file 2541 (12).qxd bangladesh j. sci. ind. res. 41(1-2), 83-88, 2006 introduction cassia alata is an indigenous flowering plant which grows almost in all the districts of bangladesh but it grows abundantly in the districts of dhaka, rajshahi and dinajpur. cassia alata is found to grow in the lower bengal, western peninsula, burma and malacca, very probably introduced into india, as it does not appear to occur far away from human dwellings. at present it is predominantly found in indo-pakbangladesh subcontinent.1 the cassia alata is of considerable importance from a medicinal point of view.2 the fresh leaves were often employed to cure ring worm.2 cassia alata is used in west africa to treat parasitic skin diseases and pustular skin infections.3 in the search for therapeutic agents from natural sources for the treatment of aids patients the antibacterial and antifungal activities of water extracts of cassia alata were investigated.4 cassia alata has wide range of medicinal uses in india and the west indies for the treatment of various aliments.5 cassia alata plants produce considerable amounts of seeds which are generally left as waste. the physico-chemical properties of oils are believed to be directly related to their glyceride and lipid. so, a first hand knowledge of its chemical composition seems to be very much essential for its potential use as a medicinal plant. studies on the lipid and glyceride compositions of cassia alata seed oil m. s. rahman,a m. y. ali,b m. u. alib and ajm moynul hasana abcsir laboratries, binodpur bazar, rajshahi-6206 and bdepartment of chemistry, university of rajshahi, rajshahi, bangladesh abstract the oil composition of cassia alata seed collected from three different districts of bangladesh was investigated. all the seed samples contain about 3.2 % oil. the triglyceride component of the oil varied from 91.5 to 92.0 % diglyceride from 3.4 to 3.9 % and monoglyceride from 1.5 to 2.1 %. the lipid components were almost the same in all the samples, the neutral lipid accounted for over 93 % of the total lipids present. the analysis of the fatty acid composition showed 25.6 % oleic acid, 45.5 % linoleic acid, 18.7 % palmitic acid, 3.5 % stearic acid, 3.4 % arachidic acid and 3.2 % behenic acid. 84 studies on the lipid and glyceride compositions 41(1-2) 2006 despite considerable works were done on the isolation of various compounds from leaves by some workers,2,6 information on the characteristics of the cassia alata seed oil is lacking. hence the present investigation was made with a view to finding out the approximate compositions of glyceride and lipid of the oil of the locally available seeds, as the location of bangladesh is typical in the subcontinent because of seasonal variations of monsoon. materials and methods ripe and matured cassia alata seeds were colleted from the districts of dhaka, rajshahi and dinajpur in the month of august. the seeds were deshelled and decorticeted manually and dried in the sunlight for four consecutive days. the sun dried seeds were finally crushed into powder with the help of a grinding machine and dried in the oven at a temperature with the help of a grinding machine and dried in a soxhlet extractor with n-hexane for an 8 hour. the solvent was removed by using a rotary vacuum evaporator and the percentage of oil content was calculated. the crude oil thus obtained was purified in a column (neutral alumina in pet. ether) using pet. ether (70:30) as the eluting solvent. the purity of the oil was checked by normal tlc. the specific gravity of the oil was calculated at 28o c with the help of a pycnometer. refractive index of clear oil free from water and air bubbles were determined at 28o c by standard iupac method.7 moisture and volatile matter in the oil were also determined by iupac method.7 the free fatty acid (ffa), saponification value, peroxide value and unsaponifiable matters in the oil were determined by the standard aocs methods.8 hanus method9 was followed to determine the iodine value of the oil. separation of glyceride each sample of oil of the seeds collected from the above three districts was separated into mono-, diand triglycerides on silicic acid (e. merck, darmstadt, germany 70-230 mesh) column. the silicic acid was activated at 120o c overnight and again for 1 hour immediately before the column was prepared. then the silicic acid was hydrated with 5 % (w/w) water. a slurry of silicic acid in chloroform was poured into the column (2.2 cm i.d). one g oil was dissolved in 15 ml of chloroform and quantitatively transferred to the column. the triglyceride components from each of the three samples (0.917, 0.920 and 0.915 g) was eluted with 200 ml of benzene, the diglyceride (0.039, 0.034 and 0.036g) with 200 ml of a 1:9 (v/v) mixture of diethy1 ether and benzene and the monoglyceride (0.021, 0.018 and 0.015g) with 200ml dieth1 ether.10 the percent compositions of the glyceride are shown in table ii. the elution was controlled at a flow rate of 1.52ml/min. the elution of each fraction was monitored by micro slide thin layer chromatography (tlc) to ensure complete separation of each class of the glycerides during slilicic acid chromatography and the eluted solvents were collected in weighed flasks. the fractions thus obtained were evaporated in a rotary vacuum evaporated in a rotary vacuum evaporator and were dried under reduced pressure before being weighed. the purity of the different glyceride components was further checked by tlc using silica gel developed with n-hexene : diethy1 ether checked by tlc using silica gel developed with n-hexene: diethy1 ether (80/20 v/v) and identified by chromic-sulphuric acid spot tests at 180o c. the glyceride were identified by comparison of rf values with standard references. the weight percentage of each glyceride class was based on total glyceride recovered, which averaged to 99.3 of the total glyceride present. fractionation of cassia alata seed lipid total lipid extracted by bligh and dyer method11 was fractionated into three major lipid groups, neutral lipid, glycolipid and phospholipid by silicic acid chromatography on about 150mg of cassia alata seed lipids neutral lipids were eluted with chloroform, glycolipid with acetone and phospholipid. with methanol.12 the elution was controlled at a flow rate of 0.5ml-1.0ml/min. the complete elution of each fraction was monitored by micro slide tlc during silicic acid column chromatography and eluted solvents were collected in weighed vials. the percentages of these fractions were determined by gravimetric method. separation of saturated and unsaturated fatty acid present in the seed oil separation of saturated and unsaturated fatty acids was carried out by lead-salt-ether method.14 50gm of the oil was saponified with alcoholic caustic soda to obtain soap solution. a slight excess of lead acetate solution was added to the soap solution to form lead salt of fatty acid which were then separated. ether was added to the mixture of lead salt and the whole mixture was added to the soap solution to form lead salt of fatty acid which were then separated. ether was added to the mixture of lead salts and the whole mixture was boiled and then cooled at oo c for 24 hours. the upper ether layer was decanted off. the lead of the unsturated fatty acid were obtained by removing the ether from the upper ethereal solution. the precipitated part contained lead salts of the saturated fatty acids. each group of lead salts was suspended in water and treated with sufficient hydrochloric acid and extracted with ether. on evaporating the ether, the fatty acid were obtained mainly in two groups. finally masses of saturated and unsaturated fatty acids were obtained by weighing them separately. fatty acid composition of cassia alata seed oil fatty acid composition of cassia alata seed oil was analysed as their methy1 ester, which was prepared by the boron trifluoride rahman, ali, ali and hasan 85 methanol method.14 a gcd pye unicam gas chromatograph equipped with a flame ionization detector was used to determine the fatty acid methy1 esters. nitrogen carrier gas was used at a flow rate of 30ml/min. fatty acid were separated on a 18x 1/8 i. d glass column packed with 6 % bds (butanediol succinate polyesters) on solid support anakorm abs (100/120) mesh. analysis was carried out at isothermal column temperature 190o c, injector and detertor temperatures for all glc analyses were 230o c. gas chromatographic peaks were identified by comparison with standard methy1 ester with respect to retertion times against equivalent carbon length (ecl). peak areas were measured by a pye unicam electronic integrator. the percentage of each peak was calculated as the percentage of total area of all the peaks. results and discussion the solvent extraction of cassia alata seed yielded 3.2 % light yellow coloured oil. purification of the oil was carried out by column chromatography and the purity was verified by normal tlc. the physico-chemical characteristics of purified oil were determined by the conventional methods and results were given in table i. no. appreciable change in physical and change in physical and chemical characteristics among the three samples collected from three different districts was observed. specific gravity and refractive index were normal in comparison with other vegetable oils.13 the whole oil was fractionated into mono-, diand triglycerides by means of column chromatography and the results were presented in table ii. from the results in table ii, it is evident that triglycerides in all the three samples irrespective from where they were collected accounted for over 91.5 % of the total weight of the oil. total extracted cassin alata seed lipid were separated into neutral lipid, glycolipid and 86 studies on the lipid and glyceride compositions 41(1-2) 2006 table i. physical and chemical characteristics of cassia alata seed oil mean results of three experiments for each sample physical and chemical characteristics 1. specific gravity at 28 o c 2. refractive index at 28 o c 3. moisture and volatile matter (%) 4. melting point 5. free fatty acid as oleic (%) 6. iodine value (hanus method) 7. saponification value 8. unsaponifiable matter (%) 9 peroxide value (m.e.v/mg) name of the districts from where seeds were collected rajshahi dinajpur dhaka 0.9215 0.9226 0.9248 1.4590 1.4628 1.4625 0.1171 0.1173 0.1170 28-29o c 28-29o c 29-30o c 2.1 2.5 2.7 94.3 94.5 95.0 189.0 188.4 188.7 1.5 1.8 2.0 1.80 1.82 1.85 phosphopid by slilicic acid column and presented in table iii. the results indicate that no significant change in the lipid composition among the three samples was noticed. from the results shown in table iii, it is observed that neutral lipids in all the three samples were in table iii, it is observed that neutral lipid in all the three samples were found to be over 93 % of the total weights of the lipid. the saturated and unsaturated fatty acid present in the oil were separated by lead saltether method and the results were depicted in table iv. from the results in table iv, it is seen that the percentage of saturated and unsaturated fatty acid present in the oil collected from rajshahi and dinajpur districts were almost similar. but the percentage of fatty acid composition of the oil in the sample collected from dhaka district differs from fatty acid composition of the samples from other two districts. the fatty acid composition of the oil was determined by glc and the results were presented in table v. gas chromatographic analysis showed that unsaturated fatty acid present in cassia alata seed oil were mainly oleic (25.6 %) and linoleic (45.5 %) which altogether accounted for over 70 % of the total fatty acid. rahman, ali, ali and hasan 87 table ii. glyceride composition of cassia alata seed oil (weight %) mean results of three experiments results for each sample name of the districts from where seeds were collected rajshahi dinajpue dhaka monoglyceride 2.1 1.8 1.5 diglyceride 3.9 3.4 3.6 triglyceride 91.7 92.0 91.5 ffa 2.1 2.5 2.7 table iii. lipid composition of cassia alata seed oil (weight %) mean results of three experiments results for each sample name of the districts from where seeds were collected rajshahi dinajpur dhaka neutral lipid (%) 93.2 94.3 92.8 glycolipid (%) 4.6 3.3 4.6 phospholipid (%) 2.6 2.1 2.3 table iv. percentage of saturated and unsaturated fatty acid name of the districts from where seeds were collected rajshahi dinajpur dhaka saturated fatty acid 25.5 23.7 29.0 unsaturated fatty acid 70.7 72.5 67.2 conclusion the cassia alata seed has been found to contain about 3.2 % oil. the oil is mainly composed of unsaturated fatty acid (over 70 % of which 25 % accounts for oleic acid and 45.5 % linoleic acid. acknowledgement the authors express their gratitude to professor m. mosihuzzaman and professor nilufar nahar of dhaka university for the fatty acid analysis by glc. references 1. the wealth of india, a dictionary of indian raw materials and industrial products, vol. iii. c.s.i.r. delhi, india, (1992) 332. 2. r. n. chopra, s. l. nayar and i. c. chopra: glossary of indian medicinal plants, council of scientific and industrial research, new delhi, india, (1980). 3. e. o. ogunti, a. j. aladesomani, s. a. adesonya. fitoterapia 62(6)(1991) 537-539, 4. c. o. crockett, f. g. guina, d. pugh, m. v. manda, t. j. robinson. j. o. olubadewo. r. f. ochillo. cellular and molecular-biologyoxford, 38(5) (1992) 505-511. 5. s. palanichamy, s. nagarajan. journal of ethnopharmcology, 29(3) (1990) 337-340. 6. h. moriama, t. iizaka, m. nagai and y. murata. fitoterapia, 74(5) (2003) 405.11. 7. international union of pure and applied chemistry: standard methods for the analysis of oils, fats and derivatives, pargamon press, 6th, ed. 8. official and tentative methods of the american oil chemicsts society (1 & 11), 3rd ed. (1980). 9. association of official agricultural chemists: official methods of analysis 8th ed. washington, (1955). 10. m. a. gafur, m. s. rahman, g. m. ahmed, a. hossain and m.e. haque. bangladesh j. sei ind. res. xxviii 3 (1993) 25. 11. j. jayarama. laboratory manual in biochemistry, wilely eastern ltd. (1985) 96. 12. m. a. gafur, m. s. rahman, g. m. ahmed, a. hossain and m. e. haque. bangladesh j. sci. ind. res. xxviii 3, 10. 13. t. p. hilditch. the industrial chemistry of the fats and waxes, 3rd ed. bailliers tindall and cox london, (1949) 80. 14. w. r. morrison and l. m. smith. j. lipid. res. 5 (1964) 600. 88 studies on the lipid and glyceride compositions 41(1-2) 2006 table v. the fatty acid composition of cassia alata seed oil of rajshahi variety (weight %) fatty acid c16:0 (palmilic acid) c18:0 (stearic acid) c18:1 (oleic acid) c18:2 (linoleic acid) c20:0 (arachidic acid) c22:0 (behenic acid) weight percent 18.7 3.5 25.6 45.5 3.4 3.2 403 forbidden forbidden you don't have permission to access this resource. apache/2.4.54 (ubuntu) server at www.banglajol.info port 443 403 forbidden forbidden you don't have permission to access this resource. apache/2.4.54 (ubuntu) server at www.banglajol.info port 443 403 forbidden forbidden you don't have permission to access this resource. apache/2.4.54 (ubuntu) server at www.banglajol.info port 443 fille 2693(14).qxd microbial contamination of water in around dhaka city sahana parveen*, m. shakir uddin ahmed and tania nasreen food microbiology section, institute of food science and technology, bangladesh council of scientific and industrial research, dhaka, bangladesh. abstract a total of 109 water samples were collected from around dhaka city and examined for microbial contamination. samples were collected in sterilized screw capped glass bottles, transported to the laboratory in cold and processed within 6 hours of their collection. all river water, pond water and household water were found heavily contaminated with coliform, faecal coliform, e. coli and salmonella whereas tube well water and bottled water was devoid of faecal coliform, e. coli and salmonella. a significant correlation between total number of total coliform and percentage of salmonella was also investigated. it is suggested that water must be boiled before use. key words: water contamination, total coliform, faecal coliform, salmonella bangladesh j. sci. ind. res. 43(2), 273-276, 2008 short comuunication introduction safe drinking water and adequate environmental sanitation are preconditions for health and for success in the fight against poverty, hunger and child deaths. worldwide in 1995, contaminated water and food caused more than 3 million deaths, of which more than 80% were among children under age five (who 1996). globally, the world health organization (who) estimates that 1.8 million people die each year from diarrhoeal diseases. faechem (1980) reported that at least one and a half thousand million people worldwide used polluted water. this problem is more acute in developing countries where higher incidence of water-borne diseases are reported. in india, more than 70% of the epidemic emergencies are either water borne or are water related (khera, et al 1996). among waterborne diseases of bacterial origin typhoid, bacillary dysentery and diarrhoea are common in bangladesh. although a substantial amount of work has been carried out on common water borne pathogens in bangladesh, unfortunately a little information is available. for this a study was conducted to estimate the quality of var* corresponding author bcsir avaiable online at www.babglajol.info bangladesh journal of scientific and industrial research e-mail: bjsir07gmail.com 274 microbial contamination of water 43(2) 2008 ious sources of water and the prevalence of waterborne pathogens. materials and methods sample collection a total of 109 water samples were collected from the entire region of the city of dhaka. samples of river water (18), pond water (18), household water (45), tubewell water (19), bottled water (9) were collected. samples were collected in sterilized screw capped glass bottles, transported to the laboratory in cold and processed within 6 hours of their collection. methodology all of the water samples were analyzed by standard methodologies recommended by the american public health association (apha 1995). to assess the microbial load, indicator parameters, viz. heterotrophic plate count (hpc), total fungus count (tfc), total coliform count (tcc), faecal coliform count (fcc), salmonella and e. coli were studied. hpc was enumerated on plate count agar (pca) by standard plate count, tfc were on potato dextrose agar (pda) by spread plate technique; tcc, fcc and e. coli were determined by the most probable number (mpn) method. isolation of salmonella was carried out on enrichment method. for salmonella, 100 ml of water sample was enriched 24 hours at 37oc in 100ml of double strength lactose broth, then 1 loopful of 24 hours culture was transferred to 10 ml selenite broth and incubated 24 hours at 37oc in an incubator. one loopfull overnight culture from selenite broth was streaked on bismuth sulphite agar (bsa) and incubated 24 hours at 37oc. from each sample three typical colonies were biochemically confirmed. results and discussion table i summerized the water samples with source , type and microbial parameters. in river water 18 1.12x105 4.93x102 2.4x104 2.4x104 3.49x102 100 pond water 18 4.43x105 3.02x103 2.4x104 2.4x104 2.12x102 100 household water 45 2.30x105 9.3x101 1.70x102 1.70x102 1.40x102 84.37 tubewell water 19 1.8x102 0.1x101 1.0x101 n.f n.f n.f mineral water 09 3.50x102 1.93x103 n.f n.f n.f n.f table i. microbial contamination of different type of water in dhaka. n= number, hpc = heterotrophic plate count, tfc= total fungus count, tcc= total coliform count, fcc=faecal coliform count, water samples counts (geometric mean) n tfc(counts/ ml) hpc(counts /ml) tcc(counts /100ml) fcc(counts /100ml) e.coli(cou nts/100ml) salmonella (%) parveen, ahmed and nasreen 275 comparison to tubewell water and bottled water, river water, pond water and household water showed more pathogenic contamination. all river water, pond water and household water were heavily contaminated with coliform, faecal coliform, e. coli and salmonella whereas tubewell water and bottled water were devoid of faecal coliform, e. coli and salmonella. there was no remarkable difference in pathogenic organism among river water, pond water and household water. geldreich (1994) reported that the rate of salmonella isolation is related to faecal coliforms. our findings was also similar with that result. from this study we had found that there was a correlation between total coliform and the presence of salmonella species. among the different sources of water the correlation was significant in case of river water, pond water and household water (fig. 1). the presence of coliform, faecal coliform, e. coli and salmonella in a majority of these samples showed that contamination was widespread. however, except for some samples, most drinking water samples were found to be devoid of any pathogenic organism. it is contended that contamination is mainly due to disposal of waste in river and pond, unhygienic conditions related to washing in utensils and bathing. household water may be contaminated with connecting the supplied pipe line with sewerage system. the dhaka city is also over crowded which seem to the cause of contamination. 0 20 40 60 80 100 1 2 3 4 % of salmonella number of tcc (log base 2) 1. river water 2. pond water 3. household water 4. tube well water fig. 1: relationship between tcc and % of salmonella. salmonella 276 microbial contamination of water 43(2) 2008 conclusion the data presented here may serve as a baseline to which all future data may be compared. studies in this respect are also warranted to safeguard ourselves against waterborne pathogens and suggested to boil the water before use. acknowledgement financial support from institute of food science and technology, bangladesh council of scientific and industrial research, dhaka is gratefully acknowledged. references american public health association (apha) (1995) standard methods for examination of water and wastewater. 19th edition. american public health association, washington, d.c.usa. faechem, r.g. (1980) bacterial standards for drinking water quality in developing countries. lancet. 2:255-56. geldreich, e.e. (1998) the bacteriology of water. in: colier, l., balows, a.and sussman, m. (eds.), microbiology and microbial infections. 9th ed. arnold publication, london. khera, a.k. jain, d.c. dutta, k.k. (1996) microbial contamination of various water sources in delhi. j. commun. dis. 28:12938. who (1996) the world health report. fighting diseases, fostering development. geneva. available at: http://www.who.int/whr/ 1996/en/. who (1997) guidelines for drinking water quality. vol 3: surveillance and control of community supplies. the world health organisation, geneva. available at: http://www.who.int/water_sanitation_healt h/dwq/gdwq3rev/en/. received : august 29, 2007; accepted : january 17, 2008 file 2527 (17).qxd bangladesh j. sci. ind. res. 41(1-2), 109-112, 2006 short communication introduction onion (allium cepa l.) is the main spice crop grown in bangladesh. it is used in almost all food preparation and is an integral part of bangladesh diet.1 onion is grown in 35,000 hactre land and its total production is 1.40 lac ton.2 it is grown more or less in all the districts of bangladesh but the average yield is 4.17 t/ha2 which is very low as compared to other developed countries like usa (42 t/ha), japan (44.7 t/ha) and south korea (53 t/ha) as reported by pathak.3 the average world production at present is about 15 t/ha.3 among various factors affecting its production, the role of irrigation assumes greater significance. onion needs frequent irrigation but it does not tolerate water logging condition. recently the climatological approach has come out to be the most reliable device for scheduling irrigation. the present study was therefore, undertaken to find out optimum irrigation schedule and water requirement of onion. materials and methods the field experiment was conducted at grey terrace soil of gazipur (aez-28) during rabi seasons of 1990-2000 and 2000-2001. five regimes of irrigation (control, 0.50, 0.75, 1.00 and 1.25 iw/cpe ratio with 4 cm depth of irrigation water at each irrigation) were tried in randomized complete block design (rcbd) with four replications. one common irrigation of 4 cm depth was given just after transplanting and the subsequent irrigations were timed on the basis of different iw/cpe ratios. the total number of irrigations including a common irrigation, irrigation schedules of control, 0.50, 0.75, 1.00 and 1.25 iw/cpe ratio were 1, 3, 4, 5 and 6, in both years respectively. five week old seedling of line on-0193 were transplanted on 6th and 1st december, 1999 and 2000, respectively and the crop was harvested on 20th and 12th march, 2000 and 2001, respectively. unit plot size was 2m x 1m. the spacing was 20 cm between rows and 10 cm between plants. uniform dose of 120 kg n/ha as urea, 90 kg p2o2/ha as tsp, 90 kg k2o/ha as mp and 20 kg s/ha as gypsum were applied. half urea and all other fertilizer were applied as basal and rest of urea was applied at 45 dat. the water table depth was below 3m through out the experimentation. hence the contribution of ground water was considered to be effect of different soil moisture regime on the yield and yield components of onion r. sen, a. t. m. a. i. mondal, s. brahma and m. s. khan soil science division, bangladesh agricultural research institute, gazipur-1701, bangladesh negligible. the total rainfall during cropping season were 6.5 cm in 2000 and 5.8 cm in 2001, the bulk of which was received in the march in both year. there was practically no rain during active growth period of the crop in both the year. five representative plants were harvested from each plot for recording yield attributes of onion. results and discussion the yield, yield components and water use efficiency of onion as responded to different soil moisture regime are presented in table i and table ii. bulb diameter, bulb length, individual bulb weight and bulb yield/ha increasing upto 1.25 iw/cpe ratio of soil moisture regime, but data obtained from 1.00 iw/cpe ratio and 1.25 iw/cpe ratio are statistically similar. maximum bulb diameter (5.96 cm in 2000 and 6.08 cm in 2001) obtained from 1.25 iw/cpe ratio which was statistically similar with 1.00 iw/cpe ratio and comparatively higher from all other treatment. highest bulb length (5.64 cm in 2000 and 5.68 cm in 2001) obtained from 1.25 iw/cpe ratio which was significantly higher than all other treatment. maximum individual bulb weight (67.55 g in 2000 and 69.86 g in 2001) was obtained from 1.25 iw/cpe ratio which was identical with bulb weight derived from 1.00 iw/cpe ratio (58.14 g in 2000 and 60.77 g in 2001). both of above two bulb weight were significantly higher than bulb weight of rest three treatments. bulb yield/ha increasing significantly with the increase of soil moisture regime upto 1.00 iw/cpe ratio. bulb yield /ha was highest in 1.25 iw/cpe ratio (16.32 t/ha in 2000 and 16.59 t/ha in 2001) which was identical with 1.00 iw/cpe ratio (15.08 t/ha in 2000 and 15.36 t/ha in 2001). percent increase in bulb yield due to 1.25, 1.00, 0.75, 0.50 iw/cpe 110 effect of different soil moisture 41(1-2) 2006 table i. effect of different soil moisture regimes on the yield, yield components and water use efficiency of onion during rabi season of 1999-2000 soil moisture regimes (iw/ cpe ratio) control 0.50 0.75 1.00 1.25 lsd cv(%) no. of irrigation 1 2 3 4 5 bulb diameter (cm) 1.81d 2.47c 4.56b 5.48a 5.96a ** 6.3 bulb length (cm) 2.13e 3.33d 4.45c 5.21b 5.64a ** 4.8 bulb weight (g) 12.52d 29.49c 44.32b 58.14a 67.55a ** 14.4 bulb yield (t/ha) 5.48d 8.72c 12.06b 15.08a 16.32a ** 8.8 % yield increase over control 59.12 120.07 175.18 197.81 total water applied including rainfall (cm) 10.50 18.50 22.50 26.50 30.50 water use efficiency (kg/ha/cm) 521.90 471.35 536.00 569.06 535.06 ratio over control were 197.81, 175.18, 120.07 and 59.12 in 2000 and 192.59 170.90, 116.58 and 56.79 in 2001, respectively. liberal water supply (1.25 or 1.00 iw/cpe ratio) increased bulb diameter, bulb length and individual bulb weight which resulted increased bulb yield of onion, confirming the results of singh and sharma4; hegde5 and palled et al.6 total water use for onion varied from 10.50 to 30.50 cm in 2000 and 9.80 to 29.80 cm in 2001. highest water use efficiency (569.06 kg/ha/cm in 2000 and 595.35 kg/ha cm in 2001) was obtained from soil moisture regimes of 1.25 iw/cpe ratio which received 6 irrigations giving bulb yield of 15.08 t/ha in 2000 and 15.36 t/ha in 2001. conclusion soil moisture regime 1.00 iw/cpe ratio (5 irrigations 1, 20, 35, 55 and 70 days after transplanting) was found optimum for onion production in grey terrace soil of gazipur. references 1. a. k. m. hossain and j. islam. status of allium cepa production in bangladesh. hort. abst. 358 (1994) 33-36. 2. b. b. s. the year book of agricultural statistics of bangladesh. statistics division, ministry of plannning. goverment of the peoples republic of bangladesh (1997). 3. c. s. pathak. allium improvement for the tropics: problem and avrdc strategy. hort. abst. 358 (1994) 23-93. 4. d. singh and r. p. sharma. effect of soil moisture regimes and nitrogen fertilization on onion. indian j. of agronomy. 36(1) (1991) 125-126. sen, mondal, brahma and khan 111 table ii. effect of different soil moisture regimes on the yield, yield components and water use efficiency of onion during rabi season of 2000-2001 soil moisture regimes (iw/ cpe ratio) control 0.50 0.75 1.00 1.25 lsd cv(%) no. of irrigation 1 2 3 4 5 bulb diameter (cm) 1.87d 2.51c 4.65b 5.59a 6.08a ** 7.0 bulb length (cm) 2.16e 3.39d 4.53c 5.28b 5.68a ** 6.2 bulb weight (g) 13.14d 30.55c 46.41b 60.77a 69.86a ** 9.7 bulb yield (t/ha) 5.67d 8.89c 12.28b 15.36a 16.59a ** 7.9 % yield increase over control 59.79 116.58 170.90 192.59 total water applied including rainfall (cm) 9.80 17.80 21.80 25.80 29.80 water use efficiency (kg/ha/cm) 578.57 499.44 563.30 595.35 556.71 5. d. m. hegde. effect of irrigation and n fertilization on water relations, canopy temperature, yield. n uptake and water use of onion. indian j. agric. sci. 56(12) (1986) 858-867. 6. y. b. palled, m. d. kachpur, a. m. chandrasekharan and a. s. prabhakar. response of onion to irrigation and nitrogen. indian j. agron. 33(1) (1988) 22-25. 112 effect of different soil moisture 41(1-2) 2006 file 2594 (11).qxd bangladesh j. sci. ind. res. 42(1), 79-82, 2007 introduction the two main types of commercial spearmint oil are obtained from the leaves of the perennial herbs mentha spicata l. (native spearmint) and mentha cardiaca l. (scotch spearmint). the spearmint plant reaches a meter in height at maturity. spearmint is indigenous to england and is grown all over the world mainly in the usa with some recent development in china and south america (lee and fred, 1998). it is available in many southeast asian countries (atal and kapur 1982). the world market for spearmint oil is approximately 1500 tons/ year (lee and fred, 1998). the major end uses are in toothpaste and mouthwash, chewing gum and candy and food flavouring (lee and fred, 1998; atal and kapur, 1982 and guenther, 1949). in southeast asian countries m. spicata is commonly used as culinary purposes and digestive (anonymous, 1962). the herb is considered to be carminative, stomachic and antispasmodic; given in hiccup, flatulence, colicky pains, cholera etc (reynolds, 1982; yusuf, et. al. 1994 and chopra, et. al. 1950). m. spicata is characterized by a high carvone content account for 60 70 % of the total oil accompanied by a limonene content of 8 15 % (lee and fred, 1998). the carvone content of m. cardiaca is also 60 70 %, but typically it has a higher limonene content of up to 20 % (lee and fred, 1998). the latter oil also has a menthone content of up to 2 %, which is the prime indicator of scotch spearmint (lee and fred, 1998). these two plants were introduced as a part of our flora enrichment pogramme of important exotic medicinal and aromatic plants and to study the aromatic properties of the oils. chemical constituents of essential oils from two types of spearmint (mentha spicata l. and m. cardiaca l.) introduced in bangladesh jasim uddin chowdhury,a nemai chandra nandi,a minhaj uddina and majibur rahmanb abcsir laboratories, chittagong-4220, bangladesh bigcrd, bcsir, dhaka-1205, bangladesh. abstract mentha spicata and m. cardiaca introduced in bangladesh were studied for their essential oil content and compositions of the oil. the essential oil from m. spicata contains carvone (73.29 %), d-limonene (7.59 %) and dihydrocarvone (3.83 %) as major constituents out of the 21 components. the essential oil from m. cardiaca contains carvone (60.9 %) and limonene (21.58 %) as major constituents out of the 35 components. materials and methods both m. cardiaca and m. spicata were collected from the experimental field of bcsir laboratories, chittagong. the species were introduced from india. oil content of these species was studied at the age of six months. isolation of the oil the oil was isolated from the fresh herbs by hydrodistillation for 4 hrs. using a clevenger type apparatus (clevenger, 1982). the oil was dried over anhydrous sodium sulphate prior to analysis. the percentage of the essential oil was calculated on volume by fresh weight basis. gc/ms analysis the analysis of the oils were carried out by gc/ms electron impact ionization (ei) method on gc-17a gas chromatograph (shimadzu) coupled to a gc/ms qp 5050a mass spectrometer (shimadzu); fused silica capillary column (30m x 2.5mm, 0.25 mm film thickness), coated with db-5 (j&w), column temperature 100o c (2 min) to 250o c at the rate of 5o c/min; carrier gas, helium at constant pressure of 90 kpa. acquisition parameters full scan; scan range 40-350 amu. the compounds were identified using the nist 127 and nist 147 library data. results and discussion the oil content of m. spicata and m. cardiaca was found to be 0.33 % & 0.41 % respectively. table i shows the chemical constituents of the essential oils from mentha spicata and m. cardiaca. the oil of m spicata contains 21 compounds of which carvone (73.29 %) was the major component followed by d-limonene (7.59 %), dihydrocarvone (3.83 %), a-bourbonene (1.67 %), trans-sabinenehydrate (1.57 %), 2-naphthol,1,2,3,4,4a,5,6,7-octahydro-4amethyl (1.47 %), trans-carveol (1.25 %), dihydrocarveol (1.12 %) and eucalyptol (1.01 %). the oil of m. cardiaca contains 35 components of which carvone (60.9 %) was the major component followed by limonene (21.58 %), eucalyptol (2.22 %), cis-carveol (1.43 %), menthone (1.38 %) and β-myrcene (1.11 %). presence of 11 components (dlimonene, α-bourbonene, trans-carveol, carveyl acetate, carvone, dihydrocarveol, dihydrocarvone, eucalyptol, piperitone, 13tetradecal, 1-yl-1-ol, jasmone) were common in both of the species. findings revealed that the constituents are resembled that of the earlier reports.1,3,4,7 these introduced plants can be cultivated commercially for their higher oil content and as sources of higher carvone content. 80 chemical constituents of essential oils 42(1) 2007 fig. 1. carvone fig. 2. d-limonene sl. no. name of compounds molecular molecular % content weight formula m. spicata m. cardiaca 1 benzene, tert-butyl 134 c10h14 0.15 -2 α-bourbonene 204 c15h24 1.67 0.95 3 camphene 136 c10h16 -0.40 4 cis-carveol 152 c10h16o -1.43 5 trans-carveol 152 c10h16o 1.25 0.62 6 carveyl acetate 194 c12h18o2 0.58 0.19 7 carvone 150 c10h14o 73.29 60.90 8 caryophyllene oxide 220 c15h24o 0.76 -9 caryophyllene 204 c15h24 -0.74 10 dihydrocarveol 154 c10h18o 1.12 0.13 11 α-cubebene 204 c15h24 -0.14 12 dihydrocarvone 152 c10h16o 3.83 0.95 13 diisobutyl carbinol 144 c9h20o 0.93 -14 cyclooctanol 128 c8h16o -0.11 15 eucalyptol 154 c10h18o 1.01 2.22 16 4-hydroxy-3,5,5154 c9h14o2 0.75 -trimethylcyclohex-2-enoen 17 (+)-isomenthol 156 c10h20o 0.37 -18 β-farnesene 204 c15h24 -0.26 19 jasmone 164 c11h16o 0.59 0.51 20 furan, 2,5-diethyltetrahydro 128 c8h16o -0.09 21 ledol 222 c15h26o 0.73 -22 d-limonene 136 c10h16 7.59 21.58 23 germacrene d 204 c15h24 -0.55 24 cis-3-hexenol 100 c10h12o -0.07 25 trans-p-mentha-2,8-dienol 152 c10h16o 0.23 -26 2-naphthol,1,2,3,4,4a,5,6,7166 c11h18o 1.47 -octahydro-4a-methyl 27 cis-3-hexenyl isovalerate 184 c11h20o2 -0.15 28 isomenthone 154 c10h18o -0.17 29 piperitone 154 c14h18o 0.44 0.45 31 trans-sabinenehydrate 154 c10h18o 1.57 -table i. chemical constituents of essential oils from m. spicata and m. cardiaca chowdhury, nandi, uddin and rahman 81 references anonymous. (1962) the wealth of india: raw materials. csir, new delhi, india. vi, p. 344-346. atal, c. k. and kapur, b. m. (1982) cultivation and utilization of aromatic plants. csir, jammu-tawi, india. p. 763. chopra, r.n. nayar, s. l. and chopra, i. c. (1950) glossary of indian medicinal plants, csir, new delhi, india. p. 165-166. clevenger, f. (1982) j. american pharm. assoc., 17: 346. guenther. e. (1949) the essential oils. r. e. k publishing co., huntington, new york. iii, p. 676-683. lee, p. and fred, b. (1998) spearmint: in a handbook for farmers and investors. rural industries research & development corporation, australian government. reynolds, e. e. (ed). (1982) martindale: the extra pharmacopoeia, 28th edition. the pharmaceutical press, london. p. 683. yusuf, m. chowdhury, j.u. wahab, m.a. and begum, j. (1994) medicinal plants of bangladesh. bangladesh council of scientific and industrial research. chittagong-4220, bangladesh. p. 164. received : may 14, 2006; accepted : february 22, 2007 82 chemical constituents of essential oils 42(1) 2007 sl. no. name of compounds molecular molecular % content weight formula m. spicata m. cardiaca 32 4-terpineol 154 c10h18o 0.27 -34 limonene oxide, trans 152 c10h16o -0.10 35 β-linalool 154 c10h18o -0.04 36 menthone 154 c10h18o -1.38 37 β-myrcene 136 c10h16 -1.11 38 octyl cyclobutane carboxylate 212 c13h24o2 -0.12 39 β-pinene 136 c10h16 -1.04 40 α-pinene 136 c10h16 -0.80 41 l-pinocarveol 152 c10h16o -0.15 42 sabinene 136 c10h16 -0.79 43 β-terpineol 154 c10h18o -0.19 44 l-4-terpineol 154 c10h18o -0.13 45 13-tetradeca-11-yn-1-ol 208 c14h24o 0.74 0.44 46 6-undecanol 172 c11h24o -0.80 47 cis-verbenol 152 c10h16o -0.14 table i to be cont. file 2517 (14).qxd bangladesh j. sci. ind. res. 41(1-2), 93-96, 2006 introduction cassia linn. includes a large tropical genus of 580 species of herbs, shrubs and trees of the leguminosae family, including cassia alata and many of them are found in indopak-bangladesh subcontinent.1,2 cassia alata linn. is a small tree generally grown in the gardens and not far away from human dwellings.3 its use as medicine, especially in the eradication of herpescircinatus is confirmed by mekenna et al.4 earlier investigations on cassia alata reported the presence of only hydroxymethylanthraquinones (unidentified) and chrysophanic acid as isolated compounds.5 hauptmann and co-workers6 isolated rhein (an antibiotic) and its reduced form with other anthraquinone derivatives which they could not identify. though some anthraquinones were isolated and characterized by some scientists,7,8,9 none reported on the isolation of flavonoids. the present work had, therefore, been taken up to make a complete chemical investigation on the plant cassia alata. a flavone was isolated from the plant as a new source. the structure of the flavone was elucidated by spectroscopic techniques. materials and methods a reichart micro melting point apparatus was used for recording the melting point. uv spectra (meoh) was recorded on a shimadzu uv-240 spectrophotometer, ir spectra (kbr) on a shimadzu ir-460 instrument, 1hnmr spectra(cd3od) on a bruker am-500 ft nmr spectrometer (500 mhz) using tms as internal standard, 13c-nmr spectra a flavone from the leaves of cassia alata m. s. rahaman,a ajm moynul hasan,a m. y. alib and m. u. alib abcsir laboratories, binodpur bazar, rajshahi-6206 and bdepartment of chemistry, rajshahi university, bangladesh abstract studies were carried out on the leaves of cassia alata. a flavone 3,5,7,4�-tetrahydroxy flavone was isolated as a new source from the leaves of cassia alata with the help of column and thin layer chromatography using a gradient of organic solvents with increasing polarity. the compound was characterized on the basis of uv, ir, 1hnmr, 13c-nmr and mass spectrometry. (cd3od) on a bruker am-500 ft nmr spectrometers (100 mhz) and mass spectra on a varian-mat 112s spectrometer. electron impact (ei), peak matching experiments were performed on a mat-312a mass spectrometer. fresh leaves were collected from the plants grown in the adjoining areas of bcsir laboratories, rajshahi campus during august-september period. the leaves were washed with water to remove extraneous materials and then dried in shade. care was taken to avoid exposure to sunlight. the dried material was crushed to powder. the air-dried cassia alata leaf powder (6.6 kg) was soaked in 80 % ethanol for a week. the ethanolic extract was then filtered and the solvent was removed under reduced pressure to obtain a viscous residue (494 g). the crude residue was then defatted with n-henane. the defatted mass was dried under reduced pressure to give a residue (162g). the defatted extract was then treated with water, shaken well to resolve into water soluble and water insoluble parts. the water soluble part was extracted with ethyl acetate. the ethyl acetate soluble part was chromatographed over a silica gel (70-230 mash) column and successively eluted using n-hexane and ethyl acetate. elution of the column with n-hexane : ethyl acetate (40:60 v/v) afforded a compound designated as compound-1 along with minor impurities. purification of the compound by preparative thin layer chromatography (ptlc) the compound 1 with some impurities was applied to a ptlc card of silica gel 60gf254 (thickness 0.1mm) and eluted with n-hexane : ethyl acetate (4:1 v/v). a distinct single band (rf 0.49) was observed on the ptlc card. the band was collected and washed out with ethyl acetate to obtain a yellow solid (compound 1, 12.5mg, m.p 276-278o c, rf = 0.49). spectroscopic analysis of compound 1 uvλmax (meoh)nm : 366, 323, 266, 203, 195 irυmax (kbr)cm-1 : 3490(o h), 2900 (c h), 1670(c = o), 1570 -1480(c = c) eims m/z (rel. int%) : 286(100), 257(9), 241(1), 229(8), 193(0.85), 184(1), 143(10), 121(20), 105(3), 93(5), 69(8). peak matching m/z (formula) : 286.41360 (c15h10o6). 1h-nmr (500mhz) δδtms : (cd3od) : δ6.28 [h-6, 1h, d, j(h-6, h-8) 2.1 hz] δ6.54 [h-4, 1h, d, j(h-8, h-6) 2.1hz] δ8.09 [h-2 / , h-6 / , 2h, dd, j(h-2/, h-3/) 9.0hz, j(h-2/, h-6/) 2.1 hz] δ7.01 [h-3 / , h-5 / , 2h, dd, j(h-5/, h-6/) 9.0hz, j(h-3/, h-5/) 2.1 hz] 94 a flavone from the leaves 41(1-2) 2006 13c-nmr (cd3od, 100mhz) : 147.9, 137.0, 177.2, 160.4, 99.2, 162.4, 94.4, 158.1,104.5, 123.7, 130.6, 115.2, 165.4, 116.2, 130.6 (table i). results and discussion the ethyl acetate triturate of the ethanolic extract of cassia alata leaves aforded compound 1 after purification by preparative tlc. compound 1 was suggested to be a flavonoid as it exhibited light yellow appearance on silica gel card and deep yellow colour when sprayed with ceric sulphate reagent. the absorption at 3490 and 1670 cm-1 in the ir spectrum (kbr) of the compound were indicative of hydroxyl and carboxyl functions respectively. the ir spectrum also rahaman, hasan, ali and ali 95 table i. 13c-nmr (cd3od, 100 mhz) chemical shifts of 3,5,7,4 /-tetrahydroxy flavone. c. no. multiplicity (dept) 13c-nmr (δ) 1h-nmr (δ) 1jhh(hz) c-2 c 147.9 c-3 c 137.0 c-4 c 177.2 c-5 c 160.4 c-6 ch 99.2 6.28 d, j = 2.1 c-7 c 162.4 c-8 ch 94.4 6.54 d, j = 2.1 c-9 c 158.1 c-10 c 104.5 c-1 / c 123.7 c-2 / ch 130.6 8.09 dd, j = 9.0, 2.1 c-3 / ch 116.2 7.01 dd, j = 9.0, 2.1 c-4 / c 165.4 c-5 / ch 116.2 7.01 dd, j = 9.0, 2.1 c-6 / ch 130.6 8.09 dd, j = 9.0, 2.1 showed absorption at 2900 and 15701480cm-1 due to ch and c = c functions. the ei mass spectrum showed the molecular ion as well as base peak at m/z 286. the moleular formula was established with the help of 13c-nmr, 1h-nmr and peak matching experiments as c15h10o6 corresponding to the mass m/z 286.41360. 15 signals appeared in the broad-band spectrum of copound-1, which were resolved with the help of dept experiment into six methine and nine quaternary carbons. the 1h-nmr spectrum of compound 1 displayed a doublet at δ6.28 with coupling constant 2.1 hz for h-6 proton and another doublet resonated at δ6.54 having coupling constant 2.1 hz for h-8 proton. two protons at 2 / and 6 / positions gave a double doublet at δ8.09 having coupling constant 9.0 and 2.1 hz respectively. two protons at 3 / and 5 / positions gave another double doublet at δ7.01 having coupling constants 9.0 and 2.1 hz. from the spectral informations, it became apparent that the compound 1 belonged to the flavone series and was characterized as 3,5,7,4 / tetrahydroxy flavone. acknowledgement the authors are grateful to professor m. iqbal choudhary, h. e. j research institute of chemistry, university of karachi, pakistan for giving excellent facilities to perform all spectroscopic analysis there. references 1. the wealth of india. a dictionary of indian raw materials and industrial products, vol. ii, c.s.i.r, new delhi, india, (1950) 93. 2. r. n. chopra, r. l. badhwar and s. ghose. poisonous plants of india, vol. i, academic publishers, jaipur, india, (1984) 364. 3. g. watt : a dictionary of the economic products of india, vol. ii, new delhi, (1972) 211. 4. mekenna : madras med. jour., vol. i, 431; arthur : indian ann. of med. science, vol. iii (1956) 632. 5. r. n. chopra, s. l. nayar and i. c. chopra : glossary of indian medicinal plants. council of scientific and indian research, new delhi, india, (1980). 6. l. h. hauptmann and l. l. nazario : j. am. chem. soc., 72 (1950) 1492. 7. hemlata and suruj b. kalidhar. phitochemistry, 32 (1993) 1616-1617. 8. k. sahyender yadav and suraj b. kalidhar, planta med., 60 (1994) 601. 9. k. n. rai and s. n. prasad. j. indian chem. soc., 71 (1994) 653-654. 96 a flavone from the leaves 41(1-2) 2006 file 2496 (15).qxd bangladesh j. sci. ind. res. 41(3-4), 239-244, 2006 introduction the flour beetle tribolium castaneum herbst is one of the most destructive pests of stored food grains. it is generally found in granaries, mills, warehouses, etc. feeding on rice, wheat, flour, suji (a coarse flour of wheat), barley, etc. it is one of the major pests of stored products. the mentioned food items are significantly damaged by this pest in storage condition throughout the world. because of the great economic importance of the pest, many studies on this beetle have dealt with its control. mention may be made of the works of pinniger, strong and tyler et al.1-3 laboratory studies on the use of malathion as a grain protectant include those of floyd, lemon, hosni et al., strong et al., lindgren et al., gore, watters, o’donnell and husain.4-12 all of them used malathion on adult tribolium. malathion gained wide acceptance and approval for use as protectant for stored grain. it has properties with emphasis on its low mammalian toxicity parkin.13 very little published works were available regarding the control of t. castaneum larvae with malathion (commercial grade) in the environment of bangladesh. there is no published data on the control of tribolium castaneum by commercial grade malathion in this country. this led to the present work. synergistic effect of piperonylbutoxide on malathion is also incorporated here. materials and methods the experimental insects were collected from the laboratory cultures and placed in petridishes containing treated whole meal flour. all the cultures were kept at a room temperature 20o ± 2o c. experiments were carried out with 1st, 2nd and 3rd instar efficacy of malathion in controlling tribolium castaneum herbst (coleoptera: tenebrionidae) m. m. husain and m. r. hasan bcsir laboratories, binodpur bazar, rajshahi, bangladesh abstract effect of malathion on treated food medium was studied on adult and 1st, 2nd and 3rd instar larvae of tribolium castaneum. the ld50 for the instars was 228.22, 78.13 and 183.01 ppm, respectively. the rate of mortality increased with increasing concentrations. toxicity probably depended on the ingestion of the treated food medium. larvae. combined effect of piperonylbutoxide and malathion on adult was also incorporated. twenty larvae for each treatment were introduced in each petridish containing treated food media. each treatment consisted of 5 replicates. a similar treatment with untreated flour was also maintained. standard concentrations were prepared by adding 2 ml of malathion with 1000 ml of water to prepare 2000 ppm. the lowest concentrations were prepared by mixing water (1:1) with higher concentrations. mortality counts of the instar larvae and adults were assessed after 20 days. the percentage mortality data were subjected to statistical analysis busvine14 and the dose mortality relationship was expressed as a median lethal dose (ld50). for adults the effectiveness of the insecticides was evaluated by confining 50 test insects on wheat flour which had been treated with insecticide and determining subsequent knockdown and mortality. to determine synergistic effects of piperonylbutoxide on adult t. castaneum required quantities of malathion alone and in combination with piperonylbutoxide was individually weighed using an electronic balance and mixed with wheat flour. after thorough mixing, the treated flour (approximately 1g) was then transferred to individual glass vials containing tribolium castaneum adults and secured at the top with cotton wool. five doses of the insecticides were applied on the insects. then mortality of the beetle was recorded ld50 and co-toxicity coefficients were calculated. the intensity of synergism was determined by cotoxicity coefficient which is measured by the ratios of the ld50 values of the toxicant done to the ld50 values of the toxicant in mixtures with the synergist x 100. if the co-toxicity coefficient is above 100, then synergism occurs.15 results and discussion the results of the dose mortality tests and statistical analysis are shown in tables i and ii and in fig. 1. malathion at 50 ppm was unable to give complete kill after 20 days from treatment. the dosage of 200 ppm cause 60, 80 and 56 % mortalities with 1st, 2nd and 3rd instar larvae of tribolium castaneum respectively within 20 days. the dosage of 160 ppm gave 23, 70 and 39 % mortalities with the 1st, 2nd and 3rd instar larvae respectively. similarly, the dosage of 80 ppm gave 12, 60 and 29 % mortalities with larvae of the mentioned instars. it is observed that the mortality percentage increased with increase of dosage and duration. the present result is nearly similar to those of the previous workers (pinniger, hosni et al.)1,6 and tyler et al.3 according to tyler and binns,3 the minimum dosage required to kill t. castaneum under low temperature conditions (5o c to 1o c) is 1395 mg/m2 of malathion. according to hosni et al.,6 the ld50 for t. castaneum was 2.25 ppm. the present findings revealed that the ld50 for 1st, 2nd and 3rd instar larvae of t. castaneum was 228.224, 78.134 and 183.019 ppm 240 efficacy of malathion in controlling 41(3-4) 2006 husain and hasan 241 table i. dose mortality response of the 1st, 2nd and 3rd instar larvae of t. castaneum exposed to different concentrations of malathion. 1st 200 100 60 2.559 + 2.109x 228.224 425.014 122.552 160 100 23 80 100 12 40 100 8 20 100 2 control 100 0 2nd 200 100 80 1.131 + 2.043x 78.134 87.690 68.060 160 100 70 80 100 60 40 100 25 20 100 10 control 100 0 3rd 200 100 56 0.815 + 1.849x 183.019 225.367 148.635 160 100 39 80 100 29 40 100 11 20 100 3 control 100 0 table ii. combined effect of malathion and piperonylbutoxide on tribolium castaneum herbst. co-toxicity coefficient ld50 percentage mortality malathion combined malathion ppm combined ppm doses of insecticide of synergist (ppm) malathion + piperonylbutoxide 1:1 ratio doses of insecticide (ppm) malathion 200 400 60 74 160 320 44 54 80 160 34 41 138.25 251.74 109.84 40 80 15 21 20 40 5 9 larval instar concentration (ppm.) no of insect used corrected % kill regression equation y ld50 (ppm) 95 % confidence limit upper (ppm) lower (ppm) 242 efficacy of malathion in controlling 41(3-4) 2006 figure 1 (1st instar) 0 10 20 30 40 50 60 70 1 2 3 4 5 mortality (%) d os es ( pp m ) figure 2 (2nd instar) 0 10 20 30 40 50 60 70 80 90 1 2 3 4 5 mortality (%) d os es ( pp m ) fig. 1,2 & 3. mortality response of the 1st, 2nd and 3rd instar larvae of t. castaneum exposed to different concentrations of malathion. respectively. this difference was probably due to the difference in the emulsifiable concentrate formulations. besides, hosni et al.6 used adult for the experiments. husain12 used premium grade malathion. it is, thus, inferred that malathion may be used in controlling this pest under pest management programme. to assure best protection against the pest, the highest dose should be applied. it appeared from the results (table ii) that malathion in combination with the synergist produced synergism to the adults of t. castaneum. the results were discussed in relation to the potential use of piperonylbutoxide alone and in combination with malathion as synertgist in the control of adult tribolium population. acknowledgement the author thanks professor dr. k. a. m. s. h mondal, university of rajshahi, for supervising the experiments. m. m. husain also wishes to thank dr. m. o. faruq (exdirector), bcsir laboratories, rajshahi for his suggestions in preparing the manuscript. references 1. d. b. pinniger. the behaviour of insects in the presence of insecticides : the effect of fenitrothion nad malathion on resistant and susceptible strains of tribolium confusum h. proc. ist. int. mg. conf. stored prod. ent., (1975) 301-308. 2. r. g. strong. relative susceptibility of confused and red flour beetles to twelve husain and hasan 243 figure 3 (3rd instar) 0 10 20 30 40 50 60 1 2 3 4 5 d os es (p pm ) organophosphorus insecticides with notes on adequacy of the test method. j. econ. ent., 63(1) (1970) 258-263. 3. p. s. tyler and t. j. binns. the toxicity of seven organophosphorus insecticides and lindane to eighteen species of stored product beetles. j. stored prod. res., 13 (1977) 39-43. 4. e. h. floyd. effectiveness of malathion dust as grain protectant for farm-stored corn in louisiana. j. econ. ent., 54 (1961) 900-904. 5. r. w. lemon. laboratory evaluation of malathion, bromophos and fenitrothion for use against beetles infesting stored products. j. stored prod. res., 2 (1967) 197-210. 6. s. m. hosni, a. k. m. fahmy, el-nahat and e. z. fam. the effectiveness of five toxicants against three species of stored grain insects. bull. ent. soc. egypt, econ. ser., 3 (1969) 85-95. 7. r. g. storng and d. e sbur. influence of grain moisture and storage temperature on the effectiveness of malathion as grain protectants. j. econ. ent., 53 (1960) 341369. 8. d. l. lindgren, h. e. krohne and l. e. vincent. malathion and chlorthion for control of insects infesting stored grain. j. econ. ent., 47(4) (1954) 705-706. 9. k. s. gore. laboratory experiments with some organic phosphorus insecticides as wheat protectants. ph. d. thesis, cornel univ. (univ. microfilms, inc.) (1958). 10. f. l. watters. effects of grain moisture content on residual toxicity and repellency of malathion. j. econ. ent., 52 (1959) 131-134. 11. o’donnell. the toxicities of four insecticides to tribolium confusum duv. in two sets of conditions of temperature and humidity. j. stored prod. res., 16 (1980) 71-74. 12. m. m. husain. dose mortality response of tribolium confusum larvae to malathion, bangladesh j. sci. ind. res., 32(4) (1997) 599-601. 13. e. a. parkin. a provisional assessment of malathion for stored product insect control. j. sci. food agr., 6 (1958) 370-375. 14. j. r. busvine. a critical review of the techniques for testing insecticides. commonwealth agricultural bureaux, london (1977) 345. 15. y. p sun and f. r johnson. synergistic and antagonistic action of insecticide-synergist combinations and their mode of action. j. agric. food chem. 8 (1960) 261-266. 16. m. m. husain. synergistic effect of piperonylbutoxide on malathion to control adult tribolium confusum duval, bangladesh j. sci. ind. res., 31(4) (1996) 111-115. 244 efficacy of malathion in controlling 41(3-4) 2006 ahmed, haque, hossain, rahman, alamgir and jalal 7 8 study of thermal conductivity of hexamethylene 41(3-4) 2006 effect of plant extracts on the yield of soybean 9 10 effect of plant extracts on the yield of soybean 41(1-2) 2006 macap fill 2834(9).qxd introduction rats and mice harbor a number of helminth parasites, which can be transmitted to man and other vertebrates (oldham, 1931). helminth parasitized rats were studied to identify the species and for determination of prevalence and intensity of helminths (stanly and virgin, 1993; alam et al., 2003; khanum and arefin, 2003). cestode and nematode parasites in rat have been reported from all parts of the world. vampirolepis nana and hymenolepis diminuta are commonly found in rats and mice and potentially transmissible (zoonoses) to man. the occurrence of h. diminuta and v. nana in certain rodents is of interest since the possibility exists that rats and mice may serve as reservoir hosts and aid in the dissemination of these worms to domestic animals and man (jawdat and mahmoud, 1980); causing zoonoses. in bangladesh, several studies have been carried out on identification of the parasites of rats and mice but no histopothological investigation have been done (huq, 1969; shaha, 1974; bhuiyan et al., 1996; alam et al., 2003 and; khanum and arefin, 2003). the effects of parasites on their host can also be examined by pathological condition. inspite of several pathological works on parasitic infestation in our country no pathological investigation have so far been undertaken on histopathology of the infestation on long-evans. the present study was carried out on identification of parasite species prevalence and histopathological effect of parasites on their host and for securing additional information on the helminth parasites of laboratory rat. materials and methods during the study period from april 2007 to march 2008 a total of 48 long-evans were collected weekly and monthly basis from animal research section of the institute of food science and technology (ifst) of bangladesh council of scientific and industrial research (bcsir), dhaka. to collect the parasites tested long-evans were dissected, the viscera were collected and brought to the parasitology laboratory of the department of zoology, university of dhaka. a histopathological investigation was carried out on thin sections of tissues. then permanent slides were prepared from the tissues and permanent slides were prepared by cable, 1963. nematode and cestode prevalence, organal distribution and histological effects due to parasitic infection in laboratory rat strain, long-evans (rattus norvegicus berkenhout, 1769) hamida khanuma , farhana muznebina* and zaibun nessab adepartment of zoology, university of dhaka, dhaka-1000, bangladesh and binstitute of food science and technology, bcsir, dhaka-1205, bangladesh. abstract endoparasitic infection and histopathological effects in the laboratory rat, long-evans (rattus norvegicus berkenhout 1769) was evaluated. five species of helminth parasites from two taxonomic groups were identified. they were -cestodes (vampirolepis nana siebold, 1852 and hymenolepis diminuta rudolphi, 1819) and nematodes (citellina dispar prendel, 1928; heterakis spumosa schneider, 1866 and syphacia muris yamaguti, 1941). all the worms were collected from the alimentary tract of the long-evans. the prevalence of infection was found highest in caecum (95.83%) and the intensity of infestation was found highest in anterior parts of the intestine (51.33±10.63). the histopathological study of helminth infected alimentary canal showed that the intestinal wall was severely damaged. key words: nematodes, cestodes, prevalence, vampirolepis nana, hymenolepis diminuta, citellina dispar, heterakis spumosa and syphacia muris. bangladesh j. sci. ind. res. 44(2), 207-210, 2009 bcsir available online at www.banglajol.info bangladesh journal of scientific and industrial research e-mail: bjsir07@gmail.com *corresponding author, email: farhana_zoologydu@yahoo.com. 208 nematode and cestode prevalence, organal distribution 44(2) 2009 results and discussion the intestine of the long-evans (rattus norvegicus) was infested by cestode parasites vampirolepis nana (siebold, 1852) and hymenolepis diminuta (rudolphi, 1819) and nematodes citellina dispar (prendel, 1928); heterakis spumosa (schneider, 1866) and syphacia muris (yamaguti, 1941). a total of 1643 nematodes were collected from 46 infested hosts and 1911 cestodes from 38 infested hosts. the prevalence of cestodes and nematodes were 79.17% and 95.83% respectively. prevalence of nematodes was higher than the cestodes. intensity of cestodes and nematodes were 50.29 ±14.13 and 35.71 ±7.89 respectively. the parasites were most abundant in anterior part of intestine. no parasites were found in stomach. in duodenum 46 (43.75%) parasites were collected and 1848 (75%) parasites were collected from anterior intestine, 729 (77.08%) parasites from posterior intestine and 931 (95.83%) parasites were collected from caecum. lower intensity of infestation was found in duodenum (2.19 ±0.42). the highest intensity was found in anterior intestine (51.3±10.63). slightly higher intensity of infestation was found in caecum (20.23±2.60) and in posterior intestine (19.70 ±2.37) respectively (table i). in species mix distribution the highest prevalence of v. nana was recorded from anterior intestine (53.33%). while, lower prevalence was found in duodenum (41.66%). the highest prevalence of h. diminuta was found also in anterior intestine (50%). the lower prevalence was recorded in duodenum 4.16% and in posterior intestine (4.17%). but duodenum and caecum contain higher and equal prevalence (20.83%). on the other hand, 0% prevalence was found in stomach, duode num and anterior intestine in case of c. dispar, h. spumosa and s. muris. the highest prevalence of c. dispar was found in caecum (60.42%) and comparatively lower in posterior intestine (52.08%). but the highest prevalence (62.50%) was found in caecum both in case of h. spumosa and s. muris. the lower prevalence of them was found in posterior intestine 39.58% and 54.17% respectively. the intensity of v. nana showed the highest intensity in anterior intestine (61.71) while, parasites were totally absent in stomach, posterior intestine and caecum. lower intensity was found in duodenum (2.2). the highest intensity of h. diminuta was found in anterior intestine (5) and lower intensity (1) was found in duodenum, posterior intestine and caecum. the highest intensity of c. dispar and s. muris were found in caecum (11.79 and 13.83) and slightly lower intensity was found in posterior intestine (9.88 and 13.42). h. spumosa was showed the highest intensity in posterior intestine (6.84) and comparatively lower intensity were found in caecum (5.33) (table ii). the intestine of long-evans is a coil and long tube and its wall is consists of serosa, muscularis, submucosa and mucosa. these layers are arranged serially one below the other. the muscularis consists of thick circular and thin longitudinal muscle layer. the parasites were found firmly attached to the intestinal wall with their adhesive organs bearing gland cells or hooks by which they remain attached to the host mucosa. the parasites damaged the walls at the sites of their attachment. this disruption was mainly due to the action of sucker of helminth parasites. as a result the intestinal wall was heavily destroyed. in some cases, tissues were found to disappear completely (fig. 1-3). thus vacular structure appeared. fibrosis or necrosis and few pigments were also observed. table i. organ wise prevalence and intensity of helminth parasites in long-evans. organ total no. of total no. of prevalence total no. of intensity hosts examined hosts infected (%) worms collected (± sd ) stomach 48 0 0 0 0 doudenum 48 21 43.75 46 2.19 ±0.42 ant. intestine 48 36 75 1848 51.33 ±10.63 post. intestine 48 37 77.08 729 19.70 ±2.3 caecum 48 46 95.83 931 20.23 ±2.60 table ii. prevalence and intensity of organ wise each species of helminth parasites in long-evans. organ v. nana h. diminuta c. dispar h. spumosa s. muris no.of hosts infected 20 2 0 0 0 no. of worms collected 44 2 0 0 0 doudenum prevalence % 41.66 4.16 0 0 0 intensity 2.20 1.00 0 0 0 no.of hosts infected 28 24 0 0 0 no. of worms collected 1728 120 0 0 0 ant. intestine prevalence % 53.33 50.00 0 0 0 intensity 61.71 5.00 0 0 0 no.of hosts infected 0 2 25 19 26 no. of worms collected 0 3 247 130 349 post. intestine prevalence % 0 4.17 52.08 39.58 54.17 intensity 0 1.50 9.88 6.84 13.42 no.of hosts infected 0 10 29 30 30 no. of worms collected 0 15 342 160 415 caecum prevalence % 0 20.83 60.42 62.50 62.50 intensity 0 1.50 11.79 5.33 13.83 total number of host examined was 48, no parasite was found in the stomach. khanum, muznebina and nessa 209 khanum and arefin (2003) reported that in laboratory mice the prevalence of infestation was highest in anterior intestine (70.5%) and the lowest in stomach (5.83%). the intensity of infestation in laboratory mice was found lowest in duodenum and the highest in anterior intestine. from the above investigation indicates that the intestine and caecum is the favorite niche of most parasites where they were heavily abundant. abundance of v. nana was highest in anterior part of the intestine (small intestine) in long-evans in present observation supports jawdat and mahmoud (1980) who also found similar distribution. from histopathological investigation it was observed that, the intestine was affected and tissues were damaged seriously by v. nana and h. diminuta. degenerated tissues were observed within the folds around the parasites. the muscularis mucosa was found to be disrupted and damaged by the parasites. disrupted tissue of mucosa fig 1. transverse section of infected intestine of longevans (40 x 10). hemorrhages and lesion of villi fig 2. transverse section of infected intestine of long-evans (40 x 10). 210 nematode and cestode prevalence, organal distribution 44(2) 2009 conclusion the histopathological observation showed that the presence of parasites within the organs causes hazard to the host in many ways. heavy infection to the intestine may cause perforation and thereby physiological function might be abnormal. damage of villi tissues may cause many reactions to the host. acknowledgement the authors wish to offer thanks to dr. m. formuzul haque, ex. director, ifst, bcsir, dhaka for providing laboratory facilities during the research work. the authors are indebted to dipa islam, scientific officer, ifst, bcsir, dhaka, for her co-operation and helpful guidance. the authors are also grateful to m. abdur razzak, senior laboratory attendant, animal research section, ifst, bcsir, dhaka for his assistance during this research. references alam m. s., khanum h., and nessa z. (2003) helminth infection in laboratory rat strain, long-evans (rattus norvegicus berkenhout, 1769). bangladesh j. zool. 31(2): 221-225. bhuiyan a. i., ahmed t. a., and khanum h. (1996) endoparasitic helminths in rattus rattus linnaeus and bendicota bengalensis gray. j. asit. soc. bangladesh, sci. 22: 189-194. cable r. m. (1963) an illustrated laboratory manual for parasitology. burgress publishing company, minneapolis. pp. 169. huq m. m. (1969) a survey of the helminth parasites of roof rats rattus rattus, digger rats bendicota bengalensis and mole scalopus scalopus in mymensingh district, east pakistan. pak. j. vet. sci. 3: 65-68. jawdat s. z., and mahamoud s. n. (1980) the incidence of cestoidean and acanthocephalan parasites of some rodents in iraq. bull. nat. hist. res. centre. 7(4): 55-71. khanum h., and arefin n. (2003) helminth burden in laboratory mice, mus musculus. bangladesh j. zool. 31: 117-123. oldham j. n. (1931) the helminth parasites of common rats. j. helminth. 9: 49-60. shaha j. g. (1974) taxonomy of some of the helminths of house rats, house mice and house shrews of dacca city. m. sc. thesis. university of dhaka, bangladesh. pp. 120. stanley s. l. j. r., and virgin, i. v. h. w. (1993) scid as models for parasitic infections. parasitol today. 9: 406411. received : september, 03, 2008; accepted : december, 18, 2008 fig 3. transverse section of infected intestine of longevans (40 x 10). destructed and damaged mucosa and submucosa layers jahangir, mondal, nada, sarker, moniruzzaman and hossain. 6 response of different level of nitrogen and phosphorus 44(2) 2009 fille 2566 (15).qxd alkylation of cresols with cyclohexene in the presence of p-toluenesulphonic acid manoranjan saha*, haradhan chandra dey, mohammad ziaul karim, mohammad ismail and dipti saha department of applied chemistry and chemical technology, university of dhaka, dhaka-1000, bangladesh. abstract isomeric cresols have been cycloalkylated with cyclohexene in the presence of p-toluenesulphonic acid as catalyst. the effects of the variation of temperature, molar ratio of cresol to cyclohexene, time of reaction and amount of p-toluenesulphonic acid on the reactions have been studied and cyclohexyl cresols have been obtained in high yield. bangladesh j. sci. ind. res. 43(2), 277-282, 2008 short comuunication introduction alkylated phenols and their derivatives are outstanding antioxidants and stabilizers in fuels, lubricating oils and polymeric materials (babakhanov et al. 1968; lebedev, 1984; paul, 1950; ravikovich, 1964; shreve and brink, 1977).some of their derivatives are also used as herbicides, bactericides and insecticides (melinikov et al. 1954; nemetkin et al. 1951). cresols have been alkylated by different normal, isoand cycloolefins (karim et al.2005; kharchenko and zavgorodni, 1964; saha and ghosh, 1989; saha et al.1994; saha et al.1996; saha et al. 1998; saha et al.2000; shulov, 1969). but no attempt has ever been made to investigate the reactions with cyclohexene in the presence of p-toluenesulphonic acid. in the present work, reactions of isomeric cresols (ortho-, metaand para-) have been investigated with cyclohexene in the presence of p-toluenesulphonic acid as catalyst. materials and methods reaction was carried out in a flask fitted with a stirrer, a condenser, a thermometer and a dropping funnel for the addition of cyclohexene. cresol and p-toluenesulphonic * corresponding author, e-mail : manoranjansaha2005@yahoo.com bcsir avaiable online at www.babglajol.info bangladesh journal of scientific and industrial research e-mail: bjsir07gmail.com 278 alkylation of cresols with cyclohexene 43(2) 2008 acid were charged into the flask and heated to desired temperature and cyclohexene was introduced into the mixture gradually over a certain period of time (time of addition) with constant stirring. after the addition of total amount of cyclohexene, the reaction mixture was stirred for another period of time (time of stirring) at the same temperature. reaction mass was then cooled to the room temperature, dissolved in petroleum ether, neutralized and washed with distilled water several times. unconverted reactants and solvent were distilled off by distillation at atmospheric pressure. the residual product was finally distilled and characterized by spectral means. results and discussion a. reaction of o-cresol with cyclohexene: table i records the results of the reaction of o-cresol with cyclohexene in the presence of p-toluenesulphonic acid. the reaction gave the mixture of isomeric cyclohexyl ocresols. the yield of the products increased with the increase of temperature (expt. no. 1 5), molar ratio of o-cresol to cyclohexene (expt. no. 6 8), time of reaction (expt. no. 3 and 8) and the amount of catalyst (expt. no. 3 and 9). but the increase in the yield was negligible when the temperature was raised from 130 to 160oc (expt no. 3 5). thus cyclohexyl o-cresols could be obtained in 95.5% yield under the following reaction conditions: temperature = 130oc, molar ratio of o-cresol to cyclohexene = 5:1, time of addition = 2h, time of stirring = 2h and the amount of catalyst = 10% by wt. of o-cresol. b. reaction of m-cresol with cyclohexene reaction of m-cresol with cyclohexene had been investigated in the presence of p-toluenesulphonic acid over the temperature range of 100-130oc. molar ratio of m-cresol to 1 70 5:1 2 2 10 28.3 2 100 5:1 2 2 10 70.1 3 130 5:1 2 2 10 95.5 4 155 5:1 2 2 10 95.9 5 160 5:1 2 2 10 96.0 6 130 3:1 2 1 10 72.0 7 130 4:1 2 1 10 80.2 8 130 5:1 2 1 10 89.4 9 130 5:1 2 2 5 81.0 table i. alkylation of o-cresol with cyclohexene in the presence of p-toluenesulphonic acid expt. no. temp.,oc molar ratio of o-cresol to cyclohexene time of addition, h time of stirring, h amount of catalyst, % by wt. of o-cresol % yield of cyclohexyl o-cresol reaction conditions cyclohexene was varied from 3:1 to 4:1, reaction time from 2 to 4h and the amount of catalyst was varied from 5 to 10% wt. of mcresol. table ii records the results. the yield of products (cyclohexyl m-cresols) increased with the increasing temperature (expt. no.1 and 2), molar ratio of m-cresol to cyclohexene (expt. no. 3 and 4), time of reaction (expt. no.2, 4 and 5; 6 and 7) and the amount of catalyst (expt. no. 4 and 6). thus the best yield of cyclohexyl m-cresols was obtained under the following conditions: temperature = 130oc, molar ratio of mcresol to cyclohexene = 4:1, the amount of catalyst = 10% by wt. of m-cresol, time of addition = 2h and time of stirring = 2h. c. reaction of p-cresol with cyclohexene: the influence of variation of the parameters, viz. temperature, molar ratio of p-cresol to cyclohexene, time of reaction and amount of p-toluenesulphonic acid on the reaction of pcresol with cyclohexene has been shown in table iii. the reaction gave only 2-cyclohexyl-4-methylphenol. the yield of the product increased with the increasing temperature (expt. no. 1 3), molar ratio of pcresol to cyclohexene (expt. no. 4, 5 and 6), time of reaction (expt. no. 2, 4 and 7 ; 8 and 9) and the amount of catalyst (expt. no. 4 and 8). but the increase in the yield was insignificant when the temperature was increased above 130oc (expt no. 2 3). at a molar ratio of p-cresol to cyclohexene = 4:1, the maximum yield could be obtained by increasing the time of additional stirring (expt no. 2).the best yield of the product was obtained when the reaction was carried out under the following conditions: temperature = 130oc, molar ratio of p-cresol to cyclohexene = 4:1, the amount of catalyst = 10% by wt. of p-cresol, time of addition = 2h and time of stirring = 2h. saha, dey, karim, ismail and saha 279 1 100 4:1 2 2 10 61.2 2 130 4:1 2 2 10 96.4 3 130 3:1 2 1 10 82.3 4 130 4:1 2 1 10 86.0 5 130 4:1 2 0 10 72.5 6 130 4:1 2 1 5 75.1 7 130 4:1 2 3 5 87.5 table ii. alkylation of m-cresol with cyclohexene in the presence of p-toluenesulphonic acid expt. no. temp.,oc molar ratio of m-cresol to cyclohexene time of addition, h time of stirring, h amount of catalyst, % by wt. of m-cresol % yield of cyclohexyl m-cresol reaction conditions 280 alkylation of cresols with cyclohexene 43(2) 2008 1 100 4:1 2 2 10 64.5 2 130 4:1 2 2 10 96.6 3 160 4:1 2 2 10 96.7 4 130 4:1 2 1 10 88.7 5 130 5:1 2 1 10 95.9 6 130 6:1 2 1 10 96.2 7 130 4:1 2 0 10 76.1 8 130 4:1 2 1 5 76.9 9 130 4:1 2 3 5 95.2 table iii. alkylation of p-cresol with cyclohexene in the presence of p-toluenesulphonic acid expt. no. temp.,oc molar ratio of p-cresol to cyclohexene time of addition, h time of stirring, h amount of catalyst, % by wt. of p-cresol % yield of 2cyclohexyl-4methylphenol reaction conditions table iv. 1h nmr-spectrum of cyclohexyl cresols products observed signals of the protons chemical shift δ in ppm cyclohexyl three protons on the aromatic ring 6.01 7.0 o-cresol one proton on the -oh group 4.06 three protons on the -ch3 group 2.0 2.02 all the protons (10) on the cyclohexane ring except one on the α-position relative to the aromatic ring 1.05 2.16 one proton on the cyclohexane ring on the a-position relative to the aromatic ring 2.4 2.8 cyclohexyl three protons on the aromatic ring 6.06 7.1 m-cresol one proton on the -oh group 4.6 5.3 three protons on the -ch3 group 2.05 2.5 all the protons (10) on the cyclohexane ring except one on the a-position relative to the aromatic ring 1.06 2.0 one proton on the cyclohexane ring on the α-position relative to the aromatic ring 2.5 3.1 2-cyclohexylthree protons on the aromatic ring 6.3 7.1 4-methylphenol one proton on the -oh group 4.5 three protons on the -ch3 group 2.233 all the protons (10) on the cyclohexane ring except one on the a-position relative to the aromatic ring 1.20 2.17 one proton on the cyclohexane ring on the α-position relative to the aromatic ring 2.633 saha, dey, karim, ismail and saha 281 cyclohexyl group is substituted into the aromatic ring to the orthoor para-position with respect to the -oh group. therefore, the reaction of p-cresol with cyclohexene gave only one product, while the reactions of orthoand meta-cresols gave mixtures of isomeric cyclohexyl cresols. in the ir-spectrum of cyclohexyl o-cresol bands at 740-770 cm-1 accounted for the 1,2,3-trisubstituted benzene ring, while bands near 800-900 cm-1 were the characteristics of the 1,2,4-trisubstituted benzene ring. bands near 3400 cm-1 indicated the presence of -oh group. absorption band at 3400 cm-1 in the irspectrum of cyclohexyl m-cresols showed the presence of -oh group. bands near 800900 cm-1 were the characteristics of the 1,2,4-trisubstituted benzene ring. bands at 740-780 cm-1 accounted for the 1,2,3-trisubstituted benzene ring. ir-spectrum of 2-cyclohexyl-4-methylphenol showed absorption band at 3350 cm-1 (-oh). bands at 800-900 cm-1 accounted for the 1,2,4-trisubstituted benzene ring. the 1h nmr-spectrum of cyclohexyl cresols table iv. references babakhanov, r. a. gasanov, s.g. bakunina a.v. salimov, m.a.(1968) cycloalkylation of m-cresol by cyclo-olefins in the presence of sulphuric acid. azer.khim.zhim. zh. 1: 3639. karim, m.z. ismail, m. kamaruzzaman, m. saha, m. (2005) alkylation of o-cresol with cyclopentene in the presence of p-toluenesulphonic acid, bangladesh j. sci res, 40(34): 331-336. kharchenko, l.s. zavgorodni, s.v. (1964) alkylation of m-cresol with propylene, zh prikl khim, 37 (1): 165-170. lebedev, n.n. (1984) chemistry and technology of basic organic and petrochemical synthesis, mir publishers, moscow, 1&2: 638. melinikov, n.n. baskakov, y.a. bokrev, k.s. (1954) chemistry of herbicides and plants growth regulators. gkhi. moskow. 38. nemetkin, s.s. baskahov, y.a. melnikov, n.n. (1951) synthesis of some alkyl and arylkyl phenoxyacetic acid. zh. obsh. khim.12: 2146-2150. paul h, (1950) treatment for the improvement of lube oil, us 2 (529): 484. ravikovich, a.m. (1964) antioxidants for minerals and synthetic oils. chemistry and technology for fuels and oils, 11: 64-71. saha, m. ghosh, s.k. (1989) cyclohexylation of m-cresol. bangladesh j sci res 7(2): 273275. 282 alkylation of cresols with cyclohexene 43(2) 2008 saha, m. ghosh, s.k. saha, s.k. sarker, m.a.b. (1994) alkylation of p-cresol with cyclohexene in the presence of sulphuric acid. bangladesh j. sci res. 29(1): 144-148. saha, m. mosihuzzaman, m. saha, s. (1996) alkylation of pcresol with cyclohexene in the presence of benzenesulphonic acid. indian j. chem. technol. 3: 292 294 saha, m. mosihuzzaman, m. saha, s. (1998) alkylation of mcresol with cyclohexene in the presence of benzenesulphonic acid. bangladesh j. sci.ind. res. 33(1): 17-19. saha, m. mahmud, h.m.n.e. ghosh s.k. zaman, m.d. saha, d. hasan, m.a. (2000) reaction of o-cresol with cyclohexene in the presence of borontrifluoride etherate. bangladesh j. sci res. 18(2): 335-337. shreve, r.n brink j.a. (1977) chemical process industries, 4th ed. p-814. shulov, l.m. gavrilova, t.f. kheift, l.a. (1969) products of the alkylation of m-cresol by camphene. . zh.org. khim .5(1): 77-82. received : october, 10, 2005; accepted : august, 28, 2007 file 2413 (2).qxd bangladesh j. sci. ind. res. 41(1-2), 15-22, 2006 introduction vegetables are very important group of crops and they constitute a major part of the diet contributing nutrients, especially vitamins, minerals and protein. they also make our diet more palatable and variable.1 in bangladesh, daily per capita consumption of vegetable is 50 g compared to 432 g in japan.2 in the country, per head availability and consumption of vegetable is very low compared to daily requirement (200 g) due to their acute shortage.3 high yielding vegetables production may be answer to the potential problems of hunger and malnutrition. the participation of different categories of farmers for the production and utilization of lady's finger (hibiscus esculentus l.) m. harunur rashid, m. nur-e-elahi and m. akhter hossain khan rfs division, bangladesh rice research institute, gazipur-1701, bangladesh abstract a study was conducted at the farming systems research and development (fsr&d) site of bangladesh rice research institute (brri) during kharif-i, 1999 to find the agronomic management followed for lady's finger cultivation by the different categories of farmers and to understand its production, consumption and disposal pattern together with its economy. technical knowledge was provided to the farmers for growing lady's finger. farmers grew the crop with their own management and resources. variation was found in the date of sowing, rate of fertilizer application and number of irrigation. the highest pod yield was associated with better agronomic management that resulted higher gross margin. lady's finger production, consumption and selling were increased from april to june with a peak in the month of june. lady's finger consumption was highest per head in case of medium farmer and was decreased from medium farmer to marginal one. the utilization of money earned from lady's finger selling followed a dissimilar pattern in different categories of farmers. cultivation of lady's finger might be an option for meeting the requirement of vegetable consumption, income generation and fulfilling the diversified demand of different category of farmers. in bangladesh 70 % of the total vegetable production is produced in the winter due to suitable climatic condition for vegetable production.4 in the country there are two scarce period for vegetable supply, from april to may and september to october.5 cultivation of high yielding lady's finger is an option to increase the supply of vegetables during april to may. lady's finger is a major kharif vegetable, which has high nutritive value. it is a source of carbohydrate, fibre, protein, nayacin, vitamin and iron. besides, 100 g edible lady's finger contains 1.2 k cal energy.6 but, yellow vein mosaic disease is a major problem for lady's finger growing in bangladesh. a recently released lady's finger variety, baridheros-1 released by bangladesh agricultural institute is resistant to the virus that makes lady's finger cultivation easier and profitable in bangladesh. baridheros-1 is flowered about 45 days after sowing and its pod harvest continued from 50 days after sowing to 5 months of its age.6 usually lady's finger is planted during the month of february and march where there is acute shortage of soil moisture which may cause delay in germination or some times complete failure of germination resulting in poor yield.7 although lady's finger is very much popular in bangladesh, the yield of the crop is very low, 3.11 t ha-1.8 on the other hand, the yield of lady's finger varied from 11 to 15 t ha-1 from region to region.6 lack of knowledge about some cultural practices has contributed to the poor yield of lady's finger.9 besides this, lady's finger producing farmers do not follow the recommended practice of input use due to higher market price and lack of facilities.10 as farmers have not sufficient access to input use, recommended agronomic management do not sustain at farmer's level. for sustainable higher production of lady's finger, consideration of farmers' participatory management is imperative. lady's finger is an income generating summer vegetable. it may increase the farmers' income as well as reduce the shortage of vegetable consumption. moreover, the cultivation of the crop helps to generate family labour employment greatly.10 economic return from lady's finger cultivation may vary in different categories of farmers. the amount of production and earned money from lady's finger cultivation may affect the utilization pattern for family expenditure in different categories of farmers. the disposal pattern of the money earned from lady's finger cultivation may help the researchers to design their research plan for different categories of farmers. therefore the present study was undertaken with the following objectives: i. to find the agronomic management practices of lady's finger by different categories of farmers; ii. to find the factors influencing the yield and economic return; 16 the participation of different categories of farmers 41(1-2) 2006 iii. to see the production, consumption and selling pattern of produced lady's finger; iv. to observe the prices pattern of lady's finger in the growing season; v. to find lady's finger consumption per head by different categories of farmers; vi. to note money utilization pattern earned from lady's finger by different categories of farmers. materials and methods the study was conducted at the farming systems research and development (fsr&d) site of bangladesh rice research institute (brri), kapasia during kharif-i 1999. the study area belongs to modhupur tract of agro-ecological region 28. the variety, baridheros -1 was used in the study. seeds of lady's finger (hibiscus esculentus l.) were distributed among six farmers taking two from each category, marginal to large in the first week of february 1999. technical knowledge was provided to the farmers for growing lady's finger. unfortunately, one farmer of marginal category could not cultivate the crop due to lack of sufficient moisture in the soil. during the growing period of the crop, the monthly minimum and maximum air temperatures were 15.7o c and 32.5o c, respectively, in february and april. a total of 8.6 mm, 325 mm, 338 mm. and 528 mm rainfall were recorded in the month of april, may, june and july respectively. there was no rainfall during the months of february and march. farmers grew this crop with their own inputs. the plot size of marginal, small-1, small-2, medium-1 and medium-2 farmers were 175, 225, 290, 500 and 250 m2 respectively. seeds were sown by the participating farmers at different dates at 50 cm row spacing and 40 cm plant spacing. two seeds were sown in every pit and one seedling was uprooted remaining a healthy seedling at 4-5 leaf stage. fertilizer rates and all other management practices differed from one farmer to another. lady's finger harvesting was started in the second week of april and continued up to fourth week of july. the other key management practices used for lady's finger cultivation are described in table i. data on harvesting, consumption, selling were recorded farmer wise twice a week and calculated these monthly bases. economic analysis of lady's finger production was done based on prevailing farm gate price. simple tabular and graphical method of analysis was carried out to arrive at results. results and discussion key agronomic management table i indicated that agronomic management for lady's finger cultivation varied from farmer to farmer. noticeable variation was found in dates of sowing, rate of fertilizer application and number of irrigation. date of sowing started from february 26 to march 16. a marginal farmer applied only nitrogenous fertilizer at the rate of 61 kg n ha-1. the rashid, elahi and khan 17 18 the participation of different categories of farmers 41(1-2) 2006 management factors land preparation a) no. of plough b) no. of level date of sowing row x hill spacing (cm) date of germination fertilizer rate : (n-p-k kg ha-1)* no of weeding with date no. of irrigation with date marginal farmer 4 4 march 14, 1999 50 x 40 march 19, 1999 61-0-0 2, 32 & 46 das small farmer 1 5 6 march 16, 1999 50 x 40 march 21, 1999 60-18-45 2, 30 & 50 das 2, 20 & 95 das small farmer 2 4 4 march 7, 1999 50 x 40 march 12, 1999 60-0-0 2, 30 & 55 das medium farmer 1 4 4 feb. 26, 1999 50 x 40 march 3, 1999 51-20-38 2, 25 & 52 das medium farmer 2 4 4 march 6, 1999 50 x 40 march 11, 1999 30-0-30 2, 28 & 60 das table i. agronomic management for lady’s finger cultivation followed by different categories of farmer *recommended rate of fertilizer : 69, 20 and 75 kg n, p and k ha-1, respectively. small farmer-1 and small farmer-2 applied equal dose of nitrogen, which was 60 kg n ha-1. the small farmer-1 also used p and k @ 18 and 45 kg ha-1. the medium-1 and medium farmer-2 applied n @ 51 and 30 kg n ha-1; 38 and 30 kg k ha-1, respectively. the medium farmer-1 also used 20 kg p ha--1. all the participating farmers applied nitrogenous and potassium fertilizer less than recommended rate. the medium farmer-1 and small farmer-1 used equal or close to recommended rate of phosphorus fertilizer (table i). however, they did not follow the recommended package of fertilizers. only small farmer-1 gave two supplemental irrigations in his lady's finger plot. in the production process of lady's finger, all the farmers followed the recommended row and plant spacing and the number of seedling per pit. yield of lady's finger in different categories of farmers the pod yield of lady's finger varied from 6.9 to 18.9 t ha-1 in relation to farmer's category (table ii). the pod yield did not exceed 8 t ha-1 except a small farmer. the highest pod yield (18.9 t ha-1) was found in case of small farmer-1. this higher yield might be attributed to the application of close to recommended p and higher k than other farmers rashid, elahi and khan 19 farmer’s category marginal small farmer-1 small farmer-2 medium farmer-1 medium farmer-2 yield (t/ha) 7.9 18.9 7.0 8.0 6.9 gross return (tk/ha) 87,086 188,311 75,948 98,060 68,760 total variable cost (tk/ha) 25,024 28,015 24,949 27,259 25,969 gross margin (tk/ha) 62,062 160,296 50,999 70,801 42,791 table ii. yield and economic return of lady’s finger obtained in different categories of farmers along with nitrogen fertilizer and two supplemental irrigations (table i). the findings were partial agreement with the results of other researchers11, 12 where they stated that the recommended rate of nitrogen in combination with phosphorus and potassium gave the higher pod yield. economic analysis indicates that the small farmer who used the better agronomic management got the highest gross margin of taka 1,60, 296 ha-1. it was due to higher pod yield. monthly production, consumption and selling pattern of lady's finger figure 1 shows the monthly production, consumption and selling pattern of lady's finger of different farmers for the months of april to july. from the figures, it is observed that lady's finger harvesting continued to increase up to june and thereafter it was declined. consumption and selling also maintained the same trend. the higher consumption and selling were associated with the higher rate of harvesting. per head lady's finger consumption and value of consumed lady's finger the number of family members of marginal and small farmers was six whereas it was 10 and 14 in medium farmer-1 and medium farmer-2, respectively. per head lady's finger consumption was the highest in the medium farmer-1 and it was decreased with medium farmer-2, marginal farmer and small farmer1 (fig. 2). it was due to consumption of other food for their daily menu. the age bar might be another cause for this variation. prices pattern of lady's finger figure 3 indicates that the price of per kg lady's finger was the highest in the second week of april e.g. tk. 16.00 kg-1. the price of lady's finger was unchanged from the third week of april to second week of may and thereafter it was gradually declined. farmers' participatory production of lady's finger might be motivated the neighbouring 20 the participation of different categories of farmers 41(1-2) 2006 fig. 1a utilization pattern of okra of marginal farmer fig. 1b utilization pattern of okra of small farmer-1 fig. 1c utilization pattern of okra of small farmer-2 fig. 1e utilization pattern of okra of medium farmer-2 fig. 1. monthly production, consumption and selling pattern of okra in different categories of farmers fig. 1d utilization pattern of okra of medium farmer-1 rashid, elahi and khan 21 fig. 2. per head okra consumption pattern of the different farmer categories fig. 3. prices pattern of okra in different weeks from april to july farmers to grow the crop following the management at their resource level. lady's finger cultivation might meet the requirement of vegetable consumption as well as help in income generation and fulfil the diversified demand of family. references 1. s. c. s. tsou. vegetables production and marketing. proceedings of a national review and planning workshop. avrdc/bari/barc: usaid arp = ii supplement, (1992) 21-30. 2. s. s. rekhi. vegetable improvement and seed production in bangladesh. paper presented in the national seminar on vegetable improvement and seed production held at bangladesh agricultural research institute, (1997). gazipur, bangladesh. 3. barc (bangladesh agricultural research council). farming systems agribusiness newsletter, 1990, april-june issue. dhaka, bangladesh. 4. m. a. razzaque, m. a. sattar, m. s. amin, m. a. quayyum and m. s. alam. (ed.) hand book on agro-technology. second ed. (in bangla). bangladesh agricultural research institute, gazipur, (2000) 313. 5. m. m. rashid olericulture (in bangla), 1999. rashid publishing house; 94, old d.o.h.s., dhaka. 6. s. m. hossain. (ed.) modern varieties of vegetables and cultivation methods (in bangla), olericulture division, horticulture research center, bangladesh agricultural research institute, gazipur, (2000) 48-49. 7. m. g. rasul, m. a. sattar, m. a. mannan and m. m. rashid. effect of mulching and earthing up on the performance of mukhikachu. bangladesh hort. 20(1) (1992) 51-54. 8. bbs (bangladesh bureau of statistics). statistics division, ministry of planning, dhaka. monthly statistical bulletin bangladesh, april (2000). 9. p. k. saha, d. k. aditya and a. f. m. sharfuddin. effects of plant spacing and picking interval on the growth and yield of lady's finger cv. pusasawani. bangladesh hort. 17(2) (1989) 10-14. 10. m. i. hossain, m. s. rahman and r. islam. impact study of improved technology of lady's finger cultivation. bangladesh j. agril. res. 25(3) (2000) 529-540. 11. g. p. chaudhari, k. g. mahakal, a. s. shrirame, s. u. gondane and v. j. kawarkhe. performance of lady's finger varieties in relation to fertilizer application. pvk res. j. 19 (1) (1995) 95-96. 12. a. fayaz, m. ishtiaq, s. muhammad and f. ahmad. effect of different levels of nitrogen alone and in combination with constant doses of phophorus and potassium on growth and yield of lady's finger cv. t-13. sorhad j. of ag. 15(5) (1999) 405-407. 22 the participation of different categories of farmers 41(1-2) 2006 fille-2766(5).qxd introduction potato is one of the most important crops in bangladesh. owing to promotional effort of government it is being placed as a third crop next to rice and wheat (haq and matin. 2006). potato is the third largest food crops of bangladesh (rashid, 1999). every year in bangladesh, the potato field becomes flooded and the floodwater especially in lowlying areas recedes from the field very late. non saline phase of the ganges tidal flood plain of southern region of bangladesh comprise part of barisal, patuakhali, and barguna districts characterized by tidal flooding of field, high rainfall in monsoon and short winter. rice is the main crops grown in the kharif season. during the rabi season, land mainly remain fallow. reason for fallow in the winter season delay of harvest of transplanted aman rice and wetness of soil. land becomes free and soils comes to working condition at the end of the november to first week of january which is the time not optimum for sowing of many rabi crops due to most of the land cultivated bangladesh j. sci. ind. res. 44(1), 51-56, 2009 *corresponding authour bcsir available online at www.banglajol.info bangladesh journal of scientific and industrial research e-mail: bjsir07@gmail.com effect of mulching material on the yield and quality of potato varieties under no tillage condition of ganges tidal flood plain soil m. a. razzaque*a and m. a. alib aregional agricultural research station, bangladesh agricultural research institute rahmatpur, barisal and bsoil resource development institute farmgate, dhaka abstract the field experiment was carried out during rabi season of 1999-2000 to 2000-2001 with five recommended potato varieties viz. heera, dhera, diamant, chamak and cardinal along with two types of mulching materials viz rice straw and water hyacinth to find out suitable variety (ies) and mulching material(s) for obtaining higher yield under no tillage condition. heera produced highest yield under both rice straw (19.45 t/ha) and water hyacinth (23.15 t/ha) mulch. rest of the variety performed more or less similar in both cases. both heera and dhera seemed to be suitable for cultivation in no tillage condition. key words: potato varieties, mulching material, yield and quality. under local t. aman and this aman rice harvest up to 1st week of january. that is why; planting of potato following the traditional methods becomes delayed which directly affects the yield. due to slow recession of floodwater, planting of seed tubers sometime is not possible even in the month of december (hoque, 2001). the technology of potato cultivation without tillage has been developed for those areas (rashid, 1999). in this method, whole tubers of potato are planted directly to the wet field immediately after removal of floodwater and then the field is covered by thick mulch (annon. 2000). thick mulch helps to retain sufficient moisture in the soil. cut tubers should not be used in this method (razzaque et al., 2000). in some areas of bangladesh, farmers are practicing this technology but they are using different varieties and different mulching materials. no screening trials were conducted so far with the existing potato varieties that perform better under no tillage condition and also no mulching material was standardized. some farmers use straw as mulch and some others use water hyacinth. they are also not aware of thickness of the mulch. for this reason they are not getting expected yield of potato. hence, an investigation was undertaken with five recommended potato varieties and two mulching materials with the following objectives: 1. to find out suitable potato variety (ies) that perform better under no tillage condition and 2. to find out suitable mulching material(s) for obtaining higher yield in potato cultivation under no tillage condition. materials and methods the field trial was conducted at the farming system research site lebukhali patuakhali of bangladesh agricultural research institute (bari), during the rabi season of 19992000 and 2000-2001 having sandy loam soil. the experimental soil exists ph 6.3, organic matter 0.95 (%), k 0.58 (%). tubers of five recommended varieties of potato viz. heera (v1), dhera (v2), diamond (v3) chamak (v4) and cardinal (v5) along with two types of mulching materials viz rice straw (m1) and water hyacinth (m2) were included for the study. the experiment was set up in randomized complete block design (rcbd) with three replications. the unit plot size was 6.0m x 4.0m. immediately after recession of flood water, whole tubers were planted maintaining a distance between rows 60cm and between plants 25cm. potato was planted 7 december in both the years. fertilizers were applied @ 330-220-250120-14-6 kg of urea, triple super phosphate (tsp), puriate of potash (mp), gypsum, zinc sulphate and boric acid per hectare respectively (anon., 2002). full amount of tsp, mp, gypsum, zinc sulphate, boric acid and half of the urea were applied before planting by broadcast and properly mixed with soil so that the tuber does not come in contact with the fertilizers during planting. the remaining 52 effect of mulching material on the yield 44(1) 2009 razzaque and ali 53 urea was top dressed before irrigation at around 30-35 days after planting. before planting, shallow furrows were made by a stick where the tubers were planted in wet soils by placing them in the particular place and pressing slightly. after that, the plots were covered by thick mulch (6-8 inch). irrigation water was sprayed over the field immediately after top dressing of urea. weeding and other intercultural operations were done as and when necessary for raising the crop. the crop was sprayed with redomeal mz 72 and dimecron to prevent diseases and insects. the dates of harvesting were 10th march 2000, respectively and 14th march 2001. the collected data were analyzed with the help of computer mstatc software and the means were separated by lsd test. results and discussion effect of variety performance of different potato varieties on the yield and quality of potato are presented in (table i). it is revealed that the highest plants per (117.37) were recorded from heera followed by chamak. other varieties also gave similar result. the variety heera produced maximum tuber per plant (8.52). it might be due to its long stolon characters. tuber produced by other varieties was very close. the highest tuber weight was recorded by variety heera (51.03 g) followed by chamak (49.64 g). it is established that fact potato varieties produced tuber with second growth in a condition of water deficiency leading to rise in soil temperature (annon, 1998, rashid, 1984; hoque et. al. 2004). the heera 60.18 117.37 8.52 51.03 21.302 dhera 55.47 116.37 8.00 49.15 19.276 diamont 58.93 116.5 7.91 48.14 18.541 chamak 57.12 117.0 7.29 49.64 17.638 cardinal 56.87 116.87 7.60 49.52 18.237 cv(%) 3.69 0.32 2.02 1.46 2.26 lsd (0.05) 3.037 0.584 0.243 1.11 0.662 variety plant height (cm) plant/plot tuber/plant tuber weight (g) yield (t/ha) table i. yield and yield contributing characters of potato variety as affect by mulching under no tillage condition (pooled). 54 effect of mulching material on the yield 44(1) 2009 lowest tuber per plant was recorded (48.14 g) in diamont. these findings agreed with hoque et al, (2004). among the varieties tuber yield was ranged from 21.302-17.638 t/ha with an average on 19.0 t/ha. the variety heera produced higher tuber yield (21.30 t/ha), which was statistically different from other varieties. it might be due to higher number of tuber per plant and higher tuber weight. effect of mulching material effect of different mulching materials on the yield of potato is presented in (table ii). the maximum tuber per plant was recorded by mulching material of water hyacinth compare than rice straw. it implies that there were water stress because straw mulch could not cover the tubers properly for which there was less moisture in the soil. tuber weights were higher in water hyacinth. regarding yield it was found that when water hyacinth was used as mulching materials the tuber yield was maximum (20.26 t/ha). reason might be behind that water hyacinth retained moisture in the soil for longer period, which was ultimately, increased tuber yield. interaction effect of variety and mulching interaction effect of different variety and mulching materials are presented in (table iii). all the varieties grown under water hyacinth produced higher yield except the variety chamak. chamak produced higher yield (17.76 t/ha) in rice straw mulching compare than water hyacinth mulching (17.5 t/ha). water hyacinth gave higher tuber per plant and tuber weight. another reason soil temperature under straw mulch was higher than that of water hyacinth. maximum yield was recorded heera variety (2.15 t/ha). this finding agreed with hoque et al (2004). it implies that the variety heera can produce good yield either any of mulching materials. tuber quality tuber quality was affected by mulching and varietal performance, which were presented in (table iv.) during grading of tuber it was found that small sized tubers ranged from 30.2% to 40.0% by weight and larged sized tubers ranged from 15.8% to 12% by weight. maximum medium sized tubers were (50.2%) produced in heera under water hyacinth water hyacinth 58.80 117.05 8.11 50.44 20.264 rice straw 57.65 116.70 7.65 48.55 18.064 mulching material plant height (cm) plant/plot tuber/plant tuber weight (g) yield (t/ha) table ii. yield contributing characters of potato variety as affect by mulching under no tillage condition (pooled value) razzaque and ali 55 green tuber (by %wt.) (g) heera 61.72 118.25 8.99 52.31 23.155 dhera 58.94 116.50 8.66 49.80 20.920 diamont 59.12 116.50 8.18 48.79 19.367 chamak 57.00 117.00 7.11 50.52 17.516 cardinal 57.25 117.00 7.62 50.80 18.863 heera 58.75 116.50 8.06 49.75 19.450 dhera 57.00 116.0 7.52 48.50 17.632 diamont 58.75 117.00 7.56 47.50 17.715 chamak 57.25 117.25 7.46 48.75 17.760 cardinal 56.00 116.75 7.57 48.25 17.612 4.83 0.73 2.34 2.56 4.16 4.078 1.235 0.267 1.837 1.14 treatment mulch variety plant/plot plant height (cm) tuber/plant tuber weight (g) yield (t/ha) table iii. interaction of mulching and varieties on the yield and yield attributes potato (pooled) heera 5.2 40.0 50.2 12.0 dhera 6.8 35.0 48.3 15.6 diamont 6.2 34.2 47.5 14.5 chamak 6.8 32.2 47.2 15.4 cardinal 6.3 30.2 46.3 15.8 heera 6.3 39.2 48.2 12.3 dhera 7.5 34.2 46.3 14.3 diamont 7.3 33.5 45.2 14.1 chamak 7.2 32.5 46.1 13.7 cardinal 7.1 30.4 45.0 13.3 treatment mulching variety <28 mm 28-55 mm >55 mm grades of tubers by size (%) table iv. tuber quality as affected by mulching and variety of lebukhali patuakhali during rabi season ( pooled value) cv(%) lsd (0.05) rice straw water hyacinth rice straw water hyacinth 56 effect of mulching material on the yield 44(1) 2009 mulching and minimum in cardinal 45% of rice straw mulching. medium size tubers are very important because they have more market value. minimum green tuber was produced water hyacinth mulching and maximum was recorded in rice straw. it was revealed that water hyacinth covered potato tubers properly and sunlight cannot contact with tubers. conclusion from the above invetigation it can be concluded that tubers of heera can be planted under water hyacinth or rice straw mulch but better production under water hyacinth mulch under no tillage condition. so, water hyacinth can be used as mulching material while planting potato under no tillage condition. to avoid greening, thick water hyacinth mulch of 10-12 cm can be used. references haq, a. s. m.a. matin, m.a. (2006) a study of potato export from bangladesh. bangladesh j. agril. res. 31(2): 259-266 rashid, m.m. (1999) shabji bijnan (in bengali). vegetable production. 2nd edition. rashid publishing house, 94, old dohs, dhaka1206. pp: 141-142. hoque, m.a. (2001). final report on post flood rehabilitation and adaptive research support project, bari, munshiganj. bari, munshiganj and barc, dhaka. pp: 28-29. anonymous, (2000) bina chashe alu utpadon (in bengali). potato production with no tillage condition (a folder). tuber crops research centre, bangladesh agricultural research institute, joydebpur, gazipur. razzaque, m.a. satter, m.a. amin, m.s. quayyum, m.i. alam, m.s. (2000) edited. krishi projukti hatboi (in bengali). handbook on agro-technology. 2nd edition. bangladesh agricultural research institute, joydebpur, gazipur-1701, bangladesh. pp: 201-202. anonymous (1998). annual report of tcrsc, 1997-1998. tuber crops research sub centre, bangladesh agricultural research institute, munshiganj. rashid, m.m. (1984). alur chash (in bengali). cultivation of potatoes. second edition. bangla acedamy, dhaka, bangladesh. pp136. hoque, m.a. islam, m.r. faruquei, m.a.b. ahmed, u. khan, m.a.i. (2004). yield and quality of potato as affected by variety and mulching under no tillage condition. j. subtrop. agric. res. dev. 2(2): 20-23. received :april 16, 2008; accepted : august 18, 2008. file 2539 (5).qxd bangladesh j. sci. ind. res. 41(1-2), 41-46, 2006 introduction cabbage is an important and nutritious winter leafy vegetable in our country. it contains a range of essential vitamins and minerals as well as small amount of protein and good caloric value. in recent years vegetable consumption has increased. however, the productivity of cabbage per unit area is quite low as compared to the developed countries of the world.1 among the various factors involved nutrient supply is an important inputs for realizing higher cabbage yield and its nutrient content. experimental evidence showed that the response of cabbage is high to nitrogen application and moderate to phosphorus application.2-3 several authors reported the importance of n-p fertilizer on the productivity and nutritional quality of cabbage.4-5 the information regarding n-p fertilizer on cabbage yield and its nutritional quality is very meagre in our local climatic condition. therefore, attempts have been made in the present investigation to study the response of various level of nitrogenphosphorus application on cabbage yield and its nutrient content. yield and nutritional quality of cabbage as affected by nitrogen and phosphorus fertilization k. m. f. haque,a a. a. jahangir,b m. e. haque,a r. k. mondal,b m. a. a. jahanb and m. a. m. sarkerb aifst, bcsir, dhaka, bbcsir labs, dhaka, dr. qudrat-i-khuda road., dhanmondi, dhaka-1205, bangladesh abstract an experiment was conducted in field condition to study the effect of nitrogenphosphorus fertilization on growth, yield and nutrient content of cabbage. the experiment was laid out in randomize block design with three replications. the yield and yield components were maximized by n3p2 fertilizer treatment. nutrient content of cabbage varied with fertilizer treatment. the maximum amount of reducing sugar, ascorbic acid, phosphorus were found at the highest rate of n p fertilization whereas accumulation of titrable acidity, iron, calcium were maximum at the rate of n2p2 treatment. however ph, ash content were more or less same throughout the experiment. materials and methods the experiment was carried out at bcsir agronomic field dhaka during rabi season 2002-2003 using the variety atlas-70. the soil of the experimental field was sandy clay loam having a ph 5.8, 1.52 % organic matter and 0.04 % total nitrogen, available sulphur (10 ppm), available phosphorus (15 ppm). the experiment was laid out in a randomized block design with three replications. the unit plot size was 3m x 6m. the row to row and plant to plant spacing were 60 and 40 cm respectively. the nitrogen fertilizer doses under study were 60 kg n/ha (n1), 120 kg n/ha (n2), 180 kg n/ha(n3), and that of phosphorus were 30 kg p2o5/ ha (p1), 60 kg p2o5/ ha (p2) and 90 kg p2o5/ ha (p3). the source of nitrogen and phosphorus were urea and triple super phosphate respectively. at the time of land preparation nitrogen and phosphorus were applied in the field. all the intercultural operation were done in proper time. at harvest time 10 plants were selected at random from each plot to collect data on plant height and yield components were recorded on the selected plants. the total yield were recorded from the whole plot. each individual cabbage was divided longitudinally in four equal parts. only composite sample taken from these parts were used for the determination of moisture, protein, total sugar, reducing sugar and titrable acidity by standard method of aoac.6 the ph and total soluble solids (tss) were determined by using standard ph meter and abb's refractometer respectively. ash was determined by heating sample at 600o c for six hours or until a constant weight was reached. vitamin c was analyzed by the titrimetric method using 2, 6, dichlorophenol-indophenol dye.7 the minerals were determined by the method described in a manual of laboratory techniques.8 the collected data were statistically analyzed following the principles of analysis of variance and duncan's new multiple range test.9 results and discussion the results on the effect of nitrogen and phosphorus on the growth, yield components have been presented in table i. the maximum plant height (23.31cm) was recorded with the application of 180 kg n and 30 kg p2o5 per hectare which is closely followed by n2p3 treatment (22.50 cm). the minimum plant height was recorded from control treatment. the maximum head diameter of cabbage (20.41 cm) was produced from the plot receiving fertilizer at the rate of 180 kg n + 60 kg p2o5 per hectare. this is followed by n3p1 treatment. these two treatments are significantly different from the rest of the treatments. k. srinivas recorded increase head diameter of cabbage by increased n application with p-fertilizer.10 the head thickness size of cabbage were found to vary 12.00 cm to 15.42 cm. the maximum weight of cabbage per plant was noticed at n3p2 treatment. the 2nd highest per plant was obtained from n3p1 treatment. the results indicate that n and p had a 42 yield and nutritional quality 41(1-2) 2006 pronounced effect on the yield of cabbage. the maximum cabbage yield 65.11 t/ha was found from the plot receiving fertilizer at the rate of 180 kg n + 60 kg p2o5 per hectare. the yield production increase progressively with the increase amount of n-fertilizer along with phosphorus fertilizer. similar results were reported by f. m. humadi et al. and mohans et al.11-12 the highest amount of total solid in cabbage was found at n3p3 treatment. it was significantly higher than the rest of the treatments. the next value was obtained from n3p2 treatment. control treatment produced the lowest amount of total solid. the protein content of cabbage was found maximum from the plot receiving fertilizer at the rate of 180 kg n + 60 kg p2o5 kg/ha. it was closely followed by n3p3 treatment. the results are in partial agreement with the results of tanaka et al.13 who found higher content of protein by using higher amount of nitrogen level. the maximum amount of tss was found from n3p2 treatment which is closely followed by n3p3 treatment. lowest value of tss are found in control and n1p1 treatment. the change of ph and ash component was insignificant during the growth period of cabbage in the experiment. reducing sugar content was found maximum from n3p3 treatment. the 2nd highest was obtained from the plot receiving fertilizer at the rate of 180 kg n + 60 kg p2o5 kg /ha. the treatments n2p2 and n2p3 have same value of reducing sugar. the range of titratable acidity in cabbage is between 34.54 to 41.27. the highest value produced from n2p2 treatment. haque, jahangir, haque, mondal, jahan and sarker 43 fertilizer treatments table i. effect of nitrogen-phosphorus fertilization on growth and yield component of cabbage. * means with the same letter are not different from one another at the 5 % level of significance. control 19.10 b 17.90 c 12.00 c 1.60 b 1.20 c 45.71 c n1 p1 19.41 b 18.21 c 12.25 c 1.67 b 1.25 bc 46.12 c n1 p2 19.50 b 18.22 c 13.51 b 1.98 bc 1.60 abc 53.60 b n1 p3 21.71 ab 19.13 b 13.62 b 1.99 bc 1.62 abc 53.41 b n2 p1 21.53 ab 19.19 b 14.60 ab 2.00 bc 1.61 abc 53.79 b n2 p2 21.70 ab 19.13 b 14.71 ab 2.47 ab 1.68 ab 58.89 ab n2 p3 22.50 a 19.18 b 14.58 ab 2.48 ab 1.72 ab 59.41 ab n3 p1 23.31 a 20.39 a 15.40 a 2.85 a 1.82 a 64.50 a n3 p2 22.41 a 20.41 a 15.42 a 2.88 a 1.85 a 65.11 a n3 p3 21.80 ab 19.20 b 14.57 ab 2.48 ab 1.72 ab 59.12 ab plant height (cm) head size diameter (cm) head size thickness (cm) total weight/ plant (kg) edible weight/ plant (kg) cabbage yield (t/ha) 44 yield and nutritional quality 41(1-2) 2006 fertilizer treatments table ii. effects of nitrogen-phosphorus fertilization on total solid, protein, total soluble solid, ash, ph, reducing sugar, titratable acidity content of cabbage. (amounts per hundred g of edible portion). * means with the same letter are not different from one another at the 5 % level of significance. control 5.96 c 1.13 c 4.36 c 0.38 a 6.40 a 1.81 b 34.54 c n1 p1 5.98 c 1.25 c 4.36 c 0.38 a 6.40 a 1.82 b 39.25 bc n2 p1 6.15 b 1.35 bc 4.38 c 0.37 a 6.40 a 1.83 b 39.24 bc n3 p1 6.16 b 1.40 b 5.52 b 0.39 a 6.39 a 1.82 b 40.86 ab n1 p2 6.13 b 1.34 bc 5.53 b 0.38 a 6.39 a 1.82 b 40.86 ab n2 p2 6.16 b 1.49 ab 5.59 b 0.38 a 6.41 a 1.90 ab 41.27 a n3 p2 6.30 a 1.56 a 5.59 b 0.36 a 6.41 a 1.90 ab 40.87 ab n1 p3 6.14 b 1.41 b 5.59 b 0.37 a 6.39 a 1.91 ab 40.85 ab n2 p3 6.15 b 1.40 b 6.71 a 0.38 a 6.40 a 2.13 a 39.26 bc n3 p3 6.15 b 1.41 b 6.22 ab 0.38 a 6.40 a 2.15 a 39.27 bc total solid (g %) protein (g %) total soluble solid (g %) ash (g %) ph reducingsugar (g %) titratable acidity (mg citric acid equivalent) fertilizer treatments table iii. effects of nitrogen-phosphorus fertilization on ascorbic acid, iron, phosphorus, calcium, sodium and potassium content of cabbage (amount per hundred g of edible portion). * means with the same letter are not different from one another at the 5 % level of significance. control 11.04 c 0.40 c 14.10 c 24.21 b 16.29 c 111.14 b n1 p1 11.10 c 0.42 c 14.12 c 24.30 b 17.31 c 111.19 b n1 p2 11.39 bc 0.47 b 14.43 bc 24.31 b 18.37 b 113.11 ab n1 p3 11.39 bc 0.46 b 14.41 bc 25.78 ab 18.40 b 113.20 ab n2 p1 11.40 bc 0.55 a 14.45 bc 27.07 a 19.15 a 113.20 ab n2 p2 11.41 bc 0.56 a 14.74 b 27.09 a 18.39 b 113.22 ab n2 p3 11.61 b 0.55 a 14.72 b 25.92 ab 18.39 b 113.21 ab n3 p1 11.62 b 0.49 ab 14.76 b 25.89 ab 18.36 b 114.51 a n3 p2 11.64 b 0.48 ab 14.78 b 25.88 ab 17.31 c 114.49 a n3 p3 13.10 a 0.49 ab 15.46 a 25.91 ab 18.32 b 114.50 a ascorbic acid (mg %) iron (mg %) phosphorus (mg %) calcium (mg %) sodium (mg %) potassium (mg %) the highest rate of n p fertilizer gave the highest concentration of vitamin c. the mean value of vitamin c was found to be 13.10 (mg/100 g) at n3p3 treatment. it was significantly higher than the rest of the treatments. ram et al found increased amount of ascorbic acid in cabbage by increasing fertilizer rate.14 the next value (11.64) was by n3p2 treatment. iron content in cabbage varied from 0.40 to 0.56 (mg/100 g). the highest value of iron were found from n2p2, n2p1 treatment which is closely followed by n2p3 treatment. the range of phosphorus accumulation in cabbage was 14.10 15.46 (mg %). the plot receiving n p fertilizer at the rate of 180 kg n + 90 kg p2o5/ha produced maximum concentration of phosphorus. the value is highly significant among the rest of treatment. calcium content varied from 24.21 to 27.09 (mg/100 g). the highest value at n2p1 treatment where as the lowest at control plot. the accumulation of sodium was found to vary 16.29 to 19.15 (mg/100 g). the highest accumulation of sodium was found from n2p1 treatment. potassium concentration ranged between 111.14 to 114.51 (mg/100 g), the lowest value being recorded from the control treatment. conclusion the finding of the study indicate that application of nitrogen phosphorus treatment improve the yield contributionary characters of cabbage leading to higher yield and better nutrition concern. so further research is needed in this direction with other varieties of cabbage to establish the present finding. acknowledgement the authors are grateful to the director, bcsir laboratories dhaka and the director, ifst, dhaka for their co-operation and help for providing laboratory facilities during the carry out of the work. references 1. anonymous. food and agriculture organization of united nation. rome production. year book. 41(1987) 176-177. 2. s. c. mallik, b. b. charya. effect of different levels of nitrogen and different spacing on growth and yield of cabbage. environment and ecology. 14(2) (1996) 304-306. 3. f. vice and j. polach. effect of principal plant nutrient on cabbage yield and quality. hort. abst. 50 (1980) 535. 4. n. h. peck, l. d. grunes, r. m. welch and g. e. mac denald. nutritional quality of vegetable crop as affected by phosphorus and zinc fertilizer. agron. j. 72(3) (1980) 528-534. 5. j. murkinski. effect of mineral fertilizer on some nutrient values indices of cabbage. soil and fertilizer. 37(8) (1973) 235. 6. officinal method of analysis of a.o.a.c. 1984 14th ed. virginia. u. s. a. haque, jahangir, haque, mondal, jahan and sarker 45 7. d. pearson. the chemical analysis of foods. (1976). churchill, livingstone edinburg. london. 8. a manual of laboratory techniques. indian council of medical research. (1971) hyderabad. india. 9. r. g. d. steel and j. h. torrie. principles and proceduces of statistics. mc. graw hill book co. inc. new york. (1960) 109 10. k. srinivas. growth yield of cabbage as spacing and fertilizer. singapore journal of primary industries. 10(1) (1982) 58-63. 11. f. m. humadi and h. a. a. hadi. effect of different source and rates of nitrogen and phosphorus fertilizer on the yield and quality of cabbage. journal of agric. and water resource plant production. 7(2) 1988.24959. 12. b. k. mohans and m. m. hossain. a role on effects of nitrogen and phosphorus on cabbage. orissa journal of horticulture. 26(1) (1998) 106-108. 13. t. tanaka and t. sato. growth and nutrient absorption characteristics of three commercial cabbage cultivar under varying nitrogen levels. japanese journal of soil science and plant nutrition. 68(5) (1997) 493-500. 14. k. ram and r. k. sharma. effect of nitrogen supply on growth yield and ascorbic acid content of cabbage. poon. agric. coll. j. 59 (122) (1969) 25-29. 46 yield and nutritional quality 41(1-2) 2006 file 2518 (4).qxd bangladesh j. sci. ind. res. 41(1-2), 33-40, 2006 introduction sunflower (helianthus annus l.) is relatively proved a good oil seed crop in bangladesh. it is a potential source of high quality edible oil, ranges second next to soybean as an oil crop in the world (fao).1 due to the increasing edible use of this oil crop, its production has been enhanced rapidly all over the world. sunflower's seed contains 48 % 52 % of good quality edible oil and 40 % 50 % of protein in meals. the oil cake from sunflower is also useful for cow and fish feeding. at present, sunflower is grown in many district of bangladesh without proper care. the average production of sunflower per unit area in our country is comparatively poor.2 the total cultivation area of this particular oil crop is limited. the progress in sunflower production is slow due to the lack of proper production technologies and management practices. among the several agro-techniques which can enhance the production of yield are the use of proper land preparation, irrigation, fertilizer application, proper plant spacing and other related factors are important. robinson et al., reddy et al. and villalobos et al. assessed that better seed yield of sunflower was greatly influenced by proper plant spacing.3-5 according to kharga et al., sharma et al. and vivck et al., nitrogen fertilizer has a positive effect on sunflower yield.6-8 several authors observed that the application of nitrogen fertilizer in conjugation with phosphorus fertilizer resulted in increased seed yield of sunflower.9-11 (chariara et al., singh et al. and ujjinaiah et al.). the information regarding the effect of response of nitrogen and phosphorus fertilizer and plant spacing on growth and yield contributing character of sunflower a. a. jahangir, r. k. mondal, katrun nada, r. sadia afroze and m. a. hakim bcsir laboratories, dhanmondi, dhaka-1205. bangladesh abstract the plant spacing of 20, 25 and 30 cm were used for the study. the doses of nitrogen and phosphorus were 80, 100, 120 and 45, 60, 75 kg/hectare respectively. the experiment was carried out in a randomized block design with three replications. 20 cm plant spacing produced the highest plot yield. maximum number of seeds per head and yield were produced by the application of 120 kg n + 75 kg p2o5 per hectare. in case of plant spacing x fertilizer interaction effect, 20 cm plant spacing with 120 kg n + 75 kg p2o5 per hectare treatment produced the highest head diameter and seed yield. plant spacing and nitrogen-phosphorus fertilizer on sunflower is mearge in our local climate condition. so, an attempt has been made to study the effect of plant spacing and nitrogen-phosphorus fertilizer for getting maximum yield of sunflower. materials and methods the investigation was made in the experimental field of bcsir (bangladesh council of scientific and industrial research) dhaka, during the winter season of 2002-2003. the soil of the experimental field was sandy clay loam having ph 5.8, 1.5 % organic matter and 0.04 % total nitrogen. the ph of moist soil was determined by using a corning glass electrode ph meter (model-7).12 organic matter content was calculated by multiplying the rules of organic carbon with conventional factor 1.74.13 the total nitrogen were determine microkjeldahl method as described by jakson.12 the unit plot size was 3m x 3m. the variety used for the study was kironi. the experiment was carried out in a randomized block design with three replications. the row spacing was 30 m. the plant spacing of 20, 25 and 30 cm were used for study. the nitrogen fertilizer doses under study were 80 kg n/ha (n1), 100 kg n/ha (n2), 120 kg n/ha (n3) and that of phosphorus 45 kg p2o5/ha (p1), 60 kg p2o5/ha (p2), 75 kg p2o5/ha (p3). the sources of nitrogen and phosphorus were urea and triple super phosphate respectively. at the time of land preparation, nitrogen and phosphorus were applied in the soil and nitrogen was applied to the field in two equal installments. all the intercultural operation were done in proper time. at the harvest time, 10 plants were selected at random from each plot to collect data on plant height and different yield contributing characters. yield was recorded from the plot. the collected data was statistically analyzed and mean values were adjudged by ducan's new multiple range test (steel and torrie).14 results and discussion the data on the effect plant spacing and nitrogen phosphorus fertilizer and their interaction have been presented in the table i, ii and iii, respectively. 34 response of nitrogen and phosphorus 41(1-2) 2006 plant spacing (cm) plant height (cm) table i. effect of plant spacing on the yield contributing character of sunflower. * means with the same letter are not different from one another at 5 % level of significance. 20 50.1c* 13.4 a 303.4 a 5.31 a 1.96 a 25 57.8 b 12.5 ab 290.3 b 5.34 a 1.68 b 30 60.8 a 12.0 b 289.4 b 5.33 a 1.56 b head diameter (cm) number of seed per head 100 seed weight (g) seed yield (t / ha) plant spacing effect the plant height of sunflower increased progressively with the increase of plant spacing. the widest plant spacing produced the highest plant height (60.8 cm) among other spacing. it was significantly different from other treatments. the results were in agreement with the result of bindra and kharwara who found increased plant height with increase of spacing.15 they observed the same spacing of 30 cm in the case of plant height of sunflower. the lowest highest (50.1 cm) plant was obtained from 20 cm plant spacing treatment. the plant grown with closer spacing produced maximum head diameter and the highest number of seeds than of those other spacing. the variation in plant spacing caused a significant difference in sunflower seed yield. the highest seed yield of 1.96 t/ha was recorded from 20 cm plant spacing. the highest and lowest yield were 1.96 t/ha and 1.65 t/ha respectively. the positive effect of closer plant spacing on seed yield as obtained in the present study agreed well to the findings of islam et al. and zaffaroni et al. where they found highest yield at closer plant spacing.16-17 rao et al. also reported the reduction in sunflower yield under higher plant density.18 the other two plant spacing treatment produced near about the same seed yield without any significant change. nitrogen phosphorous fertilizer effect in fertilizer treatment the maximum plant height (62.1 cm.) was obtained by n3p2. the second highest plant height was resulted from n3p3 treatment. this was closely jahangir, monodal, nada, afroze and hakim 35 nitrogenphosphorus fertilizer plant height (cm) table ii. effect of nitrogen_phosphorus fertilizer on the yield contributing charcter of sunflower. * means with the same letter are not different from one another at 5 % level of significance. control 49.6 e* 9.7 a 261.3 e 5.01 c 1.78 b n1p1 51.2 d 10.2 a 280.3 cd 5.39 abc 1.80 b n1p2 53.3 cd 10.3 a 271.6 de 5.38 abc 1.81 ab n1p3 58.5 ab 10.1 a 273.2 de 5.39 abc 1.82 ab n2p1 59.0 ab 12.4 ab 280.4 cd 5.60 ab 1.83 ab n2p2 58.2 ab 11.4 b 285.8 c 5.36 abc 1.97 ab n2p3 59.0 ab 12.4 ab 313.2 b 5.60 ab 1.86 ab n3p1 59.1 ab 12.7 a 314.8 b 5.61 ab 1.97 ab n3p2 62.1 a 13.3 a 337.5 a 5.73 a 2.01 ab n3p3 61.7 ab 13.2 a 339.8 a 5.73 a 2.08 a head diameter (cm) number of seed per head 100 seed weight (g) seed yield (t / ha) 36 response of nitrogen and phosphorus 41(1-2) 2006 plant spacing x n-p fertilizer treatment 20 cm 25 cm 30 cm table iii. interaction effect of plant spacing and fertilizer on the yield of sunflower. * means with the same letter are not different from one another at 5 % level of significance. control 53.3 c* 11.8 c 265.2 e 4.99 f 1.91 c n1 p1 54.5 bc 13.4 ab 329.1 ab 5.58 b 2.16 bc n1 p2 54.5 bc 13.5 b 339.1 a 5.78 b 2.16 bc n1 p3 54.3 bc 13.5 b 328.1 ab 5.67 b 2.38 ab n2 p1 54.4 bc 14.2 ab 317.7 b 5.67 b 2.32 ab n2 p2 60.7 abc 13.7 ab 329.6 ab 5.68 b 2.40 ab n2 p3 59.9 abc 14.3 ab 317.8 b 5.74 ab 2.30 ab n3 p1 60.2 abc 14.4 a 340.1 a 5.66 b 2.41 ab n3 p2 62.1 ab 14.4 a 340.9 a 5.67 b 2.50 a n3 p3 59.9 abc 14.5 a 329.4 ab 5.63 b 2.55 a n1 p1 60.1 abc 13.4 b 318.2 b 5.58 b 2.32 ab n1 p2 59.8 abc 13.5 b 318.1 b 5.57 b 2.30 ab n1 p3 54.4 bc 13.7 ab 317.9 b 5.63 b 2.17 bc n2 p1 59.9 abc 13.7 ab 328.0 ab 5.69 b 2.16 bc n2 p2 62.0 ab 13.5 b 329.5 ab 5.67 b 2.39 ab n2 p3 61.9 ab 13.8 ab 317.5 b 5.68 b 2.18 ab n3 p1 62.0 ab 13.7 ab 317.6 b 5.78 a 2.32 ab n3 p2 62.1 ab 14.2 ab 314.8 b 5.80 a 2.32 ab n3 p3 62.2 ab 14.2 ab 317.3 b 5.59 b 2.37 ab n1 p1 61.9 ab 11.8 c 281.1 cd 5.22 de 1.95 c n1 p2 62.2 ab 11.9 c 279.9 cd 5.07 ef 1.97 c n1 p3 60.1 abc 12.2 bc 279.9 cd 5.59 b 2.19 bc n2 p1 63.5 a 12.1 bc 277.4 cd 5.58 b 2.18 bc n2 p2 62.1 ab 13.3 b 271.7 de 5.67 b 2.15 bc n2 p3 59.9 abc 13.4 b 28.2 c 5.58 b 2.17 bc n3 p1 60.4 abc 13.3 b 287.1 c 5.39 cd 2.17 bc n3 p2 60.5 abc 13.7 ab 288.4 c 5.38 cd 2.15 bc n3 p3 60.0 abc 13.5 b 285.2 c 5.59 b 2.16 bc plant height (cm) head diameter (cm) number of seeds per head 100 seed weight (g) seed yield (t/ha) followed by n3p1. the minimum plant height was obtained from control treatment. the value was significantly lower than other treatments. the maximum head diameter was obtained from the plot receiving fertilizer at n3p2 treatment. the maximum number of seeds (339.8) per head was found with the application of n p fertilizer at the rate of n120p75 kg/ha. the results were in close conformity with those of nayak et al. who observed that the number of seeds per head in sunflower was increased progressively due to higher doses of nitrogen-phosphorus fertilizer application.19 100 seed weight of sunflower was found to vary from 5.01 5.73 g. the plot which received fertilizer at the rate 120 jahangir, monodal, nada, afroze and hakim 37 kg n + 75 kg p2o5 per hectare produced the highest seed yield of 2.08 t/ha. the results are in close agreement with the findings of tomar et al. but disagreed with tripathi et al. who found maximum seed yield of sunflower with lower dose of nitrogen (40 kg/ha) with conjugation of phosphorus.20-21 interaction effect in the interaction effect of the fertilizer and plant spacing, the highest plant was produced from the plot which was fertilized at the rate of n2p2 per hectare with plant spacing of 30 cm. the second highest plant height was obtained from n2p2 and n3p3 treatments space at 30 and 25 cm plant spacing respectively. the value of head diameter per plant ranged from 11.8 14.5 cm. the highest number of head diameter produced from n3p3 treatment with plant spacing of 20 cm. the variation in the number of seeds varied 38 response of nitrogen and phosphorus 41(1-2) 2006 jahangir, monodal, nada, afroze and hakim 39 from 340.9 265.2. maximum number of seed (340.9) per head was obtained in combination with n3p2 treatment with 20 cm plant spacing. the findings were in close conformity with the result of kene et al. who obtained the maximum number of seeds higher rate of n-p application with closer plant spacing.22 the next number of seeds per head of the sunflower plant was obtained by n3p1 and n1p3 treatment with mean number of 340.1 and 339.1, respectively with same plant spacing. the maximum plot yield of seed was produced from the plot receiving fertilizer at the rate of 120 kg n + 75 kg p2o5 per hectare. the superiority of closer plant spacing with increasing nitrogen-phosphorus application in sunflower yield has been reported by hedge et al. and sharma et al.23-24 the next higher seed yield was obtained from n3p2 treatment. conclusion the findings of the study indicate that the plant spacing and nitrogen-phosphorus fertilizer application treatment improved the yield contributing character efficiency of sunflower leading to higher seed yield. so, the further research is needed in this direction with other varieties of sunflower to establish the present findings. acknowledgement the authors are grateful to the director, bcsir laboratories, dhaka for his interest during the progress of the work. they do acknowledgement the assistance rendered by mohammedullah prodhan for the collection and preparation of plant sample. references 1. fao (food and agriculture organization) production year book. 37(70) (1985) 142-149. 2. m. a. khaleque and m. m. s. haque. prospect of sunflower cultivation as an oil seed crop in bangladesh. krishi katha. 52(9) (1993) 379-383. 3. r. g. robinson, j. h. ford, w. e. luesches. d. l. rabas, l. j. smith, d. d. warnes and j. v. wiersma. response of sunflower in plant population. agronomy. j. 72 (1980) 869-871. 4. s. g. reddy, v. marathi, d. g. rao and m. vanaja. effect of plant density and moisture stress on productivity of sunflower. annals agric. res. 18(4) (1997) 482-487. 5. f. t. villalobos,. v. o. sadres, a. soriano and e. fereres. planting density of dry matter partitioning and productivity of sunflower bybrides. field crops res. 36 (1984) 1-11. 6. k. v. g. kharga and b. g. nirwal. effects of inter and intra spacing and nitrogen levels of sunflower. agricultural science digest. 13(2) (1993) 115-116. 7. s. k. sharma and b. k. gaur. effect of level and method of nitrogen application on seed yield and quality of sunflower. ind. j. agron. 33(3) (1988) 330-331. 8. vivck and i. s. chakor. effect of nitrogen and irrigation on growth and yield of sunflower under mid-hill condition of himachal pradesh. ind. j. agron. 37(7) (1992) 500-502. 9. n. j. chariara, j. c. patel. d. d. malavia and n. m. baidha. effect of irrigation, nitrogen and phosphorus on the productivity of sunflower. ind. j. agron. 34(3) (1989) 399-401. 10. s. m. singh and r. k. pacheria. effect of varying row spacing, nitrogen and phosphorus levels on sunflower. ind. j. agron 26(10) (1981) 20-23. 11. u. s. ujjinaiah, n. r. shahthamallaiah and n. m. murali. effect of different row spacing and n and p2o5 fertilizer levels on growth, yield components and quality of seeds in sunflower. mysore j. agri. sci. 23(2) (1989) 146-150. 12. m. l. jacson. soil chemical analysis. (1962). constabel and co. ltd. london. 13. s. walksman. cybele and britannica. 4 (1936) 379. 14. r. g. d. steel and j. h. torrie. principles and procedures of statistics. mcgraw hill book co. inc. new york. (1960) 109. 15. a. bindra and p. c. kharware. response of sunflower to nitrogen application and spacing. ind. j. agron. 32(2) (1992) 283-284. 16. n. islam, m. a. kader and m. z. islam. response of hybrid and local varietities of sunflower to spacing and fertilizer levels. bang. j. agri sci. 27(1) (2000) 19-23. 17. e. zaffaroni and a. a. schneiter. sunflower production as influenced by plant type, plant population and row arrangement. agronomy j. 83(1) (1991) 113-118. 18. s. v. c. rao and g. saran, response of sunflower cultivars to planting density and nutrient application. ind. j. agron. 36(1) (1991) 95-98. 19. b. c. nayak and p. k. ghosh. response of sunflower varieties to n and p. orissa. j. agri. res. 3(3-4) (1990) 252-61. 20. h. p. s. tomar, h. p. singh and k. s. dadhwal. effectof irrigation, nitrogen and phosphorus on growth and yield of spring sunflower. ind. j. agron. 42(1) (1997) 169-172. 21. p. k. tripathi and g. s. kalra. effect of npk on maturity and yield of sunflower. ind. j. agron. 26(1) (1980) 66-70. 22. h. k. kene, v. r. thosar, r. b. ulemale and m. r. kale. response of sunflower to spacing and nitrogen, phophorus fertilizer. j. maharashtra agri. uni. 17(3) (1992) 433-35. 23. m. r. hedge and g. v. havanagi. effect of plant population and fertility levels on the growth and yield of sunflower. j. oil seeds res. 4 (1987) 185-192. 24. p. c. sharma, s. k. katyal and o. p. s. verma. growth and yield of sunflower varieties in relation to fertility level and plant population. ind. j. agron. 37(2) (1992) 285-289. 40 response of nitrogen and phosphorus 41(1-2) 2006 fille 2730(7).qxd influence of perceived job tension on stress reaction among hospital and university workers in nigeria bunmi omolayo* and bola mokuolu department of psychology, university of ado-ekiti, ekiti state, nigeria abstract the influence of perceived j ob tension on stress reaction among hospital and university workers in nigeria was the focus of this study. 160 participants randomly selected from hospital and university settings were used for the study. the age of the participants ranges between 25 years and 50 years with a mean age of 35. four hypotheses were tested and results shows that job stress is directly proportional to personal distress. also, no significant difference was found in the job related tension between hospital and university workers. result of this study shows that females have the same perception of work environment and they react to stress in the same manner. however, a significant difference exists in the level of stress between female and male university workers. key words : 1. job tension: the rigours and stress workers undergo on the job. 2. stress reaction: it the way workers react to stress on the job. this could be positive or negative. 3. stress: it is the unfavorable conditions that workers pass through in the course of discharging their job duties. 4. stressors: these are conditions that bring about stress on the job. bangladesh j. sci. ind. res. 43(3), 353-358, 2008 introduction stress is the result of an individual perception that does not have the resources to cope with a perceived situation from the past, present or future. it is caused by fear and the reaction to fear is to fight or flight. in basic terms, stress is an aspect of living that can be beneficial when it motivates, encourages, changes or inspires, but can be opposite when it does not. the stress which people complain about makes them to perform less well, and it is a feeling of tension or pressure experienced when they feel that the demands placed on them exceed the resources they have in order to meet the demands. stress has an unavoidable effect on the living and it is an especially complex phenomenon in *corresponding authour, email: droluomolayo@yahoo.com bcsir avaiable online at www.banglajol.info bangladesh journal of scientific and industrial research e-mail: bjsir07gmail.com 354 influence of perceived job tension 43(3) 2008 modern technological society. there is little doubt that an individual’s success or failure in controlling potentially stressful situations can have profound effect on his ability to function. people react to the same stressor differently, while some will cope with it, some other might not. the issue of perception of tension on the job and the resulting response or reaction to stress is a phenomenon that has been plaguing management of organizations and their workers both consciously and unconsciously. the underlying tension that exsits in most organizations as a result of differences in personality styles, battle for power and clashes with authority are some of the things that makes it harder and harder for some workers to get up and go to work each day. workers at times do not perform up to expectation or required standard in job situation because of their attitude to work that is perceived to be stressful and thereby reacting accordingly and also because they are stressed out by the nature of work or tasks being carried out. it should be noted that the state of equilibrium or disequilibrium of a person"s health will affect his/her productivity at work. barsade and wiesenfeld (1997) described stress related illness in a fashion similar to that of selye's 3 phase of general adaptation syndrome (gas). the alarm resistance is followed by counter attack during which the individuals defence mechanisms become active. if however the stress continues or the defence does not work, he will move to the third stage of exhaustion when adaptive mechanisms collapse. sauter, murphy and hurrel (1990) argued that individual differences in the response to stress are function of the person's cognitive appraisalhis/her evaluation through thought process of a potentially stressful event or situation. it is this process that determines how positive or negative his/her stress reaction will be, what emotions he./she will experience and what adaptive response he/she will make (sauter, hurrel, murphy and levi, 1997). the cognitive appraisal process is affected by emotional reactions. if the situation is evaluated as stressful, there may be negative emotional responses such as anxiety anger or depression. wyler, masuda and holmes (1971) found stronger physiological and more negative psychological responses when a stress task was seen as threatening than when participants viewed it as challenging. to be alive is to be constantly exposed to stressors. numerous studies in recent years bave focused on role conflict and ambiguity as major sources of stress at work and as useful concepts in understanding the relationship between job characteristics and workers behavior. khan, wolfe, quinn, snock and rosenths (1964) and house & rizzo, (1972) suggested that role conflict and ambiguity operate as intervening variables between original and personality variables. the magnitude is determined by organizational and task variables as well as by certain personalomolayo and mokuolu 355 ity predispositions. masuda and holmes (1976) found that both managers and workers who felt under pressure most reported that their supervisors always ruled with an iron hand and rarely tried out new ideas or allowed participation in decision-making. managers who were under stress also reported that their supervisors never allowed the persons under them to do their job in the way they thought best elisburg (1995) found that non-participation at work among a national representative sample of over 1,400 workers was the consistent and significant indicator of strain and job related stress. he further suggested that the long periods of activity, lack of opportunity for rest, strenuous and heavy work are considered as being conductive to the development of fatigue, hammer and tosi (1974) found that men who suffered from role ambiguity experience lower job satisfaction, higher job tension, greater futility and lower self confidence. stress indicators related to ambiguity are depressed mood and lower self-esteem. comparing men and women at similar occupational levels, hammer and tosi (1974) found that women reported more symptoms of stress than men, such as feeling depressed, having nightmares, feeling overwhelmed and experiencing stomach upset. materials and methods participants the participants for this study were randomly selected from two universities namely: university of ado-ekiti in ekiti state university of lagos in lagos state, all in nigeria (comprising of non-academic staff) and two hospitals namely: state specialist hospital, ado-ekiti in ekiti state and lagos state teaching hospital, ikeja in lagos state (comprising of administrative and nursing staff). a total number of 160 participants were used for this study (80 each from university and hospital settings comprising of 40 males and 40 females respectively). their age ranges between 25 years and 50 years. hypotheses 1. there will be a significant relationship between personal distress and job stress among the workers. 2. university workers will report a significant job related tension than hospital workers. 3. there will be a significant difference in the level of stress between female university workers and female hospital workers. 4. there will be a significant difference in the level of stress between male and female workers. instrument symptom distress checklist -90 (scl-90) developed by derogatis, lipman and covi (1973) was used to measure reactions to stress. erinosho (1996) provided the proper356 influence of perceived job tension 43(3) 2008 ties for nigerian samples with the reliability alpha co-efficient of. 77 for psychoticism and .90 for depression. job tension was measured by using job related tension (jt), a questionnaire consisting of 15 items developed by kahn,et al (1964) with a reliability co-efficient alpha of .39 and concurrent validity co-efficient of .46 design the ex-post facto design was adopted. the independent variable is the job tension while stress reaction serves as the dependent variable. statistical analysis the pearson correlation coefficient and the ttest for independent groups were used to test the hypotheses. results results of data collected are presented in table form below: authors' survey the result in table i shows a significant relationship between personal distress and job stress, thus confirming the first hypothesis. authors' survey result as indicated in the table above shows that no significant difference exist in the job related tension of university and hospital workers. hypothesis 2 is thereby rejected. authors' survey table iii above revealed that no significant difference is found in the level of stress between university workers and their counterparts in the hospital setting authors' survey table i. pearson correlation table showing the relationship between personal distress and job stress variable personal distress job stress x 48.56 46.49 df 158 r 2.28 p <.05 r (158)= 2.28, p<.05 table ii. independent t test table showing the difference in job related tension reported by university workers and hospital workers variable university workers hospital workers n 80 80 x 33.4 33.1 df 158 p >.05 t .079 t (158)= .079, p>.05 table iii. independent t -test showing the difference in the level of job stress between female university workers and hospital workers variable university workers hospital workers n 40 40 x 27.3 26.9 df 178 p >.05 t .0042 t (78)= .0042, p>.05 table iv. independent t -test showing the difference in the level of job stress between male and female workers variable male female n 80 80 x 30.6 36.2 df 78 p <.05 t 3.158 t (78)= 3.158; p<.05 omolayo and mokuolu 357 result as shown in table iv revealed that a significant difference exist in the job stress of male and female workers. discussion this study focused on the influence of perceived job tension on stress reaction among university and hospital workers in nigeria. from this study, it was found out that job stress is directly proportional to personal distress. this suggests that individuals react to job stressors differently because of the differences in their personality and coping style. this result corroborated the work of masuda and holmes (1976) who found that personality is one factor in the response to job stressors. they further stressed that only the anxious individual is most susceptible to the effect of stress. if a person has inadequate talent, inadequate training on the job, or lack of interest in the job, it will affect the level of job stress. it appears however that the single factor which is most likely to lead to job stress is a poor fit between the person and the job environment. this was revealed in the result of this study which shows no significant difference in the job related tension between hospital and university workers. this implies that it is not the type of job that causes job stress but many factors which could be personality factors, perception of stress, poor fit between the person and the job, among others. if the fit is poor, job stress is high. this also suggests that both hospital and university workers have equal chances of being exposed to job stress. this study also tries to find out if the work environment that female found themselves had any influence on their stress level. this was done by testing if there will be a significant difference in the level of stress between female hospital workers and female university workers, and the result shows no significant difference in their experience of stress. this suggests that most females have the same perception of work environment no matter the organization, and they react to stress in the same manner. this study also found that there is a significant difference in the level of job stress between female and male university workers. this shows that female university workers are prone to job stress more than their male counterparts. thus there is the tendency for the females to experience more symptoms of stress than males such as feeling depressed, having nightmares, feeling overwhelmed and experiencing stomach upset. research conducted by dohrenwend and dohrenwend (1979) on sex difference in psychopathology showed that women had consistent high rate of neurosis while men had consistent high rate of personality disorders caused by stressors. thus, women as spouses, mothers, care-givers and at the same time job holders are more susceptible to job stress. sex difference can be attributed to responsibilities and cultural value of our society. the female is not given much prerogatives as male and this results in accumulating tension and not having a way of releasing it, therefore showing in the job performance. conclusion the findings of this study revealed that job stress results from the interaction of individ358 influence of perceived job tension 43(3) 2008 ual and situational factors. sex is not a role determinant of job stress, but it can be a significant factor. the work, the family, personal life and the support network of friends and co-workers has influence on reactions to stress and perception of job tension. however, based on the findings of this study, it is recommended that management should ensure that the work load is in line with the worker's capabilities and abilities. management should equally design jobs to provide meaning, stimulation, and opportunities for workers to use their skills. the management should clearly define workers' roles and responsibilities, give workers opportunities to participate in decisions and actions affecting their jobs, improve communication network with the workers, provide opportunities for social interaction among workers, and establish work schedules that are compatible with demands and responsibilities outside the job. furthermore, measures such as absenteeism, illness, turnover rates, and performance problems should be examined to gauge the presence and scope of job stress. references barsade, s., wiesenfeld, b. (1997) attitudes in the american work place. new haven, ct: yale university of management. dohrenwend, b.s. dohrenwend, b.o. (1979) stressful life events: their nature and effects. new york: wiley pub. elisburg, d. (1995) workplace stress, legal documents, economic pressures and violence. in burton, j.t (ed.) workers compensations yearbook. horsham p.m: lrp publications, 1217-1222. hammer, m.c. tosi, h.l. (1974) relationship of role conflict and role ambiguity to job involvement measures. new york: prentice hall inc., 203-210. house, r.j. rizzo, j.r. (1972) role conflict and ambiguity as critical variable in a model of organizational behaviour & human performance. new york: prentice hall inc., 407-505. kahn, r.l., wolfe d.m., quinn, r.p., snock, j.c., rosenths, r.a., (1964) organizational stress studies in role conflict and ambiguity. new york: wiley pub. masuda, m., holmes, t.h. (1976) the social readjustment rating scale. a crosscultural study of japanese and americans. journal of pscyhosomaticresearch 11: 227-237. sauter, s.l., murphy, l.r., hurrel, j.j., jr. (1990) prevention of work related disorders. american psychologist, 45(10): 11461158. suater, s., hurrel. j., murphy, l., levi l. (1997) psychosocial and organizational factors. in stellman, j. (ed) encyclopedia of occupational health and safety (vol 1). switerland: international labour office, 1: -34, 77. wyler, a.r., masuda, m., holmes, t.h. (1971) magnitude of life events and seriousness of illness. journal of psychosomatic medicine 33: 115-122 received : january, 09, 2008; accepted : march, 02, 2008. macap fill 3009(20):macap fill 3009(20).qxd.qxd polymetallic complexes part lxxxxi dimeric and monomeric complexes of coii, niii, cuii, znii, cdii and hgii with n o-o n and n o donor bis-bidentate and bi-dentate azodye ligands. bi. b. mahapatra* and a. k. sarangi p.g. department of chemistry, g.m. autonomous college, sambalpur-768004, orissa, india. abstract bis-bidentate azodye, 4,4 / -bis (4 / -dihydroxyquinolineazo)3,3 / -dimethoxydibenzene having n o-o n donors and bidentate azodye (4 -hyoxyquinolineazo)4 / -methoxybenzene having n o donors form dimeric and monomeric complexes of the type [m2lcl2(h2o)6], [m / 2lcl2(h2o)2], [ml / 2(h2o)2] and [m / l / 2] where m = co ii, niii, cuii; m / = znii, cdii, hgii . the complexes of the first and third categories are found to be six-coordinated with an octahedral and distorted octahedral configuration and the complexes of second and fourth type are four-coordinated with a tetrahedral geometry around the metal ions. the complexes have been characterised based upon analytical, conductance, magnetic susceptibility, i.r., electronic spectra, n.m.r., e.s.r. and x-ray diffraction data. the unit cell parameters like a, b, c, α, ß, γ and v (volume) have been calculated from the 2θ values. the unit cell geometry of the complex [co2lcl2(h2o)6] is found to be monoclinic. key words: polymetallic complexes, azodye complexes, multidentate ligands. introduction the pharmacological and chemotherapeutic activity of azodye is well recognised (goodman and gilman, 1970). synthetic chemists have been inspired to prepare broad spectrum drugs from the azodyes of aromatic and heterocyclic amines. some of the azodyes are used for dyeing food stuffs, preserving food grains and as redox indicator (isa et al.,). potentiometric and spectrophotometric studies of metal complexes with azodye ligands have been reported. oxine and its derivatives possess antibacterial and amoebicidal properties (porter et al., 1968). we have earlier reported the synthesis of a number of multidonor azodyes and their polymeric metal complexes (mahapatra et al., 1987). the present work reports the synthesis of one bis-bidentate and one bidentate azodye ligands containing these two potentional biologically active moieties and their twelve dinuclear and mononuclear metal complexes with coii, niii, cuii, znii, cdii and hgii ions. bangladesh j. sci. ind. res. 46(2), 259-264, 2011 bcsir available online at www.banglajol.info bangladesh journal of scientific and industrial research e-mail: bjsir07@gmail.com * corresponding author: e-mail: mahapatra.bipin@yahoo.com, ashishsbp_2008@yahoo.com [fig. 1] [fig. 2] materials and methods o-dianisidine, p-anisidine and 8-hydroxyquinoline are b.d.h. or e. merck grade. metal, nitrogen and chloride contents were estimated by standard methods. conductivity measurement in dmf was made using toshniwal cl 01-06 conductivity bridge. magnetic moment was measured by gouy method at room temperature. i.r. spectra (kbr) were recorded on an ifs 66u spectrophotometer, electronic spectra (10-2m in dmf) using hilger-watt uvispeck spectrophotometer, e.s.r. spectrum on a e4spectrometer and n.m.r. spectra on a jeol gsx 400 with cdcl3 as solvent and relative to tetramethylsilane and x-ray diffraction (powder pattern) of the complex [co2lcl2 (h2o)6] was recorded on a phillip pw 113/00 diffractometer. preparation of 4,4 / -bis (4 / -hydroxyquinolineazo)3,3 / dimethoxydibenzene o-dianisidine (0.01 mol, 2.44 g) was dissolved in dil. hcl (10 ml) and was kept in ice cold water (0-5oc). sodium nitrite solution was then added to it slowly with stirring when the corresponding diazonium chloride was formed. to the 8-hydroxyquinoline (oxime) (0.02 mol, 3.18 g) solution in ethanol, sodium hydroxide solution was added and the resulting solution was then poured in to the above diazonium chloride slowly with stirring when a red coloured azodye (lh2) separated out. it was then filtered, washed with water and dried in vacuo. preparation of (4-hyoxyquinolineazo)4 / -methoxybenzene this azodye was prepared in a similar method by the coupling reaction of p-anisidine (0.01 mol, 1.23 g) with alkaline solution of 8-hydroxyquinoline (oxine) (0.01 mol, 1.59 g). the reddish yellow azodye separated out immediately was then filtered, washed with water and dried in vacuo. preparation of the complexes the metal chlorides in ethanol were mixed together with ethanolic solution of the ligands and the resulting solutions were refluxed at ~50 o c for an hour on a heating mantle. the solution was then cooled down to room temperature and the ph was raised to ~7 by adding conc. ammonia drop by drop with stirring. the solid complexes thus separated were then washed with ethanol, followed by ether and dried in vacuum. result and discussions the analytical data (table i) indicate that the metal complexes have the compositions [m2lcl2(h2o)6] , [m | 2lcl2 (h2o)2], [ml | 2 (h2o)2] and [m |l| 2]; where m = co ii , niii, 260 polymetallic complexes part 46(2) 2011 compound colour % metal found % nitrogen found % chlorine found μ eff b.m. (calculated) (calculated) (calculated) lh2 red 14.87 (15.10) llh reddish yellow 14.73 (15.04) [co2lcl2 (h2o)6] violet 13.58 (13.76) 9.65 (9.88) 8.12 (8.35) 5.1 [coll2(h2o)2] red 8.83 (9.05) 12.71 (12.90) 5.0 [ni2lcl2 (h2o)6] reddish brown 13.52 (13.76) 9.79 (9.88) 8.21 (8.35) 3.1 [nill2(h2o)2] reddish brown 8.88 (9.01) 12.73 (12.90) 3.0 [cu2lcl2 (h2o)6] light brown 14.4 (14.76) 9.54 (9.76) 8.13 (8.25) 1.8 [cull2(h2o)2] light brown 9.43 (9.69) 12.67 (12.81) 1.8 [zn2lcl2 (h2o)2] brown 16.19 (16.42) 10.46 (10.61) 8.75 (8.96) [znl l2] brown 10.28 (10.52) 13.23 (13.51) [cd2lcl2 (h2o)2] brown 25.13 (25.31) 9.27 (9.49) 7.84 (8.02) [cdll2] dark brown 16.55 (16.76) 12.36 (12.57) [hg2lcl2 (h2o)2] reddish brown 37.41 (37.75) 7.72 (7.90) 6.35 (6.68) [hgll2] reddish brown 26.38 (26.51) 10.96 (11.10) table i: analytical and physical data of the complexes mahapatra and sarangi 261 cuii ; m = znii, cdii, hgii ; lh2 = c32 h24 o 4n6 (fig. 1) (calcd. (%) c, 69.06; h, 4.35; n, 15.1; found (%) c, 69.02; h, 4.31; n, 14.87); l|h4= c16 h13 o2n3 (fig. 2) (calcd. (%) c, 68.81; h, 4.69; n, 15.04; found (%) c, 68.63; h, 4.54; n, 14.73) . all the six complexes with ligand (lh2) are powdery in nature having high melting points and are insoluble in common organic solvents but the six complexes with ligand (l|h) are crystalline, soluble in organic solvents and have low melting points. the non-electrolytic nature of all the twelve complexes are correlated with the low m values (4.36.5 ω-1 cm2 mol-1). in the ir spectra of the ligands, (table ii) one broad band appears at 3431(lh2) and the other at 3411 (l ih) which might be due to o-h…n intramolecular hydrogen bonding. these bands are non-existent in the metal complexes, indicating the bonding of the phenolic -oh groups to the metal ions (mishra and keshari, 1981). the v (-n=n-) band observed at 1595 cm-1(lh2) and 1600 cm -1(lih) remain unaffected in the metal chelates showing non-coordination of the azo nitrogen atoms to the metal atoms (king and bisnette, 1966). the bands observed at 1168 cm-1 (lh2) and 1152 cm -1 (lih) in the ligands are attributable to v (c-o) vibration and the bathochromic shift of ~ 40 cm-1 in the metal complexes indicates the bonding of oxine oxygen to the metal atom. in the spectra of the ligands, an intense band is observed at 1400 cm-1(lh2) and at 1403 cm -1(lih) due to c---------n vibration of the oxinate (magee and gorden) group. in the metal complexes this band occurs at ~1320 cm-1. the shift of this band to lower frequency regions show considerably lower double bond character of the c---------n bond due to involvement of the ring nitrogen on complexation. one broad band appears in the region 3400-3412 cm-1 for lh2 complexes and the other peaks at ~837-842 cm-1 for coii , niii and cuii , lih complexes which are assignable to -oh stretching and rocking vibrations respectively indicating the presence of coordinated water molecules in the complexes (nakamoto, 1978 and gamo, 1961) .the evidence of bonding of oxygen and nitrogen atoms in oxine is further substantiated by the appearance (ferraro, 1971) of bands at ~603 cm-1and ~516 cm-1 assignable to v (m-o) and v (m-n) vibrations respectively. the cobalt(ii), nickel(ii) and copper(ii) complexes exhibit magnetic moments at ~ 5.1, 3.1 and 1.8 b.m. indicating the presence of three, two and one unpaired electron respectively (cotton and wilkinson, 1988) . three bands appear at 9100(9090), 18315(18280) and 21560(21470) cm-1 in the electronic spectra of coii complexes, which could be attributed to 4t1g (f) �4t2g (f) (v1),� 4a2g (f) (v2) and�4t1g (p) (v3) transitions respectively. the value of the spectral parameters like dq = 921.5(919) cm-1 , b = 838.3 (832.0) cm-1 , β35 = 0.863 (0.856) cm -1 , v 2/v 1 = 2.01(2.01) and σ = 15.87% (16.82%) of co ii complexes are suggestive of an octahedral stereochemistry around the metal ion (lever 1968). in the electronic spectra of niii complexes, four bands appear at 10250(10282), 17122(17315), 24980(24992) and 32240(31355) cm-1 which may be assigned to 3a2g(f)� 3t2g(f) (v1), � 3t1g(f) (v2), �3t1g(p) (v3) and ct transition respectively. spectral parameters like dq = 1025.0 (1028.2) cm-1, b = 756.80 (764.06) cm-1, β35 = 0.726 (0.773) cm -1, v2/ v1 = 1.67(1.68) and σ = 37.74% (36.42%) indicates the octahedral symmetry. in the case of the copper (ii) complexes one broad asymmetry band appears at 12750-12980 cm-1characteristic of distorted octahedral stereochemistry with d4h symmetry (procter et al., 1968). the broadness of the bands might be due to jahn-teller distortion. compounds v(c-o) v( c-------n ) v(m-o) v(m-n) lh2 1168 1400 llh 1152 1403 [co2lcl2 (h2o)6] 1130 1321 603 516 [coll 2(h2o)2] 1112 1313 603 517 [ni2lcl2 (h2o)6] 1130 1321 602 515 [nill2(h2o)2] 1115 1315 602 516 [cu2lcl2 (h2o)6] 1132 1320 603 515 [cull2(h2o)2] 1112 1313 603 517 [zn2lcl2 (h2o)2] 1130 1322 603 516 [znll2] 1115 1315 603 517 [cd2lcl2 (h2o)2] 1130 1320 602 515 [cdll2] 1110 1313 602 515 [hg2lcl2 (h2o)2] 1132 1321 601 516 [hgll2] 1115 1315 602 516 table ii: infrared spectra of the ligands and the complexes 262 polymetallic complexes part 46(2) 2011 in the e.s.r. spectra of the copper complexes [cu2lcl2 (h2o)6] and [cu2li2(h2o)2] were recorded at q-band and the 'gav' values were found to be 2.05554 and 2.05848 respectively by kneubuhl's method (kneubuhl 1960). these spectra are found to be isotropic, consisting of a single line which is a characteristic of complexes having regular octahedral geometry. this type of spectrum may also result due to regular octahedral stereochemistry undergoing a dynamic or pseudo-rotational type of jahn-teller distortion. the 1h nmr spectra of the ligands lh2 and l 1h were recorded in cdcl3 solvent with tms as internal standard. the complex pattern observed at δ 6.797 -8.198 (lh2) and δ 6.983 8.186 (l1h) corresponds to 16 and 8 aromatic protons each. the sharp singlet peak observed at δ 4.019 (lh2) and δ 3.972 (l1h) corresponds to six and three methoxy (-och3) protons respectively. the phenolic protons could not be detected as it was beyond the range of the instrument. the xrd study (powder pattern) of the complex [co2lcl2 (h2o)6] was shown in graph-1. the unit cell parameters a, b, c, α, β, γ and v (volume) have been calculated from the 2θ values. the density (d) of the complex was determined by floatation method. the number of formula units (n) per unit cell is calculated from the relation n = dnv / m where d = density of the compound, n = avogadro's number, v = volume of the unit cell and m = molecular weight of the compound. the value of 'n' is found to be 1.0 for the complex corresponding to the volume of the unit cell 414.95 å . the unit cell is found to be 'monoclinic', based upon the unit cell parameters (puri et al, 1993) (table iii). the znii, cdii and hgii complexes are suggested to be fourcoordinated having tetrahedral geometry based on analytical, ir and conductance data. conclusion the azodye lh2 having o n-n o donor atoms behaves as a bis-bidentate ligand and the azodye l/h behaves as a bidentate ligand having o n donor atoms. the former ligand binds two metal atoms on either side forming dimeric complexes whereas the latter ligand forms monomeric complexes with the metal ions. both the azodyes coordinate to the metal atoms through the quinolyl oxygen and nitrogen atoms. graph-1: xrd graph for [co2lcl2 (h2o) 6] complex mahapatra and sarangi 263 acknowledgement the authors wish to thank sri l.d. pradhan, scientist, r.r.l. bhubaneswar (orissa) for his kind help in recording and analysing the xrd spectrum of the coii complex. references cotton f. a. and wilkinson p. g. (1988). advanced inorganic chemistry. 5th ed. (john wiley & sons, ny, usa). dessouki h. a., issa r. m., ghoneium a. k. and moustafa m. m. (1984). co(ii), ni(ii) and cu(ii) complexes of some phenylazosalisylaldehyde derivatives. j. indian chem. soc; 61: 286-289. ferraro j. r. (1971). low frequency vibration of inorganic and co-ordination compound, (plenum press, ny, usa). gamo i. (1961). infrared spectra of water of crystallization in some inorganic chlorides and sulfates. bull. chem. soc., jpn , 34: 760-764. goodman l. s. and gilman a. (1970). the pharmacological basis of therapeutics, 4th ed. (macmillan, ny, usa). king r. b. and bisnette m. b. (1966). organonitrogen derivatives of metals carbonyls. ii. arylazo derivatives of molybdenum inorg. chem , 5: 300-306. kneubuhl f. k. (1960). approximations in calculation of epr parameters. j. chem. phys, 33: 1074-1078. lever a. b. p. (1968). inorganic electronic spectroscopy (elsevier, amsterdam, uk). magee, r. and gordan, l. (1963). the infrastructure of chelate compounds-iii1: a study of some tervalent metal chelate compounds of 8hydroxyquinoline in the region 5000-250 cm-1. talanta, 10: 967-970. mahapatra b. b. and patel b. k. (1987). pollymetallic complexes: part xi. cobalt(ii), nickel(ii), cupper(ii), manganese(ii), zinc(ii), cadmium(ii) and mercury(ii), complexes with o n-n o tetradentate schiff base, n,n / bis (benzoin)benzidine. transition met. chem, 12: 49-51. mohapatra b. b. and das d. k. (1987). pollymetallic complexes: part x. cobalt(ii), nickel(ii), c u p p e r ( i i ) , zinc(ii), cadmium(ii) and mercury(ii), complexes with a chelating azodye ligand, 5-(ohydroxyphenyldiazo)-acetoacetanilide. acta chim, hung, 24(3): 387390. mahapatra b. b. and saraf s. k. (2003). polymetallic complexes. part-lxxxii. bis-bidentate and bis-tridentate azodye dimeric complexes of coii, niii, cuii, znii, cdii and hgii. j. indian chem. soc, 80: 696-699. compound [co2lcl2 (h2o)6] 10.897,12.991,14.935, 16.430,18.975,21.964, 28.993,32.300,39.313, 39.462,39.521,39.612, 50.137,53.670,53.820, 60.101,60.998,61.148, 68.626,73.411,73.860, 78.197,83.881,84.030, 85.675,88.218,89.265 a = 11.843 å b = 4.925 å c = 7.127 å α = 90.00 o β = 93.425 o γ = 90.00 o v = 414.95 cc 2.04 1.0 monoclinic 2θ -values in degrees unit cell parameters density, (g/cm3) n possible crystal system table iii: x-ray diffraction data of the complex 264 polymetallic complexes part 46(2) 2011 mishra l. k. and keshari b. n. (1981). thiohydrazides as complexing agents: part icomplexes of ni(ii), co(ii & iii), cu(ii), zn(ii), cd(ii), pd(ii) & hg(ii) with o-hydroxyphenylthiohydrazide. indian j. chem, secta, 28: 883-887. nakamoto k. (1978). infrared and raman spectra of inorganic and coordination compounds, (john wiley, ny, usa). puri b. r., sharma l. r. and kalia k. l. (1993). principle of inorganic chemistry, (lal, s. nagin chand & co, india). porter t. h., skelton f. s. and folkers k. (1972). coenzyme q. 139. synthesis of new alkylaminoand alkylaminomethyl-5,8-quinolinequinones as inhibitors of coenzyme q and as antimalarials. j. med. chem, 15 (1): 34-36. procter i. m., hathaway b. j. and nicholls p. (1968) the electronic properties and stereochemistry of the copper(ii) ion. part i. bis(ethylenediamine)copper(ii)complexes. j. chem. soc., (a): 1678-1684. received : october 19, 2009; accepted : october 19, 2010 file 2596 (7).qxd bangladesh j. sci. ind. res. 41(3-4), 171-180, 2006 introduction curie temperature is the temperature when the energy of the thermal motion of the atoms is sufficient to overcome the interaction forces between the atomic moments. at this temperature a ferromagnetic substances changes over to paramagnetic substances. this temperature is also a measure of exchange forces in a ferromagnetics. near curie temperature, tc, some of the intrinsic parameter such as the magnetization, the susceptibility, thermal and electrical conductivity are seen to behave differently than predicted by classical molecular field theory. in general ferrite shows an increasing value of permeability with increasing temperature, until they approach their curie points when the permeability falls sharply. this happens due to magnetic transition from the ferrimagnetic phase to the paramagnetic phase. the temperature variation of resistivity of magnetic materials shows similar irregularities at studies on anomalous behaviour at curie point, tc of some classes of mixed ferrites m. tofazzal hossain,a suravi islam,a mokbul hossain mondala and a. h. khanb abcsir laboratories, dhaka and department of physics, bjahangirnagar university, savar, dhaka. abstract a comparative studies on anomalous behaviour at curie point between clay additives mn-zn ferrites and other mixed ferrites such as mn-zn, ni-zn, mg-mn and ni-mg have been carried out in this investigation. the changes in tc on compositions, additives and manufacturing processes of such soft mixed ferrites have been determined from the temperature dependent dc resistivity data and the log ρ vs. (1/1000t) graphs. it is observed that the curie temperature is dependent on compositions, additives, manufacturing process and microstructure. definite changes of curie points of clay additives mn-zn ferrites with other ferrites were observed. both the mn-zn ferrites and clay additives mn-zn ferrites showed some changes in their tc behavior. the tc value of mn-zn ferrites with clay additives decreases with increasing additives. in the case of clay substituted mn-zn ferrites the decrease of curie point can be understood by a decrease of the number of fe3+ magnetic ions substituted by nonmagnetic al3+ ions on o sites of the system. magnetic transition point. the magnetic transition point can often be clearly observed in the anomalous temperature variation of transport properties of magnetic material near tc. the magnetic transition point tc of pure iron was studied by lunchbury.1 he studied temperature dependent electrical resistivity ρ and observed tc around 770o c. the expected linear relationship between lnρ and 1/t has often been found for ferrite materials accompanied by a change in activation energy near the curie temperature. it has been observed that in mixed ferrites, where the divalent metal ions consist of some magnetic ions such as ni, co, fe and some nonmagnetic ions such as zn, ca, cu interesting phenomenon occurs. the diamagnetic zn2+ ions content of the mixed zn2+ ferrite has a marked effect on the curie temperature. the curie temperature decreases continuously as the zinc content increased.2 this was experimentally found out by forestier in zn2+ ions substituted mixed ferrite.3 on the other hand, the addition of diamagnetic zn2+ content increase the room temperature permeability of mn ferrite from 250 to 1000 and ni ferrite from 10 to 700. so, mixed ferrite of appropriate composition can yield convenient tc values for operating at high permeability.4,5 the study of the variation of tc values with the content of a nonmagnetic substance like zn2+ ions is clearly of importance. the aim of the present experiment is to investigate the value of tc of some mixed ferrites like mn-zn, ni-zn, mg-mn and ni-mg ferrites with varying the compositions, additives and manufacturing process and to observe the resulting change in their transition temperature, tc. besides, a comparative study of curie points between mn-zn ferrites and clay additive mn-zn ferrites have been made in this investigation. materials and methods in the present investigation, eight series of samples with various compositions and additives were prepared in our laboratory by using a ceramic method. the samples were classified into eight groups such as a, b, c, d, e, f and g. group a-e are mn-zn ferrites with different compositions and sintering temperature, group f is ni-zn ferrites, group g is mg-mn ferrites and group h is ni-mg ferrites. the main emphasis of this study has been given on group e in which clay has been employed as an additive. more details about the preparation of the ferrite from oxides are given by snelling and ahsanullah.4,5 there are some methods available to determine curie temperature, tc. the curie temperature is usually determined from magnetization or magnetic susceptibility data. the tc can also be determined by different techniques; which include specific heat, thermal expansion and electrical resistivity as a function of temperature. in our present experiment the curie temperature measurement involved measuring the resistivity ρ, at 172 studies on anomalous behaviour 41(3-4) 2006 varing temperature. the same method has been treated by m. a. hossain, s. r. swant and r. n. patil and v. r. kulkarni et.al.6-9 to characterize the clay additive samples, the x-ray powder pattern were recorded on a phillips x-ray diffractometer using cu kα radiation. results and discussion structural characterization figs. 1.1 to 1.3 show the x-ray diffraction patterns for clay additive mn-zn ferrites (group e samples). the patterns were analyzed by phillips x-ray diffractometer and confirm formation of cubic system with space group fd3m. the structural parameters are shown in table i. composition dependent curie temperature, tc values of mn-zn, mg-mn and ni-mg ferrites to determine tc the temperature dependent dc resistivity data plotted as lnρ vs (1000/t) have been used. in group a, the zn2+ ions content is constant and the weight % of the value of fe2o3 and mno are changed simultaneously. the values of tc on compositions of mn-zn ferrites (a-group) are shown in fig. 2.1 hossain, islam, mondal and khan 173 fig. 1.1. x-ray diffraction patterns for rc 174 studies on anomalous behaviour 41(3-4) 2006 fig. 1.2. x-ray diffraction patterns for bc fig. 1.3. x-ray diffraction pattern for yc. it is seen from fig. 2.1 that the curie temperature increases with the increase of weight % of fe2o3. it is also observed that the slight variation in the composition ratio of fe2o3 and mno have a remarkable effect on tc. it is also well known that the tc values are dependent on the exchange interaction of magnetic ions of ferrites between octahedral and tetrahedral sites. in the present study, the increase of tc values in the case of iron rich mn-zn ferrites is due to the increase of exchange interaction of ab or bb between octahedral and tetrahedral sites. in this study we have also investigated the composition dependent anomalous behaviour that is tc of ni-zn ferrites. in ni-zn ferrites the weight % of fe2o3 remains constant and the ratio of the value of the zno and nio are changed simultaneously. the curie temperature of this system is shown in fig. 2.2. it is seen from the figure that the curie temperature decreases with the increase of zno or increases with increase of nio. this type of behaviour has also been reported by forestier in zn2+ ions substituted ni-zn ferrites.3 as the zno in ni-zn ferrite increases exchange interaction of ab and bb between octahedral and tetrahedral sites decreases and thus decreases tc. reverse is in the case of nio addition. in mg-mn and ni-mg we have seen that the mg ions have remarkable effect on curie temperature as in figs. 2.3 and 2.4. it is seen from fig. 2.3 that the curie temperature hossain, islam, mondal and khan 175 samples structure space group lattice parameter unit ao density unit gm/cc no of formula unit with unit cell e1 cubic fd 3m 8.5136 5.010 8 e2 cubic fd 3m 8.4975 5.084 8 e3 cubic fd 3m 8.4794 5.162 8 table i. the crystal system, space group and values of lattice parameters, density, number of formula units of clay additive mn-zn ferrites. fig. 2.1. composition dependent tc in mn-zn ferrites (group a samples) fig. 2.2. composition dependent tc in ni-zn ferrites decreases with the increase of mg ions. the decrease of curie point with increase of mg ions is due to the fact that mg occupies osites, which weaken the ab interaction and hence decreases tc. in case of ni-mg ferrite addition of nio enhances ab and bb interaction resulting increased tc values which is evident in fig. 2.4. effect of sintering temperature on curie temperature, tc the objective of the study of group c was to observe and gather a general knowledge about the tc values of mn-zn ferrites with different sintering temperature. this group of mn-zn ferrites was prepared by sintering at 1273 k, 1373 k, 1473 k and 1573 k calculated values of curie temperature, tc of mn-zn ferrites sintered at 1273 k, 1373 k, 1473 k and 1573 k are shown in fig. 2.5 against sintering temperature. it is evident from fig. 2.5 that the tc increases with increasing sintering temperature from 1000 to 1300o c. from the experimental findings it is observed that sintering temperature of the mn-zn ferrite samples bore some relations with their tc. the tc of the experimental samples increases with the increase of the sintering temperature. because at higher sintering temperature, the density and average grain of the magnetic ions of ferrites are increased. the magnetic ions of mn-zn ferrites not only increases magnetic moments but also increases the tc on sintering temperature. 176 studies on anomalous behaviour 41(3-4) 2006 fig. 2.3. composition dependent tc in mg-mnferrites fig. 2.4. composition dependent tc on ni-mg ferrite system fig. 2.5. variation of tc on sintering temperature (group c samples) --> c ur ie te m pe ra tu re ,t c( k) hossain, islam, mondal and khan 177 effects of zn-variables on tc values in mn-zn ferrite the purpose of the study of group b samples was to observe the change in curie temperature due to change of non magnetic zn2+ ion in mn-zn ferrite. in this investigation we have studied and have compared the tc of some mixed ferrites which containing zn2+ ions (sample no. b2, b3 and b4) with other ferrite that does not contain zn2+ ions (sample no b1). it is observed that ferrite samples b1 which does not contain zn2+ ions has higher tc value than the other samples of this group. but if we gradually increase the zn2+ ions in mixed ferrite samples b2 to b4, tc value decreases. this result is in good agreement with the result of j. roberts and galleo.2,10 this type of behavior was experimentally found out by forester and robert.3,2 the decrease of curie point is due to the tetrahedral site preference of the zn2+ ions. zn2+ ions always prefer a sites i.e. tetrahedral site. the exchange integral for a site i.e. jaa is almost negligible. so substitution of zn2+ ions only weaken the ab interaction effectively. if the number of substituted ions are not too high the overall ferrimagnetic arrangement is not destroyed even though some loosely bound spins may become canted or destroyed, at temperature t< tc. for large substitution, the ab interaction became comparable to or even weaker than bb interaction. in this way the collinear ferrimagnetic arrangement often changes to canted one. owing to this reduced a-b exchange interaction with increasing zn2+ ion content the curie temperature will drop. so the study of the variation of tc values with the content of nonmagnetic substance like zn2+ ions is clearly important. effects of replacement of zno by al2o3, cdo and cao we have already seen in group b that non magnetic material like zn2+ ions in mixed ferrites play an important role in relation to their tc. it was found that with gradual increase of zn2+ content in mixed ferrites the curie temperature decreases. behavior of the substitution of non magnetic materials like al, cd, ca, etc. in mn-zn ferrites have been also studied in the mixed ferrites (group d samples) to observe the similar effect. the calculated values of tc on substituted ions are shown in fig. 2.7. from the experimental finding it was found that molecular weight of different samples bore some relations with fig. 2.6. composition dependent tc in mn-zn ferrite (group b samples) 178 studies on anomalous behaviour 41(3-4) 2006 their curie temperature. the curie temperature decreases with the increase of molecular weight. effects of clay additives in mn-zn ferrite on tc in this investigation three types of clay additive mn-zn ferrites have been studied. these types of clay additives are denoted by rc, bc and yc and found in bijoypur and savar region of bangladesh. the main cations of clay material are si, al, mn and fe. the composition variations of tc values of clay adittives of ferrite are shown in fig. 2.8. it is evident, as in fig. 2.8, that sample yc has the highest tc value. the observed variation of tc values can be explained on the basis of aa, ab and bb interactions. in clay additive mn-zn ferrites, the cations are fe, mn and si, which contribute to tc values. it is well known that the cation fe is magnetic and occupy both the tetrahedral and octahedral sites. in the fig. 2.7. variation of tc on various substitute ions (group d samples) table ii. composition variation of tc values of clay additive ferrites 480 490 500 510 520 530 280 305 330 355 380 molecular weight fig. 2.8. variation of tc on fe content in various additives mn-zn ferrites. 480 490 500 510 520 530 280 305 330 355 380 molecular weight sl. no composition of ferrites cations compound formula concentration % curie temperature tc (k) 1. rc (red clay substitute mn -zn ferrite) si mn fe sio mno fe2o3 25.79 20.50 33.70 561 2. bc (black clay substitute mn -zn ferrite) si mn fe sio mno fe2o3 27.75 20.37 35.01 571 3. yc (yellow clay substitute mn -zn ferrite) si mn fe sio mno fe2o3 31.80 18.38 44.50 577 hossain, islam, mondal and khan 179 present study the increase of tc value in the case of fe rich clay additive mn-zn sample is due to the increase of exchange interaction of ab and bb between octahedral and tetrahedral sites. conclusions the curie temperature tc, of the various ferrites is strongly dependent on composition, sintering temperature and various additives. it is seen that the slight variation of the composition i.e ratio of major constituents have a remarkable effect on tc. it is also observed that the tc values depend on the exchange interaction of magnetic ions of ferrites between octahedral and tetrahedral sites and the observed variation may be explained on the basis of aa, ba or bb interactions of various cations and their site location between octahedral and tetrahedral sites. it is evident that sintering temperature of the mn-zn ferrite sample bears some relations with their curie temperature. at higher sintering temperature the density and average grain of the magnetic ions of ferrites are increased and the magnetic moments are increased. this enhances the magnetic interaction and hence increases tc values. in clay additive mn-zn ferrites, the cations are fe, mn and si which contribute to tc values. it is well known that the cations fe are magnetic and occupy both the tetrahedral and octahedral sites. in the present study the increase of tc value in case of fe rich clay additive mn-zn sample is due to the increase of exchange interaction of ab and bb between octahedral and tetrahedral sites. acknowledgements the authors are grateful to the director, bcsir laboratories, dhaka for his encouragement and permission to publish the work. we are grateful to mr. anwar hossain, ex scientist-in-charge, industrial research division, bcsir laboratories, dhaka who made valuable suggestions regarding experiments and project development. we are also indebted to physical instrumentation division of the same laboratory for the use of their computer facilities. the authors wish to thank the director, igcrt,bcsir, dhaka, for providing the facilities for carrying out this work. references 1. m. d. lunchbury and n. h. saunders. j. phys. f: metal phy., 6 (1976) 1967-77. 2. j. roberts. high frequency application of ferrites, the english university press ltd., london (1960). 3. h. forestier, ann. de ch m.10e ser. i. l f bates, 1963 modern magnetism. university press (cambridge). 180 studies on anomalous behaviour 41(3-4) 2006 4. e. c. snelling. soft ferrites: properties and applications. mullards research laboratories, crc press ohio. (1969) 1. 5. a. k. m. ahsanullah, m. a. hossain, m. tofazzal hossain and n. a. ahmed. observation of superconductivity type behavior in the measurement of electrical resistivity of mixture of mn-zn ferrites and clay materials. proc. pakistan acad. sci. vol. 28(4) (1991) 387-399. 6. m. a. hossain, s. b. rahman, m. tofazzal hossain, n. a. ahmed, d. haque and s. n. rahman. substitution of zno by cdo, cuo, cao, al2o3 and mgo in mn-zn ferrite. bangladesh j. sci. ind. res. 32(1) (1997). 7. r. n. patil and s. r. swant. indian journal of pure & applied physics. 24 (1996) 294-296. 8. s. r. swant and r. n. patil. indian journal of pure & applied physics, 20 (1981) 353-355. 9. v. r. kulkarni, m. m. todkar and a. s. vaingankar. indian journal of pure & applied physics, 24 (1986) 294-296. 10. m. a. gilleo and s. geller. j. appl-phys, 29 (1958) 380. 11. k. h. rao, n. k. gaur, k. aggarwal and r. g. mendiratta. journal of applied physics, 53(2) 1982. 12. gauillaud. proc. ieee suppl. 1048 (1957) 165. fille 2827(15).qxd introduction mints are an important group of plants belonging to the family labiate and the genus mentha. although, large-scale mint cultivation has come up only recently, mankind from ancient times has used these plants. mentha arvensis popularly known as japanese mint is one of the most important medicinal and aromatic plants. this is a very precious essential oil bearing crop in the world and a potential source of natural menthol. menthol is extensively used in the pharmaceutical, cosmetic and perfumery industries (atal and kapur, 1982). among the various agronomic practices used for higher production of herbage and oil adequate application of nitrogen plays an important role. the response of japanese mint to different levels of nitrogen fertilizer differs remarkably because of the different availability and nutrient absorption efficiency of bangladesh j. sci. ind. res. 44(1), 137-145, 2009 short communication bcsir available online at www.banglajol.info bangladesh journal of scientific and industrial research e-mail: bjsir07@gmail.com response of different levels of nitrogen fertilizer and water stress on the growth and yield of japanese mint (mentha arvensis l.) tanjia shormina, m. akhter hossain khanb, m. alamgir* a department of soil science, university of chittagong, chittagong-4331 and b department of soil, water and environment, university of dhaka, dhaka1000, bangladesh. abstract the response of mint (mentha arvensis l.) to different levels of nitrogen and different levels of water stress were investigated. relative performances of different growth and yield parameters such as plant height and fresh weight of shoot as influenced by n-fertilizer and water stress were investigated. pot experiment was conducted with five levels of n treatments0, 60, 120, 180, and 240 kg n ha -1 and four levels of water conditions 100, 75%, 50 and 25% field capacity. plant growth (height and fresh herb (product) was affected by water stress and different n levels. at 100% field capacity, the highest dose of n(240kg n/ha) produced maximum plant height (46.33 cm) and fresh herb product. lower dose of n treatment decreased the plant height and herb product. compared to 100% field capacity the fresh herb product was drastically decreased from 103.54 -31.67 g pot -1 at 25% field capacity. key words: mentha arvensis, water stress, n-fertilization, yield of mint. corresponding author: e-mail: alamgircu@hotmail.com the crop (atal and kapur,1982). japanese mint is well adapted to climatic conditions in tropical and subtropical areas. a climate with adequate and regular rainfall and good sunshine during the period of its growth ensures a good yield. mint is succulent crop that has a high water requirement during its active growth period in summer month. the water requirements of mints differ from location to location depending on soil type, soil fertility status and climatic factors. the favourable effects of irrigation in enhancing herb and essential oil yields of various mints species have been reported (clark and menary, 1980); (singh et al., 1982). but water stress in plants is one of the major factors limiting crop growth. both high soil moisture content and high soil moisture tension (water stress) decrease the growth, herb and essential oil yields of mints. growth of japanese mint (as revealed from height, number of branches, number of leaves, leaf area and herbage increment) was found to increase linearly up to a limit of n fertilizer application. but this limit varied from 60 kg n/ha to 225 kg n/ha in indian reports (gulati and duhan, 1975); (sarma et al., 1975); (shelke and morey, 1978); (chandra et al., 1983); (singh,1983). application of nitrogen at rates lower or higher than these respective limits caused a reduction in growth and yield. it is well established that water stress impairs numerous metabolic and physiological processes in plants such as nutrient uptake and transport (mengel and kirkby, 1996). under water stress condition, the n-uptake by mint plant is considerably low. as a result, the vegetative growth of plant, their leaves area, total plant biomass production, leaves number, root length and root density decreases. it has been reported that water stress significantly decrease plant height, leaf area index (lai), dry matter accumulation and oil content. the effects of soil moisture stress on the uptake of nitrogen by different crops were reported to differ and even were opposite some times (campbell et al., 1977). so it appeared to be interesting to find out the effect of water stress and different rates of n application on the growth and yield of japanese mint (mentha arvensis l.). materials and methods the experiment was conducted in the net house in the premises of the department of soil, water and environment, university of dhaka. planting material the planting material (suckers of cimap/hybrid 77) was brought from the research field of the bangladesh council of scientific and industrial research (bcsir), chittagong and suckers were transplanted after proper soil preparation the crops were 138 response of different levels of nitrogen 44(1) 2009 shormin, khan, alamgir 139 hervested at 140 days after transplantation when the plants were at full blossom. the experiment was carried out from march 11, 2002 to july 28, 2002. experimental soil media the soil samples collected for the study belong to the ‘‘sonatala series’’. bulk soil samples from 0-15 cm were collected from unarpur in the district, of mymensing. according to reconnaissance soil survey report of mymensing district, sonatala series textured, ridge soils developed in brahmaputra alluvium. these soils have a mixed dark comprises intermittently and seasonally flooded, imperfectly to poorly drained, medium yellowish brown to olivebrown and grey, friable, silt loam subsoil with usually moderate prismatic structure and grey ped cutans. the morphological properties of the soil are presented in table i. physical and chemicals analysis of soil plant samples soil samples were air dried and sieved by a 2mm sieve and stored for physical and chemical analysis. moisture at field capacity and wilting point were determined by pres sure membrane apparatus at 0.33 bar and 15 bar, respectively. the collected plant samples were dried at 650c and dry weights were table i. morphological characteristics of the soil morphological characteristics 1. soil series sonatala 2. soil tract brahamaputra alluvium 3. topography summit of very gently undulating ridge 4. drainage intermittent flooded, imperfectly to poorly drained. 5. present land use mainly aus, jute and rabi crops. 6. land capability subclass iidw 7. general soil type non calcareous gray floodsplain soils 8. fao-unesco soil subunit areni-eutric gleysols 9. usda soil taxonomy inceptisols order aquepts suborder haplaquepts great group aeric hapaquepts 10. limitations droughtiness late in dry season, intermittent wetness in rainy season. 140 response of different levels of nitrogen 44(1) 2009 recorded. then the samples were ground in a grinder and preserved in plastic bottle for analysis. standard methods were followed to analyze the soil and plant samples. the physical and chemical properties of the soil are presented in table ii. experimental setup the experiment was divided into two sections e.g. experiment-1 and experiment-2. in experiment-1, only one nitrogen level (60 kg n/ha) was used under 4 soil moisture levels w100 (100% field capacity), w75 (75% field capacity), w50 (50% field capacity) and w25 (25% field capacity). in experiment-2, five n level n0 (without nitrogen), n60 (60 kg n/ha), n120 (120 kg n/ha), n180 (180 kg n/ha) and n240 ( 240 kg n/ha) were used for only two soil moisture levels (100% and 50%). all treatments had three replications. the pots (18cm diameter and 15 cm depth) were arranged in a completely randomized design. nitrogen was added in three installments based dose (during pot preparation), at 40 days after transplanting (dat), 80 dat. all the pots were kept at field capacity till 60 dat and after that water status was maintained according to the treatments. 5 kg of air-dried soil samples was taken in each pot. during pot preparation, triple super phosphate (tsp) at a rate of 40 kg p/ha and muriate of potash (mp) at a rate of 40 kg k/ha were applied as a source of p and k in the soil. urea was applied as n-treatments and 1/3 amount of each n treatment was used as basal dose. about one litter (1l) of tap water was added in each pot during the pot preparation and then the pots were kept for over night. every pot was marked in accordance with the treatments. 1. moisture at field capacity 25.47% 2. moisture at wilting point 5.2% 3. particle density 2.17 g/cc 4. particle size distribution sand 36.09% silt 56.08% clay 07.73% 5. textural class silt loam 6. ph (soil :water= 1:2.5) 5.4 7. ec (soil :water= 1:2) 0.1 mmhos/cm 8. organic carban 0.71% 9. organic matter 1.2% 10.cation exchange capacity (cec) 10.82meq/100g soil 11. total nitrogen (n) 0.092% 12. total phosphorus (p) 0.06% 13. total potassium (k) 0.152% 14. total sulfur (s) 0.04% 15. total sodium (na) 0.034% 16. c:n ratio 7.72 properties values table ii. physical and chemical properties of the soil treatments were made as follows n0= nitrogen 0 kg/ha n60= nitrogen 60 kg/ha n120= nitrogen 120 kg/ha n180= nitrogen 180 kg/ha n240= nitrogen 240 kg/ha the pots were irrigated to maintain 4 constant soil moisture levels as follows w100= soil supplied with tap water to attain 100% field capacity (f.c) w75= soil supplied with tap water to attain 75% field capacity w50= soil supplied with tap water to attain 50% field capacity w25= soil supplied with tap water to attain 25% field capacity the treatment combinations for n-effects were : w100n0= 0 kg n/ha at 100% f.c. w100n60= 60 kg n/ha at 100% f.c. w100n120= 120 kg n/ha at 100% f.c. w100n180= 180 kg n/ha at 100% f.c. w100n240= 240 kg n/ha at 100% f.c. w50n0= 0 kg n/ha at 50% f.c. w50n60= 60 kg n/ha at 50% f.c. w50n120= 120 kg n/ha at 50% f.c. w50n180= 180 kg n/ha at 50% f.c. w50n240= 240 kg n/ha at 50% f.c. the treatment combinations of water stress were : w100n60= 60 kg n/ha at 100% f.c w75n60= 60 kg n/ha at 75 % f.c. w50n60= 60 kg n/ha at 50% f.c. w25n60= 60 kg n/ha at 25% f.c. statistical analysis: probability values were derived using type iii sum of squares (ss) from a one way anova model with factors of nitrogen level, water stress and their interaction on plant height using spss for windows version 11. (spss, 2001). shormin, khan, alamgir 141 days after transplantation (dat) treatment 60 90 120 w100n0 31.00 +--0.82 37.33 +---2.05 41.33 +---0.94 w100n60 31.33 +--0.47 42.00 +---2.16 43.67 +---2.05 w100n120 32.67+--0.47 35.66 +---1.90 44.67 +---3.39 w100n180 34.00+--0.82 37.00 +---1.41 41.00 +---4.32 w100n240 34.67+--0.47 40.67 +---1.24 46.33 +---4.49 w50n0 30.67 +--0.47 33.33 +---1.25 36.67 +---1.69 w50n60 31.00 +--0.00 33.67 +---0.47 37.00 +---0.81 w50n120 32.33 +--0.47 35.33 +---1.69 37.33 +---1.24 w50n180 32.67 +--0.47 35.00 +---2.16 38.67 +---1.69 w50n240 33.00+--0.00 35.33 +---1.24 38.00 +---1.63 table iii. height (cm) of mint plants with +--sem under different treatment combinations. 142 response of different levels of nitrogen 44(1) 2009 treatment plant height (cm) fresh herb days after transplantation (dat) (g/pot) 60 90 120 w100n60 31.33 +--0.47 42.00 +---2.16 43.67 +---2.05 103.54 +---22.08 w75n60 31.50 +--0.40 35.67 +---1.25 39.33 +---0.47 59.63 +---1.60 w50n60 31.00+--0.00 33.67 +---0.47 37.00 +---0.81 59.43 +---12.51 w25n60 30.33 +--0.47 30.67 +---0.94 31.00 +---0.82 31.67 +---2.08 table iv. plant height and fresh herb product of mint plants with +--sem under different soil moisture conditions. 02.87 01.43 a 05.03* replication 2 08.07 04.03 b 0.795 ns 40.07 20.03 c 01.39 ns 48.67 05.41 a 18.98 ** treatment 9 205.64 22.85 b 04.51 ** 306.80 34.08 c 02.37 ns 04.80 04.80 a 16.84 ** water stress (a) 1 108.30 108.30 b 21.36 ** 192.54 192.54 c 13.40 ** 41.33 10.33 a 36.24 ** nitrogen (b) 4 55.14 13.78 b 02.72 ns 25.47 06.37 c 00.44 ns 02.54 0.63 a 02.23 ns axb 4 42.20 10.55 b 02.08 ns 88.79 22.197 c 01.55 ns 05.13 0.285 a error 18 91.26 05.07 b 258.60 14.36 c 56.67 a total 29 304.97 b 605.47 c table v. analysis of variance for the height of mint plant at 60, 90 and 120 dat under different treatment combination. s.v d.f ss m.s f calc. a represents 60 dat , b represents 90 dat and c represents 120 dat **significant at 1% level, *significant at 5% level, ns not significant shormin, khan, alamgir 143 results and discussion in this study relative performances of different growth and yield parameters such as height of the plants at regular intervals and weight of fresh shoot as influenced by n-fertilizer and water stress have been recorded. the results obtained from this study are presented in the following sections. data presented here are the mean of three replications. plant height the analysis of variance for the height of mint plant at 60, 90 and 120 dat under different treatment combinations has been presented in table v. plant height varied from 30.67cm to 46.33 cm. height of mint plant was significantly affected by various levels of n-fertilizers. generally, plant height was increased as the level of nitrogen increased. the maximum plant height 46.33 cm was obtained at 120 dat with the treatment of w100n240 (240 kg n/ha-1 under 100%) f./c) that significantly differed from other treatments. under the same soil moisture condition plant height was increased as the level of nitrogen increased. (rahman, 1999) reported that plant height of mint was increased as the level of nitrogen increased from 0 to 200 kg ha-1. however, further increase in nitrogen did not always increase plant height. table iv shows plant height and fresh herb products under different soil moisture conditions. at 100% field capacity condition plant height varied from 41.33 cm to 46.33 cm while at 50% field capacity condition it varied from 36.67 cm to 38 cm. the lowest plant height was found in the treatment of 240 144 response of different levels of nitrogen 44(1) 2009 25% field capacity. (arnon and gupta, 1995) stated that the reduction in plant height due to water stress. fresh herb product fresh herb yield was measured at harvesting. mean values of fresh herb yield (fresh leaf + stem) under different treatments are shown in fig. 1. values ranged from 54.63 (w50n0) to 113.47 (w100n120) g/pot. in most instances fresh herb yield was increased with increasing nitrogen rates. the maximum value (103.54g) of fresh herb product was obtained with the treatment of 120 kg n/ha. generally herb product was increased as the level of nitrogen increased from 0 to 120 kg/ha. fresh herb product was drastically decreased due to water stress (table iv). the lowest yield (31.67g) was obtained at 25% field capacity. the variance analysis indicated that there were significant differences among the treatment combinations used in this experiment (table v). however, there was no nitrogen x water stress treatment interaction for plant height at different dat. conclusion data shows that the detrimental effect of water stress on herb yield can not be compensated with high nitrogen doses. data on this experiment may be helpful develop the cultivars to be cultivated under water stress conditions or water limiting areas. so further research is necessary in this direction. references arnon, i. gupta, u.s. (1995). physiological principles of dry land crop production in: u. s. gupta (ed.) production and improvement of crops for dry lands. oxford & ibh pub. co. pvt. ltd., new delhi, india. pp. 1166. atal, c.k. kapur, b.m. (1982). cultivation and utilization of aromatic plants. regional research laboratory, csir, jammu-tawi, india. campbell, c.a. cameron, d.r. nicholaichuk, w. davidson. h.r. (1977). effect of fertilizer n and soil moisture on growth, n content and moisture used by spring wheat. can. j. soil . sci. 57: 289-310. chandra, m. singh, j.n. nand, k. (1983). effect on nitrogen levels and harvesting times on the growth and yield of japanese mint. indian perf. 27(2): 94-98. clark, r.j. menary, r.c. (1980). the effect of nitrogen and irrigation on the yield and composition of peppermint oil. aust. j. agric. res. 31: 489-498. gulati, b.c. duhan, s.p.s. (1975). essential oil of mentha citrata ehrh. paper presented for vi international congress of essential oils held at california during 8-12 september, 1974. shormin, khan, alamgir 145 mengel, k. kirkby, e.a. (1996). principles of plant nutrition. (4th ed.) panama publishing corporation. new delhi, india. rahman, m. (1999). effect off n,p. and k on the growth of the mentha arvensis and the quality and quantity of its oil in bangladesh , ph. d. thesis, department of soil science, university of dhaka, dhaka. sarma, j.s. bains, d.s. gill, g.s. (1975). response of row spacing and n, p levels on herb and oil yield of mentha arvensis l. indian pref. 19(1): 4-8. shelke, d.k. morcy, d.k. (1978) growth yield and quality of japanese mint (mentha arvensis l.) as influenced by various levels of nitrogen and topping. j. maharashtra agric. univ. 3(1): 28-30. singh, a. (1983). effect of nitrogen levels and herbicides on growth, yield and quality of japanese mint (mentha arvensis l.) ph. d. thesis submitted to b.h.u. varanasi.` singh, d.v. yadav, r.l. singh, a. (1982). recent advances in research on essential oil bearing crops with reference to rural development in central u.p. indian pref. 26 (2-4): 90-93. spss inc. (2001). spss for windows, rel. 11.0.1. 2001. spss inc., chicago, usa. received : august, 26, 2008; accepted : february, 11, 2009. macap fill 2805 (2) final.qxd introduction rice husk (rh) is an agricultural waste. in bangladesh, about 39.3 million ton of rice is produced annually (mustafi, 2005) which generate about 9.83 million ton of rh after milling of the paddy. the rh is generally used as fuel in rural areas and a small quantity is used as animal feed. huge quantity of rice husk ash (rha) is generated in bangladesh during per-boiling of rice in rice mills. this ash is treated as a waste material usually dumped at the backyard causing unforeseen environmental hazards. no systematic efforts have yet been made for exploitation of this replenishible major agricultural by-product on commercial basis due to lack of detailed characterization of the rha produced in bangladesh. rha is predominantly silica together with some minor oxides (agarwal, 1989, kumar, 1993). the nature of this silica depends on the burning temperature. controlled combustion of rh produces reactive silica (agarwal, 1989, kumar, 1993, ibrahim, and helmy 1981) which is suitable for making pozzolana cement (kumar, 1993). it is reported (agarwal, 1989) that silica present in rha remains amorphous up to 973 k. with further increase in temperature, crystallization of silica occurs. techniques for burning rh to produce amorphous silica, which is suitable for pozzolana cement production, have been developed (kumar, 1993, ahmed, et al.1993). nehdi et al. (2003) have developed a new technique for complete combustion of egyptian rh to make it suitable for construction industry. a mini incinerator has been designed by ahmed, et al.(1993) in bcsir laboratory, dhaka to produce rha and a comparative study has been carried out in relation to compressive strength and setting time of the pozzolana cement prepared by using this ash and boiler ash. characterization of rha by simas nmr, xrd and fesem has been investigated by harridan et al. (1997) for synthesis of zeolites. borthakur et al. (1980) have reported thermal and infrared spectra of rha prepared at different temperatures. sem images have indicated (zhang et al., 1996) that the ash is a highly porous and fibrous material with high surface area and honeycombed microstructure. scanning force microscope has been used for the surface characterization of calcined rh and it is reported that the surface roughness of rha is decreased while the number of voids is increased with the increase of temperature (vempati et al., 1995). the primary objective of the present study is to characterize the rha collected from rice mill to evaluate its suitability as a building material such as pozzolana cement, composite characterization and utilization of rice husk ash (rha) from rice mill of bangladesh k. n. farooquea*, m. zamana, e. halimb, s. islama, m. hossaina, y. a. mollahb and a. j. mahmoodb. aigcrt, bcsir laboratories, dhanmondi, dhaka-1205 and bdepartment of chemistry, university of dhaka, dhaka-1000, bangladesh. abstract the characterization of rice husk ash (rha) was carried out using conventional chemical analysis and instrumental techniques. chemical analysis reveals that rha contains mainly silica along with minor inorganic oxides. phase analysis by x-ray diffraction (xrd) indicates the presence of quartz, crystobalite and anorthite, while micro structural features obtained from scanning electron microscopy (sem) shows that rha particles are highly porous and honeycombed structure. thermal analysis indicates the presence of surface moisture. a wide range of particles (0.001-0.100 mm) are present in the sample with 59% below the size of 0.05 mm. however after characterization, utilization of rha as a potential cost effective ingredient in developing a variety of construction materials (e.g. building brick, insulating brick and pozzolana cement) have been examined. the results obtained are very promising. keywords : charcterization, rice husk ash, xrd, sem, construction material. bangladesh j. sci. ind. res. 44(2), 157-162, 2009 bcsir available online at www.banglajol.info bangladesh journal of scientific and industrial research e-mail: bjsir07@gmail.com *corresponding author, email:ysom2002@yahoo.com 158 characterization and utilization of rice husk ash 44(2) 2009 cement, building brick, tiles and insulating brick. a number of methods that include chemical analysis, x-ray diffraction, dta/tga, particle size analysis, sem have been used in this study. materials and methods materials rha was collected from rice milling area of munshigonj and was finely ground in a pulverizer chemical analysis of rha chemical characterization of rha was carried out using classical methods as well as by instrumental techniques like pfp7 jenway (uk) flame photometer and uv-2201 shimadzu (japan) uv spectrophotometer. particle size distribution particle size was determined by sedimentation and sieve analysis using a density hydrometer and various sizes of sieve respectively. the method was based on stroke's law (bowles, 1992). xrd analysis the phase composition of the rha was determined by the xrd analysis of the sample with philips x-ray diffiactometer model operating with a cukα radiation source (kα=1.5406 ao). the samples were ground to a fine powder and loaded on a silicon low background sample holder over baseline adhesive. the xrd scans were recorded from 10 80o 2θ with 0.20o step-width and 5.1 s counting time for every step. phase analysis was performed by comparing the d values and intensity ratios of the main fundamental peaks with data available in the data book published by the joint committee of powder diffraction standards (1974). sem analyses morphological examination of the rha was carried out on a 2600sn hitachi (japan) scanning electron microscope (sem) equipped with germanium detector and diamond window. the samples were mounted using double-sided tape. dta/tga analysis dta/tga labsys tm from setaram was used to evaluate the thermal behaviors of the sample. the heating rate for dta/tga analysis was 10oc/min. the temperature difference between an inert (alumina) and the sample was recorded and mass loss was calculated from the tg curve. preparation of building brick and its characterization: building brick was made from rha soil mixtures (rha: soil = 70 : 30, 80 : 20 and 90 :10) which was ball milled. the optimum water for making the batch composition in workable condition increases as the quantity of rice husk ash was increased. 2 ' ' cube specimens were prepared by applying a pressure of 60 kg/cm2. specimens were released from the mold, dried at 110oc and fired at 1100oc. water absorption, bulk density (astm c 830-00 method) and cold crushing strength (ccs, astm c 109 method) were determined. linear shrinkage was also determined by preparing rectangular bar (10 x i.5 x 0.6 cm3) from control (100% soil) and rha soil mixtures (100 : 0, 90 : 10, 80 : 20 and 70 : 30). the test sample was mixed with optimum water just to moisten it and placed in a mold and pressed by applying a pressure of 10 ton on the surface and a straight line was drawn on the surface of the test specimen. the sample was dried at 110oc followed by firing at 1000o c in an electric muffle furnace. the difference in the linear change indicates the linear shrinkage. insulating brick was prepared by taking rha (coarse) to soil in the ratio of 70:30 and either cao (5%) or sodium silicate (5%). the rha and soil were mixed properly but not ball milled as coarser grain being required for thermal insulation. except applying 3t pressure, preparation of test specimen follows the same procedure that was used for making building brick. the bulk density (%), % apparent porosity and ccs of the products were determined. pozzolanic cement was produced from rha and lime at different ratios and ball milled for 3 h. the cement was then kept in airtight container. ccs measurements were carried out at a definite interval following astm c 109 method. the physico-chemical properties of the soil used were also evaluated (farooque et al., 2005) results and discussion compositional analysis the composition of the rha sample has been determined by chemical analyses. the rha used in this study contains: sio2 (91.3%), al2o3 (0.3%), fe2o3 (0.12%), cao (0.21%), mgo (0.31%), na2o (1.52%), k2o (2.65%), tio2 (0.15%), so3 (0.24%) and it undergoes 2.7% weight loss on ignition. it is evident that rha contains mainly silica. a survey of literature (kumar et al., 1989, al-khalaf et al., 1984) reveals that usually 79.5-97.6% silica is found in rha and 90% of farooque, zaman, halim, islam, hossain, mollah and mahmood. 159 this silica is present in gel form and the remaining is in the form of metallic silicates or in fine colloidal form. presence of small quantities of k20=2.65% and na2o=1.52% (qijun et al., 1999, sing et al., 2001) in rha makes it suitable raw material for producing composite cement. the loss on ignition indicates that small amount of free carbon is retained in rha due to insufficient asking of the husk. particle size distribution particle size analysis of rha (fig. 1) shows that ~8% , ~41% , ~8% , and ~10% of rha particles are in the range of 0.1 0.05 mm, 0.05 0.01 mm, 0.01 0.005 mm, 0.005 0.001 mm respectively. according to astm c 593 66 t standard the particle size of rha when wet sieved should retain 20% on 0.045 mm sieve for composite cement/pozzolana cement production. the present result indicates that 59% of rha particles are below 0.05mm. therefore, it is suggested that further grinding is required to obtain the required particle size, of rha for the production of composite/pozzolana cement by utilizing rha from rice mill. phase analysis: the xrd pattern of rha (fig. 2) indicates the presence of quartz (22.85o, 26.63o and 42.47o 2θ peaks) and crystobalite (21.91o, 35.99o and 69.50o 2θ peaks). anorthite phase is also found (27.91o and 29.42o 2θ peaks). it has been reported (agarwal, 1989) that at low temperature (873 973 k) silica in rha is amorphous, and crystallization occurs when temperature goes above 973 k (agarwal, 1989). the presence of crystobalite phase indicates that rha is produced above 973 k. at high temperature, quartz is transformed to tridymite (metha et al., 1976) which is favored in presence of impurities in rha (metha and pith 1974). morphological analysis a typical sem image of rha is presented in fig. 3. the sem photomicrograph reveals the siliceous nature of the ash, which is also confirmed by the presence of quartz in the xrd. close examination of the sem photomicrograph also suggests that rha is highly porous which is in agreement with others (zhang and malhotra 1996). the porous nature grain diameter, mm fig.1 : particle size distribution of rha fig.2 : x-ray diffraction of rha 160 characterization and utilization of rice husk ash 44(2) 2009 of rha and its honeycombed structure is responsible for its high specific surface and makes it suitable for making insulating brick. thermal analysis the thermal analysis curve (dta) of rha is presented in fig.4. the endotherm starting from room temperature to around 423 k is accompanied by weight change in tg curve. the endothermic peak corresponding to around 373 k can be attributed to elimination of surface moisture. the endotherm is followed by a broad and diffused exotherm in the temperature region 623 873 k which has also been observed by borthakur et al., (1980). no other change such as structural transformation or formation of new compounds has been observed with the increase in temperature. the shifting of baseline of thermogram at higher temperature is possibly due to change of surface properties of silica present in rha (borthakur et al.,1980). the properties of brick specimens produced from a mixture of rice husk ash and red soil (mirpur) in different proportion are shown in table (i). as the proportion of rha increases a gradual decrease in strength and bulk density whereas, an increase in water absorption are observed. the main reason may be due to the presence of unburnt carbon, which makes the specimen porous on firing at high temperature. another cause may be the increase in optimum water content when quantity of rice husk ash increases. this is in good agreement with the study carried out by hajela and gupta (1997). rahman (1988) has observed increase in compressive strength with increase in % rha. in fact, increase or decrease in compressive strength as well as other properties depend on the type of soil, type of kiln and also manufacturing process. as bangladesh standard specification for common clay brick requires compressive strength of 2000 psi for grade b and grade c brick, respectively and water absorption from 12-16% for b and c grade brick, therefore 10% rha can safely be used for the production of building brick for wall construction. it is also observed that percent linear shrinkage of rha soil mixture (table i) decreases as the quantity of rha increases. according to hazela and gupta (1997) and sabrah et al. (1989) the linear shrinkage decreases with the increase of rha used for brick making. this is very advantageous for the production of tile as shrinkage can deform the article during firing. controlling of shrinkage on firing is an important criterion in manufacturing tile. the burnt specimens for brick and tile show brick red color, which is the primary requirement of the consumer. chemical analysis of rha shows that it contains some unburnt carbon, which is required for thermal insulation. the presence of oxides also favours the formation of vitreous phases during sintering of the insulating brick. the effect of additive (cao or sodium silicate) on the properties of insulating brick is shown in table ii. it shows that thermal insu fig. 3 : microstructure of rha fig. 4 : dta/tga curves of rha table i. physical property of rha soil brick. soil, rha, ccs, water bulk linear (%) (%) psi absorption, density, shrinkage control 0 2600 15.0 1.78 9.8 90 10 2020 15.45 1.74 8.3 80 20 1850 20.45 1.70 7.6 70 30 1700 22.15 1.53 7.4 farooque, zaman, halim, islam, hossain, mollah and mahmood. 161 lating specimens have low bulk density, as a consequence of high porosity. change in % of apparent porosity, bulk density and ccs have been observed for the two types of additive. cao bonded insulating brick achieve lower compressive strength compared to sodium silicate bonded brick as also observed by kapur (1980). consequently %ap is more and bd is less for cao bonded brick than for the sodium silicate bonded brick. this has also been observed by kapur (1980). the presence of unburnt carbon, oxide as well as coarse particles makes the rha potentially suitable to be used as a raw material for thermal insulating brick. ash-lime composite cements the ccs of rha lime composite cement has been measured at different ash-lime ratios for 90 days. the primary objective of this experiment is to determine the optimum ratio of ash-lime that can impart maximum strength. table iii indicates that rha-lime ratio of 2:1 achieves better strength compared to rha lime ratios of 1:1 and 1:2. however, various ash-lime ratios have been reported (james et al., 1992) as optimum for developing maximum strength and widely varying strength. recent study of nair et al., (2006) indicates that unburnt carbon can adversely affect the strength. conclusions the results of characterization of rha confirm that silica is the major oxide present in rha and the two most important phases are quartz and crystobalite. about 59% of rha particles are below 0.05% mm size which implies that rha particles need further grinding to make it suitable for pozzolanic cement. the particles are porous and irregular that makes it a suitable material for producing insulating brick. the thermogram and weight loss curve of rha particles show the presence of surface moisture. the addition of 10% rha produces brick, which conform to bangladesh standard grade c, which can be used in wall construction. using a simple technology it is possible to manufacture low cost thermal insulating brick from rha for dryers, ovens, furnaces. clay roofing tiles can also be produced from rha. references agrawal b. m. (1989). utilization of rice husk ash, glass ceram. bull., 36: 1-2. al-khalaf m. n., and yousif h. a. (1984) use of rice husk ash in concrete. int. j. chem. comp. light wt. conc., 6 (4): 241-248. ahmed s., hossain m. i., and farooque k. n. (1993) studies on rice husk ash cement. bang. j. sci. ind. res., 28(2):71 borthakur p. c., saikia p. c., and dutta s. n. (1980) physicochemical characteristics of silica from paddy husk, its reactivity and probable field of application, ind. ceram. 23(2): 25-29 bowles e. j. (1992) engineering properties of soils and their measurement, 2nd ed. mcgrwhill int. book co. newyork.usa, pp.13-16. farooque k. n., zaman m., rahman a., and halim m. e. (2005) studies on the suitability of soil for making soil stabilized building block, bang. j. sc. ind. res., 40(1-2): 9-18. hamdan h., muhid m. n. m., endud s., listiorini e., and ramli z. (1997) 29silica mas nmr, xrd and fesem studies of rice husk ash silica for the synthesis of zeolites, j. non-crystal. solid, 211: 126-131. hajela r. b., and gupta r. g. (1997). rice husk utilization in brick and tile manufacturing, energy management: quart. j. nat. prod. coun. cgcri, kolkata, india., 21(2): 9-16. ibrahim d. m., and helmy m. (1981) crystalline growth of rice husk ash, thermochim. acta., 45: 79-85. table ii. physical property of insulating brick (rha: clay = 70 : 30). additive apparent bulk density ccs porosity (%) (gm/cc) psi cao 0.68 0.73 350 sodium 0.61 0.85 680 silicate table iii. compressive strength of rha lime composite cement. ageing compressive strength, psi rha: lime=2:1 rha: lime=1:1 rha: lime=1:2 7 550 525 350 28 800 650 600 90 1000 800 750 162 characterization and utilization of rice husk ash 44(2) 2009 jose j., and subbarao m. (1992) reactivity of silica from rice husk with lime, j. can. ceram. soc., 2: 61. kumar a., das d. k., and banerjee g. (1989). internal report on utilization of rice husk ash for cost effective building materials, cgcri, kolkata, india, pp.113 kumar a. (1993) rice husk ash based cements, mineral admixture in cement and concrete, progress in cement and concrete, ed. ghosh, s. n. sarker s. l. and harsh, s. abi books pvt. ltd. cgcri, kolkata, india, 4:342367 kapur p. c. (1980) thermal insulations from rice husk ash, an agricultural waste, ceram. int., 2: 6. metha p. k., and pitt n. (1974). 4th int.conf. of rice byproducts utilization, valencia.spain., 4(1): 494 metha p. k., and pitt n. (1976). energy and industrial materials from crop residues, res. recov. conserv., 2(1): 2338. mustafi b. a. a. (2005) statistical yearbook of bangladesh bureau of statistics (bbs). nehdi m., duquette j., and damatty a. e. (2003) performance of rice husk ash produced using a new technology as a mineral admixture in concrete, cem. concr. res., 33: 1203 -1210 nair d. g., jagadish k. s., and fraaij a. (june 2006) reactive pozzolanas from rice husk ash: an alternative to cement for rural housing cem. concr. res., 36(6): 1062-1071. qijun y., sawayama k., sujita s., shoya m., and isojima y. (1999) the reaction between rice husk ash and ca(oh)2 solution and the nature of its product cem. concr. res., 29: 37-43. rahman m. a. (1988) effect of rice husk ash on the properties of brick from fired lateritic soil clay mixture, mat. struc., 3: 21. sabrah b. a., didamony h. e. i., and rabiehi m. m. e i. (1989) ceramic studies of the clay/ricehusk/slug system and stability for brick making. utilization of some agro-industrial waste in the treatment of expanded clays to be suitable in the brick making. prepared as a paper to the sci. ceram. cong. orleans, france., 13: 9 11 sing n. b., and rai s. (2001) effect of pva on the hydration of cement with rice husk ash, cem. concr. res., 31: 239-243. joint committee of powder diffraction standards (1974) selected powder diffraction data for mineral.1st ed.usa. pp-851. vempati r. k., musthyala s. c., mollah. m. y. a., and cocke, d.l. (1995) surface analyses of pyrolysed rice husk using scanning force microscopy, fuel., 74(11): 1722-1725. zhang m. h., and malhotra v. m. (1996) high performance concrete incorporating rice husk ash as a supplementary cementing material, j. aci. mat., 93(6): 629-636. received : july, 08, 2008; accepted : december 14, 2008 macap fill 2760 (8).qxd introduction inflammation (latin, inflammatio, to set on fire) is the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants that leads to the local accumulation of plasmatic fluid and blood cells. it is a protective attempt by the organism to remove the injurious stimuli as well as to initiate the healing process for the tissue (underwood, 2000). however, inflammation which runs unchecked can lead to a host of diseases including different types of arthritis such as rheumatoid arthritis, shoulder tendinitis and gouty arthritis (underwood, 2000). inflammatory diseases are the major cause of morbidity of the working force throughout world. this has been called the 'king of human miseries' (chatterjee and pal, 1984). most of the drugs used presently for the management of pain and inflammatory conditions possess more or less side and toxic effects (ahmad, et al., 1992). on the contrary many medicines of plant origin had been used since long time without any adverse effects. it is therefore essential that efforts should be taken to develop new drugs of plant origin, which will be economically feasible, as well as with lesser side effects. bangladesh owing to its favorable climatic influences has been blessed with immense natural resources including explored and unexplored herbal medicinal plants. we can use these resources for remedy of different diseases. azadirachta indica (locally known as neem) is perhaps the most useful traditional medicinal plant in bangladesh as well as its neighboring countries. every parts of the tree have been used as traditional medicine for household remedy against various human ailments including arthritis, gout, fever, pain, skin diseases, diabetes etc. (ghani, 1998). the tree is regarded as 'village dispensary' in bangladesh. in this study, we have evaluated the anti-inflammatory, antinociceptive and antipyretic effect of ethanol extract of azadirachta indica leaves to establish scientific evidence in support of the folklore claim. studies on anti-inflammatory, antinociceptive and antipyretic activities of ethanol extract of azadirachta indica leaves m. mahabub-uz-zaman*, nazim uddin ahmed, rasheda akter, kabir ahmed, m. shafiqul islam aziz and m. shamsuddin ahmed drugs and toxin research division, bcsir laboratories, chittagong-4220, bangladesh. abstract the present study was carried out to investigate the anti-inflammatory, antinociceptive and antipyretic activities of the crude ethanol extract of azadirachta indica leaves on experimental animal model at three different dose level1g/kg, 500 mg/kg and 100 mg/kg. for evaluation of the anti-inflammatory property carrageenan induced paw edema served as acute model and cotton pellet induced granuloma formation served as chronic model in rats. the acetic acid induced writhing response and hot plate test were used to assess antinociceptive activity in mice. the antipyretic activity was evaluated on yeast-induced pyrexia in rats. acute toxicity test was also performed in rats after administration of the extract orally at high dose level (4g/kg). oral administration of the ethanol extract of a. indica leaves significantly (p<0.05) suppressed the paw edema induced by carrageenan as well as granulomatous tissue formation induced by cotton pellet in rats at high dose level (1g/kg) but no significant effect was observed at 500 mg/kg and 250mg/kg dose level. in addition, ethanol extract obtained from a. indica leaves (1g/ kg) also significantly (p<0.05) attenuated the acetic acid induced writhing response in mice but did not show any significant protective effect on heat induced pain in mice. a significant antipyretic effect (p< 0.05) was noticed with ethanol leaf extract of a. indica leaves at 1g/kg and 500 mg/kg dose level. in acute toxicity study, no mortality was observed at 4 g/kg dose level. the present study also demonstrates the potential anti-inflammatory, analgesic and antipyretic effect of the ethanol extract of azadirachta indica leaves, which supports the claims by the traditional medicine practitioners. keywords: anti-inflammatory, antinociceptive, antipyretic, azadirachta indica. bangladesh j. sci. ind. res. 44(2), 199-206, 2009 bcsir available online at www.banglajol.info bangladesh journal of scientific and industrial research e-mail: bjsir07@gmail.com *corresponding author, email: mahabub582@yahoo.com 200 studies on anti-inflammatory, antinociceptive 44(2) 2009 materials and methods animals and diets swiss albino mice of both sexes weighing between 30 to 35g and wistar albino rats of the either sex weighing between 150-200 g obtained from animal house of bcsir laboratories, chittagong were used for the present study. the animals were acclimatized to room temperature (28±5oc) with a relative humidity of 55±5 % in a standard wire meshed plastic cages for 4 to 5 days prior to commencement of the experiment. during the entire period of study the animals were supplied with standard pellet diet and water ad libitum. in this study, all the animal experimentation was carried out according to the guidelines of institutional animal ethics committee (iaec). collection of plant material the leaves of azadirachta indicia were collected from the plantation area of bcsir laboratories, chittagong. the plant was taxonomically identified in the industrial botany division of bcsir laboratories, chittagong. preparation of ethanol extract the collected leaves were cut into small pieces, air dried at room temperature for about 10 days and ground into powder form and stored in an airtight container. 500 g powder was then macerated in 5 l 90% ethanol for 7 days at room temperature with occasional stirring. the ethanol extract of the plant was collected in a separate container and concentrated under reduced pressure below 50 ºc through rotatory vaccum evaporator. the concentrated extract was dried using freeze dryer (shimadzu, kyoto, japan). finally a blackishgreen colored residue was obtained (yield 5.6 % w/w) which was kept in a refrigerator at 4oc. assay of anti-inflammatory activity carrageenan induced paw edema and cotton pellet test these two models were used for evaluating potential of ethanol extract of azadirachta indica leaves on inflammation. for each model fifteen albino rats weighting 150-160g were randomly divided into three equal groups (n = 5) vehicle control [received only distilled water], positive control [received dichlophenac sodium (40 mg/kg) or indomethacin (5mg/kg)] and sample treated group [administered ethanol extract of azadirachta indicia leaves (1 g/kg, 500 mg/kg and 100 mg/kg)]. carrageenan induced paw edema according to the method designed by winter et al., (1962), the initial right hind paw volume of each rat was measured using plethysmometer (ugo basile, italy) and then 0.1 ml of 1 % (w/v) carrageenan was subcutaneouly injected into the sub-plantar region of the right hind paw in order to induce acute inflammation. the volume of right hind paw was measured at 1st, 2nd, 3rd and 4th hour after carrageenan injection and the paw edema was determined. leaves extract of a. indicia (1g/kg, 500mg/kg and 100mg/kg) or standard anti-inflammatory drug dichlophenac sodium (40 mg/kg) or distilled water was administered orally one hour before the subplantar injection. the inhibitory activity was calculated according to the following formula (olajide et al., 2000): percentage inhibition (ct co) control (ct co) treated =--------------------------------------------------------------------------------------------------------------------x 100 (ct co) control where ct is the right hind paw thickness volume (in mm3) at time t, co is the right hind paw thickness volume (in mm3) before carrageenan injection. ct co is paw edema. (ct-co) control, is edema or paw size after carrageenan injection to control rats at time t. (ct co) treated, is edema or paw size after carrageenan injection to treated (reference or sample drug) rats at time t. cotton pellet test in this experiment chronic inflammation was induced by cotton pellet induced granuloma in albino rats by the previously established method of gold stein et al. (1976). briefly, under ether anesthesia two sterilized cotton pellets weighing 10±0.5 mg were implanted subcutaneously in the groin region of the rats, one on each side. these cotton pellets were sterilized in an air oven at 121oc for 1hour and soaked in 1 % solution of crystalline penicillin just before implantation. leaves extract of a. indicia leaves (1 g/kg, 500mg/kg and 100mg/kg), reference drug indomethacin (5 mg/kg) and controlled vehicle were administered orally according to time scheduled for seven consecutive days from 1st day of cotton pellet implantation. the animals were sacrificed on 8th day and cotton pellets were removed surgically and made free from fat and extraneous tissues. the pellets were incubated at 37 oc for 24 hour and dried at 60 oc to constant wt. increment in the dried weight of the pellet was taken as the measure of granuloma formation. assay of antinociceptive activity writhing and hot plate tests were performed to evaluate the antinocipeptive activities of leaves extract of neem. zaman, ahmed, akter, ahmed, aziz and ahmed 201 hot plate test the hot plate test was conducted on mice according to the method described by woolfe and macdonald (1944). male albino mice weighing 25-30 g were distributed into four groups (n=5). one hour after the oral administration of leaf extract of a. indicia leaves (1 g/kg, 500mg/kg and 100mg/kg) or standard drug dichlophenac sodium [40 mg/kg] or morphine (administered intraperitoneally at the rate of 5 mg/kg body weight) or normal distilled water, the mice were placed on the hot plate (scored ds37, ugo basile, italy), maintained at constant temperature of 55 ± 0.5oc and the latency of nociceptive response such as licking and jumping were measured [the time from reaching the hot plate until it first licks a paw and try to jump out] with 30 minutes interval over 120 minutes period of time. finally the average retention time of treated group were compared with the control group. acetic acid induced writhing response for writhing test 1 % (v/v) acetic acid solution (3.3 ml/kg body weight) was injected intraperitoneally in mice (weighing 25-30 g) and the number of writhing and stretching was counted over 20 minutes period as previously reported (koster et al., 1959; hendershot and forsaith, 1959). the ethanol extract of a. indicia leaves (1 g/kg, 500mg/kg and 100 mg/kg), reference analgesic drug dichlophenac sodium (40 mg/kg) and distilled water were administered orally 30 min before acetic acid injection. table i. effect of ethanol extract of the leaves of a. indica on carrageenan induced paw edema group dose paw edema (mm3) % inhibition (ct -co) 1st hr 2nd hr 3rd hr 4th hr 1st hr 2nd hr 3rd hr 4th hr control 0.6 ± 0.08 0.79 ± 0.09 1.21 ± 0.23 1.20 ± 0.25 diclofenac na 40 mg/kg 0.45± 0.04* 0.51± 0.08* 0.65 ± 0.08* 0.64 ± 0.09* 25.0% 35.4 % 46.3% 46.7% a. indica ethanol extract 1g/kg 0.49± 0.06 0.58 ± 0.06* 0.71 ± 0.05* 0.78 ± 0.23* 18.3 % 26.6 % 41.3% 35.0% a. indica ethanol extract 500 mg/kg 0.50 ± 0.09 0.69 ± 0.08 0.98 ± 0.10 1.01± 0.15 16.7% 12.7% 19.0% 15.8% a. indica ethanol extract 100 mg/kg 0.58 ± 0.06 0.72 ± 0.05 1.0 ± 0.09 1.06 ± 0.2 3.3% 8.9% 17.4% 11.6% all values are expressed as mean ± sem (n=5) * p<0.05 significant compared to control here, co is the paw thickness volume (in mm3) before carrageenan injection, ct is the paw thickness volume (in mm3) at time t, (ct -co) is paw edema (ct -co) control (ct -co) treated ------------------------------------------------------------------------------------------------------------------x 100 (ct -co) control table ii. effect of ethanol extract of the leaves of a. indica on cotton pellet induced granuloma formation. group dose mean increasein weight of % inhibition cotton pellets (mg) control 30.8 ± 1.8 indomethacin 5 mg/kg 20.2 ± 0.95* 34.4% a. indica ethanol extract 1g/kg 24.5 ± 1.48* 20.5% a. indica ethanol extract 500 mg/ kg 28.4 ± 1.6 7.8% a. indica ethanol extract 100 mg/ kg 28.8 ± 1.2 6.5% all values are expressed as mean ± sem (n=5) * p<0.05 significant compared to control 202 studies on anti-inflammatory, antinociceptive 44(2) 2009 assay of antipyretic activity antipyretic activity was carried out in wistar albino rats weighing 130-150 g according to the method described by adams et al. (1968). briefly, pyrexia was induced in rats by a subcutaneous injection of 15 % (w/v) aqueous suspension of brewer's yeast at the rate of 1 ml/100g body weight. ten hours later the rectal temperature of each rat was measured using clinical thermometer inserting to a constant depth of two centimeter. only rats that showed an increase in temperature of at least 0.5 oc were used for experiments. ethanol extract of a. indicia leaves (1 g/kg, 500mg/kg and 100mg/kg) or standard antipyretic drug paracetamol (100 mg/kg) or vehicle control were then administered orally to different groups of rats (n = 5) and the temperature was measured at 1st, 2nd, and 3rd hour after drug administration. acute toxicity studies ethanol extract of a. indicia leaves was dosed orally at the rate of 4 g/kg body weight on ten wistar albino rats (weighing 150-160 gm). five male and five female rats were closely observed for 24 hours for any mortality and next ten days for any delayed toxic effect. their food consumption and growth rate were also examined once daily up to ten days. statistical analysis all the values in the test are expressed as mean ± sem [standard error of the mean]. statistical difference between the mean of the various groups were analyzed by using student's "t" test. p values < 0.05 or less were considered as significant. results and discussion anti-inflammatory activity the ethanol extract of the of a. indica leaves was evaluated for anti-inflammatory activity in acute and chronic experimental animal models and the results are depicted in table i and ii. carrageenan induced paw edema as shown in table i, the ethanol extract obtained from a. indica leaf (1 g/kg) exhibited anti-inflammatory activity by significant (p<0.05) suppression of the paw edema induced by carrageenan at 2, 3 and 4h hr after carrageenan injection, though less potent than that of refer mg/kg. a. indica showed maximum inhibition of paw edema (41.3 %) at the dose of 1g/kg at 3 h after carrageenan injection. other lower dosages of a. indica leaves extract (500mg/kg and 100 mg/kg) did not show any significant change in paw edema compared with vehicle control group. cotton pellet induced granuloma the effects of the ethanol extract of a. indica (1g/kg, 500mg/kg and 100 mg/kg) and indomethacin (5 mg/kg) on the chronic model of cotton pellet induced granuloma are shown in table ii. a significant reduction (p < 0.05) in the weight of cotton pellets was observed with ethanol extract of a. indica (1g/kg) compared to the vehicle control rats though the degree of reduction (20.5%) was comparatively lower than the effect caused by indomethacin (34.4 %). 500 mg/kg and 100 mg/kg a. indica extract also reduced the weight of cotton pellets (7.8 % and 6.5% respectively) but they are not found statistically significant. table iii. effect of ethanol extract of the leaves of a. indica on nociceptive response induced by heat in mice. treatment dose reaction time (sec) 30 min 60 min 90 min 120 min control 10.2 ± 1.4 8.5 ± 1.0 5.0 ± 0.8 5.0± 1.1 diclofenac sodium 40 mg/kg 9.5 ± 1.1 10.5 ± 0.8 9. 5 ± 0.6 4.5 ± 0.5 morphine 5 mg/kg 58.2 ± 1.2 ** 45.0 ± 0.6 ** 33.5 ± 1.0 ** 35.4 ± 0.7 ** a. indica ethanol extract 1 g/kg 7.5 ± 0.6 6.0 ± 1.2 7.5 ± 1.4 10.0 ± 2.8 a. indica ethanol extract 500 mg/ kg 7.0 ± 0.8 6.2 ± 1. 5 5.2 ± 1.2 7.2 ± 1.2 a. indica ethanol extract 100 mg/ kg 5.0 ± 1.3 4.5 ± 1.6 6.0 ± 0.9 4.0 ± 1.2 all values are expressed as mean ± sem (n=5) ** p <0.001 significant compared to control. zaman, ahmed, akter, ahmed, aziz amd ahmed 203 antinociceptive activities hot plate test the ethanol extract of a. indica (1g/kg, 500 mg/kg and 100 mg/kg) and diclofenac sodium (40 mg/kg) did not show any significant protective effect on heat induced pain in mice. in contrast, a centrally acting analgesic drug, morphine (5mg/kg) markedly increased (p<0.01) pain latency (table iii). acetic acid induced writhing response table iv shows the pain behavior of writhing response, which was presented as cumulative abdominal stretching response. the treatment of animals with ethanol extract of a. indica (1g/kg) produced a significant (p<0.05) inhibition in abdominal writhes produced by acetic acid. however the degree of inhibition was less than the effect caused by standard analgesic drug diclofenac sodium (40 mg/kg). other lower dosages of a. indica leaves extract (500mg/kg and 100 mg/kg) did not show any significant effect on writhing response of mice compared with control. antipyretic activities table v shows the effects of the ethanol extract of a. indica and reference drug paracetamol on yeast induced pyrexic rats. a. indica extract showed antipyretic activity in a dose dependent manner but found significant (p<0.05) at 1g/kg and 500 mg/kg dose level which is almost comparable to standard antipyretic drug paracetamol acute toxicity test in the acute toxicity assay of ethanol extract of a. indica leaves, no deaths were observed at high (4g /kg) dose level. at this dose level, animals also did not show any stereotypical symptoms associated with toxicity, such as convulsion, ataxy, diarrhoea or increased diuresis. behavior of all treated animals appeared normal and no significant change in the body weight as well as their daily food consumption were observed. hence, the extract was considered to be without gross or acute toxic effects on rats. the results of the present study revealed that the ethanol extract of a. indica leaves possess significant (p< 0.05) antiinflammatory, antiniceptive and antipyretic activity. the acute toxicity studies showed that the extract has a high safety profile as neither death nor symptoms associated with toxicity was observed at high dose level (4g/kg) in rats. our results are consistent with other previous findings (khanna et al., 1995; pillai, et al., 1978, pillai and santhakumari, 1981). carrageenan induced paw edema is a suitable test for evaluating anti-inflammatory properties for natural drugs because of its sensitivity in detecting orally active anti-inflammatory agents particularly in the acute phase of inflammation (dirosa et al., 1971). development of edema in the paw of rat after injection of carrageenen is a biphasic event (vinger et al., 1969). the initial phase observed during the first hour is attributed to the release of histamine and serotonin. the second phase of edema is due to the release of prostaglandins, protease, and lysosome (crunkhon and meacock, 1971). the results of the present study demonstrate that the ethanol extract (1 g/kg) obtained from a. indica leaf exhibited significant anti-inflammatory activity at 2, 3 and 4hr after carrageenan injection. therefore it is possible that the ethanol extract of a. indica contains the active constituents that exhibits its anti-infl-ammatory action probably by means of either inhibiting the synthesis, release or action of inflammatory mediators e.g. histamine, serotonin and prostaglandins. the cotton pellet induced granuloma formation, is a model of chronic inflammation (ismail et al. 1997) and the dry weight of pellet has been shown to correlate with the amount of granulomatous tissue formed (swingle and shideman, 1972). chronic inflammation is a reaction arising when the acute response is insufficient to eliminate proinflammatory agents. chronic inflammation includes a proliferation of fibroblasts and the infiltration of neutrophils and exudation (dunne, 1990; arrigoni-maratellie, 1988). chronic inflammation occurs by means of the development of proliferative cells. these cells can be either spread or in granuloma form. the ethanol extract of azadirachta indica leaf (1 g/kg) showed significant (p<0.05) anti-inflammatory activity in cotton-pellet induced granuloma and thus found to be effective in chronic inflammatory conditions, which reflected its efficacy in inhibiting the increase in the number of fibrob table iv. effect the of a. indica ethanol extract on 1% (v/v) acetic acid induced writhing response treatment dose no. of writhing (counts/20 min) control 72.75 ± 2.2 paracetamol 100 mg/ kg 18.50 ± 5.5** a. indica ethanol extract 1 g/kg 55.92 ± 4.5* a. indica ethanol extract 500 mg/ kg 68.26 ±3.2 a. indica ethanol extract 100 mg/ kg 70.2 ± 4.8 all values are expressed as mean ± sem (n=5) * p<0.05 and ** p< 0.01significant compared to control 204 studies on anti-inflammatory, antinociceptive 44(2) 2009 lasts and synthesis of collagen and mucopolysaccharides during granuloma tissue formation (recio et al., 1995). the analgesic model used in the present study was chosen in order to test different nociceptive stimuli, namely cutaneous thermic (hot plate) and chemical visceral (writhing) stimuli. in acetic acid induced abdominal writhing, which is the viceral pain model, the processor, the release of arachidonic acid via cyclooxygenase and prostaglandin via synthesis plays a role in the neoceptive mechanism. results of the present study show that the ethanol extract obtained from a. indica leaf (1 g/kg) produces significant (p<0.05) antinociceptive effect and this effect may be due to inhibition of the synthesis of the arachidonic acid metabolite (vane, 1987). thermal painful stimuli are known to be selective to centrally, but not peripherally, acting analgesic drugs (chau, 1989). in the present study, morphine (5 mg/kg), a centrally acting analgesic drug, produced a significant (p<0.001) inhibitory effect on the nociceptive response in this test while ethanol extract of a. indica and peripherally acting analgesic drug, diclofenac sodium a failed to affect the response. this result indicates that probably a. indica doesn't contain any active constituents to act against pain, which is originated from cns. the ethanol extract of the leaves of a. indicia also showed appreciable antipyretic effect (up to 70%) on rats. this effect might be due to inhibition of the synthesis of prostaglandin e2 which is described as key mediator of fever (dascombe, 1985). the presence of flavonoids, tannins, alkaloids and tetranortriterpenes, including nimbin, nimbinin, nimbidinin, nimbolide and nimbidic acid in the leaves extract of this plant (basks, 1968) may be responsible for the anti-inflammatory, analgesic and antipyretic property demonstrated by a. indica, as these phytochemicals are well-known for their ability to inhibit inflammation, pain and fever (biswas et al., 2002; ferrandiz and alcaraz, 1991; brasseur, 1989). moreover, recent research findings revealed that nimbidin significantly suppresses some of the functions of macrophases and neutrophils and also inhibited nitric oxide (no) and prostaglandin e2 (pge2) production relevant to the inflammatory response (kaur et al., 2004). so, it is not unreasonable to speculate that nimbidin and related compounds like nimbidinin, nimbolide of a. indica leaf extract are probably responsible for its anti-inflammatory, analgesic and antipyretic effects. table v. effect of ethanol leaves extract of a. indica on yeast-induced pyrexia in rats. treatment dose rectal temperature (oc) rectal temperature after administration of drug (oc) initial 10th hour after 1st hr 2nd hr 3rd hr (a) yeast (c1) (c2) (c3) administration (b) control 37.61 ± 0.17 38.30 ± 0.16 38.29 ± 0.12 38.28 ± 0.15 38.27 ± 0.08 (1.4%) (1.61%) (3.63 %) paracetamol 100 mg/ kg 37.44 ± 0.14 38.10 ± 0.15 37.70 ± 0.17** 37.62 ± 0.14** 37.50 ± 0.12** (61%) (73.2%) (91.5%) a. indica ethanol 1 g/kg 37.7 ± 0.2 38.22 ± 0.18 38.0 ± 0.2* 37.9 ± 0.18* 37.85 ± 0.17** extract (41.7%) (60.4%) (69.8%) a. indica ethanol 500 mg/ kg 37.69± 0.2 38.44 ± 0.18 38.2 ± 0.18 38.12 ± 0.18* 38.00 ± 0.18* extract (30.3%) (40.3%) (55.1%) a. indica ethanol 100 mg/ kg 37.50 ± 0.2 38.2 ± 0.18 38.3 ± 0.18 38.10 ± 0.18 38.05 ± 0.18 extract (10.0%) (22.8%) (29.3%) all values are expressed as mean ± sem (n=5) * p<0.05 and ** p<0.01 significant compared to control percentage reduction in rectal temperature is given within parentheses b-cn% reduction=------------------------x 100; where n=1, 2, 3 b-a zaman, ahmed, akter, ahmed, aziz and ahmed. 205 conclusion the ethanol extract of the leaves of a. indica shows a significant anti-inflammatory (both acute and chronic), peripheral analgesic and antipyretic effects in experimental animal models and could be an alternative source to treat inflammation, arthritis, pain and fever. however, further studies are necessary to elucidate the mechanism behind this effect. this report may serve as a footstep on this aspect. acknowledgement the authors are grateful to dr. md. yousof, c.s.o. bcsir laboratories, chittagong for his useful advice and identification of plant for the study. we also extend our thanks to md. rafique uddin chowdhury, mohammad mostafa, abdul auwal khandakar, technician of drugs and toxins division for preparation of extracts and maintenance of animals. references adams s. s., hebborn p., and. nicholson j. s. (1968) some aspects of the pharmacology of ibufenac, a nonsteroidal anti-inflammatory agent. j. pharm. pharmac. 20: 305-312. ahmad f., khan r. a., and rasheed s. (1992) study of analgesic and anti-inflammatory activity from plant extracts of lactuca scariola and artemisia absinthium. j. islam. aca. sci. 5: 111-114. arrigoni-maratellie e. (1988) inflammation antiinflammatory. (spectrum publication inc, new york) pp 119120. basak s. p., and chakraborty d. p. (1968) chemical investigation of azadirachta indica leaf (melia azadirachta). j. indi. chemi. soc. 45: 466 467. brasseur t. (1989) antiinflammatory properties of flavonoids. j. pharm. belg. 44: 235-41. biswas k., chattopadhyay k., banerjee r. k, and bandyopadhyay, u. (2002) biological activities and medicinal properties of neem (azadirachta indica). curr. scien. 82:1336-1345. chatterjee g. k., and pal s. p. (1984) search for anti-inflammatory agents from indian medicinal plants. indi. drug. 21: 413. crunkhon p., and meacock s. e. r. 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(1976) cotton pellet granuloma method for evaluation of antiinflammatory activity. arch. intern. pharmacodyn. therap. 165: 294-301 hendershot l. c., and forsaith j. (1959) antagonism of the frequency of phenylquinone-induced writhing in the mouse by weak analgesics and nonanalgesics. j. pharmacol. exp. ther. 125: 237-240. ismail t. s., gapalakrisan s., begum v. h., and elango v. (1997) anti-inflammatory activities of salacia oblonga wall and azima tetracantha lam. j. ethnopharmacol. 56: 145-152. koster r., anderson m., and de beer e. j. (1959) acetic acid for analgesic screening. fed. proc. 18: 412. kaur g., sarwar-alam m., and athar m. (2004) nimbidin suppresses functions of macrophages and neutrophils: relevance to its antiinflammatory mechanisms. phytother. res. 18: 419-24 khanna n., goswami m., sen p., and ray a. (1995) antinociceptive action of azadirachta indica (neem) in mice: possible mechanisms involved. indian. j. exp. biol. 33: 848-50. olajide o. a., awe s. o., makinde j. o., ekhelar a. i., olusola a., morebise o., and okpako d. t. (2000) studies on the anti-inflammatory, antipyretic and analgesic properties of alstonia boonei stem bark. j. 206 studies on anti-inflammatory, antinociceptive 44(2) 2009 ethnopharmacol. 71:179-186. pillai n. r., suganthan d., seshadri c., and santhakumari g. (1978) analgesic and anti-pyretic actions of nimbidin. bull. med. ethno. bot. res. 1: 393-400. pillai n. r., and santhakumari g. (1981) anti-arthritic and anti-inflammatory actions of nimbidin. planta. medica. 43: 59-63. recio m. c., giner r. m., manez s., and ros j. l. (1995) structural requirements for the anti-inflammatory activity of natural triterpenoids. planta. med. 6: 182185. swingle k. f., and shideman f. e. (1972) phases of inflammatory response to subcutaneous implantation of cotton pellet and other modifications by certain anti-inflammatory agents. j. pharmacol. exp. ther. 183: 226-234. underwood j. c. e. (2000) general systematic pathology. 3rd ed. (churchill livingstone, new york) pp 201. vinegar r., schreiber w., and hugo r. (1969) biphasic development of carrageenan edema in rats. j. pharmacol. exp. ther. 166: 96-103. vane j. (1987) the evolution of non-steroidal anti-inflammatory drugs and their mechanisms of action. drug. 1: 18-27. winter c. a., risley e. a., and nuss g. w. (1962) carrageenin-induced edema in hind paws of the rat as an assay for antiinflammatory drugs. proc. soc. exp. biol. med. 111: 544-547. woolfe g., and macdonald a. d. (1944) the evaluation of the analgesic action of pethidine hydrochloride (demerol). j. pharmacol. exp. ther. 80: 300-307. received : march, 30, 2008; accepted : october 15, 2008. file 2309 (1).qxd arsenic removal efficiencies of a few impregnated silicate meterials m. f. islam and m. mokhlesur rahman department of applied chemistry and chemical technology university of rajshahi, bangladesh abstract the commonly available brick particles were impregnated with selected compounds and tested for as absorption properties. the materials tested are feso4 treated roasted brick particles, fe2(so4)3 treated roasted brick particles, feso4 and na2co3 treated brick particles, fe2(so4)3 and na2co3 treated brick particles, znso4 and na2co3 treated brick particles, feso4 and na2hpo4 treated brick particles and waste cement plaster as such. it was observed that the substances showed different behavior of as absorption on short and long time contact. on long time contact periods the absorption capacities are much increased with high concentrations of as in solution. however with short time contact with low as concentration, the materials show saturation or no absorption after certain time period. thus variable capacities for as absorption are shown depending on concentration, time of absorption and interval time between two contact periods. as (iii) absorption was studied in the ph range 2.45-7.0. the data also show that with a contact time of 3 hrs. or more, the level of as is reduced to the acceptable limit of 0.05 ppm in water. high concentration of phosphate in water decreases as absorption as phosphate is also strongly absorbed by iron oxide impregnated brick particles. leaching of loaded arsenic from brick particles using different common chemicals was also studied for ferrous sulfate treated roasted brick particles. out of the solutions of common chemicals (10 % caustic soda, 20% sodium chloride, 10 % sodium carbonate, 10 % potassium dihydrogen phosphate, 10% tsp and 5 % nh3) only 10 % caustic soda can leach ~ 95 % as from as loaded brick particles and others much less. ordinary water within ph 4-7 leach very little arsenic from iron oxide impregnated brick particles. bangladesh j. sci. ind. res. 41(1-2), 1-14, 2006 introduction the problem of as contamination in water has inspired many scientists and technologists for the study of substances for the purpose of removal of arsenic from contaminated water. different systems have been proposed. out of the several methods, arsenic removal by coagulation and absorption only has assumed importance in view of the applicability in both the industrial and household levels. the coagulation of arsenic contaminated water by alum and ferric chloride is an established method though having difficulties in removing as in different situations.1,2 adsorption methods have assumed importance in view of the reported adsorption properties of different substances for as, such as iron impregnated river sands, green sands and some composite materials.3-6 a study was initiated in this laboratory on the effectiveness of brick particles (crushed bricks) for removal of arsenic from water after impregnation with iron oxides. this paper reports further work on the as absorption properties of brick particles after modification with selected inorganic compounds and of waste cement plasters as such. by the term silicate materials is understood the commonly available substances in which silica is a major component. the chemistry of the absorption process is yet to be investigated. the purpose of the work was to identify very cheap materials for the making of arsenic filters for the poor. leaching experiments were done on a selected arsenic absorbed (loaded) material from environmental impact consideration. the effect of the co-existing interfering phosphate ion was also investigated. materials and methods preparation of materials for this investigation, ordinary locally made bricks properly burned (first class bricks) and old waste cement plaster were collected and used for study. at first these materials were crushed into small sizes. of which only (-3.15+2) mm mesh and (-2+0.2) mm mesh sizes were taken for experiments. then the fixed sized crushed bricks and waste silicate materials were treated by the following methods. the chemicals used for treatment are ferruos sulfate, ferric sulfate, zinc sulfate, disodium hydrogen phosphate, sodium carbonate etc. a) feso4 treated roasted brick particles 200 g crushed brick particles were soaked with freshly prepared 20 % feso4 solution for 24 hours. 250 ml. solution was used for 200 g crushed brick. then the feso4 impregnated wet crushed brick particles were taken in a clay pot for heat-treatment in a make shift furnace after draining out excess solution. in this experiment an electric heater of 2 kw was used whose surrounding was closed by brick walls with clay as mortar to minimize the loss of heat. a thermometer was used to record the temperature. soaked crushed brick was heated for three hours at around 450o c-500o c, feso4 being converted to oxides of iron. this iron oxide impregnated brick particles were used for investiga2 arsenic removal efficiencies of a few impregnated 41(1-2) 2006 tion. the thermal decomposition reaction of ferrous sulfate is well known. b) feso4 and na2co3 treated brick particles 200 g crushed brick particles were soaked with freshly prepared 250 ml. of 10% feso4 solution for 24 hours and filtered in order to drain out the excess feso4 solution and soaked brick particles were dried in the sun. then the dried 10 % feso4 soaked brick particles were again soaked with 250 ml. of 10 % na2co3 solution for 24 hours. then the brick particles were filtered, washed free of sulfate and dried in the sun. hydrated ferric and ferrous oxides are formed by the decomposition of unstable ferrous carbonate . c) fe2(so4)3 treated roasted brick particles 200 g crushed brick particles were soaked with 250 ml. of 10 % fe2(so4)3 solution for 24 hours and filtered, and dried. it was then heated for an hour and a half using the same electric make shift furnace at temperatures ~ 450o c. the impregnated brick particles were used for subsequent study. the decomposition of hydrated ferric sulfate is also a well known reaction. d) znso4 and na2co3 treated brick particles 200 g crushed brick particles were soaked with 250 ml. of 10 % znso4 solution for 24 hours and then filtered, and dried in the sun. then the 10 % znso4 soaked dried brick particles were soaked with 250 ml. of 10 % na2co3 solution for 24 hours and then filtered, washed free of sulfate and dried in the sun. the basic zinc carbonate is formed insitu by the reaction. znso4 + na2co3 + h2o znco3 . 2 zn(oh)2 . h2o + na2so4. e) fe2(so4)3 and na2co3 treated brick particles 200 g crushed brick particles were soaked with 250 ml. of 10 % fe2(so4)3 solution for 24 hours and then filtered, and dried in the sun. then the 10 % fe2(so4)3 soaked brick particles were soaked with 10 % na2co3 solution for 24 hours then filtered, washed free of sulfate and dried in the sun and collected. the hydrated ferric oxide is formed. f) feso4 and na2hpo4 treated brick particles 200 g crushed brick particles were soaked with 250 ml. of 10 % feso4 solution for 24 hours and then filtered and dried in the sun. then the 10 % feso4 soaked brick particles were again soaked with 250 ml. of 10 % na2hpo4 solution for 24 hours and then filtered, washed free of sulfate and dried in the sun. ferrous phosphate is formed insitu by double decomposition. g) waste cement plasters waste cement plasters (sandcement ratio 1:4) were collected and sorted to get the sand cement composite avoiding paint layer or adhering brick splinters. it was crushed to the desired sizes, washed several times with clean water and dried in the oven at 100o c. islam and rahman 3 the ph of the old waste cement plasterwater mixture was around 7-8 ensuring complete setting of cement. the sandcement ratio : 1 : 4 ensures proper hardness of the particles. analytical a) analysis of prepared materials for fe content the finely powdered brick was treated with concentrated hydrochloric acidhydro fluoric acid mixture (5 : 1) for an hour and a half at 95o c. after complete decomposition, the solution obtained was analyzed by colorimetric thiocyanate method for the determination of total iron. estimation of iron in the waste cement plasters was done after decomposition with concentrated hydrochloric acid only. the data for iron content are given in the table i. b) analysis of arsenic in water water samples were tested for as content by the silver-diethyldithiocarbamate spectro photometric method using the spectrophotometer ana-75 (tokyo photoelectric co.).7 in the analysis as free zn and reagents were used. c) analysis of phosphate in water the phosphate was determined by ammonium molybdate-hydrazine method.7 however instead of k-antimonyl tartrate, na-k tartrate was used for silicate interference. satisfactory results obtained. the analysis of all samples (liquids and solids) were done in duplicate and the average is reported. absorption tests the absorption tests of the materials were made primarily to get information as to the rapidity of the arsenic absorption by the materials from water solutions and the capacity of the materials for arsenic absorption. the rapidity of the absorption process is expected to vary for different materials. the capacity of the materials for arsenic uptake from water determines the volume of water treatable by these materials. both these 4 arsenic removal efficiencies of a few impregnated 41(1-2) 2006 table i. data for iron content in chemically treated and untreated crushed brick particles and waste cement plasters. arsenic absorbing materials brick particles feso4 treated roasted brick particles fe(so4)3 treated roasted brick particles waste cement plasters znso4 and na2co3 treated brick particles fe2(so4)3 and na2co3 treated brick particles feso4 and na2hpo4 treated brick particles percentage of iron content 4.75 10 7.0 1.37 6.6 8.0 7.0 factors are important for the actual design of arsenic filters. the actual capacity may not be obtained in a short time test. the ultimate capacity may be dependent on the concentration of arsenic in water, the equilibration time and also the interval time especially for the iron-oxide impregnated particles. tests were performed to determine the short time and long time capacity for the materials. test solutions were 1.0 ppm as (iii) and 4.0 ppm as (iii) which are much higher than the arsenic concentration encountered in ground water. very high concentration was used for long time capacity tests. capacity is expressed as as absorbed per kg of the materials. only as (iii) solutions are used in the absorption experiments as ground water contain larger proportion of as (iii). the loading of the materials with arsenic is similar in principle to the determination of the capacity of ion-exchangers. a) time dependence of arsenic absorption by the materials 20 g of (-3.15+2) mm and 20 g of (-2+0.2) mm mesh size materials were taken separately in same size glass beakers respectively and washed with distilled water to remove all fine particles and dust. after complete drainage of adhering water, the material was immersed in 100 ml. of 1.0 ppm as (iii) prepared solution (ph = 6.5). the mixture of materials and solution was agitated by an electric stirrer avoiding high stirring speed. after the first tweenty minutes stirring, 10 ml. of as solution was withdrawn and arsenic concentration of the solution was determined by sddc method.7 this test process was repeated after the 2nd 20 min., 3rd 20 min., 4th 20 min., 5th 20 min. and 6th 20 min. for the total absorption period of 120 minutes. the different portions were analysed for as concentration. the total as absorption was determined. fig. 1 and 2 indicate the time dependence of absorption of as of the materials. b) ultimate absorption capacity of the materials for short time arsenic absorption at moderately high arsenic concentration for short interval time between consecutive absorption tests the selected sizes of prepared 20 g materials were taken in different beakers and 100 ml. of 4.0 ppm (ph = 3.45) as (iii) prepared solution was added in each beaker for each experiment. the individual prepared mixture of material and as (iii) solution were agitated by an electric stirrer avoiding high stirring speed. after the first 1.0 hour stirring, as (iii) solution was withdrawn for the determination of as concentration. after the 1.0 hour absorption, the remaining as solution filtered out and the materials were dried in the air for the next experiment. after the 1.0 hour interval time, fresh 100 ml. of 4.0 ppm as (iii) solution added to the material and stirred as before for 1.0 hour. this process was repeated consecutively for the 3rd 1.0 hr to 12th 1.0 hr. period, each time a portion of solution being withdrawn for analysis maintaining the interval time between two absorption experiments at 1.0 hour. the different portions of solution were analysed for as concentration. islam and rahman 5 amount of arsenic absorbed by the material in each time period was calculated from the change in as concentration. the maximum cumulative absorption capacity for as (iii) per kg of materials was determined. the cumulative amount of arsenic absorbed after the 12th 1 hr. period is given for the two sizes of the materials tabel ii. c) ultimate absorption capacity of the materials for long time arsenic absorption and long interval time between two consecutive experiments for different very high arsenic concentration. experimental procedure is same as before, but 40.0 ppm (ph = 3.40), 120 ppm (ph = 3.25) and 200 ppm (ph = 3.08) of as (iii) prepared solution was used. absorption period was 64 hours and interval time between two consecutive experiments was 24 hours. for each experiment different portions of solution were analysed as before for as concentration and maximum absorption capacity of the materials for as (iii) per kg material was calculated table ii. d) effect of phosphate in water phosphate may be present in tube well water. therefore to observe the effect of phosphate on arsenic absorption by the material, the test (a) was repeated with solution of as (iii) 6 arsenic removal efficiencies of a few impregnated 41(1-2) 2006 table ii. ultimate absorption capacities for as (iii) of different materials under different loading conditions materials feso4 treated roasted brick particles fe(so4)3 treated roasted brick particles znso4 and na2co3 treated brick particles feso4 and na2co3 treated brick particles fe2(so4)3 and na2co3 treated brick particles feso4 and na2hpo4 treated brick particles short time absorption, interval time 1.0 hr., moderate as concentrations. ph=3.45 capacity=gmas/kg materials (-3.15+2)mm mesh size 0.1131 0.097 0.0862 0.0955 0.0702 0.064 (-3.15+2)mm mesh size 0.926 0.749 0.693 0.818 0.787 0.773 (-2+0.2)mm mesh size 0.844 0.556 0.546 0.556 0.584 0.574 long time absorption, 24 hrs. interval,high as concentrations. ph=2.45 capacity=gm as/kg materials (-2+0.2)mm mesh size 0.098 0.086 0.073 0.0855 0.060 0.0597 with different amounts of phosphate in the mixed solution for absorption by (-3.15+2) mm mesh feso4 treated roasted brick particles. the aliquots were analysed for as and phosphate concentration for the total as and phosphate absorption from the aqueous phase at predetermined time intervals. the amount of as and phosphate absorbed after 120 minutes total time are given in table iii for the feso4 treated roasted brick particles only. leaching of absorbed as (iii) by different reagents the following experiments were performed to find out the effect of commonly used chemicals on the as absorbed brick particles. principally leaching experiments were done on the as absorbed brick as to predict any possible leaching of as in the environment and the possibility of recovery of as from brick particles. the commonly used chemicals that may be encountered in the field conditions are na2co3 used as washing soda, nacl used always in the domestic environment, tsp and kh2po4 may be used as fertilizer in the village lands. their action on as absorbed brick sands is useful for predicting for possible environmental impacts. also the strong alkali was used for possible as recovery from arsenic loaded brick particles. 20 g of (-3.15+2) mm mesh as loaded material were taken in different beakers. then islam and rahman 7 table iii. arsenic absorption by feso4 treated roasted brick particles in absence and in presence of low and high concentration of phosphate in water weight of brick particles taken = 20 g size = (-3.1+2) mm mesh volume of solution taken for absorption = 100 ml. initial as content in solution = 1.0 ppm initial phosphate contents in solution = 0.0 ppm, 6.0 ppm and 10.0 pmn. absorbing material feso4 treated roasted brick particles phosphate concentration in solution (ppm) 0.00 6.00 10.00 absorpti on period minutes 120 120 120 as content in solution after absorption (ppm) 0.02 0.04 0.16 for arsenic absorption for phosphate absorption total % of as absorption from solution 98 96 84 total as absorption (mgm as/ kg brick sands) 4.9 4.8 4.2 phosphate concentration in solution after absorption (ppm) 0.0 0.0 percentage phosphate absorption 100 100 8 arsenic removal efficiencies of a few impregnated 41(1-2) 2006 table iva. time dependence of leaching of loaded as from feso4 treated roasted brick particles with naoh solution weight of brick particles taken in a beaker = 20 g size of the brick particles taken = (-3.15+2) mm mesh concentration of the leaching solution = 10 % naoh volume of solution taken for leaching of as = 100 ml. ph of the solution = 14.0 absorbing material feso4 treated roasted brick leaching period (minutes) 20 40 60 80 100 120 actual as concentration in leach (ppm) 85.0 105.0 135.0 160.0 160.0 160.0 total amount of as in brick particles, g (in 20 g) 168.8 x 10-4 % leached as in solution 50.35 62.20 79.97 94.78 94.78 94.78 table ivb. leaching of loaded as from feso4 treated roasted brick particles using tsp (triple super phosphates) solution weight of brick particles taken in a beaker = 9 g size of the brick particles taken = (-3.15+2) mm mesh concentration of the leaching solution = 10 % tsp volume of solution taken for leaching of as = 100 ml. ph of the solution = 2.97 absorbing material feso4 treated roasted brick leaching period (minutes) 20 40 60 80 100 120 actual as concentration in leach (ppm) 2.5 3.0 7.5 15.0 26.25 26.25 total amount of as in brick particles, g (in 20 g) 75.96 x 10-4 % leached as in solution 3.29 6.58 9.87 19.74 34.56 34.56 100 ml. each of 10 % naoh, 20 % nacl, 10 % na2co3, 10 % kh2po4, 10 % tsp and 5 % nh3 was added to each beaker for each experiment. the mixture of arsenic loaded materials and added leaching solution was agitated by an electric stirrer. after the first 20 min stirring 2.0 ml of the solution was withdrawn to determine as concentration in leach solution. this process was repeated for the consecutive 20 minutes for the total time of 120 minutes. after total 120 minutes leaching the actual as in leached solution was determined and the % as leached was calculated. out of the chemicals used for leaching studies, detailed data for the naoh and tsp only are given in the table iva and table ivb for iron oxide impregnated brick particles. leaching data for other common reagents are given in abbreviated form in table v. results and discussion it is observed from the figs. 1 and 2 that minute quantities of as in water or solution may be absorbed by untreated ordinary brick particles and ordinary waste cement plasters, but absorption process is very slow for brick suggesting that ordinary brick is unsuitable for absorption arsenic from water or solution but waste cement plasters is much more suitable. after 2 hours absorption period the untreated ordinary brick particles reduced arsenic level to 0.20 ppm as from 1.0 ppm as solution whereas waste cement plasters reduced it to zero ppm as from 1.0 ppm as solutionin the same time period. the experiments showed that bricks should be modified chemically to enable them to act as absorber for as from water or solution and waste plasters can be used for arsenic removal as such. the arsenic absorption properties of cement composites is also reported recently.8 it was found that the absorption process is much faster for the modified brick particles. after 120 minutes absorption period as concentration in aqueous solution was down to the permissible limit of 0.05 ppm. it can be concluded that fe-impregnated bricks are more active to absorb arsenic from water or solution than the ordinary bricks because of higher iron content (10 % fe). the increase of iron content in materials also increase as absorption capacity of the materials. this phenomenon suggests that the absorption of as by impregnated materials may occur by adsorption or chemisorption process at the surfaces of the particles and pores in the body of materials where oxides may be deposited. it is seen that rapid absorption is observed for the first 20 minutes and after that the absorption process is slowed. almost 80 % as is absorbed in the first 20 minutes. more time is necessary to decrease the level of as to less than 0.05 ppm. the phenomena can be explained by assuming that in the initial period the arsenic is absorbed by the surface deposited oxides and hydroxides and in the later period the as ions has to diffuse to the interior of the particles. the results obtained for different sizes of materials are shown graphically. the sizes selected for the study give almost the same level of arsenic (iii) absorbing capability for single contact. however the absorption properties of zinc hydroxide impregnated brick particles are islam and rahman 9 10 arsenic removal efficiencies of a few impregnated 41(1-2) 2006 fig. 1. variation of as absorption by different materials [(-3.15+2) mm mesh size], with time. fig. 2. variation of as absorption by different materials [(-2+0.2) mm mesh size], with time. almost similar to the iron oxide impregnated brick whereas iron phosphate impregnated brick particles has lower ability of arsenic absorption. impregnation with iron hydroxide by ferrous sulfate-sodium carbonate treatment is much less effective. the better absorption capability is shown by the ferrous and ferric sulfate impregnated roasted brick particles than the iron phosphate impregnated. for 120 minutes absorption period, arsenic absorbed from low as concentration (1.0 ppm) solution by materials are given below for the given ph value in a single contact. thus impregnation with iron oxides increases the absorption capacities of ordinary brick particles by 4-5 times. however the rates of as absorption in the initial 20 minutes determines the rapidity of as removal. in this regard zinc treated and the iron sulfate treated and roasted brick particles are much faster. however the maximum absorption is not achieved in a single contact as shown latter. ultimate absorption capacity of the materials for short and long time arsenic absorption at moderate to high arsenic concentration. the absorption properties of the materials for longer time use in particular conditions may be different. it was found that for treated bricks the absorption properties, specially the capacity, is dependent on the total time of contact and the concentration of as level. single contact does not show the real capacity of the materials for arsenic absorption. the previous experiment does not show the real capacity as the material will again absorb arsenic from water if contacted with fresh arsenic solution showing the same time dependence. it was also observed that the interval time between two contacts also influences the total capacity of absorption of arsenic. in the short tine contact the interval was fixed at 1 hour and in the long time contact the interval time was 24 hours. short time absorption data show that after 7 hours or more total absorption time, the materials absorbed maxislam and rahman 11 materials brick particles untreated ordinary brick particles feso4 treated roasted fe2(so4)3 treated roasted znso4 and na2co3 treated feso4 and na2co3 treated fe2(so4)3 and na2co3 treated feso4 and na2hpo4 treated total amount of absorbed as for (3.15+2) mm mesh brick particles. (mg as/kg brick sands) ph=6.5 1.0 4.8 4.9 4.7 4.7 3.725 3.1 total amount of absorbed as for (-2+0.2) mm mesh brick particles. (mg as/kg brick sands) ph=6.5 0.35 4.75 4.75 4.675 4.67 3.575 3.025 imum as and this was the maximum absorption capacity of the materials in the short time contact with 1 hour interval condition. capacity was determined in terms of as absorbed per kg of materials. the experimental data showed that almost 50 % of the total capacity was used up in the first 3 contacts. there after slow absorption occurred in the subsequent periods. long time arsenic absorption the effect on the maximum as absorption capacity of the materials for long time as absorption period and very long interval time between two consecutive absorption of as from solution was investigated. the reason for such study is that as absorption process may be totally different involving not the surface only, but also the total mass of the particles with its internal pores. longer contact time and longer interval time between two contacts together with higher as concentration make available the internal pores of the particles for as absorption. it was thought that such experimental conditions will give necessary time and driving force for the utilization of unused pores for the as absorption. moreover unknown chemisorptions process may also take place in long time contact. longer interval time may give time for the diffusion of surface absorbed species to migrate to internal pores of the materials. the active materials is expected to be deposited in the pores of the brick particles that should have very large pore surface. from the data table ii it is observed that after 256 hours absorption period the material was fully loaded with as and after the 4th 64 hour absorption period the material did not absorb any more arsenic from solution. cumulative maximum absorption capacity was determined in terms of as absorbed per kg of the material. it is evident that ultimate absorption capacity can be reached only with longer contact time. the ultimate capacity is almost 10 times greater for the larger particle size for long time contact and long interval time for the ph range used for the solutions. effect of phosphate the phosphate ion and arsenate/ arsenite ion coexist in many ground water. in some places phosphate may be present in concentrations much higher than the arsenic concentration. it is necessary to see the effect of high concentration of phosphate on arsenic absorption. such tests were done only on iron oxide impregnated brick particles using ferrous sulfate. the effect of 0.0 ppm, 6.0 ppm and 10.0 ppm of phosphate in solution on arsenic absorption is shown table iii. the data clearly indicates the competing effect of phosphate in the absorption process. the higher relative absorption of phosphate fro mixed solution is shown from the iron oxide impregnated brick. the effect is shown graphically in fig. 3. it may be predicted that the presence of high concentration of phosphate in water or solution will decrease arsenic absorption capacity of the materials for long time use. thus the filters designed for arsenic removal is not expected to run properly in areas where the ground water phosphate concentration is high as phosphate will soon saturate the 12 arsenic removal efficiencies of a few impregnated 41(1-2) 2006 absorbing material in view of the greater affinity of the phosphate. however as iron phosphate impregnated brick prticles also absorb arsenic (iii) from water, an equilibrium condition may establish with arsenic and phosphate in solid and liquid. leaching of absorbed as by different reagents the results indicate that only 10 % naoh is able to leach out ~ 95 % of as in the brick sands (table iv and v). others are not effective to leach out even 20 % of the total as absorbed by using high concentration of reagent. however 10 % tsp can leach out up to about 35 %. ordinary water in two ph ranges leach very little arsenic from the loaded brick particles. the results indicate that the arsenic is bound very strongly to the iron oxide impregnated brick particles indicating strong bond formation with the material. thus waste arsenic loaded brick particles do not pose any threat to the environment as very little of the reagents are present in the environment especially in the rural areas. only negligible quantities may be leached in the environment but the concentration of leached arsenic will be much less than the arsenic in the tube well water. studies were not made for other arsenic loaded materials but effects are expected to be similar for iron compound impregnated materials. islam and rahman 13 fig. 3. effect of phosphate concentration on as absorption table v. maximum % leaching of absorbed as from the brick particles chemicals 10 % naoh solution 20 % naci solution 10 % na2co3 solution 10 % kh2po4 10 % tsp solution 5 % nh3 solution h2o maximum % leached as 94.78 17.28 18.36 11.85 34.56 29.62 (ph = 4) 3.0 (ph = 7) 5.0 conclusion the experimental data show that the impregnated brick particles and sand-cement composites have excellent arsenic absorption properties from water. ordinary bricks and cement are in effect silicate materials manufactured from clay. impregnation with non toxic iron and zinc compounds enhances the arsenic absorption properties of brick particles. however the iron oxide impregnation may be a cheaper process than that with zinc oxide. it seems higher iron oxide percentage favor more as (iii) absorption. as (v) absorption is expected to be more favorable as literature reports better removal with other iron containing materials for the higher oxidation state of arsenic. besides the arsenic absorption capacity the kinetics of absorption and leaching characteristics suggest the suitability of iron oxide impregnated materials for practical filters. the other impregnated materials have to be studied more for practical use. the chemistry of the arsenic absorption process remains to be investigated. however a chemisorptions mechanism is more likely for iron oxide impregnated brick materials in view of the difficult leaching of arsenic from the arsenic loaded material. references 1. j. g. hering, p. y. chen, j. a. wilkie, m. elimelech and s. liang. arsenic removal by ferric chloride. journal american water works association, 88(4) (1996) 155-167. 2. j. g. hering, p. y. chen, j. a. wilkie, m. elimelech and s. liang. arsenic removal from drinking water during coagulation. journal of environmental engineering, 123(8) (1996) 800-807. 3. r. c. vaishya and i. c. agarwal. removal of arsenic (iii) from contanminated ground waters by ganga sand. journal of indian water works association, 25(3) (1993) 249-253. 4. a. joshi and m. chaudhuri. removal of arsenic from ground water by iron-oxidecoated sand. j. environ. eng. (n.y), 122(8) (1996) 769-771. 5. k. s. subramanian, t. viraraghavan, t. phommavong and s. tanjore. manganese greensand for removal of arsenic in drinking water. water quality research journal of canada, 32(3) (1997) 551-561. 6. j. hlavay, k. foldi-polyak, j. inczedy. application of new adsorbent for removal of arsenic from drinking water. (chem. prot, envioon. 1987) 119-30 (eng.) 7. a. d. eaton, l. s. clesceri, a, e. greenberg. standard methods for the examination of water and wastewater. 19th ed. 1995. 8. s. kundu, a. pal, sk ghosh, m. mandal and t. pal. removal of arsenic from water using hardened paste of portland cement. environ. technol, 25(3) (2004) 301-9. 14 arsenic removal efficiencies of a few impregnated 41(1-2) 2006 129 changes in physical properties of some proprietary safflower (carthamus tinctorius l.) cultivars after film coating application eynep dumanoğlu bingol university, faculty of agriculture, department of biosystem engineering, bingol, turkey abstract safflower is one of the economically important oil plants. there are some studies on safflower, but none on its seed properties. this study was carried out in the biosystem engineering laboratories of the faculty of agriculture of bingöl university in 2021. the seeds of four different proprietary safflower cultivars were randomly sampled, and some of their physical properties were examined under two separate groups, that is, control and film-coated. the film coating material was applied in a single layer, and its effects on the seed size were compared between the study groups. the coating dose should be at a level that will not adversely affect the germination and emergence performance of the seed. as a result of the study, it was found that the safflower seeds were long and oval in shape. this study is important in that its results will help the researchers carry out mechanization and breeding studies on safflower. keywords: safflower; carthamus tinctorius l.; seed size; film-coated *corresponding author e-mail: chiranjitpal2010@gmail.com introduction safflower (carthamus tinctorius l.), a valuable oil plant with an annual herbaceous structure, has been cultivated for about 3000 years (koç et al. 2017; culpan and arslan, 2018; baydar and erbaş, 2020). it has a high tolerance to conditions such as drought and low temperature, thanks to its behaviour in the consumption of water and nutrients in the soil depending on its root structure. due to these features, safflower is important in making use of fallow lands, controlling erosion control, and expanding cultivation areas (baydar and erbaş, 2020; esendal, 1981; bayraktar, 1991; geçit et al. 2018; köse et al. 2021). safflower is sown in two seasons, summer and winter. depending on the irrigation conditions, it can be thorny or thornless and has yellow, white, red, and orange flowers with a height of 50-150 cm. its seeds can be white, brown, striped white, and rarely black (culpan and arslan, 2018; nacar et al. 2016; toprak and tunçtürk, 2018). the flowers and seeds of the safflower plant are used in many sectors. safflower oil is used in biodiesel production as well as in the food, medicine, textile, and paint industries (kırıcı, 1998; yılmaz and tunçtürk, 2018). it is also used as animal feed and ornamental, medicinal, and aromatic plant (koç and güneş, 2021). the unsaturated fatty acids (oleic acid and linoleic acid) account for about 90% of the total fatty acid content of the safflower seed. it contains 32-34% carbohydrate, 14-15% protein, 5-8% moisture, and 2-7% ash (weiss, 2000; çoşge et al. 2007; kalafat et al. 2009). since safflower is economically valuable and durable, mechanization trials and breeding studies have been carried out to expand its cultivation areas. in these studies, it was aimed to place the seeds in the soil with the least product loss by choosing the appropriate tools, machines, and systems for the physical properties of the seeds. in addition, in breeding studies, the characteristics of seeds are important in the development of new varieties. seed technologies are used to increase the resistance of seeds to ecological conditions and increasing planting opportunities. researches are being carried out to increase seed quality through methods such as the use of plant nutrients, film coating, and pelleting. in this study, the seeds of different safflower cultivars were examined separately under two groups, control and film-coated, and some physical properties of the seeds were determined. material and method this study was carried out in the laboratories of the departments of biosystem engineering and field crops, faculty of agriculture, bingöl university in 2021. in this study, the seeds of four different safflower cultivars (balcı, dinçer, yektay, and yenice) were used as plant material. the safflower seeds were obtained from the transitional zone agricultural research institute, ministry of agriculture and forestry, republic of türkiye. the seeds were examined in two groups, control group and the film-coated group. spss v.22 statistical packages was used to analyze the data, and the tukey test was used to determine the differences. the statistical significance was set at p<0.05. in the study, a water-based polymeric material from a commercially sold brand in the market was used in the film coating application. the safflower seeds were film coated (single layer) by spraying and then dried at room temperature (approximately 24°c) in a moisture-free, dry, and dark environment for 24 hours (ista, 2007). the length (mm), width (mm), and surface area (mm2) of the seeds were measured using a stereo microscope (nikon smz 745t) (dumanoğlu and geren, 2020; dumanoğlu et al. 2021). the obtained data were evaluated according to the seed classification criteria specified in table i. the mean arithmetic diameter of the seeds (mm) (), their mean geometric diameter (mm) () and sphericity () [l: seed length (mm) w: seed width (mm)] were calculated using the data (mohsenin, 1970; alayunt, 2000; kara, 2012). in addition, 1000-grain weight was measured in triplicate randomly for both groups (dumanoğlu and öztürk, 2021). results and discussion we examined some physical properties of four different safflower cultivars under two separate groups (control and film-coated) and found that, in the control group, the seeds of the variety balcı had the highest length and surface area (7.599 mm; 22.027 mm2) and those of the variety yenice had the lowest values (6.502 mm; 18.792 mm2); the seeds of the variety dinçer had the highest width (3.721 mm) and those of the variety yektay had the lowest width (3.508 mm) (table ii) in the control group, the seeds of the variety balcı had the highest mean of both arithmetic (5.572 mm) and geometric (79.738 mm) diameter and sphericity (10.700) and those of the variety yenice had the lowest (5.062 mm; 56.458 mm; 8.589). the variety balcı was found to have the highest 1000-grain weight (40.434 g) and the variety yenice had the lowest (34.843 g) (table ii). as for the film-coated group of four different safflower varieties, it was found that the seeds of the variety balcı had the highest length (7.427 mm) and those of the variety yektay had the lowest length (6.452 mm); the seeds of the variety yektay had the highest width (3.661 mm) and the seeds of the variety yenice had the lowest width (3.503 mm); and the seeds of the variety yenice had the highest surface area (21.248 mm2) and those of the variety yektay had the lowest surface area (18.709 mm2). it was found that, in the film coated safflower cultivars, the seeds of the variety yenice had the highest mean arithmetic diameter (5.480mm) and those of the variety yektay had the lowest (5.056 mm); the seeds of the variety yenice had the highest mean geometric diameter (76.184 mm) and those of the variety yenice had the lowest (55.729 mm); and the seeds of the variety yenice had the highest sphericity (10.082) and those of the variety yektay had the lowest (8.561). in the film-coated group, the variety balcı was found to have the highest 1000-grain weight (40.562 g) and the variety yenice had the lowest (35.645 g) (table i). based on these results, it can be asserted that all the safflower seeds in the control group and the film-coated group had a long and oval seed structure. as a result of the measurement and calculation processes, it was found that the safflower varieties in the control and film coated groups had similar values in all parameters. this is primarily due to the application of a single layer film coating. there was not much difference between the coated and uncoated seeds in terms of size, and the film material did not cover the seed like a barrier. this is extremely important for germination and emergence performances. in addition, it should be noted that the seeds randomly selected for film coating were slightly smaller than those in the control group. the thousand grain weights found in this study were in agreement with those reported in previous studies. koc et al. (2017) examined the yield components of five safflower lines (106-2, 11-1, 77-1-d, 89-1-c, bdyas-9) developed by selection between 2015 and 2016 in konya and some standard safflower varieties (göktürk, balcı, linas, olas, dinçer) and reported that the 1000-grain weights of the varieties ranged from 36.5 g to 43 g. on the other hand, in their study, geçit et al. (2018) reported that the safflower varieties had a 1000-grain weight of 30-45 g. the 1000 grain weights of the safflower cultivars examined in the present study were similar to those reported in these studies.. the safflower seeds were also coated using a film coating material in order to improve their properties and quality, and the film coated seeds were compared with those in the control group. measurement and calculation processes, which form the basis for mechanization and breeding research, were carried out in this study. based on the results of the study, it can be asserted that the variety balcı in the control group and the variety yenice in the film coated group came to the fore. this study is important in that it will form a basis for future research on seeds of oil plants. acknowledgement i would like to thank assoc. dr. arzu köse and the forestry transitional zone agricultural research institute, ministry of agriculture and forestry, republic of turkiye for their support in the supply of the safflower seeds. referances alayunt fn (2000), biyolojik malzeme bilgisi, ege üniversitesi ziraat fakültesi tarım makineleri bölümü ders kitabı, ege üniv. ziraat fak. yayınları no: 541. baydar h and erbaş s (2020), our native and national safflower varieties: olein, zirkon and safir. ziraat fakültesi dergisi türkiye. ulusal 1. uluslararası tarla bitkileri kongresi (özel sayı): 13: 233-237. bayraktar n (1991), seçilmiş bazı aspir (carthamus tinctorius l.) döllerinde tohum verimi, yan dal sayısı ve tabla sayısının belirlenmesi. ankara üniversitesi ziraat fakültesi yayınları, ankara, 17 s. culpan e and arslan b (2018), effects of applications salicylic acid on seed yield and some quality traits of safflower cultivars (carthamus tinctorius l.). akademik ziraat dergisi 7(2): 173-178. çoşge b, gürbüz b and kıralan m (2007), oil content and fatty acid composition of some safflower (carthamus tinctorius l.) varieties sown in spring and winter, international journal of natural and engineering sciences. 1(3):11-15. dumanoğlu z and geren h (2020), an investigation on determination of seed characteristics of some gluten-free crops (amarantus mantegazzianus, chenopodium quinoa willd., eragrostis tef [zucc] trotter, salvia hispanica l.). turkısh journal of agriculture-food science and technology 8(8): 1650-1655. dumanoğlu z, çaçan e and kökten k (2021), determination of physical properties seeds of sainfoin (onobrychis viciifolia scop.) genotypes, journal of anatolian environmental and animal sciences 6(1): 18-24. dumanoğlu z and öztürk g (2021), a research on improving seed quality (pelleting) in true potato of 101 (nif) genotype, fresenius environmental bulletin 30(09): 10983-10968. esendal e (1981), aspir’de değişik sıra aralıkları ile farklı seviyelerde azot ve fosfor uygulamalarının verim ve verimle i̇lgili bazı özellikler üzerine etkileri. tez. atatürk üniversitesi, ziraat fakültesi, erzurum. geçit hh, çiftçi cy, emeklier hy, i̇kincikarakaya sü, adak ms, kolsarıcı ö, ekiz h, altınok s, sancak c, sevimay cs and kendir h (2018), field crops. ankara university faculty of agriculture publications. publication no: 1643, ankara. international rules for seed testing (ista), (2007), international rules for seed testing book. koç h, güneş a and aydoğan s (2017), evaluation of yield and yield components of safflower lines developed by selection in konya conditions. ksu j nat. sci. (spesial ıssue) 181-185. kırıcı s (1998), effects of gıbberellıc acıd (ga3) on agronomıc traıts, flower yıeld and dye content of safflower cultıvars, tarla bakileri merkez araştırma enstitüsü dergisi. 7(1): 10-30. köse a, koşar fç and bilir ö (2021), mutasyon ıslahı ile geliştirilmiş bazı aspir (carthamus tinctorius l.) hatlarının tarımsal performansları, turkısh journal of agricultural and natural sciences 8(2): 262-273. doi: org/10.30910/turkjans.685982 kalafat s, karakaya a, kaya m. and bayramin s (2009), a preliminary study on the reactions of safflower genotypes to rüşt disease, plant protection bulletin. 49(4): 183-187. koç h and güneş a (2021), determining the relationships between flower yield and some morphological traits in safflower genotypes, turkısh journal of nature and science 10(1): 90-95. kara m (2012), biyolojik ürünlerin fiziksel özellikleri, atatürk üniv. ziraat fakültesi yayınları no: 242. mohsenin nn (1970), physical properties of plant and animal materials. gordon and breach science publishers. nacar as, değirmenci v, hatipoğlu h, taş m, arslan h, çıkman a and şakak a (2016), effects of irrigation on yield and yield components at safflower plant in harran plain condition, tarla bitkileri merkez araştırma enst. dergisi 2(özel sayı-2): 149-154. toprak t and tunçtürk r (2018), effect of salt stress on developmental performance of diffrent aspir (carthamus tinctorius l.) cultivars, journal of natural & applied sciences of east 1(1): 44-50. weiss ea (2000), safflower. in: oilseed crops, blackwell sci. ltd., victoria, australia, pp 93-129. yılmaz s and tunçtürk m (2018), determination of yield and yield components of some safflower cultivars in soil with and without tillage under muş ecological conditions, journal of the instıtute of natural & applied sciences 23(1): 69-78. doi: https://doi.org/10.3329/bjsir.v58i2.60570 received: 29 june 2022 revised: 31 july 2022 accepted: 04 august 2022 available online at www.banglajol.info bangladesh j. sci. ind. res. 58(2), 129-132, 2023 short communication investigation of changes in physical properties of some proprietary safflower 58(2) 2023126 researches are being carried out to increase seed quality through methods such as the use of plant nutrients, film coating, and pelleting. in this study, the seeds of different safflower cultivars were examined separately under two groups, control and film-coated, and some physical properties of the seeds were determined. material and method this study was carried out in the laboratories of the departments of biosystem engineering and field crops, faculty of agriculture, bingöl university in 2021. in this study, the seeds of four different safflower cultivars (balcı, dinçer, yektay, and yenice) were used as plant material. the safflower seeds were obtained from the transitional zone agricultural research institute, ministry of agriculture and forestry, republic of türkiye. the seeds were examined in two groups, control group and the film-coated group. spss v.22 statistical packages was used to analyze the data, and the tukey test was used to determine the differences. the statistical significance was set at p<0.05. in the study, a water-based polymeric material from a commercially sold brand in the market was used in the film coating application. the safflower seeds were film coated (single layer) by spraying and then dried at room temperature (approximately 24°c) in a moisture-free, dry, and dark environment for 24 hours (ista, 2007). the length (mm), width (mm), and surface area (mm2) of the seeds were measured using a stereo microscope (nikon smz 745t) (dumanoğlu and geren, 2020; dumanoğlu et al. 2021). the obtained data were evaluated according to the seed classification criteria specified in table i. the mean arithmetic diameter of the seeds (mm) (), their mean geometric diameter (mm) () and sphericity () [l: seed length (mm) w: seed width (mm)] were calculated using the data (mohsenin, 1970; alayunt, 2000; kara, 2012). in addition, 1000-grain weight was measured in triplicate randomly for both groups (dumanoğlu and öztürk, 2021). results and discussion we examined some physical properties of four different safflower cultivars under two separate groups (control and film-coated) and found that, in the control group, the seeds of the variety balcı had the highest length and surface area (7.599 mm; 22.027 mm2) and those of the variety yenice had the lowest values (6.502 mm; 18.792 mm2); the seeds of the variety dinçer had the highest width (3.721 mm) and those of the variety yektay had the lowest width (3.508 mm) (table ii) in the control group, the seeds of the variety balcı had the highest mean of both arithmetic (5.572 mm) and geometric (79.738 mm) diameter and sphericity (10.700) and those of the variety yenice had the lowest (5.062 mm; 56.458 mm; 8.589). the variety balcı was found to have the highest 1000-grain weight (40.434 g) and the variety yenice had the lowest (34.843 g) (table ii). as for the film-coated group of four different safflower varieties, it was found that the seeds of the variety balcı had the highest length (7.427 mm) and those of the variety yektay had the lowest length (6.452 mm); the seeds of the variety yektay had the highest width (3.661 mm) and the seeds of the variety yenice had the lowest width (3.503 mm); and the seeds of the variety yenice had the highest surface area (21.248 mm2) and those of the variety yektay had the lowest surface area (18.709 mm2). it was found that, in the film coated safflower cultivars, the seeds of the variety yenice had the highest mean arithmetic diameter (5.480mm) and those of the variety yektay had the lowest (5.056 mm); the seeds of the variety yenice had the highest mean geometric diameter (76.184 mm) and those of the variety yenice had the lowest (55.729 mm); and the seeds of the variety yenice had the highest sphericity (10.082) and those of the variety yektay had the lowest (8.561). in the film-coated group, the variety balcı was found to have the highest 1000-grain weight (40.562 g) and the variety yenice had the lowest (35.645 g) (table i). based on these results, it can be asserted that all the safflower seeds in the control group and the film-coated group had a long and oval seed structure. as a result of the measurement and calculation processes, it was found that the safflower varieties in the control and film coated groups had similar values in all parameters. this is primarily due to the application of a single layer film coating. there was not much difference between the coated and uncoated seeds in terms of size, and the film material did not cover the seed like a barrier. this is extremely important for germination and emergence performances. in addition, it should be noted that the seeds randomly selected for film coating were slightly smaller than those in the control group. the thousand grain weights found in this study were in agreement with those reported in previous studies. koc et al. (2017) examined the yield components of five safflower lines (106-2, 11-1, 77-1-d, 89-1-c, bdyas-9) developed by selection between 2015 and 2016 in konya and some standard safflower varieties (göktürk, balcı, linas, olas, dinçer) and reported that the 1000-grain weights of the varieties ranged from 36.5 g to 43 g. on the other hand, in their study, geçit et al. (2018) reported that the safflower varieties had a 1000-grain weight of 30-45 g. the 1000 grain weights of the safflower cultivars examined in the present study were similar to those reported in these studies.. the safflower seeds were also coated using a film coating material in order to improve their properties and quality, and the film coated seeds were compared with those in the control group. measurement and calculation processes, which form the basis for mechanization and breeding research, were carried out in this study. based on the results of the study, it can be asserted that the variety balcı in the control group and the variety yenice in the film coated group came to the fore. this study is important in that it will form a basis for future research on seeds of oil plants. acknowledgement i would like to thank assoc. dr. arzu köse and the forestry transitional zone agricultural research institute, ministry of agriculture and forestry, republic of turkiye for their support in the supply of the safflower seeds. referances alayunt fn (2000), biyolojik malzeme bilgisi, ege üniversitesi ziraat fakültesi tarım makineleri bölümü ders kitabı, ege üniv. ziraat fak. yayınları no: 541. baydar h and erbaş s (2020), our native and national safflower varieties: olein, zirkon and safir. ziraat fakültesi dergisi türkiye. ulusal 1. uluslararası tarla bitkileri kongresi (özel sayı): 13: 233-237. bayraktar n (1991), seçilmiş bazı aspir (carthamus tinctorius l.) döllerinde tohum verimi, yan dal sayısı ve tabla sayısının belirlenmesi. ankara üniversitesi ziraat fakültesi yayınları, ankara, 17 s. culpan e and arslan b (2018), effects of applications salicylic acid on seed yield and some quality traits of safflower cultivars (carthamus tinctorius l.). akademik ziraat dergisi 7(2): 173-178. çoşge b, gürbüz b and kıralan m (2007), oil content and fatty acid composition of some safflower (carthamus tinctorius l.) varieties sown in spring and winter, international journal of natural and engineering sciences. 1(3):11-15. dumanoğlu z and geren h (2020), an investigation on determination of seed characteristics of some gluten-free crops (amarantus mantegazzianus, chenopodium quinoa willd., eragrostis tef [zucc] trotter, salvia hispanica l.). turkısh journal of agriculture-food science and technology 8(8): 1650-1655. dumanoğlu z, çaçan e and kökten k (2021), determination of physical properties seeds of sainfoin (onobrychis viciifolia scop.) genotypes, journal of anatolian environmental and animal sciences 6(1): 18-24. dumanoğlu z and öztürk g (2021), a research on improving seed quality (pelleting) in true potato of 101 (nif) genotype, fresenius environmental bulletin 30(09): 10983-10968. esendal e (1981), aspir’de değişik sıra aralıkları ile farklı seviyelerde azot ve fosfor uygulamalarının verim ve verimle i̇lgili bazı özellikler üzerine etkileri. tez. atatürk üniversitesi, ziraat fakültesi, erzurum. geçit hh, çiftçi cy, emeklier hy, i̇kincikarakaya sü, adak ms, kolsarıcı ö, ekiz h, altınok s, sancak c, sevimay cs and kendir h (2018), field crops. ankara university faculty of agriculture publications. publication no: 1643, ankara. international rules for seed testing (ista), (2007), international rules for seed testing book. koç h, güneş a and aydoğan s (2017), evaluation of yield and yield components of safflower lines developed by selection in konya conditions. ksu j nat. sci. (spesial ıssue) 181-185. kırıcı s (1998), effects of gıbberellıc acıd (ga3) on agronomıc traıts, flower yıeld and dye content of safflower cultıvars, tarla bakileri merkez araştırma enstitüsü dergisi. 7(1): 10-30. köse a, koşar fç and bilir ö (2021), mutasyon ıslahı ile geliştirilmiş bazı aspir (carthamus tinctorius l.) hatlarının tarımsal performansları, turkısh journal of agricultural and natural sciences 8(2): 262-273. doi: org/10.30910/turkjans.685982 kalafat s, karakaya a, kaya m. and bayramin s (2009), a preliminary study on the reactions of safflower genotypes to rüşt disease, plant protection bulletin. 49(4): 183-187. koç h and güneş a (2021), determining the relationships between flower yield and some morphological traits in safflower genotypes, turkısh journal of nature and science 10(1): 90-95. kara m (2012), biyolojik ürünlerin fiziksel özellikleri, atatürk üniv. ziraat fakültesi yayınları no: 242. mohsenin nn (1970), physical properties of plant and animal materials. gordon and breach science publishers. nacar as, değirmenci v, hatipoğlu h, taş m, arslan h, çıkman a and şakak a (2016), effects of irrigation on yield and yield components at safflower plant in harran plain condition, tarla bitkileri merkez araştırma enst. dergisi 2(özel sayı-2): 149-154. toprak t and tunçtürk r (2018), effect of salt stress on developmental performance of diffrent aspir (carthamus tinctorius l.) cultivars, journal of natural & applied sciences of east 1(1): 44-50. weiss ea (2000), safflower. in: oilseed crops, blackwell sci. ltd., victoria, australia, pp 93-129. yılmaz s and tunçtürk m (2018), determination of yield and yield components of some safflower cultivars in soil with and without tillage under muş ecological conditions, journal of the instıtute of natural & applied sciences 23(1): 69-78. table i. classification of the seeds by their geometric haracteristics and shapes (23) geometric characteristics grain width/ grain length (b/a) (mm) long < 0.6 medium 0.6 – 0.7 short > 0.7 shapes length (a), width (b), thickness (c) (mm) round a ≈ b ≈ c oval a/3 < b ≈ c long c < b < a/3 zeynep dumanoğlu 127 researches are being carried out to increase seed quality through methods such as the use of plant nutrients, film coating, and pelleting. in this study, the seeds of different safflower cultivars were examined separately under two groups, control and film-coated, and some physical properties of the seeds were determined. material and method this study was carried out in the laboratories of the departments of biosystem engineering and field crops, faculty of agriculture, bingöl university in 2021. in this study, the seeds of four different safflower cultivars (balcı, dinçer, yektay, and yenice) were used as plant material. the safflower seeds were obtained from the transitional zone agricultural research institute, ministry of agriculture and forestry, republic of türkiye. the seeds were examined in two groups, control group and the film-coated group. spss v.22 statistical packages was used to analyze the data, and the tukey test was used to determine the differences. the statistical significance was set at p<0.05. in the study, a water-based polymeric material from a commercially sold brand in the market was used in the film coating application. the safflower seeds were film coated (single layer) by spraying and then dried at room temperature (approximately 24°c) in a moisture-free, dry, and dark environment for 24 hours (ista, 2007). the length (mm), width (mm), and surface area (mm2) of the seeds were measured using a stereo microscope (nikon smz 745t) (dumanoğlu and geren, 2020; dumanoğlu et al. 2021). the obtained data were evaluated according to the seed classification criteria specified in table i. the mean arithmetic diameter of the seeds (mm) (), their mean geometric diameter (mm) () and sphericity () [l: seed length (mm) w: seed width (mm)] were calculated using the data (mohsenin, 1970; alayunt, 2000; kara, 2012). in addition, 1000-grain weight was measured in triplicate randomly for both groups (dumanoğlu and öztürk, 2021). results and discussion we examined some physical properties of four different safflower cultivars under two separate groups (control and film-coated) and found that, in the control group, the seeds of the variety balcı had the highest length and surface area (7.599 mm; 22.027 mm2) and those of the variety yenice had the lowest values (6.502 mm; 18.792 mm2); the seeds of the variety dinçer had the highest width (3.721 mm) and those of the variety yektay had the lowest width (3.508 mm) (table ii) in the control group, the seeds of the variety balcı had the highest mean of both arithmetic (5.572 mm) and geometric (79.738 mm) diameter and sphericity (10.700) and those of the variety yenice had the lowest (5.062 mm; 56.458 mm; 8.589). the variety balcı was found to have the highest 1000-grain weight (40.434 g) and the variety yenice had the lowest (34.843 g) (table ii). as for the film-coated group of four different safflower varieties, it was found that the seeds of the variety balcı had the highest length (7.427 mm) and those of the variety yektay had the lowest length (6.452 mm); the seeds of the variety yektay had the highest width (3.661 mm) and the seeds of the variety yenice had the lowest width (3.503 mm); and the seeds of the variety yenice had the highest surface area (21.248 mm2) and those of the variety yektay had the lowest surface area (18.709 mm2). it was found that, in the film coated safflower cultivars, the seeds of the variety yenice had the highest mean arithmetic diameter (5.480mm) and those of the variety yektay had the lowest (5.056 mm); the seeds of the variety yenice had the highest mean geometric diameter (76.184 mm) and those of the variety yenice had the lowest (55.729 mm); and the seeds of the variety yenice had the highest sphericity (10.082) and those of the variety yektay had the lowest (8.561). in the film-coated group, the variety balcı was found to have the highest 1000-grain weight (40.562 g) and the variety yenice had the lowest (35.645 g) (table i). based on these results, it can be asserted that all the safflower seeds in the control group and the film-coated group had a long and oval seed structure. as a result of the measurement and calculation processes, it was found that the safflower varieties in the control and film coated groups had similar values in all parameters. this is primarily due to the application of a single layer film coating. there was not much difference between the coated and uncoated seeds in terms of size, and the film material did not cover the seed like a barrier. this is extremely important for germination and emergence performances. in addition, it should be noted that the seeds randomly selected for film coating were slightly smaller than those in the control group. the thousand grain weights found in this study were in agreement with those reported in previous studies. koc et al. (2017) examined the yield components of five safflower lines (106-2, 11-1, 77-1-d, 89-1-c, bdyas-9) developed by selection between 2015 and 2016 in konya and some standard safflower varieties (göktürk, balcı, linas, olas, dinçer) and reported that the 1000-grain weights of the varieties ranged from 36.5 g to 43 g. on the other hand, in their study, geçit et al. (2018) reported that the safflower varieties had a 1000-grain weight of 30-45 g. the 1000 grain weights of the safflower cultivars examined in the present study were similar to those reported in these studies.. the safflower seeds were also coated using a film coating material in order to improve their properties and quality, and the film coated seeds were compared with those in the control group. measurement and calculation processes, which form the basis for mechanization and breeding research, were carried out in this study. based on the results of the study, it can be asserted that the variety balcı in the control group and the variety yenice in the film coated group came to the fore. this study is important in that it will form a basis for future research on seeds of oil plants. acknowledgement i would like to thank assoc. dr. arzu köse and the forestry transitional zone agricultural research institute, ministry of agriculture and forestry, republic of turkiye for their support in the supply of the safflower seeds. referances alayunt fn (2000), biyolojik malzeme bilgisi, ege üniversitesi ziraat fakültesi tarım makineleri bölümü ders kitabı, ege üniv. ziraat fak. yayınları no: 541. baydar h and erbaş s (2020), our native and national safflower varieties: olein, zirkon and safir. ziraat fakültesi dergisi türkiye. ulusal 1. uluslararası tarla bitkileri kongresi (özel sayı): 13: 233-237. bayraktar n (1991), seçilmiş bazı aspir (carthamus tinctorius l.) döllerinde tohum verimi, yan dal sayısı ve tabla sayısının belirlenmesi. ankara üniversitesi ziraat fakültesi yayınları, ankara, 17 s. culpan e and arslan b (2018), effects of applications salicylic acid on seed yield and some quality traits of safflower cultivars (carthamus tinctorius l.). akademik ziraat dergisi 7(2): 173-178. çoşge b, gürbüz b and kıralan m (2007), oil content and fatty acid composition of some safflower (carthamus tinctorius l.) varieties sown in spring and winter, international journal of natural and engineering sciences. 1(3):11-15. dumanoğlu z and geren h (2020), an investigation on determination of seed characteristics of some gluten-free crops (amarantus mantegazzianus, chenopodium quinoa willd., eragrostis tef [zucc] trotter, salvia hispanica l.). turkısh journal of agriculture-food science and technology 8(8): 1650-1655. dumanoğlu z, çaçan e and kökten k (2021), determination of physical properties seeds of sainfoin (onobrychis viciifolia scop.) genotypes, journal of anatolian environmental and animal sciences 6(1): 18-24. dumanoğlu z and öztürk g (2021), a research on improving seed quality (pelleting) in true potato of 101 (nif) genotype, fresenius environmental bulletin 30(09): 10983-10968. esendal e (1981), aspir’de değişik sıra aralıkları ile farklı seviyelerde azot ve fosfor uygulamalarının verim ve verimle i̇lgili bazı özellikler üzerine etkileri. tez. atatürk üniversitesi, ziraat fakültesi, erzurum. geçit hh, çiftçi cy, emeklier hy, i̇kincikarakaya sü, adak ms, kolsarıcı ö, ekiz h, altınok s, sancak c, sevimay cs and kendir h (2018), field crops. ankara university faculty of agriculture publications. publication no: 1643, ankara. international rules for seed testing (ista), (2007), international rules for seed testing book. koç h, güneş a and aydoğan s (2017), evaluation of yield and yield components of safflower lines developed by selection in konya conditions. ksu j nat. sci. (spesial ıssue) 181-185. kırıcı s (1998), effects of gıbberellıc acıd (ga3) on agronomıc traıts, flower yıeld and dye content of safflower cultıvars, tarla bakileri merkez araştırma enstitüsü dergisi. 7(1): 10-30. köse a, koşar fç and bilir ö (2021), mutasyon ıslahı ile geliştirilmiş bazı aspir (carthamus tinctorius l.) hatlarının tarımsal performansları, turkısh journal of agricultural and natural sciences 8(2): 262-273. doi: org/10.30910/turkjans.685982 kalafat s, karakaya a, kaya m. and bayramin s (2009), a preliminary study on the reactions of safflower genotypes to rüşt disease, plant protection bulletin. 49(4): 183-187. koç h and güneş a (2021), determining the relationships between flower yield and some morphological traits in safflower genotypes, turkısh journal of nature and science 10(1): 90-95. kara m (2012), biyolojik ürünlerin fiziksel özellikleri, atatürk üniv. ziraat fakültesi yayınları no: 242. mohsenin nn (1970), physical properties of plant and animal materials. gordon and breach science publishers. nacar as, değirmenci v, hatipoğlu h, taş m, arslan h, çıkman a and şakak a (2016), effects of irrigation on yield and yield components at safflower plant in harran plain condition, tarla bitkileri merkez araştırma enst. dergisi 2(özel sayı-2): 149-154. toprak t and tunçtürk r (2018), effect of salt stress on developmental performance of diffrent aspir (carthamus tinctorius l.) cultivars, journal of natural & applied sciences of east 1(1): 44-50. weiss ea (2000), safflower. in: oilseed crops, blackwell sci. ltd., victoria, australia, pp 93-129. yılmaz s and tunçtürk m (2018), determination of yield and yield components of some safflower cultivars in soil with and without tillage under muş ecological conditions, journal of the instıtute of natural & applied sciences 23(1): 69-78. table ii. some physical characteristics of the seeds of the safflower varieties varieties length (mm) width (mm) surface area (mm2) avg. arithmetic diameter avg. geometric diameter sphericity thousand grain weight (g) balcı 7.599a 3.545b 22.027a 5.572a 79.738a 10.700a 40.434 dinçer 6.767b 3.721a 20.485bc 5.244b 62.876b 9.209b 38.692 yektay 7.460a 3.508b 21.247ab 5.479a 75.955a 10.072a 38.473 yenice 6.502cd 3.622ab 18.792d 5.062c 56.458cd 8.589c 34.843 avg. 7.082 3.599 20.638 5.339 68.757 9.643 38.111 stdv. 0.531 0.094 1.382 0.231 10.928 0.931 2.348 film coated balcı 7.427a 3.536b 21.151ab 5.482a 75.705a 10.075a 40.562 film coated dinçer 6.702bc 3.643ab 19.758cd 5.173bc 60.491bc 8.959bc 39.456 film coated yektay 6.452a 3.661b 18.709ab 5.056a 55.729a 8.561a 38.803 film coated yenice 7.458d 3.503ab 21.248d 5.480c 76.184d 10.082c 35.645 avg. 7.010 3.586 20.217 5.298 67.027 9.419 38.617 stdv. 0.510 0.078 1.214 0.217 10.480 0.778 2.110 investigation of changes in physical properties of some proprietary safflower 58(2) 2023128 researches are being carried out to increase seed quality through methods such as the use of plant nutrients, film coating, and pelleting. in this study, the seeds of different safflower cultivars were examined separately under two groups, control and film-coated, and some physical properties of the seeds were determined. material and method this study was carried out in the laboratories of the departments of biosystem engineering and field crops, faculty of agriculture, bingöl university in 2021. in this study, the seeds of four different safflower cultivars (balcı, dinçer, yektay, and yenice) were used as plant material. the safflower seeds were obtained from the transitional zone agricultural research institute, ministry of agriculture and forestry, republic of türkiye. the seeds were examined in two groups, control group and the film-coated group. spss v.22 statistical packages was used to analyze the data, and the tukey test was used to determine the differences. the statistical significance was set at p<0.05. in the study, a water-based polymeric material from a commercially sold brand in the market was used in the film coating application. the safflower seeds were film coated (single layer) by spraying and then dried at room temperature (approximately 24°c) in a moisture-free, dry, and dark environment for 24 hours (ista, 2007). the length (mm), width (mm), and surface area (mm2) of the seeds were measured using a stereo microscope (nikon smz 745t) (dumanoğlu and geren, 2020; dumanoğlu et al. 2021). the obtained data were evaluated according to the seed classification criteria specified in table i. the mean arithmetic diameter of the seeds (mm) (), their mean geometric diameter (mm) () and sphericity () [l: seed length (mm) w: seed width (mm)] were calculated using the data (mohsenin, 1970; alayunt, 2000; kara, 2012). in addition, 1000-grain weight was measured in triplicate randomly for both groups (dumanoğlu and öztürk, 2021). results and discussion we examined some physical properties of four different safflower cultivars under two separate groups (control and film-coated) and found that, in the control group, the seeds of the variety balcı had the highest length and surface area (7.599 mm; 22.027 mm2) and those of the variety yenice had the lowest values (6.502 mm; 18.792 mm2); the seeds of the variety dinçer had the highest width (3.721 mm) and those of the variety yektay had the lowest width (3.508 mm) (table ii) in the control group, the seeds of the variety balcı had the highest mean of both arithmetic (5.572 mm) and geometric (79.738 mm) diameter and sphericity (10.700) and those of the variety yenice had the lowest (5.062 mm; 56.458 mm; 8.589). the variety balcı was found to have the highest 1000-grain weight (40.434 g) and the variety yenice had the lowest (34.843 g) (table ii). as for the film-coated group of four different safflower varieties, it was found that the seeds of the variety balcı had the highest length (7.427 mm) and those of the variety yektay had the lowest length (6.452 mm); the seeds of the variety yektay had the highest width (3.661 mm) and the seeds of the variety yenice had the lowest width (3.503 mm); and the seeds of the variety yenice had the highest surface area (21.248 mm2) and those of the variety yektay had the lowest surface area (18.709 mm2). it was found that, in the film coated safflower cultivars, the seeds of the variety yenice had the highest mean arithmetic diameter (5.480mm) and those of the variety yektay had the lowest (5.056 mm); the seeds of the variety yenice had the highest mean geometric diameter (76.184 mm) and those of the variety yenice had the lowest (55.729 mm); and the seeds of the variety yenice had the highest sphericity (10.082) and those of the variety yektay had the lowest (8.561). in the film-coated group, the variety balcı was found to have the highest 1000-grain weight (40.562 g) and the variety yenice had the lowest (35.645 g) (table i). based on these results, it can be asserted that all the safflower seeds in the control group and the film-coated group had a long and oval seed structure. as a result of the measurement and calculation processes, it was found that the safflower varieties in the control and film coated groups had similar values in all parameters. this is primarily due to the application of a single layer film coating. there was not much difference between the coated and uncoated seeds in terms of size, and the film material did not cover the seed like a barrier. this is extremely important for germination and emergence performances. in addition, it should be noted that the seeds randomly selected for film coating were slightly smaller than those in the control group. the thousand grain weights found in this study were in agreement with those reported in previous studies. koc et al. (2017) examined the yield components of five safflower lines (106-2, 11-1, 77-1-d, 89-1-c, bdyas-9) developed by selection between 2015 and 2016 in konya and some standard safflower varieties (göktürk, balcı, linas, olas, dinçer) and reported that the 1000-grain weights of the varieties ranged from 36.5 g to 43 g. on the other hand, in their study, geçit et al. (2018) reported that the safflower varieties had a 1000-grain weight of 30-45 g. the 1000 grain weights of the safflower cultivars examined in the present study were similar to those reported in these studies.. the safflower seeds were also coated using a film coating material in order to improve their properties and quality, and the film coated seeds were compared with those in the control group. measurement and calculation processes, which form the basis for mechanization and breeding research, were carried out in this study. based on the results of the study, it can be asserted that the variety balcı in the control group and the variety yenice in the film coated group came to the fore. this study is important in that it will form a basis for future research on seeds of oil plants. acknowledgement i would like to thank assoc. dr. arzu köse and the forestry transitional zone agricultural research institute, ministry of agriculture and forestry, republic of turkiye for their support in the supply of the safflower seeds. referances alayunt fn (2000), biyolojik malzeme bilgisi, ege üniversitesi ziraat fakültesi tarım makineleri bölümü ders kitabı, ege üniv. ziraat fak. yayınları no: 541. baydar h and erbaş s (2020), our native and national safflower varieties: olein, zirkon and safir. ziraat fakültesi dergisi türkiye. ulusal 1. uluslararası tarla bitkileri kongresi (özel sayı): 13: 233-237. bayraktar n (1991), seçilmiş bazı aspir (carthamus tinctorius l.) döllerinde tohum verimi, yan dal sayısı ve tabla sayısının belirlenmesi. ankara üniversitesi ziraat fakültesi yayınları, ankara, 17 s. culpan e and arslan b (2018), effects of applications salicylic acid on seed yield and some quality traits of safflower cultivars (carthamus tinctorius l.). akademik ziraat dergisi 7(2): 173-178. çoşge b, gürbüz b and kıralan m (2007), oil content and fatty acid composition of some safflower (carthamus tinctorius l.) varieties sown in spring and winter, international journal of natural and engineering sciences. 1(3):11-15. dumanoğlu z and geren h (2020), an investigation on determination of seed characteristics of some gluten-free crops (amarantus mantegazzianus, chenopodium quinoa willd., eragrostis tef [zucc] trotter, salvia hispanica l.). turkısh journal of agriculture-food science and technology 8(8): 1650-1655. dumanoğlu z, çaçan e and kökten k (2021), determination of physical properties seeds of sainfoin (onobrychis viciifolia scop.) genotypes, journal of anatolian environmental and animal sciences 6(1): 18-24. dumanoğlu z and öztürk g (2021), a research on improving seed quality (pelleting) in true potato of 101 (nif) genotype, fresenius environmental bulletin 30(09): 10983-10968. esendal e (1981), aspir’de değişik sıra aralıkları ile farklı seviyelerde azot ve fosfor uygulamalarının verim ve verimle i̇lgili bazı özellikler üzerine etkileri. tez. atatürk üniversitesi, ziraat fakültesi, erzurum. geçit hh, çiftçi cy, emeklier hy, i̇kincikarakaya sü, adak ms, kolsarıcı ö, ekiz h, altınok s, sancak c, sevimay cs and kendir h (2018), field crops. ankara university faculty of agriculture publications. publication no: 1643, ankara. international rules for seed testing (ista), (2007), international rules for seed testing book. koç h, güneş a and aydoğan s (2017), evaluation of yield and yield components of safflower lines developed by selection in konya conditions. ksu j nat. sci. (spesial ıssue) 181-185. kırıcı s (1998), effects of gıbberellıc acıd (ga3) on agronomıc traıts, flower yıeld and dye content of safflower cultıvars, tarla bakileri merkez araştırma enstitüsü dergisi. 7(1): 10-30. köse a, koşar fç and bilir ö (2021), mutasyon ıslahı ile geliştirilmiş bazı aspir (carthamus tinctorius l.) hatlarının tarımsal performansları, turkısh journal of agricultural and natural sciences 8(2): 262-273. doi: org/10.30910/turkjans.685982 kalafat s, karakaya a, kaya m. and bayramin s (2009), a preliminary study on the reactions of safflower genotypes to rüşt disease, plant protection bulletin. 49(4): 183-187. koç h and güneş a (2021), determining the relationships between flower yield and some morphological traits in safflower genotypes, turkısh journal of nature and science 10(1): 90-95. kara m (2012), biyolojik ürünlerin fiziksel özellikleri, atatürk üniv. ziraat fakültesi yayınları no: 242. mohsenin nn (1970), physical properties of plant and animal materials. gordon and breach science publishers. nacar as, değirmenci v, hatipoğlu h, taş m, arslan h, çıkman a and şakak a (2016), effects of irrigation on yield and yield components at safflower plant in harran plain condition, tarla bitkileri merkez araştırma enst. dergisi 2(özel sayı-2): 149-154. toprak t and tunçtürk r (2018), effect of salt stress on developmental performance of diffrent aspir (carthamus tinctorius l.) cultivars, journal of natural & applied sciences of east 1(1): 44-50. weiss ea (2000), safflower. in: oilseed crops, blackwell sci. ltd., victoria, australia, pp 93-129. yılmaz s and tunçtürk m (2018), determination of yield and yield components of some safflower cultivars in soil with and without tillage under muş ecological conditions, journal of the instıtute of natural & applied sciences 23(1): 69-78. 65 proximate composition and thermal properties of hemp and flax fibres m. a. rahman1, m. m. rahman2*, k. nemoto3 and a. k. m. golam sarwar4 1department of bio-science and food production, shinshu university, 8304 minamiminowa, nagano 399-4598, japan. 2pulp and paper research division, bangladesh council of scientific and industrial research, dhaka 1205, bangladesh 3department of agricultural and life sciences, division of plant science and resources, shinshu university, 8304 minamiminowa, nagano 399-4598, japan 4laboratory of plant systematics, department of crop botany, bangladesh agricultural university, mymensingh 2202, bangladesh abstract along with the apparel or clothing industry, diversified uses of natural lignocellulosic fibre are getting popularity in many fields e.g., composites, automotive, marines, aerospace, electronics, civil construction, nanotechnology, biomedical, etc. the property and uses of textiles are determined by their constituent fibre properties. the proximate composition and thermogravimetric analysis (tga) data of a total of 9 local hemp and flax genotypes (3 and 6, respectively) were carried out to understand their suitability in different applications. a wide variation was observed in the ash content of hemp and flax fibres varied from 1.7 to 17.7%, crude protein 3.27 to 9.02%, crude fibre 26.51 to 55.32%, ether extract 2.6 to 20.9% and energy value 284.44 to 383.96 kcal 100–1 g. in tga analysis, all the fibres showed a similar trend. the flax genotypes contain lower ash and ether extract and higher dm, crude carbohydrate and crude fibre than hemp genotypes. therefore, flax could be used in the lightweight composite, textile, pulp and cellulose-based industries. the hemp fibre had higher ash which was reflected by a higher residue at 500oc in tga analysis. to understand the viability of these flax fibres, further investigations are needed. keywords: crude protein; crude fibre; ash; ether extract; thermogravimetric analysis *corresponding author e-mail: mmrbcsir3@gmail.com available online at www.banglajol.info bangladesh j. sci. ind. res. 58(1), 65-70, 2023 introduction natural fibres (nfs), hairlike structures, originated from animals (hairs, wools, silks, etc.), plants (bast, leaf and husk fibres, seed hairs, etc.), or geological processes. these can be used as a component of composites, nonwoven fabrics e.g., felt or paper or, altered into yarns, into woven cloth. the nfs have many advantages in different aspects e.g., environmental pollution, health, etc. over artificial fibres. these nfs are renewable, carbon-neutral, biodegradable and also produce waste that is either organic or can be used to generate electricity or make ecological housing material towards the achievement of un sustainable development goals (# 12 responsible production and consumption). the demand for commercial use of the nfs and fibre-based composites in various industrial sectors e.g., textile, pulp, automotive interior linings (roof, rear wall, side panel lining), furniture, construction, packaging, and shipping pallets, etc. for their better physicochemical and physicomechanical properties (girijappa et al. 2019). the quality and use of a natural fibre may vary due to inherent variabilities in its natural components such as fibrous nature, fibre morphology, cellulosic, and non-cellulosic content, and key properties such as fibrous structure, spinnability, strength, fineness, dyeability, and the ability to react with acid or alkali (shuvo, 2020). hemp (cannabis sativa l.; cannabaceae) and flax (linum usit at issimum l.; linaceae), two of the oldest cultivated fibre plants, fibres are singly or combined used for clothing and household textiles (skoglund et al. 2013). hemp has also various traditional uses in the indian subcontinent such as fibre and roasted seeds eaten as a food. in bangladesh, the hemp plant was cultivated for manufacturing three narcotic products called ganja, charas and bhang (o’malley, 1916); there are disagreements over the use of hemp fibres. according to o’malley, hemp was cultivated on 8,000 acres (approx. 3,250 ha) of land of sitakund on the banks of the sangu river and in the southeast of satkania on the banks of tankabati for producing hemp fibre (o’malley, 1908). milburn initially mentioned that hemp has been cultivated in bengal from time immemorial for intoxication (milburn, 1813); but is never used by natives for cordage or cloth, as in europe. however, he also pointed out later that when hemp is intended for cordage, the natives sow it very thin and afterwards transplant the young plants, placing them at a considerable distance from each other, often 2.75 or 3.0 m. the history of commercial hemp cultivation in bangladesh has been discussed (rahman et al. 2022). hemp fibres are used in rope, textiles, garden mulch, an assortment of building materials and animal beddings, to fabricate different composites, and processed to form yarn or bundles (girijappa et al. 2019). the history of linen production and use dates back to 12000 bc (vedic age) to 1500 ce (medieval period) in the indian subcontinent, including india, pakistan and bangladesh <https:// agropedia.i itk.ac.in/ content/history linenindian-subcontinent>. edible flaxseed dominated india’s production rather than fibre flax; because other fibre species, such as hemp, were already in wide use (judd, 1995). flax fibres are used in furniture materials, textiles bed sheets, linen, interior decoration accessories, composite reinforcement, etc. (girijappa et al. 2019; baley, 2021). the nutritional aspects of both hemp and flax seeds and different plant parts were reported in different publications (muir and westcott, 2003; audu et al. 2014; galasso et al. thermogravimetric analysis (tga) was performed by a thermal analyzer of sii tg/dta 6300. thermal analysis was carried out in the temperature range of 30–500°c with a programmed heating rate of 20°c min–1. the inertness of the heating chamber was maintained with continuous nitrogen gas flow at 100 ml min–1. the test was performed with a 5 to 8 mg ground sample in the platinum crucible. results and discussion proximate analysis distinct differences in all the proximate components were observed between fibre of hemp and flax genotypes except the dm content. the results revealed a close similarity in the dm content of hemp and flax fibres which varied from 96% to 97.1% (table i). high dm content in fibre cells indicates that these are rich in structural components – carbohydrates, protein, fats, minerals, etc. except water. the density of hemp and flax fibres was the same or very similar and low (1.4–1.5 g cm–3) which could be a great choice for light-weight composite structures (misnon, 2014). low-density fibre has enormous implications in technical textile industries, especially in aerospace and automotive applications for reducing fuel consumption and related fuel costs (shuvo et al. 2020). a careful selection of cultivars (/genotypes) would allow for the optimizing utility of this fibre feature (shuvo, 2020). ash content was analyzed in the range of 1.7% to 17.7% and a significant difference was observed between hemp (12.5–17.7%) and flax (1.7–3.8%) genotypes. the maximum ash was found in hemp genotype meherpur and the minimum in flax genotype chilmari. ash is the residue left after all the moisture and organic matter has been removed at high temperatures. the high ash content of these fibres is a measure of mineral richness (lai and roy, 2004). the maximum quantity of cp, ee and energy value was found in hemp genotypes and minimum in flax genotypes. fibres of two flax genotypes, viz. bd-10708 and bd-1903, contained an exceptionally higher amount of ether extract compared to others (table i). in living organisms, fat is the usually stored form of energy. they are the main structural element of phospholipids and sterols (hashim et al. 2014). the cf and crude carbohydrate (cc) contents showed the maximum value for flax genotype canada (55.32%) and nila (38.25%), respectively and a minimum for hemp genotype brammonbaria (26.51%) and meherpur (23.86%). the energy value of hemp genotypes was higher and ranged from 337.93 to 383.96 kcal 100–1 g (table i). this augmented energy value is due to their greater fat content compared with flax genotypes (ishag et al. 2019). among the different plant parts of hemp, the leaf possessed the maximum amount (23.78%) of cp (audu et al. 2014). on the other hand, fibre contains the highest amount of cf (28.29%) and ash (12%); ee (%) of the leaf was identical to that of fibre except in one genotype brammonbaria (table i) (audu et al. 2014). in flax plants, seeds contain the highest amount of cp (21%) and ee (43.17%), and maximum cf (avg. 51.23%) and cc (avg. 33.38%) in fibre (table i) (ishag et al. 2019). thermogravimetric analysis the tga curves were used to determine the thermal behaviour such as weight loss and residual char level of material at a certain temperature. the thermal behaviour of untreated hemp and flax fibres is shown in fig. 1. fibres of all the genot ypea are lignocellulosic and show almost similar thermal degradation patterns. thermal degradation profiles of the fibres are separated into three different stages. the first stage of degradation started at around 100°c and last up to 180°c. at this stage, about 10% mass loss occurs. mass loss of fibres at around 100°c due to elimination or rapid evaporation of water during the initial stages of heating (ouajai and shanks, 2005). in addition to moisture, some fraction of waxes, pectin, lignin and hemicellulose degraded in this stage (wielage et al. 1999). decomposing of both the hemp and flax fibres takes place slowly up to about 250°c. later the second decomposition started where the maximum mass loss occurred. maximum decomposition took place between 250 and 350°c due to the depolymerization of cellulose and hemicellulose (albano et al. 1999). it is obvious from the proximate analysis (table i) that there is a difference in the chemical composition of the genotypes that affects the thermal stability. the thermal stability of the flax genotypes chilmari and bd-10708 showed higher than the others. the third stage of decomposition begins at a temperature of about 350°c. at this stage, the fibre breaks down to form chars releasing water and carbon dioxide. with a further increase in temperature, the process of formation and digestion of chars takes place. the stable residual mass at 500°c temperature comes mostly from minerals and char residue (gashti et al. 2013). proximate analysis showed that hemp fibre had higher ash content on average than flax fibre (table i). the tga analysis also coincides with the proximate analysis showing a higher residual mass fraction at 500°c for hemp fibres. conclusion the lower ash and ether extract and higher dm, cc and cf of these flax fibres make them (also) suitable for being used in the lightweight composite, textile, pulp and cellulose-based industries. the hemp fibre had higher ash which was reflected by a higher residue at 500°c in tga analysis. high ash content in the hemp fibres will provide high thermal stability and could be used as reinforcement material for composite. further investigations are needed to understand the viability of these flax fibres for different purposes. references albano c, gonzalez j, ichazo m and kaiser d (1999), thermal stability of blends of polyolefins and sisal fiber, polym degrad stab. 66(2): 179-190. . alonso-esteban ji, pinela j, ćirić a, calhelha rc, soković m, ferreira ic, barros l, torija-isasa e and de cortes sánchez-mata m (2022), chemical composition and biological activities of whole and dehulled hemp (cannabis sativa l.) seeds, food chem. 374: 131754. doi: 10.1016/j.foodchem.2021.131754 audu bs, ofojekwu pc, ujah a and ajima mno (2014), phytochemical, proximate composition, amino acid profile and characterization of marijuana (cannabis sativa l.), j phytopharma. 3(1): 35-43. baley c, bourmaud a and davies p (2021), eighty years of composites reinforced by flax fibres: a historical review, composites part a: appl sci manufac 144: 106333. doi: 10.1016/j.compositesa.2021.106333 european parliament and council of the european union, (2011), regulation (eu) no 1169/2011 of the european parliament and of the council of 25 october 2011 on the provision of food information to consumers, amending regulations (ec) no 1924/ 2006 and (ec) no 1925/2006 of the european parliament and of the council, and repealing commission directive 87/250/eec, council directive 90/496/eec, commission directive 1999/10/ec, directive 2000/13/ec of the european parliament and of the council, commission directives 2002/67/ec and 2008/5/ec and commission regulation (ec) no 608/2004. official journal of the european union, l 304: 18-63. galasso i, russo r, mapelli s, ponzoni e, brambilla im, battelli g and reggiani r (2016), variability in seed traits in a collection of cannabis sativa l. genotypes, front plant sci. 7: 688. doi: 10.3389/ fpls. 2016.00688 gashti mp, elahi a and gashti mp (2013), uv radiation inducing succinic acid/silica–kaolinite network on cellulose fiber to improve the functionality, compos b eng. 48: 158-166 girijappa yt, rangappa sm, parameswaranpillai j and siengchin s (2019), natural fibers as sustainable and renewable resource for development of eco-friendly composites: a comprehensive review, front mater 6: 226. doi: 10.3389/fmats.2019.00226 hashim s, bakht t, marwat kb and jan a (2014), medicinal properties, phytochemistry and pharmacology of tribulus terrestris l. (zygophyllaceae), pak j bot. 46(1): 399-404. . ishag oao, khalid aa, abdi a, erwa iy, omer ab and nour ah (2019), proximate composition, physicochemical properties and antioxidant activity of flaxseed, annl res rev biol. 34(2): 1-10. judd a (1995), flaxseed in human nutrition. eds by s.c. cunnane, l.u. thompson. (aocs press, champaign, il) 1995, pp 1-10. kabir aa, moniruzzaman m, gulshan z, rahman am and sarwar akm golam (2018), biomass yield, chemical composition and in vitro gas production of different dhaincha (sesbania spp.) accessions from bangladesh, indian anim nutri. 35(4): 397-402. doi: 10.5958/2231-6744.2018.00060.9 lai pk and roy j (2004), antimicrobial and chemopreventive properties of herbs and spices, curr med chem. 11(11): 1451-1460. milburn w (1813), oriental commerce.vol. 2 (black, parry & co, london) 1813, pp 209-11. misnon mi, islam mm, epaarachchi ja and lau kt (2014), potentiality of utilising natural textile materials for engineering composites applications, mater des. 59: 359-368. doi: 10.1016/j.matdes.2014.03.022 muir ad and westcott nd (2003), flax: the genus linum. (crc press) 2003. mundaragi a, devarajan t, bhat s and jeyabalan s (2017), proximate analysis and mineral composition of potential minor fruits of western ghats of india. scientific papers. series a. agronomy, lx., pp 340-346. o’malley lss (1916), bengal district gazetteers: rajshahi. (bengal secretariat book depot, calcutta) 1996, pp 134-144 o'malley lss (1908), eastern bengal district gazetteers: chittagong (bengal secretariat book depot, calcutta) 1908. ouajai s and shanks ra (2005), composition, structure and thermal degradation of hemp cellulose after chemical treatments, polym degrad stab. 89(2): 327-335. rahman am, nemoto k, matsushima ki, uddin sb and sarwar akm golam (2022), a history of cannabis (ganja) as an economic crop in bangladesh from the late 18th century to 1989, trop agric develop 66(1): 21-32. doi: 10.9790/0837-2509041926 roy s, ali m, amin mn, jianguang s, bhattacharya sk, sen hs, sur d, lutfar lb, rahman ms, hassan ds (2010), jute basics, international jute study group, monipuri para, dhaka. shuvo ii (2020), fibre attributes and mapping the cultivar influence of different industrial cellulosic crops (cotton, hemp, flax, and canola) on textile properties, bioresour bioprocess 7(51): 1-28. doi: 10.1177/ 0040517519886636 shuvo ii, rahman m, vahora t, morrison j, ducharme s and choo-smith lpi (2020), producing light-weight bast fibers from canola biomass for technical textiles, tex res j. 90(11-12): 1311-1325. doi: 10.1186/ s40643-020-00339-1 skoglund g, nockert m and holst b (2013), viking and early middle ages northern scandinavian textiles proven to be made with hemp, sci rep. 3(1): 1-6. doi: 10.1038/srep02686 waris z, iqbal y, arshad hussain s, khan aa, ali a and khan mw (2018), proximate composition, phytochemical analysis and antioxidant capacity of aloe vera, cannabis sativa and mentha longifolia, pure appl biol. 7(3): 1122-1130. doi: 10.19045/ bspab.2018.700131 wielage b, lampke t, marx g, nestler k and starke d (1999), thermogravimetric and differential scanning calorimetric analysis of natural fibres and polypropylene, thermochimica acta. 337(1-2): 169-177. doi: https://doi.org/10.3329/bjsir.v58i1.64236 received: 01 february 2023 revised: 15 february 2023 accepted: 19 february 2023 2016; waris et al. 2018; ishag et al. 2019; alonso-esteban et al. 2022). although the physical properties of hemp and flax fibres are known to us (girijappa et al. 2019), hitherto, no information on the proximate composition of fibres of bangladeshi genotypes of these two important fibre-yielding crops is available. the constituent fibre properties influence application of textiles in many fields e.g., composites, automotive, marines, aerospace, electronics, civil construction, nanotechnology, biomedical, as well as the apparel or clothing industry (shuvo, 2020). we have, therefore, reported the proximate composition and thermogravimetric analysis data of 3 hemp and 6 flax genotypes here. materials and methods the proximate analysis and thermogravimetric analysis (of fibres) of six flax genotypes and three hemp genotypes were carried out to understand their suitability in different applications. hemp seeds were collected from different locations in bangladesh (detailed collection information will be available upon request) and the genotypes are named accordingly, viz. brammonbaria, chittagang and meherpur. the hemp plants were grown (in a confined area) at botanical garden, department of crop botany, bangladesh agricultural university. flax fibres were collected with the ribbon retting method (roy et al. 2010) and sun-dried properly. the flax fibres of 6 genotypes, harvested from another experiment in the same year, were collected from the laboratory of plant systematics of the same department. the proximate composition analysis viz. dry matter (dm), crude protein (cp), crude fibre (cf), ash and ether extract (crude fat; ee), were accomplished at the laboratory of department of animal science, bangladesh agricultural university, mymensingh following standard procedure (kabir et al. 2018). the crude carbohydrate was calculated following mundaragi et al. (2017). crude carbohydrate (%) = 100 – [moisture (%) + protein (%) + fibre (%) + fat (%) + ash (%)] the calorific value or the total energy value of fruits in kcal100–1 g was calculated with the help of the following equation (european parliament and council of the european union, 2011). energy value (kcal 100–1 g) = 4 × protein + 9 × fat + 4 × carbohydrate + 2 × fibre short communication proximate composition and thermal properties of hemp and flax fibres 58(1) 202366 furniture, construction, packaging, and shipping pallets, etc. for their better physicochemical and physicomechanical properties (girijappa et al. 2019). the quality and use of a natural fibre may vary due to inherent variabilities in its natural components such as fibrous nature, fibre morphology, cellulosic, and non-cellulosic content, and key properties such as fibrous structure, spinnability, strength, fineness, dyeability, and the ability to react with acid or alkali (shuvo, 2020). hemp (cannabis sativa l.; cannabaceae) and flax (linum usit at issimum l.; linaceae), two of the oldest cultivated fibre plants, fibres are singly or combined used for clothing and household textiles (skoglund et al. 2013). hemp has also various traditional uses in the indian subcontinent such as fibre and roasted seeds eaten as a food. in bangladesh, the hemp plant was cultivated for manufacturing three narcotic products called ganja, charas and bhang (o’malley, 1916); there are disagreements over the use of hemp fibres. according to o’malley, hemp was cultivated on 8,000 acres (approx. 3,250 ha) of land of sitakund on the banks of the sangu river and in the southeast of satkania on the banks of tankabati for producing hemp fibre (o’malley, 1908). milburn initially mentioned that hemp has been cultivated in bengal from time immemorial for intoxication (milburn, 1813); but is never used by natives for cordage or cloth, as in europe. however, he also pointed out later that when hemp is intended for cordage, the natives sow it very thin and afterwards transplant the young plants, placing them at a considerable distance from each other, often 2.75 or 3.0 m. the history of commercial hemp cultivation in bangladesh has been discussed (rahman et al. 2022). hemp fibres are used in rope, textiles, garden mulch, an assortment of building materials and animal beddings, to fabricate different composites, and processed to form yarn or bundles (girijappa et al. 2019). the history of linen production and use dates back to 12000 bc (vedic age) to 1500 ce (medieval period) in the indian subcontinent, including india, pakistan and bangladesh <https:// agropedia.i itk.ac.in/ content/history linenindian-subcontinent>. edible flaxseed dominated india’s production rather than fibre flax; because other fibre species, such as hemp, were already in wide use (judd, 1995). flax fibres are used in furniture materials, textiles bed sheets, linen, interior decoration accessories, composite reinforcement, etc. (girijappa et al. 2019; baley, 2021). the nutritional aspects of both hemp and flax seeds and different plant parts were reported in different publications (muir and westcott, 2003; audu et al. 2014; galasso et al. thermogravimetric analysis (tga) was performed by a thermal analyzer of sii tg/dta 6300. thermal analysis was carried out in the temperature range of 30–500°c with a programmed heating rate of 20°c min–1. the inertness of the heating chamber was maintained with continuous nitrogen gas flow at 100 ml min–1. the test was performed with a 5 to 8 mg ground sample in the platinum crucible. results and discussion proximate analysis distinct differences in all the proximate components were observed between fibre of hemp and flax genotypes except the dm content. the results revealed a close similarity in the dm content of hemp and flax fibres which varied from 96% to 97.1% (table i). high dm content in fibre cells indicates that these are rich in structural components – carbohydrates, protein, fats, minerals, etc. except water. the density of hemp and flax fibres was the same or very similar and low (1.4–1.5 g cm–3) which could be a great choice for light-weight composite structures (misnon, 2014). low-density fibre has enormous implications in technical textile industries, especially in aerospace and automotive applications for reducing fuel consumption and related fuel costs (shuvo et al. 2020). a careful selection of cultivars (/genotypes) would allow for the optimizing utility of this fibre feature (shuvo, 2020). ash content was analyzed in the range of 1.7% to 17.7% and a significant difference was observed between hemp (12.5–17.7%) and flax (1.7–3.8%) genotypes. the maximum ash was found in hemp genotype meherpur and the minimum in flax genotype chilmari. ash is the residue left after all the moisture and organic matter has been removed at high temperatures. the high ash content of these fibres is a measure of mineral richness (lai and roy, 2004). the maximum quantity of cp, ee and energy value was found in hemp genotypes and minimum in flax genotypes. fibres of two flax genotypes, viz. bd-10708 and bd-1903, contained an exceptionally higher amount of ether extract compared to others (table i). in living organisms, fat is the usually stored form of energy. they are the main structural element of phospholipids and sterols (hashim et al. 2014). the cf and crude carbohydrate (cc) contents showed the maximum value for flax genotype canada (55.32%) and nila (38.25%), respectively and a minimum for hemp genotype brammonbaria (26.51%) and meherpur (23.86%). the energy value of hemp genotypes was higher and ranged from 337.93 to 383.96 kcal 100–1 g (table i). this augmented energy value is due to their greater fat content compared with flax genotypes (ishag et al. 2019). among the different plant parts of hemp, the leaf possessed the maximum amount (23.78%) of cp (audu et al. 2014). on the other hand, fibre contains the highest amount of cf (28.29%) and ash (12%); ee (%) of the leaf was identical to that of fibre except in one genotype brammonbaria (table i) (audu et al. 2014). in flax plants, seeds contain the highest amount of cp (21%) and ee (43.17%), and maximum cf (avg. 51.23%) and cc (avg. 33.38%) in fibre (table i) (ishag et al. 2019). thermogravimetric analysis the tga curves were used to determine the thermal behaviour such as weight loss and residual char level of material at a certain temperature. the thermal behaviour of untreated hemp and flax fibres is shown in fig. 1. fibres of all the genot ypea are lignocellulosic and show almost similar thermal degradation patterns. thermal degradation profiles of the fibres are separated into three different stages. the first stage of degradation started at around 100°c and last up to 180°c. at this stage, about 10% mass loss occurs. mass loss of fibres at around 100°c due to elimination or rapid evaporation of water during the initial stages of heating (ouajai and shanks, 2005). in addition to moisture, some fraction of waxes, pectin, lignin and hemicellulose degraded in this stage (wielage et al. 1999). decomposing of both the hemp and flax fibres takes place slowly up to about 250°c. later the second decomposition started where the maximum mass loss occurred. maximum decomposition took place between 250 and 350°c due to the depolymerization of cellulose and hemicellulose (albano et al. 1999). it is obvious from the proximate analysis (table i) that there is a difference in the chemical composition of the genotypes that affects the thermal stability. the thermal stability of the flax genotypes chilmari and bd-10708 showed higher than the others. the third stage of decomposition begins at a temperature of about 350°c. at this stage, the fibre breaks down to form chars releasing water and carbon dioxide. with a further increase in temperature, the process of formation and digestion of chars takes place. the stable residual mass at 500°c temperature comes mostly from minerals and char residue (gashti et al. 2013). proximate analysis showed that hemp fibre had higher ash content on average than flax fibre (table i). the tga analysis also coincides with the proximate analysis showing a higher residual mass fraction at 500°c for hemp fibres. conclusion the lower ash and ether extract and higher dm, cc and cf of these flax fibres make them (also) suitable for being used in the lightweight composite, textile, pulp and cellulose-based industries. the hemp fibre had higher ash which was reflected by a higher residue at 500°c in tga analysis. high ash content in the hemp fibres will provide high thermal stability and could be used as reinforcement material for composite. further investigations are needed to understand the viability of these flax fibres for different purposes. references albano c, gonzalez j, ichazo m and kaiser d (1999), thermal stability of blends of polyolefins and sisal fiber, polym degrad stab. 66(2): 179-190. . alonso-esteban ji, pinela j, ćirić a, calhelha rc, soković m, ferreira ic, barros l, torija-isasa e and de cortes sánchez-mata m (2022), chemical composition and biological activities of whole and dehulled hemp (cannabis sativa l.) seeds, food chem. 374: 131754. doi: 10.1016/j.foodchem.2021.131754 audu bs, ofojekwu pc, ujah a and ajima mno (2014), phytochemical, proximate composition, amino acid profile and characterization of marijuana (cannabis sativa l.), j phytopharma. 3(1): 35-43. baley c, bourmaud a and davies p (2021), eighty years of composites reinforced by flax fibres: a historical review, composites part a: appl sci manufac 144: 106333. doi: 10.1016/j.compositesa.2021.106333 european parliament and council of the european union, (2011), regulation (eu) no 1169/2011 of the european parliament and of the council of 25 october 2011 on the provision of food information to consumers, amending regulations (ec) no 1924/ 2006 and (ec) no 1925/2006 of the european parliament and of the council, and repealing commission directive 87/250/eec, council directive 90/496/eec, commission directive 1999/10/ec, directive 2000/13/ec of the european parliament and of the council, commission directives 2002/67/ec and 2008/5/ec and commission regulation (ec) no 608/2004. official journal of the european union, l 304: 18-63. galasso i, russo r, mapelli s, ponzoni e, brambilla im, battelli g and reggiani r (2016), variability in seed traits in a collection of cannabis sativa l. genotypes, front plant sci. 7: 688. doi: 10.3389/ fpls. 2016.00688 gashti mp, elahi a and gashti mp (2013), uv radiation inducing succinic acid/silica–kaolinite network on cellulose fiber to improve the functionality, compos b eng. 48: 158-166 girijappa yt, rangappa sm, parameswaranpillai j and siengchin s (2019), natural fibers as sustainable and renewable resource for development of eco-friendly composites: a comprehensive review, front mater 6: 226. doi: 10.3389/fmats.2019.00226 hashim s, bakht t, marwat kb and jan a (2014), medicinal properties, phytochemistry and pharmacology of tribulus terrestris l. (zygophyllaceae), pak j bot. 46(1): 399-404. . ishag oao, khalid aa, abdi a, erwa iy, omer ab and nour ah (2019), proximate composition, physicochemical properties and antioxidant activity of flaxseed, annl res rev biol. 34(2): 1-10. judd a (1995), flaxseed in human nutrition. eds by s.c. cunnane, l.u. thompson. (aocs press, champaign, il) 1995, pp 1-10. kabir aa, moniruzzaman m, gulshan z, rahman am and sarwar akm golam (2018), biomass yield, chemical composition and in vitro gas production of different dhaincha (sesbania spp.) accessions from bangladesh, indian anim nutri. 35(4): 397-402. doi: 10.5958/2231-6744.2018.00060.9 lai pk and roy j (2004), antimicrobial and chemopreventive properties of herbs and spices, curr med chem. 11(11): 1451-1460. milburn w (1813), oriental commerce.vol. 2 (black, parry & co, london) 1813, pp 209-11. misnon mi, islam mm, epaarachchi ja and lau kt (2014), potentiality of utilising natural textile materials for engineering composites applications, mater des. 59: 359-368. doi: 10.1016/j.matdes.2014.03.022 muir ad and westcott nd (2003), flax: the genus linum. (crc press) 2003. mundaragi a, devarajan t, bhat s and jeyabalan s (2017), proximate analysis and mineral composition of potential minor fruits of western ghats of india. scientific papers. series a. agronomy, lx., pp 340-346. o’malley lss (1916), bengal district gazetteers: rajshahi. (bengal secretariat book depot, calcutta) 1996, pp 134-144 o'malley lss (1908), eastern bengal district gazetteers: chittagong (bengal secretariat book depot, calcutta) 1908. ouajai s and shanks ra (2005), composition, structure and thermal degradation of hemp cellulose after chemical treatments, polym degrad stab. 89(2): 327-335. rahman am, nemoto k, matsushima ki, uddin sb and sarwar akm golam (2022), a history of cannabis (ganja) as an economic crop in bangladesh from the late 18th century to 1989, trop agric develop 66(1): 21-32. doi: 10.9790/0837-2509041926 roy s, ali m, amin mn, jianguang s, bhattacharya sk, sen hs, sur d, lutfar lb, rahman ms, hassan ds (2010), jute basics, international jute study group, monipuri para, dhaka. shuvo ii (2020), fibre attributes and mapping the cultivar influence of different industrial cellulosic crops (cotton, hemp, flax, and canola) on textile properties, bioresour bioprocess 7(51): 1-28. doi: 10.1177/ 0040517519886636 shuvo ii, rahman m, vahora t, morrison j, ducharme s and choo-smith lpi (2020), producing light-weight bast fibers from canola biomass for technical textiles, tex res j. 90(11-12): 1311-1325. doi: 10.1186/ s40643-020-00339-1 skoglund g, nockert m and holst b (2013), viking and early middle ages northern scandinavian textiles proven to be made with hemp, sci rep. 3(1): 1-6. doi: 10.1038/srep02686 waris z, iqbal y, arshad hussain s, khan aa, ali a and khan mw (2018), proximate composition, phytochemical analysis and antioxidant capacity of aloe vera, cannabis sativa and mentha longifolia, pure appl biol. 7(3): 1122-1130. doi: 10.19045/ bspab.2018.700131 wielage b, lampke t, marx g, nestler k and starke d (1999), thermogravimetric and differential scanning calorimetric analysis of natural fibres and polypropylene, thermochimica acta. 337(1-2): 169-177. 2016; waris et al. 2018; ishag et al. 2019; alonso-esteban et al. 2022). although the physical properties of hemp and flax fibres are known to us (girijappa et al. 2019), hitherto, no information on the proximate composition of fibres of bangladeshi genotypes of these two important fibre-yielding crops is available. the constituent fibre properties influence application of textiles in many fields e.g., composites, automotive, marines, aerospace, electronics, civil construction, nanotechnology, biomedical, as well as the apparel or clothing industry (shuvo, 2020). we have, therefore, reported the proximate composition and thermogravimetric analysis data of 3 hemp and 6 flax genotypes here. materials and methods the proximate analysis and thermogravimetric analysis (of fibres) of six flax genotypes and three hemp genotypes were carried out to understand their suitability in different applications. hemp seeds were collected from different locations in bangladesh (detailed collection information will be available upon request) and the genotypes are named accordingly, viz. brammonbaria, chittagang and meherpur. the hemp plants were grown (in a confined area) at botanical garden, department of crop botany, bangladesh agricultural university. flax fibres were collected with the ribbon retting method (roy et al. 2010) and sun-dried properly. the flax fibres of 6 genotypes, harvested from another experiment in the same year, were collected from the laboratory of plant systematics of the same department. the proximate composition analysis viz. dry matter (dm), crude protein (cp), crude fibre (cf), ash and ether extract (crude fat; ee), were accomplished at the laboratory of department of animal science, bangladesh agricultural university, mymensingh following standard procedure (kabir et al. 2018). the crude carbohydrate was calculated following mundaragi et al. (2017). crude carbohydrate (%) = 100 – [moisture (%) + protein (%) + fibre (%) + fat (%) + ash (%)] the calorific value or the total energy value of fruits in kcal100–1 g was calculated with the help of the following equation (european parliament and council of the european union, 2011). energy value (kcal 100–1 g) = 4 × protein + 9 × fat + 4 × carbohydrate + 2 × fibre rahman, rahman, nemoto and sarwar 67 furniture, construction, packaging, and shipping pallets, etc. for their better physicochemical and physicomechanical properties (girijappa et al. 2019). the quality and use of a natural fibre may vary due to inherent variabilities in its natural components such as fibrous nature, fibre morphology, cellulosic, and non-cellulosic content, and key properties such as fibrous structure, spinnability, strength, fineness, dyeability, and the ability to react with acid or alkali (shuvo, 2020). hemp (cannabis sativa l.; cannabaceae) and flax (linum usit at issimum l.; linaceae), two of the oldest cultivated fibre plants, fibres are singly or combined used for clothing and household textiles (skoglund et al. 2013). hemp has also various traditional uses in the indian subcontinent such as fibre and roasted seeds eaten as a food. in bangladesh, the hemp plant was cultivated for manufacturing three narcotic products called ganja, charas and bhang (o’malley, 1916); there are disagreements over the use of hemp fibres. according to o’malley, hemp was cultivated on 8,000 acres (approx. 3,250 ha) of land of sitakund on the banks of the sangu river and in the southeast of satkania on the banks of tankabati for producing hemp fibre (o’malley, 1908). milburn initially mentioned that hemp has been cultivated in bengal from time immemorial for intoxication (milburn, 1813); but is never used by natives for cordage or cloth, as in europe. however, he also pointed out later that when hemp is intended for cordage, the natives sow it very thin and afterwards transplant the young plants, placing them at a considerable distance from each other, often 2.75 or 3.0 m. the history of commercial hemp cultivation in bangladesh has been discussed (rahman et al. 2022). hemp fibres are used in rope, textiles, garden mulch, an assortment of building materials and animal beddings, to fabricate different composites, and processed to form yarn or bundles (girijappa et al. 2019). the history of linen production and use dates back to 12000 bc (vedic age) to 1500 ce (medieval period) in the indian subcontinent, including india, pakistan and bangladesh <https:// agropedia.i itk.ac.in/ content/history linenindian-subcontinent>. edible flaxseed dominated india’s production rather than fibre flax; because other fibre species, such as hemp, were already in wide use (judd, 1995). flax fibres are used in furniture materials, textiles bed sheets, linen, interior decoration accessories, composite reinforcement, etc. (girijappa et al. 2019; baley, 2021). the nutritional aspects of both hemp and flax seeds and different plant parts were reported in different publications (muir and westcott, 2003; audu et al. 2014; galasso et al. thermogravimetric analysis (tga) was performed by a thermal analyzer of sii tg/dta 6300. thermal analysis was carried out in the temperature range of 30–500°c with a programmed heating rate of 20°c min–1. the inertness of the heating chamber was maintained with continuous nitrogen gas flow at 100 ml min–1. the test was performed with a 5 to 8 mg ground sample in the platinum crucible. results and discussion proximate analysis distinct differences in all the proximate components were observed between fibre of hemp and flax genotypes except the dm content. the results revealed a close similarity in the dm content of hemp and flax fibres which varied from 96% to 97.1% (table i). high dm content in fibre cells indicates that these are rich in structural components – carbohydrates, protein, fats, minerals, etc. except water. the density of hemp and flax fibres was the same or very similar and low (1.4–1.5 g cm–3) which could be a great choice for light-weight composite structures (misnon, 2014). low-density fibre has enormous implications in technical textile industries, especially in aerospace and automotive applications for reducing fuel consumption and related fuel costs (shuvo et al. 2020). a careful selection of cultivars (/genotypes) would allow for the optimizing utility of this fibre feature (shuvo, 2020). ash content was analyzed in the range of 1.7% to 17.7% and a significant difference was observed between hemp (12.5–17.7%) and flax (1.7–3.8%) genotypes. the maximum ash was found in hemp genotype meherpur and the minimum in flax genotype chilmari. ash is the residue left after all the moisture and organic matter has been removed at high temperatures. the high ash content of these fibres is a measure of mineral richness (lai and roy, 2004). the maximum quantity of cp, ee and energy value was found in hemp genotypes and minimum in flax genotypes. fibres of two flax genotypes, viz. bd-10708 and bd-1903, contained an exceptionally higher amount of ether extract compared to others (table i). in living organisms, fat is the usually stored form of energy. they are the main structural element of phospholipids and sterols (hashim et al. 2014). the cf and crude carbohydrate (cc) contents showed the maximum value for flax genotype canada (55.32%) and nila (38.25%), respectively and a minimum for hemp genotype brammonbaria (26.51%) and meherpur (23.86%). the energy value of hemp genotypes was higher and ranged from 337.93 to 383.96 kcal 100–1 g (table i). this augmented energy value is due to their greater fat content compared with flax genotypes (ishag et al. 2019). among the different plant parts of hemp, the leaf possessed the maximum amount (23.78%) of cp (audu et al. 2014). on the other hand, fibre contains the highest amount of cf (28.29%) and ash (12%); ee (%) of the leaf was identical to that of fibre except in one genotype brammonbaria (table i) (audu et al. 2014). in flax plants, seeds contain the highest amount of cp (21%) and ee (43.17%), and maximum cf (avg. 51.23%) and cc (avg. 33.38%) in fibre (table i) (ishag et al. 2019). thermogravimetric analysis the tga curves were used to determine the thermal behaviour such as weight loss and residual char level of material at a certain temperature. the thermal behaviour of untreated hemp and flax fibres is shown in fig. 1. fibres of all the genot ypea are lignocellulosic and show almost similar thermal degradation patterns. thermal degradation profiles of the fibres are separated into three different stages. the first stage of degradation started at around 100°c and last up to 180°c. at this stage, about 10% mass loss occurs. mass loss of fibres at around 100°c due to elimination or rapid evaporation of water during the initial stages of heating (ouajai and shanks, 2005). in addition to moisture, some fraction of waxes, pectin, lignin and hemicellulose degraded in this stage (wielage et al. 1999). decomposing of both the hemp and flax fibres takes place slowly up to about 250°c. later the second decomposition started where the maximum mass loss occurred. maximum decomposition took place between 250 and 350°c due to the depolymerization of cellulose and hemicellulose (albano et al. 1999). it is obvious from the proximate analysis (table i) that there is a difference in the chemical composition of the genotypes that affects the thermal stability. the thermal stability of the flax genotypes chilmari and bd-10708 showed higher than the others. the third stage of decomposition begins at a temperature of about 350°c. at this stage, the fibre breaks down to form chars releasing water and carbon dioxide. with a further increase in temperature, the process of formation and digestion of chars takes place. the stable residual mass at 500°c temperature comes mostly from minerals and char residue (gashti et al. 2013). proximate analysis showed that hemp fibre had higher ash content on average than flax fibre (table i). the tga analysis also coincides with the proximate analysis showing a higher residual mass fraction at 500°c for hemp fibres. conclusion the lower ash and ether extract and higher dm, cc and cf of these flax fibres make them (also) suitable for being used in the lightweight composite, textile, pulp and cellulose-based industries. the hemp fibre had higher ash which was reflected by a higher residue at 500°c in tga analysis. high ash content in the hemp fibres will provide high thermal stability and could be used as reinforcement material for composite. further investigations are needed to understand the viability of these flax fibres for different purposes. references albano c, gonzalez j, ichazo m and kaiser d (1999), thermal stability of blends of polyolefins and sisal fiber, polym degrad stab. 66(2): 179-190. . alonso-esteban ji, pinela j, ćirić a, calhelha rc, soković m, ferreira ic, barros l, torija-isasa e and de cortes sánchez-mata m (2022), chemical composition and biological activities of whole and dehulled hemp (cannabis sativa l.) seeds, food chem. 374: 131754. doi: 10.1016/j.foodchem.2021.131754 audu bs, ofojekwu pc, ujah a and ajima mno (2014), phytochemical, proximate composition, amino acid profile and characterization of marijuana (cannabis sativa l.), j phytopharma. 3(1): 35-43. baley c, bourmaud a and davies p (2021), eighty years of composites reinforced by flax fibres: a historical review, composites part a: appl sci manufac 144: 106333. doi: 10.1016/j.compositesa.2021.106333 european parliament and council of the european union, (2011), regulation (eu) no 1169/2011 of the european parliament and of the council of 25 october 2011 on the provision of food information to consumers, amending regulations (ec) no 1924/ 2006 and (ec) no 1925/2006 of the european parliament and of the council, and repealing commission directive 87/250/eec, council directive 90/496/eec, commission directive 1999/10/ec, directive 2000/13/ec of the european parliament and of the council, commission directives 2002/67/ec and 2008/5/ec and commission regulation (ec) no 608/2004. official journal of the european union, l 304: 18-63. galasso i, russo r, mapelli s, ponzoni e, brambilla im, battelli g and reggiani r (2016), variability in seed traits in a collection of cannabis sativa l. genotypes, front plant sci. 7: 688. doi: 10.3389/ fpls. 2016.00688 gashti mp, elahi a and gashti mp (2013), uv radiation inducing succinic acid/silica–kaolinite network on cellulose fiber to improve the functionality, compos b eng. 48: 158-166 girijappa yt, rangappa sm, parameswaranpillai j and siengchin s (2019), natural fibers as sustainable and renewable resource for development of eco-friendly composites: a comprehensive review, front mater 6: 226. doi: 10.3389/fmats.2019.00226 hashim s, bakht t, marwat kb and jan a (2014), medicinal properties, phytochemistry and pharmacology of tribulus terrestris l. (zygophyllaceae), pak j bot. 46(1): 399-404. . ishag oao, khalid aa, abdi a, erwa iy, omer ab and nour ah (2019), proximate composition, physicochemical properties and antioxidant activity of flaxseed, annl res rev biol. 34(2): 1-10. judd a (1995), flaxseed in human nutrition. eds by s.c. cunnane, l.u. thompson. (aocs press, champaign, il) 1995, pp 1-10. kabir aa, moniruzzaman m, gulshan z, rahman am and sarwar akm golam (2018), biomass yield, chemical composition and in vitro gas production of different dhaincha (sesbania spp.) accessions from bangladesh, indian anim nutri. 35(4): 397-402. doi: 10.5958/2231-6744.2018.00060.9 lai pk and roy j (2004), antimicrobial and chemopreventive properties of herbs and spices, curr med chem. 11(11): 1451-1460. milburn w (1813), oriental commerce.vol. 2 (black, parry & co, london) 1813, pp 209-11. misnon mi, islam mm, epaarachchi ja and lau kt (2014), potentiality of utilising natural textile materials for engineering composites applications, mater des. 59: 359-368. doi: 10.1016/j.matdes.2014.03.022 muir ad and westcott nd (2003), flax: the genus linum. (crc press) 2003. mundaragi a, devarajan t, bhat s and jeyabalan s (2017), proximate analysis and mineral composition of potential minor fruits of western ghats of india. scientific papers. series a. agronomy, lx., pp 340-346. o’malley lss (1916), bengal district gazetteers: rajshahi. (bengal secretariat book depot, calcutta) 1996, pp 134-144 o'malley lss (1908), eastern bengal district gazetteers: chittagong (bengal secretariat book depot, calcutta) 1908. ouajai s and shanks ra (2005), composition, structure and thermal degradation of hemp cellulose after chemical treatments, polym degrad stab. 89(2): 327-335. rahman am, nemoto k, matsushima ki, uddin sb and sarwar akm golam (2022), a history of cannabis (ganja) as an economic crop in bangladesh from the late 18th century to 1989, trop agric develop 66(1): 21-32. doi: 10.9790/0837-2509041926 roy s, ali m, amin mn, jianguang s, bhattacharya sk, sen hs, sur d, lutfar lb, rahman ms, hassan ds (2010), jute basics, international jute study group, monipuri para, dhaka. shuvo ii (2020), fibre attributes and mapping the cultivar influence of different industrial cellulosic crops (cotton, hemp, flax, and canola) on textile properties, bioresour bioprocess 7(51): 1-28. doi: 10.1177/ 0040517519886636 shuvo ii, rahman m, vahora t, morrison j, ducharme s and choo-smith lpi (2020), producing light-weight bast fibers from canola biomass for technical textiles, tex res j. 90(11-12): 1311-1325. doi: 10.1186/ s40643-020-00339-1 skoglund g, nockert m and holst b (2013), viking and early middle ages northern scandinavian textiles proven to be made with hemp, sci rep. 3(1): 1-6. doi: 10.1038/srep02686 waris z, iqbal y, arshad hussain s, khan aa, ali a and khan mw (2018), proximate composition, phytochemical analysis and antioxidant capacity of aloe vera, cannabis sativa and mentha longifolia, pure appl biol. 7(3): 1122-1130. doi: 10.19045/ bspab.2018.700131 wielage b, lampke t, marx g, nestler k and starke d (1999), thermogravimetric and differential scanning calorimetric analysis of natural fibres and polypropylene, thermochimica acta. 337(1-2): 169-177. 2016; waris et al. 2018; ishag et al. 2019; alonso-esteban et al. 2022). although the physical properties of hemp and flax fibres are known to us (girijappa et al. 2019), hitherto, no information on the proximate composition of fibres of bangladeshi genotypes of these two important fibre-yielding crops is available. the constituent fibre properties influence application of textiles in many fields e.g., composites, automotive, marines, aerospace, electronics, civil construction, nanotechnology, biomedical, as well as the apparel or clothing industry (shuvo, 2020). we have, therefore, reported the proximate composition and thermogravimetric analysis data of 3 hemp and 6 flax genotypes here. materials and methods the proximate analysis and thermogravimetric analysis (of fibres) of six flax genotypes and three hemp genotypes were carried out to understand their suitability in different applications. hemp seeds were collected from different locations in bangladesh (detailed collection information will be available upon request) and the genotypes are named accordingly, viz. brammonbaria, chittagang and meherpur. the hemp plants were grown (in a confined area) at botanical garden, department of crop botany, bangladesh agricultural university. flax fibres were collected with the ribbon retting method (roy et al. 2010) and sun-dried properly. the flax fibres of 6 genotypes, harvested from another experiment in the same year, were collected from the laboratory of plant systematics of the same department. the proximate composition analysis viz. dry matter (dm), crude protein (cp), crude fibre (cf), ash and ether extract (crude fat; ee), were accomplished at the laboratory of department of animal science, bangladesh agricultural university, mymensingh following standard procedure (kabir et al. 2018). the crude carbohydrate was calculated following mundaragi et al. (2017). crude carbohydrate (%) = 100 – [moisture (%) + protein (%) + fibre (%) + fat (%) + ash (%)] the calorific value or the total energy value of fruits in kcal100–1 g was calculated with the help of the following equation (european parliament and council of the european union, 2011). energy value (kcal 100–1 g) = 4 × protein + 9 × fat + 4 × carbohydrate + 2 × fibre genotype dry matter (%) ash (%) crude protein (%) crude fibre (%) ether extract (%) crude carbohydrate (%) energy value (kcal 100–1 g) hemp meherpur 96.9 17.7 7.94 29.10 18.30 23.86 350.1 brammonbaria 97.1 14.8 8.65 26.51 12.35 34.79 337.93 chittagang 97.0 12.5 9.02 29.27 20.90 25.31 383.96 average 97±0.08 15±2.13 8.54±0.45 28.29±1.26 17.18±3.58 27.99±4.85 357.33±19.47 flax nila 96.0 2.3 3.64 49.21 2.60 38.25 289.38 chilmari 96.2 1.7 3.27 52.21 3.91 35.11 293.13 china 96.5 3.8 3.62 51.73 3.42 33.93 284.44 bd-10708 96.8 1.8 5.24 47.28 9.70 32.78 333.94 canada 96.7 1.8 3.98 55.32 4.50 31.1 291.46 bd-1903 96.3 2.0 3.27 51.60 10.30 29.13 325.5 average 96.4±0.31 2.23±0.79 3.84±0.74 51.23±2.75 5.74±3.36 33.38±3.18 302.98±21.09 table i. proximate analysis of fibres of different hemp and flax genotypes proximate composition and thermal properties of hemp and flax fibres 58(1) 202368 furniture, construction, packaging, and shipping pallets, etc. for their better physicochemical and physicomechanical properties (girijappa et al. 2019). the quality and use of a natural fibre may vary due to inherent variabilities in its natural components such as fibrous nature, fibre morphology, cellulosic, and non-cellulosic content, and key properties such as fibrous structure, spinnability, strength, fineness, dyeability, and the ability to react with acid or alkali (shuvo, 2020). hemp (cannabis sativa l.; cannabaceae) and flax (linum usit at issimum l.; linaceae), two of the oldest cultivated fibre plants, fibres are singly or combined used for clothing and household textiles (skoglund et al. 2013). hemp has also various traditional uses in the indian subcontinent such as fibre and roasted seeds eaten as a food. in bangladesh, the hemp plant was cultivated for manufacturing three narcotic products called ganja, charas and bhang (o’malley, 1916); there are disagreements over the use of hemp fibres. according to o’malley, hemp was cultivated on 8,000 acres (approx. 3,250 ha) of land of sitakund on the banks of the sangu river and in the southeast of satkania on the banks of tankabati for producing hemp fibre (o’malley, 1908). milburn initially mentioned that hemp has been cultivated in bengal from time immemorial for intoxication (milburn, 1813); but is never used by natives for cordage or cloth, as in europe. however, he also pointed out later that when hemp is intended for cordage, the natives sow it very thin and afterwards transplant the young plants, placing them at a considerable distance from each other, often 2.75 or 3.0 m. the history of commercial hemp cultivation in bangladesh has been discussed (rahman et al. 2022). hemp fibres are used in rope, textiles, garden mulch, an assortment of building materials and animal beddings, to fabricate different composites, and processed to form yarn or bundles (girijappa et al. 2019). the history of linen production and use dates back to 12000 bc (vedic age) to 1500 ce (medieval period) in the indian subcontinent, including india, pakistan and bangladesh <https:// agropedia.i itk.ac.in/ content/history linenindian-subcontinent>. edible flaxseed dominated india’s production rather than fibre flax; because other fibre species, such as hemp, were already in wide use (judd, 1995). flax fibres are used in furniture materials, textiles bed sheets, linen, interior decoration accessories, composite reinforcement, etc. (girijappa et al. 2019; baley, 2021). the nutritional aspects of both hemp and flax seeds and different plant parts were reported in different publications (muir and westcott, 2003; audu et al. 2014; galasso et al. thermogravimetric analysis (tga) was performed by a thermal analyzer of sii tg/dta 6300. thermal analysis was carried out in the temperature range of 30–500°c with a programmed heating rate of 20°c min–1. the inertness of the heating chamber was maintained with continuous nitrogen gas flow at 100 ml min–1. the test was performed with a 5 to 8 mg ground sample in the platinum crucible. results and discussion proximate analysis distinct differences in all the proximate components were observed between fibre of hemp and flax genotypes except the dm content. the results revealed a close similarity in the dm content of hemp and flax fibres which varied from 96% to 97.1% (table i). high dm content in fibre cells indicates that these are rich in structural components – carbohydrates, protein, fats, minerals, etc. except water. the density of hemp and flax fibres was the same or very similar and low (1.4–1.5 g cm–3) which could be a great choice for light-weight composite structures (misnon, 2014). low-density fibre has enormous implications in technical textile industries, especially in aerospace and automotive applications for reducing fuel consumption and related fuel costs (shuvo et al. 2020). a careful selection of cultivars (/genotypes) would allow for the optimizing utility of this fibre feature (shuvo, 2020). ash content was analyzed in the range of 1.7% to 17.7% and a significant difference was observed between hemp (12.5–17.7%) and flax (1.7–3.8%) genotypes. the maximum ash was found in hemp genotype meherpur and the minimum in flax genotype chilmari. ash is the residue left after all the moisture and organic matter has been removed at high temperatures. the high ash content of these fibres is a measure of mineral richness (lai and roy, 2004). the maximum quantity of cp, ee and energy value was found in hemp genotypes and minimum in flax genotypes. fibres of two flax genotypes, viz. bd-10708 and bd-1903, contained an exceptionally higher amount of ether extract compared to others (table i). in living organisms, fat is the usually stored form of energy. they are the main structural element of phospholipids and sterols (hashim et al. 2014). the cf and crude carbohydrate (cc) contents showed the maximum value for flax genotype canada (55.32%) and nila (38.25%), respectively and a minimum for hemp genotype brammonbaria (26.51%) and meherpur (23.86%). the energy value of hemp genotypes was higher and ranged from 337.93 to 383.96 kcal 100–1 g (table i). this augmented energy value is due to their greater fat content compared with flax genotypes (ishag et al. 2019). among the different plant parts of hemp, the leaf possessed the maximum amount (23.78%) of cp (audu et al. 2014). on the other hand, fibre contains the highest amount of cf (28.29%) and ash (12%); ee (%) of the leaf was identical to that of fibre except in one genotype brammonbaria (table i) (audu et al. 2014). in flax plants, seeds contain the highest amount of cp (21%) and ee (43.17%), and maximum cf (avg. 51.23%) and cc (avg. 33.38%) in fibre (table i) (ishag et al. 2019). thermogravimetric analysis the tga curves were used to determine the thermal behaviour such as weight loss and residual char level of material at a certain temperature. the thermal behaviour of untreated hemp and flax fibres is shown in fig. 1. fibres of all the genot ypea are lignocellulosic and show almost similar thermal degradation patterns. thermal degradation profiles of the fibres are separated into three different stages. the first stage of degradation started at around 100°c and last up to 180°c. at this stage, about 10% mass loss occurs. mass loss of fibres at around 100°c due to elimination or rapid evaporation of water during the initial stages of heating (ouajai and shanks, 2005). in addition to moisture, some fraction of waxes, pectin, lignin and hemicellulose degraded in this stage (wielage et al. 1999). decomposing of both the hemp and flax fibres takes place slowly up to about 250°c. later the second decomposition started where the maximum mass loss occurred. maximum decomposition took place between 250 and 350°c due to the depolymerization of cellulose and hemicellulose (albano et al. 1999). it is obvious from the proximate analysis (table i) that there is a difference in the chemical composition of the genotypes that affects the thermal stability. the thermal stability of the flax genotypes chilmari and bd-10708 showed higher than the others. the third stage of decomposition begins at a temperature of about 350°c. at this stage, the fibre breaks down to form chars releasing water and carbon dioxide. with a further increase in temperature, the process of formation and digestion of chars takes place. the stable residual mass at 500°c temperature comes mostly from minerals and char residue (gashti et al. 2013). proximate analysis showed that hemp fibre had higher ash content on average than flax fibre (table i). the tga analysis also coincides with the proximate analysis showing a higher residual mass fraction at 500°c for hemp fibres. conclusion the lower ash and ether extract and higher dm, cc and cf of these flax fibres make them (also) suitable for being used in the lightweight composite, textile, pulp and cellulose-based industries. the hemp fibre had higher ash which was reflected by a higher residue at 500°c in tga analysis. high ash content in the hemp fibres will provide high thermal stability and could be used as reinforcement material for composite. further investigations are needed to understand the viability of these flax fibres for different purposes. references albano c, gonzalez j, ichazo m and kaiser d (1999), thermal stability of blends of polyolefins and sisal fiber, polym degrad stab. 66(2): 179-190. . alonso-esteban ji, pinela j, ćirić a, calhelha rc, soković m, ferreira ic, barros l, torija-isasa e and de cortes sánchez-mata m (2022), chemical composition and biological activities of whole and dehulled hemp (cannabis sativa l.) seeds, food chem. 374: 131754. doi: 10.1016/j.foodchem.2021.131754 audu bs, ofojekwu pc, ujah a and ajima mno (2014), phytochemical, proximate composition, amino acid profile and characterization of marijuana (cannabis sativa l.), j phytopharma. 3(1): 35-43. baley c, bourmaud a and davies p (2021), eighty years of composites reinforced by flax fibres: a historical review, composites part a: appl sci manufac 144: 106333. doi: 10.1016/j.compositesa.2021.106333 european parliament and council of the european union, (2011), regulation (eu) no 1169/2011 of the european parliament and of the council of 25 october 2011 on the provision of food information to consumers, amending regulations (ec) no 1924/ 2006 and (ec) no 1925/2006 of the european parliament and of the council, and repealing commission directive 87/250/eec, council directive 90/496/eec, commission directive 1999/10/ec, directive 2000/13/ec of the european parliament and of the council, commission directives 2002/67/ec and 2008/5/ec and commission regulation (ec) no 608/2004. official journal of the european union, l 304: 18-63. galasso i, russo r, mapelli s, ponzoni e, brambilla im, battelli g and reggiani r (2016), variability in seed traits in a collection of cannabis sativa l. genotypes, front plant sci. 7: 688. doi: 10.3389/ fpls. 2016.00688 gashti mp, elahi a and gashti mp (2013), uv radiation inducing succinic acid/silica–kaolinite network on cellulose fiber to improve the functionality, compos b eng. 48: 158-166 girijappa yt, rangappa sm, parameswaranpillai j and siengchin s (2019), natural fibers as sustainable and renewable resource for development of eco-friendly composites: a comprehensive review, front mater 6: 226. doi: 10.3389/fmats.2019.00226 hashim s, bakht t, marwat kb and jan a (2014), medicinal properties, phytochemistry and pharmacology of tribulus terrestris l. (zygophyllaceae), pak j bot. 46(1): 399-404. . ishag oao, khalid aa, abdi a, erwa iy, omer ab and nour ah (2019), proximate composition, physicochemical properties and antioxidant activity of flaxseed, annl res rev biol. 34(2): 1-10. judd a (1995), flaxseed in human nutrition. eds by s.c. cunnane, l.u. thompson. (aocs press, champaign, il) 1995, pp 1-10. kabir aa, moniruzzaman m, gulshan z, rahman am and sarwar akm golam (2018), biomass yield, chemical composition and in vitro gas production of different dhaincha (sesbania spp.) accessions from bangladesh, indian anim nutri. 35(4): 397-402. doi: 10.5958/2231-6744.2018.00060.9 lai pk and roy j (2004), antimicrobial and chemopreventive properties of herbs and spices, curr med chem. 11(11): 1451-1460. milburn w (1813), oriental commerce.vol. 2 (black, parry & co, london) 1813, pp 209-11. misnon mi, islam mm, epaarachchi ja and lau kt (2014), potentiality of utilising natural textile materials for engineering composites applications, mater des. 59: 359-368. doi: 10.1016/j.matdes.2014.03.022 muir ad and westcott nd (2003), flax: the genus linum. (crc press) 2003. mundaragi a, devarajan t, bhat s and jeyabalan s (2017), proximate analysis and mineral composition of potential minor fruits of western ghats of india. scientific papers. series a. agronomy, lx., pp 340-346. o’malley lss (1916), bengal district gazetteers: rajshahi. (bengal secretariat book depot, calcutta) 1996, pp 134-144 o'malley lss (1908), eastern bengal district gazetteers: chittagong (bengal secretariat book depot, calcutta) 1908. ouajai s and shanks ra (2005), composition, structure and thermal degradation of hemp cellulose after chemical treatments, polym degrad stab. 89(2): 327-335. rahman am, nemoto k, matsushima ki, uddin sb and sarwar akm golam (2022), a history of cannabis (ganja) as an economic crop in bangladesh from the late 18th century to 1989, trop agric develop 66(1): 21-32. doi: 10.9790/0837-2509041926 roy s, ali m, amin mn, jianguang s, bhattacharya sk, sen hs, sur d, lutfar lb, rahman ms, hassan ds (2010), jute basics, international jute study group, monipuri para, dhaka. shuvo ii (2020), fibre attributes and mapping the cultivar influence of different industrial cellulosic crops (cotton, hemp, flax, and canola) on textile properties, bioresour bioprocess 7(51): 1-28. doi: 10.1177/ 0040517519886636 shuvo ii, rahman m, vahora t, morrison j, ducharme s and choo-smith lpi (2020), producing light-weight bast fibers from canola biomass for technical textiles, tex res j. 90(11-12): 1311-1325. doi: 10.1186/ s40643-020-00339-1 skoglund g, nockert m and holst b (2013), viking and early middle ages northern scandinavian textiles proven to be made with hemp, sci rep. 3(1): 1-6. doi: 10.1038/srep02686 waris z, iqbal y, arshad hussain s, khan aa, ali a and khan mw (2018), proximate composition, phytochemical analysis and antioxidant capacity of aloe vera, cannabis sativa and mentha longifolia, pure appl biol. 7(3): 1122-1130. doi: 10.19045/ bspab.2018.700131 wielage b, lampke t, marx g, nestler k and starke d (1999), thermogravimetric and differential scanning calorimetric analysis of natural fibres and polypropylene, thermochimica acta. 337(1-2): 169-177. 2016; waris et al. 2018; ishag et al. 2019; alonso-esteban et al. 2022). although the physical properties of hemp and flax fibres are known to us (girijappa et al. 2019), hitherto, no information on the proximate composition of fibres of bangladeshi genotypes of these two important fibre-yielding crops is available. the constituent fibre properties influence application of textiles in many fields e.g., composites, automotive, marines, aerospace, electronics, civil construction, nanotechnology, biomedical, as well as the apparel or clothing industry (shuvo, 2020). we have, therefore, reported the proximate composition and thermogravimetric analysis data of 3 hemp and 6 flax genotypes here. materials and methods the proximate analysis and thermogravimetric analysis (of fibres) of six flax genotypes and three hemp genotypes were carried out to understand their suitability in different applications. hemp seeds were collected from different locations in bangladesh (detailed collection information will be available upon request) and the genotypes are named accordingly, viz. brammonbaria, chittagang and meherpur. the hemp plants were grown (in a confined area) at botanical garden, department of crop botany, bangladesh agricultural university. flax fibres were collected with the ribbon retting method (roy et al. 2010) and sun-dried properly. the flax fibres of 6 genotypes, harvested from another experiment in the same year, were collected from the laboratory of plant systematics of the same department. the proximate composition analysis viz. dry matter (dm), crude protein (cp), crude fibre (cf), ash and ether extract (crude fat; ee), were accomplished at the laboratory of department of animal science, bangladesh agricultural university, mymensingh following standard procedure (kabir et al. 2018). the crude carbohydrate was calculated following mundaragi et al. (2017). crude carbohydrate (%) = 100 – [moisture (%) + protein (%) + fibre (%) + fat (%) + ash (%)] the calorific value or the total energy value of fruits in kcal100–1 g was calculated with the help of the following equation (european parliament and council of the european union, 2011). energy value (kcal 100–1 g) = 4 × protein + 9 × fat + 4 × carbohydrate + 2 × fibre fig. 1. thermogravimetric analysis curves of fibres of different hemp and flax genotypes rahman, rahman, nemoto and sarwar 69 furniture, construction, packaging, and shipping pallets, etc. for their better physicochemical and physicomechanical properties (girijappa et al. 2019). the quality and use of a natural fibre may vary due to inherent variabilities in its natural components such as fibrous nature, fibre morphology, cellulosic, and non-cellulosic content, and key properties such as fibrous structure, spinnability, strength, fineness, dyeability, and the ability to react with acid or alkali (shuvo, 2020). hemp (cannabis sativa l.; cannabaceae) and flax (linum usit at issimum l.; linaceae), two of the oldest cultivated fibre plants, fibres are singly or combined used for clothing and household textiles (skoglund et al. 2013). hemp has also various traditional uses in the indian subcontinent such as fibre and roasted seeds eaten as a food. in bangladesh, the hemp plant was cultivated for manufacturing three narcotic products called ganja, charas and bhang (o’malley, 1916); there are disagreements over the use of hemp fibres. according to o’malley, hemp was cultivated on 8,000 acres (approx. 3,250 ha) of land of sitakund on the banks of the sangu river and in the southeast of satkania on the banks of tankabati for producing hemp fibre (o’malley, 1908). milburn initially mentioned that hemp has been cultivated in bengal from time immemorial for intoxication (milburn, 1813); but is never used by natives for cordage or cloth, as in europe. however, he also pointed out later that when hemp is intended for cordage, the natives sow it very thin and afterwards transplant the young plants, placing them at a considerable distance from each other, often 2.75 or 3.0 m. the history of commercial hemp cultivation in bangladesh has been discussed (rahman et al. 2022). hemp fibres are used in rope, textiles, garden mulch, an assortment of building materials and animal beddings, to fabricate different composites, and processed to form yarn or bundles (girijappa et al. 2019). the history of linen production and use dates back to 12000 bc (vedic age) to 1500 ce (medieval period) in the indian subcontinent, including india, pakistan and bangladesh <https:// agropedia.i itk.ac.in/ content/history linenindian-subcontinent>. edible flaxseed dominated india’s production rather than fibre flax; because other fibre species, such as hemp, were already in wide use (judd, 1995). flax fibres are used in furniture materials, textiles bed sheets, linen, interior decoration accessories, composite reinforcement, etc. (girijappa et al. 2019; baley, 2021). the nutritional aspects of both hemp and flax seeds and different plant parts were reported in different publications (muir and westcott, 2003; audu et al. 2014; galasso et al. thermogravimetric analysis (tga) was performed by a thermal analyzer of sii tg/dta 6300. thermal analysis was carried out in the temperature range of 30–500°c with a programmed heating rate of 20°c min–1. the inertness of the heating chamber was maintained with continuous nitrogen gas flow at 100 ml min–1. the test was performed with a 5 to 8 mg ground sample in the platinum crucible. results and discussion proximate analysis distinct differences in all the proximate components were observed between fibre of hemp and flax genotypes except the dm content. the results revealed a close similarity in the dm content of hemp and flax fibres which varied from 96% to 97.1% (table i). high dm content in fibre cells indicates that these are rich in structural components – carbohydrates, protein, fats, minerals, etc. except water. the density of hemp and flax fibres was the same or very similar and low (1.4–1.5 g cm–3) which could be a great choice for light-weight composite structures (misnon, 2014). low-density fibre has enormous implications in technical textile industries, especially in aerospace and automotive applications for reducing fuel consumption and related fuel costs (shuvo et al. 2020). a careful selection of cultivars (/genotypes) would allow for the optimizing utility of this fibre feature (shuvo, 2020). ash content was analyzed in the range of 1.7% to 17.7% and a significant difference was observed between hemp (12.5–17.7%) and flax (1.7–3.8%) genotypes. the maximum ash was found in hemp genotype meherpur and the minimum in flax genotype chilmari. ash is the residue left after all the moisture and organic matter has been removed at high temperatures. the high ash content of these fibres is a measure of mineral richness (lai and roy, 2004). the maximum quantity of cp, ee and energy value was found in hemp genotypes and minimum in flax genotypes. fibres of two flax genotypes, viz. bd-10708 and bd-1903, contained an exceptionally higher amount of ether extract compared to others (table i). in living organisms, fat is the usually stored form of energy. they are the main structural element of phospholipids and sterols (hashim et al. 2014). the cf and crude carbohydrate (cc) contents showed the maximum value for flax genotype canada (55.32%) and nila (38.25%), respectively and a minimum for hemp genotype brammonbaria (26.51%) and meherpur (23.86%). the energy value of hemp genotypes was higher and ranged from 337.93 to 383.96 kcal 100–1 g (table i). this augmented energy value is due to their greater fat content compared with flax genotypes (ishag et al. 2019). among the different plant parts of hemp, the leaf possessed the maximum amount (23.78%) of cp (audu et al. 2014). on the other hand, fibre contains the highest amount of cf (28.29%) and ash (12%); ee (%) of the leaf was identical to that of fibre except in one genotype brammonbaria (table i) (audu et al. 2014). in flax plants, seeds contain the highest amount of cp (21%) and ee (43.17%), and maximum cf (avg. 51.23%) and cc (avg. 33.38%) in fibre (table i) (ishag et al. 2019). thermogravimetric analysis the tga curves were used to determine the thermal behaviour such as weight loss and residual char level of material at a certain temperature. the thermal behaviour of untreated hemp and flax fibres is shown in fig. 1. fibres of all the genot ypea are lignocellulosic and show almost similar thermal degradation patterns. thermal degradation profiles of the fibres are separated into three different stages. the first stage of degradation started at around 100°c and last up to 180°c. at this stage, about 10% mass loss occurs. mass loss of fibres at around 100°c due to elimination or rapid evaporation of water during the initial stages of heating (ouajai and shanks, 2005). in addition to moisture, some fraction of waxes, pectin, lignin and hemicellulose degraded in this stage (wielage et al. 1999). decomposing of both the hemp and flax fibres takes place slowly up to about 250°c. later the second decomposition started where the maximum mass loss occurred. maximum decomposition took place between 250 and 350°c due to the depolymerization of cellulose and hemicellulose (albano et al. 1999). it is obvious from the proximate analysis (table i) that there is a difference in the chemical composition of the genotypes that affects the thermal stability. the thermal stability of the flax genotypes chilmari and bd-10708 showed higher than the others. the third stage of decomposition begins at a temperature of about 350°c. at this stage, the fibre breaks down to form chars releasing water and carbon dioxide. with a further increase in temperature, the process of formation and digestion of chars takes place. the stable residual mass at 500°c temperature comes mostly from minerals and char residue (gashti et al. 2013). proximate analysis showed that hemp fibre had higher ash content on average than flax fibre (table i). the tga analysis also coincides with the proximate analysis showing a higher residual mass fraction at 500°c for hemp fibres. conclusion the lower ash and ether extract and higher dm, cc and cf of these flax fibres make them (also) suitable for being used in the lightweight composite, textile, pulp and cellulose-based industries. the hemp fibre had higher ash which was reflected by a higher residue at 500°c in tga analysis. high ash content in the hemp fibres will provide high thermal stability and could be used as reinforcement material for composite. further investigations are needed to understand the viability of these flax fibres for different purposes. references albano c, gonzalez j, ichazo m and kaiser d (1999), thermal stability of blends of polyolefins and sisal fiber, polym degrad stab. 66(2): 179-190. . alonso-esteban ji, pinela j, ćirić a, calhelha rc, soković m, ferreira ic, barros l, torija-isasa e and de cortes sánchez-mata m (2022), chemical composition and biological activities of whole and dehulled hemp (cannabis sativa l.) seeds, food chem. 374: 131754. doi: 10.1016/j.foodchem.2021.131754 audu bs, ofojekwu pc, ujah a and ajima mno (2014), phytochemical, proximate composition, amino acid profile and characterization of marijuana (cannabis sativa l.), j phytopharma. 3(1): 35-43. baley c, bourmaud a and davies p (2021), eighty years of composites reinforced by flax fibres: a historical review, composites part a: appl sci manufac 144: 106333. doi: 10.1016/j.compositesa.2021.106333 european parliament and council of the european union, (2011), regulation (eu) no 1169/2011 of the european parliament and of the council of 25 october 2011 on the provision of food information to consumers, amending regulations (ec) no 1924/ 2006 and (ec) no 1925/2006 of the european parliament and of the council, and repealing commission directive 87/250/eec, council directive 90/496/eec, commission directive 1999/10/ec, directive 2000/13/ec of the european parliament and of the council, commission directives 2002/67/ec and 2008/5/ec and commission regulation (ec) no 608/2004. official journal of the european union, l 304: 18-63. galasso i, russo r, mapelli s, ponzoni e, brambilla im, battelli g and reggiani r (2016), variability in seed traits in a collection of cannabis sativa l. genotypes, front plant sci. 7: 688. doi: 10.3389/ fpls. 2016.00688 gashti mp, elahi a and gashti mp (2013), uv radiation inducing succinic acid/silica–kaolinite network on cellulose fiber to improve the functionality, compos b eng. 48: 158-166 girijappa yt, rangappa sm, parameswaranpillai j and siengchin s (2019), natural fibers as sustainable and renewable resource for development of eco-friendly composites: a comprehensive review, front mater 6: 226. doi: 10.3389/fmats.2019.00226 hashim s, bakht t, marwat kb and jan a (2014), medicinal properties, phytochemistry and pharmacology of tribulus terrestris l. (zygophyllaceae), pak j bot. 46(1): 399-404. . ishag oao, khalid aa, abdi a, erwa iy, omer ab and nour ah (2019), proximate composition, physicochemical properties and antioxidant activity of flaxseed, annl res rev biol. 34(2): 1-10. judd a (1995), flaxseed in human nutrition. eds by s.c. cunnane, l.u. thompson. (aocs press, champaign, il) 1995, pp 1-10. kabir aa, moniruzzaman m, gulshan z, rahman am and sarwar akm golam (2018), biomass yield, chemical composition and in vitro gas production of different dhaincha (sesbania spp.) accessions from bangladesh, indian anim nutri. 35(4): 397-402. doi: 10.5958/2231-6744.2018.00060.9 lai pk and roy j (2004), antimicrobial and chemopreventive properties of herbs and spices, curr med chem. 11(11): 1451-1460. milburn w (1813), oriental commerce.vol. 2 (black, parry & co, london) 1813, pp 209-11. misnon mi, islam mm, epaarachchi ja and lau kt (2014), potentiality of utilising natural textile materials for engineering composites applications, mater des. 59: 359-368. doi: 10.1016/j.matdes.2014.03.022 muir ad and westcott nd (2003), flax: the genus linum. (crc press) 2003. mundaragi a, devarajan t, bhat s and jeyabalan s (2017), proximate analysis and mineral composition of potential minor fruits of western ghats of india. scientific papers. series a. agronomy, lx., pp 340-346. o’malley lss (1916), bengal district gazetteers: rajshahi. (bengal secretariat book depot, calcutta) 1996, pp 134-144 o'malley lss (1908), eastern bengal district gazetteers: chittagong (bengal secretariat book depot, calcutta) 1908. ouajai s and shanks ra (2005), composition, structure and thermal degradation of hemp cellulose after chemical treatments, polym degrad stab. 89(2): 327-335. rahman am, nemoto k, matsushima ki, uddin sb and sarwar akm golam (2022), a history of cannabis (ganja) as an economic crop in bangladesh from the late 18th century to 1989, trop agric develop 66(1): 21-32. doi: 10.9790/0837-2509041926 roy s, ali m, amin mn, jianguang s, bhattacharya sk, sen hs, sur d, lutfar lb, rahman ms, hassan ds (2010), jute basics, international jute study group, monipuri para, dhaka. shuvo ii (2020), fibre attributes and mapping the cultivar influence of different industrial cellulosic crops (cotton, hemp, flax, and canola) on textile properties, bioresour bioprocess 7(51): 1-28. doi: 10.1177/ 0040517519886636 shuvo ii, rahman m, vahora t, morrison j, ducharme s and choo-smith lpi (2020), producing light-weight bast fibers from canola biomass for technical textiles, tex res j. 90(11-12): 1311-1325. doi: 10.1186/ s40643-020-00339-1 skoglund g, nockert m and holst b (2013), viking and early middle ages northern scandinavian textiles proven to be made with hemp, sci rep. 3(1): 1-6. doi: 10.1038/srep02686 waris z, iqbal y, arshad hussain s, khan aa, ali a and khan mw (2018), proximate composition, phytochemical analysis and antioxidant capacity of aloe vera, cannabis sativa and mentha longifolia, pure appl biol. 7(3): 1122-1130. doi: 10.19045/ bspab.2018.700131 wielage b, lampke t, marx g, nestler k and starke d (1999), thermogravimetric and differential scanning calorimetric analysis of natural fibres and polypropylene, thermochimica acta. 337(1-2): 169-177. 2016; waris et al. 2018; ishag et al. 2019; alonso-esteban et al. 2022). although the physical properties of hemp and flax fibres are known to us (girijappa et al. 2019), hitherto, no information on the proximate composition of fibres of bangladeshi genotypes of these two important fibre-yielding crops is available. the constituent fibre properties influence application of textiles in many fields e.g., composites, automotive, marines, aerospace, electronics, civil construction, nanotechnology, biomedical, as well as the apparel or clothing industry (shuvo, 2020). we have, therefore, reported the proximate composition and thermogravimetric analysis data of 3 hemp and 6 flax genotypes here. materials and methods the proximate analysis and thermogravimetric analysis (of fibres) of six flax genotypes and three hemp genotypes were carried out to understand their suitability in different applications. hemp seeds were collected from different locations in bangladesh (detailed collection information will be available upon request) and the genotypes are named accordingly, viz. brammonbaria, chittagang and meherpur. the hemp plants were grown (in a confined area) at botanical garden, department of crop botany, bangladesh agricultural university. flax fibres were collected with the ribbon retting method (roy et al. 2010) and sun-dried properly. the flax fibres of 6 genotypes, harvested from another experiment in the same year, were collected from the laboratory of plant systematics of the same department. the proximate composition analysis viz. dry matter (dm), crude protein (cp), crude fibre (cf), ash and ether extract (crude fat; ee), were accomplished at the laboratory of department of animal science, bangladesh agricultural university, mymensingh following standard procedure (kabir et al. 2018). the crude carbohydrate was calculated following mundaragi et al. (2017). crude carbohydrate (%) = 100 – [moisture (%) + protein (%) + fibre (%) + fat (%) + ash (%)] the calorific value or the total energy value of fruits in kcal100–1 g was calculated with the help of the following equation (european parliament and council of the european union, 2011). energy value (kcal 100–1 g) = 4 × protein + 9 × fat + 4 × carbohydrate + 2 × fibre proximate composition and thermal properties of hemp and flax fibres 58(1) 202370 furniture, construction, packaging, and shipping pallets, etc. for their better physicochemical and physicomechanical properties (girijappa et al. 2019). the quality and use of a natural fibre may vary due to inherent variabilities in its natural components such as fibrous nature, fibre morphology, cellulosic, and non-cellulosic content, and key properties such as fibrous structure, spinnability, strength, fineness, dyeability, and the ability to react with acid or alkali (shuvo, 2020). hemp (cannabis sativa l.; cannabaceae) and flax (linum usit at issimum l.; linaceae), two of the oldest cultivated fibre plants, fibres are singly or combined used for clothing and household textiles (skoglund et al. 2013). hemp has also various traditional uses in the indian subcontinent such as fibre and roasted seeds eaten as a food. in bangladesh, the hemp plant was cultivated for manufacturing three narcotic products called ganja, charas and bhang (o’malley, 1916); there are disagreements over the use of hemp fibres. according to o’malley, hemp was cultivated on 8,000 acres (approx. 3,250 ha) of land of sitakund on the banks of the sangu river and in the southeast of satkania on the banks of tankabati for producing hemp fibre (o’malley, 1908). milburn initially mentioned that hemp has been cultivated in bengal from time immemorial for intoxication (milburn, 1813); but is never used by natives for cordage or cloth, as in europe. however, he also pointed out later that when hemp is intended for cordage, the natives sow it very thin and afterwards transplant the young plants, placing them at a considerable distance from each other, often 2.75 or 3.0 m. the history of commercial hemp cultivation in bangladesh has been discussed (rahman et al. 2022). hemp fibres are used in rope, textiles, garden mulch, an assortment of building materials and animal beddings, to fabricate different composites, and processed to form yarn or bundles (girijappa et al. 2019). the history of linen production and use dates back to 12000 bc (vedic age) to 1500 ce (medieval period) in the indian subcontinent, including india, pakistan and bangladesh <https:// agropedia.i itk.ac.in/ content/history linenindian-subcontinent>. edible flaxseed dominated india’s production rather than fibre flax; because other fibre species, such as hemp, were already in wide use (judd, 1995). flax fibres are used in furniture materials, textiles bed sheets, linen, interior decoration accessories, composite reinforcement, etc. (girijappa et al. 2019; baley, 2021). the nutritional aspects of both hemp and flax seeds and different plant parts were reported in different publications (muir and westcott, 2003; audu et al. 2014; galasso et al. thermogravimetric analysis (tga) was performed by a thermal analyzer of sii tg/dta 6300. thermal analysis was carried out in the temperature range of 30–500°c with a programmed heating rate of 20°c min–1. the inertness of the heating chamber was maintained with continuous nitrogen gas flow at 100 ml min–1. the test was performed with a 5 to 8 mg ground sample in the platinum crucible. results and discussion proximate analysis distinct differences in all the proximate components were observed between fibre of hemp and flax genotypes except the dm content. the results revealed a close similarity in the dm content of hemp and flax fibres which varied from 96% to 97.1% (table i). high dm content in fibre cells indicates that these are rich in structural components – carbohydrates, protein, fats, minerals, etc. except water. the density of hemp and flax fibres was the same or very similar and low (1.4–1.5 g cm–3) which could be a great choice for light-weight composite structures (misnon, 2014). low-density fibre has enormous implications in technical textile industries, especially in aerospace and automotive applications for reducing fuel consumption and related fuel costs (shuvo et al. 2020). a careful selection of cultivars (/genotypes) would allow for the optimizing utility of this fibre feature (shuvo, 2020). ash content was analyzed in the range of 1.7% to 17.7% and a significant difference was observed between hemp (12.5–17.7%) and flax (1.7–3.8%) genotypes. the maximum ash was found in hemp genotype meherpur and the minimum in flax genotype chilmari. ash is the residue left after all the moisture and organic matter has been removed at high temperatures. the high ash content of these fibres is a measure of mineral richness (lai and roy, 2004). the maximum quantity of cp, ee and energy value was found in hemp genotypes and minimum in flax genotypes. fibres of two flax genotypes, viz. bd-10708 and bd-1903, contained an exceptionally higher amount of ether extract compared to others (table i). in living organisms, fat is the usually stored form of energy. they are the main structural element of phospholipids and sterols (hashim et al. 2014). the cf and crude carbohydrate (cc) contents showed the maximum value for flax genotype canada (55.32%) and nila (38.25%), respectively and a minimum for hemp genotype brammonbaria (26.51%) and meherpur (23.86%). the energy value of hemp genotypes was higher and ranged from 337.93 to 383.96 kcal 100–1 g (table i). this augmented energy value is due to their greater fat content compared with flax genotypes (ishag et al. 2019). among the different plant parts of hemp, the leaf possessed the maximum amount (23.78%) of cp (audu et al. 2014). on the other hand, fibre contains the highest amount of cf (28.29%) and ash (12%); ee (%) of the leaf was identical to that of fibre except in one genotype brammonbaria (table i) (audu et al. 2014). in flax plants, seeds contain the highest amount of cp (21%) and ee (43.17%), and maximum cf (avg. 51.23%) and cc (avg. 33.38%) in fibre (table i) (ishag et al. 2019). thermogravimetric analysis the tga curves were used to determine the thermal behaviour such as weight loss and residual char level of material at a certain temperature. the thermal behaviour of untreated hemp and flax fibres is shown in fig. 1. fibres of all the genot ypea are lignocellulosic and show almost similar thermal degradation patterns. thermal degradation profiles of the fibres are separated into three different stages. the first stage of degradation started at around 100°c and last up to 180°c. at this stage, about 10% mass loss occurs. mass loss of fibres at around 100°c due to elimination or rapid evaporation of water during the initial stages of heating (ouajai and shanks, 2005). in addition to moisture, some fraction of waxes, pectin, lignin and hemicellulose degraded in this stage (wielage et al. 1999). decomposing of both the hemp and flax fibres takes place slowly up to about 250°c. later the second decomposition started where the maximum mass loss occurred. maximum decomposition took place between 250 and 350°c due to the depolymerization of cellulose and hemicellulose (albano et al. 1999). it is obvious from the proximate analysis (table i) that there is a difference in the chemical composition of the genotypes that affects the thermal stability. the thermal stability of the flax genotypes chilmari and bd-10708 showed higher than the others. the third stage of decomposition begins at a temperature of about 350°c. at this stage, the fibre breaks down to form chars releasing water and carbon dioxide. with a further increase in temperature, the process of formation and digestion of chars takes place. the stable residual mass at 500°c temperature comes mostly from minerals and char residue (gashti et al. 2013). proximate analysis showed that hemp fibre had higher ash content on average than flax fibre (table i). the tga analysis also coincides with the proximate analysis showing a higher residual mass fraction at 500°c for hemp fibres. conclusion the lower ash and ether extract and higher dm, cc and cf of these flax fibres make them (also) suitable for being used in the lightweight composite, textile, pulp and cellulose-based industries. the hemp fibre had higher ash which was reflected by a higher residue at 500°c in tga analysis. high ash content in the hemp fibres will provide high thermal stability and could be used as reinforcement material for composite. further investigations are needed to understand the viability of these flax fibres for different purposes. references albano c, gonzalez j, ichazo m and kaiser d (1999), thermal stability of blends of polyolefins and sisal fiber, polym degrad stab. 66(2): 179-190. . alonso-esteban ji, pinela j, ćirić a, calhelha rc, soković m, ferreira ic, barros l, torija-isasa e and de cortes sánchez-mata m (2022), chemical composition and biological activities of whole and dehulled hemp (cannabis sativa l.) seeds, food chem. 374: 131754. doi: 10.1016/j.foodchem.2021.131754 audu bs, ofojekwu pc, ujah a and ajima mno (2014), phytochemical, proximate composition, amino acid profile and characterization of marijuana (cannabis sativa l.), j phytopharma. 3(1): 35-43. baley c, bourmaud a and davies p (2021), eighty years of composites reinforced by flax fibres: a historical review, composites part a: appl sci manufac 144: 106333. doi: 10.1016/j.compositesa.2021.106333 european parliament and council of the european union, (2011), regulation (eu) no 1169/2011 of the european parliament and of the council of 25 october 2011 on the provision of food information to consumers, amending regulations (ec) no 1924/ 2006 and (ec) no 1925/2006 of the european parliament and of the council, and repealing commission directive 87/250/eec, council directive 90/496/eec, commission directive 1999/10/ec, directive 2000/13/ec of the european parliament and of the council, commission directives 2002/67/ec and 2008/5/ec and commission regulation (ec) no 608/2004. official journal of the european union, l 304: 18-63. galasso i, russo r, mapelli s, ponzoni e, brambilla im, battelli g and reggiani r (2016), variability in seed traits in a collection of cannabis sativa l. genotypes, front plant sci. 7: 688. doi: 10.3389/ fpls. 2016.00688 gashti mp, elahi a and gashti mp (2013), uv radiation inducing succinic acid/silica–kaolinite network on cellulose fiber to improve the functionality, compos b eng. 48: 158-166 girijappa yt, rangappa sm, parameswaranpillai j and siengchin s (2019), natural fibers as sustainable and renewable resource for development of eco-friendly composites: a comprehensive review, front mater 6: 226. doi: 10.3389/fmats.2019.00226 hashim s, bakht t, marwat kb and jan a (2014), medicinal properties, phytochemistry and pharmacology of tribulus terrestris l. (zygophyllaceae), pak j bot. 46(1): 399-404. . ishag oao, khalid aa, abdi a, erwa iy, omer ab and nour ah (2019), proximate composition, physicochemical properties and antioxidant activity of flaxseed, annl res rev biol. 34(2): 1-10. judd a (1995), flaxseed in human nutrition. eds by s.c. cunnane, l.u. thompson. (aocs press, champaign, il) 1995, pp 1-10. kabir aa, moniruzzaman m, gulshan z, rahman am and sarwar akm golam (2018), biomass yield, chemical composition and in vitro gas production of different dhaincha (sesbania spp.) accessions from bangladesh, indian anim nutri. 35(4): 397-402. doi: 10.5958/2231-6744.2018.00060.9 lai pk and roy j (2004), antimicrobial and chemopreventive properties of herbs and spices, curr med chem. 11(11): 1451-1460. milburn w (1813), oriental commerce.vol. 2 (black, parry & co, london) 1813, pp 209-11. misnon mi, islam mm, epaarachchi ja and lau kt (2014), potentiality of utilising natural textile materials for engineering composites applications, mater des. 59: 359-368. doi: 10.1016/j.matdes.2014.03.022 muir ad and westcott nd (2003), flax: the genus linum. (crc press) 2003. mundaragi a, devarajan t, bhat s and jeyabalan s (2017), proximate analysis and mineral composition of potential minor fruits of western ghats of india. scientific papers. series a. agronomy, lx., pp 340-346. o’malley lss (1916), bengal district gazetteers: rajshahi. (bengal secretariat book depot, calcutta) 1996, pp 134-144 o'malley lss (1908), eastern bengal district gazetteers: chittagong (bengal secretariat book depot, calcutta) 1908. ouajai s and shanks ra (2005), composition, structure and thermal degradation of hemp cellulose after chemical treatments, polym degrad stab. 89(2): 327-335. rahman am, nemoto k, matsushima ki, uddin sb and sarwar akm golam (2022), a history of cannabis (ganja) as an economic crop in bangladesh from the late 18th century to 1989, trop agric develop 66(1): 21-32. doi: 10.9790/0837-2509041926 roy s, ali m, amin mn, jianguang s, bhattacharya sk, sen hs, sur d, lutfar lb, rahman ms, hassan ds (2010), jute basics, international jute study group, monipuri para, dhaka. shuvo ii (2020), fibre attributes and mapping the cultivar influence of different industrial cellulosic crops (cotton, hemp, flax, and canola) on textile properties, bioresour bioprocess 7(51): 1-28. doi: 10.1177/ 0040517519886636 shuvo ii, rahman m, vahora t, morrison j, ducharme s and choo-smith lpi (2020), producing light-weight bast fibers from canola biomass for technical textiles, tex res j. 90(11-12): 1311-1325. doi: 10.1186/ s40643-020-00339-1 skoglund g, nockert m and holst b (2013), viking and early middle ages northern scandinavian textiles proven to be made with hemp, sci rep. 3(1): 1-6. doi: 10.1038/srep02686 waris z, iqbal y, arshad hussain s, khan aa, ali a and khan mw (2018), proximate composition, phytochemical analysis and antioxidant capacity of aloe vera, cannabis sativa and mentha longifolia, pure appl biol. 7(3): 1122-1130. doi: 10.19045/ bspab.2018.700131 wielage b, lampke t, marx g, nestler k and starke d (1999), thermogravimetric and differential scanning calorimetric analysis of natural fibres and polypropylene, thermochimica acta. 337(1-2): 169-177. 2016; waris et al. 2018; ishag et al. 2019; alonso-esteban et al. 2022). although the physical properties of hemp and flax fibres are known to us (girijappa et al. 2019), hitherto, no information on the proximate composition of fibres of bangladeshi genotypes of these two important fibre-yielding crops is available. the constituent fibre properties influence application of textiles in many fields e.g., composites, automotive, marines, aerospace, electronics, civil construction, nanotechnology, biomedical, as well as the apparel or clothing industry (shuvo, 2020). we have, therefore, reported the proximate composition and thermogravimetric analysis data of 3 hemp and 6 flax genotypes here. materials and methods the proximate analysis and thermogravimetric analysis (of fibres) of six flax genotypes and three hemp genotypes were carried out to understand their suitability in different applications. hemp seeds were collected from different locations in bangladesh (detailed collection information will be available upon request) and the genotypes are named accordingly, viz. brammonbaria, chittagang and meherpur. the hemp plants were grown (in a confined area) at botanical garden, department of crop botany, bangladesh agricultural university. flax fibres were collected with the ribbon retting method (roy et al. 2010) and sun-dried properly. the flax fibres of 6 genotypes, harvested from another experiment in the same year, were collected from the laboratory of plant systematics of the same department. the proximate composition analysis viz. dry matter (dm), crude protein (cp), crude fibre (cf), ash and ether extract (crude fat; ee), were accomplished at the laboratory of department of animal science, bangladesh agricultural university, mymensingh following standard procedure (kabir et al. 2018). the crude carbohydrate was calculated following mundaragi et al. (2017). crude carbohydrate (%) = 100 – [moisture (%) + protein (%) + fibre (%) + fat (%) + ash (%)] the calorific value or the total energy value of fruits in kcal100–1 g was calculated with the help of the following equation (european parliament and council of the european union, 2011). energy value (kcal 100–1 g) = 4 × protein + 9 × fat + 4 × carbohydrate + 2 × fibre 99 mineral nutrition of rice and post-harvest soils influenced by self-made organic composts s. akter*, h. r. khan and m. k. saha department of soil, water and environment, university of dhaka, dhaka 1000, bangladesh abstract using self-made organic composts i.e., rice hull compost (rhc), rice straw compost (rsc), sawdust compost (sdc), and vermicompost (v) an experiment was conducted to evaluate their responses on mineral nutrition of rice and post-harvest soils under field condition. the total nitrogen contents among the treatments ranged from 9.6 21.4, phosphorus: 1.1 – 4.42, potassium: 3.86 7.27, sulfur: 11.9 – 19.7, calcium: 3.30 – 11.87 and magnesium: 2.76 – 5.54 g kg-1 at the maturity stage of rice plants which were found to be positively influenced by the applied organic composts. the nutrient status of the post-harvest soils was also influenced by the applied organic composts. the maximum amount of 78.29 mg kg-1 available n was recorded in the t3 treatment, where available nitrogen content increased by 85.65% as compared to the control plot. there were significant (p ≤ 0.05) increases in other nutrient contents with the increased doses of the composts under rice production. keywords: nutrition of rice plant; post-harvest soils; self-made organic compost; suitable source *corresponding author’s e-mail: suma.soil93@gmail.com available online at www.banglajol.info bangladesh j. sci. ind. res. 58(2), 99-106, 2023 introduction rice (oryza sativa l.) is the second most important staple food as it fulfills the dietary requirement of over half of the human population and considers the major food crop of economic significance in asia (ahmed et al. 2021). among south asian countries, bangladesh ranks second in terms of areas and production of rice, where it is being cultivated on over 82% of the total cropped land, while aman rice shares over 37% of total rice production (bbs, 2020). in the country, with advancement of time, nutrient mining increases due to increasing cropping intensity (191%; bbs, 2017), use of modern varieties, nutrient leaching, gaseous loss, soil erosion and imbalanced application of fertilizers with no or little addition of organic manure. to ensure the food security of the increasing population, high-yielding rice cultivars are being cultivated on large scale with intensive use of chemical fertilizers, which not only degraded soil fertility but also polluting associated environments and affecting food chain and ultimately affect human health. higher is the crop yield, higher is the nutrient removal from soil. nutrient deficiency in this country’s soils has arisen chronologically n, p, k and s (jahiruddin and satter, 2010). about 45% of net cultivable areas of bangladesh contain less than 1% organic matter (frg, 2012). organic manure is a good source of nutrients, especially n, p and s and it's a good means of soil rejuvenation (jeptoo et al. 2013). so, use of organic matter could be an inevitable practice in the coming years for ensuring sustainable crop productivity without affecting soil fertility (heikamp et al. 2011). numerous actions have been taken to improve soil fertility and productivity. the most effective measure is increasing the organic input, such as application of organic manure or compost (xin et al. 2017) and straw incorporation (zhang et al. 2016). crop straw, an easy-to-get, nutrient-rich resource, has great value for improving soil fertility (tan et al. 2017). several studies have reported that crop straw is rich in nutrients and organic materials, can be treated as a natural organic fertilizer, and used as an alternative to chemical fertilizers (wang et al. 2017). therefore, straw amalgamation seems hopeful to maintain and restore soil fertility. however, until now, the use of straw incorporation to increase crop yield is still a matter of argument since studies in different climates and soil types have led to inconclusive results (pituello et al. 2016). it has been reported that straw incorporation has significant valuable effects on crop yields and soil properties. for instance, straw incorporation can increase crop yields (yang et al. 2016), soil organic matter and other soil nutrients (zhang et al. 2018). straw return can also improve soil physical properties, such as by increasing hydraulic conductivity, decreasing bulk density, and enhancing aggregate formation (yang et al. 2016). vermicompost is a nourishing organic fertilizer having high amount of humus, nitrogen 2–3%, phosphorous 1.55–2.25%, potassium 1.85–2.25%, micronutrients, more beneficial for soil microbes like ‘nitrogen fixing bacteria’ and mycorrhizal fungi. vermicompost has been scientifically proved as miracle plant growth enhancer (guerrero, 2010). ansari and ismail (2012) reported that worms vermicompost contains 7.37 % nitrogen and 19.58% phosphorous as p2o5. microbial population of n2fixing bacteria and actinomycetes increases by the application of vermicompost. the amplified microbial activities improve the availability of soil phosphorous and nitrogen. vermicomposting is an aerobic, biological method and is proficient to convert eco-friendly hummus like organic substances (chanda et al. 2011). vermicompost stimulates to influence the microbial activity of soil, increases the availability of oxygen, maintains normal soil temperature, increases soil porosity and infiltration of water, improves nutrient content and increases growth, yield and quality of the plant (arora et al. 2011). rice hull and sawdust are also important agricultural amendments. growth and yield components of rice grown in saline soil were found to be increased significantly (p ≤ 0.05) by the application of rice hull, rice straw and sawdust alone and in combination (akter et al. 2018). the physico-chemical properties and nutrient status of post-harvest soils were also found to be influenced by the application of these amendments (akter and khan, 2019). composting is a low-cost natural way of recycling and stabilizing organic matter under thermophilic temperature that forms a pathogen-free substrate, beneficial to crops (gurtler et al. 2018; somerville et al. 2020). low-income farmers found it more advantageous to them. composting was found to be a promising practice that brought organic materials to a certain stage by narrowing down its c:n ratio where nutrients are easily accessible to plants (palaniveloo et al. 2020). partey et al. (2018) and dinesh et al. (2011), had consolidated that biomass needs to decompose for making n available to crops. thus, composting locally available organic amendments (oas) is essential for a healthy and sustainable agro-ecosystem in different climatic conditions. therefore, the objectives of the study were to evaluate the nutrient statuses of post-harvest soils and rice plants grown in aman season as influenced by the different rates of organic composts applied under field condition. materials and methods study site and experimental design in patuakhali a district of bangladesh, the field experiment was conducted in bilbilash of bauphal upazila (map i), which is located between 22°20ʹ00ʺn and 90°20ʹ00ʺe longitude within agro-ecological zone-13 named as ganges tidal floodplain. the climatic condition of this area is usually known as ‘tropical monsoon climate’. the area mainly enjoys three seasons such as rainy, dry and summer season. the experiment was carried out following completely randomized block design with the self-made organic composts, such as, rice hull compost (rhc), rice straw compost (rsc), sawdust compost (sdc) and vermicompost (v) corresponding to the rates of 0, 2, 4 and 8 t ha-1 of each organic compost at aman season during august to december, 2018. there were 13 plots having individual treatment (table i) in the experimental area, each unit plot size was 16 m2 (4m×4m) and replications were considered within the plot. selected properties of potential amendments used and initial soils at field site are presented in the tables ii and iii. transplantation following subsequent protocols basal doses of n, p2o5, and k2o from urea, tsp, and mop fertilizers were applied at the rates of 40, 30, and 15 kg ha-1, respectively considering soil amendments and initial contents of the nutrients. during field preparation, the tsp, mop, and half of the urea were applied in their entirety after being thoroughly mixed with the field soil. the remaining urea was top dressed in two splits, one at the beginning of the rice panicle and another at the active tillering stage. three seedlings per hill of the br 25 variety, which were thirty days old and in good health, were transplanted. row to row and hill to hill distances were each 20 and 22 cm, respectively. no irrigation was required for this study for the growth of rice in this season. intercultural operations such as, weeding, pesticide use, etc. were done as per requirement. sample collection and analyses plant samples were collected from each plot just after harvesting. soil samples were collected from 3 spots as replications of each plot of active root zone (0-15 cm) with the help of an auger. soil samples were then stored treatment wise in polythene bags with proper labeling. after sun drying and grounding the samples were then passed through 2 mm sieve and stored properly in air tight plastic pots for further analyses. the collected plant samples were sun dried and weighed. after sun drying a portion of the collected plant samples were oven dried at 65⁰c and then grinded and stored in air tight plastic pots for laboratory analyses. all the laboratory analyses were done following standard methods. statistical analyses pearson correlation and regression analyses between treatments and mineral nutrition of rice plants, analysis of variance (anova) and tukey’s range test at 5% (p≤ 0.05) level were done for the interpretation of the experimental results. results and discussion mineral nutrition of rice plants the total nitrogen, phosphorus, potassium, sulfur, calcium and magnesium contents at maturity stage of rice plants grown under field condition were significantly (p≤0.05) influenced by the application of variable indigenous organic amendments (rice hull compost, rice straw compost, sawdust compost and vermicompost) during aman season (table iv and fig.1). pearson correlation and regression analyses have been performed between the different treatments and mineral nutrition of rice plant tissues (table v). significance has been determined based on p values whether they were <0.05 or not. the total nitrogen (r = 0.78***), phosphorus (r = 0.77**), potassium (r = 0.75**), sulfur (r = 0.82***), calcium (r = 0.82***) and magnesium (r = 0.60*) contents of the tested rice plant (br 25) tissues were significantly correlated with the applied organic composts and these correlations confirmed that the different sources of organic materials positively influenced the nutrition of rice plant tissues which ultimately regulate the edible part (grain) of the rice crops. according to graham et al. (2012), people taking cereal based diets still suffering from hidden hunger of nutrients due to low level and low bioavailability of essential elements. the present results demonstrated that the nitrogen content in rice straw increased with the increased rate of the application of organic composts. the maximum nitrogen contents in the rice plant tissues were recorded at v8 treatment for the tested variety. among the applied composts, vermicompost (18.63 g kg-1n) ranked first followed by rice straw compost (17.40 g kg-1), sawdust compost (14.57g kg-1) and rice hull compost (13.33 g kg-1), regardless of their doses. phosphorus contents in rice plant tissues increased with the higher rates of the different composts. the highest (4.42 g kg-1) and lowest (1.10 g kg-1) contents of total phosphorus were recorded in the t12 (v8) and t0 (control) treatments. the rest of the above-mentioned nutrients were exerted the similar trends as those obtained by the p and n contents by the different organic composts. the nutrition of rice shoots was influenced by the direction of vermicompost > rice straw compost > sawdust compost > rice hull compost for the studied variety of rice grown under field condition. nutrient status of post-harvest soils rice production during t. aman season, the available n contents in the post-harvest soils increased significantly (p ≤ 0.05) by the application of vermicompost, rice hull compost, rice straw compost and sawdust compost (table vi and fig. 2). the maximum amount of available n (78.29 mg kg-1) was recorded in t3 (rhc8) treatment, where available nitrogen content increased 85.65% as compared to control plot. at the same dose (8 t ha-1), the sawdust compost treatment ranked second for the available nitrogen content (62.31 mg kg-1) at post-harvest soils followed by rsc8 treatment (60.76 mg kg-1). there were significant (p≤0.05) increase in available phosphorus and sulfur, exchangeable potassium, calcium and magnesium at post-harvest soils with the increased doses of the organic amendments under rice production (table vi). soils treated with vermicompost at the rate of 8 t ha-1 was found to have significantly more phosphorus (12.57 mg kg-1) as compared to control plot. the rice straw compost and sawdust compost each at 8 t ha-1 were showed almost similar trends in the increment of available phosphorus contents in post-harvest soils followed by rice hull compost. the other nutrients of post-harvest soils followed the similar trends as that of phosphorus, except for the exchangeable potassium, where rice straw compost at the highest rate (8 t ha-1) exhibited the best response (0.97 c molc kg -1) than those of the other treatments. the maximum amounts of available sulfur, exchangeable calcium and magnesium were obtained from the highest dose of vermicompost and the minimum amounts were attained by the control plot. the trend of increments of all these nutrients were more pronounced with the higher rates of the applied organic amendments indicate that all the applied organic composts are suitable sources for improving nutrient statuses of soils. pearson correlation and regression analyses also indicate the strong positive relationship between the treatments and nutrient statuses of post-harvest soils (table vii). the current findings are in consistent with those of xin et al. (2017). many steps have been made to improve soil fertility and productivity, according to them. increased organic input, such as organic manure, compost, and straw integration, are the most effective approaches. crop straw, a cheap and nutrient-dense material, offers a lot of potential for enhancing soil fertility (tan et al. 2017). crop straw, which is high in nutrients and organic elements, can be treated as a natural organic fertilizer and utilized as an alternative to chemical fertilizers, according to the studies of wang et al. (2017). as a result, straw integration appears to be a potential method for maintaining and restoring soil fertility, the burning issue of present day. because, mineral elements are required for the healthy growth and development of both plants and humans. the plant roots take up the mineral nutrients from soil and transported them to the edible parts for human consumption through various transporters. for human health, an ideal future crop should be rich in essential mineral elements but with less toxic elements in the edible parts. still, it is estimated that nearly 2 billion people are suffering from deficiency of nutrients because of low availability of mineral elements in soil and/or low accumulation/bioavailability of mineral elements in edible parts (graham et al. 2012). this so-called hidden hunger is an especially serious health problem for people subsisting on cereal-based diets because cereals such as rice usually contain a low level of mineral elements as well as low bioavailability (grebmer et al. 2014; nakandalage and seneweera, 2018). on the other hand, rapid urbanization and industrialization cause contamination by toxic elements in many soils used for crop production (zhao et al. 2010; clemens and ma, 2016), which threaten our health throughout the food chain. therefore, it is extremely important to boost essential nutrients (both density and bioavailability) and reduce toxic elements in edible parts of cereals for human health. conclusion the present research findings conclude that the locally made organic composts using indigenous organic materials had potential to improve soil fertility and provide nutrients for rice production. significant positive correlation between the treatments and mineral nutrients of rice plants confirmed the strong relationship of organic farming for sustainable agriculture. there were significant (p ≤ 0.05) increase in available phosphorus and sulfur, exchangeable potassium, calcium and magnesium at post-harvest soils with the increased doses of amendments under rice production. the nutrition of rice plants grown under field condition was influenced most by the vermicompost and followed the order of the treatments as rice straw compost > sawdust compost > rice hull compost for the studied variety of rice. these results resemble that the further researches are needed to find out the suitable doses and types of the amendments. however, the applied organic fertilizers were found to have responses on the nutritional statuses of rice shoot and post-harvest soils and these might be effective for the nutritional balance of the rice variety and ultimately will be helpful for country’s penniless people to combat their existing and future demand of quality rice. acknowledgement the study was carried out under a project of the climate change trust fund (cctf) titled ‘assessment of impacts of climate change on soil health and food security, and adaptation of climate-smart agriculture in most adversely affected areas of bangladesh’ through the moefcc, government of the peoples’ republic of bangladesh. the project was implemented in two phases (phase i: jan.’17 to dec.’18, code 410 duand phase ii: jan.’19 to dec.’22, code 573 du) within six years. we are also grateful to the project staff and relevant officers/staff of the swed-du, du, moe and moefcc of gob, who performed for the successful completion of the study. references ahmed s, alam mj, hossain a, islam ak, awan th, soufan w, qahtan aa, okla mk and sabagh si (2021), interactive effect of weeding regimes, rice cultivars, and seeding rates influence the rice-weed competition under dry direct-seeded condition, sustainability. 13: 317-321. doi: 10.3390/su13010317 akter s and khan hr (2019), influence of rice hull, rice straw, sawdust and moisture levels on selected properties of post harvested saline soils under variable conditions of rice cultivation, national university journal of science. 6(1): 61-74. akter s, khan hr, hossain 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(london: academic press), pp 209-224. palaniveloo k, amran ma, norhashim na, mohamad-fauzi n, peng-hui f, hui-wen l, kai-lin y, jiale l, chian-yee mg and jing-yi l (2020), food waste composting and microbial community structure profiling, processes. 8: 723. doi: org/10.3390/ pr8060723 partey st, thevathasan nv, zougmoré rb and preziosi rf (2018), improving maize production through nitrogen supply from tenrarely-used organic resources in ghana, agrofor syst. 92: 375-387. doi: 10.1007/ s10457-016-0035-8 pituello c, polese r, morari f and berti a (2016), outcomes from a long-term study on crop residue effects on plant yield and nitrogen use efficiency in contrasting soils, eur j agron. 77: 179-187. doi: 10.1016/j. eja.2015.11.027 somerville pd, farrell c, may pb and livesley sj (2020), biochar and compost equally improve urban soil physical and biological properties and tree growth, with no added benefit in combination, sci total environ. 706: 135-736. doi: 10.1016/j.scitotenv. 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z, jia z, yang b, han q and ren x (2016), effects of straw incorporation on the soil nutrient contents, enzyme activities, and crop yield in a semiarid region of china, soil tillage res. 160: 65-72. doi: 10.1016/j.still.2016.02.006 zhang y, liu y, zhang g, guo x, sun z and li t (2018), the effects of rice straw and biochar applications on the microbial community in a soil with a history of continuous tomato planting history, agronomy. 8. doi: 10.3390/agronomy8050065 zhao fj, mcgrath sp and meharg aa (2010), arsenic as a food chain contaminant: mechanisms of plant uptake and metabolism and mitigation strategies, annu rev plant biol. 61: 535-559. doi: 10.1146/annurev-arplant-042809-112152 doi: https://doi.org/10.3329/bjsir.v58i2.64570 received: 26 february 2023 revised: 17 april 2023 accepted: 21 may 2023 mineral nutrition of rice and post-harvest soils influenced by self-made organic composts 58(2) 2023100 however, until now, the use of straw incorporation to increase crop yield is still a matter of argument since studies in different climates and soil types have led to inconclusive results (pituello et al. 2016). it has been reported that straw incorporation has significant valuable effects on crop yields and soil properties. for instance, straw incorporation can increase crop yields (yang et al. 2016), soil organic matter and other soil nutrients (zhang et al. 2018). straw return can also improve soil physical properties, such as by increasing hydraulic conductivity, decreasing bulk density, and enhancing aggregate formation (yang et al. 2016). vermicompost is a nourishing organic fertilizer having high amount of humus, nitrogen 2–3%, phosphorous 1.55–2.25%, potassium 1.85–2.25%, micronutrients, more beneficial for soil microbes like ‘nitrogen fixing bacteria’ and mycorrhizal fungi. vermicompost has been scientifically proved as miracle plant growth enhancer (guerrero, 2010). ansari and ismail (2012) reported that worms vermicompost contains 7.37 % nitrogen and 19.58% phosphorous as p2o5. microbial population of n2fixing bacteria and actinomycetes increases by the application of vermicompost. the amplified microbial activities improve the availability of soil phosphorous and nitrogen. vermicomposting is an aerobic, biological method and is proficient to convert eco-friendly hummus like organic substances (chanda et al. 2011). vermicompost stimulates to influence the microbial activity of soil, increases the availability of oxygen, maintains normal soil temperature, increases soil porosity and infiltration of water, improves nutrient content and increases growth, yield and quality of the plant (arora et al. 2011). rice hull and sawdust are also important agricultural amendments. growth and yield components of rice grown in saline soil were found to be increased significantly (p ≤ 0.05) by the application of rice hull, rice straw and sawdust alone and in combination (akter et al. 2018). the physico-chemical properties and nutrient status of post-harvest soils were also found to be influenced by the application of these amendments (akter and khan, 2019). composting is a low-cost natural way of recycling and stabilizing organic matter under thermophilic temperature that forms a pathogen-free substrate, beneficial to crops (gurtler et al. 2018; somerville et al. 2020). low-income farmers found it more advantageous to them. composting was found to be a promising practice that brought organic materials to a certain stage by narrowing down its c:n ratio where nutrients are easily accessible to plants (palaniveloo et al. 2020). partey et al. (2018) and dinesh et al. (2011), had consolidated that biomass needs to decompose for making n available to crops. thus, composting locally available organic amendments (oas) is essential for a healthy and sustainable agro-ecosystem in different climatic conditions. therefore, the objectives of the study were to evaluate the nutrient statuses of post-harvest soils and rice plants grown in aman season as influenced by the different rates of organic composts applied under field condition. materials and methods study site and experimental design in patuakhali a district of bangladesh, the field experiment was conducted in bilbilash of bauphal upazila (map i), which is located between 22°20ʹ00ʺn and 90°20ʹ00ʺe longitude within agro-ecological zone-13 named as ganges tidal floodplain. the climatic condition of this area is usually known as ‘tropical monsoon climate’. the area mainly enjoys three seasons such as rainy, dry and summer season. the experiment was carried out following completely randomized block design with the self-made organic composts, such as, rice hull compost (rhc), rice straw compost (rsc), sawdust compost (sdc) and vermicompost (v) corresponding to the rates of 0, 2, 4 and 8 t ha-1 of each organic compost at aman season during august to december, 2018. there were 13 plots having individual treatment (table i) in the experimental area, each unit plot size was 16 m2 (4m×4m) and replications were considered within the plot. selected properties of potential amendments used and initial soils at field site are presented in the tables ii and iii. transplantation following subsequent protocols basal doses of n, p2o5, and k2o from urea, tsp, and mop fertilizers were applied at the rates of 40, 30, and 15 kg ha-1, respectively considering soil amendments and initial contents of the nutrients. during field preparation, the tsp, mop, and half of the urea were applied in their entirety after being thoroughly mixed with the field soil. the remaining urea was top dressed in two splits, one at the beginning of the rice panicle and another at the active tillering stage. three seedlings per hill of the br 25 variety, which were thirty days old and in good health, were transplanted. row to row and hill to hill distances were each 20 and 22 cm, respectively. no irrigation was required for this study for the growth of rice in this season. intercultural operations such as, weeding, pesticide use, etc. were done as per requirement. sample collection and analyses plant samples were collected from each plot just after harvesting. soil samples were collected from 3 spots as replications of each plot of active root zone (0-15 cm) with the help of an auger. soil samples were then stored treatment wise in polythene bags with proper labeling. after sun drying and grounding the samples were then passed through 2 mm sieve and stored properly in air tight plastic pots for further analyses. the collected plant samples were sun dried and weighed. after sun drying a portion of the collected plant samples were oven dried at 65⁰c and then grinded and stored in air tight plastic pots for laboratory analyses. all the laboratory analyses were done following standard methods. statistical analyses pearson correlation and regression analyses between treatments and mineral nutrition of rice plants, analysis of variance (anova) and tukey’s range test at 5% (p≤ 0.05) level were done for the interpretation of the experimental results. results and discussion mineral nutrition of rice plants the total nitrogen, phosphorus, potassium, sulfur, calcium and magnesium contents at maturity stage of rice plants grown under field condition were significantly (p≤0.05) influenced by the application of variable indigenous organic amendments (rice hull compost, rice straw compost, sawdust compost and vermicompost) during aman season (table iv and fig.1). pearson correlation and regression analyses have been performed between the different treatments and mineral nutrition of rice plant tissues (table v). significance has been determined based on p values whether they were <0.05 or not. the total nitrogen (r = 0.78***), phosphorus (r = 0.77**), potassium (r = 0.75**), sulfur (r = 0.82***), calcium (r = 0.82***) and magnesium (r = 0.60*) contents of the tested rice plant (br 25) tissues were significantly correlated with the applied organic composts and these correlations confirmed that the different sources of organic materials positively influenced the nutrition of rice plant tissues which ultimately regulate the edible part (grain) of the rice crops. according to graham et al. (2012), people taking cereal based diets still suffering from hidden hunger of nutrients due to low level and low bioavailability of essential elements. the present results demonstrated that the nitrogen content in rice straw increased with the increased rate of the application of organic composts. the maximum nitrogen contents in the rice plant tissues were recorded at v8 treatment for the tested variety. among the applied composts, vermicompost (18.63 g kg-1n) ranked first followed by rice straw compost (17.40 g kg-1), sawdust compost (14.57g kg-1) and rice hull compost (13.33 g kg-1), regardless of their doses. phosphorus contents in rice plant tissues increased with the higher rates of the different composts. the highest (4.42 g kg-1) and lowest (1.10 g kg-1) contents of total phosphorus were recorded in the t12 (v8) and t0 (control) treatments. the rest of the above-mentioned nutrients were exerted the similar trends as those obtained by the p and n contents by the different organic composts. the nutrition of rice shoots was influenced by the direction of vermicompost > rice straw compost > sawdust compost > rice hull compost for the studied variety of rice grown under field condition. nutrient status of post-harvest soils rice production during t. aman season, the available n contents in the post-harvest soils increased significantly (p ≤ 0.05) by the application of vermicompost, rice hull compost, rice straw compost and sawdust compost (table vi and fig. 2). the maximum amount of available n (78.29 mg kg-1) was recorded in t3 (rhc8) treatment, where available nitrogen content increased 85.65% as compared to control plot. at the same dose (8 t ha-1), the sawdust compost treatment ranked second for the available nitrogen content (62.31 mg kg-1) at post-harvest soils followed by rsc8 treatment (60.76 mg kg-1). there were significant (p≤0.05) increase in available phosphorus and sulfur, exchangeable potassium, calcium and magnesium at post-harvest soils with the increased doses of the organic amendments under rice production (table vi). soils treated with vermicompost at the rate of 8 t ha-1 was found to have significantly more phosphorus (12.57 mg kg-1) as compared to control plot. the rice straw compost and sawdust compost each at 8 t ha-1 were showed almost similar trends in the increment of available phosphorus contents in post-harvest soils followed by rice hull compost. the other nutrients of post-harvest soils followed the similar trends as that of phosphorus, except for the exchangeable potassium, where rice straw compost at the highest rate (8 t ha-1) exhibited the best response (0.97 c molc kg -1) than those of the other treatments. the maximum amounts of available sulfur, exchangeable calcium and magnesium were obtained from the highest dose of vermicompost and the minimum amounts were attained by the control plot. the trend of increments of all these nutrients were more pronounced with the higher rates of the applied organic amendments indicate that all the applied organic composts are suitable sources for improving nutrient statuses of soils. pearson correlation and regression analyses also indicate the strong positive relationship between the treatments and nutrient statuses of post-harvest soils (table vii). the current findings are in consistent with those of xin et al. (2017). many steps have been made to improve soil fertility and productivity, according to them. increased organic input, such as organic manure, compost, and straw integration, are the most effective approaches. crop straw, a cheap and nutrient-dense material, offers a lot of potential for enhancing soil fertility (tan et al. 2017). crop straw, which is high in nutrients and organic elements, can be treated as a natural organic fertilizer and utilized as an alternative to chemical fertilizers, according to the studies of wang et al. (2017). as a result, straw integration appears to be a potential method for maintaining and restoring soil fertility, the burning issue of present day. because, mineral elements are required for the healthy growth and development of both plants and humans. the plant roots take up the mineral nutrients from soil and transported them to the edible parts for human consumption through various transporters. for human health, an ideal future crop should be rich in essential mineral elements but with less toxic elements in the edible parts. still, it is estimated that nearly 2 billion people are suffering from deficiency of nutrients because of low availability of mineral elements in soil and/or low accumulation/bioavailability of mineral elements in edible parts (graham et al. 2012). this so-called hidden hunger is an especially serious health problem for people subsisting on cereal-based diets because cereals such as rice usually contain a low level of mineral elements as well as low bioavailability (grebmer et al. 2014; nakandalage and seneweera, 2018). on the other hand, rapid urbanization and industrialization cause contamination by toxic elements in many soils used for crop production (zhao et al. 2010; clemens and ma, 2016), which threaten our health throughout the food chain. therefore, it is extremely important to boost essential nutrients (both density and bioavailability) and reduce toxic elements in edible parts of cereals for human health. conclusion the present research findings conclude that the locally made organic composts using indigenous organic materials had potential to improve soil fertility and provide nutrients for rice production. significant positive correlation between the treatments and mineral nutrients of rice plants confirmed the strong relationship of organic farming for sustainable agriculture. there were significant (p ≤ 0.05) increase in available phosphorus and sulfur, exchangeable potassium, calcium and magnesium at post-harvest soils with the increased doses of amendments under rice production. the nutrition of rice plants grown under field condition was influenced most by the vermicompost and followed the order of the treatments as rice straw compost > sawdust compost > rice hull compost for the studied variety of rice. these results resemble that the further researches are needed to find out the suitable doses and types of the amendments. however, the applied organic fertilizers were found to have responses on the nutritional statuses of rice shoot and post-harvest soils and these might be effective for the nutritional balance of the rice variety and ultimately will be helpful for country’s penniless people to combat their existing and future demand of quality rice. acknowledgement the study was carried out under a project of the climate change trust fund (cctf) titled ‘assessment of impacts of climate change on soil health and food security, and adaptation of climate-smart agriculture in most adversely affected areas of bangladesh’ through the moefcc, government of the peoples’ republic of bangladesh. the project was implemented in two phases (phase i: jan.’17 to dec.’18, code 410 duand phase ii: jan.’19 to dec.’22, code 573 du) within six years. we are also grateful to the project staff and relevant officers/staff of the swed-du, du, moe and moefcc of gob, who performed for the successful completion of the study. references ahmed s, alam mj, hossain a, islam ak, awan th, soufan w, qahtan aa, okla mk and sabagh si (2021), interactive effect of weeding regimes, rice cultivars, and seeding rates influence the rice-weed competition under dry direct-seeded condition, sustainability. 13: 317-321. doi: 10.3390/su13010317 akter s and khan hr (2019), influence of rice hull, rice straw, sawdust and moisture levels on selected properties of post harvested saline soils under variable conditions of rice cultivation, national university journal of science. 6(1): 61-74. akter s, khan hr, hossain ms, saha mk and farzana f (2018), response of rice grown in saline soil as influenced by the application of agricultural amendments and moisture regimes, j biodivers conserv bioresour manag. 4(2): 33-42. doi: https://doi.org/ 10.3329/jbcbm.v4i2.39845 ansari aa and ismail sa (2012), role of earthworms in vermtechnology, j agric technol. 8(2): 405-415. https://www.ijat-aatsea.com arora vk, singh cb, sidhu as and thind ss (2011), irrigation, tillage and mulching effects on soybean yield and water productivity in relation to soil texture, agric water manag. 98(4): 563-568. https://doi.org/10.1016/j.agwat .2010.10.004 bbs (2017), bangladesh bureau of statistics. the year book of agricultural statistics of bangladesh. stat. div. minis. planning, govt. peoples repub. bangladesh, dhaka. bbs (2020), summary crop statistics and crop indices (2019-2020). bangladesh bureau of statistics division, govt. of the people’s republic of bangladesh: dhaka, bangladesh. pp 35-37. chanda gc, bhunia g and chakraborty sk (2011), the effect of vermicompost and other fertilizers on cultivation of tomato plants, j hortic for. 3: 42-45. http://www.acade mic journals.org/jhf clemens s and ma jf (2016), toxic heavy metal and metalloid accumulation in crop plants and foods, annu rev plant biol. 67: 489-512. doi: 10.1146/annurev-arplant-043015-112301 dinesh r, suryanarayana ma, nair ak and chaudhuri sg (2011), leguminous cover crop effects on nitrogen mineralization rates and kinetics in soils, j agron crop sci. 187: 161-166. doi: 10.1046/j.1439-037x. 2001. 00512.x frg (2012), (fertilizer recommendation guide). bangladesh agricultural research council (barc), dhaka, bangladesh. graham rd, knez m and welch rm (2012), how much nutritional iron deficiency in humans globally is due to an underlying zinc deficiency, adv agron. 1-40. doi: 10.1016/b978-0-12-394276-0.00001-9 grebmer bkv, saltzman a, birol e, wiesmann d, prasai n, yins, yohannes y, menon p, thompson j and sonntag a (2014), 2014 global hunger index: the challenge of hidden hunger (washington, dc: international food policy research institute), pp 56. doi: http://dx.doi.org/10.2499/9780896299580 guerrero rd (2010), vermicompost production and its use for crop production in the philippines, international journal of global environmental issues. 10(3/4): 378-383. doi: 10.1504/ijgenvi.2010.037278 gurtler jb, doyle mp, erickson mc, jiang x, millner p and sharma m (2018), composting to inactivate food borne pathogens for crop soil application, a review j food prot.81: 1821-1837. doi: 10.4315/0362-028x.jfp-18-217 heitkamp f, raupp j and ludwig b (2011), soil organic matter pools and crop yields as affected by the rate of farmyard manure and use of biodynamic preparations in a sandy soil, organic agriculture. 11: 111-124. doi: 10.1007/s13165-011-0010-7 jahiruddin m and satter ma (2010), research priority in agriculture and development of vision document-2030 and beyond. land and soil resource management. bangladesh gricultural research council. dhaka. jeptoo a, aguyoh jn and saidi m (2013), improving carrot yield and quality through the use of bio-slurry manure, sustainable agricultural research. 2(1): 164-172. doi: 10.5539/sar.v2n1p164 nakandalage n and seneweera s (2018), micronutrients useefficiency of crop-plants under changing climate. in plant micronutrient use efficiency, m.a. hossain, t. kamiya, d.j. burritt, l.-s.p. tran and t. fujiwara, eds. (london: academic press), pp 209-224. palaniveloo k, amran ma, norhashim na, mohamad-fauzi n, peng-hui f, hui-wen l, kai-lin y, jiale l, chian-yee mg and jing-yi l (2020), food waste composting and microbial community structure profiling, processes. 8: 723. doi: org/10.3390/ pr8060723 partey st, thevathasan nv, zougmoré rb and preziosi rf (2018), improving maize production through nitrogen supply from tenrarely-used organic resources in ghana, agrofor syst. 92: 375-387. doi: 10.1007/ s10457-016-0035-8 pituello c, polese r, morari f and berti a (2016), outcomes from a long-term study on crop residue effects on plant yield and nitrogen use efficiency in contrasting soils, eur j agron. 77: 179-187. doi: 10.1016/j. eja.2015.11.027 somerville pd, farrell c, may pb and livesley sj (2020), biochar and compost equally improve urban soil physical and biological properties and tree growth, with no added benefit in combination, sci total environ. 706: 135-736. doi: 10.1016/j.scitotenv. 2019.135736 tan d, liu z, jiang l, luo j and li j (2017), long-term potash application and wheat straw return reduced soil potassium fixation and affected crop yields in north china, nutr cycl agroecosyst. doi: 10.1007/s10705 017-9843-0 wang w, sardans j, wang c, pan t, zeng c, lai d, bartrons m and peñuelas j (2017), straw application strategy to optimize nutrient release in a southeastern china rice cropland, agronomy. 7. doi: 10.3390/agronomy 7040084 xin x, qin s, zhang j, zhu a, yang w and zhang x (2017), yield, phosphorus use efficiency and balance response to substituting long-term chemical fertilizer use with organic manure in a wheat-maize system, field crop res. 208: 27-33. doi: 10.1016/j.fcr.2017.03.011 yang hs, xu mm, koide rt, liu q, dai yj, liu l and bian xm (2016), effects of ditch-buried straw return on water percolation, nitrogen leaching and crop yields in a rice-wheat rotation system, j sc. food agric. 96: 1141-1149. doi: 10.1002/jsfa.7196 zhang p, chen x, wei t, yang z, jia z, yang b, han q and ren x (2016), effects of straw incorporation on the soil nutrient contents, enzyme activities, and crop yield in a semiarid region of china, soil tillage res. 160: 65-72. doi: 10.1016/j.still.2016.02.006 zhang y, liu y, zhang g, guo x, sun z and li t (2018), the effects of rice straw and biochar applications on the microbial community in a soil with a history of continuous tomato planting history, agronomy. 8. doi: 10.3390/agronomy8050065 zhao fj, mcgrath sp and meharg aa (2010), arsenic as a food chain contaminant: mechanisms of plant uptake and metabolism and mitigation strategies, annu rev plant biol. 61: 535-559. doi: 10.1146/annurev-arplant-042809-112152 akter, khan and saha 101 however, until now, the use of straw incorporation to increase crop yield is still a matter of argument since studies in different climates and soil types have led to inconclusive results (pituello et al. 2016). it has been reported that straw incorporation has significant valuable effects on crop yields and soil properties. for instance, straw incorporation can increase crop yields (yang et al. 2016), soil organic matter and other soil nutrients (zhang et al. 2018). straw return can also improve soil physical properties, such as by increasing hydraulic conductivity, decreasing bulk density, and enhancing aggregate formation (yang et al. 2016). vermicompost is a nourishing organic fertilizer having high amount of humus, nitrogen 2–3%, phosphorous 1.55–2.25%, potassium 1.85–2.25%, micronutrients, more beneficial for soil microbes like ‘nitrogen fixing bacteria’ and mycorrhizal fungi. vermicompost has been scientifically proved as miracle plant growth enhancer (guerrero, 2010). ansari and ismail (2012) reported that worms vermicompost contains 7.37 % nitrogen and 19.58% phosphorous as p2o5. microbial population of n2fixing bacteria and actinomycetes increases by the application of vermicompost. the amplified microbial activities improve the availability of soil phosphorous and nitrogen. vermicomposting is an aerobic, biological method and is proficient to convert eco-friendly hummus like organic substances (chanda et al. 2011). vermicompost stimulates to influence the microbial activity of soil, increases the availability of oxygen, maintains normal soil temperature, increases soil porosity and infiltration of water, improves nutrient content and increases growth, yield and quality of the plant (arora et al. 2011). rice hull and sawdust are also important agricultural amendments. growth and yield components of rice grown in saline soil were found to be increased significantly (p ≤ 0.05) by the application of rice hull, rice straw and sawdust alone and in combination (akter et al. 2018). the physico-chemical properties and nutrient status of post-harvest soils were also found to be influenced by the application of these amendments (akter and khan, 2019). composting is a low-cost natural way of recycling and stabilizing organic matter under thermophilic temperature that forms a pathogen-free substrate, beneficial to crops (gurtler et al. 2018; somerville et al. 2020). low-income farmers found it more advantageous to them. composting was found to be a promising practice that brought organic materials to a certain stage by narrowing down its c:n ratio where nutrients are easily accessible to plants (palaniveloo et al. 2020). partey et al. (2018) and dinesh et al. (2011), had consolidated that biomass needs to decompose for making n available to crops. thus, composting locally available organic amendments (oas) is essential for a healthy and sustainable agro-ecosystem in different climatic conditions. therefore, the objectives of the study were to evaluate the nutrient statuses of post-harvest soils and rice plants grown in aman season as influenced by the different rates of organic composts applied under field condition. materials and methods study site and experimental design in patuakhali a district of bangladesh, the field experiment was conducted in bilbilash of bauphal upazila (map i), which is located between 22°20ʹ00ʺn and 90°20ʹ00ʺe longitude within agro-ecological zone-13 named as ganges tidal floodplain. the climatic condition of this area is usually known as ‘tropical monsoon climate’. the area mainly enjoys three seasons such as rainy, dry and summer season. the experiment was carried out following completely randomized block design with the self-made organic composts, such as, rice hull compost (rhc), rice straw compost (rsc), sawdust compost (sdc) and vermicompost (v) corresponding to the rates of 0, 2, 4 and 8 t ha-1 of each organic compost at aman season during august to december, 2018. there were 13 plots having individual treatment (table i) in the experimental area, each unit plot size was 16 m2 (4m×4m) and replications were considered within the plot. selected properties of potential amendments used and initial soils at field site are presented in the tables ii and iii. transplantation following subsequent protocols basal doses of n, p2o5, and k2o from urea, tsp, and mop fertilizers were applied at the rates of 40, 30, and 15 kg ha-1, respectively considering soil amendments and initial contents of the nutrients. during field preparation, the tsp, mop, and half of the urea were applied in their entirety after being thoroughly mixed with the field soil. the remaining urea was top dressed in two splits, one at the beginning of the rice panicle and another at the active tillering stage. three seedlings per hill of the br 25 variety, which were thirty days old and in good health, were transplanted. row to row and hill to hill distances were each 20 and 22 cm, respectively. no irrigation was required for this study for the growth of rice in this season. intercultural operations such as, weeding, pesticide use, etc. were done as per requirement. sample collection and analyses plant samples were collected from each plot just after harvesting. soil samples were collected from 3 spots as replications of each plot of active root zone (0-15 cm) with the help of an auger. soil samples were then stored treatment wise in polythene bags with proper labeling. after sun drying and grounding the samples were then passed through 2 mm sieve and stored properly in air tight plastic pots for further analyses. the collected plant samples were sun dried and weighed. after sun drying a portion of the collected plant samples were oven dried at 65⁰c and then grinded and stored in air tight plastic pots for laboratory analyses. all the laboratory analyses were done following standard methods. statistical analyses pearson correlation and regression analyses between treatments and mineral nutrition of rice plants, analysis of variance (anova) and tukey’s range test at 5% (p≤ 0.05) level were done for the interpretation of the experimental results. results and discussion mineral nutrition of rice plants the total nitrogen, phosphorus, potassium, sulfur, calcium and magnesium contents at maturity stage of rice plants grown under field condition were significantly (p≤0.05) influenced by the application of variable indigenous organic amendments (rice hull compost, rice straw compost, sawdust compost and vermicompost) during aman season (table iv and fig.1). pearson correlation and regression analyses have been performed between the different treatments and mineral nutrition of rice plant tissues (table v). significance has been determined based on p values whether they were <0.05 or not. the total nitrogen (r = 0.78***), phosphorus (r = 0.77**), potassium (r = 0.75**), sulfur (r = 0.82***), calcium (r = 0.82***) and magnesium (r = 0.60*) contents of the tested rice plant (br 25) tissues were significantly correlated with the applied organic composts and these correlations confirmed that the different sources of organic materials positively influenced the nutrition of rice plant tissues which ultimately regulate the edible part (grain) of the rice crops. according to graham et al. (2012), people taking cereal based diets still suffering from hidden hunger of nutrients due to low level and low bioavailability of essential elements. the present results demonstrated that the nitrogen content in rice straw increased with the increased rate of the application of organic composts. the maximum nitrogen contents in the rice plant tissues were recorded at v8 treatment for the tested variety. among the applied composts, vermicompost (18.63 g kg-1n) ranked first followed by rice straw compost (17.40 g kg-1), sawdust compost (14.57g kg-1) and rice hull compost (13.33 g kg-1), regardless of their doses. phosphorus contents in rice plant tissues increased with the higher rates of the different composts. the highest (4.42 g kg-1) and lowest (1.10 g kg-1) contents of total phosphorus were recorded in the t12 (v8) and t0 (control) treatments. the rest of the above-mentioned nutrients were exerted the similar trends as those obtained by the p and n contents by the different organic composts. the nutrition of rice shoots was influenced by the direction of vermicompost > rice straw compost > sawdust compost > rice hull compost for the studied variety of rice grown under field condition. nutrient status of post-harvest soils rice production during t. aman season, the available n contents in the post-harvest soils increased significantly (p ≤ 0.05) by the application of vermicompost, rice hull compost, rice straw compost and sawdust compost (table vi and fig. 2). the maximum amount of available n (78.29 mg kg-1) was recorded in t3 (rhc8) treatment, where available nitrogen content increased 85.65% as compared to control plot. at the same dose (8 t ha-1), the sawdust compost treatment ranked second for the available nitrogen content (62.31 mg kg-1) at post-harvest soils followed by rsc8 treatment (60.76 mg kg-1). there were significant (p≤0.05) increase in available phosphorus and sulfur, exchangeable potassium, calcium and magnesium at post-harvest soils with the increased doses of the organic amendments under rice production (table vi). soils treated with vermicompost at the rate of 8 t ha-1 was found to have significantly more phosphorus (12.57 mg kg-1) as compared to control plot. the rice straw compost and sawdust compost each at 8 t ha-1 were showed almost similar trends in the increment of available phosphorus contents in post-harvest soils followed by rice hull compost. the other nutrients of post-harvest soils followed the similar trends as that of phosphorus, except for the exchangeable potassium, where rice straw compost at the highest rate (8 t ha-1) exhibited the best response (0.97 c molc kg -1) than those of the other treatments. the maximum amounts of available sulfur, exchangeable calcium and magnesium were obtained from the highest dose of vermicompost and the minimum amounts were attained by the control plot. the trend of increments of all these nutrients were more pronounced with the higher rates of the applied organic amendments indicate that all the applied organic composts are suitable sources for improving nutrient statuses of soils. pearson correlation and regression analyses also indicate the strong positive relationship between the treatments and nutrient statuses of post-harvest soils (table vii). the current findings are in consistent with those of xin et al. (2017). many steps have been made to improve soil fertility and productivity, according to them. increased organic input, such as organic manure, compost, and straw integration, are the most effective approaches. crop straw, a cheap and nutrient-dense material, offers a lot of potential for enhancing soil fertility (tan et al. 2017). crop straw, which is high in nutrients and organic elements, can be treated as a natural organic fertilizer and utilized as an alternative to chemical fertilizers, according to the studies of wang et al. (2017). as a result, straw integration appears to be a potential method for maintaining and restoring soil fertility, the burning issue of present day. because, mineral elements are required for the healthy growth and development of both plants and humans. the plant roots take up the mineral nutrients from soil and transported them to the edible parts for human consumption through various transporters. for human health, an ideal future crop should be rich in essential mineral elements but with less toxic elements in the edible parts. still, it is estimated that nearly 2 billion people are suffering from deficiency of nutrients because of low availability of mineral elements in soil and/or low accumulation/bioavailability of mineral elements in edible parts (graham et al. 2012). this so-called hidden hunger is an especially serious health problem for people subsisting on cereal-based diets because cereals such as rice usually contain a low level of mineral elements as well as low bioavailability (grebmer et al. 2014; nakandalage and seneweera, 2018). on the other hand, rapid urbanization and industrialization cause contamination by toxic elements in many soils used for crop production (zhao et al. 2010; clemens and ma, 2016), which threaten our health throughout the food chain. therefore, it is extremely important to boost essential nutrients (both density and bioavailability) and reduce toxic elements in edible parts of cereals for human health. conclusion the present research findings conclude that the locally made organic composts using indigenous organic materials had potential to improve soil fertility and provide nutrients for rice production. significant positive correlation between the treatments and mineral nutrients of rice plants confirmed the strong relationship of organic farming for sustainable agriculture. there were significant (p ≤ 0.05) increase in available phosphorus and sulfur, exchangeable potassium, calcium and magnesium at post-harvest soils with the increased doses of amendments under rice production. the nutrition of rice plants grown under field condition was influenced most by the vermicompost and followed the order of the treatments as rice straw compost > sawdust compost > rice hull compost for the studied variety of rice. these results resemble that the further researches are needed to find out the suitable doses and types of the amendments. however, the applied organic fertilizers were found to have responses on the nutritional statuses of rice shoot and post-harvest soils and these might be effective for the nutritional balance of the rice variety and ultimately will be helpful for country’s penniless people to combat their existing and future demand of quality rice. acknowledgement the study was carried out under a project of the climate change trust fund (cctf) titled ‘assessment of impacts of climate change on soil health and food security, and adaptation of climate-smart agriculture in most adversely affected areas of bangladesh’ through the moefcc, government of the peoples’ republic of bangladesh. the project was implemented in two phases (phase i: jan.’17 to dec.’18, code 410 duand phase ii: jan.’19 to dec.’22, code 573 du) within six years. we are also grateful to the project staff and relevant officers/staff of the swed-du, du, moe and moefcc of gob, who performed for the successful completion of the study. references ahmed s, alam mj, hossain a, islam ak, awan th, soufan w, qahtan aa, okla mk and sabagh si (2021), interactive effect of weeding regimes, rice cultivars, and seeding rates influence the rice-weed competition under dry direct-seeded condition, sustainability. 13: 317-321. doi: 10.3390/su13010317 akter s and khan hr (2019), influence of rice hull, rice straw, sawdust and moisture levels on selected properties of post harvested saline soils under variable conditions of rice cultivation, national university journal of science. 6(1): 61-74. akter s, khan hr, hossain ms, saha mk and farzana f (2018), response of rice grown in saline soil as influenced by the application of agricultural amendments and moisture regimes, j biodivers conserv bioresour manag. 4(2): 33-42. doi: https://doi.org/ 10.3329/jbcbm.v4i2.39845 ansari aa and ismail sa (2012), role of earthworms in vermtechnology, j agric technol. 8(2): 405-415. https://www.ijat-aatsea.com arora vk, singh cb, sidhu as and thind ss (2011), irrigation, tillage and mulching effects on soybean yield and water productivity in relation to soil texture, agric water manag. 98(4): 563-568. https://doi.org/10.1016/j.agwat .2010.10.004 bbs (2017), bangladesh bureau of statistics. the year book of agricultural statistics of bangladesh. stat. div. minis. planning, govt. peoples repub. bangladesh, dhaka. bbs (2020), summary crop statistics and crop indices (2019-2020). bangladesh bureau of statistics division, govt. of the people’s republic of bangladesh: dhaka, bangladesh. pp 35-37. chanda gc, bhunia g and chakraborty sk (2011), the effect of vermicompost and other fertilizers on cultivation of tomato plants, j hortic for. 3: 42-45. http://www.acade mic journals.org/jhf clemens s and ma jf (2016), toxic heavy metal and metalloid accumulation in crop plants and foods, annu rev plant biol. 67: 489-512. doi: 10.1146/annurev-arplant-043015-112301 dinesh r, suryanarayana ma, nair ak and chaudhuri sg (2011), leguminous cover crop effects on nitrogen mineralization rates and kinetics in soils, j agron crop sci. 187: 161-166. doi: 10.1046/j.1439-037x. 2001. 00512.x frg (2012), (fertilizer recommendation guide). bangladesh agricultural research council (barc), dhaka, bangladesh. graham rd, knez m and welch rm (2012), how much nutritional iron deficiency in humans globally is due to an underlying zinc deficiency, adv agron. 1-40. doi: 10.1016/b978-0-12-394276-0.00001-9 grebmer bkv, saltzman a, birol e, wiesmann d, prasai n, yins, yohannes y, menon p, thompson j and sonntag a (2014), 2014 global hunger index: the challenge of hidden hunger (washington, dc: international food policy research institute), pp 56. doi: http://dx.doi.org/10.2499/9780896299580 guerrero rd (2010), vermicompost production and its use for crop production in the philippines, international journal of global environmental issues. 10(3/4): 378-383. doi: 10.1504/ijgenvi.2010.037278 gurtler jb, doyle mp, erickson mc, jiang x, millner p and sharma m (2018), composting to inactivate food borne pathogens for crop soil application, a review j food prot.81: 1821-1837. doi: 10.4315/0362-028x.jfp-18-217 heitkamp f, raupp j and ludwig b (2011), soil organic matter pools and crop yields as affected by the rate of farmyard manure and use of biodynamic preparations in a sandy soil, organic agriculture. 11: 111-124. doi: 10.1007/s13165-011-0010-7 jahiruddin m and satter ma (2010), research priority in agriculture and development of vision document-2030 and beyond. land and soil resource management. bangladesh gricultural research council. dhaka. jeptoo a, aguyoh jn and saidi m (2013), improving carrot yield and quality through the use of bio-slurry manure, sustainable agricultural research. 2(1): 164-172. doi: 10.5539/sar.v2n1p164 nakandalage n and seneweera s (2018), micronutrients useefficiency of crop-plants under changing climate. in plant micronutrient use efficiency, m.a. hossain, t. kamiya, d.j. burritt, l.-s.p. tran and t. fujiwara, eds. (london: academic press), pp 209-224. palaniveloo k, amran ma, norhashim na, mohamad-fauzi n, peng-hui f, hui-wen l, kai-lin y, jiale l, chian-yee mg and jing-yi l (2020), food waste composting and microbial community structure profiling, processes. 8: 723. doi: org/10.3390/ pr8060723 partey st, thevathasan nv, zougmoré rb and preziosi rf (2018), improving maize production through nitrogen supply from tenrarely-used organic resources in ghana, agrofor syst. 92: 375-387. doi: 10.1007/ s10457-016-0035-8 pituello c, polese r, morari f and berti a (2016), outcomes from a long-term study on crop residue effects on plant yield and nitrogen use efficiency in contrasting soils, eur j agron. 77: 179-187. doi: 10.1016/j. eja.2015.11.027 somerville pd, farrell c, may pb and livesley sj (2020), biochar and compost equally improve urban soil physical and biological properties and tree growth, with no added benefit in combination, sci total environ. 706: 135-736. doi: 10.1016/j.scitotenv. 2019.135736 tan d, liu z, jiang l, luo j and li j (2017), long-term potash application and wheat straw return reduced soil potassium fixation and affected crop yields in north china, nutr cycl agroecosyst. doi: 10.1007/s10705 017-9843-0 wang w, sardans j, wang c, pan t, zeng c, lai d, bartrons m and peñuelas j (2017), straw application strategy to optimize nutrient release in a southeastern china rice cropland, agronomy. 7. doi: 10.3390/agronomy 7040084 xin x, qin s, zhang j, zhu a, yang w and zhang x (2017), yield, phosphorus use efficiency and balance response to substituting long-term chemical fertilizer use with organic manure in a wheat-maize system, field crop res. 208: 27-33. doi: 10.1016/j.fcr.2017.03.011 yang hs, xu mm, koide rt, liu q, dai yj, liu l and bian xm (2016), effects of ditch-buried straw return on water percolation, nitrogen leaching and crop yields in a rice-wheat rotation system, j sc. food agric. 96: 1141-1149. doi: 10.1002/jsfa.7196 zhang p, chen x, wei t, yang z, jia z, yang b, han q and ren x (2016), effects of straw incorporation on the soil nutrient contents, enzyme activities, and crop yield in a semiarid region of china, soil tillage res. 160: 65-72. doi: 10.1016/j.still.2016.02.006 zhang y, liu y, zhang g, guo x, sun z and li t (2018), the effects of rice straw and biochar applications on the microbial community in a soil with a history of continuous tomato planting history, agronomy. 8. doi: 10.3390/agronomy8050065 zhao fj, mcgrath sp and meharg aa (2010), arsenic as a food chain contaminant: mechanisms of plant uptake and metabolism and mitigation strategies, annu rev plant biol. 61: 535-559. doi: 10.1146/annurev-arplant-042809-112152 map i. location map of the study site #a = barishal division in bangladesh map; b = patuakhali district in barishal divisional map and c = bauphal upazila (study site) in patuakhali district map. table ii. nutrient compositions of different organic amendments used in the field experiment nutrient element (%) organic composts rhc rsc sdc v org. c 11.37 20.17 13.28 16.15 total n 0.57 1.07 1.02 1.05 total p 0.15 0.36 0.31 0.72 total k 0.14 0.43 0.23 0.79 total s 0.23 0.29 0.22 0.28 total ca 0.08 0.21 0.14 0.24 total mg 0.07 0.18 0.09 0.15 table i. description of the treatments used for the experiment treatment no. description no. description t0 = control no amendments were made t7 = sdc2 sawdust compost @ 2 t ha-1 t1 = rhc2 rice hull compost @ 2 t ha-1 t8 = sdc4 sawdust compost @ 4 t ha-1 t2 = rhc4 rice hull compost @ 4 t ha-1 t9 = sdc8 sawdust compost @ 8 t ha-1 t3 = rhc8 rice hull compost @ 8 t ha-1 t10 = v2 vermicompost @ 2 t ha-1 t4 = rsc2 rice straw compost @ 2 t ha-1 t11 = v4 vermicompost @ 4 t ha-1 t5 = rsc4 rice straw compost @ 4 t ha-1 t12 = v8 vermicompost @ 8 t ha-1 t6 = rsc8 rice straw compost @ 8 t ha-1 mineral nutrition of rice and post-harvest soils influenced by self-made organic composts 58(2) 2023102 however, until now, the use of straw incorporation to increase crop yield is still a matter of argument since studies in different climates and soil types have led to inconclusive results (pituello et al. 2016). it has been reported that straw incorporation has significant valuable effects on crop yields and soil properties. for instance, straw incorporation can increase crop yields (yang et al. 2016), soil organic matter and other soil nutrients (zhang et al. 2018). straw return can also improve soil physical properties, such as by increasing hydraulic conductivity, decreasing bulk density, and enhancing aggregate formation (yang et al. 2016). vermicompost is a nourishing organic fertilizer having high amount of humus, nitrogen 2–3%, phosphorous 1.55–2.25%, potassium 1.85–2.25%, micronutrients, more beneficial for soil microbes like ‘nitrogen fixing bacteria’ and mycorrhizal fungi. vermicompost has been scientifically proved as miracle plant growth enhancer (guerrero, 2010). ansari and ismail (2012) reported that worms vermicompost contains 7.37 % nitrogen and 19.58% phosphorous as p2o5. microbial population of n2fixing bacteria and actinomycetes increases by the application of vermicompost. the amplified microbial activities improve the availability of soil phosphorous and nitrogen. vermicomposting is an aerobic, biological method and is proficient to convert eco-friendly hummus like organic substances (chanda et al. 2011). vermicompost stimulates to influence the microbial activity of soil, increases the availability of oxygen, maintains normal soil temperature, increases soil porosity and infiltration of water, improves nutrient content and increases growth, yield and quality of the plant (arora et al. 2011). rice hull and sawdust are also important agricultural amendments. growth and yield components of rice grown in saline soil were found to be increased significantly (p ≤ 0.05) by the application of rice hull, rice straw and sawdust alone and in combination (akter et al. 2018). the physico-chemical properties and nutrient status of post-harvest soils were also found to be influenced by the application of these amendments (akter and khan, 2019). composting is a low-cost natural way of recycling and stabilizing organic matter under thermophilic temperature that forms a pathogen-free substrate, beneficial to crops (gurtler et al. 2018; somerville et al. 2020). low-income farmers found it more advantageous to them. composting was found to be a promising practice that brought organic materials to a certain stage by narrowing down its c:n ratio where nutrients are easily accessible to plants (palaniveloo et al. 2020). partey et al. (2018) and dinesh et al. (2011), had consolidated that biomass needs to decompose for making n available to crops. thus, composting locally available organic amendments (oas) is essential for a healthy and sustainable agro-ecosystem in different climatic conditions. therefore, the objectives of the study were to evaluate the nutrient statuses of post-harvest soils and rice plants grown in aman season as influenced by the different rates of organic composts applied under field condition. materials and methods study site and experimental design in patuakhali a district of bangladesh, the field experiment was conducted in bilbilash of bauphal upazila (map i), which is located between 22°20ʹ00ʺn and 90°20ʹ00ʺe longitude within agro-ecological zone-13 named as ganges tidal floodplain. the climatic condition of this area is usually known as ‘tropical monsoon climate’. the area mainly enjoys three seasons such as rainy, dry and summer season. the experiment was carried out following completely randomized block design with the self-made organic composts, such as, rice hull compost (rhc), rice straw compost (rsc), sawdust compost (sdc) and vermicompost (v) corresponding to the rates of 0, 2, 4 and 8 t ha-1 of each organic compost at aman season during august to december, 2018. there were 13 plots having individual treatment (table i) in the experimental area, each unit plot size was 16 m2 (4m×4m) and replications were considered within the plot. selected properties of potential amendments used and initial soils at field site are presented in the tables ii and iii. transplantation following subsequent protocols basal doses of n, p2o5, and k2o from urea, tsp, and mop fertilizers were applied at the rates of 40, 30, and 15 kg ha-1, respectively considering soil amendments and initial contents of the nutrients. during field preparation, the tsp, mop, and half of the urea were applied in their entirety after being thoroughly mixed with the field soil. the remaining urea was top dressed in two splits, one at the beginning of the rice panicle and another at the active tillering stage. three seedlings per hill of the br 25 variety, which were thirty days old and in good health, were transplanted. row to row and hill to hill distances were each 20 and 22 cm, respectively. no irrigation was required for this study for the growth of rice in this season. intercultural operations such as, weeding, pesticide use, etc. were done as per requirement. sample collection and analyses plant samples were collected from each plot just after harvesting. soil samples were collected from 3 spots as replications of each plot of active root zone (0-15 cm) with the help of an auger. soil samples were then stored treatment wise in polythene bags with proper labeling. after sun drying and grounding the samples were then passed through 2 mm sieve and stored properly in air tight plastic pots for further analyses. the collected plant samples were sun dried and weighed. after sun drying a portion of the collected plant samples were oven dried at 65⁰c and then grinded and stored in air tight plastic pots for laboratory analyses. all the laboratory analyses were done following standard methods. statistical analyses pearson correlation and regression analyses between treatments and mineral nutrition of rice plants, analysis of variance (anova) and tukey’s range test at 5% (p≤ 0.05) level were done for the interpretation of the experimental results. results and discussion mineral nutrition of rice plants the total nitrogen, phosphorus, potassium, sulfur, calcium and magnesium contents at maturity stage of rice plants grown under field condition were significantly (p≤0.05) influenced by the application of variable indigenous organic amendments (rice hull compost, rice straw compost, sawdust compost and vermicompost) during aman season (table iv and fig.1). pearson correlation and regression analyses have been performed between the different treatments and mineral nutrition of rice plant tissues (table v). significance has been determined based on p values whether they were <0.05 or not. the total nitrogen (r = 0.78***), phosphorus (r = 0.77**), potassium (r = 0.75**), sulfur (r = 0.82***), calcium (r = 0.82***) and magnesium (r = 0.60*) contents of the tested rice plant (br 25) tissues were significantly correlated with the applied organic composts and these correlations confirmed that the different sources of organic materials positively influenced the nutrition of rice plant tissues which ultimately regulate the edible part (grain) of the rice crops. according to graham et al. (2012), people taking cereal based diets still suffering from hidden hunger of nutrients due to low level and low bioavailability of essential elements. the present results demonstrated that the nitrogen content in rice straw increased with the increased rate of the application of organic composts. the maximum nitrogen contents in the rice plant tissues were recorded at v8 treatment for the tested variety. among the applied composts, vermicompost (18.63 g kg-1n) ranked first followed by rice straw compost (17.40 g kg-1), sawdust compost (14.57g kg-1) and rice hull compost (13.33 g kg-1), regardless of their doses. phosphorus contents in rice plant tissues increased with the higher rates of the different composts. the highest (4.42 g kg-1) and lowest (1.10 g kg-1) contents of total phosphorus were recorded in the t12 (v8) and t0 (control) treatments. the rest of the above-mentioned nutrients were exerted the similar trends as those obtained by the p and n contents by the different organic composts. the nutrition of rice shoots was influenced by the direction of vermicompost > rice straw compost > sawdust compost > rice hull compost for the studied variety of rice grown under field condition. nutrient status of post-harvest soils rice production during t. aman season, the available n contents in the post-harvest soils increased significantly (p ≤ 0.05) by the application of vermicompost, rice hull compost, rice straw compost and sawdust compost (table vi and fig. 2). the maximum amount of available n (78.29 mg kg-1) was recorded in t3 (rhc8) treatment, where available nitrogen content increased 85.65% as compared to control plot. at the same dose (8 t ha-1), the sawdust compost treatment ranked second for the available nitrogen content (62.31 mg kg-1) at post-harvest soils followed by rsc8 treatment (60.76 mg kg-1). there were significant (p≤0.05) increase in available phosphorus and sulfur, exchangeable potassium, calcium and magnesium at post-harvest soils with the increased doses of the organic amendments under rice production (table vi). soils treated with vermicompost at the rate of 8 t ha-1 was found to have significantly more phosphorus (12.57 mg kg-1) as compared to control plot. the rice straw compost and sawdust compost each at 8 t ha-1 were showed almost similar trends in the increment of available phosphorus contents in post-harvest soils followed by rice hull compost. the other nutrients of post-harvest soils followed the similar trends as that of phosphorus, except for the exchangeable potassium, where rice straw compost at the highest rate (8 t ha-1) exhibited the best response (0.97 c molc kg -1) than those of the other treatments. the maximum amounts of available sulfur, exchangeable calcium and magnesium were obtained from the highest dose of vermicompost and the minimum amounts were attained by the control plot. the trend of increments of all these nutrients were more pronounced with the higher rates of the applied organic amendments indicate that all the applied organic composts are suitable sources for improving nutrient statuses of soils. pearson correlation and regression analyses also indicate the strong positive relationship between the treatments and nutrient statuses of post-harvest soils (table vii). the current findings are in consistent with those of xin et al. (2017). many steps have been made to improve soil fertility and productivity, according to them. increased organic input, such as organic manure, compost, and straw integration, are the most effective approaches. crop straw, a cheap and nutrient-dense material, offers a lot of potential for enhancing soil fertility (tan et al. 2017). crop straw, which is high in nutrients and organic elements, can be treated as a natural organic fertilizer and utilized as an alternative to chemical fertilizers, according to the studies of wang et al. (2017). as a result, straw integration appears to be a potential method for maintaining and restoring soil fertility, the burning issue of present day. because, mineral elements are required for the healthy growth and development of both plants and humans. the plant roots take up the mineral nutrients from soil and transported them to the edible parts for human consumption through various transporters. for human health, an ideal future crop should be rich in essential mineral elements but with less toxic elements in the edible parts. still, it is estimated that nearly 2 billion people are suffering from deficiency of nutrients because of low availability of mineral elements in soil and/or low accumulation/bioavailability of mineral elements in edible parts (graham et al. 2012). this so-called hidden hunger is an especially serious health problem for people subsisting on cereal-based diets because cereals such as rice usually contain a low level of mineral elements as well as low bioavailability (grebmer et al. 2014; nakandalage and seneweera, 2018). on the other hand, rapid urbanization and industrialization cause contamination by toxic elements in many soils used for crop production (zhao et al. 2010; clemens and ma, 2016), which threaten our health throughout the food chain. therefore, it is extremely important to boost essential nutrients (both density and bioavailability) and reduce toxic elements in edible parts of cereals for human health. conclusion the present research findings conclude that the locally made organic composts using indigenous organic materials had potential to improve soil fertility and provide nutrients for rice production. significant positive correlation between the treatments and mineral nutrients of rice plants confirmed the strong relationship of organic farming for sustainable agriculture. there were significant (p ≤ 0.05) increase in available phosphorus and sulfur, exchangeable potassium, calcium and magnesium at post-harvest soils with the increased doses of amendments under rice production. the nutrition of rice plants grown under field condition was influenced most by the vermicompost and followed the order of the treatments as rice straw compost > sawdust compost > rice hull compost for the studied variety of rice. these results resemble that the further researches are needed to find out the suitable doses and types of the amendments. however, the applied organic fertilizers were found to have responses on the nutritional statuses of rice shoot and post-harvest soils and these might be effective for the nutritional balance of the rice variety and ultimately will be helpful for country’s penniless people to combat their existing and future demand of quality rice. acknowledgement the study was carried out under a project of the climate change trust fund (cctf) titled ‘assessment of impacts of climate change on soil health and food security, and adaptation of climate-smart agriculture in most adversely affected areas of bangladesh’ through the moefcc, government of the peoples’ republic of bangladesh. the project was implemented in two phases (phase i: jan.’17 to dec.’18, code 410 duand phase ii: jan.’19 to dec.’22, code 573 du) within six years. we are also grateful to the project staff and relevant officers/staff of the swed-du, du, moe and moefcc of gob, who performed for the successful completion of the study. references ahmed s, alam mj, hossain a, islam ak, awan th, soufan w, qahtan aa, okla mk and sabagh si (2021), interactive effect of weeding regimes, rice cultivars, and seeding rates influence the rice-weed competition under dry direct-seeded condition, sustainability. 13: 317-321. doi: 10.3390/su13010317 akter s and khan hr (2019), influence of rice hull, rice straw, sawdust and moisture levels on selected properties of post harvested saline soils under variable conditions of rice cultivation, national university journal of science. 6(1): 61-74. akter s, khan hr, hossain ms, saha mk and farzana f (2018), response of rice grown in saline soil as influenced by the application of agricultural amendments and moisture regimes, j biodivers conserv bioresour manag. 4(2): 33-42. doi: https://doi.org/ 10.3329/jbcbm.v4i2.39845 ansari aa and ismail sa (2012), role of earthworms in vermtechnology, j agric technol. 8(2): 405-415. https://www.ijat-aatsea.com arora vk, singh cb, sidhu as and thind ss (2011), irrigation, tillage and mulching effects on soybean yield and water productivity in relation to soil texture, agric water manag. 98(4): 563-568. https://doi.org/10.1016/j.agwat .2010.10.004 bbs (2017), bangladesh bureau of statistics. the year book of agricultural statistics of bangladesh. stat. div. minis. planning, govt. peoples repub. bangladesh, dhaka. bbs (2020), summary crop statistics and crop indices (2019-2020). bangladesh bureau of statistics division, govt. of the people’s republic of bangladesh: dhaka, bangladesh. pp 35-37. chanda gc, bhunia g and chakraborty sk (2011), the effect of vermicompost and other fertilizers on cultivation of tomato plants, j hortic for. 3: 42-45. http://www.acade mic journals.org/jhf clemens s and ma jf (2016), toxic heavy metal and metalloid accumulation in crop plants and foods, annu rev plant biol. 67: 489-512. doi: 10.1146/annurev-arplant-043015-112301 dinesh r, suryanarayana ma, nair ak and chaudhuri sg (2011), leguminous cover crop effects on nitrogen mineralization rates and kinetics in soils, j agron crop sci. 187: 161-166. doi: 10.1046/j.1439-037x. 2001. 00512.x frg (2012), (fertilizer recommendation guide). bangladesh agricultural research council (barc), dhaka, bangladesh. graham rd, knez m and welch rm (2012), how much nutritional iron deficiency in humans globally is due to an underlying zinc deficiency, adv agron. 1-40. doi: 10.1016/b978-0-12-394276-0.00001-9 grebmer bkv, saltzman a, birol e, wiesmann d, prasai n, yins, yohannes y, menon p, thompson j and sonntag a (2014), 2014 global hunger index: the challenge of hidden hunger (washington, dc: international food policy research institute), pp 56. doi: http://dx.doi.org/10.2499/9780896299580 guerrero rd (2010), vermicompost production and its use for crop production in the philippines, international journal of global environmental issues. 10(3/4): 378-383. doi: 10.1504/ijgenvi.2010.037278 gurtler jb, doyle mp, erickson mc, jiang x, millner p and sharma m (2018), composting to inactivate food borne pathogens for crop soil application, a review j food prot.81: 1821-1837. doi: 10.4315/0362-028x.jfp-18-217 heitkamp f, raupp j and ludwig b (2011), soil organic matter pools and crop yields as affected by the rate of farmyard manure and use of biodynamic preparations in a sandy soil, organic agriculture. 11: 111-124. doi: 10.1007/s13165-011-0010-7 jahiruddin m and satter ma (2010), research priority in agriculture and development of vision document-2030 and beyond. land and soil resource management. bangladesh gricultural research council. dhaka. jeptoo a, aguyoh jn and saidi m (2013), improving carrot yield and quality through the use of bio-slurry manure, sustainable agricultural research. 2(1): 164-172. doi: 10.5539/sar.v2n1p164 nakandalage n and seneweera s (2018), micronutrients useefficiency of crop-plants under changing climate. in plant micronutrient use efficiency, m.a. hossain, t. kamiya, d.j. burritt, l.-s.p. tran and t. fujiwara, eds. (london: academic press), pp 209-224. palaniveloo k, amran ma, norhashim na, mohamad-fauzi n, peng-hui f, hui-wen l, kai-lin y, jiale l, chian-yee mg and jing-yi l (2020), food waste composting and microbial community structure profiling, processes. 8: 723. doi: org/10.3390/ pr8060723 partey st, thevathasan nv, zougmoré rb and preziosi rf (2018), improving maize production through nitrogen supply from tenrarely-used organic resources in ghana, agrofor syst. 92: 375-387. doi: 10.1007/ s10457-016-0035-8 pituello c, polese r, morari f and berti a (2016), outcomes from a long-term study on crop residue effects on plant yield and nitrogen use efficiency in contrasting soils, eur j agron. 77: 179-187. doi: 10.1016/j. eja.2015.11.027 somerville pd, farrell c, may pb and livesley sj (2020), biochar and compost equally improve urban soil physical and biological properties and tree growth, with no added benefit in combination, sci total environ. 706: 135-736. doi: 10.1016/j.scitotenv. 2019.135736 tan d, liu z, jiang l, luo j and li j (2017), long-term potash application and wheat straw return reduced soil potassium fixation and affected crop yields in north china, nutr cycl agroecosyst. doi: 10.1007/s10705 017-9843-0 wang w, sardans j, wang c, pan t, zeng c, lai d, bartrons m and peñuelas j (2017), straw application strategy to optimize nutrient release in a southeastern china rice cropland, agronomy. 7. doi: 10.3390/agronomy 7040084 xin x, qin s, zhang j, zhu a, yang w and zhang x (2017), yield, phosphorus use efficiency and balance response to substituting long-term chemical fertilizer use with organic manure in a wheat-maize system, field crop res. 208: 27-33. doi: 10.1016/j.fcr.2017.03.011 yang hs, xu mm, koide rt, liu q, dai yj, liu l and bian xm (2016), effects of ditch-buried straw return on water percolation, nitrogen leaching and crop yields in a rice-wheat rotation system, j sc. food agric. 96: 1141-1149. doi: 10.1002/jsfa.7196 zhang p, chen x, wei t, yang z, jia z, yang b, han q and ren x (2016), effects of straw incorporation on the soil nutrient contents, enzyme activities, and crop yield in a semiarid region of china, soil tillage res. 160: 65-72. doi: 10.1016/j.still.2016.02.006 zhang y, liu y, zhang g, guo x, sun z and li t (2018), the effects of rice straw and biochar applications on the microbial community in a soil with a history of continuous tomato planting history, agronomy. 8. doi: 10.3390/agronomy8050065 zhao fj, mcgrath sp and meharg aa (2010), arsenic as a food chain contaminant: mechanisms of plant uptake and metabolism and mitigation strategies, annu rev plant biol. 61: 535-559. doi: 10.1146/annurev-arplant-042809-112152 table iii. selected properties of initial soil (on oven dry basis: 0-15 cm) used in the field experiment properties values a. physical particle density (g cm-3) 2.53 bulk density (g cm-3) 1.25 porosity (%) 50.21 moisture content (%) 3.15 particle size distribution sand (%) 5.67 silt (%) 57.47 clay (%) 36.86 textural class b. chemical ph 4.57 ec (saturation extract, 1:5; ds m-1) 0.21 organic matter (%) total nitrogen (g kg-1) 1.56 0.54 available nitrogen (mg kg-1) 63.07 available phosphorus (mg kg-1) 7.21 available sulfur (mg kg-1) 19.18 exchangeable cations (c molc kg -1): potassium (k+) 0.21 calcium (ca2+) 5.41 magnesium (mg2+) 3.88 cation exchange capacity (c molckg -1) 12.87 akter, khan and saha 103 however, until now, the use of straw incorporation to increase crop yield is still a matter of argument since studies in different climates and soil types have led to inconclusive results (pituello et al. 2016). it has been reported that straw incorporation has significant valuable effects on crop yields and soil properties. for instance, straw incorporation can increase crop yields (yang et al. 2016), soil organic matter and other soil nutrients (zhang et al. 2018). straw return can also improve soil physical properties, such as by increasing hydraulic conductivity, decreasing bulk density, and enhancing aggregate formation (yang et al. 2016). vermicompost is a nourishing organic fertilizer having high amount of humus, nitrogen 2–3%, phosphorous 1.55–2.25%, potassium 1.85–2.25%, micronutrients, more beneficial for soil microbes like ‘nitrogen fixing bacteria’ and mycorrhizal fungi. vermicompost has been scientifically proved as miracle plant growth enhancer (guerrero, 2010). ansari and ismail (2012) reported that worms vermicompost contains 7.37 % nitrogen and 19.58% phosphorous as p2o5. microbial population of n2fixing bacteria and actinomycetes increases by the application of vermicompost. the amplified microbial activities improve the availability of soil phosphorous and nitrogen. vermicomposting is an aerobic, biological method and is proficient to convert eco-friendly hummus like organic substances (chanda et al. 2011). vermicompost stimulates to influence the microbial activity of soil, increases the availability of oxygen, maintains normal soil temperature, increases soil porosity and infiltration of water, improves nutrient content and increases growth, yield and quality of the plant (arora et al. 2011). rice hull and sawdust are also important agricultural amendments. growth and yield components of rice grown in saline soil were found to be increased significantly (p ≤ 0.05) by the application of rice hull, rice straw and sawdust alone and in combination (akter et al. 2018). the physico-chemical properties and nutrient status of post-harvest soils were also found to be influenced by the application of these amendments (akter and khan, 2019). composting is a low-cost natural way of recycling and stabilizing organic matter under thermophilic temperature that forms a pathogen-free substrate, beneficial to crops (gurtler et al. 2018; somerville et al. 2020). low-income farmers found it more advantageous to them. composting was found to be a promising practice that brought organic materials to a certain stage by narrowing down its c:n ratio where nutrients are easily accessible to plants (palaniveloo et al. 2020). partey et al. (2018) and dinesh et al. (2011), had consolidated that biomass needs to decompose for making n available to crops. thus, composting locally available organic amendments (oas) is essential for a healthy and sustainable agro-ecosystem in different climatic conditions. therefore, the objectives of the study were to evaluate the nutrient statuses of post-harvest soils and rice plants grown in aman season as influenced by the different rates of organic composts applied under field condition. materials and methods study site and experimental design in patuakhali a district of bangladesh, the field experiment was conducted in bilbilash of bauphal upazila (map i), which is located between 22°20ʹ00ʺn and 90°20ʹ00ʺe longitude within agro-ecological zone-13 named as ganges tidal floodplain. the climatic condition of this area is usually known as ‘tropical monsoon climate’. the area mainly enjoys three seasons such as rainy, dry and summer season. the experiment was carried out following completely randomized block design with the self-made organic composts, such as, rice hull compost (rhc), rice straw compost (rsc), sawdust compost (sdc) and vermicompost (v) corresponding to the rates of 0, 2, 4 and 8 t ha-1 of each organic compost at aman season during august to december, 2018. there were 13 plots having individual treatment (table i) in the experimental area, each unit plot size was 16 m2 (4m×4m) and replications were considered within the plot. selected properties of potential amendments used and initial soils at field site are presented in the tables ii and iii. transplantation following subsequent protocols basal doses of n, p2o5, and k2o from urea, tsp, and mop fertilizers were applied at the rates of 40, 30, and 15 kg ha-1, respectively considering soil amendments and initial contents of the nutrients. during field preparation, the tsp, mop, and half of the urea were applied in their entirety after being thoroughly mixed with the field soil. the remaining urea was top dressed in two splits, one at the beginning of the rice panicle and another at the active tillering stage. three seedlings per hill of the br 25 variety, which were thirty days old and in good health, were transplanted. row to row and hill to hill distances were each 20 and 22 cm, respectively. no irrigation was required for this study for the growth of rice in this season. intercultural operations such as, weeding, pesticide use, etc. were done as per requirement. sample collection and analyses plant samples were collected from each plot just after harvesting. soil samples were collected from 3 spots as replications of each plot of active root zone (0-15 cm) with the help of an auger. soil samples were then stored treatment wise in polythene bags with proper labeling. after sun drying and grounding the samples were then passed through 2 mm sieve and stored properly in air tight plastic pots for further analyses. the collected plant samples were sun dried and weighed. after sun drying a portion of the collected plant samples were oven dried at 65⁰c and then grinded and stored in air tight plastic pots for laboratory analyses. all the laboratory analyses were done following standard methods. statistical analyses pearson correlation and regression analyses between treatments and mineral nutrition of rice plants, analysis of variance (anova) and tukey’s range test at 5% (p≤ 0.05) level were done for the interpretation of the experimental results. results and discussion mineral nutrition of rice plants the total nitrogen, phosphorus, potassium, sulfur, calcium and magnesium contents at maturity stage of rice plants grown under field condition were significantly (p≤0.05) influenced by the application of variable indigenous organic amendments (rice hull compost, rice straw compost, sawdust compost and vermicompost) during aman season (table iv and fig.1). pearson correlation and regression analyses have been performed between the different treatments and mineral nutrition of rice plant tissues (table v). significance has been determined based on p values whether they were <0.05 or not. the total nitrogen (r = 0.78***), phosphorus (r = 0.77**), potassium (r = 0.75**), sulfur (r = 0.82***), calcium (r = 0.82***) and magnesium (r = 0.60*) contents of the tested rice plant (br 25) tissues were significantly correlated with the applied organic composts and these correlations confirmed that the different sources of organic materials positively influenced the nutrition of rice plant tissues which ultimately regulate the edible part (grain) of the rice crops. according to graham et al. (2012), people taking cereal based diets still suffering from hidden hunger of nutrients due to low level and low bioavailability of essential elements. the present results demonstrated that the nitrogen content in rice straw increased with the increased rate of the application of organic composts. the maximum nitrogen contents in the rice plant tissues were recorded at v8 treatment for the tested variety. among the applied composts, vermicompost (18.63 g kg-1n) ranked first followed by rice straw compost (17.40 g kg-1), sawdust compost (14.57g kg-1) and rice hull compost (13.33 g kg-1), regardless of their doses. phosphorus contents in rice plant tissues increased with the higher rates of the different composts. the highest (4.42 g kg-1) and lowest (1.10 g kg-1) contents of total phosphorus were recorded in the t12 (v8) and t0 (control) treatments. the rest of the above-mentioned nutrients were exerted the similar trends as those obtained by the p and n contents by the different organic composts. the nutrition of rice shoots was influenced by the direction of vermicompost > rice straw compost > sawdust compost > rice hull compost for the studied variety of rice grown under field condition. nutrient status of post-harvest soils rice production during t. aman season, the available n contents in the post-harvest soils increased significantly (p ≤ 0.05) by the application of vermicompost, rice hull compost, rice straw compost and sawdust compost (table vi and fig. 2). the maximum amount of available n (78.29 mg kg-1) was recorded in t3 (rhc8) treatment, where available nitrogen content increased 85.65% as compared to control plot. at the same dose (8 t ha-1), the sawdust compost treatment ranked second for the available nitrogen content (62.31 mg kg-1) at post-harvest soils followed by rsc8 treatment (60.76 mg kg-1). there were significant (p≤0.05) increase in available phosphorus and sulfur, exchangeable potassium, calcium and magnesium at post-harvest soils with the increased doses of the organic amendments under rice production (table vi). soils treated with vermicompost at the rate of 8 t ha-1 was found to have significantly more phosphorus (12.57 mg kg-1) as compared to control plot. the rice straw compost and sawdust compost each at 8 t ha-1 were showed almost similar trends in the increment of available phosphorus contents in post-harvest soils followed by rice hull compost. the other nutrients of post-harvest soils followed the similar trends as that of phosphorus, except for the exchangeable potassium, where rice straw compost at the highest rate (8 t ha-1) exhibited the best response (0.97 c molc kg -1) than those of the other treatments. the maximum amounts of available sulfur, exchangeable calcium and magnesium were obtained from the highest dose of vermicompost and the minimum amounts were attained by the control plot. the trend of increments of all these nutrients were more pronounced with the higher rates of the applied organic amendments indicate that all the applied organic composts are suitable sources for improving nutrient statuses of soils. pearson correlation and regression analyses also indicate the strong positive relationship between the treatments and nutrient statuses of post-harvest soils (table vii). the current findings are in consistent with those of xin et al. (2017). many steps have been made to improve soil fertility and productivity, according to them. increased organic input, such as organic manure, compost, and straw integration, are the most effective approaches. crop straw, a cheap and nutrient-dense material, offers a lot of potential for enhancing soil fertility (tan et al. 2017). crop straw, which is high in nutrients and organic elements, can be treated as a natural organic fertilizer and utilized as an alternative to chemical fertilizers, according to the studies of wang et al. (2017). as a result, straw integration appears to be a potential method for maintaining and restoring soil fertility, the burning issue of present day. because, mineral elements are required for the healthy growth and development of both plants and humans. the plant roots take up the mineral nutrients from soil and transported them to the edible parts for human consumption through various transporters. for human health, an ideal future crop should be rich in essential mineral elements but with less toxic elements in the edible parts. still, it is estimated that nearly 2 billion people are suffering from deficiency of nutrients because of low availability of mineral elements in soil and/or low accumulation/bioavailability of mineral elements in edible parts (graham et al. 2012). this so-called hidden hunger is an especially serious health problem for people subsisting on cereal-based diets because cereals such as rice usually contain a low level of mineral elements as well as low bioavailability (grebmer et al. 2014; nakandalage and seneweera, 2018). on the other hand, rapid urbanization and industrialization cause contamination by toxic elements in many soils used for crop production (zhao et al. 2010; clemens and ma, 2016), which threaten our health throughout the food chain. therefore, it is extremely important to boost essential nutrients (both density and bioavailability) and reduce toxic elements in edible parts of cereals for human health. conclusion the present research findings conclude that the locally made organic composts using indigenous organic materials had potential to improve soil fertility and provide nutrients for rice production. significant positive correlation between the treatments and mineral nutrients of rice plants confirmed the strong relationship of organic farming for sustainable agriculture. there were significant (p ≤ 0.05) increase in available phosphorus and sulfur, exchangeable potassium, calcium and magnesium at post-harvest soils with the increased doses of amendments under rice production. the nutrition of rice plants grown under field condition was influenced most by the vermicompost and followed the order of the treatments as rice straw compost > sawdust compost > rice hull compost for the studied variety of rice. these results resemble that the further researches are needed to find out the suitable doses and types of the amendments. however, the applied organic fertilizers were found to have responses on the nutritional statuses of rice shoot and post-harvest soils and these might be effective for the nutritional balance of the rice variety and ultimately will be helpful for country’s penniless people to combat their existing and future demand of quality rice. acknowledgement the study was carried out under a project of the climate change trust fund (cctf) titled ‘assessment of impacts of climate change on soil health and food security, and adaptation of climate-smart agriculture in most adversely affected areas of bangladesh’ through the moefcc, government of the peoples’ republic of bangladesh. the project was implemented in two phases (phase i: jan.’17 to dec.’18, code 410 duand phase ii: jan.’19 to dec.’22, code 573 du) within six years. we are also grateful to the project staff and relevant officers/staff of the swed-du, du, moe and moefcc of gob, who performed for the successful completion of the study. references ahmed s, alam mj, hossain a, islam ak, awan th, soufan w, qahtan aa, okla mk and sabagh si (2021), interactive effect of weeding regimes, rice cultivars, and seeding rates influence the rice-weed competition under dry direct-seeded condition, sustainability. 13: 317-321. doi: 10.3390/su13010317 akter s and khan hr (2019), influence of rice hull, rice straw, sawdust and moisture levels on selected properties of post harvested saline soils under variable conditions of rice cultivation, national university journal of science. 6(1): 61-74. akter s, khan hr, hossain ms, saha mk and farzana f (2018), response of rice grown in saline soil as influenced by the application of agricultural amendments and moisture regimes, j biodivers conserv bioresour manag. 4(2): 33-42. doi: https://doi.org/ 10.3329/jbcbm.v4i2.39845 ansari aa and ismail sa (2012), role of earthworms in vermtechnology, j agric technol. 8(2): 405-415. https://www.ijat-aatsea.com arora vk, singh cb, sidhu as and thind ss (2011), irrigation, tillage and mulching effects on soybean yield and water productivity in relation to soil texture, agric water manag. 98(4): 563-568. https://doi.org/10.1016/j.agwat .2010.10.004 bbs (2017), bangladesh bureau of statistics. the year book of agricultural statistics of bangladesh. stat. div. minis. planning, govt. peoples repub. bangladesh, dhaka. bbs (2020), summary crop statistics and crop indices (2019-2020). bangladesh bureau of statistics division, govt. of the people’s republic of bangladesh: dhaka, bangladesh. pp 35-37. chanda gc, bhunia g and chakraborty sk (2011), the effect of vermicompost and other fertilizers on cultivation of tomato plants, j hortic for. 3: 42-45. http://www.acade mic journals.org/jhf clemens s and ma jf (2016), toxic heavy metal and metalloid accumulation in crop plants and foods, annu rev plant biol. 67: 489-512. doi: 10.1146/annurev-arplant-043015-112301 dinesh r, suryanarayana ma, nair ak and chaudhuri sg (2011), leguminous cover crop effects on nitrogen mineralization rates and kinetics in soils, j agron crop sci. 187: 161-166. doi: 10.1046/j.1439-037x. 2001. 00512.x frg (2012), (fertilizer recommendation guide). bangladesh agricultural research council (barc), dhaka, bangladesh. graham rd, knez m and welch rm (2012), how much nutritional iron deficiency in humans globally is due to an underlying zinc deficiency, adv agron. 1-40. doi: 10.1016/b978-0-12-394276-0.00001-9 grebmer bkv, saltzman a, birol e, wiesmann d, prasai n, yins, yohannes y, menon p, thompson j and sonntag a (2014), 2014 global hunger index: the challenge of hidden hunger (washington, dc: international food policy research institute), pp 56. doi: http://dx.doi.org/10.2499/9780896299580 guerrero rd (2010), vermicompost production and its use for crop production in the philippines, international journal of global environmental issues. 10(3/4): 378-383. doi: 10.1504/ijgenvi.2010.037278 gurtler jb, doyle mp, erickson mc, jiang x, millner p and sharma m (2018), composting to inactivate food borne pathogens for crop soil application, a review j food prot.81: 1821-1837. doi: 10.4315/0362-028x.jfp-18-217 heitkamp f, raupp j and ludwig b (2011), soil organic matter pools and crop yields as affected by the rate of farmyard manure and use of biodynamic preparations in a sandy soil, organic agriculture. 11: 111-124. doi: 10.1007/s13165-011-0010-7 jahiruddin m and satter ma (2010), research priority in agriculture and development of vision document-2030 and beyond. land and soil resource management. bangladesh gricultural research council. dhaka. jeptoo a, aguyoh jn and saidi m (2013), improving carrot yield and quality through the use of bio-slurry manure, sustainable agricultural research. 2(1): 164-172. doi: 10.5539/sar.v2n1p164 nakandalage n and seneweera s (2018), micronutrients useefficiency of crop-plants under changing climate. in plant micronutrient use efficiency, m.a. hossain, t. kamiya, d.j. burritt, l.-s.p. tran and t. fujiwara, eds. (london: academic press), pp 209-224. palaniveloo k, amran ma, norhashim na, mohamad-fauzi n, peng-hui f, hui-wen l, kai-lin y, jiale l, chian-yee mg and jing-yi l (2020), food waste composting and microbial community structure profiling, processes. 8: 723. doi: org/10.3390/ pr8060723 partey st, thevathasan nv, zougmoré rb and preziosi rf (2018), improving maize production through nitrogen supply from tenrarely-used organic resources in ghana, agrofor syst. 92: 375-387. doi: 10.1007/ s10457-016-0035-8 pituello c, polese r, morari f and berti a (2016), outcomes from a long-term study on crop residue effects on plant yield and nitrogen use efficiency in contrasting soils, eur j agron. 77: 179-187. doi: 10.1016/j. eja.2015.11.027 somerville pd, farrell c, may pb and livesley sj (2020), biochar and compost equally improve urban soil physical and biological properties and tree growth, with no added benefit in combination, sci total environ. 706: 135-736. doi: 10.1016/j.scitotenv. 2019.135736 tan d, liu z, jiang l, luo j and li j (2017), long-term potash application and wheat straw return reduced soil potassium fixation and affected crop yields in north china, nutr cycl agroecosyst. doi: 10.1007/s10705 017-9843-0 wang w, sardans j, wang c, pan t, zeng c, lai d, bartrons m and peñuelas j (2017), straw application strategy to optimize nutrient release in a southeastern china rice cropland, agronomy. 7. doi: 10.3390/agronomy 7040084 xin x, qin s, zhang j, zhu a, yang w and zhang x (2017), yield, phosphorus use efficiency and balance response to substituting long-term chemical fertilizer use with organic manure in a wheat-maize system, field crop res. 208: 27-33. doi: 10.1016/j.fcr.2017.03.011 yang hs, xu mm, koide rt, liu q, dai yj, liu l and bian xm (2016), effects of ditch-buried straw return on water percolation, nitrogen leaching and crop yields in a rice-wheat rotation system, j sc. food agric. 96: 1141-1149. doi: 10.1002/jsfa.7196 zhang p, chen x, wei t, yang z, jia z, yang b, han q and ren x (2016), effects of straw incorporation on the soil nutrient contents, enzyme activities, and crop yield in a semiarid region of china, soil tillage res. 160: 65-72. doi: 10.1016/j.still.2016.02.006 zhang y, liu y, zhang g, guo x, sun z and li t (2018), the effects of rice straw and biochar applications on the microbial community in a soil with a history of continuous tomato planting history, agronomy. 8. doi: 10.3390/agronomy8050065 zhao fj, mcgrath sp and meharg aa (2010), arsenic as a food chain contaminant: mechanisms of plant uptake and metabolism and mitigation strategies, annu rev plant biol. 61: 535-559. doi: 10.1146/annurev-arplant-042809-112152 table iv. impacts of applied organic composts on mineral nutrition of rice plant tissues grown during aman season in patuakhali district of bangladesh treatment nitrogen phosphorus sulfur potassium calcium magnesium total (g kg-1) t0 = control 9.6 e 1.1 a 11.9 b 3.86 ab 3.3 a 2.76 t1 = rhc2 11.3 be 1.34 a 13.6 ab 3.32 a 3.92 ab 3.18 t2 = rhc4 13 ab 1.58 ab 13.8 ab 4.5 abc 5.6 abc 3.29 t3 = rhc8 15.7 acd 2.24 ab 14.7 abc 4.96 abc 7.21 cdef 3.35 t4 = rsc2 14.6 ac 2.05 ab 14 ab 3.9 ab 6.13 abcd 3.66 t5 = rsc4 17.1 cdf 2.7 ab 15.5 acd 5.2 abc 8.77 defg 4.71 t6 = rsc8 20.5 gh 3.65 ab 17.9 de 6.79 bc 11.3 gh 4.68 t7 = sdc2 11.6 be 1.78 ab 13.7 ab 4.52 abc 5.05 abc 3.53 t8 = sdc4 14 ab 2.23 ab 14.6 abc 5.09 abc 5.94 abcd 3.82 t9 = sdc8 18.1 dfg 3.12 ab 17.3 cde 6.9 c 9.67 fgh 4.65 t10 = v2 15.7 acd 2.35 ab 16.3 acd 4.55 abc 6.64 bcde 4.09 t11 = v4 18.8 fgh 3.13 ab 17 cde 6.17 abc 9.13 efgh 4.96 t12 = v8 21.4 h 4.42 b 19.7 e 7.27 c 11.87 h 5.54 in a column, means followed by a common letter are not significantly different at 5% level by tukey’s range test table v. correlation between the treatments and mineral nutrition of rice plant tissues nutrition coefficient stand. error t stat p-value lower 95% upper 95% nitrogen 1.0133 0.2394 4.2322 0.0014 0.4863 1.5403 phosphorus 0.2588 0.0655 3.9541 0.0023 0.1148 0.4029 potassium 0.6295 0.1663 3.7864 0.0030 0.2636 0.9955 sulphur 0.3697 0.0767 4.8205 0.0005 0.2009 0.5385 calcium 0.7854 0.1656 4.7437 0.0006 0.4210 1.1498 magnesium 0.1778 0.0706 2.5189 0.0285 0.0224 0.3332 mineral nutrition of rice and post-harvest soils influenced by self-made organic composts 58(2) 2023104 however, until now, the use of straw incorporation to increase crop yield is still a matter of argument since studies in different climates and soil types have led to inconclusive results (pituello et al. 2016). it has been reported that straw incorporation has significant valuable effects on crop yields and soil properties. for instance, straw incorporation can increase crop yields (yang et al. 2016), soil organic matter and other soil nutrients (zhang et al. 2018). straw return can also improve soil physical properties, such as by increasing hydraulic conductivity, decreasing bulk density, and enhancing aggregate formation (yang et al. 2016). vermicompost is a nourishing organic fertilizer having high amount of humus, nitrogen 2–3%, phosphorous 1.55–2.25%, potassium 1.85–2.25%, micronutrients, more beneficial for soil microbes like ‘nitrogen fixing bacteria’ and mycorrhizal fungi. vermicompost has been scientifically proved as miracle plant growth enhancer (guerrero, 2010). ansari and ismail (2012) reported that worms vermicompost contains 7.37 % nitrogen and 19.58% phosphorous as p2o5. microbial population of n2fixing bacteria and actinomycetes increases by the application of vermicompost. the amplified microbial activities improve the availability of soil phosphorous and nitrogen. vermicomposting is an aerobic, biological method and is proficient to convert eco-friendly hummus like organic substances (chanda et al. 2011). vermicompost stimulates to influence the microbial activity of soil, increases the availability of oxygen, maintains normal soil temperature, increases soil porosity and infiltration of water, improves nutrient content and increases growth, yield and quality of the plant (arora et al. 2011). rice hull and sawdust are also important agricultural amendments. growth and yield components of rice grown in saline soil were found to be increased significantly (p ≤ 0.05) by the application of rice hull, rice straw and sawdust alone and in combination (akter et al. 2018). the physico-chemical properties and nutrient status of post-harvest soils were also found to be influenced by the application of these amendments (akter and khan, 2019). composting is a low-cost natural way of recycling and stabilizing organic matter under thermophilic temperature that forms a pathogen-free substrate, beneficial to crops (gurtler et al. 2018; somerville et al. 2020). low-income farmers found it more advantageous to them. composting was found to be a promising practice that brought organic materials to a certain stage by narrowing down its c:n ratio where nutrients are easily accessible to plants (palaniveloo et al. 2020). partey et al. (2018) and dinesh et al. (2011), had consolidated that biomass needs to decompose for making n available to crops. thus, composting locally available organic amendments (oas) is essential for a healthy and sustainable agro-ecosystem in different climatic conditions. therefore, the objectives of the study were to evaluate the nutrient statuses of post-harvest soils and rice plants grown in aman season as influenced by the different rates of organic composts applied under field condition. materials and methods study site and experimental design in patuakhali a district of bangladesh, the field experiment was conducted in bilbilash of bauphal upazila (map i), which is located between 22°20ʹ00ʺn and 90°20ʹ00ʺe longitude within agro-ecological zone-13 named as ganges tidal floodplain. the climatic condition of this area is usually known as ‘tropical monsoon climate’. the area mainly enjoys three seasons such as rainy, dry and summer season. the experiment was carried out following completely randomized block design with the self-made organic composts, such as, rice hull compost (rhc), rice straw compost (rsc), sawdust compost (sdc) and vermicompost (v) corresponding to the rates of 0, 2, 4 and 8 t ha-1 of each organic compost at aman season during august to december, 2018. there were 13 plots having individual treatment (table i) in the experimental area, each unit plot size was 16 m2 (4m×4m) and replications were considered within the plot. selected properties of potential amendments used and initial soils at field site are presented in the tables ii and iii. transplantation following subsequent protocols basal doses of n, p2o5, and k2o from urea, tsp, and mop fertilizers were applied at the rates of 40, 30, and 15 kg ha-1, respectively considering soil amendments and initial contents of the nutrients. during field preparation, the tsp, mop, and half of the urea were applied in their entirety after being thoroughly mixed with the field soil. the remaining urea was top dressed in two splits, one at the beginning of the rice panicle and another at the active tillering stage. three seedlings per hill of the br 25 variety, which were thirty days old and in good health, were transplanted. row to row and hill to hill distances were each 20 and 22 cm, respectively. no irrigation was required for this study for the growth of rice in this season. intercultural operations such as, weeding, pesticide use, etc. were done as per requirement. sample collection and analyses plant samples were collected from each plot just after harvesting. soil samples were collected from 3 spots as replications of each plot of active root zone (0-15 cm) with the help of an auger. soil samples were then stored treatment wise in polythene bags with proper labeling. after sun drying and grounding the samples were then passed through 2 mm sieve and stored properly in air tight plastic pots for further analyses. the collected plant samples were sun dried and weighed. after sun drying a portion of the collected plant samples were oven dried at 65⁰c and then grinded and stored in air tight plastic pots for laboratory analyses. all the laboratory analyses were done following standard methods. statistical analyses pearson correlation and regression analyses between treatments and mineral nutrition of rice plants, analysis of variance (anova) and tukey’s range test at 5% (p≤ 0.05) level were done for the interpretation of the experimental results. results and discussion mineral nutrition of rice plants the total nitrogen, phosphorus, potassium, sulfur, calcium and magnesium contents at maturity stage of rice plants grown under field condition were significantly (p≤0.05) influenced by the application of variable indigenous organic amendments (rice hull compost, rice straw compost, sawdust compost and vermicompost) during aman season (table iv and fig.1). pearson correlation and regression analyses have been performed between the different treatments and mineral nutrition of rice plant tissues (table v). significance has been determined based on p values whether they were <0.05 or not. the total nitrogen (r = 0.78***), phosphorus (r = 0.77**), potassium (r = 0.75**), sulfur (r = 0.82***), calcium (r = 0.82***) and magnesium (r = 0.60*) contents of the tested rice plant (br 25) tissues were significantly correlated with the applied organic composts and these correlations confirmed that the different sources of organic materials positively influenced the nutrition of rice plant tissues which ultimately regulate the edible part (grain) of the rice crops. according to graham et al. (2012), people taking cereal based diets still suffering from hidden hunger of nutrients due to low level and low bioavailability of essential elements. the present results demonstrated that the nitrogen content in rice straw increased with the increased rate of the application of organic composts. the maximum nitrogen contents in the rice plant tissues were recorded at v8 treatment for the tested variety. among the applied composts, vermicompost (18.63 g kg-1n) ranked first followed by rice straw compost (17.40 g kg-1), sawdust compost (14.57g kg-1) and rice hull compost (13.33 g kg-1), regardless of their doses. phosphorus contents in rice plant tissues increased with the higher rates of the different composts. the highest (4.42 g kg-1) and lowest (1.10 g kg-1) contents of total phosphorus were recorded in the t12 (v8) and t0 (control) treatments. the rest of the above-mentioned nutrients were exerted the similar trends as those obtained by the p and n contents by the different organic composts. the nutrition of rice shoots was influenced by the direction of vermicompost > rice straw compost > sawdust compost > rice hull compost for the studied variety of rice grown under field condition. nutrient status of post-harvest soils rice production during t. aman season, the available n contents in the post-harvest soils increased significantly (p ≤ 0.05) by the application of vermicompost, rice hull compost, rice straw compost and sawdust compost (table vi and fig. 2). the maximum amount of available n (78.29 mg kg-1) was recorded in t3 (rhc8) treatment, where available nitrogen content increased 85.65% as compared to control plot. at the same dose (8 t ha-1), the sawdust compost treatment ranked second for the available nitrogen content (62.31 mg kg-1) at post-harvest soils followed by rsc8 treatment (60.76 mg kg-1). there were significant (p≤0.05) increase in available phosphorus and sulfur, exchangeable potassium, calcium and magnesium at post-harvest soils with the increased doses of the organic amendments under rice production (table vi). soils treated with vermicompost at the rate of 8 t ha-1 was found to have significantly more phosphorus (12.57 mg kg-1) as compared to control plot. the rice straw compost and sawdust compost each at 8 t ha-1 were showed almost similar trends in the increment of available phosphorus contents in post-harvest soils followed by rice hull compost. the other nutrients of post-harvest soils followed the similar trends as that of phosphorus, except for the exchangeable potassium, where rice straw compost at the highest rate (8 t ha-1) exhibited the best response (0.97 c molc kg -1) than those of the other treatments. the maximum amounts of available sulfur, exchangeable calcium and magnesium were obtained from the highest dose of vermicompost and the minimum amounts were attained by the control plot. the trend of increments of all these nutrients were more pronounced with the higher rates of the applied organic amendments indicate that all the applied organic composts are suitable sources for improving nutrient statuses of soils. pearson correlation and regression analyses also indicate the strong positive relationship between the treatments and nutrient statuses of post-harvest soils (table vii). the current findings are in consistent with those of xin et al. (2017). many steps have been made to improve soil fertility and productivity, according to them. increased organic input, such as organic manure, compost, and straw integration, are the most effective approaches. crop straw, a cheap and nutrient-dense material, offers a lot of potential for enhancing soil fertility (tan et al. 2017). crop straw, which is high in nutrients and organic elements, can be treated as a natural organic fertilizer and utilized as an alternative to chemical fertilizers, according to the studies of wang et al. (2017). as a result, straw integration appears to be a potential method for maintaining and restoring soil fertility, the burning issue of present day. because, mineral elements are required for the healthy growth and development of both plants and humans. the plant roots take up the mineral nutrients from soil and transported them to the edible parts for human consumption through various transporters. for human health, an ideal future crop should be rich in essential mineral elements but with less toxic elements in the edible parts. still, it is estimated that nearly 2 billion people are suffering from deficiency of nutrients because of low availability of mineral elements in soil and/or low accumulation/bioavailability of mineral elements in edible parts (graham et al. 2012). this so-called hidden hunger is an especially serious health problem for people subsisting on cereal-based diets because cereals such as rice usually contain a low level of mineral elements as well as low bioavailability (grebmer et al. 2014; nakandalage and seneweera, 2018). on the other hand, rapid urbanization and industrialization cause contamination by toxic elements in many soils used for crop production (zhao et al. 2010; clemens and ma, 2016), which threaten our health throughout the food chain. therefore, it is extremely important to boost essential nutrients (both density and bioavailability) and reduce toxic elements in edible parts of cereals for human health. conclusion the present research findings conclude that the locally made organic composts using indigenous organic materials had potential to improve soil fertility and provide nutrients for rice production. significant positive correlation between the treatments and mineral nutrients of rice plants confirmed the strong relationship of organic farming for sustainable agriculture. there were significant (p ≤ 0.05) increase in available phosphorus and sulfur, exchangeable potassium, calcium and magnesium at post-harvest soils with the increased doses of amendments under rice production. the nutrition of rice plants grown under field condition was influenced most by the vermicompost and followed the order of the treatments as rice straw compost > sawdust compost > rice hull compost for the studied variety of rice. these results resemble that the further researches are needed to find out the suitable doses and types of the amendments. however, the applied organic fertilizers were found to have responses on the nutritional statuses of rice shoot and post-harvest soils and these might be effective for the nutritional balance of the rice variety and ultimately will be helpful for country’s penniless people to combat their existing and future demand of quality rice. acknowledgement the study was carried out under a project of the climate change trust fund (cctf) titled ‘assessment of impacts of climate change on soil health and food security, and adaptation of climate-smart agriculture in most adversely affected areas of bangladesh’ through the moefcc, government of the peoples’ republic of bangladesh. the project was implemented in two phases (phase i: jan.’17 to dec.’18, code 410 duand phase ii: jan.’19 to dec.’22, code 573 du) within six years. we are also grateful to the project staff and relevant officers/staff of the swed-du, du, moe and moefcc of gob, who performed for the successful completion of the study. references ahmed s, alam mj, hossain a, islam ak, awan th, soufan w, qahtan aa, okla mk and sabagh si (2021), interactive effect of weeding regimes, rice cultivars, and seeding rates influence the rice-weed competition under dry direct-seeded condition, sustainability. 13: 317-321. doi: 10.3390/su13010317 akter s and khan hr (2019), influence of rice hull, rice straw, sawdust and moisture levels on selected properties of post harvested saline soils under variable conditions of rice cultivation, national university journal of science. 6(1): 61-74. akter s, khan hr, hossain ms, saha mk and farzana f (2018), response of rice grown in saline soil as influenced by the application of agricultural amendments and moisture regimes, j biodivers conserv bioresour manag. 4(2): 33-42. doi: https://doi.org/ 10.3329/jbcbm.v4i2.39845 ansari aa and ismail sa (2012), role of earthworms in vermtechnology, j agric technol. 8(2): 405-415. https://www.ijat-aatsea.com arora vk, singh cb, sidhu as and thind ss (2011), irrigation, tillage and mulching effects on soybean yield and water productivity in relation to soil texture, agric water manag. 98(4): 563-568. https://doi.org/10.1016/j.agwat .2010.10.004 bbs (2017), bangladesh bureau of statistics. the year book of agricultural statistics of bangladesh. stat. div. minis. planning, govt. peoples repub. bangladesh, dhaka. bbs (2020), summary crop statistics and crop indices (2019-2020). bangladesh bureau of statistics division, govt. of the people’s republic of bangladesh: dhaka, bangladesh. pp 35-37. chanda gc, bhunia g and chakraborty sk (2011), the effect of vermicompost and other fertilizers on cultivation of tomato plants, j hortic for. 3: 42-45. http://www.acade mic journals.org/jhf clemens s and ma jf (2016), toxic heavy metal and metalloid accumulation in crop plants and foods, annu rev plant biol. 67: 489-512. doi: 10.1146/annurev-arplant-043015-112301 dinesh r, suryanarayana ma, nair ak and chaudhuri sg (2011), leguminous cover crop effects on nitrogen mineralization rates and kinetics in soils, j agron crop sci. 187: 161-166. doi: 10.1046/j.1439-037x. 2001. 00512.x frg (2012), (fertilizer recommendation guide). bangladesh agricultural research council (barc), dhaka, bangladesh. graham rd, knez m and welch rm (2012), how much nutritional iron deficiency in humans globally is due to an underlying zinc deficiency, adv agron. 1-40. doi: 10.1016/b978-0-12-394276-0.00001-9 grebmer bkv, saltzman a, birol e, wiesmann d, prasai n, yins, yohannes y, menon p, thompson j and sonntag a (2014), 2014 global hunger index: the challenge of hidden hunger (washington, dc: international food policy research institute), pp 56. doi: http://dx.doi.org/10.2499/9780896299580 guerrero rd (2010), vermicompost production and its use for crop production in the philippines, international journal of global environmental issues. 10(3/4): 378-383. doi: 10.1504/ijgenvi.2010.037278 gurtler jb, doyle mp, erickson mc, jiang x, millner p and sharma m (2018), composting to inactivate food borne pathogens for crop soil application, a review j food prot.81: 1821-1837. doi: 10.4315/0362-028x.jfp-18-217 heitkamp f, raupp j and ludwig b (2011), soil organic matter pools and crop yields as affected by the rate of farmyard manure and use of biodynamic preparations in a sandy soil, organic agriculture. 11: 111-124. doi: 10.1007/s13165-011-0010-7 jahiruddin m and satter ma (2010), research priority in agriculture and development of vision document-2030 and beyond. land and soil resource management. bangladesh gricultural research council. dhaka. jeptoo a, aguyoh jn and saidi m (2013), improving carrot yield and quality through the use of bio-slurry manure, sustainable agricultural research. 2(1): 164-172. doi: 10.5539/sar.v2n1p164 nakandalage n and seneweera s (2018), micronutrients useefficiency of crop-plants under changing climate. in plant micronutrient use efficiency, m.a. hossain, t. kamiya, d.j. burritt, l.-s.p. tran and t. fujiwara, eds. (london: academic press), pp 209-224. palaniveloo k, amran ma, norhashim na, mohamad-fauzi n, peng-hui f, hui-wen l, kai-lin y, jiale l, chian-yee mg and jing-yi l (2020), food waste composting and microbial community structure profiling, processes. 8: 723. doi: org/10.3390/ pr8060723 partey st, thevathasan nv, zougmoré rb and preziosi rf (2018), improving maize production through nitrogen supply from tenrarely-used organic resources in ghana, agrofor syst. 92: 375-387. doi: 10.1007/ s10457-016-0035-8 pituello c, polese r, morari f and berti a (2016), outcomes from a long-term study on crop residue effects on plant yield and nitrogen use efficiency in contrasting soils, eur j agron. 77: 179-187. doi: 10.1016/j. eja.2015.11.027 somerville pd, farrell c, may pb and livesley sj (2020), biochar and compost equally improve urban soil physical and biological properties and tree growth, with no added benefit in combination, sci total environ. 706: 135-736. doi: 10.1016/j.scitotenv. 2019.135736 tan d, liu z, jiang l, luo j and li j (2017), long-term potash application and wheat straw return reduced soil potassium fixation and affected crop yields in north china, nutr cycl agroecosyst. doi: 10.1007/s10705 017-9843-0 wang w, sardans j, wang c, pan t, zeng c, lai d, bartrons m and peñuelas j (2017), straw application strategy to optimize nutrient release in a southeastern china rice cropland, agronomy. 7. doi: 10.3390/agronomy 7040084 xin x, qin s, zhang j, zhu a, yang w and zhang x (2017), yield, phosphorus use efficiency and balance response to substituting long-term chemical fertilizer use with organic manure in a wheat-maize system, field crop res. 208: 27-33. doi: 10.1016/j.fcr.2017.03.011 yang hs, xu mm, koide rt, liu q, dai yj, liu l and bian xm (2016), effects of ditch-buried straw return on water percolation, nitrogen leaching and crop yields in a rice-wheat rotation system, j sc. food agric. 96: 1141-1149. doi: 10.1002/jsfa.7196 zhang p, chen x, wei t, yang z, jia z, yang b, han q and ren x (2016), effects of straw incorporation on the soil nutrient contents, enzyme activities, and crop yield in a semiarid region of china, soil tillage res. 160: 65-72. doi: 10.1016/j.still.2016.02.006 zhang y, liu y, zhang g, guo x, sun z and li t (2018), the effects of rice straw and biochar applications on the microbial community in a soil with a history of continuous tomato planting history, agronomy. 8. doi: 10.3390/agronomy8050065 zhao fj, mcgrath sp and meharg aa (2010), arsenic as a food chain contaminant: mechanisms of plant uptake and metabolism and mitigation strategies, annu rev plant biol. 61: 535-559. doi: 10.1146/annurev-arplant-042809-112152 fig. 1. relationship between applied organic composts and mineral nutrition of rice plant tissues *,**,*** indicate the significant levels of correlation at 5%, 1% and 0.1%, respectively. akter, khan and saha 95 however, until now, the use of straw incorporation to increase crop yield is still a matter of argument since studies in different climates and soil types have led to inconclusive results (pituello et al. 2016). it has been reported that straw incorporation has significant valuable effects on crop yields and soil properties. for instance, straw incorporation can increase crop yields (yang et al. 2016), soil organic matter and other soil nutrients (zhang et al. 2018). straw return can also improve soil physical properties, such as by increasing hydraulic conductivity, decreasing bulk density, and enhancing aggregate formation (yang et al. 2016). vermicompost is a nourishing organic fertilizer having high amount of humus, nitrogen 2–3%, phosphorous 1.55–2.25%, potassium 1.85–2.25%, micronutrients, more beneficial for soil microbes like ‘nitrogen fixing bacteria’ and mycorrhizal fungi. vermicompost has been scientifically proved as miracle plant growth enhancer (guerrero, 2010). ansari and ismail (2012) reported that worms vermicompost contains 7.37 % nitrogen and 19.58% phosphorous as p2o5. microbial population of n2fixing bacteria and actinomycetes increases by the application of vermicompost. the amplified microbial activities improve the availability of soil phosphorous and nitrogen. vermicomposting is an aerobic, biological method and is proficient to convert eco-friendly hummus like organic substances (chanda et al. 2011). vermicompost stimulates to influence the microbial activity of soil, increases the availability of oxygen, maintains normal soil temperature, increases soil porosity and infiltration of water, improves nutrient content and increases growth, yield and quality of the plant (arora et al. 2011). rice hull and sawdust are also important agricultural amendments. growth and yield components of rice grown in saline soil were found to be increased significantly (p ≤ 0.05) by the application of rice hull, rice straw and sawdust alone and in combination (akter et al. 2018). the physico-chemical properties and nutrient status of post-harvest soils were also found to be influenced by the application of these amendments (akter and khan, 2019). composting is a low-cost natural way of recycling and stabilizing organic matter under thermophilic temperature that forms a pathogen-free substrate, beneficial to crops (gurtler et al. 2018; somerville et al. 2020). low-income farmers found it more advantageous to them. composting was found to be a promising practice that brought organic materials to a certain stage by narrowing down its c:n ratio where nutrients are easily accessible to plants (palaniveloo et al. 2020). partey et al. (2018) and dinesh et al. (2011), had consolidated that biomass needs to decompose for making n available to crops. thus, composting locally available organic amendments (oas) is essential for a healthy and sustainable agro-ecosystem in different climatic conditions. therefore, the objectives of the study were to evaluate the nutrient statuses of post-harvest soils and rice plants grown in aman season as influenced by the different rates of organic composts applied under field condition. materials and methods study site and experimental design in patuakhali a district of bangladesh, the field experiment was conducted in bilbilash of bauphal upazila (map i), which is located between 22°20ʹ00ʺn and 90°20ʹ00ʺe longitude within agro-ecological zone-13 named as ganges tidal floodplain. the climatic condition of this area is usually known as ‘tropical monsoon climate’. the area mainly enjoys three seasons such as rainy, dry and summer season. the experiment was carried out following completely randomized block design with the self-made organic composts, such as, rice hull compost (rhc), rice straw compost (rsc), sawdust compost (sdc) and vermicompost (v) corresponding to the rates of 0, 2, 4 and 8 t ha-1 of each organic compost at aman season during august to december, 2018. there were 13 plots having individual treatment (table i) in the experimental area, each unit plot size was 16 m2 (4m×4m) and replications were considered within the plot. selected properties of potential amendments used and initial soils at field site are presented in the tables ii and iii. transplantation following subsequent protocols basal doses of n, p2o5, and k2o from urea, tsp, and mop fertilizers were applied at the rates of 40, 30, and 15 kg ha-1, respectively considering soil amendments and initial contents of the nutrients. during field preparation, the tsp, mop, and half of the urea were applied in their entirety after being thoroughly mixed with the field soil. the remaining urea was top dressed in two splits, one at the beginning of the rice panicle and another at the active tillering stage. three seedlings per hill of the br 25 variety, which were thirty days old and in good health, were transplanted. row to row and hill to hill distances were each 20 and 22 cm, respectively. no irrigation was required for this study for the growth of rice in this season. intercultural operations such as, weeding, pesticide use, etc. were done as per requirement. sample collection and analyses plant samples were collected from each plot just after harvesting. soil samples were collected from 3 spots as replications of each plot of active root zone (0-15 cm) with the help of an auger. soil samples were then stored treatment wise in polythene bags with proper labeling. after sun drying and grounding the samples were then passed through 2 mm sieve and stored properly in air tight plastic pots for further analyses. the collected plant samples were sun dried and weighed. after sun drying a portion of the collected plant samples were oven dried at 65⁰c and then grinded and stored in air tight plastic pots for laboratory analyses. all the laboratory analyses were done following standard methods. statistical analyses pearson correlation and regression analyses between treatments and mineral nutrition of rice plants, analysis of variance (anova) and tukey’s range test at 5% (p≤ 0.05) level were done for the interpretation of the experimental results. results and discussion mineral nutrition of rice plants the total nitrogen, phosphorus, potassium, sulfur, calcium and magnesium contents at maturity stage of rice plants grown under field condition were significantly (p≤0.05) influenced by the application of variable indigenous organic amendments (rice hull compost, rice straw compost, sawdust compost and vermicompost) during aman season (table iv and fig.1). pearson correlation and regression analyses have been performed between the different treatments and mineral nutrition of rice plant tissues (table v). significance has been determined based on p values whether they were <0.05 or not. the total nitrogen (r = 0.78***), phosphorus (r = 0.77**), potassium (r = 0.75**), sulfur (r = 0.82***), calcium (r = 0.82***) and magnesium (r = 0.60*) contents of the tested rice plant (br 25) tissues were significantly correlated with the applied organic composts and these correlations confirmed that the different sources of organic materials positively influenced the nutrition of rice plant tissues which ultimately regulate the edible part (grain) of the rice crops. according to graham et al. (2012), people taking cereal based diets still suffering from hidden hunger of nutrients due to low level and low bioavailability of essential elements. the present results demonstrated that the nitrogen content in rice straw increased with the increased rate of the application of organic composts. the maximum nitrogen contents in the rice plant tissues were recorded at v8 treatment for the tested variety. among the applied composts, vermicompost (18.63 g kg-1n) ranked first followed by rice straw compost (17.40 g kg-1), sawdust compost (14.57g kg-1) and rice hull compost (13.33 g kg-1), regardless of their doses. phosphorus contents in rice plant tissues increased with the higher rates of the different composts. the highest (4.42 g kg-1) and lowest (1.10 g kg-1) contents of total phosphorus were recorded in the t12 (v8) and t0 (control) treatments. the rest of the above-mentioned nutrients were exerted the similar trends as those obtained by the p and n contents by the different organic composts. the nutrition of rice shoots was influenced by the direction of vermicompost > rice straw compost > sawdust compost > rice hull compost for the studied variety of rice grown under field condition. nutrient status of post-harvest soils rice production during t. aman season, the available n contents in the post-harvest soils increased significantly (p ≤ 0.05) by the application of vermicompost, rice hull compost, rice straw compost and sawdust compost (table vi and fig. 2). the maximum amount of available n (78.29 mg kg-1) was recorded in t3 (rhc8) treatment, where available nitrogen content increased 85.65% as compared to control plot. at the same dose (8 t ha-1), the sawdust compost treatment ranked second for the available nitrogen content (62.31 mg kg-1) at post-harvest soils followed by rsc8 treatment (60.76 mg kg-1). there were significant (p≤0.05) increase in available phosphorus and sulfur, exchangeable potassium, calcium and magnesium at post-harvest soils with the increased doses of the organic amendments under rice production (table vi). soils treated with vermicompost at the rate of 8 t ha-1 was found to have significantly more phosphorus (12.57 mg kg-1) as compared to control plot. the rice straw compost and sawdust compost each at 8 t ha-1 were showed almost similar trends in the increment of available phosphorus contents in post-harvest soils followed by rice hull compost. the other nutrients of post-harvest soils followed the similar trends as that of phosphorus, except for the exchangeable potassium, where rice straw compost at the highest rate (8 t ha-1) exhibited the best response (0.97 c molc kg -1) than those of the other treatments. the maximum amounts of available sulfur, exchangeable calcium and magnesium were obtained from the highest dose of vermicompost and the minimum amounts were attained by the control plot. the trend of increments of all these nutrients were more pronounced with the higher rates of the applied organic amendments indicate that all the applied organic composts are suitable sources for improving nutrient statuses of soils. pearson correlation and regression analyses also indicate the strong positive relationship between the treatments and nutrient statuses of post-harvest soils (table vii). the current findings are in consistent with those of xin et al. (2017). many steps have been made to improve soil fertility and productivity, according to them. increased organic input, such as organic manure, compost, and straw integration, are the most effective approaches. crop straw, a cheap and nutrient-dense material, offers a lot of potential for enhancing soil fertility (tan et al. 2017). crop straw, which is high in nutrients and organic elements, can be treated as a natural organic fertilizer and utilized as an alternative to chemical fertilizers, according to the studies of wang et al. (2017). as a result, straw integration appears to be a potential method for maintaining and restoring soil fertility, the burning issue of present day. because, mineral elements are required for the healthy growth and development of both plants and humans. the plant roots take up the mineral nutrients from soil and transported them to the edible parts for human consumption through various transporters. for human health, an ideal future crop should be rich in essential mineral elements but with less toxic elements in the edible parts. still, it is estimated that nearly 2 billion people are suffering from deficiency of nutrients because of low availability of mineral elements in soil and/or low accumulation/bioavailability of mineral elements in edible parts (graham et al. 2012). this so-called hidden hunger is an especially serious health problem for people subsisting on cereal-based diets because cereals such as rice usually contain a low level of mineral elements as well as low bioavailability (grebmer et al. 2014; nakandalage and seneweera, 2018). on the other hand, rapid urbanization and industrialization cause contamination by toxic elements in many soils used for crop production (zhao et al. 2010; clemens and ma, 2016), which threaten our health throughout the food chain. therefore, it is extremely important to boost essential nutrients (both density and bioavailability) and reduce toxic elements in edible parts of cereals for human health. conclusion the present research findings conclude that the locally made organic composts using indigenous organic materials had potential to improve soil fertility and provide nutrients for rice production. significant positive correlation between the treatments and mineral nutrients of rice plants confirmed the strong relationship of organic farming for sustainable agriculture. there were significant (p ≤ 0.05) increase in available phosphorus and sulfur, exchangeable potassium, calcium and magnesium at post-harvest soils with the increased doses of amendments under rice production. the nutrition of rice plants grown under field condition was influenced most by the vermicompost and followed the order of the treatments as rice straw compost > sawdust compost > rice hull compost for the studied variety of rice. these results resemble that the further researches are needed to find out the suitable doses and types of the amendments. however, the applied organic fertilizers were found to have responses on the nutritional statuses of rice shoot and post-harvest soils and these might be effective for the nutritional balance of the rice variety and ultimately will be helpful for country’s penniless people to combat their existing and future demand of quality rice. acknowledgement the study was carried out under a project of the climate change trust fund (cctf) titled ‘assessment of impacts of climate change on soil health and food security, and adaptation of climate-smart agriculture in most adversely affected areas of bangladesh’ through the moefcc, government of the peoples’ republic of bangladesh. the project was implemented in two phases (phase i: jan.’17 to dec.’18, code 410 duand phase ii: jan.’19 to dec.’22, code 573 du) within six years. we are also grateful to the project staff and relevant officers/staff of the swed-du, du, moe and moefcc of gob, who performed for the successful completion of the study. references ahmed s, alam mj, hossain a, islam ak, awan th, soufan w, qahtan aa, okla mk and sabagh si (2021), interactive effect of weeding regimes, rice cultivars, and seeding rates influence the rice-weed competition under dry direct-seeded condition, sustainability. 13: 317-321. doi: 10.3390/su13010317 akter s and khan hr (2019), influence of rice hull, rice straw, sawdust and moisture levels on selected properties of post harvested saline soils under variable conditions of rice cultivation, national university journal of science. 6(1): 61-74. akter s, khan hr, hossain ms, saha mk and farzana f (2018), response of rice grown in saline soil as influenced by the application of agricultural amendments and moisture regimes, j biodivers conserv bioresour manag. 4(2): 33-42. doi: https://doi.org/ 10.3329/jbcbm.v4i2.39845 ansari aa and ismail sa (2012), role of earthworms in vermtechnology, j agric technol. 8(2): 405-415. https://www.ijat-aatsea.com arora vk, singh cb, sidhu as and thind ss (2011), irrigation, tillage and mulching effects on soybean yield and water productivity in relation to soil texture, agric water manag. 98(4): 563-568. https://doi.org/10.1016/j.agwat .2010.10.004 bbs (2017), bangladesh bureau of statistics. the year book of agricultural statistics of bangladesh. stat. div. minis. planning, govt. peoples repub. bangladesh, dhaka. bbs (2020), summary crop statistics and crop indices (2019-2020). bangladesh bureau of statistics division, govt. of the people’s republic of bangladesh: dhaka, bangladesh. pp 35-37. chanda gc, bhunia g and chakraborty sk (2011), the effect of vermicompost and other fertilizers on cultivation of tomato plants, j hortic for. 3: 42-45. http://www.acade mic journals.org/jhf clemens s and ma jf (2016), toxic heavy metal and metalloid accumulation in crop plants and foods, annu rev plant biol. 67: 489-512. doi: 10.1146/annurev-arplant-043015-112301 dinesh r, suryanarayana ma, nair ak and chaudhuri sg (2011), leguminous cover crop effects on nitrogen mineralization rates and kinetics in soils, j agron crop sci. 187: 161-166. doi: 10.1046/j.1439-037x. 2001. 00512.x frg (2012), (fertilizer recommendation guide). bangladesh agricultural research council (barc), dhaka, bangladesh. graham rd, knez m and welch rm (2012), how much nutritional iron deficiency in humans globally is due to an underlying zinc deficiency, adv agron. 1-40. doi: 10.1016/b978-0-12-394276-0.00001-9 grebmer bkv, saltzman a, birol e, wiesmann d, prasai n, yins, yohannes y, menon p, thompson j and sonntag a (2014), 2014 global hunger index: the challenge of hidden hunger (washington, dc: international food policy research institute), pp 56. doi: http://dx.doi.org/10.2499/9780896299580 guerrero rd (2010), vermicompost production and its use for crop production in the philippines, international journal of global environmental issues. 10(3/4): 378-383. doi: 10.1504/ijgenvi.2010.037278 gurtler jb, doyle mp, erickson mc, jiang x, millner p and sharma m (2018), composting to inactivate food borne pathogens for crop soil application, a review j food prot.81: 1821-1837. doi: 10.4315/0362-028x.jfp-18-217 heitkamp f, raupp j and ludwig b (2011), soil organic matter pools and crop yields as affected by the rate of farmyard manure and use of biodynamic preparations in a sandy soil, organic agriculture. 11: 111-124. doi: 10.1007/s13165-011-0010-7 jahiruddin m and satter ma (2010), research priority in agriculture and development of vision document-2030 and beyond. land and soil resource management. bangladesh gricultural research council. dhaka. jeptoo a, aguyoh jn and saidi m (2013), improving carrot yield and quality through the use of bio-slurry manure, sustainable agricultural research. 2(1): 164-172. doi: 10.5539/sar.v2n1p164 nakandalage n and seneweera s (2018), micronutrients useefficiency of crop-plants under changing climate. in plant micronutrient use efficiency, m.a. hossain, t. kamiya, d.j. burritt, l.-s.p. tran and t. fujiwara, eds. (london: academic press), pp 209-224. palaniveloo k, amran ma, norhashim na, mohamad-fauzi n, peng-hui f, hui-wen l, kai-lin y, jiale l, chian-yee mg and jing-yi l (2020), food waste composting and microbial community structure profiling, processes. 8: 723. doi: org/10.3390/ pr8060723 partey st, thevathasan nv, zougmoré rb and preziosi rf (2018), improving maize production through nitrogen supply from tenrarely-used organic resources in ghana, agrofor syst. 92: 375-387. doi: 10.1007/ s10457-016-0035-8 pituello c, polese r, morari f and berti a (2016), outcomes from a long-term study on crop residue effects on plant yield and nitrogen use efficiency in contrasting soils, eur j agron. 77: 179-187. doi: 10.1016/j. eja.2015.11.027 somerville pd, farrell c, may pb and livesley sj (2020), biochar and compost equally improve urban soil physical and biological properties and tree growth, with no added benefit in combination, sci total environ. 706: 135-736. doi: 10.1016/j.scitotenv. 2019.135736 tan d, liu z, jiang l, luo j and li j (2017), long-term potash application and wheat straw return reduced soil potassium fixation and affected crop yields in north china, nutr cycl agroecosyst. doi: 10.1007/s10705 017-9843-0 wang w, sardans j, wang c, pan t, zeng c, lai d, bartrons m and peñuelas j (2017), straw application strategy to optimize nutrient release in a southeastern china rice cropland, agronomy. 7. doi: 10.3390/agronomy 7040084 xin x, qin s, zhang j, zhu a, yang w and zhang x (2017), yield, phosphorus use efficiency and balance response to substituting long-term chemical fertilizer use with organic manure in a wheat-maize system, field crop res. 208: 27-33. doi: 10.1016/j.fcr.2017.03.011 yang hs, xu mm, koide rt, liu q, dai yj, liu l and bian xm (2016), effects of ditch-buried straw return on water percolation, nitrogen leaching and crop yields in a rice-wheat rotation system, j sc. food agric. 96: 1141-1149. doi: 10.1002/jsfa.7196 zhang p, chen x, wei t, yang z, jia z, yang b, han q and ren x (2016), effects of straw incorporation on the soil nutrient contents, enzyme activities, and crop yield in a semiarid region of china, soil tillage res. 160: 65-72. doi: 10.1016/j.still.2016.02.006 zhang y, liu y, zhang g, guo x, sun z and li t (2018), the effects of rice straw and biochar applications on the microbial community in a soil with a history of continuous tomato planting history, agronomy. 8. doi: 10.3390/agronomy8050065 zhao fj, mcgrath sp and meharg aa (2010), arsenic as a food chain contaminant: mechanisms of plant uptake and metabolism and mitigation strategies, annu rev plant biol. 61: 535-559. doi: 10.1146/annurev-arplant-042809-112152 table vi. impacts of applied organic composts on nutrient statuses of post-harvest soils under rice production during aman season in patuakhali district of bangladesh treatment nitrogen phosphorus sulfur potassium calcium magnesium available (mg kg-1) exchangeable (c molckg -1) t0 = control 42.17 d 7.17 e 19.83 c 0.23 g 5.52 c 2.93 d t1 = rhc2 56.75 bc 8.37 e 21.38 bc 0.44 e 6.26 b 3.12 cd t2 = rhc4 61.14 b 9.89 cd 22.51 bc 0.87 ab 7.14 b 3.37 c t3 = rhc8 78.29 a 10.56 c 23.64 b 0.93 ab 8.17 ab 3.85 b t4 = rsc2 51.54 cd 9.85 cd 22.14 bc 0.52 d 6.57 b 3.20 cd t5 = rsc4 58.24 bc 10.16 23.21 b 0.71 c 7.29 b 3.46 bc t6 = rsc8 60.76 b 11.84 ab 24.19 b 0.97 a 8.36 ab 4.19 ab t7 = sdc2 49.68 cd 8.83 de 22.34 bc 0.35 f 5.79 c 2.96 cd t8 = sdc4 56.87 bc 10.19 23.15 b 0.62 cd 6.78 b 3.54 bc t9 = sdc8 62.31 b 11.86 ab 24.78 ab 0.94 ab 8.13 ab 3.81 b t10 = v2 47.32 d 9.63 cd 25.21 ab 0.61 cd 7.13 b 3.16 cd t11 = v4 53.76 c 10.85 bc 26.93 ab 0.85 b 8.27 ab 3.54 bc t12 = v8 57.74 bc 12.57 a 27.62 a 0.94 ab 8.92 a 4.48 a fig. 2. relationship between applied organic composts and nutrient statuses of post-harvest soils mineral nutrition of rice and post-harvest soils influenced by self-made organic composts96 58(2) 2023 however, until now, the use of straw incorporation to increase crop yield is still a matter of argument since studies in different climates and soil types have led to inconclusive results (pituello et al. 2016). it has been reported that straw incorporation has significant valuable effects on crop yields and soil properties. for instance, straw incorporation can increase crop yields (yang et al. 2016), soil organic matter and other soil nutrients (zhang et al. 2018). straw return can also improve soil physical properties, such as by increasing hydraulic conductivity, decreasing bulk density, and enhancing aggregate formation (yang et al. 2016). vermicompost is a nourishing organic fertilizer having high amount of humus, nitrogen 2–3%, phosphorous 1.55–2.25%, potassium 1.85–2.25%, micronutrients, more beneficial for soil microbes like ‘nitrogen fixing bacteria’ and mycorrhizal fungi. vermicompost has been scientifically proved as miracle plant growth enhancer (guerrero, 2010). ansari and ismail (2012) reported that worms vermicompost contains 7.37 % nitrogen and 19.58% phosphorous as p2o5. microbial population of n2fixing bacteria and actinomycetes increases by the application of vermicompost. the amplified microbial activities improve the availability of soil phosphorous and nitrogen. vermicomposting is an aerobic, biological method and is proficient to convert eco-friendly hummus like organic substances (chanda et al. 2011). vermicompost stimulates to influence the microbial activity of soil, increases the availability of oxygen, maintains normal soil temperature, increases soil porosity and infiltration of water, improves nutrient content and increases growth, yield and quality of the plant (arora et al. 2011). rice hull and sawdust are also important agricultural amendments. growth and yield components of rice grown in saline soil were found to be increased significantly (p ≤ 0.05) by the application of rice hull, rice straw and sawdust alone and in combination (akter et al. 2018). the physico-chemical properties and nutrient status of post-harvest soils were also found to be influenced by the application of these amendments (akter and khan, 2019). composting is a low-cost natural way of recycling and stabilizing organic matter under thermophilic temperature that forms a pathogen-free substrate, beneficial to crops (gurtler et al. 2018; somerville et al. 2020). low-income farmers found it more advantageous to them. composting was found to be a promising practice that brought organic materials to a certain stage by narrowing down its c:n ratio where nutrients are easily accessible to plants (palaniveloo et al. 2020). partey et al. (2018) and dinesh et al. (2011), had consolidated that biomass needs to decompose for making n available to crops. thus, composting locally available organic amendments (oas) is essential for a healthy and sustainable agro-ecosystem in different climatic conditions. therefore, the objectives of the study were to evaluate the nutrient statuses of post-harvest soils and rice plants grown in aman season as influenced by the different rates of organic composts applied under field condition. materials and methods study site and experimental design in patuakhali a district of bangladesh, the field experiment was conducted in bilbilash of bauphal upazila (map i), which is located between 22°20ʹ00ʺn and 90°20ʹ00ʺe longitude within agro-ecological zone-13 named as ganges tidal floodplain. the climatic condition of this area is usually known as ‘tropical monsoon climate’. the area mainly enjoys three seasons such as rainy, dry and summer season. the experiment was carried out following completely randomized block design with the self-made organic composts, such as, rice hull compost (rhc), rice straw compost (rsc), sawdust compost (sdc) and vermicompost (v) corresponding to the rates of 0, 2, 4 and 8 t ha-1 of each organic compost at aman season during august to december, 2018. there were 13 plots having individual treatment (table i) in the experimental area, each unit plot size was 16 m2 (4m×4m) and replications were considered within the plot. selected properties of potential amendments used and initial soils at field site are presented in the tables ii and iii. transplantation following subsequent protocols basal doses of n, p2o5, and k2o from urea, tsp, and mop fertilizers were applied at the rates of 40, 30, and 15 kg ha-1, respectively considering soil amendments and initial contents of the nutrients. during field preparation, the tsp, mop, and half of the urea were applied in their entirety after being thoroughly mixed with the field soil. the remaining urea was top dressed in two splits, one at the beginning of the rice panicle and another at the active tillering stage. three seedlings per hill of the br 25 variety, which were thirty days old and in good health, were transplanted. row to row and hill to hill distances were each 20 and 22 cm, respectively. no irrigation was required for this study for the growth of rice in this season. intercultural operations such as, weeding, pesticide use, etc. were done as per requirement. sample collection and analyses plant samples were collected from each plot just after harvesting. soil samples were collected from 3 spots as replications of each plot of active root zone (0-15 cm) with the help of an auger. soil samples were then stored treatment wise in polythene bags with proper labeling. after sun drying and grounding the samples were then passed through 2 mm sieve and stored properly in air tight plastic pots for further analyses. the collected plant samples were sun dried and weighed. after sun drying a portion of the collected plant samples were oven dried at 65⁰c and then grinded and stored in air tight plastic pots for laboratory analyses. all the laboratory analyses were done following standard methods. statistical analyses pearson correlation and regression analyses between treatments and mineral nutrition of rice plants, analysis of variance (anova) and tukey’s range test at 5% (p≤ 0.05) level were done for the interpretation of the experimental results. results and discussion mineral nutrition of rice plants the total nitrogen, phosphorus, potassium, sulfur, calcium and magnesium contents at maturity stage of rice plants grown under field condition were significantly (p≤0.05) influenced by the application of variable indigenous organic amendments (rice hull compost, rice straw compost, sawdust compost and vermicompost) during aman season (table iv and fig.1). pearson correlation and regression analyses have been performed between the different treatments and mineral nutrition of rice plant tissues (table v). significance has been determined based on p values whether they were <0.05 or not. the total nitrogen (r = 0.78***), phosphorus (r = 0.77**), potassium (r = 0.75**), sulfur (r = 0.82***), calcium (r = 0.82***) and magnesium (r = 0.60*) contents of the tested rice plant (br 25) tissues were significantly correlated with the applied organic composts and these correlations confirmed that the different sources of organic materials positively influenced the nutrition of rice plant tissues which ultimately regulate the edible part (grain) of the rice crops. according to graham et al. (2012), people taking cereal based diets still suffering from hidden hunger of nutrients due to low level and low bioavailability of essential elements. the present results demonstrated that the nitrogen content in rice straw increased with the increased rate of the application of organic composts. the maximum nitrogen contents in the rice plant tissues were recorded at v8 treatment for the tested variety. among the applied composts, vermicompost (18.63 g kg-1n) ranked first followed by rice straw compost (17.40 g kg-1), sawdust compost (14.57g kg-1) and rice hull compost (13.33 g kg-1), regardless of their doses. phosphorus contents in rice plant tissues increased with the higher rates of the different composts. the highest (4.42 g kg-1) and lowest (1.10 g kg-1) contents of total phosphorus were recorded in the t12 (v8) and t0 (control) treatments. the rest of the above-mentioned nutrients were exerted the similar trends as those obtained by the p and n contents by the different organic composts. the nutrition of rice shoots was influenced by the direction of vermicompost > rice straw compost > sawdust compost > rice hull compost for the studied variety of rice grown under field condition. nutrient status of post-harvest soils rice production during t. aman season, the available n contents in the post-harvest soils increased significantly (p ≤ 0.05) by the application of vermicompost, rice hull compost, rice straw compost and sawdust compost (table vi and fig. 2). the maximum amount of available n (78.29 mg kg-1) was recorded in t3 (rhc8) treatment, where available nitrogen content increased 85.65% as compared to control plot. at the same dose (8 t ha-1), the sawdust compost treatment ranked second for the available nitrogen content (62.31 mg kg-1) at post-harvest soils followed by rsc8 treatment (60.76 mg kg-1). there were significant (p≤0.05) increase in available phosphorus and sulfur, exchangeable potassium, calcium and magnesium at post-harvest soils with the increased doses of the organic amendments under rice production (table vi). soils treated with vermicompost at the rate of 8 t ha-1 was found to have significantly more phosphorus (12.57 mg kg-1) as compared to control plot. the rice straw compost and sawdust compost each at 8 t ha-1 were showed almost similar trends in the increment of available phosphorus contents in post-harvest soils followed by rice hull compost. the other nutrients of post-harvest soils followed the similar trends as that of phosphorus, except for the exchangeable potassium, where rice straw compost at the highest rate (8 t ha-1) exhibited the best response (0.97 c molc kg -1) than those of the other treatments. the maximum amounts of available sulfur, exchangeable calcium and magnesium were obtained from the highest dose of vermicompost and the minimum amounts were attained by the control plot. the trend of increments of all these nutrients were more pronounced with the higher rates of the applied organic amendments indicate that all the applied organic composts are suitable sources for improving nutrient statuses of soils. pearson correlation and regression analyses also indicate the strong positive relationship between the treatments and nutrient statuses of post-harvest soils (table vii). the current findings are in consistent with those of xin et al. (2017). many steps have been made to improve soil fertility and productivity, according to them. increased organic input, such as organic manure, compost, and straw integration, are the most effective approaches. crop straw, a cheap and nutrient-dense material, offers a lot of potential for enhancing soil fertility (tan et al. 2017). crop straw, which is high in nutrients and organic elements, can be treated as a natural organic fertilizer and utilized as an alternative to chemical fertilizers, according to the studies of wang et al. (2017). as a result, straw integration appears to be a potential method for maintaining and restoring soil fertility, the burning issue of present day. because, mineral elements are required for the healthy growth and development of both plants and humans. the plant roots take up the mineral nutrients from soil and transported them to the edible parts for human consumption through various transporters. for human health, an ideal future crop should be rich in essential mineral elements but with less toxic elements in the edible parts. still, it is estimated that nearly 2 billion people are suffering from deficiency of nutrients because of low availability of mineral elements in soil and/or low accumulation/bioavailability of mineral elements in edible parts (graham et al. 2012). this so-called hidden hunger is an especially serious health problem for people subsisting on cereal-based diets because cereals such as rice usually contain a low level of mineral elements as well as low bioavailability (grebmer et al. 2014; nakandalage and seneweera, 2018). on the other hand, rapid urbanization and industrialization cause contamination by toxic elements in many soils used for crop production (zhao et al. 2010; clemens and ma, 2016), which threaten our health throughout the food chain. therefore, it is extremely important to boost essential nutrients (both density and bioavailability) and reduce toxic elements in edible parts of cereals for human health. conclusion the present research findings conclude that the locally made organic composts using indigenous organic materials had potential to improve soil fertility and provide nutrients for rice production. significant positive correlation between the treatments and mineral nutrients of rice plants confirmed the strong relationship of organic farming for sustainable agriculture. there were significant (p ≤ 0.05) increase in available phosphorus and sulfur, exchangeable potassium, calcium and magnesium at post-harvest soils with the increased doses of amendments under rice production. the nutrition of rice plants grown under field condition was influenced most by the vermicompost and followed the order of the treatments as rice straw compost > sawdust compost > rice hull compost for the studied variety of rice. these results resemble that the further researches are needed to find out the suitable doses and types of the amendments. however, the applied organic fertilizers were found to have responses on the nutritional statuses of rice shoot and post-harvest soils and these might be effective for the nutritional balance of the rice variety and ultimately will be helpful for country’s penniless people to combat their existing and future demand of quality rice. acknowledgement the study was carried out under a project of the climate change trust fund (cctf) titled ‘assessment of impacts of climate change on soil health and food security, and adaptation of climate-smart agriculture in most adversely affected areas of bangladesh’ through the moefcc, government of the peoples’ republic of bangladesh. the project was implemented in two phases (phase i: jan.’17 to dec.’18, code 410 duand phase ii: jan.’19 to dec.’22, code 573 du) within six years. we are also grateful to the project staff and relevant officers/staff of the swed-du, du, moe and moefcc of gob, who performed for the successful completion of the study. references ahmed s, alam mj, hossain a, islam ak, awan th, soufan w, qahtan aa, okla mk and sabagh si (2021), interactive effect of weeding regimes, rice cultivars, and seeding rates influence the rice-weed competition under dry direct-seeded condition, sustainability. 13: 317-321. doi: 10.3390/su13010317 akter s and khan hr (2019), influence of rice hull, rice straw, sawdust and moisture levels on selected properties of post harvested saline soils under variable conditions of rice cultivation, national university journal of science. 6(1): 61-74. akter s, khan hr, hossain ms, saha mk and farzana f (2018), response of rice grown in saline soil as influenced by the application of agricultural amendments and moisture regimes, j biodivers conserv bioresour manag. 4(2): 33-42. doi: https://doi.org/ 10.3329/jbcbm.v4i2.39845 ansari aa and ismail sa (2012), role of earthworms in vermtechnology, j agric technol. 8(2): 405-415. https://www.ijat-aatsea.com arora vk, singh cb, sidhu as and thind ss (2011), irrigation, tillage and mulching effects on soybean yield and water productivity in relation to soil texture, agric water manag. 98(4): 563-568. https://doi.org/10.1016/j.agwat .2010.10.004 bbs (2017), bangladesh bureau of statistics. the year book of agricultural statistics of bangladesh. stat. div. minis. planning, govt. peoples repub. bangladesh, dhaka. bbs (2020), summary crop statistics and crop indices (2019-2020). bangladesh bureau of statistics division, govt. of the people’s republic of bangladesh: dhaka, bangladesh. pp 35-37. chanda gc, bhunia g and chakraborty sk (2011), the effect of vermicompost and other fertilizers on cultivation of tomato plants, j hortic for. 3: 42-45. http://www.acade mic journals.org/jhf clemens s and ma jf (2016), toxic heavy metal and metalloid accumulation in crop plants and foods, annu rev plant biol. 67: 489-512. doi: 10.1146/annurev-arplant-043015-112301 dinesh r, suryanarayana ma, nair ak and chaudhuri sg (2011), leguminous cover crop effects on nitrogen mineralization rates and kinetics in soils, j agron crop sci. 187: 161-166. doi: 10.1046/j.1439-037x. 2001. 00512.x frg (2012), (fertilizer recommendation guide). bangladesh agricultural research council (barc), dhaka, bangladesh. graham rd, knez m and welch rm (2012), how much nutritional iron deficiency in humans globally is due to an underlying zinc deficiency, adv agron. 1-40. doi: 10.1016/b978-0-12-394276-0.00001-9 grebmer bkv, saltzman a, birol e, wiesmann d, prasai n, yins, yohannes y, menon p, thompson j and sonntag a (2014), 2014 global hunger index: the challenge of hidden hunger (washington, dc: international food policy research institute), pp 56. doi: http://dx.doi.org/10.2499/9780896299580 guerrero rd (2010), vermicompost production and its use for crop production in the philippines, international journal of global environmental issues. 10(3/4): 378-383. doi: 10.1504/ijgenvi.2010.037278 gurtler jb, doyle mp, erickson mc, jiang x, millner p and sharma m (2018), composting to inactivate food borne pathogens for crop soil application, a review j food prot.81: 1821-1837. doi: 10.4315/0362-028x.jfp-18-217 heitkamp f, raupp j and ludwig b (2011), soil organic matter pools and crop yields as affected by the rate of farmyard manure and use of biodynamic preparations in a sandy soil, organic agriculture. 11: 111-124. doi: 10.1007/s13165-011-0010-7 jahiruddin m and satter ma (2010), research priority in agriculture and development of vision document-2030 and beyond. land and soil resource management. bangladesh gricultural research council. dhaka. jeptoo a, aguyoh jn and saidi m (2013), improving carrot yield and quality through the use of bio-slurry manure, sustainable agricultural research. 2(1): 164-172. doi: 10.5539/sar.v2n1p164 nakandalage n and seneweera s (2018), micronutrients useefficiency of crop-plants under changing climate. in plant micronutrient use efficiency, m.a. hossain, t. kamiya, d.j. burritt, l.-s.p. tran and t. fujiwara, eds. (london: academic press), pp 209-224. palaniveloo k, amran ma, norhashim na, mohamad-fauzi n, peng-hui f, hui-wen l, kai-lin y, jiale l, chian-yee mg and jing-yi l (2020), food waste composting and microbial community structure profiling, processes. 8: 723. doi: org/10.3390/ pr8060723 partey st, thevathasan nv, zougmoré rb and preziosi rf (2018), improving maize production through nitrogen supply from tenrarely-used organic resources in ghana, agrofor syst. 92: 375-387. doi: 10.1007/ s10457-016-0035-8 pituello c, polese r, morari f and berti a (2016), outcomes from a long-term study on crop residue effects on plant yield and nitrogen use efficiency in contrasting soils, eur j agron. 77: 179-187. doi: 10.1016/j. eja.2015.11.027 somerville pd, farrell c, may pb and livesley sj (2020), biochar and compost equally improve urban soil physical and biological properties and tree growth, with no added benefit in combination, sci total environ. 706: 135-736. doi: 10.1016/j.scitotenv. 2019.135736 tan d, liu z, jiang l, luo j and li j (2017), long-term potash application and wheat straw return reduced soil potassium fixation and affected crop yields in north china, nutr cycl agroecosyst. doi: 10.1007/s10705 017-9843-0 wang w, sardans j, wang c, pan t, zeng c, lai d, bartrons m and peñuelas j (2017), straw application strategy to optimize nutrient release in a southeastern china rice cropland, agronomy. 7. doi: 10.3390/agronomy 7040084 xin x, qin s, zhang j, zhu a, yang w and zhang x (2017), yield, phosphorus use efficiency and balance response to substituting long-term chemical fertilizer use with organic manure in a wheat-maize system, field crop res. 208: 27-33. doi: 10.1016/j.fcr.2017.03.011 yang hs, xu mm, koide rt, liu q, dai yj, liu l and bian xm (2016), effects of ditch-buried straw return on water percolation, nitrogen leaching and crop yields in a rice-wheat rotation system, j sc. food agric. 96: 1141-1149. doi: 10.1002/jsfa.7196 zhang p, chen x, wei t, yang z, jia z, yang b, han q and ren x (2016), effects of straw incorporation on the soil nutrient contents, enzyme activities, and crop yield in a semiarid region of china, soil tillage res. 160: 65-72. doi: 10.1016/j.still.2016.02.006 zhang y, liu y, zhang g, guo x, sun z and li t (2018), the effects of rice straw and biochar applications on the microbial community in a soil with a history of continuous tomato planting history, agronomy. 8. doi: 10.3390/agronomy8050065 zhao fj, mcgrath sp and meharg aa (2010), arsenic as a food chain contaminant: mechanisms of plant uptake and metabolism and mitigation strategies, annu rev plant biol. 61: 535-559. doi: 10.1146/annurev-arplant-042809-112152 table vii. correlation between the treatments and nutrient statuses of post-harvest soils nutrition coefficient stand. error t stat p-value lower 95% upper 95% *av. nitrogen 2.4323 0.5879 4.1374 0.0017 1.1384 3.7262 av. phosphorus 0.4720 0.0719 6.5611 0.0000 0.3137 0.6304 #ex. potassium 0.0802 0.0116 6.9098 0.0000 0.0546 0.1057 av. sulphur 0.4750 0.1822 2.6076 0.0244 0.0741 0.8760 ex. calcium 0.3347 0.0526 6.3628 0.0001 0.2189 0.4504 ex. magnesium 0.1550 0.0188 8.2649 0.0000 0.1137 0.1962 *av. indicate available and #ex. indicate exchangeable. however, until now, the use of straw incorporation to increase crop yield is still a matter of argument since studies in different climates and soil types have led to inconclusive results (pituello et al. 2016). it has been reported that straw incorporation has significant valuable effects on crop yields and soil properties. for instance, straw incorporation can increase crop yields (yang et al. 2016), soil organic matter and other soil nutrients (zhang et al. 2018). straw return can also improve soil physical properties, such as by increasing hydraulic conductivity, decreasing bulk density, and enhancing aggregate formation (yang et al. 2016). vermicompost is a nourishing organic fertilizer having high amount of humus, nitrogen 2–3%, phosphorous 1.55–2.25%, potassium 1.85–2.25%, micronutrients, more beneficial for soil microbes like ‘nitrogen fixing bacteria’ and mycorrhizal fungi. vermicompost has been scientifically proved as miracle plant growth enhancer (guerrero, 2010). ansari and ismail (2012) reported that worms vermicompost contains 7.37 % nitrogen and 19.58% phosphorous as p2o5. microbial population of n2fixing bacteria and actinomycetes increases by the application of vermicompost. the amplified microbial activities improve the availability of soil phosphorous and nitrogen. vermicomposting is an aerobic, biological method and is proficient to convert eco-friendly hummus like organic substances (chanda et al. 2011). vermicompost stimulates to influence the microbial activity of soil, increases the availability of oxygen, maintains normal soil temperature, increases soil porosity and infiltration of water, improves nutrient content and increases growth, yield and quality of the plant (arora et al. 2011). rice hull and sawdust are also important agricultural amendments. growth and yield components of rice grown in saline soil were found to be increased significantly (p ≤ 0.05) by the application of rice hull, rice straw and sawdust alone and in combination (akter et al. 2018). the physico-chemical properties and nutrient status of post-harvest soils were also found to be influenced by the application of these amendments (akter and khan, 2019). composting is a low-cost natural way of recycling and stabilizing organic matter under thermophilic temperature that forms a pathogen-free substrate, beneficial to crops (gurtler et al. 2018; somerville et al. 2020). low-income farmers found it more advantageous to them. composting was found to be a promising practice that brought organic materials to a certain stage by narrowing down its c:n ratio where nutrients are easily accessible to plants (palaniveloo et al. 2020). partey et al. (2018) and dinesh et al. (2011), had consolidated that biomass needs to decompose for making n available to crops. thus, composting locally available organic amendments (oas) is essential for a healthy and sustainable agro-ecosystem in different climatic conditions. therefore, the objectives of the study were to evaluate the nutrient statuses of post-harvest soils and rice plants grown in aman season as influenced by the different rates of organic composts applied under field condition. materials and methods study site and experimental design in patuakhali a district of bangladesh, the field experiment was conducted in bilbilash of bauphal upazila (map i), which is located between 22°20ʹ00ʺn and 90°20ʹ00ʺe longitude within agro-ecological zone-13 named as ganges tidal floodplain. the climatic condition of this area is usually known as ‘tropical monsoon climate’. the area mainly enjoys three seasons such as rainy, dry and summer season. the experiment was carried out following completely randomized block design with the self-made organic composts, such as, rice hull compost (rhc), rice straw compost (rsc), sawdust compost (sdc) and vermicompost (v) corresponding to the rates of 0, 2, 4 and 8 t ha-1 of each organic compost at aman season during august to december, 2018. there were 13 plots having individual treatment (table i) in the experimental area, each unit plot size was 16 m2 (4m×4m) and replications were considered within the plot. selected properties of potential amendments used and initial soils at field site are presented in the tables ii and iii. transplantation following subsequent protocols basal doses of n, p2o5, and k2o from urea, tsp, and mop fertilizers were applied at the rates of 40, 30, and 15 kg ha-1, respectively considering soil amendments and initial contents of the nutrients. during field preparation, the tsp, mop, and half of the urea were applied in their entirety after being thoroughly mixed with the field soil. the remaining urea was top dressed in two splits, one at the beginning of the rice panicle and another at the active tillering stage. three seedlings per hill of the br 25 variety, which were thirty days old and in good health, were transplanted. row to row and hill to hill distances were each 20 and 22 cm, respectively. no irrigation was required for this study for the growth of rice in this season. intercultural operations such as, weeding, pesticide use, etc. were done as per requirement. sample collection and analyses plant samples were collected from each plot just after harvesting. soil samples were collected from 3 spots as replications of each plot of active root zone (0-15 cm) with the help of an auger. soil samples were then stored treatment wise in polythene bags with proper labeling. after sun drying and grounding the samples were then passed through 2 mm sieve and stored properly in air tight plastic pots for further analyses. the collected plant samples were sun dried and weighed. after sun drying a portion of the collected plant samples were oven dried at 65⁰c and then grinded and stored in air tight plastic pots for laboratory analyses. all the laboratory analyses were done following standard methods. statistical analyses pearson correlation and regression analyses between treatments and mineral nutrition of rice plants, analysis of variance (anova) and tukey’s range test at 5% (p≤ 0.05) level were done for the interpretation of the experimental results. results and discussion mineral nutrition of rice plants the total nitrogen, phosphorus, potassium, sulfur, calcium and magnesium contents at maturity stage of rice plants grown under field condition were significantly (p≤0.05) influenced by the application of variable indigenous organic amendments (rice hull compost, rice straw compost, sawdust compost and vermicompost) during aman season (table iv and fig.1). pearson correlation and regression analyses have been performed between the different treatments and mineral nutrition of rice plant tissues (table v). significance has been determined based on p values whether they were <0.05 or not. the total nitrogen (r = 0.78***), phosphorus (r = 0.77**), potassium (r = 0.75**), sulfur (r = 0.82***), calcium (r = 0.82***) and magnesium (r = 0.60*) contents of the tested rice plant (br 25) tissues were significantly correlated with the applied organic composts and these correlations confirmed that the different sources of organic materials positively influenced the nutrition of rice plant tissues which ultimately regulate the edible part (grain) of the rice crops. according to graham et al. (2012), people taking cereal based diets still suffering from hidden hunger of nutrients due to low level and low bioavailability of essential elements. the present results demonstrated that the nitrogen content in rice straw increased with the increased rate of the application of organic composts. the maximum nitrogen contents in the rice plant tissues were recorded at v8 treatment for the tested variety. among the applied composts, vermicompost (18.63 g kg-1n) ranked first followed by rice straw compost (17.40 g kg-1), sawdust compost (14.57g kg-1) and rice hull compost (13.33 g kg-1), regardless of their doses. phosphorus contents in rice plant tissues increased with the higher rates of the different composts. the highest (4.42 g kg-1) and lowest (1.10 g kg-1) contents of total phosphorus were recorded in the t12 (v8) and t0 (control) treatments. the rest of the above-mentioned nutrients were exerted the similar trends as those obtained by the p and n contents by the different organic composts. the nutrition of rice shoots was influenced by the direction of vermicompost > rice straw compost > sawdust compost > rice hull compost for the studied variety of rice grown under field condition. nutrient status of post-harvest soils rice production during t. aman season, the available n contents in the post-harvest soils increased significantly (p ≤ 0.05) by the application of vermicompost, rice hull compost, rice straw compost and sawdust compost (table vi and fig. 2). the maximum amount of available n (78.29 mg kg-1) was recorded in t3 (rhc8) treatment, where available nitrogen content increased 85.65% as compared to control plot. at the same dose (8 t ha-1), the sawdust compost treatment ranked second for the available nitrogen content (62.31 mg kg-1) at post-harvest soils followed by rsc8 treatment (60.76 mg kg-1). there were significant (p≤0.05) increase in available phosphorus and sulfur, exchangeable potassium, calcium and magnesium at post-harvest soils with the increased doses of the organic amendments under rice production (table vi). soils treated with vermicompost at the rate of 8 t ha-1 was found to have significantly more phosphorus (12.57 mg kg-1) as compared to control plot. the rice straw compost and sawdust compost each at 8 t ha-1 were showed almost similar trends in the increment of available phosphorus contents in post-harvest soils followed by rice hull compost. the other nutrients of post-harvest soils followed the similar trends as that of phosphorus, except for the exchangeable potassium, where rice straw compost at the highest rate (8 t ha-1) exhibited the best response (0.97 c molc kg -1) than those of the other treatments. the maximum amounts of available sulfur, exchangeable calcium and magnesium were obtained from the highest dose of vermicompost and the minimum amounts were attained by the control plot. the trend of increments of all these nutrients were more pronounced with the higher rates of the applied organic amendments indicate that all the applied organic composts are suitable sources for improving nutrient statuses of soils. pearson correlation and regression analyses also indicate the strong positive relationship between the treatments and nutrient statuses of post-harvest soils (table vii). the current findings are in consistent with those of xin et al. (2017). many steps have been made to improve soil fertility and productivity, according to them. increased organic input, such as organic manure, compost, and straw integration, are the most effective approaches. crop straw, a cheap and nutrient-dense material, offers a lot of potential for enhancing soil fertility (tan et al. 2017). crop straw, which is high in nutrients and organic elements, can be treated as a natural organic fertilizer and utilized as an alternative to chemical fertilizers, according to the studies of wang et al. (2017). as a result, straw integration appears to be a potential method for maintaining and restoring soil fertility, the burning issue of present day. because, mineral elements are required for the healthy growth and development of both plants and humans. the plant roots take up the mineral nutrients from soil and transported them to the edible parts for human consumption through various transporters. for human health, an ideal future crop should be rich in essential mineral elements but with less toxic elements in the edible parts. still, it is estimated that nearly 2 billion people are suffering from deficiency of nutrients because of low availability of mineral elements in soil and/or low accumulation/bioavailability of mineral elements in edible parts (graham et al. 2012). this so-called hidden hunger is an especially serious health problem for people subsisting on cereal-based diets because cereals such as rice usually contain a low level of mineral elements as well as low bioavailability (grebmer et al. 2014; nakandalage and seneweera, 2018). on the other hand, rapid urbanization and industrialization cause contamination by toxic elements in many soils used for crop production (zhao et al. 2010; clemens and ma, 2016), which threaten our health throughout the food chain. therefore, it is extremely important to boost essential nutrients (both density and bioavailability) and reduce toxic elements in edible parts of cereals for human health. conclusion the present research findings conclude that the locally made organic composts using indigenous organic materials had potential to improve soil fertility and provide nutrients for rice production. significant positive correlation between the treatments and mineral nutrients of rice plants confirmed the strong relationship of organic farming for sustainable agriculture. there were significant (p ≤ 0.05) increase in available phosphorus and sulfur, exchangeable potassium, calcium and magnesium at post-harvest soils with the increased doses of amendments under rice production. the nutrition of rice plants grown under field condition was influenced most by the vermicompost and followed the order of the treatments as rice straw compost > sawdust compost > rice hull compost for the studied variety of rice. these results resemble that the further researches are needed to find out the suitable doses and types of the amendments. however, the applied organic fertilizers were found to have responses on the nutritional statuses of rice shoot and post-harvest soils and these might be effective for the nutritional balance of the rice variety and ultimately will be helpful for country’s penniless people to combat their existing and future demand of quality rice. acknowledgement the study was carried out under a project of the climate change trust fund (cctf) titled ‘assessment of impacts of climate change on soil health and food security, and adaptation of climate-smart agriculture in most adversely affected areas of bangladesh’ through the moefcc, government of the peoples’ republic of bangladesh. the project was implemented in two phases (phase i: jan.’17 to dec.’18, code 410 duand phase ii: jan.’19 to dec.’22, code 573 du) within six years. we are also grateful to the project staff and relevant officers/staff of the swed-du, du, moe and moefcc of gob, who performed for the successful completion of the study. references ahmed s, alam mj, hossain a, islam ak, awan th, soufan w, qahtan aa, okla mk and sabagh si (2021), interactive effect of weeding regimes, rice cultivars, and seeding rates influence the rice-weed competition under dry direct-seeded condition, sustainability. 13: 317-321. doi: 10.3390/su13010317 akter s and khan hr (2019), influence of rice hull, rice straw, sawdust and moisture levels on selected properties of post harvested saline soils under variable conditions of rice cultivation, national university journal of science. 6(1): 61-74. akter s, khan hr, hossain ms, saha mk and farzana f (2018), response of rice grown in saline soil as influenced by the application of agricultural amendments and moisture regimes, j biodivers conserv bioresour manag. 4(2): 33-42. doi: https://doi.org/ 10.3329/jbcbm.v4i2.39845 ansari aa and ismail sa (2012), role of earthworms in vermtechnology, j agric technol. 8(2): 405-415. https://www.ijat-aatsea.com arora vk, singh cb, sidhu as and thind ss (2011), irrigation, tillage and mulching effects on soybean yield and water productivity in relation to soil texture, agric water manag. 98(4): 563-568. https://doi.org/10.1016/j.agwat .2010.10.004 bbs (2017), bangladesh bureau of statistics. the year book of agricultural statistics of bangladesh. stat. div. minis. planning, govt. peoples repub. bangladesh, dhaka. bbs (2020), summary crop statistics and crop indices (2019-2020). bangladesh bureau of statistics division, govt. of the people’s republic of bangladesh: dhaka, bangladesh. pp 35-37. chanda gc, bhunia g and chakraborty sk (2011), the effect of vermicompost and other fertilizers on cultivation of tomato plants, j hortic for. 3: 42-45. http://www.acade mic journals.org/jhf clemens s and ma jf (2016), toxic heavy metal and metalloid accumulation in crop plants and foods, annu rev plant biol. 67: 489-512. doi: 10.1146/annurev-arplant-043015-112301 dinesh r, suryanarayana ma, nair ak and chaudhuri sg (2011), leguminous cover crop effects on nitrogen mineralization rates and kinetics in soils, j agron crop sci. 187: 161-166. doi: 10.1046/j.1439-037x. 2001. 00512.x frg (2012), (fertilizer recommendation guide). bangladesh agricultural research council (barc), dhaka, bangladesh. graham rd, knez m and welch rm (2012), how much nutritional iron deficiency in humans globally is due to an underlying zinc deficiency, adv agron. 1-40. doi: 10.1016/b978-0-12-394276-0.00001-9 grebmer bkv, saltzman a, birol e, wiesmann d, prasai n, yins, yohannes y, menon p, thompson j and sonntag a (2014), 2014 global hunger index: the challenge of hidden hunger (washington, dc: international food policy research institute), pp 56. doi: http://dx.doi.org/10.2499/9780896299580 guerrero rd (2010), vermicompost production and its use for crop production in the philippines, international journal of global environmental issues. 10(3/4): 378-383. doi: 10.1504/ijgenvi.2010.037278 gurtler jb, doyle mp, erickson mc, jiang x, millner p and sharma m (2018), composting to inactivate food borne pathogens for crop soil application, a review j food prot.81: 1821-1837. doi: 10.4315/0362-028x.jfp-18-217 heitkamp f, raupp j and ludwig b (2011), soil organic matter pools and crop yields as affected by the rate of farmyard manure and use of biodynamic preparations in a sandy soil, organic agriculture. 11: 111-124. doi: 10.1007/s13165-011-0010-7 jahiruddin m and satter ma (2010), research priority in agriculture and development of vision document-2030 and beyond. land and soil resource management. bangladesh gricultural research council. dhaka. jeptoo a, aguyoh jn and saidi m (2013), improving carrot yield and quality through the use of bio-slurry manure, sustainable agricultural research. 2(1): 164-172. doi: 10.5539/sar.v2n1p164 nakandalage n and seneweera s (2018), micronutrients useefficiency of crop-plants under changing climate. in plant micronutrient use efficiency, m.a. hossain, t. kamiya, d.j. burritt, l.-s.p. tran and t. fujiwara, eds. (london: academic press), pp 209-224. palaniveloo k, amran ma, norhashim na, mohamad-fauzi n, peng-hui f, hui-wen l, kai-lin y, jiale l, chian-yee mg and jing-yi l (2020), food waste composting and microbial community structure profiling, processes. 8: 723. doi: org/10.3390/ pr8060723 partey st, thevathasan nv, zougmoré rb and preziosi rf (2018), improving maize production through nitrogen supply from tenrarely-used organic resources in ghana, agrofor syst. 92: 375-387. doi: 10.1007/ s10457-016-0035-8 pituello c, polese r, morari f and berti a (2016), outcomes from a long-term study on crop residue effects on plant yield and nitrogen use efficiency in contrasting soils, eur j agron. 77: 179-187. doi: 10.1016/j. eja.2015.11.027 somerville pd, farrell c, may pb and livesley sj (2020), biochar and compost equally improve urban soil physical and biological properties and tree growth, with no added benefit in combination, sci total environ. 706: 135-736. doi: 10.1016/j.scitotenv. 2019.135736 tan d, liu z, jiang l, luo j and li j (2017), long-term potash application and wheat straw return reduced soil potassium fixation and affected crop yields in north china, nutr cycl agroecosyst. doi: 10.1007/s10705 017-9843-0 wang w, sardans j, wang c, pan t, zeng c, lai d, bartrons m and peñuelas j (2017), straw application strategy to optimize nutrient release in a southeastern china rice cropland, agronomy. 7. doi: 10.3390/agronomy 7040084 xin x, qin s, zhang j, zhu a, yang w and zhang x (2017), yield, phosphorus use efficiency and balance response to substituting long-term chemical fertilizer use with organic manure in a wheat-maize system, field crop res. 208: 27-33. doi: 10.1016/j.fcr.2017.03.011 yang hs, xu mm, koide rt, liu q, dai yj, liu l and bian xm (2016), effects of ditch-buried straw return on water percolation, nitrogen leaching and crop yields in a rice-wheat rotation system, j sc. food agric. 96: 1141-1149. doi: 10.1002/jsfa.7196 zhang p, chen x, wei t, yang z, jia z, yang b, han q and ren x (2016), effects of straw incorporation on the soil nutrient contents, enzyme activities, and crop yield in a semiarid region of china, soil tillage res. 160: 65-72. doi: 10.1016/j.still.2016.02.006 zhang y, liu y, zhang g, guo x, sun z and li t (2018), the effects of rice straw and biochar applications on the microbial community in a soil with a history of continuous tomato planting history, agronomy. 8. doi: 10.3390/agronomy8050065 zhao fj, mcgrath sp and meharg aa (2010), arsenic as a food chain contaminant: mechanisms of plant uptake and metabolism and mitigation strategies, annu rev plant biol. 61: 535-559. doi: 10.1146/annurev-arplant-042809-112152 hasan, satter and ahmed 105 however, until now, the use of straw incorporation to increase crop yield is still a matter of argument since studies in different climates and soil types have led to inconclusive results (pituello et al. 2016). it has been reported that straw incorporation has significant valuable effects on crop yields and soil properties. for instance, straw incorporation can increase crop yields (yang et al. 2016), soil organic matter and other soil nutrients (zhang et al. 2018). straw return can also improve soil physical properties, such as by increasing hydraulic conductivity, decreasing bulk density, and enhancing aggregate formation (yang et al. 2016). vermicompost is a nourishing organic fertilizer having high amount of humus, nitrogen 2–3%, phosphorous 1.55–2.25%, potassium 1.85–2.25%, micronutrients, more beneficial for soil microbes like ‘nitrogen fixing bacteria’ and mycorrhizal fungi. vermicompost has been scientifically proved as miracle plant growth enhancer (guerrero, 2010). ansari and ismail (2012) reported that worms vermicompost contains 7.37 % nitrogen and 19.58% phosphorous as p2o5. microbial population of n2fixing bacteria and actinomycetes increases by the application of vermicompost. the amplified microbial activities improve the availability of soil phosphorous and nitrogen. vermicomposting is an aerobic, biological method and is proficient to convert eco-friendly hummus like organic substances (chanda et al. 2011). vermicompost stimulates to influence the microbial activity of soil, increases the availability of oxygen, maintains normal soil temperature, increases soil porosity and infiltration of water, improves nutrient content and increases growth, yield and quality of the plant (arora et al. 2011). rice hull and sawdust are also important agricultural amendments. growth and yield components of rice grown in saline soil were found to be increased significantly (p ≤ 0.05) by the application of rice hull, rice straw and sawdust alone and in combination (akter et al. 2018). the physico-chemical properties and nutrient status of post-harvest soils were also found to be influenced by the application of these amendments (akter and khan, 2019). composting is a low-cost natural way of recycling and stabilizing organic matter under thermophilic temperature that forms a pathogen-free substrate, beneficial to crops (gurtler et al. 2018; somerville et al. 2020). low-income farmers found it more advantageous to them. composting was found to be a promising practice that brought organic materials to a certain stage by narrowing down its c:n ratio where nutrients are easily accessible to plants (palaniveloo et al. 2020). partey et al. (2018) and dinesh et al. (2011), had consolidated that biomass needs to decompose for making n available to crops. thus, composting locally available organic amendments (oas) is essential for a healthy and sustainable agro-ecosystem in different climatic conditions. therefore, the objectives of the study were to evaluate the nutrient statuses of post-harvest soils and rice plants grown in aman season as influenced by the different rates of organic composts applied under field condition. materials and methods study site and experimental design in patuakhali a district of bangladesh, the field experiment was conducted in bilbilash of bauphal upazila (map i), which is located between 22°20ʹ00ʺn and 90°20ʹ00ʺe longitude within agro-ecological zone-13 named as ganges tidal floodplain. the climatic condition of this area is usually known as ‘tropical monsoon climate’. the area mainly enjoys three seasons such as rainy, dry and summer season. the experiment was carried out following completely randomized block design with the self-made organic composts, such as, rice hull compost (rhc), rice straw compost (rsc), sawdust compost (sdc) and vermicompost (v) corresponding to the rates of 0, 2, 4 and 8 t ha-1 of each organic compost at aman season during august to december, 2018. there were 13 plots having individual treatment (table i) in the experimental area, each unit plot size was 16 m2 (4m×4m) and replications were considered within the plot. selected properties of potential amendments used and initial soils at field site are presented in the tables ii and iii. transplantation following subsequent protocols basal doses of n, p2o5, and k2o from urea, tsp, and mop fertilizers were applied at the rates of 40, 30, and 15 kg ha-1, respectively considering soil amendments and initial contents of the nutrients. during field preparation, the tsp, mop, and half of the urea were applied in their entirety after being thoroughly mixed with the field soil. the remaining urea was top dressed in two splits, one at the beginning of the rice panicle and another at the active tillering stage. three seedlings per hill of the br 25 variety, which were thirty days old and in good health, were transplanted. row to row and hill to hill distances were each 20 and 22 cm, respectively. no irrigation was required for this study for the growth of rice in this season. intercultural operations such as, weeding, pesticide use, etc. were done as per requirement. sample collection and analyses plant samples were collected from each plot just after harvesting. soil samples were collected from 3 spots as replications of each plot of active root zone (0-15 cm) with the help of an auger. soil samples were then stored treatment wise in polythene bags with proper labeling. after sun drying and grounding the samples were then passed through 2 mm sieve and stored properly in air tight plastic pots for further analyses. the collected plant samples were sun dried and weighed. after sun drying a portion of the collected plant samples were oven dried at 65⁰c and then grinded and stored in air tight plastic pots for laboratory analyses. all the laboratory analyses were done following standard methods. statistical analyses pearson correlation and regression analyses between treatments and mineral nutrition of rice plants, analysis of variance (anova) and tukey’s range test at 5% (p≤ 0.05) level were done for the interpretation of the experimental results. results and discussion mineral nutrition of rice plants the total nitrogen, phosphorus, potassium, sulfur, calcium and magnesium contents at maturity stage of rice plants grown under field condition were significantly (p≤0.05) influenced by the application of variable indigenous organic amendments (rice hull compost, rice straw compost, sawdust compost and vermicompost) during aman season (table iv and fig.1). pearson correlation and regression analyses have been performed between the different treatments and mineral nutrition of rice plant tissues (table v). significance has been determined based on p values whether they were <0.05 or not. the total nitrogen (r = 0.78***), phosphorus (r = 0.77**), potassium (r = 0.75**), sulfur (r = 0.82***), calcium (r = 0.82***) and magnesium (r = 0.60*) contents of the tested rice plant (br 25) tissues were significantly correlated with the applied organic composts and these correlations confirmed that the different sources of organic materials positively influenced the nutrition of rice plant tissues which ultimately regulate the edible part (grain) of the rice crops. according to graham et al. (2012), people taking cereal based diets still suffering from hidden hunger of nutrients due to low level and low bioavailability of essential elements. the present results demonstrated that the nitrogen content in rice straw increased with the increased rate of the application of organic composts. the maximum nitrogen contents in the rice plant tissues were recorded at v8 treatment for the tested variety. among the applied composts, vermicompost (18.63 g kg-1n) ranked first followed by rice straw compost (17.40 g kg-1), sawdust compost (14.57g kg-1) and rice hull compost (13.33 g kg-1), regardless of their doses. phosphorus contents in rice plant tissues increased with the higher rates of the different composts. the highest (4.42 g kg-1) and lowest (1.10 g kg-1) contents of total phosphorus were recorded in the t12 (v8) and t0 (control) treatments. the rest of the above-mentioned nutrients were exerted the similar trends as those obtained by the p and n contents by the different organic composts. the nutrition of rice shoots was influenced by the direction of vermicompost > rice straw compost > sawdust compost > rice hull compost for the studied variety of rice grown under field condition. nutrient status of post-harvest soils rice production during t. aman season, the available n contents in the post-harvest soils increased significantly (p ≤ 0.05) by the application of vermicompost, rice hull compost, rice straw compost and sawdust compost (table vi and fig. 2). the maximum amount of available n (78.29 mg kg-1) was recorded in t3 (rhc8) treatment, where available nitrogen content increased 85.65% as compared to control plot. at the same dose (8 t ha-1), the sawdust compost treatment ranked second for the available nitrogen content (62.31 mg kg-1) at post-harvest soils followed by rsc8 treatment (60.76 mg kg-1). there were significant (p≤0.05) increase in available phosphorus and sulfur, exchangeable potassium, calcium and magnesium at post-harvest soils with the increased doses of the organic amendments under rice production (table vi). soils treated with vermicompost at the rate of 8 t ha-1 was found to have significantly more phosphorus (12.57 mg kg-1) as compared to control plot. the rice straw compost and sawdust compost each at 8 t ha-1 were showed almost similar trends in the increment of available phosphorus contents in post-harvest soils followed by rice hull compost. the other nutrients of post-harvest soils followed the similar trends as that of phosphorus, except for the exchangeable potassium, where rice straw compost at the highest rate (8 t ha-1) exhibited the best response (0.97 c molc kg -1) than those of the other treatments. the maximum amounts of available sulfur, exchangeable calcium and magnesium were obtained from the highest dose of vermicompost and the minimum amounts were attained by the control plot. the trend of increments of all these nutrients were more pronounced with the higher rates of the applied organic amendments indicate that all the applied organic composts are suitable sources for improving nutrient statuses of soils. pearson correlation and regression analyses also indicate the strong positive relationship between the treatments and nutrient statuses of post-harvest soils (table vii). the current findings are in consistent with those of xin et al. (2017). many steps have been made to improve soil fertility and productivity, according to them. increased organic input, such as organic manure, compost, and straw integration, are the most effective approaches. crop straw, a cheap and nutrient-dense material, offers a lot of potential for enhancing soil fertility (tan et al. 2017). crop straw, which is high in nutrients and organic elements, can be treated as a natural organic fertilizer and utilized as an alternative to chemical fertilizers, according to the studies of wang et al. (2017). as a result, straw integration appears to be a potential method for maintaining and restoring soil fertility, the burning issue of present day. because, mineral elements are required for the healthy growth and development of both plants and humans. the plant roots take up the mineral nutrients from soil and transported them to the edible parts for human consumption through various transporters. for human health, an ideal future crop should be rich in essential mineral elements but with less toxic elements in the edible parts. still, it is estimated that nearly 2 billion people are suffering from deficiency of nutrients because of low availability of mineral elements in soil and/or low accumulation/bioavailability of mineral elements in edible parts (graham et al. 2012). this so-called hidden hunger is an especially serious health problem for people subsisting on cereal-based diets because cereals such as rice usually contain a low level of mineral elements as well as low bioavailability (grebmer et al. 2014; nakandalage and seneweera, 2018). on the other hand, rapid urbanization and industrialization cause contamination by toxic elements in many soils used for crop production (zhao et al. 2010; clemens and ma, 2016), which threaten our health throughout the food chain. therefore, it is extremely important to boost essential nutrients (both density and bioavailability) and reduce toxic elements in edible parts of cereals for human health. conclusion the present research findings conclude that the locally made organic composts using indigenous organic materials had potential to improve soil fertility and provide nutrients for rice production. significant positive correlation between the treatments and mineral nutrients of rice plants confirmed the strong relationship of organic farming for sustainable agriculture. there were significant (p ≤ 0.05) increase in available phosphorus and sulfur, exchangeable potassium, calcium and magnesium at post-harvest soils with the increased doses of amendments under rice production. the nutrition of rice plants grown under field condition was influenced most by the vermicompost and followed the order of the treatments as rice straw compost > sawdust compost > rice hull compost for the studied variety of rice. these results resemble that the further researches are needed to find out the suitable doses and types of the amendments. however, the applied organic fertilizers were found to have responses on the nutritional statuses of rice shoot and post-harvest soils and these might be effective for the nutritional balance of the rice variety and ultimately will be helpful for country’s penniless people to combat their existing and future demand of quality rice. acknowledgement the study was carried out under a project of the climate change trust fund (cctf) titled ‘assessment of impacts of climate change on soil health and food security, and adaptation of climate-smart agriculture in most adversely affected areas of bangladesh’ through the moefcc, government of the peoples’ republic of bangladesh. the project was implemented in two phases (phase i: jan.’17 to dec.’18, code 410 duand phase ii: jan.’19 to dec.’22, code 573 du) within six years. we are also grateful to the project staff and relevant officers/staff of the swed-du, du, moe and moefcc of gob, who performed for the successful completion of the study. references ahmed s, alam mj, hossain a, islam ak, awan th, soufan w, qahtan aa, okla mk and sabagh si (2021), interactive effect of weeding regimes, rice cultivars, and seeding rates influence the rice-weed competition under dry direct-seeded condition, sustainability. 13: 317-321. doi: 10.3390/su13010317 akter s and khan hr (2019), influence of rice hull, rice straw, sawdust and moisture levels on selected properties of post harvested saline soils under variable conditions of rice cultivation, national university journal of science. 6(1): 61-74. akter s, khan hr, hossain 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z, jia z, yang b, han q and ren x (2016), effects of straw incorporation on the soil nutrient contents, enzyme activities, and crop yield in a semiarid region of china, soil tillage res. 160: 65-72. doi: 10.1016/j.still.2016.02.006 zhang y, liu y, zhang g, guo x, sun z and li t (2018), the effects of rice straw and biochar applications on the microbial community in a soil with a history of continuous tomato planting history, agronomy. 8. doi: 10.3390/agronomy8050065 zhao fj, mcgrath sp and meharg aa (2010), arsenic as a food chain contaminant: mechanisms of plant uptake and metabolism and mitigation strategies, annu rev plant biol. 61: 535-559. doi: 10.1146/annurev-arplant-042809-112152 mineral nutrition of rice and post-harvest soils influenced by self-made organic composts 58(2) 2023106 35 biodiesel from moringa stenopetala seed oil g. y. shage1* and a. y. ali2 1forest products innovation center, ethiopian forest development, p.o. box: 2322, addis ababa, ethiopia 2process engineering division, school of chemical and bioengineering, addis ababa institute of technology, addis ababa university, p.o. box: 385, addis ababa, ethiopia abstract the aim of this paper is the production and characterization of biodiesel from moringa stenopetala seed oil. biodiesel is a renewable, biodegradable, and nontoxic biofuel. moringa stenopetala seed oil is a potential feedstock that has not been discovered as an energy source. this study investigated the effects of process parameters: methanol to oil ratio, reaction temperature, and catalyst loading on the yield and quality of biodiesel. the experimental results showed that the maximum biodiesel yield was 94% and it was obtained at optimum process conditions: temperature 55°c, methanol to oil ratio 6:1, and catalyst loading1.0. biodiesel product was characterized based on international standards for testing fuels. according to the findings of the study, moringa stenopetala seed oil biodiesel has a specific gravity of 0.874 g/mole, a kinematic viscosity of 4.8 mm2/s, an acid value of 0.4 mg koh/g, a saponification value of 196 mg koh/g, ffa 0.2%, iodine value 104.5 high heating value 10,287 cal/g, flash point 184°c, pour point 1°c, cloud point 10°c and cetane number 53. these results satisfy international standards for biodiesel. keywords: biodiesel; biomass; characterization; production; moringa stenopetala *corresponding author e-mail: gemechyade@gmail.com available online at www.banglajol.info bangladesh j. sci. ind. res. 58(1), 35-44, 2023 introduction energy plays a crucial role in the socio-economic development of any country. the demand for energy sources has increased rapidly with the growing population in the world. nowadays, the world is highly dependent on non-renewable fuelsas an energy source. the current concerns such as high global warming, depletion of fossil fuels, and fluctuating price of conventional diesel fuels have pushed researchers toward finding new alternative, clean, renewable, and sustainable energy resourcessuch as solar, hydroelectric, wind, and biomass-derived fuels (kafuku, g. and mbarawa, 2010). currently, fossil fuel is the dominant source of energy in the world though it is not renewable and has a high impact on global climate. the rapid increase in global energy demand, the depleting petroleum fuels, global climate change, the increasing price of fossil fuels, urbanization, and the increasing population has driven the search for renewable energy sources which are clean, sustainable, and environmentally friendly (atabani et al. 2013). biodiesel is a chain of mono-alkyl esters produced by the transesterification of vegetable oil and animal fats (demshemino et al. 2013). biodiesel is a promising biofuel that is renewable, biodegradable, and non-toxic. biodiesel is gaining importance as one of the most important substitutes for depleting fossil fuels. there are many advantages of using biodiesel as an alternative form of energy. it can be used as such in the diesel engine without any engine modification indicating that it has similar physical and chemical properties as conventional diesel fuel. the combustion properties of biodiesel are also very close to those of petroleum diesel (sreepada and vijayalaxmi, 2013). the most common production technology of biodiesel is the transesterification process. transesterification is a chemical reaction between one mole of triglyceride with three moles of alcohol to produce fatty acid methyl ester and glycerol in the presence of a catalyst or without a catalyst. most transesterification reactions use ethanol or methanol alcohol. many studies show that methanol is more practically used as alcohol than ethanol. methanol is preferable due to its low cost and its physical and chemical advantages. another advantage of using methanol is the ease of separation of glycerin which can be achieved by simple decantation (marchetti and yadessa, 2012). various catalysts can be used in the process. however, it was confirmed that the transesterification reaction was completed very fast when alkali catalysts are used. after the transesterification reaction is completed, glycerol, catalyst, alcohol, and soap are separated from biodiesel. the factors affecting biodiesel yield and fuel quality are alcohol-to-oil ratios, temperature, catalyst loading, and reaction time (raj and bhandari, 2017). biodiesel is formed when triglyceride reacts with alcohol leaving glycerol as a byproduct as shown in figure 1. there are more than 300 vegetable oils identified as potential feedstocks for biodiesel production globally. the availability, characteristics, and variety of feedstocks make them promising ingredients for the sustainable production of biodiesel (piyush et al. 2013). researchers have proposed moringa seed oil as an alternative potential feedstock to produce biodiesel. however, there is a research gap that promotes this feedstock for industrial processing. moringa seed has an average of 35%-45% oil content with high oleic content of greater than 73% based on the type of the tree. moringa oil has many various industrial and homemade benefits. one of oil by rotary evaporation at 80°c. gum and wax were removed by a degumming method. then, biodiesel was synthesized by transesterification reaction using a homogenous catalyst (methanol) at different process parameters. experimental design the experimental design used for this study was a box behnken design standard using design expert 11.0 software. the experimental design was done using three variables and tree levels for a response surface method. 17 experimental runswere selected by design expert 11.0 software using the box behnken design standard method, with five central points per block. the main factors that affect biodiesel production by transesterification reaction are reaction time, reaction temperature, and alcohol-to-oil ratio (seema and meena, 2017). as indicated in table i, the overall production of biodiesel was carried out at optimum parameters of catalyst load of 0.5 to 1.5 wt.%, reaction temperature of 45 to 65°c, and methanol to oil ratio of 3 to 9. the other parameters, reaction time and mixing intensity were kept constant at 1 hour and 500 rpm for all experimental runs. a combination of three factors and three levels of experimental runs was conducted. there are 17 experimental runs determined bybox behnken’s design arrangement as shown in table ii. production and purification of the product the method used to produce biodiesel was a one-steptransesterification reaction. methanol was the alcohol selected for the transesterification reaction due to its availability, low cost, popularity, and ease of separation (demirbas, 2005). the catalyst selected for this study was the base catalyst (koh) since biodiesel can be produced at low temperatures and pressure reactions. moreover, it is a homogeneous base catalyst that results in high conversion, minimum side reactions, short reaction time, and high yield (marchetti and yadessa, 2012). though it has many advantages, the disadvantage of the catalyst used is it cannot be reused. when the reaction is completed, biodiesel and glycerol were separated by a separatory funnel after it settles for 24 hours. then, biodiesel was washed with hot distilled water to remove soap, remaining methanol, and wax. optimization of the process parameters using the response surface method (rsm). optimization aims to determine the optimum value of the factors that affect the transesterification process to produce the maximum possible biodiesel yield at a minimum production cost. this is done by minimizing the methanol to oil ratio, reaction temperature, and amount of catalyst used as indicated in table iii. characterization of biodiesel characterization of fuel is determining the physical and chemical properties (atabani et al. 2013). the physical and chemical properties of biodiesel were determined according to the american society for testing materials (astm d 6751) and european standard (en 14214) methods (demirbas, 2005). table iv showed the physical and chemical properties of biodiesel and the standard methods used to determine them. statistical analysis of experimental results data analysis of the experiment was done by design expert 11.0 software using box behnken design standard. the significance of experimental variables was obtained from analysis of variance (anova). results and discussions yield the maximum oil yield obtained at optimum conditions of temperature 80°c and extraction time 5 hours was 39.86 %. this result agreed with the average oil content of moringa stenopetala seed oil which is 35% 45% (ayerza, 2012), and this result also agreed with the previous reportof 38% which was reported by azad et al. (2015) and by gemechu (2021). the maximum yield of biodiesel was 94% and it was obtained at optimum process parameters of methanol to oil ratio 6:1, temperature 55°c, and catalyst loading 1.0%. the yield of biodiesel obtained agrees with the previous report of azad et al. (2015) which was 91%. the yield increased as transesterification parameters increased until the optimum value and decreased beyond the optimum value. at the lower value of parameters, the yield decreased due to the incomplete conversion of reactants to the product. table v showed the yield response of all experimental runs. characterization of biodiesel physical and chemical properties of biodiesel were evaluated using standard methods and the results were compared with astm and en standard methods and previous reports. density the value of the density of biodiesel was 874 kg/m3. this result is within the standard range of density (860 – 900 kg/m3) (demirbas, 2005) and agrees with the previous report by kafuku and mbarawa (2010) which was 900 kg/m3. higher density increases thesize of fuel droplets and causes higher emission of particulate matter and nox emission ina diesel engine while the lower density of fuel expands the efficiency of atomization (choi and reitz, 1999). kinematic viscosity the experimental result showed that the value of kinematic viscosity was 4.8 mm2/s. this result is within the range of the astm standard value of biodiesel which is 1.6-6 (eman and cadence, 2013; demirbas, 2005). highly viscous fuel is difficult to pump and operate in internal combustion engines while lower kinematic viscosity of fuels increases wear leakage due to insufficient lubrication (rao, 2011). acid value the value of an acid value obtained was 0.4 mm koh/g. this result agrees with the previous report (kafuku and mbarawa, 2010), with a value of 1.2 mmkoh/g. higher acid-value fuels need further acid treatment costs and it also lowers the quality of the fuels. in this study, the lower acid value of biodiesel indicates that it has higher fuel quality. calorific value the experimental result showed that the value of biodiesel was 10287 cal/ g or 43 mj/kj. this result agrees with the previous report of mahamudul et al. (2017) which was 39 mj/kg, and the previous report of agarwal and das (2001) which was 43.2 kj/kg. the result obtained is above the standard astm value which is 42-42.5 mj/kg. this result indicates the higher fuel quality of biodiesel. the calorific value obtained is similar to that of conventional diesel fuels. this is the novel result of this study. flash point the flash point obtained from the experimental result was 184°c. this result agrees with the standard astm value of biodiesel flash point which is greater than 130°c. from this study, the higher flash point of biodiesel indicates that it is safer to handle, store and transport the fuel (jayed et al. 2011). cetane number the value of the cetane number observed was 53. this result agrees with the standard astm value of the cetane number of biodiesel which is greater than 47 (demirbas, 2005). fuels with higher cetane number benefit the engine performance since the engine starts rapidly and run smoothly without causing much noise. cloud and pour point the experimental result showed that the cloud and pour points of biodiesel were 10°c and 1°c respectively. this result agrees with the previous report of kafuku and mbarawa (2010) which was 10°c and 3°c respectively. cloud and pour point of fuel indicates the fuel performance at low ambient temperature (agarwal and das, 2001). table vi showed the result of all main physicochemical properties of biodiesel synthesized. statistical analysis of experimental results analysis of variance (anova) for the quadratic model analysis of variance determines the significance of the experimental results using coded variables as indicated in table vii. the model f-value of 380.98 implies the model is significant. there is only a 0.01% chance that an f-value this large could occur due to noise. p-values less than 0.0500 indicate model terms are significant. in this case, a, b, c, a², b², c² are significant model terms. values greater than 0.1000 indicate the model terms are not significant. if there are many insignificant model terms (not counting those required to support hierarchy), model reduction may improve your model. the lack of fit f-value of 5.69 implies there is a 6.31% chance that a lack of fit f-value this large could occur due to noise. lack of fit is bad -we want the model to fit. this relatively low probability (<10%) is troubling. the coefficient estimate represents the expected change in response per unit change in factor value when all remaining factors are held constant. the intercept in an orthogonal design is the overall average response of all the runs. the coefficients are adjustments around that average based on the factor settings. when the factors are orthogonal the vifs are 1; vifs greater than 1 indicate multi-collinearity, and the higher the vif the more severe the correlation of factors. as a rough rule, vifs less than 10 are tolerable. the effect of process parameters on the yield of biodiesel effect of methanol to oil ratio figure. (2) shows the effect of methanol to oil ratio on biodiesel yield at constant temperature and catalyst loading. it showed that the yield of biodiesel increases as the methanol-to-oil ratio increases. increasing the methanol-to-oil ratio beyond the optimum value results in excess methanol which decreases the yield of biodiesel. the maximum yield of biodiesel (94%) was obtained at a methanol-to-oil ratio of 6: 1. therefore, this ratio was taken as an optimum value of the methanol-to-oil ratio. decreasing the methanol-to-oil ratio below the optimum value (3:1), decreased the conversion efficiency of the transesterification reaction and resulted in lower biodiesel yield. effect of reaction temperature figure (3) shows the effect of reaction temperature on the yield of biodiesel at a constant methanol-to-oil ratio and catalyst loading. the yield of biodiesel highly increased as temperature increased from 45°c to 55°c. maximum yield was obtained at 58°c and the yield started to decrease slightly from 58°c to 65°c due to the vaporization of methanol resulting in soap formation. the boiling point of methanol is 64.7°c. increasing reaction temperature above this point leads to methanol loss by evaporation and decreases the conversion efficiency of the reaction. at 45°c, the yield is about 75°c. effect of catalyst loading figure (4) shows the effect of catalyst loading on the yield of biodiesel at a constant methanol-to-oil ratio and temperature. as the amount of catalyst increased from 0.5% to 1.0%, the yield of biodiesel increased from 89% to 94% and the yield starts to decrease slightly as the amount of catalyst increased from 1.0% to 1.5% due to the formation of soap and emulsion. at a lower amount of catalyst (0.5%), the yield of biodiesel decreased due to the incomplete conversion of triglycerides of oil to fatty acid methyl ester. optimization of transesterification process parameters using the response surface method (rsm) the response surface method determined the optimum value of process variables that maximize the yield of the product and minimize production cost table viii showed that response surface method found 15 solutions and selected the optimum values to minimize the economic cost of temperature, methanol, and catalyst required for the reaction and to maximize the yield of biodiesel. the optimum yield of biodiesel (83.772%) was observed at a temperature of 51.537 and catalyst load of 0.500 wt.%. conclusions biodiesel is a promising biofuel that is synthesized by the transesterification of vegetable oils and animal fats. in this study, biodiesel was synthesized from moringa stenopetala seed oil using an alkali catalyst. the effect of methanol to oil ratio, reaction temperature, and catalyst weight on the yield and quality of biodiesel have been studied. biodiesel produced was characterized according to international fuel testing standards methods. the optimization of process parameters was carried out using response surface method (rsm). the experimental result showed that the highest yield of biodiesel was 94% and this result was obtained at an optimum value of temperature 55°c, methanol to oil ratio of 6:1, and catalyst load of 1.0%. increasing methanol to oil ratio, temperature, and catalyst load up to the optimum point increased the yield of biodiesel. however, further increase of the parameters above the optimum point decreased the yield of biodiesel. the temperature has the highest significant effect while the catalyst load has a lower effect. besides to characterization of different basic fuel properties of it, biodiesel can be blended with petrol-diesel at different percentages and applied in compression ignition engine to evaluate the effect of using a blend of biodiesel using different parameters such as engine power, brake thermal efficiency, specific fuel consumption, exhaust gas temperature, and greenhouse gas temperature and gas emission. however, the performance analysis of the blend of biodiesel with petrol diesel in a compression ignition engine was not done due to a lack of laboratory setup and equipment required to measure these parameters. this study did not compare biodiesel with diesel fuels used in diesel engines. moreover, it did not characterize the blend of biodiesel with petroleum fuels and did not compare biodiesel produced from other feedstocks other than moringa stenopetala. thus, further research should be done on these areas. generally, it can be concluded that moringa stenopetala is a promising alternative feedstock for biodiesel production for the reasons: it does not affect food security, has a good oil content, and can be harvested throughout the year. the biodiesel produced meets the standard fuel quality and international standard specifications. acknowledgment the authors are thankful to addis ababa institute of technology, addis ababa university, ethiopian environment and forest research institute, college of natural and computational science, addis 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base-catalyzed transesterification, procedia engineering. 53: 7-12. doi: 10.1016/j.proeng.2013.02.002 gemeda t and desta n (2020), pre-extension demonstration of moringa preparation and utilization methods in east shoa zones of oromia, ethiopia, journal of biomaterials. 4(1): 17-22. doi: 10.11648/j.jb. 20200401.12 gemechu ys (2021), production and characterization of biodiesel from moringa stenopetala seed oil via catalytic transesterification process, thesis work at addis ababa university institute of technology, addis ababa, ethiopia. hamza ta and azmach nn (2017), the miraculous moringa trees: from a nutritionaland medicinal point of view in tropical regions, journal of medicinal plants studies 5 (4): 151-162. jayed mh, masjuki hh, kalam ma, mahlia tm, husnawan m and liaquat am (2011), prospects of dedicated biodiesel engine vehicles in malaysia and indonesia, ren. sus. ener. rev. 15: 220-235. doi: 10.1016/j.rser.2010.09.002 kafuku g and mbarawa m (2010), alkaline-catalyzed biodiesel production from moringa oleifera oil with optimized production parameters, applied energy. 87 (8): 2561-2565. doi:10.1016/j. apenergy. 2010.02.026 marchetti jm and yadessa gk (2012), a review of oil extraction from plant seeds for biodiesel production, ims energy. 5(4): 316-340. doi: 10.3934/energy. 2017.2.316 mahmudul h, hagos r, mamat a, abdul a and ishak ra (2017), production, characterization and performance of biodiesel as an alternative fuel in diesel engines, renewable and sustainable energy reviews 72(c): 497-509. doi: 10.1016/j.rser.2017.01.001 piyush n, subramanian ka and dastidar mg (2013), production and characterization of biodieselfrom algae, fuel processing technology. 120: 79-88. doi: 10.1016/j.fuproc.2013.12.003 raj s and bhandari m (2017), comparison of methods of production of biodiesel from jatropha curcas, journal of biofuel. 8(2): 58-80. rao pv (2011), experimental investigations on the influence of properties of jatropha biodiesel on performance, combustion, and emission characteristics of di–ci engines, world acad. sci. eng. technol. 5(3): 855-868. sreepada h and vijayalaxmi h (2013), an overview of moringa production in ethiopia, international journal of science and research 4(4): 2319-7064. doi: 10.36106/ijsr seema r and meena b (2017), comparison of methods of biodiesel productionfrom jatropha curcas, journal of biofuels. 8(2): 58-80. doi: https://doi.org/10.3329/bjsir.v58i1.62772 received: 17 november 2022 revised: 01 january 2023 accepted: 15 january 2023 its advantages is it is considered a great natural cosmetic emollient and has high oxidative stability (ayerza, 2012). moringa plant is a high-value tree of the moringaceae family. it consists of 13 species highly distributed in africa and asia (hamza and azmach, 2017). moringa is particularly suitable for dry regions since it can be grown using rainwater without expensive irrigation techniques. moringa has been given less attention and ignored tree by communities to utilize it in different ways (gemeda and desta, 2020). flowering begins within the first six months. moringa stenopetala seed is an available and underutilized resource. ethiopia has a comfortable environment for mooring stenopetala plantations. many parts of the country particularly southern parts such as gamo goffa, sidama wolayitta, konso, and darashe have planted moringa in their garden and farmland (sreepada and vijayalaxmi, 2013). thus, this study investigated that moringa stenopetala seed oil is a potential industrial feedstock for biodiesel production as an alternative energy source. materials and methods the sample of moringa seed was collected from the gamo goffa zone, arba minch area of ethiopia. the seed sample was dried and milled to reduce the particle size. then, 80 g of sample was measured and put into the soxhlet apparatus thimble. then, it was placed in a 500 ml capacity soxhlet chamber. 400 ml solvent (hexane) was used for the extraction at different temperatures for 3 hrs. to 5 hrs. the extraction was conducted at 70°c, 75°c, and 80°c by varying extraction time to get the maximum possible oil yield. the soxhlet extraction method was selected since it results in high oil yield, is quick, the solvent can be reused, and is low cost (sreepada and vijayalaxmi, 2013). the unwanted substances were removed by evaporation and degumming. evaporation was used to separate hexane from biodiesel from moringa stenopetala seed oil 58(1) 202336 the most common production technology of biodiesel is the transesterification process. transesterification is a chemical reaction between one mole of triglyceride with three moles of alcohol to produce fatty acid methyl ester and glycerol in the presence of a catalyst or without a catalyst. most transesterification reactions use ethanol or methanol alcohol. many studies show that methanol is more practically used as alcohol than ethanol. methanol is preferable due to its low cost and its physical and chemical advantages. another advantage of using methanol is the ease of separation of glycerin which can be achieved by simple decantation (marchetti and yadessa, 2012). various catalysts can be used in the process. however, it was confirmed that the transesterification reaction was completed very fast when alkali catalysts are used. after the transesterification reaction is completed, glycerol, catalyst, alcohol, and soap are separated from biodiesel. the factors affecting biodiesel yield and fuel quality are alcohol-to-oil ratios, temperature, catalyst loading, and reaction time (raj and bhandari, 2017). biodiesel is formed when triglyceride reacts with alcohol leaving glycerol as a byproduct as shown in figure 1. there are more than 300 vegetable oils identified as potential feedstocks for biodiesel production globally. the availability, characteristics, and variety of feedstocks make them promising ingredients for the sustainable production of biodiesel (piyush et al. 2013). researchers have proposed moringa seed oil as an alternative potential feedstock to produce biodiesel. however, there is a research gap that promotes this feedstock for industrial processing. moringa seed has an average of 35%-45% oil content with high oleic content of greater than 73% based on the type of the tree. moringa oil has many various industrial and homemade benefits. one of oil by rotary evaporation at 80°c. gum and wax were removed by a degumming method. then, biodiesel was synthesized by transesterification reaction using a homogenous catalyst (methanol) at different process parameters. experimental design the experimental design used for this study was a box behnken design standard using design expert 11.0 software. the experimental design was done using three variables and tree levels for a response surface method. 17 experimental runswere selected by design expert 11.0 software using the box behnken design standard method, with five central points per block. the main factors that affect biodiesel production by transesterification reaction are reaction time, reaction temperature, and alcohol-to-oil ratio (seema and meena, 2017). as indicated in table i, the overall production of biodiesel was carried out at optimum parameters of catalyst load of 0.5 to 1.5 wt.%, reaction temperature of 45 to 65°c, and methanol to oil ratio of 3 to 9. the other parameters, reaction time and mixing intensity were kept constant at 1 hour and 500 rpm for all experimental runs. a combination of three factors and three levels of experimental runs was conducted. there are 17 experimental runs determined bybox behnken’s design arrangement as shown in table ii. production and purification of the product the method used to produce biodiesel was a one-steptransesterification reaction. methanol was the alcohol selected for the transesterification reaction due to its availability, low cost, popularity, and ease of separation (demirbas, 2005). the catalyst selected for this study was the base catalyst (koh) since biodiesel can be produced at low temperatures and pressure reactions. moreover, it is a homogeneous base catalyst that results in high conversion, minimum side reactions, short reaction time, and high yield (marchetti and yadessa, 2012). though it has many advantages, the disadvantage of the catalyst used is it cannot be reused. when the reaction is completed, biodiesel and glycerol were separated by a separatory funnel after it settles for 24 hours. then, biodiesel was washed with hot distilled water to remove soap, remaining methanol, and wax. optimization of the process parameters using the response surface method (rsm). optimization aims to determine the optimum value of the factors that affect the transesterification process to produce the maximum possible biodiesel yield at a minimum production cost. this is done by minimizing the methanol to oil ratio, reaction temperature, and amount of catalyst used as indicated in table iii. characterization of biodiesel characterization of fuel is determining the physical and chemical properties (atabani et al. 2013). the physical and chemical properties of biodiesel were determined according to the american society for testing materials (astm d 6751) and european standard (en 14214) methods (demirbas, 2005). table iv showed the physical and chemical properties of biodiesel and the standard methods used to determine them. statistical analysis of experimental results data analysis of the experiment was done by design expert 11.0 software using box behnken design standard. the significance of experimental variables was obtained from analysis of variance (anova). results and discussions yield the maximum oil yield obtained at optimum conditions of temperature 80°c and extraction time 5 hours was 39.86 %. this result agreed with the average oil content of moringa stenopetala seed oil which is 35% 45% (ayerza, 2012), and this result also agreed with the previous reportof 38% which was reported by azad et al. (2015) and by gemechu (2021). the maximum yield of biodiesel was 94% and it was obtained at optimum process parameters of methanol to oil ratio 6:1, temperature 55°c, and catalyst loading 1.0%. the yield of biodiesel obtained agrees with the previous report of azad et al. (2015) which was 91%. the yield increased as transesterification parameters increased until the optimum value and decreased beyond the optimum value. at the lower value of parameters, the yield decreased due to the incomplete conversion of reactants to the product. table v showed the yield response of all experimental runs. characterization of biodiesel physical and chemical properties of biodiesel were evaluated using standard methods and the results were compared with astm and en standard methods and previous reports. density the value of the density of biodiesel was 874 kg/m3. this result is within the standard range of density (860 – 900 kg/m3) (demirbas, 2005) and agrees with the previous report by kafuku and mbarawa (2010) which was 900 kg/m3. higher density increases thesize of fuel droplets and causes higher emission of particulate matter and nox emission ina diesel engine while the lower density of fuel expands the efficiency of atomization (choi and reitz, 1999). kinematic viscosity the experimental result showed that the value of kinematic viscosity was 4.8 mm2/s. this result is within the range of the astm standard value of biodiesel which is 1.6-6 (eman and cadence, 2013; demirbas, 2005). highly viscous fuel is difficult to pump and operate in internal combustion engines while lower kinematic viscosity of fuels increases wear leakage due to insufficient lubrication (rao, 2011). acid value the value of an acid value obtained was 0.4 mm koh/g. this result agrees with the previous report (kafuku and mbarawa, 2010), with a value of 1.2 mmkoh/g. higher acid-value fuels need further acid treatment costs and it also lowers the quality of the fuels. in this study, the lower acid value of biodiesel indicates that it has higher fuel quality. calorific value the experimental result showed that the value of biodiesel was 10287 cal/ g or 43 mj/kj. this result agrees with the previous report of mahamudul et al. (2017) which was 39 mj/kg, and the previous report of agarwal and das (2001) which was 43.2 kj/kg. the result obtained is above the standard astm value which is 42-42.5 mj/kg. this result indicates the higher fuel quality of biodiesel. the calorific value obtained is similar to that of conventional diesel fuels. this is the novel result of this study. flash point the flash point obtained from the experimental result was 184°c. this result agrees with the standard astm value of biodiesel flash point which is greater than 130°c. from this study, the higher flash point of biodiesel indicates that it is safer to handle, store and transport the fuel (jayed et al. 2011). cetane number the value of the cetane number observed was 53. this result agrees with the standard astm value of the cetane number of biodiesel which is greater than 47 (demirbas, 2005). fuels with higher cetane number benefit the engine performance since the engine starts rapidly and run smoothly without causing much noise. cloud and pour point the experimental result showed that the cloud and pour points of biodiesel were 10°c and 1°c respectively. this result agrees with the previous report of kafuku and mbarawa (2010) which was 10°c and 3°c respectively. cloud and pour point of fuel indicates the fuel performance at low ambient temperature (agarwal and das, 2001). table vi showed the result of all main physicochemical properties of biodiesel synthesized. statistical analysis of experimental results analysis of variance (anova) for the quadratic model analysis of variance determines the significance of the experimental results using coded variables as indicated in table vii. the model f-value of 380.98 implies the model is significant. there is only a 0.01% chance that an f-value this large could occur due to noise. p-values less than 0.0500 indicate model terms are significant. in this case, a, b, c, a², b², c² are significant model terms. values greater than 0.1000 indicate the model terms are not significant. if there are many insignificant model terms (not counting those required to support hierarchy), model reduction may improve your model. the lack of fit f-value of 5.69 implies there is a 6.31% chance that a lack of fit f-value this large could occur due to noise. lack of fit is bad -we want the model to fit. this relatively low probability (<10%) is troubling. the coefficient estimate represents the expected change in response per unit change in factor value when all remaining factors are held constant. the intercept in an orthogonal design is the overall average response of all the runs. the coefficients are adjustments around that average based on the factor settings. when the factors are orthogonal the vifs are 1; vifs greater than 1 indicate multi-collinearity, and the higher the vif the more severe the correlation of factors. as a rough rule, vifs less than 10 are tolerable. the effect of process parameters on the yield of biodiesel effect of methanol to oil ratio figure. (2) shows the effect of methanol to oil ratio on biodiesel yield at constant temperature and catalyst loading. it showed that the yield of biodiesel increases as the methanol-to-oil ratio increases. increasing the methanol-to-oil ratio beyond the optimum value results in excess methanol which decreases the yield of biodiesel. the maximum yield of biodiesel (94%) was obtained at a methanol-to-oil ratio of 6: 1. therefore, this ratio was taken as an optimum value of the methanol-to-oil ratio. decreasing the methanol-to-oil ratio below the optimum value (3:1), decreased the conversion efficiency of the transesterification reaction and resulted in lower biodiesel yield. effect of reaction temperature figure (3) shows the effect of reaction temperature on the yield of biodiesel at a constant methanol-to-oil ratio and catalyst loading. the yield of biodiesel highly increased as temperature increased from 45°c to 55°c. maximum yield was obtained at 58°c and the yield started to decrease slightly from 58°c to 65°c due to the vaporization of methanol resulting in soap formation. the boiling point of methanol is 64.7°c. increasing reaction temperature above this point leads to methanol loss by evaporation and decreases the conversion efficiency of the reaction. at 45°c, the yield is about 75°c. effect of catalyst loading figure (4) shows the effect of catalyst loading on the yield of biodiesel at a constant methanol-to-oil ratio and temperature. as the amount of catalyst increased from 0.5% to 1.0%, the yield of biodiesel increased from 89% to 94% and the yield starts to decrease slightly as the amount of catalyst increased from 1.0% to 1.5% due to the formation of soap and emulsion. at a lower amount of catalyst (0.5%), the yield of biodiesel decreased due to the incomplete conversion of triglycerides of oil to fatty acid methyl ester. optimization of transesterification process parameters using the response surface method (rsm) the response surface method determined the optimum value of process variables that maximize the yield of the product and minimize production cost table viii showed that response surface method found 15 solutions and selected the optimum values to minimize the economic cost of temperature, methanol, and catalyst required for the reaction and to maximize the yield of biodiesel. the optimum yield of biodiesel (83.772%) was observed at a temperature of 51.537 and catalyst load of 0.500 wt.%. conclusions biodiesel is a promising biofuel that is synthesized by the transesterification of vegetable oils and animal fats. in this study, biodiesel was synthesized from moringa stenopetala seed oil using an alkali catalyst. the effect of methanol to oil ratio, reaction temperature, and catalyst weight on the yield and quality of biodiesel have been studied. biodiesel produced was characterized according to international fuel testing standards methods. the optimization of process parameters was carried out using response surface method (rsm). the experimental result showed that the highest yield of biodiesel was 94% and this result was obtained at an optimum value of temperature 55°c, methanol to oil ratio of 6:1, and catalyst load of 1.0%. increasing methanol to oil ratio, temperature, and catalyst load up to the optimum point increased the yield of biodiesel. however, further increase of the parameters above the optimum point decreased the yield of biodiesel. the temperature has the highest significant effect while the catalyst load has a lower effect. besides to characterization of different basic fuel properties of it, biodiesel can be blended with petrol-diesel at different percentages and applied in compression ignition engine to evaluate the effect of using a blend of biodiesel using different parameters such as engine power, brake thermal efficiency, specific fuel consumption, exhaust gas temperature, and greenhouse gas temperature and gas emission. however, the performance analysis of the blend of biodiesel with petrol diesel in a compression ignition engine was not done due to a lack of laboratory setup and equipment required to measure these parameters. this study did not compare biodiesel with diesel fuels used in diesel engines. moreover, it did not characterize the blend of biodiesel with petroleum fuels and did not compare biodiesel produced from other feedstocks other than moringa stenopetala. thus, further research should be done on these areas. generally, it can be concluded that moringa stenopetala is a promising alternative feedstock for biodiesel production for the reasons: it does not affect food security, has a good oil content, and can be harvested throughout the year. the biodiesel produced meets the standard fuel quality and international standard specifications. acknowledgment the authors are thankful to addis ababa institute of technology, addis ababa university, ethiopian environment and forest research institute, college of natural and computational science, addis ababa university, and ethiopian geological survey for their technical support. references agarwal ak and das lm (2001), biodiesel development and characterization for use as a fuel in compression in ignition engines, j eng gas turbines power. 123(2): 440-447. doi: 10.1115/1.1364522 atabani ae, silitonga as, ong hc, mahila tm, masjuki hh, irfan a and fayaz h (2013), non-edible vegetable oils: evaluation of oil extraction, fatty acid compositions, biodiesel production, characteristics, engine performance and emissions production, ren. sus. energy rev. 18: 211-245. doi: 10.1016/ j.rser.2012.10.013 atabani ae, mahlia tm, ifran a, masjuki hh, chong wt and keat tl (2013), investigation of physical and chemical properties of potential edible and non-edible feedstocks for biodiesel production, a comparative analysis, ren. sus. energy rev. 21: 749-55. doi: 10.1016/j.rser.2013.01.027 ayerza hr (2012), seed and oil yields of moringa oleifera variety periyakalum-1 introduced for oil production in four ecosystems of south america, ind. crops prod. 36: 70-73. doi: 10.1016/j.indcrop.2011.08.008 azad a, rasul m, khan k, subhash cs and rubayat i (2015), prospect of moringa seed oil is a sustainable biodiesel fuel in australia, procedia engineering. 105: 601-606, doi: 10.1016/j.proeng. 2015.05.037 choi c and reitz r (1999), a numerical analysis of emission characteristics of biodiesel blended fuels, j eng gas turbines power 121(1): 31-37. doi: 10.1115/1. 2816309 demirbas a (2005), potential applications of renewable energy sources, biomasscombustion problems in boiler power systems, and combustion-related environmentalissues, progress in energy and combustion sci. 31: 171-192. doi: 10.1016/j.pecs. 2005.02.002 demshemino si, donnel ps, muhamma fy, niwadike and okoro ln (2013), comparative analysis of biodiesel and petroleum diesel, international journal of education and research 1(8): 2-5. eman na and cadence it (2013), characterization of biodiesel produced from palm oilvia base-catalyzed transesterification, procedia engineering. 53: 7-12. doi: 10.1016/j.proeng.2013.02.002 gemeda t and desta n (2020), pre-extension demonstration of moringa preparation and utilization methods in east shoa zones of oromia, ethiopia, journal of biomaterials. 4(1): 17-22. doi: 10.11648/j.jb. 20200401.12 gemechu ys (2021), production and characterization of biodiesel from moringa stenopetala seed oil via catalytic transesterification process, thesis work at addis ababa university institute of technology, addis ababa, ethiopia. hamza ta and azmach nn (2017), the miraculous moringa trees: from a nutritionaland medicinal point of view in tropical regions, journal of medicinal plants studies 5 (4): 151-162. jayed mh, masjuki hh, kalam ma, mahlia tm, husnawan m and liaquat am (2011), prospects of dedicated biodiesel engine vehicles in malaysia and indonesia, ren. sus. ener. rev. 15: 220-235. doi: 10.1016/j.rser.2010.09.002 kafuku g and mbarawa m (2010), alkaline-catalyzed biodiesel production from moringa oleifera oil with optimized production parameters, applied energy. 87 (8): 2561-2565. doi:10.1016/j. apenergy. 2010.02.026 marchetti jm and yadessa gk (2012), a review of oil extraction from plant seeds for biodiesel production, ims energy. 5(4): 316-340. doi: 10.3934/energy. 2017.2.316 mahmudul h, hagos r, mamat a, abdul a and ishak ra (2017), production, characterization and performance of biodiesel as an alternative fuel in diesel engines, renewable and sustainable energy reviews 72(c): 497-509. doi: 10.1016/j.rser.2017.01.001 piyush n, subramanian ka and dastidar mg (2013), production and characterization of biodieselfrom algae, fuel processing technology. 120: 79-88. doi: 10.1016/j.fuproc.2013.12.003 raj s and bhandari m (2017), comparison of methods of production of biodiesel from jatropha curcas, journal of biofuel. 8(2): 58-80. rao pv (2011), experimental investigations on the influence of properties of jatropha biodiesel on performance, combustion, and emission characteristics of di–ci engines, world acad. sci. eng. technol. 5(3): 855-868. sreepada h and vijayalaxmi h (2013), an overview of moringa production in ethiopia, international journal of science and research 4(4): 2319-7064. doi: 10.36106/ijsr seema r and meena b (2017), comparison of methods of biodiesel productionfrom jatropha curcas, journal of biofuels. 8(2): 58-80. its advantages is it is considered a great natural cosmetic emollient and has high oxidative stability (ayerza, 2012). moringa plant is a high-value tree of the moringaceae family. it consists of 13 species highly distributed in africa and asia (hamza and azmach, 2017). moringa is particularly suitable for dry regions since it can be grown using rainwater without expensive irrigation techniques. moringa has been given less attention and ignored tree by communities to utilize it in different ways (gemeda and desta, 2020). flowering begins within the first six months. moringa stenopetala seed is an available and underutilized resource. ethiopia has a comfortable environment for mooring stenopetala plantations. many parts of the country particularly southern parts such as gamo goffa, sidama wolayitta, konso, and darashe have planted moringa in their garden and farmland (sreepada and vijayalaxmi, 2013). thus, this study investigated that moringa stenopetala seed oil is a potential industrial feedstock for biodiesel production as an alternative energy source. materials and methods the sample of moringa seed was collected from the gamo goffa zone, arba minch area of ethiopia. the seed sample was dried and milled to reduce the particle size. then, 80 g of sample was measured and put into the soxhlet apparatus thimble. then, it was placed in a 500 ml capacity soxhlet chamber. 400 ml solvent (hexane) was used for the extraction at different temperatures for 3 hrs. to 5 hrs. the extraction was conducted at 70°c, 75°c, and 80°c by varying extraction time to get the maximum possible oil yield. the soxhlet extraction method was selected since it results in high oil yield, is quick, the solvent can be reused, and is low cost (sreepada and vijayalaxmi, 2013). the unwanted substances were removed by evaporation and degumming. evaporation was used to separate hexane from fig. 1. transesterification reaction biodiesel + glycerol triglyceride + alcohol shage and ali 37 the most common production technology of biodiesel is the transesterification process. transesterification is a chemical reaction between one mole of triglyceride with three moles of alcohol to produce fatty acid methyl ester and glycerol in the presence of a catalyst or without a catalyst. most transesterification reactions use ethanol or methanol alcohol. many studies show that methanol is more practically used as alcohol than ethanol. methanol is preferable due to its low cost and its physical and chemical advantages. another advantage of using methanol is the ease of separation of glycerin which can be achieved by simple decantation (marchetti and yadessa, 2012). various catalysts can be used in the process. however, it was confirmed that the transesterification reaction was completed very fast when alkali catalysts are used. after the transesterification reaction is completed, glycerol, catalyst, alcohol, and soap are separated from biodiesel. the factors affecting biodiesel yield and fuel quality are alcohol-to-oil ratios, temperature, catalyst loading, and reaction time (raj and bhandari, 2017). biodiesel is formed when triglyceride reacts with alcohol leaving glycerol as a byproduct as shown in figure 1. there are more than 300 vegetable oils identified as potential feedstocks for biodiesel production globally. the availability, characteristics, and variety of feedstocks make them promising ingredients for the sustainable production of biodiesel (piyush et al. 2013). researchers have proposed moringa seed oil as an alternative potential feedstock to produce biodiesel. however, there is a research gap that promotes this feedstock for industrial processing. moringa seed has an average of 35%-45% oil content with high oleic content of greater than 73% based on the type of the tree. moringa oil has many various industrial and homemade benefits. one of oil by rotary evaporation at 80°c. gum and wax were removed by a degumming method. then, biodiesel was synthesized by transesterification reaction using a homogenous catalyst (methanol) at different process parameters. experimental design the experimental design used for this study was a box behnken design standard using design expert 11.0 software. the experimental design was done using three variables and tree levels for a response surface method. 17 experimental runswere selected by design expert 11.0 software using the box behnken design standard method, with five central points per block. the main factors that affect biodiesel production by transesterification reaction are reaction time, reaction temperature, and alcohol-to-oil ratio (seema and meena, 2017). as indicated in table i, the overall production of biodiesel was carried out at optimum parameters of catalyst load of 0.5 to 1.5 wt.%, reaction temperature of 45 to 65°c, and methanol to oil ratio of 3 to 9. the other parameters, reaction time and mixing intensity were kept constant at 1 hour and 500 rpm for all experimental runs. a combination of three factors and three levels of experimental runs was conducted. there are 17 experimental runs determined bybox behnken’s design arrangement as shown in table ii. production and purification of the product the method used to produce biodiesel was a one-steptransesterification reaction. methanol was the alcohol selected for the transesterification reaction due to its availability, low cost, popularity, and ease of separation (demirbas, 2005). the catalyst selected for this study was the base catalyst (koh) since biodiesel can be produced at low temperatures and pressure reactions. moreover, it is a homogeneous base catalyst that results in high conversion, minimum side reactions, short reaction time, and high yield (marchetti and yadessa, 2012). though it has many advantages, the disadvantage of the catalyst used is it cannot be reused. when the reaction is completed, biodiesel and glycerol were separated by a separatory funnel after it settles for 24 hours. then, biodiesel was washed with hot distilled water to remove soap, remaining methanol, and wax. optimization of the process parameters using the response surface method (rsm). optimization aims to determine the optimum value of the factors that affect the transesterification process to produce the maximum possible biodiesel yield at a minimum production cost. this is done by minimizing the methanol to oil ratio, reaction temperature, and amount of catalyst used as indicated in table iii. characterization of biodiesel characterization of fuel is determining the physical and chemical properties (atabani et al. 2013). the physical and chemical properties of biodiesel were determined according to the american society for testing materials (astm d 6751) and european standard (en 14214) methods (demirbas, 2005). table iv showed the physical and chemical properties of biodiesel and the standard methods used to determine them. statistical analysis of experimental results data analysis of the experiment was done by design expert 11.0 software using box behnken design standard. the significance of experimental variables was obtained from analysis of variance (anova). results and discussions yield the maximum oil yield obtained at optimum conditions of temperature 80°c and extraction time 5 hours was 39.86 %. this result agreed with the average oil content of moringa stenopetala seed oil which is 35% 45% (ayerza, 2012), and this result also agreed with the previous reportof 38% which was reported by azad et al. (2015) and by gemechu (2021). the maximum yield of biodiesel was 94% and it was obtained at optimum process parameters of methanol to oil ratio 6:1, temperature 55°c, and catalyst loading 1.0%. the yield of biodiesel obtained agrees with the previous report of azad et al. (2015) which was 91%. the yield increased as transesterification parameters increased until the optimum value and decreased beyond the optimum value. at the lower value of parameters, the yield decreased due to the incomplete conversion of reactants to the product. table v showed the yield response of all experimental runs. characterization of biodiesel physical and chemical properties of biodiesel were evaluated using standard methods and the results were compared with astm and en standard methods and previous reports. density the value of the density of biodiesel was 874 kg/m3. this result is within the standard range of density (860 – 900 kg/m3) (demirbas, 2005) and agrees with the previous report by kafuku and mbarawa (2010) which was 900 kg/m3. higher density increases thesize of fuel droplets and causes higher emission of particulate matter and nox emission ina diesel engine while the lower density of fuel expands the efficiency of atomization (choi and reitz, 1999). kinematic viscosity the experimental result showed that the value of kinematic viscosity was 4.8 mm2/s. this result is within the range of the astm standard value of biodiesel which is 1.6-6 (eman and cadence, 2013; demirbas, 2005). highly viscous fuel is difficult to pump and operate in internal combustion engines while lower kinematic viscosity of fuels increases wear leakage due to insufficient lubrication (rao, 2011). acid value the value of an acid value obtained was 0.4 mm koh/g. this result agrees with the previous report (kafuku and mbarawa, 2010), with a value of 1.2 mmkoh/g. higher acid-value fuels need further acid treatment costs and it also lowers the quality of the fuels. in this study, the lower acid value of biodiesel indicates that it has higher fuel quality. calorific value the experimental result showed that the value of biodiesel was 10287 cal/ g or 43 mj/kj. this result agrees with the previous report of mahamudul et al. (2017) which was 39 mj/kg, and the previous report of agarwal and das (2001) which was 43.2 kj/kg. the result obtained is above the standard astm value which is 42-42.5 mj/kg. this result indicates the higher fuel quality of biodiesel. the calorific value obtained is similar to that of conventional diesel fuels. this is the novel result of this study. flash point the flash point obtained from the experimental result was 184°c. this result agrees with the standard astm value of biodiesel flash point which is greater than 130°c. from this study, the higher flash point of biodiesel indicates that it is safer to handle, store and transport the fuel (jayed et al. 2011). cetane number the value of the cetane number observed was 53. this result agrees with the standard astm value of the cetane number of biodiesel which is greater than 47 (demirbas, 2005). fuels with higher cetane number benefit the engine performance since the engine starts rapidly and run smoothly without causing much noise. cloud and pour point the experimental result showed that the cloud and pour points of biodiesel were 10°c and 1°c respectively. this result agrees with the previous report of kafuku and mbarawa (2010) which was 10°c and 3°c respectively. cloud and pour point of fuel indicates the fuel performance at low ambient temperature (agarwal and das, 2001). table vi showed the result of all main physicochemical properties of biodiesel synthesized. statistical analysis of experimental results analysis of variance (anova) for the quadratic model analysis of variance determines the significance of the experimental results using coded variables as indicated in table vii. the model f-value of 380.98 implies the model is significant. there is only a 0.01% chance that an f-value this large could occur due to noise. p-values less than 0.0500 indicate model terms are significant. in this case, a, b, c, a², b², c² are significant model terms. values greater than 0.1000 indicate the model terms are not significant. if there are many insignificant model terms (not counting those required to support hierarchy), model reduction may improve your model. the lack of fit f-value of 5.69 implies there is a 6.31% chance that a lack of fit f-value this large could occur due to noise. lack of fit is bad -we want the model to fit. this relatively low probability (<10%) is troubling. the coefficient estimate represents the expected change in response per unit change in factor value when all remaining factors are held constant. the intercept in an orthogonal design is the overall average response of all the runs. the coefficients are adjustments around that average based on the factor settings. when the factors are orthogonal the vifs are 1; vifs greater than 1 indicate multi-collinearity, and the higher the vif the more severe the correlation of factors. as a rough rule, vifs less than 10 are tolerable. the effect of process parameters on the yield of biodiesel effect of methanol to oil ratio figure. (2) shows the effect of methanol to oil ratio on biodiesel yield at constant temperature and catalyst loading. it showed that the yield of biodiesel increases as the methanol-to-oil ratio increases. increasing the methanol-to-oil ratio beyond the optimum value results in excess methanol which decreases the yield of biodiesel. the maximum yield of biodiesel (94%) was obtained at a methanol-to-oil ratio of 6: 1. therefore, this ratio was taken as an optimum value of the methanol-to-oil ratio. decreasing the methanol-to-oil ratio below the optimum value (3:1), decreased the conversion efficiency of the transesterification reaction and resulted in lower biodiesel yield. effect of reaction temperature figure (3) shows the effect of reaction temperature on the yield of biodiesel at a constant methanol-to-oil ratio and catalyst loading. the yield of biodiesel highly increased as temperature increased from 45°c to 55°c. maximum yield was obtained at 58°c and the yield started to decrease slightly from 58°c to 65°c due to the vaporization of methanol resulting in soap formation. the boiling point of methanol is 64.7°c. increasing reaction temperature above this point leads to methanol loss by evaporation and decreases the conversion efficiency of the reaction. at 45°c, the yield is about 75°c. effect of catalyst loading figure (4) shows the effect of catalyst loading on the yield of biodiesel at a constant methanol-to-oil ratio and temperature. as the amount of catalyst increased from 0.5% to 1.0%, the yield of biodiesel increased from 89% to 94% and the yield starts to decrease slightly as the amount of catalyst increased from 1.0% to 1.5% due to the formation of soap and emulsion. at a lower amount of catalyst (0.5%), the yield of biodiesel decreased due to the incomplete conversion of triglycerides of oil to fatty acid methyl ester. optimization of transesterification process parameters using the response surface method (rsm) the response surface method determined the optimum value of process variables that maximize the yield of the product and minimize production cost table viii showed that response surface method found 15 solutions and selected the optimum values to minimize the economic cost of temperature, methanol, and catalyst required for the reaction and to maximize the yield of biodiesel. the optimum yield of biodiesel (83.772%) was observed at a temperature of 51.537 and catalyst load of 0.500 wt.%. conclusions biodiesel is a promising biofuel that is synthesized by the transesterification of vegetable oils and animal fats. in this study, biodiesel was synthesized from moringa stenopetala seed oil using an alkali catalyst. the effect of methanol to oil ratio, reaction temperature, and catalyst weight on the yield and quality of biodiesel have been studied. biodiesel produced was characterized according to international fuel testing standards methods. the optimization of process parameters was carried out using response surface method (rsm). the experimental result showed that the highest yield of biodiesel was 94% and this result was obtained at an optimum value of temperature 55°c, methanol to oil ratio of 6:1, and catalyst load of 1.0%. increasing methanol to oil ratio, temperature, and catalyst load up to the optimum point increased the yield of biodiesel. however, further increase of the parameters above the optimum point decreased the yield of biodiesel. the temperature has the highest significant effect while the catalyst load has a lower effect. besides to characterization of different basic fuel properties of it, biodiesel can be blended with petrol-diesel at different percentages and applied in compression ignition engine to evaluate the effect of using a blend of biodiesel using different parameters such as engine power, brake thermal efficiency, specific fuel consumption, exhaust gas temperature, and greenhouse gas temperature and gas emission. however, the performance analysis of the blend of biodiesel with petrol diesel in a compression ignition engine was not done due to a lack of laboratory setup and equipment required to measure these parameters. this study did not compare biodiesel with diesel fuels used in diesel engines. moreover, it did not characterize the blend of biodiesel with petroleum fuels and did not compare biodiesel produced from other feedstocks other than moringa stenopetala. thus, further research should be done on these areas. generally, it can be concluded that moringa stenopetala is a promising alternative feedstock for biodiesel production for the reasons: it does not affect food security, has a good oil content, and can be harvested throughout the year. the biodiesel produced meets the standard fuel quality and international standard specifications. acknowledgment the authors are thankful to addis ababa institute of technology, addis ababa university, ethiopian environment and forest research institute, college of natural and computational science, addis ababa university, and ethiopian geological survey for their technical support. references agarwal ak and das lm (2001), biodiesel development and characterization for use as a fuel in compression in ignition engines, j eng gas turbines power. 123(2): 440-447. doi: 10.1115/1.1364522 atabani ae, silitonga as, ong hc, mahila tm, masjuki hh, irfan a and fayaz h (2013), non-edible vegetable oils: evaluation of oil extraction, fatty acid compositions, biodiesel production, characteristics, engine performance and emissions production, ren. sus. energy rev. 18: 211-245. doi: 10.1016/ j.rser.2012.10.013 atabani ae, mahlia tm, ifran a, masjuki hh, chong wt and keat tl (2013), investigation of physical and chemical properties of potential edible and non-edible feedstocks for biodiesel production, a comparative analysis, ren. sus. energy rev. 21: 749-55. doi: 10.1016/j.rser.2013.01.027 ayerza hr (2012), seed and oil yields of moringa oleifera variety periyakalum-1 introduced for oil production in four ecosystems of south america, ind. crops prod. 36: 70-73. doi: 10.1016/j.indcrop.2011.08.008 azad a, rasul m, khan k, subhash cs and rubayat i (2015), prospect of moringa seed oil is a sustainable biodiesel fuel in australia, procedia engineering. 105: 601-606, doi: 10.1016/j.proeng. 2015.05.037 choi c and reitz r (1999), a numerical analysis of emission characteristics of biodiesel blended fuels, j eng gas turbines power 121(1): 31-37. doi: 10.1115/1. 2816309 demirbas a (2005), potential applications of renewable energy sources, biomasscombustion problems in boiler power systems, and combustion-related environmentalissues, progress in energy and combustion sci. 31: 171-192. doi: 10.1016/j.pecs. 2005.02.002 demshemino si, donnel ps, muhamma fy, niwadike and okoro ln (2013), comparative analysis of biodiesel and petroleum diesel, international journal of education and research 1(8): 2-5. eman na and cadence it (2013), characterization of biodiesel produced from palm oilvia base-catalyzed transesterification, procedia engineering. 53: 7-12. doi: 10.1016/j.proeng.2013.02.002 gemeda t and desta n (2020), pre-extension demonstration of moringa preparation and utilization methods in east shoa zones of oromia, ethiopia, journal of biomaterials. 4(1): 17-22. doi: 10.11648/j.jb. 20200401.12 gemechu ys (2021), production and characterization of biodiesel from moringa stenopetala seed oil via catalytic transesterification process, thesis work at addis ababa university institute of technology, addis ababa, ethiopia. hamza ta and azmach nn (2017), the miraculous moringa trees: from a nutritionaland medicinal point of view in tropical regions, journal of medicinal plants studies 5 (4): 151-162. jayed mh, masjuki hh, kalam ma, mahlia tm, husnawan m and liaquat am (2011), prospects of dedicated biodiesel engine vehicles in malaysia and indonesia, ren. sus. ener. rev. 15: 220-235. doi: 10.1016/j.rser.2010.09.002 kafuku g and mbarawa m (2010), alkaline-catalyzed biodiesel production from moringa oleifera oil with optimized production parameters, applied energy. 87 (8): 2561-2565. doi:10.1016/j. apenergy. 2010.02.026 marchetti jm and yadessa gk (2012), a review of oil extraction from plant seeds for biodiesel production, ims energy. 5(4): 316-340. doi: 10.3934/energy. 2017.2.316 mahmudul h, hagos r, mamat a, abdul a and ishak ra (2017), production, characterization and performance of biodiesel as an alternative fuel in diesel engines, renewable and sustainable energy reviews 72(c): 497-509. doi: 10.1016/j.rser.2017.01.001 piyush n, subramanian ka and dastidar mg (2013), production and characterization of biodieselfrom algae, fuel processing technology. 120: 79-88. doi: 10.1016/j.fuproc.2013.12.003 raj s and bhandari m (2017), comparison of methods of production of biodiesel from jatropha curcas, journal of biofuel. 8(2): 58-80. rao pv (2011), experimental investigations on the influence of properties of jatropha biodiesel on performance, combustion, and emission characteristics of di–ci engines, world acad. sci. eng. technol. 5(3): 855-868. sreepada h and vijayalaxmi h (2013), an overview of moringa production in ethiopia, international journal of science and research 4(4): 2319-7064. doi: 10.36106/ijsr seema r and meena b (2017), comparison of methods of biodiesel productionfrom jatropha curcas, journal of biofuels. 8(2): 58-80. its advantages is it is considered a great natural cosmetic emollient and has high oxidative stability (ayerza, 2012). moringa plant is a high-value tree of the moringaceae family. it consists of 13 species highly distributed in africa and asia (hamza and azmach, 2017). moringa is particularly suitable for dry regions since it can be grown using rainwater without expensive irrigation techniques. moringa has been given less attention and ignored tree by communities to utilize it in different ways (gemeda and desta, 2020). flowering begins within the first six months. moringa stenopetala seed is an available and underutilized resource. ethiopia has a comfortable environment for mooring stenopetala plantations. many parts of the country particularly southern parts such as gamo goffa, sidama wolayitta, konso, and darashe have planted moringa in their garden and farmland (sreepada and vijayalaxmi, 2013). thus, this study investigated that moringa stenopetala seed oil is a potential industrial feedstock for biodiesel production as an alternative energy source. materials and methods the sample of moringa seed was collected from the gamo goffa zone, arba minch area of ethiopia. the seed sample was dried and milled to reduce the particle size. then, 80 g of sample was measured and put into the soxhlet apparatus thimble. then, it was placed in a 500 ml capacity soxhlet chamber. 400 ml solvent (hexane) was used for the extraction at different temperatures for 3 hrs. to 5 hrs. the extraction was conducted at 70°c, 75°c, and 80°c by varying extraction time to get the maximum possible oil yield. the soxhlet extraction method was selected since it results in high oil yield, is quick, the solvent can be reused, and is low cost (sreepada and vijayalaxmi, 2013). the unwanted substances were removed by evaporation and degumming. evaporation was used to separate hexane from variable unit level -1 +1 methanol to oil ratio 3 9 catalyst loading wt.% 0.5 1.5 reaction temperature °c 45 65 table i. independent variables and level of main factors that affect transesterification reaction volume of pure biodiesel produced a volume of oil used yield (%) = *100 biodiesel from moringa stenopetala seed oil 58(1) 202338 the most common production technology of biodiesel is the transesterification process. transesterification is a chemical reaction between one mole of triglyceride with three moles of alcohol to produce fatty acid methyl ester and glycerol in the presence of a catalyst or without a catalyst. most transesterification reactions use ethanol or methanol alcohol. many studies show that methanol is more practically used as alcohol than ethanol. methanol is preferable due to its low cost and its physical and chemical advantages. another advantage of using methanol is the ease of separation of glycerin which can be achieved by simple decantation (marchetti and yadessa, 2012). various catalysts can be used in the process. however, it was confirmed that the transesterification reaction was completed very fast when alkali catalysts are used. after the transesterification reaction is completed, glycerol, catalyst, alcohol, and soap are separated from biodiesel. the factors affecting biodiesel yield and fuel quality are alcohol-to-oil ratios, temperature, catalyst loading, and reaction time (raj and bhandari, 2017). biodiesel is formed when triglyceride reacts with alcohol leaving glycerol as a byproduct as shown in figure 1. there are more than 300 vegetable oils identified as potential feedstocks for biodiesel production globally. the availability, characteristics, and variety of feedstocks make them promising ingredients for the sustainable production of biodiesel (piyush et al. 2013). researchers have proposed moringa seed oil as an alternative potential feedstock to produce biodiesel. however, there is a research gap that promotes this feedstock for industrial processing. moringa seed has an average of 35%-45% oil content with high oleic content of greater than 73% based on the type of the tree. moringa oil has many various industrial and homemade benefits. one of oil by rotary evaporation at 80°c. gum and wax were removed by a degumming method. then, biodiesel was synthesized by transesterification reaction using a homogenous catalyst (methanol) at different process parameters. experimental design the experimental design used for this study was a box behnken design standard using design expert 11.0 software. the experimental design was done using three variables and tree levels for a response surface method. 17 experimental runswere selected by design expert 11.0 software using the box behnken design standard method, with five central points per block. the main factors that affect biodiesel production by transesterification reaction are reaction time, reaction temperature, and alcohol-to-oil ratio (seema and meena, 2017). as indicated in table i, the overall production of biodiesel was carried out at optimum parameters of catalyst load of 0.5 to 1.5 wt.%, reaction temperature of 45 to 65°c, and methanol to oil ratio of 3 to 9. the other parameters, reaction time and mixing intensity were kept constant at 1 hour and 500 rpm for all experimental runs. a combination of three factors and three levels of experimental runs was conducted. there are 17 experimental runs determined bybox behnken’s design arrangement as shown in table ii. production and purification of the product the method used to produce biodiesel was a one-steptransesterification reaction. methanol was the alcohol selected for the transesterification reaction due to its availability, low cost, popularity, and ease of separation (demirbas, 2005). the catalyst selected for this study was the base catalyst (koh) since biodiesel can be produced at low temperatures and pressure reactions. moreover, it is a homogeneous base catalyst that results in high conversion, minimum side reactions, short reaction time, and high yield (marchetti and yadessa, 2012). though it has many advantages, the disadvantage of the catalyst used is it cannot be reused. when the reaction is completed, biodiesel and glycerol were separated by a separatory funnel after it settles for 24 hours. then, biodiesel was washed with hot distilled water to remove soap, remaining methanol, and wax. optimization of the process parameters using the response surface method (rsm). optimization aims to determine the optimum value of the factors that affect the transesterification process to produce the maximum possible biodiesel yield at a minimum production cost. this is done by minimizing the methanol to oil ratio, reaction temperature, and amount of catalyst used as indicated in table iii. characterization of biodiesel characterization of fuel is determining the physical and chemical properties (atabani et al. 2013). the physical and chemical properties of biodiesel were determined according to the american society for testing materials (astm d 6751) and european standard (en 14214) methods (demirbas, 2005). table iv showed the physical and chemical properties of biodiesel and the standard methods used to determine them. statistical analysis of experimental results data analysis of the experiment was done by design expert 11.0 software using box behnken design standard. the significance of experimental variables was obtained from analysis of variance (anova). results and discussions yield the maximum oil yield obtained at optimum conditions of temperature 80°c and extraction time 5 hours was 39.86 %. this result agreed with the average oil content of moringa stenopetala seed oil which is 35% 45% (ayerza, 2012), and this result also agreed with the previous reportof 38% which was reported by azad et al. (2015) and by gemechu (2021). the maximum yield of biodiesel was 94% and it was obtained at optimum process parameters of methanol to oil ratio 6:1, temperature 55°c, and catalyst loading 1.0%. the yield of biodiesel obtained agrees with the previous report of azad et al. (2015) which was 91%. the yield increased as transesterification parameters increased until the optimum value and decreased beyond the optimum value. at the lower value of parameters, the yield decreased due to the incomplete conversion of reactants to the product. table v showed the yield response of all experimental runs. characterization of biodiesel physical and chemical properties of biodiesel were evaluated using standard methods and the results were compared with astm and en standard methods and previous reports. density the value of the density of biodiesel was 874 kg/m3. this result is within the standard range of density (860 – 900 kg/m3) (demirbas, 2005) and agrees with the previous report by kafuku and mbarawa (2010) which was 900 kg/m3. higher density increases thesize of fuel droplets and causes higher emission of particulate matter and nox emission ina diesel engine while the lower density of fuel expands the efficiency of atomization (choi and reitz, 1999). kinematic viscosity the experimental result showed that the value of kinematic viscosity was 4.8 mm2/s. this result is within the range of the astm standard value of biodiesel which is 1.6-6 (eman and cadence, 2013; demirbas, 2005). highly viscous fuel is difficult to pump and operate in internal combustion engines while lower kinematic viscosity of fuels increases wear leakage due to insufficient lubrication (rao, 2011). acid value the value of an acid value obtained was 0.4 mm koh/g. this result agrees with the previous report (kafuku and mbarawa, 2010), with a value of 1.2 mmkoh/g. higher acid-value fuels need further acid treatment costs and it also lowers the quality of the fuels. in this study, the lower acid value of biodiesel indicates that it has higher fuel quality. calorific value the experimental result showed that the value of biodiesel was 10287 cal/ g or 43 mj/kj. this result agrees with the previous report of mahamudul et al. (2017) which was 39 mj/kg, and the previous report of agarwal and das (2001) which was 43.2 kj/kg. the result obtained is above the standard astm value which is 42-42.5 mj/kg. this result indicates the higher fuel quality of biodiesel. the calorific value obtained is similar to that of conventional diesel fuels. this is the novel result of this study. flash point the flash point obtained from the experimental result was 184°c. this result agrees with the standard astm value of biodiesel flash point which is greater than 130°c. from this study, the higher flash point of biodiesel indicates that it is safer to handle, store and transport the fuel (jayed et al. 2011). cetane number the value of the cetane number observed was 53. this result agrees with the standard astm value of the cetane number of biodiesel which is greater than 47 (demirbas, 2005). fuels with higher cetane number benefit the engine performance since the engine starts rapidly and run smoothly without causing much noise. cloud and pour point the experimental result showed that the cloud and pour points of biodiesel were 10°c and 1°c respectively. this result agrees with the previous report of kafuku and mbarawa (2010) which was 10°c and 3°c respectively. cloud and pour point of fuel indicates the fuel performance at low ambient temperature (agarwal and das, 2001). table vi showed the result of all main physicochemical properties of biodiesel synthesized. statistical analysis of experimental results analysis of variance (anova) for the quadratic model analysis of variance determines the significance of the experimental results using coded variables as indicated in table vii. the model f-value of 380.98 implies the model is significant. there is only a 0.01% chance that an f-value this large could occur due to noise. p-values less than 0.0500 indicate model terms are significant. in this case, a, b, c, a², b², c² are significant model terms. values greater than 0.1000 indicate the model terms are not significant. if there are many insignificant model terms (not counting those required to support hierarchy), model reduction may improve your model. the lack of fit f-value of 5.69 implies there is a 6.31% chance that a lack of fit f-value this large could occur due to noise. lack of fit is bad -we want the model to fit. this relatively low probability (<10%) is troubling. the coefficient estimate represents the expected change in response per unit change in factor value when all remaining factors are held constant. the intercept in an orthogonal design is the overall average response of all the runs. the coefficients are adjustments around that average based on the factor settings. when the factors are orthogonal the vifs are 1; vifs greater than 1 indicate multi-collinearity, and the higher the vif the more severe the correlation of factors. as a rough rule, vifs less than 10 are tolerable. the effect of process parameters on the yield of biodiesel effect of methanol to oil ratio figure. (2) shows the effect of methanol to oil ratio on biodiesel yield at constant temperature and catalyst loading. it showed that the yield of biodiesel increases as the methanol-to-oil ratio increases. increasing the methanol-to-oil ratio beyond the optimum value results in excess methanol which decreases the yield of biodiesel. the maximum yield of biodiesel (94%) was obtained at a methanol-to-oil ratio of 6: 1. therefore, this ratio was taken as an optimum value of the methanol-to-oil ratio. decreasing the methanol-to-oil ratio below the optimum value (3:1), decreased the conversion efficiency of the transesterification reaction and resulted in lower biodiesel yield. effect of reaction temperature figure (3) shows the effect of reaction temperature on the yield of biodiesel at a constant methanol-to-oil ratio and catalyst loading. the yield of biodiesel highly increased as temperature increased from 45°c to 55°c. maximum yield was obtained at 58°c and the yield started to decrease slightly from 58°c to 65°c due to the vaporization of methanol resulting in soap formation. the boiling point of methanol is 64.7°c. increasing reaction temperature above this point leads to methanol loss by evaporation and decreases the conversion efficiency of the reaction. at 45°c, the yield is about 75°c. effect of catalyst loading figure (4) shows the effect of catalyst loading on the yield of biodiesel at a constant methanol-to-oil ratio and temperature. as the amount of catalyst increased from 0.5% to 1.0%, the yield of biodiesel increased from 89% to 94% and the yield starts to decrease slightly as the amount of catalyst increased from 1.0% to 1.5% due to the formation of soap and emulsion. at a lower amount of catalyst (0.5%), the yield of biodiesel decreased due to the incomplete conversion of triglycerides of oil to fatty acid methyl ester. optimization of transesterification process parameters using the response surface method (rsm) the response surface method determined the optimum value of process variables that maximize the yield of the product and minimize production cost table viii showed that response surface method found 15 solutions and selected the optimum values to minimize the economic cost of temperature, methanol, and catalyst required for the reaction and to maximize the yield of biodiesel. the optimum yield of biodiesel (83.772%) was observed at a temperature of 51.537 and catalyst load of 0.500 wt.%. conclusions biodiesel is a promising biofuel that is synthesized by the transesterification of vegetable oils and animal fats. in this study, biodiesel was synthesized from moringa stenopetala seed oil using an alkali catalyst. the effect of methanol to oil ratio, reaction temperature, and catalyst weight on the yield and quality of biodiesel have been studied. biodiesel produced was characterized according to international fuel testing standards methods. the optimization of process parameters was carried out using response surface method (rsm). the experimental result showed that the highest yield of biodiesel was 94% and this result was obtained at an optimum value of temperature 55°c, methanol to oil ratio of 6:1, and catalyst load of 1.0%. increasing methanol to oil ratio, temperature, and catalyst load up to the optimum point increased the yield of biodiesel. however, further increase of the parameters above the optimum point decreased the yield of biodiesel. the temperature has the highest significant effect while the catalyst load has a lower effect. besides to characterization of different basic fuel properties of it, biodiesel can be blended with petrol-diesel at different percentages and applied in compression ignition engine to evaluate the effect of using a blend of biodiesel using different parameters such as engine power, brake thermal efficiency, specific fuel consumption, exhaust gas temperature, and greenhouse gas temperature and gas emission. however, the performance analysis of the blend of biodiesel with petrol diesel in a compression ignition engine was not done due to a lack of laboratory setup and equipment required to measure these parameters. this study did not compare biodiesel with diesel fuels used in diesel engines. moreover, it did not characterize the blend of biodiesel with petroleum fuels and did not compare biodiesel produced from other feedstocks other than moringa stenopetala. thus, further research should be done on these areas. generally, it can be concluded that moringa stenopetala is a promising alternative feedstock for biodiesel production for the reasons: it does not affect food security, has a good oil content, and can be harvested throughout the year. the biodiesel produced meets the standard fuel quality and international standard specifications. acknowledgment the authors are thankful to addis ababa institute of technology, addis ababa university, ethiopian environment and forest research institute, college of natural and computational science, addis ababa university, and ethiopian geological survey for their technical support. references agarwal ak and das lm (2001), biodiesel development and characterization for use as a fuel in compression in ignition engines, j eng gas turbines power. 123(2): 440-447. doi: 10.1115/1.1364522 atabani ae, silitonga as, ong hc, mahila tm, masjuki hh, irfan a and fayaz h (2013), non-edible vegetable oils: evaluation of oil extraction, fatty acid compositions, biodiesel production, characteristics, engine performance and emissions production, ren. sus. energy rev. 18: 211-245. doi: 10.1016/ j.rser.2012.10.013 atabani ae, mahlia tm, ifran a, masjuki hh, chong wt and keat tl (2013), investigation of physical and chemical properties of potential edible and non-edible feedstocks for biodiesel production, a comparative analysis, ren. sus. energy rev. 21: 749-55. doi: 10.1016/j.rser.2013.01.027 ayerza hr (2012), seed and oil yields of moringa oleifera variety periyakalum-1 introduced for oil production in four ecosystems of south america, ind. crops prod. 36: 70-73. doi: 10.1016/j.indcrop.2011.08.008 azad a, rasul m, khan k, subhash cs and rubayat i (2015), prospect of moringa seed oil is a sustainable biodiesel fuel in australia, procedia engineering. 105: 601-606, doi: 10.1016/j.proeng. 2015.05.037 choi c and reitz r (1999), a numerical analysis of emission characteristics of biodiesel blended fuels, j eng gas turbines power 121(1): 31-37. doi: 10.1115/1. 2816309 demirbas a (2005), potential applications of renewable energy sources, biomasscombustion problems in boiler power systems, and combustion-related environmentalissues, progress in energy and combustion sci. 31: 171-192. doi: 10.1016/j.pecs. 2005.02.002 demshemino si, donnel ps, muhamma fy, niwadike and okoro ln (2013), comparative analysis of biodiesel and petroleum diesel, international journal of education and research 1(8): 2-5. eman na and cadence it (2013), characterization of biodiesel produced from palm oilvia base-catalyzed transesterification, procedia engineering. 53: 7-12. doi: 10.1016/j.proeng.2013.02.002 gemeda t and desta n (2020), pre-extension demonstration of moringa preparation and utilization methods in east shoa zones of oromia, ethiopia, journal of biomaterials. 4(1): 17-22. doi: 10.11648/j.jb. 20200401.12 gemechu ys (2021), production and characterization of biodiesel from moringa stenopetala seed oil via catalytic transesterification process, thesis work at addis ababa university institute of technology, addis ababa, ethiopia. hamza ta and azmach nn (2017), the miraculous moringa trees: from a nutritionaland medicinal point of view in tropical regions, journal of medicinal plants studies 5 (4): 151-162. jayed mh, masjuki hh, kalam ma, mahlia tm, husnawan m and liaquat am (2011), prospects of dedicated biodiesel engine vehicles in malaysia and indonesia, ren. sus. ener. rev. 15: 220-235. doi: 10.1016/j.rser.2010.09.002 kafuku g and mbarawa m (2010), alkaline-catalyzed biodiesel production from moringa oleifera oil with optimized production parameters, applied energy. 87 (8): 2561-2565. doi:10.1016/j. apenergy. 2010.02.026 marchetti jm and yadessa gk (2012), a review of oil extraction from plant seeds for biodiesel production, ims energy. 5(4): 316-340. doi: 10.3934/energy. 2017.2.316 mahmudul h, hagos r, mamat a, abdul a and ishak ra (2017), production, characterization and performance of biodiesel as an alternative fuel in diesel engines, renewable and sustainable energy reviews 72(c): 497-509. doi: 10.1016/j.rser.2017.01.001 piyush n, subramanian ka and dastidar mg (2013), production and characterization of biodieselfrom algae, fuel processing technology. 120: 79-88. doi: 10.1016/j.fuproc.2013.12.003 raj s and bhandari m (2017), comparison of methods of production of biodiesel from jatropha curcas, journal of biofuel. 8(2): 58-80. rao pv (2011), experimental investigations on the influence of properties of jatropha biodiesel on performance, combustion, and emission characteristics of di–ci engines, world acad. sci. eng. technol. 5(3): 855-868. sreepada h and vijayalaxmi h (2013), an overview of moringa production in ethiopia, international journal of science and research 4(4): 2319-7064. doi: 10.36106/ijsr seema r and meena b (2017), comparison of methods of biodiesel productionfrom jatropha curcas, journal of biofuels. 8(2): 58-80. its advantages is it is considered a great natural cosmetic emollient and has high oxidative stability (ayerza, 2012). moringa plant is a high-value tree of the moringaceae family. it consists of 13 species highly distributed in africa and asia (hamza and azmach, 2017). moringa is particularly suitable for dry regions since it can be grown using rainwater without expensive irrigation techniques. moringa has been given less attention and ignored tree by communities to utilize it in different ways (gemeda and desta, 2020). flowering begins within the first six months. moringa stenopetala seed is an available and underutilized resource. ethiopia has a comfortable environment for mooring stenopetala plantations. many parts of the country particularly southern parts such as gamo goffa, sidama wolayitta, konso, and darashe have planted moringa in their garden and farmland (sreepada and vijayalaxmi, 2013). thus, this study investigated that moringa stenopetala seed oil is a potential industrial feedstock for biodiesel production as an alternative energy source. materials and methods the sample of moringa seed was collected from the gamo goffa zone, arba minch area of ethiopia. the seed sample was dried and milled to reduce the particle size. then, 80 g of sample was measured and put into the soxhlet apparatus thimble. then, it was placed in a 500 ml capacity soxhlet chamber. 400 ml solvent (hexane) was used for the extraction at different temperatures for 3 hrs. to 5 hrs. the extraction was conducted at 70°c, 75°c, and 80°c by varying extraction time to get the maximum possible oil yield. the soxhlet extraction method was selected since it results in high oil yield, is quick, the solvent can be reused, and is low cost (sreepada and vijayalaxmi, 2013). the unwanted substances were removed by evaporation and degumming. evaporation was used to separate hexane from table ii. box behnken design arrangement (experimental design matrix) run factor 1 a: methanol to oil ratio factor 2 b: temperature factor 3 c: catalyst loading yield response (%) 1 6 55 1.0 2 6 65 0.5 3 6 45 0.5 4 3 55 1.5 5 9 45 1.0 6 9 65 1.0 7 3 65 1.0 8 6 55 1.0 9 6 55 1.0 10 9 55 0.5 11 3 55 0.5 12 6 55 1.0 13 3 45 1.0 14 9 55 1.5 15 6 45 1.5 16 6 65 1.5 17 6 55 1.0 table iii. the goal of optimization and limitation of process parameters name goal lower limit upper limit lower weight upper weight importance a: methanol to oil ratio minimize 3 9 1 3 3 b: temperature minimize 45 65 1 3 3 c: catalyst loading minimize 0.5 1.5 1 3 3 yield maximize 65.67 94.0 1 3 3 shage and ali 39 the most common production technology of biodiesel is the transesterification process. transesterification is a chemical reaction between one mole of triglyceride with three moles of alcohol to produce fatty acid methyl ester and glycerol in the presence of a catalyst or without a catalyst. most transesterification reactions use ethanol or methanol alcohol. many studies show that methanol is more practically used as alcohol than ethanol. methanol is preferable due to its low cost and its physical and chemical advantages. another advantage of using methanol is the ease of separation of glycerin which can be achieved by simple decantation (marchetti and yadessa, 2012). various catalysts can be used in the process. however, it was confirmed that the transesterification reaction was completed very fast when alkali catalysts are used. after the transesterification reaction is completed, glycerol, catalyst, alcohol, and soap are separated from biodiesel. the factors affecting biodiesel yield and fuel quality are alcohol-to-oil ratios, temperature, catalyst loading, and reaction time (raj and bhandari, 2017). biodiesel is formed when triglyceride reacts with alcohol leaving glycerol as a byproduct as shown in figure 1. there are more than 300 vegetable oils identified as potential feedstocks for biodiesel production globally. the availability, characteristics, and variety of feedstocks make them promising ingredients for the sustainable production of biodiesel (piyush et al. 2013). researchers have proposed moringa seed oil as an alternative potential feedstock to produce biodiesel. however, there is a research gap that promotes this feedstock for industrial processing. moringa seed has an average of 35%-45% oil content with high oleic content of greater than 73% based on the type of the tree. moringa oil has many various industrial and homemade benefits. one of oil by rotary evaporation at 80°c. gum and wax were removed by a degumming method. then, biodiesel was synthesized by transesterification reaction using a homogenous catalyst (methanol) at different process parameters. experimental design the experimental design used for this study was a box behnken design standard using design expert 11.0 software. the experimental design was done using three variables and tree levels for a response surface method. 17 experimental runswere selected by design expert 11.0 software using the box behnken design standard method, with five central points per block. the main factors that affect biodiesel production by transesterification reaction are reaction time, reaction temperature, and alcohol-to-oil ratio (seema and meena, 2017). as indicated in table i, the overall production of biodiesel was carried out at optimum parameters of catalyst load of 0.5 to 1.5 wt.%, reaction temperature of 45 to 65°c, and methanol to oil ratio of 3 to 9. the other parameters, reaction time and mixing intensity were kept constant at 1 hour and 500 rpm for all experimental runs. a combination of three factors and three levels of experimental runs was conducted. there are 17 experimental runs determined bybox behnken’s design arrangement as shown in table ii. production and purification of the product the method used to produce biodiesel was a one-steptransesterification reaction. methanol was the alcohol selected for the transesterification reaction due to its availability, low cost, popularity, and ease of separation (demirbas, 2005). the catalyst selected for this study was the base catalyst (koh) since biodiesel can be produced at low temperatures and pressure reactions. moreover, it is a homogeneous base catalyst that results in high conversion, minimum side reactions, short reaction time, and high yield (marchetti and yadessa, 2012). though it has many advantages, the disadvantage of the catalyst used is it cannot be reused. when the reaction is completed, biodiesel and glycerol were separated by a separatory funnel after it settles for 24 hours. then, biodiesel was washed with hot distilled water to remove soap, remaining methanol, and wax. optimization of the process parameters using the response surface method (rsm). optimization aims to determine the optimum value of the factors that affect the transesterification process to produce the maximum possible biodiesel yield at a minimum production cost. this is done by minimizing the methanol to oil ratio, reaction temperature, and amount of catalyst used as indicated in table iii. characterization of biodiesel characterization of fuel is determining the physical and chemical properties (atabani et al. 2013). the physical and chemical properties of biodiesel were determined according to the american society for testing materials (astm d 6751) and european standard (en 14214) methods (demirbas, 2005). table iv showed the physical and chemical properties of biodiesel and the standard methods used to determine them. statistical analysis of experimental results data analysis of the experiment was done by design expert 11.0 software using box behnken design standard. the significance of experimental variables was obtained from analysis of variance (anova). results and discussions yield the maximum oil yield obtained at optimum conditions of temperature 80°c and extraction time 5 hours was 39.86 %. this result agreed with the average oil content of moringa stenopetala seed oil which is 35% 45% (ayerza, 2012), and this result also agreed with the previous reportof 38% which was reported by azad et al. (2015) and by gemechu (2021). the maximum yield of biodiesel was 94% and it was obtained at optimum process parameters of methanol to oil ratio 6:1, temperature 55°c, and catalyst loading 1.0%. the yield of biodiesel obtained agrees with the previous report of azad et al. (2015) which was 91%. the yield increased as transesterification parameters increased until the optimum value and decreased beyond the optimum value. at the lower value of parameters, the yield decreased due to the incomplete conversion of reactants to the product. table v showed the yield response of all experimental runs. characterization of biodiesel physical and chemical properties of biodiesel were evaluated using standard methods and the results were compared with astm and en standard methods and previous reports. density the value of the density of biodiesel was 874 kg/m3. this result is within the standard range of density (860 – 900 kg/m3) (demirbas, 2005) and agrees with the previous report by kafuku and mbarawa (2010) which was 900 kg/m3. higher density increases thesize of fuel droplets and causes higher emission of particulate matter and nox emission ina diesel engine while the lower density of fuel expands the efficiency of atomization (choi and reitz, 1999). kinematic viscosity the experimental result showed that the value of kinematic viscosity was 4.8 mm2/s. this result is within the range of the astm standard value of biodiesel which is 1.6-6 (eman and cadence, 2013; demirbas, 2005). highly viscous fuel is difficult to pump and operate in internal combustion engines while lower kinematic viscosity of fuels increases wear leakage due to insufficient lubrication (rao, 2011). acid value the value of an acid value obtained was 0.4 mm koh/g. this result agrees with the previous report (kafuku and mbarawa, 2010), with a value of 1.2 mmkoh/g. higher acid-value fuels need further acid treatment costs and it also lowers the quality of the fuels. in this study, the lower acid value of biodiesel indicates that it has higher fuel quality. calorific value the experimental result showed that the value of biodiesel was 10287 cal/ g or 43 mj/kj. this result agrees with the previous report of mahamudul et al. (2017) which was 39 mj/kg, and the previous report of agarwal and das (2001) which was 43.2 kj/kg. the result obtained is above the standard astm value which is 42-42.5 mj/kg. this result indicates the higher fuel quality of biodiesel. the calorific value obtained is similar to that of conventional diesel fuels. this is the novel result of this study. flash point the flash point obtained from the experimental result was 184°c. this result agrees with the standard astm value of biodiesel flash point which is greater than 130°c. from this study, the higher flash point of biodiesel indicates that it is safer to handle, store and transport the fuel (jayed et al. 2011). cetane number the value of the cetane number observed was 53. this result agrees with the standard astm value of the cetane number of biodiesel which is greater than 47 (demirbas, 2005). fuels with higher cetane number benefit the engine performance since the engine starts rapidly and run smoothly without causing much noise. cloud and pour point the experimental result showed that the cloud and pour points of biodiesel were 10°c and 1°c respectively. this result agrees with the previous report of kafuku and mbarawa (2010) which was 10°c and 3°c respectively. cloud and pour point of fuel indicates the fuel performance at low ambient temperature (agarwal and das, 2001). table vi showed the result of all main physicochemical properties of biodiesel synthesized. statistical analysis of experimental results analysis of variance (anova) for the quadratic model analysis of variance determines the significance of the experimental results using coded variables as indicated in table vii. the model f-value of 380.98 implies the model is significant. there is only a 0.01% chance that an f-value this large could occur due to noise. p-values less than 0.0500 indicate model terms are significant. in this case, a, b, c, a², b², c² are significant model terms. values greater than 0.1000 indicate the model terms are not significant. if there are many insignificant model terms (not counting those required to support hierarchy), model reduction may improve your model. the lack of fit f-value of 5.69 implies there is a 6.31% chance that a lack of fit f-value this large could occur due to noise. lack of fit is bad -we want the model to fit. this relatively low probability (<10%) is troubling. the coefficient estimate represents the expected change in response per unit change in factor value when all remaining factors are held constant. the intercept in an orthogonal design is the overall average response of all the runs. the coefficients are adjustments around that average based on the factor settings. when the factors are orthogonal the vifs are 1; vifs greater than 1 indicate multi-collinearity, and the higher the vif the more severe the correlation of factors. as a rough rule, vifs less than 10 are tolerable. the effect of process parameters on the yield of biodiesel effect of methanol to oil ratio figure. (2) shows the effect of methanol to oil ratio on biodiesel yield at constant temperature and catalyst loading. it showed that the yield of biodiesel increases as the methanol-to-oil ratio increases. increasing the methanol-to-oil ratio beyond the optimum value results in excess methanol which decreases the yield of biodiesel. the maximum yield of biodiesel (94%) was obtained at a methanol-to-oil ratio of 6: 1. therefore, this ratio was taken as an optimum value of the methanol-to-oil ratio. decreasing the methanol-to-oil ratio below the optimum value (3:1), decreased the conversion efficiency of the transesterification reaction and resulted in lower biodiesel yield. effect of reaction temperature figure (3) shows the effect of reaction temperature on the yield of biodiesel at a constant methanol-to-oil ratio and catalyst loading. the yield of biodiesel highly increased as temperature increased from 45°c to 55°c. maximum yield was obtained at 58°c and the yield started to decrease slightly from 58°c to 65°c due to the vaporization of methanol resulting in soap formation. the boiling point of methanol is 64.7°c. increasing reaction temperature above this point leads to methanol loss by evaporation and decreases the conversion efficiency of the reaction. at 45°c, the yield is about 75°c. effect of catalyst loading figure (4) shows the effect of catalyst loading on the yield of biodiesel at a constant methanol-to-oil ratio and temperature. as the amount of catalyst increased from 0.5% to 1.0%, the yield of biodiesel increased from 89% to 94% and the yield starts to decrease slightly as the amount of catalyst increased from 1.0% to 1.5% due to the formation of soap and emulsion. at a lower amount of catalyst (0.5%), the yield of biodiesel decreased due to the incomplete conversion of triglycerides of oil to fatty acid methyl ester. optimization of transesterification process parameters using the response surface method (rsm) the response surface method determined the optimum value of process variables that maximize the yield of the product and minimize production cost table viii showed that response surface method found 15 solutions and selected the optimum values to minimize the economic cost of temperature, methanol, and catalyst required for the reaction and to maximize the yield of biodiesel. the optimum yield of biodiesel (83.772%) was observed at a temperature of 51.537 and catalyst load of 0.500 wt.%. conclusions biodiesel is a promising biofuel that is synthesized by the transesterification of vegetable oils and animal fats. in this study, biodiesel was synthesized from moringa stenopetala seed oil using an alkali catalyst. the effect of methanol to oil ratio, reaction temperature, and catalyst weight on the yield and quality of biodiesel have been studied. biodiesel produced was characterized according to international fuel testing standards methods. the optimization of process parameters was carried out using response surface method (rsm). the experimental result showed that the highest yield of biodiesel was 94% and this result was obtained at an optimum value of temperature 55°c, methanol to oil ratio of 6:1, and catalyst load of 1.0%. increasing methanol to oil ratio, temperature, and catalyst load up to the optimum point increased the yield of biodiesel. however, further increase of the parameters above the optimum point decreased the yield of biodiesel. the temperature has the highest significant effect while the catalyst load has a lower effect. besides to characterization of different basic fuel properties of it, biodiesel can be blended with petrol-diesel at different percentages and applied in compression ignition engine to evaluate the effect of using a blend of biodiesel using different parameters such as engine power, brake thermal efficiency, specific fuel consumption, exhaust gas temperature, and greenhouse gas temperature and gas emission. however, the performance analysis of the blend of biodiesel with petrol diesel in a compression ignition engine was not done due to a lack of laboratory setup and equipment required to measure these parameters. this study did not compare biodiesel with diesel fuels used in diesel engines. moreover, it did not characterize the blend of biodiesel with petroleum fuels and did not compare biodiesel produced from other feedstocks other than moringa stenopetala. thus, further research should be done on these areas. generally, it can be concluded that moringa stenopetala is a promising alternative feedstock for biodiesel production for the reasons: it does not affect food security, has a good oil content, and can be harvested throughout the year. the biodiesel produced meets the standard fuel quality and international standard specifications. acknowledgment the authors are thankful to addis ababa institute of technology, addis ababa university, ethiopian environment and forest research institute, college of natural and computational science, addis ababa university, and ethiopian geological survey for their technical support. references agarwal ak and das lm (2001), biodiesel development and characterization for use as a fuel in compression in ignition engines, j eng gas turbines power. 123(2): 440-447. doi: 10.1115/1.1364522 atabani ae, silitonga as, ong hc, mahila tm, masjuki hh, irfan a and fayaz h (2013), non-edible vegetable oils: evaluation of oil extraction, fatty acid compositions, biodiesel production, characteristics, engine performance and emissions production, ren. sus. energy rev. 18: 211-245. doi: 10.1016/ j.rser.2012.10.013 atabani ae, mahlia tm, ifran a, masjuki hh, chong wt and keat tl (2013), investigation of physical and chemical properties of potential edible and non-edible feedstocks for biodiesel production, a comparative analysis, ren. sus. energy rev. 21: 749-55. doi: 10.1016/j.rser.2013.01.027 ayerza hr (2012), seed and oil yields of moringa oleifera variety periyakalum-1 introduced for oil production in four ecosystems of south america, ind. crops prod. 36: 70-73. doi: 10.1016/j.indcrop.2011.08.008 azad a, rasul m, khan k, subhash cs and rubayat i (2015), prospect of moringa seed oil is a sustainable biodiesel fuel in australia, procedia engineering. 105: 601-606, doi: 10.1016/j.proeng. 2015.05.037 choi c and reitz r (1999), a numerical analysis of emission characteristics of biodiesel blended fuels, j eng gas turbines power 121(1): 31-37. doi: 10.1115/1. 2816309 demirbas a (2005), potential applications of renewable energy sources, biomasscombustion problems in boiler power systems, and combustion-related environmentalissues, progress in energy and combustion sci. 31: 171-192. doi: 10.1016/j.pecs. 2005.02.002 demshemino si, donnel ps, muhamma fy, niwadike and okoro ln (2013), comparative analysis of biodiesel and petroleum diesel, international journal of education and research 1(8): 2-5. eman na and cadence it (2013), characterization of biodiesel produced from palm oilvia base-catalyzed transesterification, procedia engineering. 53: 7-12. doi: 10.1016/j.proeng.2013.02.002 gemeda t and desta n (2020), pre-extension demonstration of moringa preparation and utilization methods in east shoa zones of oromia, ethiopia, journal of biomaterials. 4(1): 17-22. doi: 10.11648/j.jb. 20200401.12 gemechu ys (2021), production and characterization of biodiesel from moringa stenopetala seed oil via catalytic transesterification process, thesis work at addis ababa university institute of technology, addis ababa, ethiopia. hamza ta and azmach nn (2017), the miraculous moringa trees: from a nutritionaland medicinal point of view in tropical regions, journal of medicinal plants studies 5 (4): 151-162. jayed mh, masjuki hh, kalam ma, mahlia tm, husnawan m and liaquat am (2011), prospects of dedicated biodiesel engine vehicles in malaysia and indonesia, ren. sus. ener. rev. 15: 220-235. doi: 10.1016/j.rser.2010.09.002 kafuku g and mbarawa m (2010), alkaline-catalyzed biodiesel production from moringa oleifera oil with optimized production parameters, applied energy. 87 (8): 2561-2565. doi:10.1016/j. apenergy. 2010.02.026 marchetti jm and yadessa gk (2012), a review of oil extraction from plant seeds for biodiesel production, ims energy. 5(4): 316-340. doi: 10.3934/energy. 2017.2.316 mahmudul h, hagos r, mamat a, abdul a and ishak ra (2017), production, characterization and performance of biodiesel as an alternative fuel in diesel engines, renewable and sustainable energy reviews 72(c): 497-509. doi: 10.1016/j.rser.2017.01.001 piyush n, subramanian ka and dastidar mg (2013), production and characterization of biodieselfrom algae, fuel processing technology. 120: 79-88. doi: 10.1016/j.fuproc.2013.12.003 raj s and bhandari m (2017), comparison of methods of production of biodiesel from jatropha curcas, journal of biofuel. 8(2): 58-80. rao pv (2011), experimental investigations on the influence of properties of jatropha biodiesel on performance, combustion, and emission characteristics of di–ci engines, world acad. sci. eng. technol. 5(3): 855-868. sreepada h and vijayalaxmi h (2013), an overview of moringa production in ethiopia, international journal of science and research 4(4): 2319-7064. doi: 10.36106/ijsr seema r and meena b (2017), comparison of methods of biodiesel productionfrom jatropha curcas, journal of biofuels. 8(2): 58-80. its advantages is it is considered a great natural cosmetic emollient and has high oxidative stability (ayerza, 2012). moringa plant is a high-value tree of the moringaceae family. it consists of 13 species highly distributed in africa and asia (hamza and azmach, 2017). moringa is particularly suitable for dry regions since it can be grown using rainwater without expensive irrigation techniques. moringa has been given less attention and ignored tree by communities to utilize it in different ways (gemeda and desta, 2020). flowering begins within the first six months. moringa stenopetala seed is an available and underutilized resource. ethiopia has a comfortable environment for mooring stenopetala plantations. many parts of the country particularly southern parts such as gamo goffa, sidama wolayitta, konso, and darashe have planted moringa in their garden and farmland (sreepada and vijayalaxmi, 2013). thus, this study investigated that moringa stenopetala seed oil is a potential industrial feedstock for biodiesel production as an alternative energy source. materials and methods the sample of moringa seed was collected from the gamo goffa zone, arba minch area of ethiopia. the seed sample was dried and milled to reduce the particle size. then, 80 g of sample was measured and put into the soxhlet apparatus thimble. then, it was placed in a 500 ml capacity soxhlet chamber. 400 ml solvent (hexane) was used for the extraction at different temperatures for 3 hrs. to 5 hrs. the extraction was conducted at 70°c, 75°c, and 80°c by varying extraction time to get the maximum possible oil yield. the soxhlet extraction method was selected since it results in high oil yield, is quick, the solvent can be reused, and is low cost (sreepada and vijayalaxmi, 2013). the unwanted substances were removed by evaporation and degumming. evaporation was used to separate hexane from table iv. standard methods (astm d 6751 and en 14214) for physical and chemical properties of biodiesel property standard methods specific gravity en 14214 kinematic viscosity astm d445 saponification value astm d5558 acid value en 14104 calorific value astm d240 flash and fire point astm d93 moisture content en 14774 -1 iodine value en 14111 pour point astm d5771 cloud point astm d6950 factor 1 factor 2 factor 3 response 1 std run oil ratio a: methanol to b: c: catalyst temperature loading yield °c wt.% % 10 1 6 65 0.5 86.67 3 2 3 65 1 78.18 13 3 6 55 1 93.81 2 4 9 45 1 78.18 9 5 6 45 0.5 76.36 4 6 9 65 1 81.82 12 7 6 65 1.5 88.34 8 8 9 55 1.5 85.45 15 9 6 55 1 93.84 7 10 3 55 1.5 80 5 11 3 55 0.5 72.71 11 12 6 45 1.5 76.67 14 13 6 55 1 94 17 14 6 55 1 93.27 16 15 6 55 1 93.92 6 16 9 55 0.5 83.63 1 17 3 45 1 76.67 table v. biodiesel yield response of experimental runs biodiesel from moringa stenopetala seed oil 58(1) 202340 the most common production technology of biodiesel is the transesterification process. transesterification is a chemical reaction between one mole of triglyceride with three moles of alcohol to produce fatty acid methyl ester and glycerol in the presence of a catalyst or without a catalyst. most transesterification reactions use ethanol or methanol alcohol. many studies show that methanol is more practically used as alcohol than ethanol. methanol is preferable due to its low cost and its physical and chemical advantages. another advantage of using methanol is the ease of separation of glycerin which can be achieved by simple decantation (marchetti and yadessa, 2012). various catalysts can be used in the process. however, it was confirmed that the transesterification reaction was completed very fast when alkali catalysts are used. after the transesterification reaction is completed, glycerol, catalyst, alcohol, and soap are separated from biodiesel. the factors affecting biodiesel yield and fuel quality are alcohol-to-oil ratios, temperature, catalyst loading, and reaction time (raj and bhandari, 2017). biodiesel is formed when triglyceride reacts with alcohol leaving glycerol as a byproduct as shown in figure 1. there are more than 300 vegetable oils identified as potential feedstocks for biodiesel production globally. the availability, characteristics, and variety of feedstocks make them promising ingredients for the sustainable production of biodiesel (piyush et al. 2013). researchers have proposed moringa seed oil as an alternative potential feedstock to produce biodiesel. however, there is a research gap that promotes this feedstock for industrial processing. moringa seed has an average of 35%-45% oil content with high oleic content of greater than 73% based on the type of the tree. moringa oil has many various industrial and homemade benefits. one of oil by rotary evaporation at 80°c. gum and wax were removed by a degumming method. then, biodiesel was synthesized by transesterification reaction using a homogenous catalyst (methanol) at different process parameters. experimental design the experimental design used for this study was a box behnken design standard using design expert 11.0 software. the experimental design was done using three variables and tree levels for a response surface method. 17 experimental runswere selected by design expert 11.0 software using the box behnken design standard method, with five central points per block. the main factors that affect biodiesel production by transesterification reaction are reaction time, reaction temperature, and alcohol-to-oil ratio (seema and meena, 2017). as indicated in table i, the overall production of biodiesel was carried out at optimum parameters of catalyst load of 0.5 to 1.5 wt.%, reaction temperature of 45 to 65°c, and methanol to oil ratio of 3 to 9. the other parameters, reaction time and mixing intensity were kept constant at 1 hour and 500 rpm for all experimental runs. a combination of three factors and three levels of experimental runs was conducted. there are 17 experimental runs determined bybox behnken’s design arrangement as shown in table ii. production and purification of the product the method used to produce biodiesel was a one-steptransesterification reaction. methanol was the alcohol selected for the transesterification reaction due to its availability, low cost, popularity, and ease of separation (demirbas, 2005). the catalyst selected for this study was the base catalyst (koh) since biodiesel can be produced at low temperatures and pressure reactions. moreover, it is a homogeneous base catalyst that results in high conversion, minimum side reactions, short reaction time, and high yield (marchetti and yadessa, 2012). though it has many advantages, the disadvantage of the catalyst used is it cannot be reused. when the reaction is completed, biodiesel and glycerol were separated by a separatory funnel after it settles for 24 hours. then, biodiesel was washed with hot distilled water to remove soap, remaining methanol, and wax. optimization of the process parameters using the response surface method (rsm). optimization aims to determine the optimum value of the factors that affect the transesterification process to produce the maximum possible biodiesel yield at a minimum production cost. this is done by minimizing the methanol to oil ratio, reaction temperature, and amount of catalyst used as indicated in table iii. characterization of biodiesel characterization of fuel is determining the physical and chemical properties (atabani et al. 2013). the physical and chemical properties of biodiesel were determined according to the american society for testing materials (astm d 6751) and european standard (en 14214) methods (demirbas, 2005). table iv showed the physical and chemical properties of biodiesel and the standard methods used to determine them. statistical analysis of experimental results data analysis of the experiment was done by design expert 11.0 software using box behnken design standard. the significance of experimental variables was obtained from analysis of variance (anova). results and discussions yield the maximum oil yield obtained at optimum conditions of temperature 80°c and extraction time 5 hours was 39.86 %. this result agreed with the average oil content of moringa stenopetala seed oil which is 35% 45% (ayerza, 2012), and this result also agreed with the previous reportof 38% which was reported by azad et al. (2015) and by gemechu (2021). the maximum yield of biodiesel was 94% and it was obtained at optimum process parameters of methanol to oil ratio 6:1, temperature 55°c, and catalyst loading 1.0%. the yield of biodiesel obtained agrees with the previous report of azad et al. (2015) which was 91%. the yield increased as transesterification parameters increased until the optimum value and decreased beyond the optimum value. at the lower value of parameters, the yield decreased due to the incomplete conversion of reactants to the product. table v showed the yield response of all experimental runs. characterization of biodiesel physical and chemical properties of biodiesel were evaluated using standard methods and the results were compared with astm and en standard methods and previous reports. density the value of the density of biodiesel was 874 kg/m3. this result is within the standard range of density (860 – 900 kg/m3) (demirbas, 2005) and agrees with the previous report by kafuku and mbarawa (2010) which was 900 kg/m3. higher density increases thesize of fuel droplets and causes higher emission of particulate matter and nox emission ina diesel engine while the lower density of fuel expands the efficiency of atomization (choi and reitz, 1999). kinematic viscosity the experimental result showed that the value of kinematic viscosity was 4.8 mm2/s. this result is within the range of the astm standard value of biodiesel which is 1.6-6 (eman and cadence, 2013; demirbas, 2005). highly viscous fuel is difficult to pump and operate in internal combustion engines while lower kinematic viscosity of fuels increases wear leakage due to insufficient lubrication (rao, 2011). acid value the value of an acid value obtained was 0.4 mm koh/g. this result agrees with the previous report (kafuku and mbarawa, 2010), with a value of 1.2 mmkoh/g. higher acid-value fuels need further acid treatment costs and it also lowers the quality of the fuels. in this study, the lower acid value of biodiesel indicates that it has higher fuel quality. calorific value the experimental result showed that the value of biodiesel was 10287 cal/ g or 43 mj/kj. this result agrees with the previous report of mahamudul et al. (2017) which was 39 mj/kg, and the previous report of agarwal and das (2001) which was 43.2 kj/kg. the result obtained is above the standard astm value which is 42-42.5 mj/kg. this result indicates the higher fuel quality of biodiesel. the calorific value obtained is similar to that of conventional diesel fuels. this is the novel result of this study. flash point the flash point obtained from the experimental result was 184°c. this result agrees with the standard astm value of biodiesel flash point which is greater than 130°c. from this study, the higher flash point of biodiesel indicates that it is safer to handle, store and transport the fuel (jayed et al. 2011). cetane number the value of the cetane number observed was 53. this result agrees with the standard astm value of the cetane number of biodiesel which is greater than 47 (demirbas, 2005). fuels with higher cetane number benefit the engine performance since the engine starts rapidly and run smoothly without causing much noise. cloud and pour point the experimental result showed that the cloud and pour points of biodiesel were 10°c and 1°c respectively. this result agrees with the previous report of kafuku and mbarawa (2010) which was 10°c and 3°c respectively. cloud and pour point of fuel indicates the fuel performance at low ambient temperature (agarwal and das, 2001). table vi showed the result of all main physicochemical properties of biodiesel synthesized. statistical analysis of experimental results analysis of variance (anova) for the quadratic model analysis of variance determines the significance of the experimental results using coded variables as indicated in table vii. the model f-value of 380.98 implies the model is significant. there is only a 0.01% chance that an f-value this large could occur due to noise. p-values less than 0.0500 indicate model terms are significant. in this case, a, b, c, a², b², c² are significant model terms. values greater than 0.1000 indicate the model terms are not significant. if there are many insignificant model terms (not counting those required to support hierarchy), model reduction may improve your model. the lack of fit f-value of 5.69 implies there is a 6.31% chance that a lack of fit f-value this large could occur due to noise. lack of fit is bad -we want the model to fit. this relatively low probability (<10%) is troubling. the coefficient estimate represents the expected change in response per unit change in factor value when all remaining factors are held constant. the intercept in an orthogonal design is the overall average response of all the runs. the coefficients are adjustments around that average based on the factor settings. when the factors are orthogonal the vifs are 1; vifs greater than 1 indicate multi-collinearity, and the higher the vif the more severe the correlation of factors. as a rough rule, vifs less than 10 are tolerable. the effect of process parameters on the yield of biodiesel effect of methanol to oil ratio figure. (2) shows the effect of methanol to oil ratio on biodiesel yield at constant temperature and catalyst loading. it showed that the yield of biodiesel increases as the methanol-to-oil ratio increases. increasing the methanol-to-oil ratio beyond the optimum value results in excess methanol which decreases the yield of biodiesel. the maximum yield of biodiesel (94%) was obtained at a methanol-to-oil ratio of 6: 1. therefore, this ratio was taken as an optimum value of the methanol-to-oil ratio. decreasing the methanol-to-oil ratio below the optimum value (3:1), decreased the conversion efficiency of the transesterification reaction and resulted in lower biodiesel yield. effect of reaction temperature figure (3) shows the effect of reaction temperature on the yield of biodiesel at a constant methanol-to-oil ratio and catalyst loading. the yield of biodiesel highly increased as temperature increased from 45°c to 55°c. maximum yield was obtained at 58°c and the yield started to decrease slightly from 58°c to 65°c due to the vaporization of methanol resulting in soap formation. the boiling point of methanol is 64.7°c. increasing reaction temperature above this point leads to methanol loss by evaporation and decreases the conversion efficiency of the reaction. at 45°c, the yield is about 75°c. effect of catalyst loading figure (4) shows the effect of catalyst loading on the yield of biodiesel at a constant methanol-to-oil ratio and temperature. as the amount of catalyst increased from 0.5% to 1.0%, the yield of biodiesel increased from 89% to 94% and the yield starts to decrease slightly as the amount of catalyst increased from 1.0% to 1.5% due to the formation of soap and emulsion. at a lower amount of catalyst (0.5%), the yield of biodiesel decreased due to the incomplete conversion of triglycerides of oil to fatty acid methyl ester. optimization of transesterification process parameters using the response surface method (rsm) the response surface method determined the optimum value of process variables that maximize the yield of the product and minimize production cost table viii showed that response surface method found 15 solutions and selected the optimum values to minimize the economic cost of temperature, methanol, and catalyst required for the reaction and to maximize the yield of biodiesel. the optimum yield of biodiesel (83.772%) was observed at a temperature of 51.537 and catalyst load of 0.500 wt.%. conclusions biodiesel is a promising biofuel that is synthesized by the transesterification of vegetable oils and animal fats. in this study, biodiesel was synthesized from moringa stenopetala seed oil using an alkali catalyst. the effect of methanol to oil ratio, reaction temperature, and catalyst weight on the yield and quality of biodiesel have been studied. biodiesel produced was characterized according to international fuel testing standards methods. the optimization of process parameters was carried out using response surface method (rsm). the experimental result showed that the highest yield of biodiesel was 94% and this result was obtained at an optimum value of temperature 55°c, methanol to oil ratio of 6:1, and catalyst load of 1.0%. increasing methanol to oil ratio, temperature, and catalyst load up to the optimum point increased the yield of biodiesel. however, further increase of the parameters above the optimum point decreased the yield of biodiesel. the temperature has the highest significant effect while the catalyst load has a lower effect. besides to characterization of different basic fuel properties of it, biodiesel can be blended with petrol-diesel at different percentages and applied in compression ignition engine to evaluate the effect of using a blend of biodiesel using different parameters such as engine power, brake thermal efficiency, specific fuel consumption, exhaust gas temperature, and greenhouse gas temperature and gas emission. however, the performance analysis of the blend of biodiesel with petrol diesel in a compression ignition engine was not done due to a lack of laboratory setup and equipment required to measure these parameters. this study did not compare biodiesel with diesel fuels used in diesel engines. moreover, it did not characterize the blend of biodiesel with petroleum fuels and did not compare biodiesel produced from other feedstocks other than moringa stenopetala. thus, further research should be done on these areas. generally, it can be concluded that moringa stenopetala is a promising alternative feedstock for biodiesel production for the reasons: it does not affect food security, has a good oil content, and can be harvested throughout the year. the biodiesel produced meets the standard fuel quality and international standard specifications. acknowledgment the authors are thankful to addis ababa institute of technology, addis ababa university, ethiopian environment and forest research institute, college of natural and computational science, addis ababa university, and ethiopian geological survey for their technical support. references agarwal ak and das lm (2001), biodiesel development and characterization for use as a fuel in compression in ignition engines, j eng gas turbines power. 123(2): 440-447. doi: 10.1115/1.1364522 atabani ae, silitonga as, ong hc, mahila tm, masjuki hh, irfan a and fayaz h (2013), non-edible vegetable oils: evaluation of oil extraction, fatty acid compositions, biodiesel production, characteristics, engine performance and emissions production, ren. sus. energy rev. 18: 211-245. doi: 10.1016/ j.rser.2012.10.013 atabani ae, mahlia tm, ifran a, masjuki hh, chong wt and keat tl (2013), investigation of physical and chemical properties of potential edible and non-edible feedstocks for biodiesel production, a comparative analysis, ren. sus. energy rev. 21: 749-55. doi: 10.1016/j.rser.2013.01.027 ayerza hr (2012), seed and oil yields of moringa oleifera variety periyakalum-1 introduced for oil production in four ecosystems of south america, ind. crops prod. 36: 70-73. doi: 10.1016/j.indcrop.2011.08.008 azad a, rasul m, khan k, subhash cs and rubayat i (2015), prospect of moringa seed oil is a sustainable biodiesel fuel in australia, procedia engineering. 105: 601-606, doi: 10.1016/j.proeng. 2015.05.037 choi c and reitz r (1999), a numerical analysis of emission characteristics of biodiesel blended fuels, j eng gas turbines power 121(1): 31-37. doi: 10.1115/1. 2816309 demirbas a (2005), potential applications of renewable energy sources, biomasscombustion problems in boiler power systems, and combustion-related environmentalissues, progress in energy and combustion sci. 31: 171-192. doi: 10.1016/j.pecs. 2005.02.002 demshemino si, donnel ps, muhamma fy, niwadike and okoro ln (2013), comparative analysis of biodiesel and petroleum diesel, international journal of education and research 1(8): 2-5. eman na and cadence it (2013), characterization of biodiesel produced from palm oilvia base-catalyzed transesterification, procedia engineering. 53: 7-12. doi: 10.1016/j.proeng.2013.02.002 gemeda t and desta n (2020), pre-extension demonstration of moringa preparation and utilization methods in east shoa zones of oromia, ethiopia, journal of biomaterials. 4(1): 17-22. doi: 10.11648/j.jb. 20200401.12 gemechu ys (2021), production and characterization of biodiesel from moringa stenopetala seed oil via catalytic transesterification process, thesis work at addis ababa university institute of technology, addis ababa, ethiopia. hamza ta and azmach nn (2017), the miraculous moringa trees: from a nutritionaland medicinal point of view in tropical regions, journal of medicinal plants studies 5 (4): 151-162. jayed mh, masjuki hh, kalam ma, mahlia tm, husnawan m and liaquat am (2011), prospects of dedicated biodiesel engine vehicles in malaysia and indonesia, ren. sus. ener. rev. 15: 220-235. doi: 10.1016/j.rser.2010.09.002 kafuku g and mbarawa m (2010), alkaline-catalyzed biodiesel production from moringa oleifera oil with optimized production parameters, applied energy. 87 (8): 2561-2565. doi:10.1016/j. apenergy. 2010.02.026 marchetti jm and yadessa gk (2012), a review of oil extraction from plant seeds for biodiesel production, ims energy. 5(4): 316-340. doi: 10.3934/energy. 2017.2.316 mahmudul h, hagos r, mamat a, abdul a and ishak ra (2017), production, characterization and performance of biodiesel as an alternative fuel in diesel engines, renewable and sustainable energy reviews 72(c): 497-509. doi: 10.1016/j.rser.2017.01.001 piyush n, subramanian ka and dastidar mg (2013), production and characterization of biodieselfrom algae, fuel processing technology. 120: 79-88. doi: 10.1016/j.fuproc.2013.12.003 raj s and bhandari m (2017), comparison of methods of production of biodiesel from jatropha curcas, journal of biofuel. 8(2): 58-80. rao pv (2011), experimental investigations on the influence of properties of jatropha biodiesel on performance, combustion, and emission characteristics of di–ci engines, world acad. sci. eng. technol. 5(3): 855-868. sreepada h and vijayalaxmi h (2013), an overview of moringa production in ethiopia, international journal of science and research 4(4): 2319-7064. doi: 10.36106/ijsr seema r and meena b (2017), comparison of methods of biodiesel productionfrom jatropha curcas, journal of biofuels. 8(2): 58-80. its advantages is it is considered a great natural cosmetic emollient and has high oxidative stability (ayerza, 2012). moringa plant is a high-value tree of the moringaceae family. it consists of 13 species highly distributed in africa and asia (hamza and azmach, 2017). moringa is particularly suitable for dry regions since it can be grown using rainwater without expensive irrigation techniques. moringa has been given less attention and ignored tree by communities to utilize it in different ways (gemeda and desta, 2020). flowering begins within the first six months. moringa stenopetala seed is an available and underutilized resource. ethiopia has a comfortable environment for mooring stenopetala plantations. many parts of the country particularly southern parts such as gamo goffa, sidama wolayitta, konso, and darashe have planted moringa in their garden and farmland (sreepada and vijayalaxmi, 2013). thus, this study investigated that moringa stenopetala seed oil is a potential industrial feedstock for biodiesel production as an alternative energy source. materials and methods the sample of moringa seed was collected from the gamo goffa zone, arba minch area of ethiopia. the seed sample was dried and milled to reduce the particle size. then, 80 g of sample was measured and put into the soxhlet apparatus thimble. then, it was placed in a 500 ml capacity soxhlet chamber. 400 ml solvent (hexane) was used for the extraction at different temperatures for 3 hrs. to 5 hrs. the extraction was conducted at 70°c, 75°c, and 80°c by varying extraction time to get the maximum possible oil yield. the soxhlet extraction method was selected since it results in high oil yield, is quick, the solvent can be reused, and is low cost (sreepada and vijayalaxmi, 2013). the unwanted substances were removed by evaporation and degumming. evaporation was used to separate hexane from table vi. summary of physicochemical properties of moringa stenopetala seed biodiesel property result unit standard method used moisture 1.4 % astm d4442-07 ph 7.9 density at 15°c 874 kg/m3 en 3675 kinematic viscosity at 22°c 4.8 mm2/s astm d445 acid value 0.4 mg koh/g astm d664 saponification value 196 mg koh/g free fatty acid 0.2 % iodine value 104.5 g i2 /100 g en 14111 calorific value 10,287 cal/g astm d240 flash point 184 °c astm d93 cetane number 53 astm d 6751 fire point 190 °c astm d93 specific gravity 0.874 g/mole en 14214 cloud point 10 °c astm d6950 pour point 1 °c astm d5771 shage and ali 41 the most common production technology of biodiesel is the transesterification process. transesterification is a chemical reaction between one mole of triglyceride with three moles of alcohol to produce fatty acid methyl ester and glycerol in the presence of a catalyst or without a catalyst. most transesterification reactions use ethanol or methanol alcohol. many studies show that methanol is more practically used as alcohol than ethanol. methanol is preferable due to its low cost and its physical and chemical advantages. another advantage of using methanol is the ease of separation of glycerin which can be achieved by simple decantation (marchetti and yadessa, 2012). various catalysts can be used in the process. however, it was confirmed that the transesterification reaction was completed very fast when alkali catalysts are used. after the transesterification reaction is completed, glycerol, catalyst, alcohol, and soap are separated from biodiesel. the factors affecting biodiesel yield and fuel quality are alcohol-to-oil ratios, temperature, catalyst loading, and reaction time (raj and bhandari, 2017). biodiesel is formed when triglyceride reacts with alcohol leaving glycerol as a byproduct as shown in figure 1. there are more than 300 vegetable oils identified as potential feedstocks for biodiesel production globally. the availability, characteristics, and variety of feedstocks make them promising ingredients for the sustainable production of biodiesel (piyush et al. 2013). researchers have proposed moringa seed oil as an alternative potential feedstock to produce biodiesel. however, there is a research gap that promotes this feedstock for industrial processing. moringa seed has an average of 35%-45% oil content with high oleic content of greater than 73% based on the type of the tree. moringa oil has many various industrial and homemade benefits. one of oil by rotary evaporation at 80°c. gum and wax were removed by a degumming method. then, biodiesel was synthesized by transesterification reaction using a homogenous catalyst (methanol) at different process parameters. experimental design the experimental design used for this study was a box behnken design standard using design expert 11.0 software. the experimental design was done using three variables and tree levels for a response surface method. 17 experimental runswere selected by design expert 11.0 software using the box behnken design standard method, with five central points per block. the main factors that affect biodiesel production by transesterification reaction are reaction time, reaction temperature, and alcohol-to-oil ratio (seema and meena, 2017). as indicated in table i, the overall production of biodiesel was carried out at optimum parameters of catalyst load of 0.5 to 1.5 wt.%, reaction temperature of 45 to 65°c, and methanol to oil ratio of 3 to 9. the other parameters, reaction time and mixing intensity were kept constant at 1 hour and 500 rpm for all experimental runs. a combination of three factors and three levels of experimental runs was conducted. there are 17 experimental runs determined bybox behnken’s design arrangement as shown in table ii. production and purification of the product the method used to produce biodiesel was a one-steptransesterification reaction. methanol was the alcohol selected for the transesterification reaction due to its availability, low cost, popularity, and ease of separation (demirbas, 2005). the catalyst selected for this study was the base catalyst (koh) since biodiesel can be produced at low temperatures and pressure reactions. moreover, it is a homogeneous base catalyst that results in high conversion, minimum side reactions, short reaction time, and high yield (marchetti and yadessa, 2012). though it has many advantages, the disadvantage of the catalyst used is it cannot be reused. when the reaction is completed, biodiesel and glycerol were separated by a separatory funnel after it settles for 24 hours. then, biodiesel was washed with hot distilled water to remove soap, remaining methanol, and wax. optimization of the process parameters using the response surface method (rsm). optimization aims to determine the optimum value of the factors that affect the transesterification process to produce the maximum possible biodiesel yield at a minimum production cost. this is done by minimizing the methanol to oil ratio, reaction temperature, and amount of catalyst used as indicated in table iii. characterization of biodiesel characterization of fuel is determining the physical and chemical properties (atabani et al. 2013). the physical and chemical properties of biodiesel were determined according to the american society for testing materials (astm d 6751) and european standard (en 14214) methods (demirbas, 2005). table iv showed the physical and chemical properties of biodiesel and the standard methods used to determine them. statistical analysis of experimental results data analysis of the experiment was done by design expert 11.0 software using box behnken design standard. the significance of experimental variables was obtained from analysis of variance (anova). results and discussions yield the maximum oil yield obtained at optimum conditions of temperature 80°c and extraction time 5 hours was 39.86 %. this result agreed with the average oil content of moringa stenopetala seed oil which is 35% 45% (ayerza, 2012), and this result also agreed with the previous reportof 38% which was reported by azad et al. (2015) and by gemechu (2021). the maximum yield of biodiesel was 94% and it was obtained at optimum process parameters of methanol to oil ratio 6:1, temperature 55°c, and catalyst loading 1.0%. the yield of biodiesel obtained agrees with the previous report of azad et al. (2015) which was 91%. the yield increased as transesterification parameters increased until the optimum value and decreased beyond the optimum value. at the lower value of parameters, the yield decreased due to the incomplete conversion of reactants to the product. table v showed the yield response of all experimental runs. characterization of biodiesel physical and chemical properties of biodiesel were evaluated using standard methods and the results were compared with astm and en standard methods and previous reports. density the value of the density of biodiesel was 874 kg/m3. this result is within the standard range of density (860 – 900 kg/m3) (demirbas, 2005) and agrees with the previous report by kafuku and mbarawa (2010) which was 900 kg/m3. higher density increases thesize of fuel droplets and causes higher emission of particulate matter and nox emission ina diesel engine while the lower density of fuel expands the efficiency of atomization (choi and reitz, 1999). kinematic viscosity the experimental result showed that the value of kinematic viscosity was 4.8 mm2/s. this result is within the range of the astm standard value of biodiesel which is 1.6-6 (eman and cadence, 2013; demirbas, 2005). highly viscous fuel is difficult to pump and operate in internal combustion engines while lower kinematic viscosity of fuels increases wear leakage due to insufficient lubrication (rao, 2011). acid value the value of an acid value obtained was 0.4 mm koh/g. this result agrees with the previous report (kafuku and mbarawa, 2010), with a value of 1.2 mmkoh/g. higher acid-value fuels need further acid treatment costs and it also lowers the quality of the fuels. in this study, the lower acid value of biodiesel indicates that it has higher fuel quality. calorific value the experimental result showed that the value of biodiesel was 10287 cal/ g or 43 mj/kj. this result agrees with the previous report of mahamudul et al. (2017) which was 39 mj/kg, and the previous report of agarwal and das (2001) which was 43.2 kj/kg. the result obtained is above the standard astm value which is 42-42.5 mj/kg. this result indicates the higher fuel quality of biodiesel. the calorific value obtained is similar to that of conventional diesel fuels. this is the novel result of this study. flash point the flash point obtained from the experimental result was 184°c. this result agrees with the standard astm value of biodiesel flash point which is greater than 130°c. from this study, the higher flash point of biodiesel indicates that it is safer to handle, store and transport the fuel (jayed et al. 2011). cetane number the value of the cetane number observed was 53. this result agrees with the standard astm value of the cetane number of biodiesel which is greater than 47 (demirbas, 2005). fuels with higher cetane number benefit the engine performance since the engine starts rapidly and run smoothly without causing much noise. cloud and pour point the experimental result showed that the cloud and pour points of biodiesel were 10°c and 1°c respectively. this result agrees with the previous report of kafuku and mbarawa (2010) which was 10°c and 3°c respectively. cloud and pour point of fuel indicates the fuel performance at low ambient temperature (agarwal and das, 2001). table vi showed the result of all main physicochemical properties of biodiesel synthesized. statistical analysis of experimental results analysis of variance (anova) for the quadratic model analysis of variance determines the significance of the experimental results using coded variables as indicated in table vii. the model f-value of 380.98 implies the model is significant. there is only a 0.01% chance that an f-value this large could occur due to noise. p-values less than 0.0500 indicate model terms are significant. in this case, a, b, c, a², b², c² are significant model terms. values greater than 0.1000 indicate the model terms are not significant. if there are many insignificant model terms (not counting those required to support hierarchy), model reduction may improve your model. the lack of fit f-value of 5.69 implies there is a 6.31% chance that a lack of fit f-value this large could occur due to noise. lack of fit is bad -we want the model to fit. this relatively low probability (<10%) is troubling. the coefficient estimate represents the expected change in response per unit change in factor value when all remaining factors are held constant. the intercept in an orthogonal design is the overall average response of all the runs. the coefficients are adjustments around that average based on the factor settings. when the factors are orthogonal the vifs are 1; vifs greater than 1 indicate multi-collinearity, and the higher the vif the more severe the correlation of factors. as a rough rule, vifs less than 10 are tolerable. the effect of process parameters on the yield of biodiesel effect of methanol to oil ratio figure. (2) shows the effect of methanol to oil ratio on biodiesel yield at constant temperature and catalyst loading. it showed that the yield of biodiesel increases as the methanol-to-oil ratio increases. increasing the methanol-to-oil ratio beyond the optimum value results in excess methanol which decreases the yield of biodiesel. the maximum yield of biodiesel (94%) was obtained at a methanol-to-oil ratio of 6: 1. therefore, this ratio was taken as an optimum value of the methanol-to-oil ratio. decreasing the methanol-to-oil ratio below the optimum value (3:1), decreased the conversion efficiency of the transesterification reaction and resulted in lower biodiesel yield. effect of reaction temperature figure (3) shows the effect of reaction temperature on the yield of biodiesel at a constant methanol-to-oil ratio and catalyst loading. the yield of biodiesel highly increased as temperature increased from 45°c to 55°c. maximum yield was obtained at 58°c and the yield started to decrease slightly from 58°c to 65°c due to the vaporization of methanol resulting in soap formation. the boiling point of methanol is 64.7°c. increasing reaction temperature above this point leads to methanol loss by evaporation and decreases the conversion efficiency of the reaction. at 45°c, the yield is about 75°c. effect of catalyst loading figure (4) shows the effect of catalyst loading on the yield of biodiesel at a constant methanol-to-oil ratio and temperature. as the amount of catalyst increased from 0.5% to 1.0%, the yield of biodiesel increased from 89% to 94% and the yield starts to decrease slightly as the amount of catalyst increased from 1.0% to 1.5% due to the formation of soap and emulsion. at a lower amount of catalyst (0.5%), the yield of biodiesel decreased due to the incomplete conversion of triglycerides of oil to fatty acid methyl ester. optimization of transesterification process parameters using the response surface method (rsm) the response surface method determined the optimum value of process variables that maximize the yield of the product and minimize production cost table viii showed that response surface method found 15 solutions and selected the optimum values to minimize the economic cost of temperature, methanol, and catalyst required for the reaction and to maximize the yield of biodiesel. the optimum yield of biodiesel (83.772%) was observed at a temperature of 51.537 and catalyst load of 0.500 wt.%. conclusions biodiesel is a promising biofuel that is synthesized by the transesterification of vegetable oils and animal fats. in this study, biodiesel was synthesized from moringa stenopetala seed oil using an alkali catalyst. the effect of methanol to oil ratio, reaction temperature, and catalyst weight on the yield and quality of biodiesel have been studied. biodiesel produced was characterized according to international fuel testing standards methods. the optimization of process parameters was carried out using response surface method (rsm). the experimental result showed that the highest yield of biodiesel was 94% and this result was obtained at an optimum value of temperature 55°c, methanol to oil ratio of 6:1, and catalyst load of 1.0%. increasing methanol to oil ratio, temperature, and catalyst load up to the optimum point increased the yield of biodiesel. however, further increase of the parameters above the optimum point decreased the yield of biodiesel. the temperature has the highest significant effect while the catalyst load has a lower effect. besides to characterization of different basic fuel properties of it, biodiesel can be blended with petrol-diesel at different percentages and applied in compression ignition engine to evaluate the effect of using a blend of biodiesel using different parameters such as engine power, brake thermal efficiency, specific fuel consumption, exhaust gas temperature, and greenhouse gas temperature and gas emission. however, the performance analysis of the blend of biodiesel with petrol diesel in a compression ignition engine was not done due to a lack of laboratory setup and equipment required to measure these parameters. this study did not compare biodiesel with diesel fuels used in diesel engines. moreover, it did not characterize the blend of biodiesel with petroleum fuels and did not compare biodiesel produced from other feedstocks other than moringa stenopetala. thus, further research should be done on these areas. generally, it can be concluded that moringa stenopetala is a promising alternative feedstock for biodiesel production for the reasons: it does not affect food security, has a good oil content, and can be harvested throughout the year. the biodiesel produced meets the standard fuel quality and international standard specifications. acknowledgment the authors are thankful to addis ababa institute of technology, addis ababa university, ethiopian environment and forest research institute, college of natural and computational science, addis ababa university, and ethiopian geological survey for their technical support. references agarwal ak and das lm (2001), biodiesel development and characterization for use as a fuel in compression in ignition engines, j eng gas turbines power. 123(2): 440-447. doi: 10.1115/1.1364522 atabani ae, silitonga as, ong hc, mahila tm, masjuki hh, irfan a and fayaz h (2013), non-edible vegetable oils: evaluation of oil extraction, fatty acid compositions, biodiesel production, characteristics, engine performance and emissions production, ren. sus. energy rev. 18: 211-245. doi: 10.1016/ j.rser.2012.10.013 atabani ae, mahlia tm, ifran a, masjuki hh, chong wt and keat tl (2013), investigation of physical and chemical properties of potential edible and non-edible feedstocks for biodiesel production, a comparative analysis, ren. sus. energy rev. 21: 749-55. doi: 10.1016/j.rser.2013.01.027 ayerza hr (2012), seed and oil yields of moringa oleifera variety periyakalum-1 introduced for oil production in four ecosystems of south america, ind. crops prod. 36: 70-73. doi: 10.1016/j.indcrop.2011.08.008 azad a, rasul m, khan k, subhash cs and rubayat i (2015), prospect of moringa seed oil is a sustainable biodiesel fuel in australia, procedia engineering. 105: 601-606, doi: 10.1016/j.proeng. 2015.05.037 choi c and reitz r (1999), a numerical analysis of emission characteristics of biodiesel blended fuels, j eng gas turbines power 121(1): 31-37. doi: 10.1115/1. 2816309 demirbas a (2005), potential applications of renewable energy sources, biomasscombustion problems in boiler power systems, and combustion-related environmentalissues, progress in energy and combustion sci. 31: 171-192. doi: 10.1016/j.pecs. 2005.02.002 demshemino si, donnel ps, muhamma fy, niwadike and okoro ln (2013), comparative analysis of biodiesel and petroleum diesel, international journal of education and research 1(8): 2-5. eman na and cadence it (2013), characterization of biodiesel produced from palm oilvia base-catalyzed transesterification, procedia engineering. 53: 7-12. doi: 10.1016/j.proeng.2013.02.002 gemeda t and desta n (2020), pre-extension demonstration of moringa preparation and utilization methods in east shoa zones of oromia, ethiopia, journal of biomaterials. 4(1): 17-22. doi: 10.11648/j.jb. 20200401.12 gemechu ys (2021), production and characterization of biodiesel from moringa stenopetala seed oil via catalytic transesterification process, thesis work at addis ababa university institute of technology, addis ababa, ethiopia. hamza ta and azmach nn (2017), the miraculous moringa trees: from a nutritionaland medicinal point of view in tropical regions, journal of medicinal plants studies 5 (4): 151-162. jayed mh, masjuki hh, kalam ma, mahlia tm, husnawan m and liaquat am (2011), prospects of dedicated biodiesel engine vehicles in malaysia and indonesia, ren. sus. ener. rev. 15: 220-235. doi: 10.1016/j.rser.2010.09.002 kafuku g and mbarawa m (2010), alkaline-catalyzed biodiesel production from moringa oleifera oil with optimized production parameters, applied energy. 87 (8): 2561-2565. doi:10.1016/j. apenergy. 2010.02.026 marchetti jm and yadessa gk (2012), a review of oil extraction from plant seeds for biodiesel production, ims energy. 5(4): 316-340. doi: 10.3934/energy. 2017.2.316 mahmudul h, hagos r, mamat a, abdul a and ishak ra (2017), production, characterization and performance of biodiesel as an alternative fuel in diesel engines, renewable and sustainable energy reviews 72(c): 497-509. doi: 10.1016/j.rser.2017.01.001 piyush n, subramanian ka and dastidar mg (2013), production and characterization of biodieselfrom algae, fuel processing technology. 120: 79-88. doi: 10.1016/j.fuproc.2013.12.003 raj s and bhandari m (2017), comparison of methods of production of biodiesel from jatropha curcas, journal of biofuel. 8(2): 58-80. rao pv (2011), experimental investigations on the influence of properties of jatropha biodiesel on performance, combustion, and emission characteristics of di–ci engines, world acad. sci. eng. technol. 5(3): 855-868. sreepada h and vijayalaxmi h (2013), an overview of moringa production in ethiopia, international journal of science and research 4(4): 2319-7064. doi: 10.36106/ijsr seema r and meena b (2017), comparison of methods of biodiesel productionfrom jatropha curcas, journal of biofuels. 8(2): 58-80. its advantages is it is considered a great natural cosmetic emollient and has high oxidative stability (ayerza, 2012). moringa plant is a high-value tree of the moringaceae family. it consists of 13 species highly distributed in africa and asia (hamza and azmach, 2017). moringa is particularly suitable for dry regions since it can be grown using rainwater without expensive irrigation techniques. moringa has been given less attention and ignored tree by communities to utilize it in different ways (gemeda and desta, 2020). flowering begins within the first six months. moringa stenopetala seed is an available and underutilized resource. ethiopia has a comfortable environment for mooring stenopetala plantations. many parts of the country particularly southern parts such as gamo goffa, sidama wolayitta, konso, and darashe have planted moringa in their garden and farmland (sreepada and vijayalaxmi, 2013). thus, this study investigated that moringa stenopetala seed oil is a potential industrial feedstock for biodiesel production as an alternative energy source. materials and methods the sample of moringa seed was collected from the gamo goffa zone, arba minch area of ethiopia. the seed sample was dried and milled to reduce the particle size. then, 80 g of sample was measured and put into the soxhlet apparatus thimble. then, it was placed in a 500 ml capacity soxhlet chamber. 400 ml solvent (hexane) was used for the extraction at different temperatures for 3 hrs. to 5 hrs. the extraction was conducted at 70°c, 75°c, and 80°c by varying extraction time to get the maximum possible oil yield. the soxhlet extraction method was selected since it results in high oil yield, is quick, the solvent can be reused, and is low cost (sreepada and vijayalaxmi, 2013). the unwanted substances were removed by evaporation and degumming. evaporation was used to separate hexane from table vii. analysis of variance (anova) source sum of squares df mean square f-value p-value model 1316.65 9 146.29 380.98 < 0.0001 significant a-methanol to oil ratio 35.15 1 35.15 91.55 < 0.0001 b-temperature 332.56 1 332.56 866.06 < 0.0001 c-catalyst loading 7.55 1 7.55 19.65 0.0030 ab 0.6972 1 0.6972 1.82 0.2198 ac 0.3481 1 0.3481 0.9065 0.3727 bc 0.0380 1 0.0380 0.0990 0.7622 a² 393.68 1 393.68 1025.23 < 0.0001 b² 458.66 1 458.66 1194.44 < 0.0001 c² 16.58 1 16.58 43.18 0.0003 residual 2.69 7 0.3840 lack of fit 2.18 3 0.7259 5.69 0.0631 not significant pure error 0.5101 4 0.1275 cor total 1319.33 16 biodiesel from moringa stenopetala seed oil42 58(1) 2023 the most common production technology of biodiesel is the transesterification process. transesterification is a chemical reaction between one mole of triglyceride with three moles of alcohol to produce fatty acid methyl ester and glycerol in the presence of a catalyst or without a catalyst. most transesterification reactions use ethanol or methanol alcohol. many studies show that methanol is more practically used as alcohol than ethanol. methanol is preferable due to its low cost and its physical and chemical advantages. another advantage of using methanol is the ease of separation of glycerin which can be achieved by simple decantation (marchetti and yadessa, 2012). various catalysts can be used in the process. however, it was confirmed that the transesterification reaction was completed very fast when alkali catalysts are used. after the transesterification reaction is completed, glycerol, catalyst, alcohol, and soap are separated from biodiesel. the factors affecting biodiesel yield and fuel quality are alcohol-to-oil ratios, temperature, catalyst loading, and reaction time (raj and bhandari, 2017). biodiesel is formed when triglyceride reacts with alcohol leaving glycerol as a byproduct as shown in figure 1. there are more than 300 vegetable oils identified as potential feedstocks for biodiesel production globally. the availability, characteristics, and variety of feedstocks make them promising ingredients for the sustainable production of biodiesel (piyush et al. 2013). researchers have proposed moringa seed oil as an alternative potential feedstock to produce biodiesel. however, there is a research gap that promotes this feedstock for industrial processing. moringa seed has an average of 35%-45% oil content with high oleic content of greater than 73% based on the type of the tree. moringa oil has many various industrial and homemade benefits. one of oil by rotary evaporation at 80°c. gum and wax were removed by a degumming method. then, biodiesel was synthesized by transesterification reaction using a homogenous catalyst (methanol) at different process parameters. experimental design the experimental design used for this study was a box behnken design standard using design expert 11.0 software. the experimental design was done using three variables and tree levels for a response surface method. 17 experimental runswere selected by design expert 11.0 software using the box behnken design standard method, with five central points per block. the main factors that affect biodiesel production by transesterification reaction are reaction time, reaction temperature, and alcohol-to-oil ratio (seema and meena, 2017). as indicated in table i, the overall production of biodiesel was carried out at optimum parameters of catalyst load of 0.5 to 1.5 wt.%, reaction temperature of 45 to 65°c, and methanol to oil ratio of 3 to 9. the other parameters, reaction time and mixing intensity were kept constant at 1 hour and 500 rpm for all experimental runs. a combination of three factors and three levels of experimental runs was conducted. there are 17 experimental runs determined bybox behnken’s design arrangement as shown in table ii. production and purification of the product the method used to produce biodiesel was a one-steptransesterification reaction. methanol was the alcohol selected for the transesterification reaction due to its availability, low cost, popularity, and ease of separation (demirbas, 2005). the catalyst selected for this study was the base catalyst (koh) since biodiesel can be produced at low temperatures and pressure reactions. moreover, it is a homogeneous base catalyst that results in high conversion, minimum side reactions, short reaction time, and high yield (marchetti and yadessa, 2012). though it has many advantages, the disadvantage of the catalyst used is it cannot be reused. when the reaction is completed, biodiesel and glycerol were separated by a separatory funnel after it settles for 24 hours. then, biodiesel was washed with hot distilled water to remove soap, remaining methanol, and wax. optimization of the process parameters using the response surface method (rsm). optimization aims to determine the optimum value of the factors that affect the transesterification process to produce the maximum possible biodiesel yield at a minimum production cost. this is done by minimizing the methanol to oil ratio, reaction temperature, and amount of catalyst used as indicated in table iii. characterization of biodiesel characterization of fuel is determining the physical and chemical properties (atabani et al. 2013). the physical and chemical properties of biodiesel were determined according to the american society for testing materials (astm d 6751) and european standard (en 14214) methods (demirbas, 2005). table iv showed the physical and chemical properties of biodiesel and the standard methods used to determine them. statistical analysis of experimental results data analysis of the experiment was done by design expert 11.0 software using box behnken design standard. the significance of experimental variables was obtained from analysis of variance (anova). results and discussions yield the maximum oil yield obtained at optimum conditions of temperature 80°c and extraction time 5 hours was 39.86 %. this result agreed with the average oil content of moringa stenopetala seed oil which is 35% 45% (ayerza, 2012), and this result also agreed with the previous reportof 38% which was reported by azad et al. (2015) and by gemechu (2021). the maximum yield of biodiesel was 94% and it was obtained at optimum process parameters of methanol to oil ratio 6:1, temperature 55°c, and catalyst loading 1.0%. the yield of biodiesel obtained agrees with the previous report of azad et al. (2015) which was 91%. the yield increased as transesterification parameters increased until the optimum value and decreased beyond the optimum value. at the lower value of parameters, the yield decreased due to the incomplete conversion of reactants to the product. table v showed the yield response of all experimental runs. characterization of biodiesel physical and chemical properties of biodiesel were evaluated using standard methods and the results were compared with astm and en standard methods and previous reports. density the value of the density of biodiesel was 874 kg/m3. this result is within the standard range of density (860 – 900 kg/m3) (demirbas, 2005) and agrees with the previous report by kafuku and mbarawa (2010) which was 900 kg/m3. higher density increases thesize of fuel droplets and causes higher emission of particulate matter and nox emission ina diesel engine while the lower density of fuel expands the efficiency of atomization (choi and reitz, 1999). kinematic viscosity the experimental result showed that the value of kinematic viscosity was 4.8 mm2/s. this result is within the range of the astm standard value of biodiesel which is 1.6-6 (eman and cadence, 2013; demirbas, 2005). highly viscous fuel is difficult to pump and operate in internal combustion engines while lower kinematic viscosity of fuels increases wear leakage due to insufficient lubrication (rao, 2011). acid value the value of an acid value obtained was 0.4 mm koh/g. this result agrees with the previous report (kafuku and mbarawa, 2010), with a value of 1.2 mmkoh/g. higher acid-value fuels need further acid treatment costs and it also lowers the quality of the fuels. in this study, the lower acid value of biodiesel indicates that it has higher fuel quality. calorific value the experimental result showed that the value of biodiesel was 10287 cal/ g or 43 mj/kj. this result agrees with the previous report of mahamudul et al. (2017) which was 39 mj/kg, and the previous report of agarwal and das (2001) which was 43.2 kj/kg. the result obtained is above the standard astm value which is 42-42.5 mj/kg. this result indicates the higher fuel quality of biodiesel. the calorific value obtained is similar to that of conventional diesel fuels. this is the novel result of this study. flash point the flash point obtained from the experimental result was 184°c. this result agrees with the standard astm value of biodiesel flash point which is greater than 130°c. from this study, the higher flash point of biodiesel indicates that it is safer to handle, store and transport the fuel (jayed et al. 2011). cetane number the value of the cetane number observed was 53. this result agrees with the standard astm value of the cetane number of biodiesel which is greater than 47 (demirbas, 2005). fuels with higher cetane number benefit the engine performance since the engine starts rapidly and run smoothly without causing much noise. cloud and pour point the experimental result showed that the cloud and pour points of biodiesel were 10°c and 1°c respectively. this result agrees with the previous report of kafuku and mbarawa (2010) which was 10°c and 3°c respectively. cloud and pour point of fuel indicates the fuel performance at low ambient temperature (agarwal and das, 2001). table vi showed the result of all main physicochemical properties of biodiesel synthesized. statistical analysis of experimental results analysis of variance (anova) for the quadratic model analysis of variance determines the significance of the experimental results using coded variables as indicated in table vii. the model f-value of 380.98 implies the model is significant. there is only a 0.01% chance that an f-value this large could occur due to noise. p-values less than 0.0500 indicate model terms are significant. in this case, a, b, c, a², b², c² are significant model terms. values greater than 0.1000 indicate the model terms are not significant. if there are many insignificant model terms (not counting those required to support hierarchy), model reduction may improve your model. the lack of fit f-value of 5.69 implies there is a 6.31% chance that a lack of fit f-value this large could occur due to noise. lack of fit is bad -we want the model to fit. this relatively low probability (<10%) is troubling. the coefficient estimate represents the expected change in response per unit change in factor value when all remaining factors are held constant. the intercept in an orthogonal design is the overall average response of all the runs. the coefficients are adjustments around that average based on the factor settings. when the factors are orthogonal the vifs are 1; vifs greater than 1 indicate multi-collinearity, and the higher the vif the more severe the correlation of factors. as a rough rule, vifs less than 10 are tolerable. the effect of process parameters on the yield of biodiesel effect of methanol to oil ratio figure. (2) shows the effect of methanol to oil ratio on biodiesel yield at constant temperature and catalyst loading. it showed that the yield of biodiesel increases as the methanol-to-oil ratio increases. increasing the methanol-to-oil ratio beyond the optimum value results in excess methanol which decreases the yield of biodiesel. the maximum yield of biodiesel (94%) was obtained at a methanol-to-oil ratio of 6: 1. therefore, this ratio was taken as an optimum value of the methanol-to-oil ratio. decreasing the methanol-to-oil ratio below the optimum value (3:1), decreased the conversion efficiency of the transesterification reaction and resulted in lower biodiesel yield. effect of reaction temperature figure (3) shows the effect of reaction temperature on the yield of biodiesel at a constant methanol-to-oil ratio and catalyst loading. the yield of biodiesel highly increased as temperature increased from 45°c to 55°c. maximum yield was obtained at 58°c and the yield started to decrease slightly from 58°c to 65°c due to the vaporization of methanol resulting in soap formation. the boiling point of methanol is 64.7°c. increasing reaction temperature above this point leads to methanol loss by evaporation and decreases the conversion efficiency of the reaction. at 45°c, the yield is about 75°c. effect of catalyst loading figure (4) shows the effect of catalyst loading on the yield of biodiesel at a constant methanol-to-oil ratio and temperature. as the amount of catalyst increased from 0.5% to 1.0%, the yield of biodiesel increased from 89% to 94% and the yield starts to decrease slightly as the amount of catalyst increased from 1.0% to 1.5% due to the formation of soap and emulsion. at a lower amount of catalyst (0.5%), the yield of biodiesel decreased due to the incomplete conversion of triglycerides of oil to fatty acid methyl ester. optimization of transesterification process parameters using the response surface method (rsm) the response surface method determined the optimum value of process variables that maximize the yield of the product and minimize production cost table viii showed that response surface method found 15 solutions and selected the optimum values to minimize the economic cost of temperature, methanol, and catalyst required for the reaction and to maximize the yield of biodiesel. the optimum yield of biodiesel (83.772%) was observed at a temperature of 51.537 and catalyst load of 0.500 wt.%. conclusions biodiesel is a promising biofuel that is synthesized by the transesterification of vegetable oils and animal fats. in this study, biodiesel was synthesized from moringa stenopetala seed oil using an alkali catalyst. the effect of methanol to oil ratio, reaction temperature, and catalyst weight on the yield and quality of biodiesel have been studied. biodiesel produced was characterized according to international fuel testing standards methods. the optimization of process parameters was carried out using response surface method (rsm). the experimental result showed that the highest yield of biodiesel was 94% and this result was obtained at an optimum value of temperature 55°c, methanol to oil ratio of 6:1, and catalyst load of 1.0%. increasing methanol to oil ratio, temperature, and catalyst load up to the optimum point increased the yield of biodiesel. however, further increase of the parameters above the optimum point decreased the yield of biodiesel. the temperature has the highest significant effect while the catalyst load has a lower effect. besides to characterization of different basic fuel properties of it, biodiesel can be blended with petrol-diesel at different percentages and applied in compression ignition engine to evaluate the effect of using a blend of biodiesel using different parameters such as engine power, brake thermal efficiency, specific fuel consumption, exhaust gas temperature, and greenhouse gas temperature and gas emission. however, the performance analysis of the blend of biodiesel with petrol diesel in a compression ignition engine was not done due to a lack of laboratory setup and equipment required to measure these parameters. this study did not compare biodiesel with diesel fuels used in diesel engines. moreover, it did not characterize the blend of biodiesel with petroleum fuels and did not compare biodiesel produced from other feedstocks other than moringa stenopetala. thus, further research should be done on these areas. generally, it can be concluded that moringa stenopetala is a promising alternative feedstock for biodiesel production for the reasons: it does not affect food security, has a good oil content, and can be harvested throughout the year. the biodiesel produced meets the standard fuel quality and international standard specifications. acknowledgment the authors are thankful to addis ababa institute of technology, addis ababa university, ethiopian environment and forest research institute, college of natural and computational science, addis ababa university, and ethiopian geological survey for their technical support. references agarwal ak and das lm (2001), biodiesel development and characterization for use as a fuel in compression in ignition engines, j eng gas turbines power. 123(2): 440-447. doi: 10.1115/1.1364522 atabani ae, silitonga as, ong hc, mahila tm, masjuki hh, irfan a and fayaz h (2013), non-edible vegetable oils: evaluation of oil extraction, fatty acid compositions, biodiesel production, characteristics, engine performance and emissions production, ren. sus. energy rev. 18: 211-245. doi: 10.1016/ j.rser.2012.10.013 atabani ae, mahlia tm, ifran a, masjuki hh, chong wt and keat tl (2013), investigation of physical and chemical properties of potential edible and non-edible feedstocks for biodiesel production, a comparative analysis, ren. sus. energy rev. 21: 749-55. doi: 10.1016/j.rser.2013.01.027 ayerza hr (2012), seed and oil yields of moringa oleifera variety periyakalum-1 introduced for oil production in four ecosystems of south america, ind. crops prod. 36: 70-73. doi: 10.1016/j.indcrop.2011.08.008 azad a, rasul m, khan k, subhash cs and rubayat i (2015), prospect of moringa seed oil is a sustainable biodiesel fuel in australia, procedia engineering. 105: 601-606, doi: 10.1016/j.proeng. 2015.05.037 choi c and reitz r (1999), a numerical analysis of emission characteristics of biodiesel blended fuels, j eng gas turbines power 121(1): 31-37. doi: 10.1115/1. 2816309 demirbas a (2005), potential applications of renewable energy sources, biomasscombustion problems in boiler power systems, and combustion-related environmentalissues, progress in energy and combustion sci. 31: 171-192. doi: 10.1016/j.pecs. 2005.02.002 demshemino si, donnel ps, muhamma fy, niwadike and okoro ln (2013), comparative analysis of biodiesel and petroleum diesel, international journal of education and research 1(8): 2-5. eman na and cadence it (2013), characterization of biodiesel produced from palm oilvia base-catalyzed transesterification, procedia engineering. 53: 7-12. doi: 10.1016/j.proeng.2013.02.002 gemeda t and desta n (2020), pre-extension demonstration of moringa preparation and utilization methods in east shoa zones of oromia, ethiopia, journal of biomaterials. 4(1): 17-22. doi: 10.11648/j.jb. 20200401.12 gemechu ys (2021), production and characterization of biodiesel from moringa stenopetala seed oil via catalytic transesterification process, thesis work at addis ababa university institute of technology, addis ababa, ethiopia. hamza ta and azmach nn (2017), the miraculous moringa trees: from a nutritionaland medicinal point of view in tropical regions, journal of medicinal plants studies 5 (4): 151-162. jayed mh, masjuki hh, kalam ma, mahlia tm, husnawan m and liaquat am (2011), prospects of dedicated biodiesel engine vehicles in malaysia and indonesia, ren. sus. ener. rev. 15: 220-235. doi: 10.1016/j.rser.2010.09.002 kafuku g and mbarawa m (2010), alkaline-catalyzed biodiesel production from moringa oleifera oil with optimized production parameters, applied energy. 87 (8): 2561-2565. doi:10.1016/j. apenergy. 2010.02.026 marchetti jm and yadessa gk (2012), a review of oil extraction from plant seeds for biodiesel production, ims energy. 5(4): 316-340. doi: 10.3934/energy. 2017.2.316 mahmudul h, hagos r, mamat a, abdul a and ishak ra (2017), production, characterization and performance of biodiesel as an alternative fuel in diesel engines, renewable and sustainable energy reviews 72(c): 497-509. doi: 10.1016/j.rser.2017.01.001 piyush n, subramanian ka and dastidar mg (2013), production and characterization of biodieselfrom algae, fuel processing technology. 120: 79-88. doi: 10.1016/j.fuproc.2013.12.003 raj s and bhandari m (2017), comparison of methods of production of biodiesel from jatropha curcas, journal of biofuel. 8(2): 58-80. rao pv (2011), experimental investigations on the influence of properties of jatropha biodiesel on performance, combustion, and emission characteristics of di–ci engines, world acad. sci. eng. technol. 5(3): 855-868. sreepada h and vijayalaxmi h (2013), an overview of moringa production in ethiopia, international journal of science and research 4(4): 2319-7064. doi: 10.36106/ijsr seema r and meena b (2017), comparison of methods of biodiesel productionfrom jatropha curcas, journal of biofuels. 8(2): 58-80. its advantages is it is considered a great natural cosmetic emollient and has high oxidative stability (ayerza, 2012). moringa plant is a high-value tree of the moringaceae family. it consists of 13 species highly distributed in africa and asia (hamza and azmach, 2017). moringa is particularly suitable for dry regions since it can be grown using rainwater without expensive irrigation techniques. moringa has been given less attention and ignored tree by communities to utilize it in different ways (gemeda and desta, 2020). flowering begins within the first six months. moringa stenopetala seed is an available and underutilized resource. ethiopia has a comfortable environment for mooring stenopetala plantations. many parts of the country particularly southern parts such as gamo goffa, sidama wolayitta, konso, and darashe have planted moringa in their garden and farmland (sreepada and vijayalaxmi, 2013). thus, this study investigated that moringa stenopetala seed oil is a potential industrial feedstock for biodiesel production as an alternative energy source. materials and methods the sample of moringa seed was collected from the gamo goffa zone, arba minch area of ethiopia. the seed sample was dried and milled to reduce the particle size. then, 80 g of sample was measured and put into the soxhlet apparatus thimble. then, it was placed in a 500 ml capacity soxhlet chamber. 400 ml solvent (hexane) was used for the extraction at different temperatures for 3 hrs. to 5 hrs. the extraction was conducted at 70°c, 75°c, and 80°c by varying extraction time to get the maximum possible oil yield. the soxhlet extraction method was selected since it results in high oil yield, is quick, the solvent can be reused, and is low cost (sreepada and vijayalaxmi, 2013). the unwanted substances were removed by evaporation and degumming. evaporation was used to separate hexane from table viii. optimum numerical solution by rsm number methanol to oil ratio temperature catalyst loading yield desirability 1 4.489 51.537 0.500 83.683 0.753 selected 2 4.511 51.501 0.500 83.722 0.753 3 4.513 51.518 0.500 83.753 0.753 4 4.487 51.430 0.500 83.529 0.753 5 4.500 51.630 0.500 83.850 0.753 6 4.444 51.617 0.500 83.610 0.753 7 4.521 51.382 0.500 83.599 0.753 8 4.450 51.419 0.500 83.369 0.753 9 4.419 51.558 0.500 83.428 0.753 10 4.512 51.729 0.500 84.028 0.753 11 4.422 51.412 0.500 83.243 0.753 12 4.472 51.818 0.500 83.981 0.753 13 4.421 51.813 0.500 83.769 0.753 14 4.773 50.864 0.500 83.781 0.751 15 5.068 53.527 0.500 87.898 0.737 fig. 2. effect of methanol to oil ratio on yield of biodiesel design-expert® software factor coding: actual yield (%) design points 95% ci bands x1 = a: methanol to oil ratio actual factors b: temperature = 55 c: catalyst loading = 1 a: methanol to oil ratio (-) 3 4 5 6 7 8 9 y ie ld ( % ) 65 72.25 79.5 86.75 94 3 22 22 one factor fig. 3. effect of temperature on yield of biodiesel design-expert® software factor coding: actual yield (%) design points 95% ci bands x1 = b: temperature actual factors a: methanol to oil ratio = 6 c: catalyst loading = 1 b: temperature 45 50 55 60 65 y ie ld ( % ) 65 72.25 79.5 86.75 94 3 22 22 one factor design-expert® software factor coding: actual yield (%) design points 95% ci bands x1 = c: catalyst loading actual factors a: methanol to oil ratio = 6 b: temperature = 55 c: catalyst loading (wt.%) 0.5 0.7 0.9 1.1 1.3 1.5 y ie ld ( % ) 65 72.25 79.5 86.75 94 3 22 22 one factor fig. 4. effect of catalyst loading on yield of biodiesel the most common production technology of biodiesel is the transesterification process. transesterification is a chemical reaction between one mole of triglyceride with three moles of alcohol to produce fatty acid methyl ester and glycerol in the presence of a catalyst or without a catalyst. most transesterification reactions use ethanol or methanol alcohol. many studies show that methanol is more practically used as alcohol than ethanol. methanol is preferable due to its low cost and its physical and chemical advantages. another advantage of using methanol is the ease of separation of glycerin which can be achieved by simple decantation (marchetti and yadessa, 2012). various catalysts can be used in the process. however, it was confirmed that the transesterification reaction was completed very fast when alkali catalysts are used. after the transesterification reaction is completed, glycerol, catalyst, alcohol, and soap are separated from biodiesel. the factors affecting biodiesel yield and fuel quality are alcohol-to-oil ratios, temperature, catalyst loading, and reaction time (raj and bhandari, 2017). biodiesel is formed when triglyceride reacts with alcohol leaving glycerol as a byproduct as shown in figure 1. there are more than 300 vegetable oils identified as potential feedstocks for biodiesel production globally. the availability, characteristics, and variety of feedstocks make them promising ingredients for the sustainable production of biodiesel (piyush et al. 2013). researchers have proposed moringa seed oil as an alternative potential feedstock to produce biodiesel. however, there is a research gap that promotes this feedstock for industrial processing. moringa seed has an average of 35%-45% oil content with high oleic content of greater than 73% based on the type of the tree. moringa oil has many various industrial and homemade benefits. one of oil by rotary evaporation at 80°c. gum and wax were removed by a degumming method. then, biodiesel was synthesized by transesterification reaction using a homogenous catalyst (methanol) at different process parameters. experimental design the experimental design used for this study was a box behnken design standard using design expert 11.0 software. the experimental design was done using three variables and tree levels for a response surface method. 17 experimental runswere selected by design expert 11.0 software using the box behnken design standard method, with five central points per block. the main factors that affect biodiesel production by transesterification reaction are reaction time, reaction temperature, and alcohol-to-oil ratio (seema and meena, 2017). as indicated in table i, the overall production of biodiesel was carried out at optimum parameters of catalyst load of 0.5 to 1.5 wt.%, reaction temperature of 45 to 65°c, and methanol to oil ratio of 3 to 9. the other parameters, reaction time and mixing intensity were kept constant at 1 hour and 500 rpm for all experimental runs. a combination of three factors and three levels of experimental runs was conducted. there are 17 experimental runs determined bybox behnken’s design arrangement as shown in table ii. production and purification of the product the method used to produce biodiesel was a one-steptransesterification reaction. methanol was the alcohol selected for the transesterification reaction due to its availability, low cost, popularity, and ease of separation (demirbas, 2005). the catalyst selected for this study was the base catalyst (koh) since biodiesel can be produced at low temperatures and pressure reactions. moreover, it is a homogeneous base catalyst that results in high conversion, minimum side reactions, short reaction time, and high yield (marchetti and yadessa, 2012). though it has many advantages, the disadvantage of the catalyst used is it cannot be reused. when the reaction is completed, biodiesel and glycerol were separated by a separatory funnel after it settles for 24 hours. then, biodiesel was washed with hot distilled water to remove soap, remaining methanol, and wax. optimization of the process parameters using the response surface method (rsm). optimization aims to determine the optimum value of the factors that affect the transesterification process to produce the maximum possible biodiesel yield at a minimum production cost. this is done by minimizing the methanol to oil ratio, reaction temperature, and amount of catalyst used as indicated in table iii. characterization of biodiesel characterization of fuel is determining the physical and chemical properties (atabani et al. 2013). the physical and chemical properties of biodiesel were determined according to the american society for testing materials (astm d 6751) and european standard (en 14214) methods (demirbas, 2005). table iv showed the physical and chemical properties of biodiesel and the standard methods used to determine them. statistical analysis of experimental results data analysis of the experiment was done by design expert 11.0 software using box behnken design standard. the significance of experimental variables was obtained from analysis of variance (anova). results and discussions yield the maximum oil yield obtained at optimum conditions of temperature 80°c and extraction time 5 hours was 39.86 %. this result agreed with the average oil content of moringa stenopetala seed oil which is 35% 45% (ayerza, 2012), and this result also agreed with the previous reportof 38% which was reported by azad et al. (2015) and by gemechu (2021). the maximum yield of biodiesel was 94% and it was obtained at optimum process parameters of methanol to oil ratio 6:1, temperature 55°c, and catalyst loading 1.0%. the yield of biodiesel obtained agrees with the previous report of azad et al. (2015) which was 91%. the yield increased as transesterification parameters increased until the optimum value and decreased beyond the optimum value. at the lower value of parameters, the yield decreased due to the incomplete conversion of reactants to the product. table v showed the yield response of all experimental runs. characterization of biodiesel physical and chemical properties of biodiesel were evaluated using standard methods and the results were compared with astm and en standard methods and previous reports. density the value of the density of biodiesel was 874 kg/m3. this result is within the standard range of density (860 – 900 kg/m3) (demirbas, 2005) and agrees with the previous report by kafuku and mbarawa (2010) which was 900 kg/m3. higher density increases thesize of fuel droplets and causes higher emission of particulate matter and nox emission ina diesel engine while the lower density of fuel expands the efficiency of atomization (choi and reitz, 1999). kinematic viscosity the experimental result showed that the value of kinematic viscosity was 4.8 mm2/s. this result is within the range of the astm standard value of biodiesel which is 1.6-6 (eman and cadence, 2013; demirbas, 2005). highly viscous fuel is difficult to pump and operate in internal combustion engines while lower kinematic viscosity of fuels increases wear leakage due to insufficient lubrication (rao, 2011). acid value the value of an acid value obtained was 0.4 mm koh/g. this result agrees with the previous report (kafuku and mbarawa, 2010), with a value of 1.2 mmkoh/g. higher acid-value fuels need further acid treatment costs and it also lowers the quality of the fuels. in this study, the lower acid value of biodiesel indicates that it has higher fuel quality. calorific value the experimental result showed that the value of biodiesel was 10287 cal/ g or 43 mj/kj. this result agrees with the previous report of mahamudul et al. (2017) which was 39 mj/kg, and the previous report of agarwal and das (2001) which was 43.2 kj/kg. the result obtained is above the standard astm value which is 42-42.5 mj/kg. this result indicates the higher fuel quality of biodiesel. the calorific value obtained is similar to that of conventional diesel fuels. this is the novel result of this study. flash point the flash point obtained from the experimental result was 184°c. this result agrees with the standard astm value of biodiesel flash point which is greater than 130°c. from this study, the higher flash point of biodiesel indicates that it is safer to handle, store and transport the fuel (jayed et al. 2011). cetane number the value of the cetane number observed was 53. this result agrees with the standard astm value of the cetane number of biodiesel which is greater than 47 (demirbas, 2005). fuels with higher cetane number benefit the engine performance since the engine starts rapidly and run smoothly without causing much noise. cloud and pour point the experimental result showed that the cloud and pour points of biodiesel were 10°c and 1°c respectively. this result agrees with the previous report of kafuku and mbarawa (2010) which was 10°c and 3°c respectively. cloud and pour point of fuel indicates the fuel performance at low ambient temperature (agarwal and das, 2001). table vi showed the result of all main physicochemical properties of biodiesel synthesized. statistical analysis of experimental results analysis of variance (anova) for the quadratic model analysis of variance determines the significance of the experimental results using coded variables as indicated in table vii. the model f-value of 380.98 implies the model is significant. there is only a 0.01% chance that an f-value this large could occur due to noise. p-values less than 0.0500 indicate model terms are significant. in this case, a, b, c, a², b², c² are significant model terms. values greater than 0.1000 indicate the model terms are not significant. if there are many insignificant model terms (not counting those required to support hierarchy), model reduction may improve your model. the lack of fit f-value of 5.69 implies there is a 6.31% chance that a lack of fit f-value this large could occur due to noise. lack of fit is bad -we want the model to fit. this relatively low probability (<10%) is troubling. the coefficient estimate represents the expected change in response per unit change in factor value when all remaining factors are held constant. the intercept in an orthogonal design is the overall average response of all the runs. the coefficients are adjustments around that average based on the factor settings. when the factors are orthogonal the vifs are 1; vifs greater than 1 indicate multi-collinearity, and the higher the vif the more severe the correlation of factors. as a rough rule, vifs less than 10 are tolerable. the effect of process parameters on the yield of biodiesel effect of methanol to oil ratio figure. (2) shows the effect of methanol to oil ratio on biodiesel yield at constant temperature and catalyst loading. it showed that the yield of biodiesel increases as the methanol-to-oil ratio increases. increasing the methanol-to-oil ratio beyond the optimum value results in excess methanol which decreases the yield of biodiesel. the maximum yield of biodiesel (94%) was obtained at a methanol-to-oil ratio of 6: 1. therefore, this ratio was taken as an optimum value of the methanol-to-oil ratio. decreasing the methanol-to-oil ratio below the optimum value (3:1), decreased the conversion efficiency of the transesterification reaction and resulted in lower biodiesel yield. effect of reaction temperature figure (3) shows the effect of reaction temperature on the yield of biodiesel at a constant methanol-to-oil ratio and catalyst loading. the yield of biodiesel highly increased as temperature increased from 45°c to 55°c. maximum yield was obtained at 58°c and the yield started to decrease slightly from 58°c to 65°c due to the vaporization of methanol resulting in soap formation. the boiling point of methanol is 64.7°c. increasing reaction temperature above this point leads to methanol loss by evaporation and decreases the conversion efficiency of the reaction. at 45°c, the yield is about 75°c. effect of catalyst loading figure (4) shows the effect of catalyst loading on the yield of biodiesel at a constant methanol-to-oil ratio and temperature. as the amount of catalyst increased from 0.5% to 1.0%, the yield of biodiesel increased from 89% to 94% and the yield starts to decrease slightly as the amount of catalyst increased from 1.0% to 1.5% due to the formation of soap and emulsion. at a lower amount of catalyst (0.5%), the yield of biodiesel decreased due to the incomplete conversion of triglycerides of oil to fatty acid methyl ester. optimization of transesterification process parameters using the response surface method (rsm) the response surface method determined the optimum value of process variables that maximize the yield of the product and minimize production cost table viii showed that response surface method found 15 solutions and selected the optimum values to minimize the economic cost of temperature, methanol, and catalyst required for the reaction and to maximize the yield of biodiesel. the optimum yield of biodiesel (83.772%) was observed at a temperature of 51.537 and catalyst load of 0.500 wt.%. conclusions biodiesel is a promising biofuel that is synthesized by the transesterification of vegetable oils and animal fats. in this study, biodiesel was synthesized from moringa stenopetala seed oil using an alkali catalyst. the effect of methanol to oil ratio, reaction temperature, and catalyst weight on the yield and quality of biodiesel have been studied. biodiesel produced was characterized according to international fuel testing standards methods. the optimization of process parameters was carried out using response surface method (rsm). the experimental result showed that the highest yield of biodiesel was 94% and this result was obtained at an optimum value of temperature 55°c, methanol to oil ratio of 6:1, and catalyst load of 1.0%. increasing methanol to oil ratio, temperature, and catalyst load up to the optimum point increased the yield of biodiesel. however, further increase of the parameters above the optimum point decreased the yield of biodiesel. the temperature has the highest significant effect while the catalyst load has a lower effect. besides to characterization of different basic fuel properties of it, biodiesel can be blended with petrol-diesel at different percentages and applied in compression ignition engine to evaluate the effect of using a blend of biodiesel using different parameters such as engine power, brake thermal efficiency, specific fuel consumption, exhaust gas temperature, and greenhouse gas temperature and gas emission. however, the performance analysis of the blend of biodiesel with petrol diesel in a compression ignition engine was not done due to a lack of laboratory setup and equipment required to measure these parameters. this study did not compare biodiesel with diesel fuels used in diesel engines. moreover, it did not characterize the blend of biodiesel with petroleum fuels and did not compare biodiesel produced from other feedstocks other than moringa stenopetala. thus, further research should be done on these areas. generally, it can be concluded that moringa stenopetala is a promising alternative feedstock for biodiesel production for the reasons: it does not affect food security, has a good oil content, and can be harvested throughout the year. the biodiesel produced meets the standard fuel quality and international standard specifications. acknowledgment the authors are thankful to addis ababa institute of technology, addis ababa university, ethiopian environment and forest research institute, college of natural and computational science, addis ababa university, and ethiopian geological survey for their technical support. references agarwal ak and das lm (2001), biodiesel development and characterization for use as a fuel in compression in ignition engines, j eng gas turbines power. 123(2): 440-447. doi: 10.1115/1.1364522 atabani ae, silitonga as, ong hc, mahila tm, masjuki hh, irfan a and fayaz h (2013), non-edible vegetable oils: evaluation of oil extraction, fatty acid compositions, biodiesel production, characteristics, engine performance and emissions production, ren. sus. energy rev. 18: 211-245. doi: 10.1016/ j.rser.2012.10.013 atabani ae, mahlia tm, ifran a, masjuki hh, chong wt and keat tl (2013), investigation of physical and chemical properties of potential edible and non-edible feedstocks for biodiesel production, a comparative analysis, ren. sus. energy rev. 21: 749-55. doi: 10.1016/j.rser.2013.01.027 ayerza hr (2012), seed and oil yields of moringa oleifera variety periyakalum-1 introduced for oil production in four ecosystems of south america, ind. crops prod. 36: 70-73. doi: 10.1016/j.indcrop.2011.08.008 azad a, rasul m, khan k, subhash cs and rubayat i (2015), prospect of moringa seed oil is a sustainable biodiesel fuel in australia, procedia engineering. 105: 601-606, doi: 10.1016/j.proeng. 2015.05.037 choi c and reitz r (1999), a numerical analysis of emission characteristics of biodiesel blended fuels, j eng gas turbines power 121(1): 31-37. doi: 10.1115/1. 2816309 demirbas a (2005), potential applications of renewable energy sources, biomasscombustion problems in boiler power systems, and combustion-related environmentalissues, progress in energy and combustion sci. 31: 171-192. doi: 10.1016/j.pecs. 2005.02.002 demshemino si, donnel ps, muhamma fy, niwadike and okoro ln (2013), comparative analysis of biodiesel and petroleum diesel, international journal of education and research 1(8): 2-5. eman na and cadence it (2013), characterization of biodiesel produced from palm oilvia base-catalyzed transesterification, procedia engineering. 53: 7-12. doi: 10.1016/j.proeng.2013.02.002 gemeda t and desta n (2020), pre-extension demonstration of moringa preparation and utilization methods in east shoa zones of oromia, ethiopia, journal of biomaterials. 4(1): 17-22. doi: 10.11648/j.jb. 20200401.12 gemechu ys (2021), production and characterization of biodiesel from moringa stenopetala seed oil via catalytic transesterification process, thesis work at addis ababa university institute of technology, addis ababa, ethiopia. hamza ta and azmach nn (2017), the miraculous moringa trees: from a nutritionaland medicinal point of view in tropical regions, journal of medicinal plants studies 5 (4): 151-162. jayed mh, masjuki hh, kalam ma, mahlia tm, husnawan m and liaquat am (2011), prospects of dedicated biodiesel engine vehicles in malaysia and indonesia, ren. sus. ener. rev. 15: 220-235. doi: 10.1016/j.rser.2010.09.002 kafuku g and mbarawa m (2010), alkaline-catalyzed biodiesel production from moringa oleifera oil with optimized production parameters, applied energy. 87 (8): 2561-2565. doi:10.1016/j. apenergy. 2010.02.026 marchetti jm and yadessa gk (2012), a review of oil extraction from plant seeds for biodiesel production, ims energy. 5(4): 316-340. doi: 10.3934/energy. 2017.2.316 mahmudul h, hagos r, mamat a, abdul a and ishak ra (2017), production, characterization and performance of biodiesel as an alternative fuel in diesel engines, renewable and sustainable energy reviews 72(c): 497-509. doi: 10.1016/j.rser.2017.01.001 piyush n, subramanian ka and dastidar mg (2013), production and characterization of biodieselfrom algae, fuel processing technology. 120: 79-88. doi: 10.1016/j.fuproc.2013.12.003 raj s and bhandari m (2017), comparison of methods of production of biodiesel from jatropha curcas, journal of biofuel. 8(2): 58-80. rao pv (2011), experimental investigations on the influence of properties of jatropha biodiesel on performance, combustion, and emission characteristics of di–ci engines, world acad. sci. eng. technol. 5(3): 855-868. sreepada h and vijayalaxmi h (2013), an overview of moringa production in ethiopia, international journal of science and research 4(4): 2319-7064. doi: 10.36106/ijsr seema r and meena b (2017), comparison of methods of biodiesel productionfrom jatropha curcas, journal of biofuels. 8(2): 58-80. shage and ali 43 its advantages is it is considered a great natural cosmetic emollient and has high oxidative stability (ayerza, 2012). moringa plant is a high-value tree of the moringaceae family. it consists of 13 species highly distributed in africa and asia (hamza and azmach, 2017). moringa is particularly suitable for dry regions since it can be grown using rainwater without expensive irrigation techniques. moringa has been given less attention and ignored tree by communities to utilize it in different ways (gemeda and desta, 2020). flowering begins within the first six months. moringa stenopetala seed is an available and underutilized resource. ethiopia has a comfortable environment for mooring stenopetala plantations. many parts of the country particularly southern parts such as gamo goffa, sidama wolayitta, konso, and darashe have planted moringa in their garden and farmland (sreepada and vijayalaxmi, 2013). thus, this study investigated that moringa stenopetala seed oil is a potential industrial feedstock for biodiesel production as an alternative energy source. materials and methods the sample of moringa seed was collected from the gamo goffa zone, arba minch area of ethiopia. the seed sample was dried and milled to reduce the particle size. then, 80 g of sample was measured and put into the soxhlet apparatus thimble. then, it was placed in a 500 ml capacity soxhlet chamber. 400 ml solvent (hexane) was used for the extraction at different temperatures for 3 hrs. to 5 hrs. the extraction was conducted at 70°c, 75°c, and 80°c by varying extraction time to get the maximum possible oil yield. the soxhlet extraction method was selected since it results in high oil yield, is quick, the solvent can be reused, and is low cost (sreepada and vijayalaxmi, 2013). the unwanted substances were removed by evaporation and degumming. evaporation was used to separate hexane from the most common production technology of biodiesel is the transesterification process. transesterification is a chemical reaction between one mole of triglyceride with three moles of alcohol to produce fatty acid methyl ester and glycerol in the presence of a catalyst or without a catalyst. most transesterification reactions use ethanol or methanol alcohol. many studies show that methanol is more practically used as alcohol than ethanol. methanol is preferable due to its low cost and its physical and chemical advantages. another advantage of using methanol is the ease of separation of glycerin which can be achieved by simple decantation (marchetti and yadessa, 2012). various catalysts can be used in the process. however, it was confirmed that the transesterification reaction was completed very fast when alkali catalysts are used. after the transesterification reaction is completed, glycerol, catalyst, alcohol, and soap are separated from biodiesel. the factors affecting biodiesel yield and fuel quality are alcohol-to-oil ratios, temperature, catalyst loading, and reaction time (raj and bhandari, 2017). biodiesel is formed when triglyceride reacts with alcohol leaving glycerol as a byproduct as shown in figure 1. there are more than 300 vegetable oils identified as potential feedstocks for biodiesel production globally. the availability, characteristics, and variety of feedstocks make them promising ingredients for the sustainable production of biodiesel (piyush et al. 2013). researchers have proposed moringa seed oil as an alternative potential feedstock to produce biodiesel. however, there is a research gap that promotes this feedstock for industrial processing. moringa seed has an average of 35%-45% oil content with high oleic content of greater than 73% based on the type of the tree. moringa oil has many various industrial and homemade benefits. one of oil by rotary evaporation at 80°c. gum and wax were removed by a degumming method. then, biodiesel was synthesized by transesterification reaction using a homogenous catalyst (methanol) at different process parameters. experimental design the experimental design used for this study was a box behnken design standard using design expert 11.0 software. the experimental design was done using three variables and tree levels for a response surface method. 17 experimental runswere selected by design expert 11.0 software using the box behnken design standard method, with five central points per block. the main factors that affect biodiesel production by transesterification reaction are reaction time, reaction temperature, and alcohol-to-oil ratio (seema and meena, 2017). as indicated in table i, the overall production of biodiesel was carried out at optimum parameters of catalyst load of 0.5 to 1.5 wt.%, reaction temperature of 45 to 65°c, and methanol to oil ratio of 3 to 9. the other parameters, reaction time and mixing intensity were kept constant at 1 hour and 500 rpm for all experimental runs. a combination of three factors and three levels of experimental runs was conducted. there are 17 experimental runs determined bybox behnken’s design arrangement as shown in table ii. production and purification of the product the method used to produce biodiesel was a one-steptransesterification reaction. methanol was the alcohol selected for the transesterification reaction due to its availability, low cost, popularity, and ease of separation (demirbas, 2005). the catalyst selected for this study was the base catalyst (koh) since biodiesel can be produced at low temperatures and pressure reactions. moreover, it is a homogeneous base catalyst that results in high conversion, minimum side reactions, short reaction time, and high yield (marchetti and yadessa, 2012). though it has many advantages, the disadvantage of the catalyst used is it cannot be reused. when the reaction is completed, biodiesel and glycerol were separated by a separatory funnel after it settles for 24 hours. then, biodiesel was washed with hot distilled water to remove soap, remaining methanol, and wax. optimization of the process parameters using the response surface method (rsm). optimization aims to determine the optimum value of the factors that affect the transesterification process to produce the maximum possible biodiesel yield at a minimum production cost. this is done by minimizing the methanol to oil ratio, reaction temperature, and amount of catalyst used as indicated in table iii. characterization of biodiesel characterization of fuel is determining the physical and chemical properties (atabani et al. 2013). the physical and chemical properties of biodiesel were determined according to the american society for testing materials (astm d 6751) and european standard (en 14214) methods (demirbas, 2005). table iv showed the physical and chemical properties of biodiesel and the standard methods used to determine them. statistical analysis of experimental results data analysis of the experiment was done by design expert 11.0 software using box behnken design standard. the significance of experimental variables was obtained from analysis of variance (anova). results and discussions yield the maximum oil yield obtained at optimum conditions of temperature 80°c and extraction time 5 hours was 39.86 %. this result agreed with the average oil content of moringa stenopetala seed oil which is 35% 45% (ayerza, 2012), and this result also agreed with the previous reportof 38% which was reported by azad et al. (2015) and by gemechu (2021). the maximum yield of biodiesel was 94% and it was obtained at optimum process parameters of methanol to oil ratio 6:1, temperature 55°c, and catalyst loading 1.0%. the yield of biodiesel obtained agrees with the previous report of azad et al. (2015) which was 91%. the yield increased as transesterification parameters increased until the optimum value and decreased beyond the optimum value. at the lower value of parameters, the yield decreased due to the incomplete conversion of reactants to the product. table v showed the yield response of all experimental runs. characterization of biodiesel physical and chemical properties of biodiesel were evaluated using standard methods and the results were compared with astm and en standard methods and previous reports. density the value of the density of biodiesel was 874 kg/m3. this result is within the standard range of density (860 – 900 kg/m3) (demirbas, 2005) and agrees with the previous report by kafuku and mbarawa (2010) which was 900 kg/m3. higher density increases thesize of fuel droplets and causes higher emission of particulate matter and nox emission ina diesel engine while the lower density of fuel expands the efficiency of atomization (choi and reitz, 1999). kinematic viscosity the experimental result showed that the value of kinematic viscosity was 4.8 mm2/s. this result is within the range of the astm standard value of biodiesel which is 1.6-6 (eman and cadence, 2013; demirbas, 2005). highly viscous fuel is difficult to pump and operate in internal combustion engines while lower kinematic viscosity of fuels increases wear leakage due to insufficient lubrication (rao, 2011). acid value the value of an acid value obtained was 0.4 mm koh/g. this result agrees with the previous report (kafuku and mbarawa, 2010), with a value of 1.2 mmkoh/g. higher acid-value fuels need further acid treatment costs and it also lowers the quality of the fuels. in this study, the lower acid value of biodiesel indicates that it has higher fuel quality. calorific value the experimental result showed that the value of biodiesel was 10287 cal/ g or 43 mj/kj. this result agrees with the previous report of mahamudul et al. (2017) which was 39 mj/kg, and the previous report of agarwal and das (2001) which was 43.2 kj/kg. the result obtained is above the standard astm value which is 42-42.5 mj/kg. this result indicates the higher fuel quality of biodiesel. the calorific value obtained is similar to that of conventional diesel fuels. this is the novel result of this study. flash point the flash point obtained from the experimental result was 184°c. this result agrees with the standard astm value of biodiesel flash point which is greater than 130°c. from this study, the higher flash point of biodiesel indicates that it is safer to handle, store and transport the fuel (jayed et al. 2011). cetane number the value of the cetane number observed was 53. this result agrees with the standard astm value of the cetane number of biodiesel which is greater than 47 (demirbas, 2005). fuels with higher cetane number benefit the engine performance since the engine starts rapidly and run smoothly without causing much noise. cloud and pour point the experimental result showed that the cloud and pour points of biodiesel were 10°c and 1°c respectively. this result agrees with the previous report of kafuku and mbarawa (2010) which was 10°c and 3°c respectively. cloud and pour point of fuel indicates the fuel performance at low ambient temperature (agarwal and das, 2001). table vi showed the result of all main physicochemical properties of biodiesel synthesized. statistical analysis of experimental results analysis of variance (anova) for the quadratic model analysis of variance determines the significance of the experimental results using coded variables as indicated in table vii. the model f-value of 380.98 implies the model is significant. there is only a 0.01% chance that an f-value this large could occur due to noise. p-values less than 0.0500 indicate model terms are significant. in this case, a, b, c, a², b², c² are significant model terms. values greater than 0.1000 indicate the model terms are not significant. if there are many insignificant model terms (not counting those required to support hierarchy), model reduction may improve your model. the lack of fit f-value of 5.69 implies there is a 6.31% chance that a lack of fit f-value this large could occur due to noise. lack of fit is bad -we want the model to fit. this relatively low probability (<10%) is troubling. the coefficient estimate represents the expected change in response per unit change in factor value when all remaining factors are held constant. the intercept in an orthogonal design is the overall average response of all the runs. the coefficients are adjustments around that average based on the factor settings. when the factors are orthogonal the vifs are 1; vifs greater than 1 indicate multi-collinearity, and the higher the vif the more severe the correlation of factors. as a rough rule, vifs less than 10 are tolerable. the effect of process parameters on the yield of biodiesel effect of methanol to oil ratio figure. (2) shows the effect of methanol to oil ratio on biodiesel yield at constant temperature and catalyst loading. it showed that the yield of biodiesel increases as the methanol-to-oil ratio increases. increasing the methanol-to-oil ratio beyond the optimum value results in excess methanol which decreases the yield of biodiesel. the maximum yield of biodiesel (94%) was obtained at a methanol-to-oil ratio of 6: 1. therefore, this ratio was taken as an optimum value of the methanol-to-oil ratio. decreasing the methanol-to-oil ratio below the optimum value (3:1), decreased the conversion efficiency of the transesterification reaction and resulted in lower biodiesel yield. effect of reaction temperature figure (3) shows the effect of reaction temperature on the yield of biodiesel at a constant methanol-to-oil ratio and catalyst loading. the yield of biodiesel highly increased as temperature increased from 45°c to 55°c. maximum yield was obtained at 58°c and the yield started to decrease slightly from 58°c to 65°c due to the vaporization of methanol resulting in soap formation. the boiling point of methanol is 64.7°c. increasing reaction temperature above this point leads to methanol loss by evaporation and decreases the conversion efficiency of the reaction. at 45°c, the yield is about 75°c. effect of catalyst loading figure (4) shows the effect of catalyst loading on the yield of biodiesel at a constant methanol-to-oil ratio and temperature. as the amount of catalyst increased from 0.5% to 1.0%, the yield of biodiesel increased from 89% to 94% and the yield starts to decrease slightly as the amount of catalyst increased from 1.0% to 1.5% due to the formation of soap and emulsion. at a lower amount of catalyst (0.5%), the yield of biodiesel decreased due to the incomplete conversion of triglycerides of oil to fatty acid methyl ester. optimization of transesterification process parameters using the response surface method (rsm) the response surface method determined the optimum value of process variables that maximize the yield of the product and minimize production cost table viii showed that response surface method found 15 solutions and selected the optimum values to minimize the economic cost of temperature, methanol, and catalyst required for the reaction and to maximize the yield of biodiesel. the optimum yield of biodiesel (83.772%) was observed at a temperature of 51.537 and catalyst load of 0.500 wt.%. conclusions biodiesel is a promising biofuel that is synthesized by the transesterification of vegetable oils and animal fats. in this study, biodiesel was synthesized from moringa stenopetala seed oil using an alkali catalyst. the effect of methanol to oil ratio, reaction temperature, and catalyst weight on the yield and quality of biodiesel have been studied. biodiesel produced was characterized according to international fuel testing standards methods. the optimization of process parameters was carried out using response surface method (rsm). the experimental result showed that the highest yield of biodiesel was 94% and this result was obtained at an optimum value of temperature 55°c, methanol to oil ratio of 6:1, and catalyst load of 1.0%. increasing methanol to oil ratio, temperature, and catalyst load up to the optimum point increased the yield of biodiesel. however, further increase of the parameters above the optimum point decreased the yield of biodiesel. the temperature has the highest significant effect while the catalyst load has a lower effect. besides to characterization of different basic fuel properties of it, biodiesel can be blended with petrol-diesel at different percentages and applied in compression ignition engine to evaluate the effect of using a blend of biodiesel using different parameters such as engine power, brake thermal efficiency, specific fuel consumption, exhaust gas temperature, and greenhouse gas temperature and gas emission. however, the performance analysis of the blend of biodiesel with petrol diesel in a compression ignition engine was not done due to a lack of laboratory setup and equipment required to measure these parameters. this study did not compare biodiesel with diesel fuels used in diesel engines. moreover, it did not characterize the blend of biodiesel with petroleum fuels and did not compare biodiesel produced from other feedstocks other than moringa stenopetala. thus, further research should be done on these areas. generally, it can be concluded that moringa stenopetala is a promising alternative feedstock for biodiesel production for the reasons: it does not affect food security, has a good oil content, and can be harvested throughout the year. the biodiesel produced meets the standard fuel quality and international standard specifications. acknowledgment the authors are thankful to addis ababa institute of technology, addis ababa university, ethiopian environment and forest research institute, college of natural and computational science, addis ababa university, and ethiopian geological survey for their technical support. references agarwal ak and das lm (2001), biodiesel development and characterization for use as a fuel in compression in ignition engines, j eng gas turbines power. 123(2): 440-447. doi: 10.1115/1.1364522 atabani ae, silitonga as, ong hc, mahila tm, masjuki hh, irfan a and fayaz h (2013), non-edible vegetable oils: evaluation of oil extraction, fatty acid compositions, biodiesel production, characteristics, engine performance and emissions production, ren. sus. energy rev. 18: 211-245. doi: 10.1016/ j.rser.2012.10.013 atabani ae, mahlia tm, ifran a, masjuki hh, chong wt and keat tl (2013), investigation of physical and chemical properties of potential edible and non-edible feedstocks for biodiesel production, a comparative analysis, ren. sus. energy rev. 21: 749-55. doi: 10.1016/j.rser.2013.01.027 ayerza hr (2012), seed and oil yields of moringa oleifera variety periyakalum-1 introduced for oil production in four ecosystems of south america, ind. crops prod. 36: 70-73. doi: 10.1016/j.indcrop.2011.08.008 azad a, rasul m, khan k, subhash cs and rubayat i (2015), prospect of moringa seed oil is a sustainable biodiesel fuel in australia, procedia engineering. 105: 601-606, doi: 10.1016/j.proeng. 2015.05.037 choi c and reitz r (1999), a numerical analysis of emission characteristics of biodiesel blended fuels, j eng gas turbines power 121(1): 31-37. doi: 10.1115/1. 2816309 demirbas a (2005), potential applications of renewable energy sources, biomasscombustion problems in boiler power systems, and combustion-related environmentalissues, progress in energy and combustion sci. 31: 171-192. doi: 10.1016/j.pecs. 2005.02.002 demshemino si, donnel ps, muhamma fy, niwadike and okoro ln (2013), comparative analysis of biodiesel and petroleum diesel, international journal of education and research 1(8): 2-5. eman na and cadence it (2013), characterization of biodiesel produced from palm oilvia base-catalyzed transesterification, procedia engineering. 53: 7-12. doi: 10.1016/j.proeng.2013.02.002 gemeda t and desta n (2020), pre-extension demonstration of moringa preparation and utilization methods in east shoa zones of oromia, ethiopia, journal of biomaterials. 4(1): 17-22. doi: 10.11648/j.jb. 20200401.12 gemechu ys (2021), production and characterization of biodiesel from moringa stenopetala seed oil via catalytic transesterification process, thesis work at addis ababa university institute of technology, addis ababa, ethiopia. hamza ta and azmach nn (2017), the miraculous moringa trees: from a nutritionaland medicinal point of view in tropical regions, journal of medicinal plants studies 5 (4): 151-162. jayed mh, masjuki hh, kalam ma, mahlia tm, husnawan m and liaquat am (2011), prospects of dedicated biodiesel engine vehicles in malaysia and indonesia, ren. sus. ener. rev. 15: 220-235. doi: 10.1016/j.rser.2010.09.002 kafuku g and mbarawa m (2010), alkaline-catalyzed biodiesel production from moringa oleifera oil with optimized production parameters, applied energy. 87 (8): 2561-2565. doi:10.1016/j. apenergy. 2010.02.026 marchetti jm and yadessa gk (2012), a review of oil extraction from plant seeds for biodiesel production, ims energy. 5(4): 316-340. doi: 10.3934/energy. 2017.2.316 mahmudul h, hagos r, mamat a, abdul a and ishak ra (2017), production, characterization and performance of biodiesel as an alternative fuel in diesel engines, renewable and sustainable energy reviews 72(c): 497-509. doi: 10.1016/j.rser.2017.01.001 piyush n, subramanian ka and dastidar mg (2013), production and characterization of biodieselfrom algae, fuel processing technology. 120: 79-88. doi: 10.1016/j.fuproc.2013.12.003 raj s and bhandari m (2017), comparison of methods of production of biodiesel from jatropha curcas, journal of biofuel. 8(2): 58-80. rao pv (2011), experimental investigations on the influence of properties of jatropha biodiesel on performance, combustion, and emission characteristics of di–ci engines, world acad. sci. eng. technol. 5(3): 855-868. sreepada h and vijayalaxmi h (2013), an overview of moringa production in ethiopia, international journal of science and research 4(4): 2319-7064. doi: 10.36106/ijsr seema r and meena b (2017), comparison of methods of biodiesel productionfrom jatropha curcas, journal of biofuels. 8(2): 58-80. biodiesel from moringa stenopetala seed oil 58(1) 202344 its advantages is it is considered a great natural cosmetic emollient and has high oxidative stability (ayerza, 2012). moringa plant is a high-value tree of the moringaceae family. it consists of 13 species highly distributed in africa and asia (hamza and azmach, 2017). moringa is particularly suitable for dry regions since it can be grown using rainwater without expensive irrigation techniques. moringa has been given less attention and ignored tree by communities to utilize it in different ways (gemeda and desta, 2020). flowering begins within the first six months. moringa stenopetala seed is an available and underutilized resource. ethiopia has a comfortable environment for mooring stenopetala plantations. many parts of the country particularly southern parts such as gamo goffa, sidama wolayitta, konso, and darashe have planted moringa in their garden and farmland (sreepada and vijayalaxmi, 2013). thus, this study investigated that moringa stenopetala seed oil is a potential industrial feedstock for biodiesel production as an alternative energy source. materials and methods the sample of moringa seed was collected from the gamo goffa zone, arba minch area of ethiopia. the seed sample was dried and milled to reduce the particle size. then, 80 g of sample was measured and put into the soxhlet apparatus thimble. then, it was placed in a 500 ml capacity soxhlet chamber. 400 ml solvent (hexane) was used for the extraction at different temperatures for 3 hrs. to 5 hrs. the extraction was conducted at 70°c, 75°c, and 80°c by varying extraction time to get the maximum possible oil yield. the soxhlet extraction method was selected since it results in high oil yield, is quick, the solvent can be reused, and is low cost (sreepada and vijayalaxmi, 2013). the unwanted substances were removed by evaporation and degumming. evaporation was used to separate hexane from 89 optimization of alkali concentration in the pretreatment of sugarcane bagasse for ethanol production s. m. asaduzzaman sujan1,3*, m. hossain2, m. nashir uddin4 and a. n. m. fakhruddin1 1department of environmental science, jahangirnagar university, savar, dhaka-1342, bangladesh 2institute of fuel research and development, bangladesh council of scientific and industrial research, savar, dhaka-1350, bangladesh 3leather research institute, bangladesh council of scientific and industrial research, dhaka-1205, bangladesh 4pulp and paper research division, bangladesh council of scientific and industrial research, dhaka-1205, bangladesh abstract this study was aimed for the investigation of the effect of pretreatment procedure of alkaline, based on the chemical arrangement, surface morphology, structural composition and enzymatic assimilation of sugarcane bagasse for sugars and ethanol production. alkali pretreatment (0 to 8% w/v of naoh) assists to reduce the lignin portion (from 19.57±0.03% to 9.91±0.02%) and increase the cellulose content of the treated sb (from 34.66±0.05% to 63.58±0.05%) simultaneously. the optimal conditions for alkali pretreatment were 8% naoh charge at 100oc for 90 min. enzymatic digestibility of alkali treated sb was significantly improved and hydrolysis yield reached to 89.59% glucose and 61.23% xylose at an prime level using trichoderma viridae. further hydrolysate of 8% (w/v) alkali treated sb sample was fermented by saccharomyces cerevisiae to convert sugar into ethanol and yield was 16.81±0.32% in 24 h. alkali pretreatment was found to be a treatment of choice for cellulose hydrolysis in sb and subsequent sugar acquired for the production of ethanol during fermentation. keywords: sugarcane bagasse; alkali treatment; time; temperature; bioethanol; xrd; sem *corresponding author’s e-mail: asad2306@gmail.com available online at www.banglajol.info bangladesh j. sci. ind. res. 58(2), 89-98, 2023 introduction due to a possible source of renewable energy and a reduction in green house gases (ghg) emissions, recently emphasize on exclusive products using lignocellulosic materials has increased. (den et al. 2018; janker-obermeier et al. 2012). in comparison to first generation biofuel, second generation biofuel made from lignocellulosic sources has more energetic, economic, and environmental benefits (hirani et al. 2018). mostly three biological polymerscellulose, lignin and hemicellulose comprise the lignocellulosic biomass in which supramolecular assocition of cellulose and its combination with lignin and hemicellulose provide physical and chemical barriers in plant tissue. in general the purposes of pretreatment are (1) enlargement of the available surface area and breakdown the cellulose crystal (2) partial depolymerization of cellulose, (3) solubolize lignin and/or hemicellulose (4) modification of enzyme accessibility to improve digestibility of cellulose (zhao et al. 2012). the process design that has a clear impact on the cellulose, hemicellulose and lignin fragments should be consider solemnly while selecting the pretreatment techniques and constrains (alvira et al. 2010). agricultural remains in bangladesh could be the potential source of bioethanol production. sugarcane bagasse is loosely bonded anatomical metric, composed of vasculer bundles surrounded by non-fibrous parenchymatic cell (jahan et al. 2009). usually it is available as agricultural residue and byproduct from sugar mill industries. in the year of 2015-16, there was 2,95,162 metric ton sugarcane bagasse was obtained from sugar mills of bangladesh (http://www.bsfic.gov.bd). to enrich cellulose content in biomass for enzymatic saccarification, current research has focused on various pretreatment processes. currently, scientists have gone through a lot of studies on different pretreatment techniques to remove the compact and rigid composition by open up the cellulosic structure (alvira et al. 2010). pretreatment technologies are commonly abandoned to reduce the structural barriers and boost cellulose availability based on not only chemicals such as acid, alkali, oxidant, etc. but also several treatment settings. alkali treatment is one of the most widespread and economical methods used for surface modification of lignocellulosic biomass. in the field of biorefinary, alkali pretreatment is intensively employed to develop the cellulosic materials both mechanically as well as chemically and such properties include tensile strength, dyeability, stability of dimension and reactivity (wu et al. 2011). in alkali pretreatment biomass is treated under moderate reaction conditions ensuring inexpensiveness, inflated recycling possibilities of water and chemical agents (mcintosh and vancov, 2010). usually alkali treatment is the most effective pretreatment for agricultural residues, herbaceous crops and hardwood containing low lignin content in the compariosn of softwood containing high lignin content (agbor et al. 2011; canilha et al. 2012). this research aims is to investigate the alkaline pretreatment repercussions based on the chemical structure, surface morphology, structure and enzymatic digestion of sugarcane bagasse for sugars and ethanol production. materials and methods sugarcane bagasse (sb) was taken from street juice vendor. warm tap water was used for washing purpose to eliminate the residual free sugars once again. this washing and pressing step was then repeated for three times. after that drying was done in an oven at 65oc for 16 h. crushing of dried bagasse was done successively using a locally made crusher and sieved (retsch, d-42759, haan, germany) to have the particle size of 20-40 mesh on average. before usage, the 20-40 mesh bagasse was kept at room temperature in an airtight plastic container (sujan et al. 2018). moisture and ash content moisture content of raw materials was measured using the astm d 4442-07 procedure. in a glass crucible, 2 grams of pretreatment sample containing 20-40 mesh were dried in oven at 105±2°c. the moisture content was expressed in percent wet basis and weight measurements were taken every 3 h. a muffle furnace was used for burning the oven-dried samples at 575±25°c for ash content determination following the astm standard e 1755-01. volatile matter the volatile matter analysis was carried out in accordance with astm standard d 271-48. four grams of raw materials were heated in a furnace at 950±20°c for seven minutes. the weight loss, excluding the weight of moisture pushed off at 105°c, is then used to calculate volatile matter. fixed carbon the difference between 100 and the total of volatile matter, moisture, and ash content was used to compute the fixed carbon percentage. chemical analysis the technical association of the pulp and paper industry (tappi) method detects α-cellulose (t 203 cm-99), pentosan (t 223 cm-01), klason lignin (t211 om-83), and acid soluble lignin (t um 250) on a dry basis. ultimate analysis ultimate analysis of samples was done by following the procedure astm standard d 5291-02. organic elemental analyzer (flash 2000, thermo scientific, usa) was used with a specific condition (reactor temp. 900°c, he: 250 kpa, o2: 250 kpa, tcd). low concentration alkali pretreatment different alkali concentration (0%, 2%, 4%, 6% and 8%), time (60, 90 and 120 min) and temperature (80, 100 and 120oc) were applied on raw material to check alkali effect on sb shown in table 3. a portion of the ground bagasse 20-40 mesh (10g) was taken into plastic zipper bag (temperature 80oc, figure 2a and 2b) and stainless-steel reactor (temperature 100oc and 120oc, figure 2c and 2d). different alkali concentration was applied during the pretreatment process (alkali to sb ratio ranging between 1:12). the mixture was heated at a particular temperature such as in a water bath (80oc) and oil bath (100oc and 120oc) for a desired length of time. in the course of pretreatment process the sample was manually mixed 2-3 times to attain proper alkali treatment. the treated sb was placed into a polyester bag to remove excess alkali water by pressing it. after that it was vigorously washed with tap water (repeated for five times) to remove the remaining alkali. finally the sb was dried in an oven at 65oc for 72 h and stored in a close container at room temperature for further experiment. regression model regression model has been developed for prediction of α-cellulose, pentosan and lignin in sb. the general form of the model is: y=α+α1x1 + α2x2+........................+αnxn + ε.......................(1) where α is the constant term. αi are the coefficient of variables xi. ε is the random error term which is minimized with simple least squares regression (slsr). regression coefficients of the independent variables namely alkali concentration, temperature and time are estimated by slsr method for developing regression model to predict α-cellulose, pentosan and lignin. efficiencies of these models are expressed by coefficient of multiple determination (r2) and adjusted r2. 2.9 separate hydrolysis and fermentation (shf) the hydrolysis experiment took place in 100 ml conical flux 10ml enzyme solution with 200 mg (2% dry wt.) in citrate buffer (0.05 m, ph 5.0) at 50°c for 48 h. in this case trichoderma viride was used for hydrolysis. hydrolysate was then heated for 15 min in a boiling water bath and centrifugation was done to remove solid particles. the supernatant was used for analysis of released sugars as described by jamal et al. (2011). during fermentation process according to firoz et al. (2012), 100 ml media was prepared and 0.5 g of commercial yeast saccharomyces cerevisiae was used as inoculum which showed good performance to converts sugar into bioethanol. this inoculated media mixture was poured in a suitable glassware and was kept in a shaking incubator for 48 h. 10 ml of this medium was then added into the flask and it was properly covered with aluminum foil. then it was placed in the incubator at 30oc for 24 h, 48 h, 72 h and 96 h for fermentation of sugars to bio-ethanol according to sujan et al. (2018). samples from hydrolysis and fermentation were performed by hplc. high performance liquid chromatography (hplc) in characterize part, concentration of sugars and ethanol were determined by hplc (ultimate 3000, thermo scientific, usa) method using hyper rez xp carbohydrate h+ 8 µm column (100×7.7 mm) equipped with a refractive index (shodex ri-101) detector. the mobile phase was degassed with deionized water with a flow rate of 0.7 ml/min and column temperature was maintained at 70°c. it is possible to measure the total sugar concentration in the hydrolysis liquid fraction by comparing its peak area detected by hplc with peak area of 1% standard sugar which consists of two sugars namely glucose and xylose (sujan et al. 2018). the same column which is specialized for fermentation broth analysis is used for ethanol detection. the kinetic parameters of ethanol fermentation were determined as follows (islam et al. 2019): crystallinity measurement x-ray diffraction (xrd) was used to determine the crystalline structure of the sb samples using a diffractometer (gbc xrd) and filtered copper k radiation (λ = 0.1542 nm) by a monochromator at 35.50 kv voltage and 28 ma current, with a speed of about 2o/min and scanning in the range of 10 80ºc. the crystallinity index (cri) was obtained from the ratio between the intensity of the 002 peak (i002, 2θ = 22.5) and the minimum dip (iam, 2 θ = 18.5) according to the following equation (roberta et al., 2012): cri (%) = [(i002 iam)/i002] ×100 ...................................... (2) where i002 is the highest peak intensity of plane 002 and iam is related to the amorphous structure. in present study, the average crystallite sizes were determined from the scherrer equation by using the diffraction pattern obtained from the 002 (hkl) lattice planes of cellulose samples d(hkl) = [(kλ / b(hkl) cos2θ] ............................................... (3) where d(hkl) (crystallite size), k (scherrer constant, 0.84), λ (x-ray wavelength, 0.154nm), b(hkl)(full width half maximum of the measured hkl reflection), and 2θ (corresponding bragg angle). scanning electron microscopy (sem) analysis in this research, sem (zeiss evo 18 sem) was used to detect the change of pretreated bagasse fibers. sem images were taken of different pretreated bagasse samples with acceleration voltage of 2.0 kv. results and discussion proximate analysis proximate analysis of sb sample (20-40 mesh) are presented in table i. primarily this analysis usually evaluate the fuel characteristics of raw materials. according to sun et al., 2009, higher moisture and ashcontent in samples lessen the heating value. ultimate analysis ultimate analysis denotes the elemental configuration of sb such as carbon, hydrogen, oxygen, nitrogen and sulfur which are shown in table ii. this examination helps to measure the percentage of carbon and hydrogen content in biomass that is responsible to determine the amount of air is required for complete combustion, composition of combustion gases and heat is generated by it (poddar et al. 2014). chemical properties raw sb contained 34.66±12% α-cellulose, 22.43±08% pentosan and 19.57±06% klason lignin in which 1.75±04% acid soluble lignin (dry basis) was detected by technical association of the pulp and paper industry (tappi) method. the chemical composition of sb was determined by acid hydrolysis and it was calculatedby hplc method as 45.35% glucose and 30.64% xylose (sujan et al., 2018). α-cellulose yield bagasse is mainly composed of cellulose, hemicellulose and lignin. besides these there are some extractives such as ash, wax, gum, pectin etc. during alkali pretreatment usually most of the extractives are removed with the increasing of alkali concentration. pretreatment of sb with different alkali concentration based on raw material (0%, 2%, 4%, 6% and 8%), time (60, 90 and 120 min) and temperature (80, 100 and 120oc) are shown in table iii. consequences of each independent experiment varying with alkali concentration, temperature and time on the α-cellulose yield were analyzed using matlab software. apparently, it was observed that α-cellulose yield was considerably increased with changes of alkali concentration ranging from 0% to 8% (34.66% to 63.58%). but no noticeable variation was observed in temperature-time alteration during pretreatment of sb. based on cellulose percentage obtained in treated bagasse, the optimum conditions for pretreatment reaction were selected as alkali concentration 8%, time 90 min and temperature 100oc. although cellulose content in treated sb was slowly increased with the increase of alkali concentration 12% attime 90 min and temperature 100oc but as a consequence of huge chemical consumption, recovery problem, chance of losses cellulose and hemicellulose, alkali concentrations for pretreatment above 8% was not considered as ideal concentration. effect of alkali concentration (ac), cooking time and temperature (temp) charge on α-cellulose yield as well as their statistical significance on the basis of f-test number are presented in regression equations (4). as shown in equations, cooking time at the maximum temperature had no significant effect on α-cellulose yield followed by alkali concentration charge. effect of temperature on α-cellulose yield was less in employed cooking conditions. for α-cellulose yield: α-cellulose yield = 82.05-0.151×temp-1.56×time-0.69×ac (r2=0.89, adjusted r2=0.87) ............................................. (4) for pentosan: pentosan = 13.58+0.086 × tem p + 0.006 × time+0.445 × ac (r2=0.67, adjusted r2=0.63) ............................................. (5) for lignin: lignin = 27.662-0.041×temp-0.001×time-01.242×ac (r2=0.93, adjusted r2=0.92) ............................................. (6) for predicting α-cellulose, percentage of pentosan and lignin, the most influential factor was alkali concentration and then cooking temperature for α-cellulose yield, which exhibited an almost linear dependence on both operational variables. the coefficient of determinations is good for α-cellulose yield and lignin percentage which hovers around 90 percent, although the figure is moderate more than 60 percent for pentosan. all these three models are significant (p<0.05) at 5% level of significance. in order to perceive the impact of alkali concentration and temperature on these three parameters, three-dimensional (3d) response surface plots were created by plotting the response (α-cellulose yield) pentosan and lignin on the z-axis versus the most influential one independent variable alkali concentration and temperature as shown in fig. 3 (a), (b) and (c). xrd analysis in 19th century the cellulose crystalline structure has been discovered and later it was verified by x-ray crystallography (meyer and misch, 1937; wilkie, 1961). the crystallinity index (cri) of non-woody biomass, such as grasses and agricultural residues, varies depending on the type of biomass. generally, non-woody biomass has a lower crystallinity index than woody biomass, typically ranging from 20-40%. the crystallinity index of non-woody biomass affects its digestibility and energy production potential.recently, researchers are being paid more attention on cellulose index because of its potential use in bioenergy production. since then several different models of cellulose index have been proposed. the most popular two-phase cellulose model describes cellulose chains as containing both crystalline (ordered) and amorphous (less ordered) region (park et al., 2010). alkali treatment of bagasse has been found to increase the crystallinity index of the bagasse. alkali treatment breaks down hemicellulose, making the cellulose molecules more ordered and crystalline, resulting in a higher crystallinity index. alkali treatment also increases the digestibility of the bagasse, making it easier to break down and therefore more suitable for bioenergy production. x-ray diffraction spectra of the sb and alkali treated sb were presented in figure 4. it was observed that the intensity of 101 and 002 peaks were gradually increased. the relative amount of crystalline cellulose (cri) in the total solid were calculated based on the equation (2) and obtained 18.68%, 24.80%, 27.23%, 32.69%, 36.45% and 39.19% for raw sb, 0%, 2%, 4%, 6% and 8% alkali treated sb samples respectively. the cri of alkali treated sb samples (not cellulose crystallinity) were intensely influenced by the composition of the samples. in case of lignocellulosic biomass examples, cellulose cri measured the relative amount of crystalline cellulose in the total solid. therefore, amorphous part of lignin and hemicellulose in biomass specimens were partially removed with the delignification process as a result the proportion of α-cellulose was increased and hence cri would be increased gradually. this interpretation could be proved by the fact that alkali-treated sb had higher cri than raw sb (zhao et al. 2010) and the portion of cellulose in the treated sb was also increased gradually. according to the equation 3, the average sizes of crystallite obtained were 3.28, 3.51, 3.63, 3.78, 3.90 and 4.06 nm for raw sb, 0%, 2%, 4%, 6% and 8% alkali treated sb samples respectively. the experimental data revealed that during delignification, the size of crystallite was increased. sem analysis sem is one of the most commanding tools widely used to investigate the lignocellulosic biomass surface (amiri and karimi, 2015). sem is usually employed for surface characterization, morphology and inspection of microstructure. in respect of biomass example through sem images we can compare the untreated and pretreated models which may lead to different insight into the biomass (karimi and taherzadeh, 2016). sem provides two-dimensional images of raw sb and alkali treated sb, which were taken and compared to the outcome of naoh treatment. all testers were coated with carbon tape and magnification of 500x was used. figure 4 shows the wall of raw sb (figure 6a) was intact where the alkali treated sb (figures 6c-6f), the cell wall was ruptured or splitted and hence packing of the fibers were partially loosened (firoz et al. 2012). sugar and ethanol yield enzymatic digestibility is the ability of enzymes to break down molecules into smaller molecules, such as glucose. it is used to measure the efficiency of enzyme-catalyzed reactions and the digestibility of cellulose. the enzymatic digestibility of a compound is affected by factors such as the compound's crystallinity index, the type of enzyme used, and the temperature and ph of the reaction. in this study the enzymatic digestibility of the alkali pretreated sb was improved by increasing pretreatment conditions. typically the pretreatment settings are selected by considering various factors such as feedstock characteristics, pretreatment chemical cost, energy consumption and recovery efficiency (wu et al. 2011). α-cellulose obtained by 8% alkali treated of sb was used for hydrolysis reaction and the reaction was carried out at an optimum condition set by sujan et al. (2018). the most effective enzymatic hydrolysis was taken place with trichoderma virideat 48 h and the theoretical yield of sugars i.e. glucose and xylose were obtained 89.59% and 61.23%, respectively. through fermentation process generated sugars were used to check ethanol production. yeast saccharomyces cerevisiae presented worthy performance to convert c6 sugar into ethanol when it was incubated at 30°c for 24 h and 16.81±0.32% ethanol yield was detected. conclusion α-cellulose yield was optimized by varying alkali concentration, temperature and cooking time. the most vital influencing factor for α-cellulose yield was alkali concentration and after that temperature performed a little bit. the optimum α-cellulose yield (63.58±0.05%) was obtained at 8% alkali concentration, 100oc and 90 minutes. in hydrolysis step of sb, trichoderma viridaewas used to convert 8% alkali treated sb into sugars and it was attained 89.59% glucose and 61.23% xylose which gave higher yield in compare with our previous study such as ball milled and mesh size varied sb sample (sujan et al. 2018). at fermentation step saccharomyces cerevisiae was used to convert hydrolysate of 8% alkali treated sb sample and ethanol yield was obtained 16.81±0.32% at 24 h. compositional analysis, imaging and crystallinity are three methods were performed. sem images can give different clues about sb including morphology, surface disruption and creation of highly accessible surface area iii) cri (18.68% to 39.19%) and crystal size (3.28 nm to 4.06 nm) of sb are increased with different alkali treatment (0%-8%). in this case it was observed that crystallinity, crystal size, accessible surface area, porosity, particle size, lignin and hemicellulose content and enzyme adsorption/desorption were acted as the most impressive factors for digestibility of sugarcane bagasse. acknowledgement authors would like to acknowledge pulp and paper division, bcsir for their cooperation. authors also like to thanks for the sincere assistance of md. abdul hamid, junior technician, ifrd, bcsir. references alvira p, tomás-pejó e, ballesteros m and negro mj (2010), pretreatment technologies for an efficient bioethanol production process based on enzymatic hydrolysis: a review, bioresource technology 101(13): 4851-4861. doi: org/10.1016/j.biortech.2009.11.093 agbor vb, cicek n, sparling r, berlin a and levin, db (2011), biomass pretreatment: fundamentals toward application, biotechnology advances 29(6): 675-685. doi: org/10.1016/j.biotechadv.2011.05.005 amiri h and karimi k (2015), improvement of acetone, butanol, and ethanol production from woody biomass using organosolv pretreatment, bioprocess and biosystems engineering 38(10): 1959-1972. astm (2007), standard test members for instrumental determination of c, h, n in petroleum products and lubricants. astm d5291-02, astm international, west conshohocken, pa. canilha l, chandel ak, suzane dos santos milessi t, antunes faf, luiz da costa freitas w, das graças almeida felipe m and da silva ss (2012), bioconversion of sugarcane biomass into ethanol: an overview about composition, pretreatment methods, detoxification of hydrolysates, enzymatic saccharification and ethanol fermentation. journal of biomedicine and biotechnology, doi: org/10.1155/2012/989572 den w, sharma vk, lee m, nadadur g and varma rs (2018), lignocellulosic biomass transformations via greener oxidative pretreatment processes: access to energy and value-added chemicals, frontiers in chemistry 6: 141. doi: org/10.3389/fchem.2018.00141 ahmed fm, rahman sr and gomes dj (2012), saccharification of sugarcane bagasse by enzymatic treatment for bioethanol production, malays j microbiol 8(2), 97-103. hirani ah, javed n, asif m, basu sk and kumar a (2018), a review on first-and second-generation biofuel productions. in biofuels: greenhouse gas mitigation and global warming, springer, new delhi, pp 141-154. doi: 10.1007/978-81-322-3763-1_8 islam mz, asad ma, hossain mt, paul sc and sujan sma (2019), bioethanol production from banana pseudostem by using separate and cocultures of cellulase enzyme with saccharomyces cerevisiae, journal of environmental science and technology 12(4): 157-163. jahan ms, saeed a, ni y and he z (2009), pre-extraction and its impact on the alkaline pulping of bagasse, journal of biobased materials and bioenergy 3(4): 380-385. doi: org/10.1166/jbmb.2009.1053 janker-obermeier i, sieber v, faulstich mand schieder d (2012), solubilization of hemicellulose and lignin from wheat straw through microwave-assisted alkali treatment, industrial crops and products 39: 198-203. doi: org/10.1016/j.indcrop.2012.02.022 karimi k and taherzadeh mj (2016), a critical review of analytical methods in pretreatment of lignocelluloses: composition, imaging, and crystallinity, bioresource technology 200: 1008-1018. doi: org/10.1016/j. biortech.2015.11.022 maryana r, ma’rifatun d, wheni ai, satriyo kw and rizal wa (2014), alkaline pretreatment on sugarcane bagasse for bioethanol production, energy procedia, 47: 250-254. doi: org/10.1016/j.egypro.2014.01.221 mcintosh sand vancov t (2010), enhanced enzyme saccharification of sorghum bicolor straw using dilute alkali pretreatment, bioresource technology 101(17): 6718-6727. doi: org/10.1016/j.biortech.2010.03.116 meyer kh and misch l (1937), positions des atomes dans le nouveau modele spatial de la cellulose. helvetica chimica acta 20(1): 232-244. doi: org/10. 1002/hlca.19370200134 park s, baker jo, himmel me, parilla pa and johnson dk (2010), cellulose crystallinity index: measurement techniques and their impact on interpreting cellulase performance, biotechnology for biofuels 3(1): 10. sujan sma, bari ml and fakhruddin an (2018), effects of physical pretreatment (crushing and ball milling) on sugarcane bagasse for bioethanol production, bangladesh journal of botany 147(2): 257-64. wilkie js (1961), carl nägeli and the fine structure of living matter, nature 190: 1145-1150. wu l, arakane m, ike m, wada m, takai t, gau mand tokuyasu k (2011), low temperature alkali pretreatment for improving enzymatic digestibility of sweet sorghum bagasse for ethanol production, bioresource technology 102(7): 4793-4799. zhang w, okubayashi s and bechtold t (2005), fibrillation tendency of cellulosic fibers-part 4. effects of alkali pretreatment of various cellulosic fibers, carbohydrate polymers. 61(4): 427-433. zhao x, van der heide e, zhang tand liu d (2010), delignification of sugarcane bagasse with alkali and peracetic acid and characterization of the pulp, bioresources 5(3): 1565-1580. zhao x, zhang land liu d (2012), biomass recalcitrance. part ii: fundamentals of different pre‐treatments to increase the enzymatic digestibility of lignocellulose, biofuels, bioproducts and biorefining 6(5): 561-579. doi: https://doi.org/10.3329/bjsir.v58i2.66990 received: 01 february 2023 revised: 04 april 2023 accepted: 11 april 2023 optimization of alkali concentration in the pretreatment of sugarcane bagasse 58(2) 202390 composed of vasculer bundles surrounded by non-fibrous parenchymatic cell (jahan et al. 2009). usually it is available as agricultural residue and byproduct from sugar mill industries. in the year of 2015-16, there was 2,95,162 metric ton sugarcane bagasse was obtained from sugar mills of bangladesh (http://www.bsfic.gov.bd). to enrich cellulose content in biomass for enzymatic saccarification, current research has focused on various pretreatment processes. currently, scientists have gone through a lot of studies on different pretreatment techniques to remove the compact and rigid composition by open up the cellulosic structure (alvira et al. 2010). pretreatment technologies are commonly abandoned to reduce the structural barriers and boost cellulose availability based on not only chemicals such as acid, alkali, oxidant, etc. but also several treatment settings. alkali treatment is one of the most widespread and economical methods used for surface modification of lignocellulosic biomass. in the field of biorefinary, alkali pretreatment is intensively employed to develop the cellulosic materials both mechanically as well as chemically and such properties include tensile strength, dyeability, stability of dimension and reactivity (wu et al. 2011). in alkali pretreatment biomass is treated under moderate reaction conditions ensuring inexpensiveness, inflated recycling possibilities of water and chemical agents (mcintosh and vancov, 2010). usually alkali treatment is the most effective pretreatment for agricultural residues, herbaceous crops and hardwood containing low lignin content in the compariosn of softwood containing high lignin content (agbor et al. 2011; canilha et al. 2012). this research aims is to investigate the alkaline pretreatment repercussions based on the chemical structure, surface morphology, structure and enzymatic digestion of sugarcane bagasse for sugars and ethanol production. materials and methods sugarcane bagasse (sb) was taken from street juice vendor. warm tap water was used for washing purpose to eliminate the residual free sugars once again. this washing and pressing step was then repeated for three times. after that drying was done in an oven at 65oc for 16 h. crushing of dried bagasse was done successively using a locally made crusher and sieved (retsch, d-42759, haan, germany) to have the particle size of 20-40 mesh on average. before usage, the 20-40 mesh bagasse was kept at room temperature in an airtight plastic container (sujan et al. 2018). moisture and ash content moisture content of raw materials was measured using the astm d 4442-07 procedure. in a glass crucible, 2 grams of pretreatment sample containing 20-40 mesh were dried in oven at 105±2°c. the moisture content was expressed in percent wet basis and weight measurements were taken every 3 h. a muffle furnace was used for burning the oven-dried samples at 575±25°c for ash content determination following the astm standard e 1755-01. volatile matter the volatile matter analysis was carried out in accordance with astm standard d 271-48. four grams of raw materials were heated in a furnace at 950±20°c for seven minutes. the weight loss, excluding the weight of moisture pushed off at 105°c, is then used to calculate volatile matter. fixed carbon the difference between 100 and the total of volatile matter, moisture, and ash content was used to compute the fixed carbon percentage. chemical analysis the technical association of the pulp and paper industry (tappi) method detects α-cellulose (t 203 cm-99), pentosan (t 223 cm-01), klason lignin (t211 om-83), and acid soluble lignin (t um 250) on a dry basis. ultimate analysis ultimate analysis of samples was done by following the procedure astm standard d 5291-02. organic elemental analyzer (flash 2000, thermo scientific, usa) was used with a specific condition (reactor temp. 900°c, he: 250 kpa, o2: 250 kpa, tcd). low concentration alkali pretreatment different alkali concentration (0%, 2%, 4%, 6% and 8%), time (60, 90 and 120 min) and temperature (80, 100 and 120oc) were applied on raw material to check alkali effect on sb shown in table 3. a portion of the ground bagasse 20-40 mesh (10g) was taken into plastic zipper bag (temperature 80oc, figure 2a and 2b) and stainless-steel reactor (temperature 100oc and 120oc, figure 2c and 2d). different alkali concentration was applied during the pretreatment process (alkali to sb ratio ranging between 1:12). the mixture was heated at a particular temperature such as in a water bath (80oc) and oil bath (100oc and 120oc) for a desired length of time. in the course of pretreatment process the sample was manually mixed 2-3 times to attain proper alkali treatment. the treated sb was placed into a polyester bag to remove excess alkali water by pressing it. after that it was vigorously washed with tap water (repeated for five times) to remove the remaining alkali. finally the sb was dried in an oven at 65oc for 72 h and stored in a close container at room temperature for further experiment. regression model regression model has been developed for prediction of α-cellulose, pentosan and lignin in sb. the general form of the model is: y=α+α1x1 + α2x2+........................+αnxn + ε.......................(1) where α is the constant term. αi are the coefficient of variables xi. ε is the random error term which is minimized with simple least squares regression (slsr). regression coefficients of the independent variables namely alkali concentration, temperature and time are estimated by slsr method for developing regression model to predict α-cellulose, pentosan and lignin. efficiencies of these models are expressed by coefficient of multiple determination (r2) and adjusted r2. 2.9 separate hydrolysis and fermentation (shf) the hydrolysis experiment took place in 100 ml conical flux 10ml enzyme solution with 200 mg (2% dry wt.) in citrate buffer (0.05 m, ph 5.0) at 50°c for 48 h. in this case trichoderma viride was used for hydrolysis. hydrolysate was then heated for 15 min in a boiling water bath and centrifugation was done to remove solid particles. the supernatant was used for analysis of released sugars as described by jamal et al. (2011). during fermentation process according to firoz et al. (2012), 100 ml media was prepared and 0.5 g of commercial yeast saccharomyces cerevisiae was used as inoculum which showed good performance to converts sugar into bioethanol. this inoculated media mixture was poured in a suitable glassware and was kept in a shaking incubator for 48 h. 10 ml of this medium was then added into the flask and it was properly covered with aluminum foil. then it was placed in the incubator at 30oc for 24 h, 48 h, 72 h and 96 h for fermentation of sugars to bio-ethanol according to sujan et al. (2018). samples from hydrolysis and fermentation were performed by hplc. high performance liquid chromatography (hplc) in characterize part, concentration of sugars and ethanol were determined by hplc (ultimate 3000, thermo scientific, usa) method using hyper rez xp carbohydrate h+ 8 µm column (100×7.7 mm) equipped with a refractive index (shodex ri-101) detector. the mobile phase was degassed with deionized water with a flow rate of 0.7 ml/min and column temperature was maintained at 70°c. it is possible to measure the total sugar concentration in the hydrolysis liquid fraction by comparing its peak area detected by hplc with peak area of 1% standard sugar which consists of two sugars namely glucose and xylose (sujan et al. 2018). the same column which is specialized for fermentation broth analysis is used for ethanol detection. the kinetic parameters of ethanol fermentation were determined as follows (islam et al. 2019): crystallinity measurement x-ray diffraction (xrd) was used to determine the crystalline structure of the sb samples using a diffractometer (gbc xrd) and filtered copper k radiation (λ = 0.1542 nm) by a monochromator at 35.50 kv voltage and 28 ma current, with a speed of about 2o/min and scanning in the range of 10 80ºc. the crystallinity index (cri) was obtained from the ratio between the intensity of the 002 peak (i002, 2θ = 22.5) and the minimum dip (iam, 2 θ = 18.5) according to the following equation (roberta et al., 2012): cri (%) = [(i002 iam)/i002] ×100 ...................................... (2) where i002 is the highest peak intensity of plane 002 and iam is related to the amorphous structure. in present study, the average crystallite sizes were determined from the scherrer equation by using the diffraction pattern obtained from the 002 (hkl) lattice planes of cellulose samples d(hkl) = [(kλ / b(hkl) cos2θ] ............................................... (3) where d(hkl) (crystallite size), k (scherrer constant, 0.84), λ (x-ray wavelength, 0.154nm), b(hkl)(full width half maximum of the measured hkl reflection), and 2θ (corresponding bragg angle). scanning electron microscopy (sem) analysis in this research, sem (zeiss evo 18 sem) was used to detect the change of pretreated bagasse fibers. sem images were taken of different pretreated bagasse samples with acceleration voltage of 2.0 kv. results and discussion proximate analysis proximate analysis of sb sample (20-40 mesh) are presented in table i. primarily this analysis usually evaluate the fuel characteristics of raw materials. according to sun et al., 2009, higher moisture and ashcontent in samples lessen the heating value. ultimate analysis ultimate analysis denotes the elemental configuration of sb such as carbon, hydrogen, oxygen, nitrogen and sulfur which are shown in table ii. this examination helps to measure the percentage of carbon and hydrogen content in biomass that is responsible to determine the amount of air is required for complete combustion, composition of combustion gases and heat is generated by it (poddar et al. 2014). chemical properties raw sb contained 34.66±12% α-cellulose, 22.43±08% pentosan and 19.57±06% klason lignin in which 1.75±04% acid soluble lignin (dry basis) was detected by technical association of the pulp and paper industry (tappi) method. the chemical composition of sb was determined by acid hydrolysis and it was calculatedby hplc method as 45.35% glucose and 30.64% xylose (sujan et al., 2018). α-cellulose yield bagasse is mainly composed of cellulose, hemicellulose and lignin. besides these there are some extractives such as ash, wax, gum, pectin etc. during alkali pretreatment usually most of the extractives are removed with the increasing of alkali concentration. pretreatment of sb with different alkali concentration based on raw material (0%, 2%, 4%, 6% and 8%), time (60, 90 and 120 min) and temperature (80, 100 and 120oc) are shown in table iii. consequences of each independent experiment varying with alkali concentration, temperature and time on the α-cellulose yield were analyzed using matlab software. apparently, it was observed that α-cellulose yield was considerably increased with changes of alkali concentration ranging from 0% to 8% (34.66% to 63.58%). but no noticeable variation was observed in temperature-time alteration during pretreatment of sb. based on cellulose percentage obtained in treated bagasse, the optimum conditions for pretreatment reaction were selected as alkali concentration 8%, time 90 min and temperature 100oc. although cellulose content in treated sb was slowly increased with the increase of alkali concentration 12% attime 90 min and temperature 100oc but as a consequence of huge chemical consumption, recovery problem, chance of losses cellulose and hemicellulose, alkali concentrations for pretreatment above 8% was not considered as ideal concentration. effect of alkali concentration (ac), cooking time and temperature (temp) charge on α-cellulose yield as well as their statistical significance on the basis of f-test number are presented in regression equations (4). as shown in equations, cooking time at the maximum temperature had no significant effect on α-cellulose yield followed by alkali concentration charge. effect of temperature on α-cellulose yield was less in employed cooking conditions. for α-cellulose yield: α-cellulose yield = 82.05-0.151×temp-1.56×time-0.69×ac (r2=0.89, adjusted r2=0.87) ............................................. (4) for pentosan: pentosan = 13.58+0.086 × tem p + 0.006 × time+0.445 × ac (r2=0.67, adjusted r2=0.63) ............................................. (5) for lignin: lignin = 27.662-0.041×temp-0.001×time-01.242×ac (r2=0.93, adjusted r2=0.92) ............................................. (6) for predicting α-cellulose, percentage of pentosan and lignin, the most influential factor was alkali concentration and then cooking temperature for α-cellulose yield, which exhibited an almost linear dependence on both operational variables. the coefficient of determinations is good for α-cellulose yield and lignin percentage which hovers around 90 percent, although the figure is moderate more than 60 percent for pentosan. all these three models are significant (p<0.05) at 5% level of significance. in order to perceive the impact of alkali concentration and temperature on these three parameters, three-dimensional (3d) response surface plots were created by plotting the response (α-cellulose yield) pentosan and lignin on the z-axis versus the most influential one independent variable alkali concentration and temperature as shown in fig. 3 (a), (b) and (c). xrd analysis in 19th century the cellulose crystalline structure has been discovered and later it was verified by x-ray crystallography (meyer and misch, 1937; wilkie, 1961). the crystallinity index (cri) of non-woody biomass, such as grasses and agricultural residues, varies depending on the type of biomass. generally, non-woody biomass has a lower crystallinity index than woody biomass, typically ranging from 20-40%. the crystallinity index of non-woody biomass affects its digestibility and energy production potential.recently, researchers are being paid more attention on cellulose index because of its potential use in bioenergy production. since then several different models of cellulose index have been proposed. the most popular two-phase cellulose model describes cellulose chains as containing both crystalline (ordered) and amorphous (less ordered) region (park et al., 2010). alkali treatment of bagasse has been found to increase the crystallinity index of the bagasse. alkali treatment breaks down hemicellulose, making the cellulose molecules more ordered and crystalline, resulting in a higher crystallinity index. alkali treatment also increases the digestibility of the bagasse, making it easier to break down and therefore more suitable for bioenergy production. x-ray diffraction spectra of the sb and alkali treated sb were presented in figure 4. it was observed that the intensity of 101 and 002 peaks were gradually increased. the relative amount of crystalline cellulose (cri) in the total solid were calculated based on the equation (2) and obtained 18.68%, 24.80%, 27.23%, 32.69%, 36.45% and 39.19% for raw sb, 0%, 2%, 4%, 6% and 8% alkali treated sb samples respectively. the cri of alkali treated sb samples (not cellulose crystallinity) were intensely influenced by the composition of the samples. in case of lignocellulosic biomass examples, cellulose cri measured the relative amount of crystalline cellulose in the total solid. therefore, amorphous part of lignin and hemicellulose in biomass specimens were partially removed with the delignification process as a result the proportion of α-cellulose was increased and hence cri would be increased gradually. this interpretation could be proved by the fact that alkali-treated sb had higher cri than raw sb (zhao et al. 2010) and the portion of cellulose in the treated sb was also increased gradually. according to the equation 3, the average sizes of crystallite obtained were 3.28, 3.51, 3.63, 3.78, 3.90 and 4.06 nm for raw sb, 0%, 2%, 4%, 6% and 8% alkali treated sb samples respectively. the experimental data revealed that during delignification, the size of crystallite was increased. sem analysis sem is one of the most commanding tools widely used to investigate the lignocellulosic biomass surface (amiri and karimi, 2015). sem is usually employed for surface characterization, morphology and inspection of microstructure. in respect of biomass example through sem images we can compare the untreated and pretreated models which may lead to different insight into the biomass (karimi and taherzadeh, 2016). sem provides two-dimensional images of raw sb and alkali treated sb, which were taken and compared to the outcome of naoh treatment. all testers were coated with carbon tape and magnification of 500x was used. figure 4 shows the wall of raw sb (figure 6a) was intact where the alkali treated sb (figures 6c-6f), the cell wall was ruptured or splitted and hence packing of the fibers were partially loosened (firoz et al. 2012). sugar and ethanol yield enzymatic digestibility is the ability of enzymes to break down molecules into smaller molecules, such as glucose. it is used to measure the efficiency of enzyme-catalyzed reactions and the digestibility of cellulose. the enzymatic digestibility of a compound is affected by factors such as the compound's crystallinity index, the type of enzyme used, and the temperature and ph of the reaction. in this study the enzymatic digestibility of the alkali pretreated sb was improved by increasing pretreatment conditions. typically the pretreatment settings are selected by considering various factors such as feedstock characteristics, pretreatment chemical cost, energy consumption and recovery efficiency (wu et al. 2011). α-cellulose obtained by 8% alkali treated of sb was used for hydrolysis reaction and the reaction was carried out at an optimum condition set by sujan et al. (2018). the most effective enzymatic hydrolysis was taken place with trichoderma virideat 48 h and the theoretical yield of sugars i.e. glucose and xylose were obtained 89.59% and 61.23%, respectively. through fermentation process generated sugars were used to check ethanol production. yeast saccharomyces cerevisiae presented worthy performance to convert c6 sugar into ethanol when it was incubated at 30°c for 24 h and 16.81±0.32% ethanol yield was detected. conclusion α-cellulose yield was optimized by varying alkali concentration, temperature and cooking time. the most vital influencing factor for α-cellulose yield was alkali concentration and after that temperature performed a little bit. the optimum α-cellulose yield (63.58±0.05%) was obtained at 8% alkali concentration, 100oc and 90 minutes. in hydrolysis step of sb, trichoderma viridaewas used to convert 8% alkali treated sb into sugars and it was attained 89.59% glucose and 61.23% xylose which gave higher yield in compare with our previous study such as ball milled and mesh size varied sb sample (sujan et al. 2018). at fermentation step saccharomyces cerevisiae was used to convert hydrolysate of 8% alkali treated sb sample and ethanol yield was obtained 16.81±0.32% at 24 h. compositional analysis, imaging and crystallinity are three methods were performed. sem images can give different clues about sb including morphology, surface disruption and creation of highly accessible surface area iii) cri (18.68% to 39.19%) and crystal size (3.28 nm to 4.06 nm) of sb are increased with different alkali treatment (0%-8%). in this case it was observed that crystallinity, crystal size, accessible surface area, porosity, particle size, lignin and hemicellulose content and enzyme adsorption/desorption were acted as the most impressive factors for digestibility of sugarcane bagasse. acknowledgement authors would like to acknowledge pulp and paper division, bcsir for their cooperation. authors also like to thanks for the sincere assistance of md. abdul hamid, junior technician, ifrd, bcsir. references alvira p, tomás-pejó e, ballesteros m and negro mj (2010), pretreatment technologies for an efficient bioethanol production process based on enzymatic hydrolysis: a review, bioresource technology 101(13): 4851-4861. doi: org/10.1016/j.biortech.2009.11.093 agbor vb, cicek n, sparling r, berlin a and levin, db (2011), biomass pretreatment: fundamentals toward application, biotechnology advances 29(6): 675-685. doi: org/10.1016/j.biotechadv.2011.05.005 amiri h and karimi k (2015), improvement of acetone, butanol, and ethanol production from woody biomass using organosolv pretreatment, bioprocess and biosystems engineering 38(10): 1959-1972. astm (2007), standard test members for instrumental determination of c, h, n in petroleum products and lubricants. astm d5291-02, astm international, west conshohocken, pa. canilha l, chandel ak, suzane dos santos milessi t, antunes faf, luiz da costa freitas w, das graças almeida felipe m and da silva ss (2012), bioconversion of sugarcane biomass into ethanol: an overview about composition, pretreatment methods, detoxification of hydrolysates, enzymatic saccharification and ethanol fermentation. journal of biomedicine and biotechnology, doi: org/10.1155/2012/989572 den w, sharma vk, lee m, nadadur g and varma rs (2018), lignocellulosic biomass transformations via greener oxidative pretreatment processes: access to energy and value-added chemicals, frontiers in chemistry 6: 141. doi: org/10.3389/fchem.2018.00141 ahmed fm, rahman sr and gomes dj (2012), saccharification of sugarcane bagasse by enzymatic treatment for bioethanol production, malays j microbiol 8(2), 97-103. hirani ah, javed n, asif m, basu sk and kumar a (2018), a review on first-and second-generation biofuel productions. in biofuels: greenhouse gas mitigation and global warming, springer, new delhi, pp 141-154. doi: 10.1007/978-81-322-3763-1_8 islam mz, asad ma, hossain mt, paul sc and sujan sma (2019), bioethanol production from banana pseudostem by using separate and cocultures of cellulase enzyme with saccharomyces cerevisiae, journal of environmental science and technology 12(4): 157-163. jahan ms, saeed a, ni y and he z (2009), pre-extraction and its impact on the alkaline pulping of bagasse, journal of biobased materials and bioenergy 3(4): 380-385. doi: org/10.1166/jbmb.2009.1053 janker-obermeier i, sieber v, faulstich mand schieder d (2012), solubilization of hemicellulose and lignin from wheat straw through microwave-assisted alkali treatment, industrial crops and products 39: 198-203. doi: org/10.1016/j.indcrop.2012.02.022 karimi k and taherzadeh mj (2016), a critical review of analytical methods in pretreatment of lignocelluloses: composition, imaging, and crystallinity, bioresource technology 200: 1008-1018. doi: org/10.1016/j. biortech.2015.11.022 maryana r, ma’rifatun d, wheni ai, satriyo kw and rizal wa (2014), alkaline pretreatment on sugarcane bagasse for bioethanol production, energy procedia, 47: 250-254. doi: org/10.1016/j.egypro.2014.01.221 mcintosh sand vancov t (2010), enhanced enzyme saccharification of sorghum bicolor straw using dilute alkali pretreatment, bioresource technology 101(17): 6718-6727. doi: org/10.1016/j.biortech.2010.03.116 meyer kh and misch l (1937), positions des atomes dans le nouveau modele spatial de la cellulose. helvetica chimica acta 20(1): 232-244. doi: org/10. 1002/hlca.19370200134 park s, baker jo, himmel me, parilla pa and johnson dk (2010), cellulose crystallinity index: measurement techniques and their impact on interpreting cellulase performance, biotechnology for biofuels 3(1): 10. sujan sma, bari ml and fakhruddin an (2018), effects of physical pretreatment (crushing and ball milling) on sugarcane bagasse for bioethanol production, bangladesh journal of botany 147(2): 257-64. wilkie js (1961), carl nägeli and the fine structure of living matter, nature 190: 1145-1150. wu l, arakane m, ike m, wada m, takai t, gau mand tokuyasu k (2011), low temperature alkali pretreatment for improving enzymatic digestibility of sweet sorghum bagasse for ethanol production, bioresource technology 102(7): 4793-4799. zhang w, okubayashi s and bechtold t (2005), fibrillation tendency of cellulosic fibers-part 4. effects of alkali pretreatment of various cellulosic fibers, carbohydrate polymers. 61(4): 427-433. zhao x, van der heide e, zhang tand liu d (2010), delignification of sugarcane bagasse with alkali and peracetic acid and characterization of the pulp, bioresources 5(3): 1565-1580. zhao x, zhang land liu d (2012), biomass recalcitrance. part ii: fundamentals of different pre‐treatments to increase the enzymatic digestibility of lignocellulose, biofuels, bioproducts and biorefining 6(5): 561-579. fig. 1. 20-40 mesh size sb sujan, hossain, uddin and fakhruddin 91 composed of vasculer bundles surrounded by non-fibrous parenchymatic cell (jahan et al. 2009). usually it is available as agricultural residue and byproduct from sugar mill industries. in the year of 2015-16, there was 2,95,162 metric ton sugarcane bagasse was obtained from sugar mills of bangladesh (http://www.bsfic.gov.bd). to enrich cellulose content in biomass for enzymatic saccarification, current research has focused on various pretreatment processes. currently, scientists have gone through a lot of studies on different pretreatment techniques to remove the compact and rigid composition by open up the cellulosic structure (alvira et al. 2010). pretreatment technologies are commonly abandoned to reduce the structural barriers and boost cellulose availability based on not only chemicals such as acid, alkali, oxidant, etc. but also several treatment settings. alkali treatment is one of the most widespread and economical methods used for surface modification of lignocellulosic biomass. in the field of biorefinary, alkali pretreatment is intensively employed to develop the cellulosic materials both mechanically as well as chemically and such properties include tensile strength, dyeability, stability of dimension and reactivity (wu et al. 2011). in alkali pretreatment biomass is treated under moderate reaction conditions ensuring inexpensiveness, inflated recycling possibilities of water and chemical agents (mcintosh and vancov, 2010). usually alkali treatment is the most effective pretreatment for agricultural residues, herbaceous crops and hardwood containing low lignin content in the compariosn of softwood containing high lignin content (agbor et al. 2011; canilha et al. 2012). this research aims is to investigate the alkaline pretreatment repercussions based on the chemical structure, surface morphology, structure and enzymatic digestion of sugarcane bagasse for sugars and ethanol production. materials and methods sugarcane bagasse (sb) was taken from street juice vendor. warm tap water was used for washing purpose to eliminate the residual free sugars once again. this washing and pressing step was then repeated for three times. after that drying was done in an oven at 65oc for 16 h. crushing of dried bagasse was done successively using a locally made crusher and sieved (retsch, d-42759, haan, germany) to have the particle size of 20-40 mesh on average. before usage, the 20-40 mesh bagasse was kept at room temperature in an airtight plastic container (sujan et al. 2018). moisture and ash content moisture content of raw materials was measured using the astm d 4442-07 procedure. in a glass crucible, 2 grams of pretreatment sample containing 20-40 mesh were dried in oven at 105±2°c. the moisture content was expressed in percent wet basis and weight measurements were taken every 3 h. a muffle furnace was used for burning the oven-dried samples at 575±25°c for ash content determination following the astm standard e 1755-01. volatile matter the volatile matter analysis was carried out in accordance with astm standard d 271-48. four grams of raw materials were heated in a furnace at 950±20°c for seven minutes. the weight loss, excluding the weight of moisture pushed off at 105°c, is then used to calculate volatile matter. fixed carbon the difference between 100 and the total of volatile matter, moisture, and ash content was used to compute the fixed carbon percentage. chemical analysis the technical association of the pulp and paper industry (tappi) method detects α-cellulose (t 203 cm-99), pentosan (t 223 cm-01), klason lignin (t211 om-83), and acid soluble lignin (t um 250) on a dry basis. ultimate analysis ultimate analysis of samples was done by following the procedure astm standard d 5291-02. organic elemental analyzer (flash 2000, thermo scientific, usa) was used with a specific condition (reactor temp. 900°c, he: 250 kpa, o2: 250 kpa, tcd). low concentration alkali pretreatment different alkali concentration (0%, 2%, 4%, 6% and 8%), time (60, 90 and 120 min) and temperature (80, 100 and 120oc) were applied on raw material to check alkali effect on sb shown in table 3. a portion of the ground bagasse 20-40 mesh (10g) was taken into plastic zipper bag (temperature 80oc, figure 2a and 2b) and stainless-steel reactor (temperature 100oc and 120oc, figure 2c and 2d). different alkali concentration was applied during the pretreatment process (alkali to sb ratio ranging between 1:12). the mixture was heated at a particular temperature such as in a water bath (80oc) and oil bath (100oc and 120oc) for a desired length of time. in the course of pretreatment process the sample was manually mixed 2-3 times to attain proper alkali treatment. the treated sb was placed into a polyester bag to remove excess alkali water by pressing it. after that it was vigorously washed with tap water (repeated for five times) to remove the remaining alkali. finally the sb was dried in an oven at 65oc for 72 h and stored in a close container at room temperature for further experiment. regression model regression model has been developed for prediction of α-cellulose, pentosan and lignin in sb. the general form of the model is: y=α+α1x1 + α2x2+........................+αnxn + ε.......................(1) where α is the constant term. αi are the coefficient of variables xi. ε is the random error term which is minimized with simple least squares regression (slsr). regression coefficients of the independent variables namely alkali concentration, temperature and time are estimated by slsr method for developing regression model to predict α-cellulose, pentosan and lignin. efficiencies of these models are expressed by coefficient of multiple determination (r2) and adjusted r2. 2.9 separate hydrolysis and fermentation (shf) the hydrolysis experiment took place in 100 ml conical flux 10ml enzyme solution with 200 mg (2% dry wt.) in citrate buffer (0.05 m, ph 5.0) at 50°c for 48 h. in this case trichoderma viride was used for hydrolysis. hydrolysate was then heated for 15 min in a boiling water bath and centrifugation was done to remove solid particles. the supernatant was used for analysis of released sugars as described by jamal et al. (2011). during fermentation process according to firoz et al. (2012), 100 ml media was prepared and 0.5 g of commercial yeast saccharomyces cerevisiae was used as inoculum which showed good performance to converts sugar into bioethanol. this inoculated media mixture was poured in a suitable glassware and was kept in a shaking incubator for 48 h. 10 ml of this medium was then added into the flask and it was properly covered with aluminum foil. then it was placed in the incubator at 30oc for 24 h, 48 h, 72 h and 96 h for fermentation of sugars to bio-ethanol according to sujan et al. (2018). samples from hydrolysis and fermentation were performed by hplc. high performance liquid chromatography (hplc) in characterize part, concentration of sugars and ethanol were determined by hplc (ultimate 3000, thermo scientific, usa) method using hyper rez xp carbohydrate h+ 8 µm column (100×7.7 mm) equipped with a refractive index (shodex ri-101) detector. the mobile phase was degassed with deionized water with a flow rate of 0.7 ml/min and column temperature was maintained at 70°c. it is possible to measure the total sugar concentration in the hydrolysis liquid fraction by comparing its peak area detected by hplc with peak area of 1% standard sugar which consists of two sugars namely glucose and xylose (sujan et al. 2018). the same column which is specialized for fermentation broth analysis is used for ethanol detection. the kinetic parameters of ethanol fermentation were determined as follows (islam et al. 2019): crystallinity measurement x-ray diffraction (xrd) was used to determine the crystalline structure of the sb samples using a diffractometer (gbc xrd) and filtered copper k radiation (λ = 0.1542 nm) by a monochromator at 35.50 kv voltage and 28 ma current, with a speed of about 2o/min and scanning in the range of 10 80ºc. the crystallinity index (cri) was obtained from the ratio between the intensity of the 002 peak (i002, 2θ = 22.5) and the minimum dip (iam, 2 θ = 18.5) according to the following equation (roberta et al., 2012): cri (%) = [(i002 iam)/i002] ×100 ...................................... (2) where i002 is the highest peak intensity of plane 002 and iam is related to the amorphous structure. in present study, the average crystallite sizes were determined from the scherrer equation by using the diffraction pattern obtained from the 002 (hkl) lattice planes of cellulose samples d(hkl) = [(kλ / b(hkl) cos2θ] ............................................... (3) where d(hkl) (crystallite size), k (scherrer constant, 0.84), λ (x-ray wavelength, 0.154nm), b(hkl)(full width half maximum of the measured hkl reflection), and 2θ (corresponding bragg angle). scanning electron microscopy (sem) analysis in this research, sem (zeiss evo 18 sem) was used to detect the change of pretreated bagasse fibers. sem images were taken of different pretreated bagasse samples with acceleration voltage of 2.0 kv. results and discussion proximate analysis proximate analysis of sb sample (20-40 mesh) are presented in table i. primarily this analysis usually evaluate the fuel characteristics of raw materials. according to sun et al., 2009, higher moisture and ashcontent in samples lessen the heating value. ultimate analysis ultimate analysis denotes the elemental configuration of sb such as carbon, hydrogen, oxygen, nitrogen and sulfur which are shown in table ii. this examination helps to measure the percentage of carbon and hydrogen content in biomass that is responsible to determine the amount of air is required for complete combustion, composition of combustion gases and heat is generated by it (poddar et al. 2014). chemical properties raw sb contained 34.66±12% α-cellulose, 22.43±08% pentosan and 19.57±06% klason lignin in which 1.75±04% acid soluble lignin (dry basis) was detected by technical association of the pulp and paper industry (tappi) method. the chemical composition of sb was determined by acid hydrolysis and it was calculatedby hplc method as 45.35% glucose and 30.64% xylose (sujan et al., 2018). α-cellulose yield bagasse is mainly composed of cellulose, hemicellulose and lignin. besides these there are some extractives such as ash, wax, gum, pectin etc. during alkali pretreatment usually most of the extractives are removed with the increasing of alkali concentration. pretreatment of sb with different alkali concentration based on raw material (0%, 2%, 4%, 6% and 8%), time (60, 90 and 120 min) and temperature (80, 100 and 120oc) are shown in table iii. consequences of each independent experiment varying with alkali concentration, temperature and time on the α-cellulose yield were analyzed using matlab software. apparently, it was observed that α-cellulose yield was considerably increased with changes of alkali concentration ranging from 0% to 8% (34.66% to 63.58%). but no noticeable variation was observed in temperature-time alteration during pretreatment of sb. based on cellulose percentage obtained in treated bagasse, the optimum conditions for pretreatment reaction were selected as alkali concentration 8%, time 90 min and temperature 100oc. although cellulose content in treated sb was slowly increased with the increase of alkali concentration 12% attime 90 min and temperature 100oc but as a consequence of huge chemical consumption, recovery problem, chance of losses cellulose and hemicellulose, alkali concentrations for pretreatment above 8% was not considered as ideal concentration. effect of alkali concentration (ac), cooking time and temperature (temp) charge on α-cellulose yield as well as their statistical significance on the basis of f-test number are presented in regression equations (4). as shown in equations, cooking time at the maximum temperature had no significant effect on α-cellulose yield followed by alkali concentration charge. effect of temperature on α-cellulose yield was less in employed cooking conditions. for α-cellulose yield: α-cellulose yield = 82.05-0.151×temp-1.56×time-0.69×ac (r2=0.89, adjusted r2=0.87) ............................................. (4) for pentosan: pentosan = 13.58+0.086 × tem p + 0.006 × time+0.445 × ac (r2=0.67, adjusted r2=0.63) ............................................. (5) for lignin: lignin = 27.662-0.041×temp-0.001×time-01.242×ac (r2=0.93, adjusted r2=0.92) ............................................. (6) for predicting α-cellulose, percentage of pentosan and lignin, the most influential factor was alkali concentration and then cooking temperature for α-cellulose yield, which exhibited an almost linear dependence on both operational variables. the coefficient of determinations is good for α-cellulose yield and lignin percentage which hovers around 90 percent, although the figure is moderate more than 60 percent for pentosan. all these three models are significant (p<0.05) at 5% level of significance. in order to perceive the impact of alkali concentration and temperature on these three parameters, three-dimensional (3d) response surface plots were created by plotting the response (α-cellulose yield) pentosan and lignin on the z-axis versus the most influential one independent variable alkali concentration and temperature as shown in fig. 3 (a), (b) and (c). xrd analysis in 19th century the cellulose crystalline structure has been discovered and later it was verified by x-ray crystallography (meyer and misch, 1937; wilkie, 1961). the crystallinity index (cri) of non-woody biomass, such as grasses and agricultural residues, varies depending on the type of biomass. generally, non-woody biomass has a lower crystallinity index than woody biomass, typically ranging from 20-40%. the crystallinity index of non-woody biomass affects its digestibility and energy production potential.recently, researchers are being paid more attention on cellulose index because of its potential use in bioenergy production. since then several different models of cellulose index have been proposed. the most popular two-phase cellulose model describes cellulose chains as containing both crystalline (ordered) and amorphous (less ordered) region (park et al., 2010). alkali treatment of bagasse has been found to increase the crystallinity index of the bagasse. alkali treatment breaks down hemicellulose, making the cellulose molecules more ordered and crystalline, resulting in a higher crystallinity index. alkali treatment also increases the digestibility of the bagasse, making it easier to break down and therefore more suitable for bioenergy production. x-ray diffraction spectra of the sb and alkali treated sb were presented in figure 4. it was observed that the intensity of 101 and 002 peaks were gradually increased. the relative amount of crystalline cellulose (cri) in the total solid were calculated based on the equation (2) and obtained 18.68%, 24.80%, 27.23%, 32.69%, 36.45% and 39.19% for raw sb, 0%, 2%, 4%, 6% and 8% alkali treated sb samples respectively. the cri of alkali treated sb samples (not cellulose crystallinity) were intensely influenced by the composition of the samples. in case of lignocellulosic biomass examples, cellulose cri measured the relative amount of crystalline cellulose in the total solid. therefore, amorphous part of lignin and hemicellulose in biomass specimens were partially removed with the delignification process as a result the proportion of α-cellulose was increased and hence cri would be increased gradually. this interpretation could be proved by the fact that alkali-treated sb had higher cri than raw sb (zhao et al. 2010) and the portion of cellulose in the treated sb was also increased gradually. according to the equation 3, the average sizes of crystallite obtained were 3.28, 3.51, 3.63, 3.78, 3.90 and 4.06 nm for raw sb, 0%, 2%, 4%, 6% and 8% alkali treated sb samples respectively. the experimental data revealed that during delignification, the size of crystallite was increased. sem analysis sem is one of the most commanding tools widely used to investigate the lignocellulosic biomass surface (amiri and karimi, 2015). sem is usually employed for surface characterization, morphology and inspection of microstructure. in respect of biomass example through sem images we can compare the untreated and pretreated models which may lead to different insight into the biomass (karimi and taherzadeh, 2016). sem provides two-dimensional images of raw sb and alkali treated sb, which were taken and compared to the outcome of naoh treatment. all testers were coated with carbon tape and magnification of 500x was used. figure 4 shows the wall of raw sb (figure 6a) was intact where the alkali treated sb (figures 6c-6f), the cell wall was ruptured or splitted and hence packing of the fibers were partially loosened (firoz et al. 2012). sugar and ethanol yield enzymatic digestibility is the ability of enzymes to break down molecules into smaller molecules, such as glucose. it is used to measure the efficiency of enzyme-catalyzed reactions and the digestibility of cellulose. the enzymatic digestibility of a compound is affected by factors such as the compound's crystallinity index, the type of enzyme used, and the temperature and ph of the reaction. in this study the enzymatic digestibility of the alkali pretreated sb was improved by increasing pretreatment conditions. typically the pretreatment settings are selected by considering various factors such as feedstock characteristics, pretreatment chemical cost, energy consumption and recovery efficiency (wu et al. 2011). α-cellulose obtained by 8% alkali treated of sb was used for hydrolysis reaction and the reaction was carried out at an optimum condition set by sujan et al. (2018). the most effective enzymatic hydrolysis was taken place with trichoderma virideat 48 h and the theoretical yield of sugars i.e. glucose and xylose were obtained 89.59% and 61.23%, respectively. through fermentation process generated sugars were used to check ethanol production. yeast saccharomyces cerevisiae presented worthy performance to convert c6 sugar into ethanol when it was incubated at 30°c for 24 h and 16.81±0.32% ethanol yield was detected. conclusion α-cellulose yield was optimized by varying alkali concentration, temperature and cooking time. the most vital influencing factor for α-cellulose yield was alkali concentration and after that temperature performed a little bit. the optimum α-cellulose yield (63.58±0.05%) was obtained at 8% alkali concentration, 100oc and 90 minutes. in hydrolysis step of sb, trichoderma viridaewas used to convert 8% alkali treated sb into sugars and it was attained 89.59% glucose and 61.23% xylose which gave higher yield in compare with our previous study such as ball milled and mesh size varied sb sample (sujan et al. 2018). at fermentation step saccharomyces cerevisiae was used to convert hydrolysate of 8% alkali treated sb sample and ethanol yield was obtained 16.81±0.32% at 24 h. compositional analysis, imaging and crystallinity are three methods were performed. sem images can give different clues about sb including morphology, surface disruption and creation of highly accessible surface area iii) cri (18.68% to 39.19%) and crystal size (3.28 nm to 4.06 nm) of sb are increased with different alkali treatment (0%-8%). in this case it was observed that crystallinity, crystal size, accessible surface area, porosity, particle size, lignin and hemicellulose content and enzyme adsorption/desorption were acted as the most impressive factors for digestibility of sugarcane bagasse. acknowledgement authors would like to acknowledge pulp and paper division, bcsir for their cooperation. authors also like to thanks for the sincere assistance of md. abdul hamid, junior technician, ifrd, bcsir. references alvira p, tomás-pejó e, ballesteros m and negro mj (2010), pretreatment technologies for an efficient bioethanol production process based on enzymatic hydrolysis: a review, bioresource technology 101(13): 4851-4861. doi: org/10.1016/j.biortech.2009.11.093 agbor vb, cicek n, sparling r, berlin a and levin, db (2011), biomass pretreatment: fundamentals toward application, biotechnology advances 29(6): 675-685. doi: org/10.1016/j.biotechadv.2011.05.005 amiri h and karimi k (2015), improvement of acetone, butanol, and ethanol production from woody biomass using organosolv pretreatment, bioprocess and biosystems engineering 38(10): 1959-1972. astm (2007), standard test members for instrumental determination of c, h, n in petroleum products and lubricants. astm d5291-02, astm international, west conshohocken, pa. canilha l, chandel ak, suzane dos santos milessi t, antunes faf, luiz da costa freitas w, das graças almeida felipe m and da silva ss (2012), bioconversion of sugarcane biomass into ethanol: an overview about composition, pretreatment methods, detoxification of hydrolysates, enzymatic saccharification and ethanol fermentation. journal of biomedicine and biotechnology, doi: org/10.1155/2012/989572 den w, sharma vk, lee m, nadadur g and varma rs (2018), lignocellulosic biomass transformations via greener oxidative pretreatment processes: access to energy and value-added chemicals, frontiers in chemistry 6: 141. doi: org/10.3389/fchem.2018.00141 ahmed fm, rahman sr and gomes dj (2012), saccharification of sugarcane bagasse by enzymatic treatment for bioethanol production, malays j microbiol 8(2), 97-103. hirani ah, javed n, asif m, basu sk and kumar a (2018), a review on first-and second-generation biofuel productions. in biofuels: greenhouse gas mitigation and global warming, springer, new delhi, pp 141-154. doi: 10.1007/978-81-322-3763-1_8 islam mz, asad ma, hossain mt, paul sc and sujan sma (2019), bioethanol production from banana pseudostem by using separate and cocultures of cellulase enzyme with saccharomyces cerevisiae, journal of environmental science and technology 12(4): 157-163. jahan ms, saeed a, ni y and he z (2009), pre-extraction and its impact on the alkaline pulping of bagasse, journal of biobased materials and bioenergy 3(4): 380-385. doi: org/10.1166/jbmb.2009.1053 janker-obermeier i, sieber v, faulstich mand schieder d (2012), solubilization of hemicellulose and lignin from wheat straw through microwave-assisted alkali treatment, industrial crops and products 39: 198-203. doi: org/10.1016/j.indcrop.2012.02.022 karimi k and taherzadeh mj (2016), a critical review of analytical methods in pretreatment of lignocelluloses: composition, imaging, and crystallinity, bioresource technology 200: 1008-1018. doi: org/10.1016/j. biortech.2015.11.022 maryana r, ma’rifatun d, wheni ai, satriyo kw and rizal wa (2014), alkaline pretreatment on sugarcane bagasse for bioethanol production, energy procedia, 47: 250-254. doi: org/10.1016/j.egypro.2014.01.221 mcintosh sand vancov t (2010), enhanced enzyme saccharification of sorghum bicolor straw using dilute alkali pretreatment, bioresource technology 101(17): 6718-6727. doi: org/10.1016/j.biortech.2010.03.116 meyer kh and misch l (1937), positions des atomes dans le nouveau modele spatial de la cellulose. helvetica chimica acta 20(1): 232-244. doi: org/10. 1002/hlca.19370200134 park s, baker jo, himmel me, parilla pa and johnson dk (2010), cellulose crystallinity index: measurement techniques and their impact on interpreting cellulase performance, biotechnology for biofuels 3(1): 10. sujan sma, bari ml and fakhruddin an (2018), effects of physical pretreatment (crushing and ball milling) on sugarcane bagasse for bioethanol production, bangladesh journal of botany 147(2): 257-64. wilkie js (1961), carl nägeli and the fine structure of living matter, nature 190: 1145-1150. wu l, arakane m, ike m, wada m, takai t, gau mand tokuyasu k (2011), low temperature alkali pretreatment for improving enzymatic digestibility of sweet sorghum bagasse for ethanol production, bioresource technology 102(7): 4793-4799. zhang w, okubayashi s and bechtold t (2005), fibrillation tendency of cellulosic fibers-part 4. effects of alkali pretreatment of various cellulosic fibers, carbohydrate polymers. 61(4): 427-433. zhao x, van der heide e, zhang tand liu d (2010), delignification of sugarcane bagasse with alkali and peracetic acid and characterization of the pulp, bioresources 5(3): 1565-1580. zhao x, zhang land liu d (2012), biomass recalcitrance. part ii: fundamentals of different pre‐treatments to increase the enzymatic digestibility of lignocellulose, biofuels, bioproducts and biorefining 6(5): 561-579. fig. 2. a) 20-40 mesh size sb and alkali were taking into plastic zipper bag; b) samples were pretreated into water bath at a temperature below 100oc; c) 20-40 mesh size sb and alkali were taking into stainless-steel reactor; d) sample pretreated into oil bath at a temperature above 100oc 2a 2b 2c 2d optimization of alkali concentration in the pretreatment of sugarcane bagasse 58(2) 202392 composed of vasculer bundles surrounded by non-fibrous parenchymatic cell (jahan et al. 2009). usually it is available as agricultural residue and byproduct from sugar mill industries. in the year of 2015-16, there was 2,95,162 metric ton sugarcane bagasse was obtained from sugar mills of bangladesh (http://www.bsfic.gov.bd). to enrich cellulose content in biomass for enzymatic saccarification, current research has focused on various pretreatment processes. currently, scientists have gone through a lot of studies on different pretreatment techniques to remove the compact and rigid composition by open up the cellulosic structure (alvira et al. 2010). pretreatment technologies are commonly abandoned to reduce the structural barriers and boost cellulose availability based on not only chemicals such as acid, alkali, oxidant, etc. but also several treatment settings. alkali treatment is one of the most widespread and economical methods used for surface modification of lignocellulosic biomass. in the field of biorefinary, alkali pretreatment is intensively employed to develop the cellulosic materials both mechanically as well as chemically and such properties include tensile strength, dyeability, stability of dimension and reactivity (wu et al. 2011). in alkali pretreatment biomass is treated under moderate reaction conditions ensuring inexpensiveness, inflated recycling possibilities of water and chemical agents (mcintosh and vancov, 2010). usually alkali treatment is the most effective pretreatment for agricultural residues, herbaceous crops and hardwood containing low lignin content in the compariosn of softwood containing high lignin content (agbor et al. 2011; canilha et al. 2012). this research aims is to investigate the alkaline pretreatment repercussions based on the chemical structure, surface morphology, structure and enzymatic digestion of sugarcane bagasse for sugars and ethanol production. materials and methods sugarcane bagasse (sb) was taken from street juice vendor. warm tap water was used for washing purpose to eliminate the residual free sugars once again. this washing and pressing step was then repeated for three times. after that drying was done in an oven at 65oc for 16 h. crushing of dried bagasse was done successively using a locally made crusher and sieved (retsch, d-42759, haan, germany) to have the particle size of 20-40 mesh on average. before usage, the 20-40 mesh bagasse was kept at room temperature in an airtight plastic container (sujan et al. 2018). moisture and ash content moisture content of raw materials was measured using the astm d 4442-07 procedure. in a glass crucible, 2 grams of pretreatment sample containing 20-40 mesh were dried in oven at 105±2°c. the moisture content was expressed in percent wet basis and weight measurements were taken every 3 h. a muffle furnace was used for burning the oven-dried samples at 575±25°c for ash content determination following the astm standard e 1755-01. volatile matter the volatile matter analysis was carried out in accordance with astm standard d 271-48. four grams of raw materials were heated in a furnace at 950±20°c for seven minutes. the weight loss, excluding the weight of moisture pushed off at 105°c, is then used to calculate volatile matter. fixed carbon the difference between 100 and the total of volatile matter, moisture, and ash content was used to compute the fixed carbon percentage. chemical analysis the technical association of the pulp and paper industry (tappi) method detects α-cellulose (t 203 cm-99), pentosan (t 223 cm-01), klason lignin (t211 om-83), and acid soluble lignin (t um 250) on a dry basis. ultimate analysis ultimate analysis of samples was done by following the procedure astm standard d 5291-02. organic elemental analyzer (flash 2000, thermo scientific, usa) was used with a specific condition (reactor temp. 900°c, he: 250 kpa, o2: 250 kpa, tcd). low concentration alkali pretreatment different alkali concentration (0%, 2%, 4%, 6% and 8%), time (60, 90 and 120 min) and temperature (80, 100 and 120oc) were applied on raw material to check alkali effect on sb shown in table 3. a portion of the ground bagasse 20-40 mesh (10g) was taken into plastic zipper bag (temperature 80oc, figure 2a and 2b) and stainless-steel reactor (temperature 100oc and 120oc, figure 2c and 2d). different alkali concentration was applied during the pretreatment process (alkali to sb ratio ranging between 1:12). the mixture was heated at a particular temperature such as in a water bath (80oc) and oil bath (100oc and 120oc) for a desired length of time. in the course of pretreatment process the sample was manually mixed 2-3 times to attain proper alkali treatment. the treated sb was placed into a polyester bag to remove excess alkali water by pressing it. after that it was vigorously washed with tap water (repeated for five times) to remove the remaining alkali. finally the sb was dried in an oven at 65oc for 72 h and stored in a close container at room temperature for further experiment. regression model regression model has been developed for prediction of α-cellulose, pentosan and lignin in sb. the general form of the model is: y=α+α1x1 + α2x2+........................+αnxn + ε.......................(1) where α is the constant term. αi are the coefficient of variables xi. ε is the random error term which is minimized with simple least squares regression (slsr). regression coefficients of the independent variables namely alkali concentration, temperature and time are estimated by slsr method for developing regression model to predict α-cellulose, pentosan and lignin. efficiencies of these models are expressed by coefficient of multiple determination (r2) and adjusted r2. 2.9 separate hydrolysis and fermentation (shf) the hydrolysis experiment took place in 100 ml conical flux 10ml enzyme solution with 200 mg (2% dry wt.) in citrate buffer (0.05 m, ph 5.0) at 50°c for 48 h. in this case trichoderma viride was used for hydrolysis. hydrolysate was then heated for 15 min in a boiling water bath and centrifugation was done to remove solid particles. the supernatant was used for analysis of released sugars as described by jamal et al. (2011). during fermentation process according to firoz et al. (2012), 100 ml media was prepared and 0.5 g of commercial yeast saccharomyces cerevisiae was used as inoculum which showed good performance to converts sugar into bioethanol. this inoculated media mixture was poured in a suitable glassware and was kept in a shaking incubator for 48 h. 10 ml of this medium was then added into the flask and it was properly covered with aluminum foil. then it was placed in the incubator at 30oc for 24 h, 48 h, 72 h and 96 h for fermentation of sugars to bio-ethanol according to sujan et al. (2018). samples from hydrolysis and fermentation were performed by hplc. high performance liquid chromatography (hplc) in characterize part, concentration of sugars and ethanol were determined by hplc (ultimate 3000, thermo scientific, usa) method using hyper rez xp carbohydrate h+ 8 µm column (100×7.7 mm) equipped with a refractive index (shodex ri-101) detector. the mobile phase was degassed with deionized water with a flow rate of 0.7 ml/min and column temperature was maintained at 70°c. it is possible to measure the total sugar concentration in the hydrolysis liquid fraction by comparing its peak area detected by hplc with peak area of 1% standard sugar which consists of two sugars namely glucose and xylose (sujan et al. 2018). the same column which is specialized for fermentation broth analysis is used for ethanol detection. the kinetic parameters of ethanol fermentation were determined as follows (islam et al. 2019): crystallinity measurement x-ray diffraction (xrd) was used to determine the crystalline structure of the sb samples using a diffractometer (gbc xrd) and filtered copper k radiation (λ = 0.1542 nm) by a monochromator at 35.50 kv voltage and 28 ma current, with a speed of about 2o/min and scanning in the range of 10 80ºc. the crystallinity index (cri) was obtained from the ratio between the intensity of the 002 peak (i002, 2θ = 22.5) and the minimum dip (iam, 2 θ = 18.5) according to the following equation (roberta et al., 2012): cri (%) = [(i002 iam)/i002] ×100 ...................................... (2) where i002 is the highest peak intensity of plane 002 and iam is related to the amorphous structure. in present study, the average crystallite sizes were determined from the scherrer equation by using the diffraction pattern obtained from the 002 (hkl) lattice planes of cellulose samples d(hkl) = [(kλ / b(hkl) cos2θ] ............................................... (3) where d(hkl) (crystallite size), k (scherrer constant, 0.84), λ (x-ray wavelength, 0.154nm), b(hkl)(full width half maximum of the measured hkl reflection), and 2θ (corresponding bragg angle). scanning electron microscopy (sem) analysis in this research, sem (zeiss evo 18 sem) was used to detect the change of pretreated bagasse fibers. sem images were taken of different pretreated bagasse samples with acceleration voltage of 2.0 kv. results and discussion proximate analysis proximate analysis of sb sample (20-40 mesh) are presented in table i. primarily this analysis usually evaluate the fuel characteristics of raw materials. according to sun et al., 2009, higher moisture and ashcontent in samples lessen the heating value. ultimate analysis ultimate analysis denotes the elemental configuration of sb such as carbon, hydrogen, oxygen, nitrogen and sulfur which are shown in table ii. this examination helps to measure the percentage of carbon and hydrogen content in biomass that is responsible to determine the amount of air is required for complete combustion, composition of combustion gases and heat is generated by it (poddar et al. 2014). chemical properties raw sb contained 34.66±12% α-cellulose, 22.43±08% pentosan and 19.57±06% klason lignin in which 1.75±04% acid soluble lignin (dry basis) was detected by technical association of the pulp and paper industry (tappi) method. the chemical composition of sb was determined by acid hydrolysis and it was calculatedby hplc method as 45.35% glucose and 30.64% xylose (sujan et al., 2018). α-cellulose yield bagasse is mainly composed of cellulose, hemicellulose and lignin. besides these there are some extractives such as ash, wax, gum, pectin etc. during alkali pretreatment usually most of the extractives are removed with the increasing of alkali concentration. pretreatment of sb with different alkali concentration based on raw material (0%, 2%, 4%, 6% and 8%), time (60, 90 and 120 min) and temperature (80, 100 and 120oc) are shown in table iii. consequences of each independent experiment varying with alkali concentration, temperature and time on the α-cellulose yield were analyzed using matlab software. apparently, it was observed that α-cellulose yield was considerably increased with changes of alkali concentration ranging from 0% to 8% (34.66% to 63.58%). but no noticeable variation was observed in temperature-time alteration during pretreatment of sb. based on cellulose percentage obtained in treated bagasse, the optimum conditions for pretreatment reaction were selected as alkali concentration 8%, time 90 min and temperature 100oc. although cellulose content in treated sb was slowly increased with the increase of alkali concentration 12% attime 90 min and temperature 100oc but as a consequence of huge chemical consumption, recovery problem, chance of losses cellulose and hemicellulose, alkali concentrations for pretreatment above 8% was not considered as ideal concentration. effect of alkali concentration (ac), cooking time and temperature (temp) charge on α-cellulose yield as well as their statistical significance on the basis of f-test number are presented in regression equations (4). as shown in equations, cooking time at the maximum temperature had no significant effect on α-cellulose yield followed by alkali concentration charge. effect of temperature on α-cellulose yield was less in employed cooking conditions. for α-cellulose yield: α-cellulose yield = 82.05-0.151×temp-1.56×time-0.69×ac (r2=0.89, adjusted r2=0.87) ............................................. (4) for pentosan: pentosan = 13.58+0.086 × tem p + 0.006 × time+0.445 × ac (r2=0.67, adjusted r2=0.63) ............................................. (5) for lignin: lignin = 27.662-0.041×temp-0.001×time-01.242×ac (r2=0.93, adjusted r2=0.92) ............................................. (6) for predicting α-cellulose, percentage of pentosan and lignin, the most influential factor was alkali concentration and then cooking temperature for α-cellulose yield, which exhibited an almost linear dependence on both operational variables. the coefficient of determinations is good for α-cellulose yield and lignin percentage which hovers around 90 percent, although the figure is moderate more than 60 percent for pentosan. all these three models are significant (p<0.05) at 5% level of significance. in order to perceive the impact of alkali concentration and temperature on these three parameters, three-dimensional (3d) response surface plots were created by plotting the response (α-cellulose yield) pentosan and lignin on the z-axis versus the most influential one independent variable alkali concentration and temperature as shown in fig. 3 (a), (b) and (c). xrd analysis in 19th century the cellulose crystalline structure has been discovered and later it was verified by x-ray crystallography (meyer and misch, 1937; wilkie, 1961). the crystallinity index (cri) of non-woody biomass, such as grasses and agricultural residues, varies depending on the type of biomass. generally, non-woody biomass has a lower crystallinity index than woody biomass, typically ranging from 20-40%. the crystallinity index of non-woody biomass affects its digestibility and energy production potential.recently, researchers are being paid more attention on cellulose index because of its potential use in bioenergy production. since then several different models of cellulose index have been proposed. the most popular two-phase cellulose model describes cellulose chains as containing both crystalline (ordered) and amorphous (less ordered) region (park et al., 2010). alkali treatment of bagasse has been found to increase the crystallinity index of the bagasse. alkali treatment breaks down hemicellulose, making the cellulose molecules more ordered and crystalline, resulting in a higher crystallinity index. alkali treatment also increases the digestibility of the bagasse, making it easier to break down and therefore more suitable for bioenergy production. x-ray diffraction spectra of the sb and alkali treated sb were presented in figure 4. it was observed that the intensity of 101 and 002 peaks were gradually increased. the relative amount of crystalline cellulose (cri) in the total solid were calculated based on the equation (2) and obtained 18.68%, 24.80%, 27.23%, 32.69%, 36.45% and 39.19% for raw sb, 0%, 2%, 4%, 6% and 8% alkali treated sb samples respectively. the cri of alkali treated sb samples (not cellulose crystallinity) were intensely influenced by the composition of the samples. in case of lignocellulosic biomass examples, cellulose cri measured the relative amount of crystalline cellulose in the total solid. therefore, amorphous part of lignin and hemicellulose in biomass specimens were partially removed with the delignification process as a result the proportion of α-cellulose was increased and hence cri would be increased gradually. this interpretation could be proved by the fact that alkali-treated sb had higher cri than raw sb (zhao et al. 2010) and the portion of cellulose in the treated sb was also increased gradually. according to the equation 3, the average sizes of crystallite obtained were 3.28, 3.51, 3.63, 3.78, 3.90 and 4.06 nm for raw sb, 0%, 2%, 4%, 6% and 8% alkali treated sb samples respectively. the experimental data revealed that during delignification, the size of crystallite was increased. sem analysis sem is one of the most commanding tools widely used to investigate the lignocellulosic biomass surface (amiri and karimi, 2015). sem is usually employed for surface characterization, morphology and inspection of microstructure. in respect of biomass example through sem images we can compare the untreated and pretreated models which may lead to different insight into the biomass (karimi and taherzadeh, 2016). sem provides two-dimensional images of raw sb and alkali treated sb, which were taken and compared to the outcome of naoh treatment. all testers were coated with carbon tape and magnification of 500x was used. figure 4 shows the wall of raw sb (figure 6a) was intact where the alkali treated sb (figures 6c-6f), the cell wall was ruptured or splitted and hence packing of the fibers were partially loosened (firoz et al. 2012). sugar and ethanol yield enzymatic digestibility is the ability of enzymes to break down molecules into smaller molecules, such as glucose. it is used to measure the efficiency of enzyme-catalyzed reactions and the digestibility of cellulose. the enzymatic digestibility of a compound is affected by factors such as the compound's crystallinity index, the type of enzyme used, and the temperature and ph of the reaction. in this study the enzymatic digestibility of the alkali pretreated sb was improved by increasing pretreatment conditions. typically the pretreatment settings are selected by considering various factors such as feedstock characteristics, pretreatment chemical cost, energy consumption and recovery efficiency (wu et al. 2011). α-cellulose obtained by 8% alkali treated of sb was used for hydrolysis reaction and the reaction was carried out at an optimum condition set by sujan et al. (2018). the most effective enzymatic hydrolysis was taken place with trichoderma virideat 48 h and the theoretical yield of sugars i.e. glucose and xylose were obtained 89.59% and 61.23%, respectively. through fermentation process generated sugars were used to check ethanol production. yeast saccharomyces cerevisiae presented worthy performance to convert c6 sugar into ethanol when it was incubated at 30°c for 24 h and 16.81±0.32% ethanol yield was detected. conclusion α-cellulose yield was optimized by varying alkali concentration, temperature and cooking time. the most vital influencing factor for α-cellulose yield was alkali concentration and after that temperature performed a little bit. the optimum α-cellulose yield (63.58±0.05%) was obtained at 8% alkali concentration, 100oc and 90 minutes. in hydrolysis step of sb, trichoderma viridaewas used to convert 8% alkali treated sb into sugars and it was attained 89.59% glucose and 61.23% xylose which gave higher yield in compare with our previous study such as ball milled and mesh size varied sb sample (sujan et al. 2018). at fermentation step saccharomyces cerevisiae was used to convert hydrolysate of 8% alkali treated sb sample and ethanol yield was obtained 16.81±0.32% at 24 h. compositional analysis, imaging and crystallinity are three methods were performed. sem images can give different clues about sb including morphology, surface disruption and creation of highly accessible surface area iii) cri (18.68% to 39.19%) and crystal size (3.28 nm to 4.06 nm) of sb are increased with different alkali treatment (0%-8%). in this case it was observed that crystallinity, crystal size, accessible surface area, porosity, particle size, lignin and hemicellulose content and enzyme adsorption/desorption were acted as the most impressive factors for digestibility of sugarcane bagasse. acknowledgement authors would like to acknowledge pulp and paper division, bcsir for their cooperation. authors also like to thanks for the sincere assistance of md. abdul hamid, junior technician, ifrd, bcsir. references alvira p, tomás-pejó e, ballesteros m and negro mj (2010), pretreatment technologies for an efficient bioethanol production process based on enzymatic hydrolysis: a review, bioresource technology 101(13): 4851-4861. doi: org/10.1016/j.biortech.2009.11.093 agbor vb, cicek n, sparling r, berlin a and levin, db (2011), biomass pretreatment: fundamentals toward application, biotechnology advances 29(6): 675-685. doi: org/10.1016/j.biotechadv.2011.05.005 amiri h and karimi k (2015), improvement of acetone, butanol, and ethanol production from woody biomass using organosolv pretreatment, bioprocess and biosystems engineering 38(10): 1959-1972. astm (2007), standard test members for instrumental determination of c, h, n in petroleum products and lubricants. astm d5291-02, astm international, west conshohocken, pa. canilha l, chandel ak, suzane dos santos milessi t, antunes faf, luiz da costa freitas w, das graças almeida felipe m and da silva ss (2012), bioconversion of sugarcane biomass into ethanol: an overview about composition, pretreatment methods, detoxification of hydrolysates, enzymatic saccharification and ethanol fermentation. journal of biomedicine and biotechnology, doi: org/10.1155/2012/989572 den w, sharma vk, lee m, nadadur g and varma rs (2018), lignocellulosic biomass transformations via greener oxidative pretreatment processes: access to energy and value-added chemicals, frontiers in chemistry 6: 141. doi: org/10.3389/fchem.2018.00141 ahmed fm, rahman sr and gomes dj (2012), saccharification of sugarcane bagasse by enzymatic treatment for bioethanol production, malays j microbiol 8(2), 97-103. hirani ah, javed n, asif m, basu sk and kumar a (2018), a review on first-and second-generation biofuel productions. in biofuels: greenhouse gas mitigation and global warming, springer, new delhi, pp 141-154. doi: 10.1007/978-81-322-3763-1_8 islam mz, asad ma, hossain mt, paul sc and sujan sma (2019), bioethanol production from banana pseudostem by using separate and cocultures of cellulase enzyme with saccharomyces cerevisiae, journal of environmental science and technology 12(4): 157-163. jahan ms, saeed a, ni y and he z (2009), pre-extraction and its impact on the alkaline pulping of bagasse, journal of biobased materials and bioenergy 3(4): 380-385. doi: org/10.1166/jbmb.2009.1053 janker-obermeier i, sieber v, faulstich mand schieder d (2012), solubilization of hemicellulose and lignin from wheat straw through microwave-assisted alkali treatment, industrial crops and products 39: 198-203. doi: org/10.1016/j.indcrop.2012.02.022 karimi k and taherzadeh mj (2016), a critical review of analytical methods in pretreatment of lignocelluloses: composition, imaging, and crystallinity, bioresource technology 200: 1008-1018. doi: org/10.1016/j. biortech.2015.11.022 maryana r, ma’rifatun d, wheni ai, satriyo kw and rizal wa (2014), alkaline pretreatment on sugarcane bagasse for bioethanol production, energy procedia, 47: 250-254. doi: org/10.1016/j.egypro.2014.01.221 mcintosh sand vancov t (2010), enhanced enzyme saccharification of sorghum bicolor straw using dilute alkali pretreatment, bioresource technology 101(17): 6718-6727. doi: org/10.1016/j.biortech.2010.03.116 meyer kh and misch l (1937), positions des atomes dans le nouveau modele spatial de la cellulose. helvetica chimica acta 20(1): 232-244. doi: org/10. 1002/hlca.19370200134 park s, baker jo, himmel me, parilla pa and johnson dk (2010), cellulose crystallinity index: measurement techniques and their impact on interpreting cellulase performance, biotechnology for biofuels 3(1): 10. sujan sma, bari ml and fakhruddin an (2018), effects of physical pretreatment (crushing and ball milling) on sugarcane bagasse for bioethanol production, bangladesh journal of botany 147(2): 257-64. wilkie js (1961), carl nägeli and the fine structure of living matter, nature 190: 1145-1150. wu l, arakane m, ike m, wada m, takai t, gau mand tokuyasu k (2011), low temperature alkali pretreatment for improving enzymatic digestibility of sweet sorghum bagasse for ethanol production, bioresource technology 102(7): 4793-4799. zhang w, okubayashi s and bechtold t (2005), fibrillation tendency of cellulosic fibers-part 4. effects of alkali pretreatment of various cellulosic fibers, carbohydrate polymers. 61(4): 427-433. zhao x, van der heide e, zhang tand liu d (2010), delignification of sugarcane bagasse with alkali and peracetic acid and characterization of the pulp, bioresources 5(3): 1565-1580. zhao x, zhang land liu d (2012), biomass recalcitrance. part ii: fundamentals of different pre‐treatments to increase the enzymatic digestibility of lignocellulose, biofuels, bioproducts and biorefining 6(5): 561-579. ethanol concentration (ec)% = volume of reaction mixture (l) ethanol produced (g) table i. proximate analysis of sugarcane bagasse sample name of sample moisture (%) ash (%) volatile matter (%) fixed carbon (%) sb 9.44±0.14 1.75±0.06 4.99±0.11 83.82±0.17 sujan, hossain, uddin and fakhruddin 93 composed of vasculer bundles surrounded by non-fibrous parenchymatic cell (jahan et al. 2009). usually it is available as agricultural residue and byproduct from sugar mill industries. in the year of 2015-16, there was 2,95,162 metric ton sugarcane bagasse was obtained from sugar mills of bangladesh (http://www.bsfic.gov.bd). to enrich cellulose content in biomass for enzymatic saccarification, current research has focused on various pretreatment processes. currently, scientists have gone through a lot of studies on different pretreatment techniques to remove the compact and rigid composition by open up the cellulosic structure (alvira et al. 2010). pretreatment technologies are commonly abandoned to reduce the structural barriers and boost cellulose availability based on not only chemicals such as acid, alkali, oxidant, etc. but also several treatment settings. alkali treatment is one of the most widespread and economical methods used for surface modification of lignocellulosic biomass. in the field of biorefinary, alkali pretreatment is intensively employed to develop the cellulosic materials both mechanically as well as chemically and such properties include tensile strength, dyeability, stability of dimension and reactivity (wu et al. 2011). in alkali pretreatment biomass is treated under moderate reaction conditions ensuring inexpensiveness, inflated recycling possibilities of water and chemical agents (mcintosh and vancov, 2010). usually alkali treatment is the most effective pretreatment for agricultural residues, herbaceous crops and hardwood containing low lignin content in the compariosn of softwood containing high lignin content (agbor et al. 2011; canilha et al. 2012). this research aims is to investigate the alkaline pretreatment repercussions based on the chemical structure, surface morphology, structure and enzymatic digestion of sugarcane bagasse for sugars and ethanol production. materials and methods sugarcane bagasse (sb) was taken from street juice vendor. warm tap water was used for washing purpose to eliminate the residual free sugars once again. this washing and pressing step was then repeated for three times. after that drying was done in an oven at 65oc for 16 h. crushing of dried bagasse was done successively using a locally made crusher and sieved (retsch, d-42759, haan, germany) to have the particle size of 20-40 mesh on average. before usage, the 20-40 mesh bagasse was kept at room temperature in an airtight plastic container (sujan et al. 2018). moisture and ash content moisture content of raw materials was measured using the astm d 4442-07 procedure. in a glass crucible, 2 grams of pretreatment sample containing 20-40 mesh were dried in oven at 105±2°c. the moisture content was expressed in percent wet basis and weight measurements were taken every 3 h. a muffle furnace was used for burning the oven-dried samples at 575±25°c for ash content determination following the astm standard e 1755-01. volatile matter the volatile matter analysis was carried out in accordance with astm standard d 271-48. four grams of raw materials were heated in a furnace at 950±20°c for seven minutes. the weight loss, excluding the weight of moisture pushed off at 105°c, is then used to calculate volatile matter. fixed carbon the difference between 100 and the total of volatile matter, moisture, and ash content was used to compute the fixed carbon percentage. chemical analysis the technical association of the pulp and paper industry (tappi) method detects α-cellulose (t 203 cm-99), pentosan (t 223 cm-01), klason lignin (t211 om-83), and acid soluble lignin (t um 250) on a dry basis. ultimate analysis ultimate analysis of samples was done by following the procedure astm standard d 5291-02. organic elemental analyzer (flash 2000, thermo scientific, usa) was used with a specific condition (reactor temp. 900°c, he: 250 kpa, o2: 250 kpa, tcd). low concentration alkali pretreatment different alkali concentration (0%, 2%, 4%, 6% and 8%), time (60, 90 and 120 min) and temperature (80, 100 and 120oc) were applied on raw material to check alkali effect on sb shown in table 3. a portion of the ground bagasse 20-40 mesh (10g) was taken into plastic zipper bag (temperature 80oc, figure 2a and 2b) and stainless-steel reactor (temperature 100oc and 120oc, figure 2c and 2d). different alkali concentration was applied during the pretreatment process (alkali to sb ratio ranging between 1:12). the mixture was heated at a particular temperature such as in a water bath (80oc) and oil bath (100oc and 120oc) for a desired length of time. in the course of pretreatment process the sample was manually mixed 2-3 times to attain proper alkali treatment. the treated sb was placed into a polyester bag to remove excess alkali water by pressing it. after that it was vigorously washed with tap water (repeated for five times) to remove the remaining alkali. finally the sb was dried in an oven at 65oc for 72 h and stored in a close container at room temperature for further experiment. regression model regression model has been developed for prediction of α-cellulose, pentosan and lignin in sb. the general form of the model is: y=α+α1x1 + α2x2+........................+αnxn + ε.......................(1) where α is the constant term. αi are the coefficient of variables xi. ε is the random error term which is minimized with simple least squares regression (slsr). regression coefficients of the independent variables namely alkali concentration, temperature and time are estimated by slsr method for developing regression model to predict α-cellulose, pentosan and lignin. efficiencies of these models are expressed by coefficient of multiple determination (r2) and adjusted r2. 2.9 separate hydrolysis and fermentation (shf) the hydrolysis experiment took place in 100 ml conical flux 10ml enzyme solution with 200 mg (2% dry wt.) in citrate buffer (0.05 m, ph 5.0) at 50°c for 48 h. in this case trichoderma viride was used for hydrolysis. hydrolysate was then heated for 15 min in a boiling water bath and centrifugation was done to remove solid particles. the supernatant was used for analysis of released sugars as described by jamal et al. (2011). during fermentation process according to firoz et al. (2012), 100 ml media was prepared and 0.5 g of commercial yeast saccharomyces cerevisiae was used as inoculum which showed good performance to converts sugar into bioethanol. this inoculated media mixture was poured in a suitable glassware and was kept in a shaking incubator for 48 h. 10 ml of this medium was then added into the flask and it was properly covered with aluminum foil. then it was placed in the incubator at 30oc for 24 h, 48 h, 72 h and 96 h for fermentation of sugars to bio-ethanol according to sujan et al. (2018). samples from hydrolysis and fermentation were performed by hplc. high performance liquid chromatography (hplc) in characterize part, concentration of sugars and ethanol were determined by hplc (ultimate 3000, thermo scientific, usa) method using hyper rez xp carbohydrate h+ 8 µm column (100×7.7 mm) equipped with a refractive index (shodex ri-101) detector. the mobile phase was degassed with deionized water with a flow rate of 0.7 ml/min and column temperature was maintained at 70°c. it is possible to measure the total sugar concentration in the hydrolysis liquid fraction by comparing its peak area detected by hplc with peak area of 1% standard sugar which consists of two sugars namely glucose and xylose (sujan et al. 2018). the same column which is specialized for fermentation broth analysis is used for ethanol detection. the kinetic parameters of ethanol fermentation were determined as follows (islam et al. 2019): crystallinity measurement x-ray diffraction (xrd) was used to determine the crystalline structure of the sb samples using a diffractometer (gbc xrd) and filtered copper k radiation (λ = 0.1542 nm) by a monochromator at 35.50 kv voltage and 28 ma current, with a speed of about 2o/min and scanning in the range of 10 80ºc. the crystallinity index (cri) was obtained from the ratio between the intensity of the 002 peak (i002, 2θ = 22.5) and the minimum dip (iam, 2 θ = 18.5) according to the following equation (roberta et al., 2012): cri (%) = [(i002 iam)/i002] ×100 ...................................... (2) where i002 is the highest peak intensity of plane 002 and iam is related to the amorphous structure. in present study, the average crystallite sizes were determined from the scherrer equation by using the diffraction pattern obtained from the 002 (hkl) lattice planes of cellulose samples d(hkl) = [(kλ / b(hkl) cos2θ] ............................................... (3) where d(hkl) (crystallite size), k (scherrer constant, 0.84), λ (x-ray wavelength, 0.154nm), b(hkl)(full width half maximum of the measured hkl reflection), and 2θ (corresponding bragg angle). scanning electron microscopy (sem) analysis in this research, sem (zeiss evo 18 sem) was used to detect the change of pretreated bagasse fibers. sem images were taken of different pretreated bagasse samples with acceleration voltage of 2.0 kv. results and discussion proximate analysis proximate analysis of sb sample (20-40 mesh) are presented in table i. primarily this analysis usually evaluate the fuel characteristics of raw materials. according to sun et al., 2009, higher moisture and ashcontent in samples lessen the heating value. ultimate analysis ultimate analysis denotes the elemental configuration of sb such as carbon, hydrogen, oxygen, nitrogen and sulfur which are shown in table ii. this examination helps to measure the percentage of carbon and hydrogen content in biomass that is responsible to determine the amount of air is required for complete combustion, composition of combustion gases and heat is generated by it (poddar et al. 2014). chemical properties raw sb contained 34.66±12% α-cellulose, 22.43±08% pentosan and 19.57±06% klason lignin in which 1.75±04% acid soluble lignin (dry basis) was detected by technical association of the pulp and paper industry (tappi) method. the chemical composition of sb was determined by acid hydrolysis and it was calculatedby hplc method as 45.35% glucose and 30.64% xylose (sujan et al., 2018). α-cellulose yield bagasse is mainly composed of cellulose, hemicellulose and lignin. besides these there are some extractives such as ash, wax, gum, pectin etc. during alkali pretreatment usually most of the extractives are removed with the increasing of alkali concentration. pretreatment of sb with different alkali concentration based on raw material (0%, 2%, 4%, 6% and 8%), time (60, 90 and 120 min) and temperature (80, 100 and 120oc) are shown in table iii. consequences of each independent experiment varying with alkali concentration, temperature and time on the α-cellulose yield were analyzed using matlab software. apparently, it was observed that α-cellulose yield was considerably increased with changes of alkali concentration ranging from 0% to 8% (34.66% to 63.58%). but no noticeable variation was observed in temperature-time alteration during pretreatment of sb. based on cellulose percentage obtained in treated bagasse, the optimum conditions for pretreatment reaction were selected as alkali concentration 8%, time 90 min and temperature 100oc. although cellulose content in treated sb was slowly increased with the increase of alkali concentration 12% attime 90 min and temperature 100oc but as a consequence of huge chemical consumption, recovery problem, chance of losses cellulose and hemicellulose, alkali concentrations for pretreatment above 8% was not considered as ideal concentration. effect of alkali concentration (ac), cooking time and temperature (temp) charge on α-cellulose yield as well as their statistical significance on the basis of f-test number are presented in regression equations (4). as shown in equations, cooking time at the maximum temperature had no significant effect on α-cellulose yield followed by alkali concentration charge. effect of temperature on α-cellulose yield was less in employed cooking conditions. for α-cellulose yield: α-cellulose yield = 82.05-0.151×temp-1.56×time-0.69×ac (r2=0.89, adjusted r2=0.87) ............................................. (4) for pentosan: pentosan = 13.58+0.086 × tem p + 0.006 × time+0.445 × ac (r2=0.67, adjusted r2=0.63) ............................................. (5) for lignin: lignin = 27.662-0.041×temp-0.001×time-01.242×ac (r2=0.93, adjusted r2=0.92) ............................................. (6) for predicting α-cellulose, percentage of pentosan and lignin, the most influential factor was alkali concentration and then cooking temperature for α-cellulose yield, which exhibited an almost linear dependence on both operational variables. the coefficient of determinations is good for α-cellulose yield and lignin percentage which hovers around 90 percent, although the figure is moderate more than 60 percent for pentosan. all these three models are significant (p<0.05) at 5% level of significance. in order to perceive the impact of alkali concentration and temperature on these three parameters, three-dimensional (3d) response surface plots were created by plotting the response (α-cellulose yield) pentosan and lignin on the z-axis versus the most influential one independent variable alkali concentration and temperature as shown in fig. 3 (a), (b) and (c). xrd analysis in 19th century the cellulose crystalline structure has been discovered and later it was verified by x-ray crystallography (meyer and misch, 1937; wilkie, 1961). the crystallinity index (cri) of non-woody biomass, such as grasses and agricultural residues, varies depending on the type of biomass. generally, non-woody biomass has a lower crystallinity index than woody biomass, typically ranging from 20-40%. the crystallinity index of non-woody biomass affects its digestibility and energy production potential.recently, researchers are being paid more attention on cellulose index because of its potential use in bioenergy production. since then several different models of cellulose index have been proposed. the most popular two-phase cellulose model describes cellulose chains as containing both crystalline (ordered) and amorphous (less ordered) region (park et al., 2010). alkali treatment of bagasse has been found to increase the crystallinity index of the bagasse. alkali treatment breaks down hemicellulose, making the cellulose molecules more ordered and crystalline, resulting in a higher crystallinity index. alkali treatment also increases the digestibility of the bagasse, making it easier to break down and therefore more suitable for bioenergy production. x-ray diffraction spectra of the sb and alkali treated sb were presented in figure 4. it was observed that the intensity of 101 and 002 peaks were gradually increased. the relative amount of crystalline cellulose (cri) in the total solid were calculated based on the equation (2) and obtained 18.68%, 24.80%, 27.23%, 32.69%, 36.45% and 39.19% for raw sb, 0%, 2%, 4%, 6% and 8% alkali treated sb samples respectively. the cri of alkali treated sb samples (not cellulose crystallinity) were intensely influenced by the composition of the samples. in case of lignocellulosic biomass examples, cellulose cri measured the relative amount of crystalline cellulose in the total solid. therefore, amorphous part of lignin and hemicellulose in biomass specimens were partially removed with the delignification process as a result the proportion of α-cellulose was increased and hence cri would be increased gradually. this interpretation could be proved by the fact that alkali-treated sb had higher cri than raw sb (zhao et al. 2010) and the portion of cellulose in the treated sb was also increased gradually. according to the equation 3, the average sizes of crystallite obtained were 3.28, 3.51, 3.63, 3.78, 3.90 and 4.06 nm for raw sb, 0%, 2%, 4%, 6% and 8% alkali treated sb samples respectively. the experimental data revealed that during delignification, the size of crystallite was increased. sem analysis sem is one of the most commanding tools widely used to investigate the lignocellulosic biomass surface (amiri and karimi, 2015). sem is usually employed for surface characterization, morphology and inspection of microstructure. in respect of biomass example through sem images we can compare the untreated and pretreated models which may lead to different insight into the biomass (karimi and taherzadeh, 2016). sem provides two-dimensional images of raw sb and alkali treated sb, which were taken and compared to the outcome of naoh treatment. all testers were coated with carbon tape and magnification of 500x was used. figure 4 shows the wall of raw sb (figure 6a) was intact where the alkali treated sb (figures 6c-6f), the cell wall was ruptured or splitted and hence packing of the fibers were partially loosened (firoz et al. 2012). sugar and ethanol yield enzymatic digestibility is the ability of enzymes to break down molecules into smaller molecules, such as glucose. it is used to measure the efficiency of enzyme-catalyzed reactions and the digestibility of cellulose. the enzymatic digestibility of a compound is affected by factors such as the compound's crystallinity index, the type of enzyme used, and the temperature and ph of the reaction. in this study the enzymatic digestibility of the alkali pretreated sb was improved by increasing pretreatment conditions. typically the pretreatment settings are selected by considering various factors such as feedstock characteristics, pretreatment chemical cost, energy consumption and recovery efficiency (wu et al. 2011). α-cellulose obtained by 8% alkali treated of sb was used for hydrolysis reaction and the reaction was carried out at an optimum condition set by sujan et al. (2018). the most effective enzymatic hydrolysis was taken place with trichoderma virideat 48 h and the theoretical yield of sugars i.e. glucose and xylose were obtained 89.59% and 61.23%, respectively. through fermentation process generated sugars were used to check ethanol production. yeast saccharomyces cerevisiae presented worthy performance to convert c6 sugar into ethanol when it was incubated at 30°c for 24 h and 16.81±0.32% ethanol yield was detected. conclusion α-cellulose yield was optimized by varying alkali concentration, temperature and cooking time. the most vital influencing factor for α-cellulose yield was alkali concentration and after that temperature performed a little bit. the optimum α-cellulose yield (63.58±0.05%) was obtained at 8% alkali concentration, 100oc and 90 minutes. in hydrolysis step of sb, trichoderma viridaewas used to convert 8% alkali treated sb into sugars and it was attained 89.59% glucose and 61.23% xylose which gave higher yield in compare with our previous study such as ball milled and mesh size varied sb sample (sujan et al. 2018). at fermentation step saccharomyces cerevisiae was used to convert hydrolysate of 8% alkali treated sb sample and ethanol yield was obtained 16.81±0.32% at 24 h. compositional analysis, imaging and crystallinity are three methods were performed. sem images can give different clues about sb including morphology, surface disruption and creation of highly accessible surface area iii) cri (18.68% to 39.19%) and crystal size (3.28 nm to 4.06 nm) of sb are increased with different alkali treatment (0%-8%). in this case it was observed that crystallinity, crystal size, accessible surface area, porosity, particle size, lignin and hemicellulose content and enzyme adsorption/desorption were acted as the most impressive factors for digestibility of sugarcane bagasse. acknowledgement authors would like to acknowledge pulp and paper division, bcsir for their cooperation. authors also like to thanks for the sincere assistance of md. abdul hamid, junior technician, ifrd, bcsir. references alvira p, tomás-pejó e, ballesteros m and negro mj (2010), pretreatment technologies for an efficient bioethanol production process based on enzymatic hydrolysis: a review, bioresource technology 101(13): 4851-4861. doi: org/10.1016/j.biortech.2009.11.093 agbor vb, cicek n, sparling r, berlin a and levin, db (2011), biomass pretreatment: fundamentals toward application, biotechnology advances 29(6): 675-685. doi: org/10.1016/j.biotechadv.2011.05.005 amiri h and karimi k (2015), improvement of acetone, butanol, and ethanol production from woody biomass using organosolv pretreatment, bioprocess and biosystems engineering 38(10): 1959-1972. astm (2007), standard test members for instrumental determination of c, h, n in petroleum products and lubricants. astm d5291-02, astm international, west conshohocken, pa. canilha l, chandel ak, suzane dos santos milessi t, antunes faf, luiz da costa freitas w, das graças almeida felipe m and da silva ss (2012), bioconversion of sugarcane biomass into ethanol: an overview about composition, pretreatment methods, detoxification of hydrolysates, enzymatic saccharification and ethanol fermentation. journal of biomedicine and biotechnology, doi: org/10.1155/2012/989572 den w, sharma vk, lee m, nadadur g and varma rs (2018), lignocellulosic biomass transformations via greener oxidative pretreatment processes: access to energy and value-added chemicals, frontiers in chemistry 6: 141. doi: org/10.3389/fchem.2018.00141 ahmed fm, rahman sr and gomes dj (2012), saccharification of sugarcane bagasse by enzymatic treatment for bioethanol production, malays j microbiol 8(2), 97-103. hirani ah, javed n, asif m, basu sk and kumar a (2018), a review on first-and second-generation biofuel productions. in biofuels: greenhouse gas mitigation and global warming, springer, new delhi, pp 141-154. doi: 10.1007/978-81-322-3763-1_8 islam mz, asad ma, hossain mt, paul sc and sujan sma (2019), bioethanol production from banana pseudostem by using separate and cocultures of cellulase enzyme with saccharomyces cerevisiae, journal of environmental science and technology 12(4): 157-163. jahan ms, saeed a, ni y and he z (2009), pre-extraction and its impact on the alkaline pulping of bagasse, journal of biobased materials and bioenergy 3(4): 380-385. doi: org/10.1166/jbmb.2009.1053 janker-obermeier i, sieber v, faulstich mand schieder d (2012), solubilization of hemicellulose and lignin from wheat straw through microwave-assisted alkali treatment, industrial crops and products 39: 198-203. doi: org/10.1016/j.indcrop.2012.02.022 karimi k and taherzadeh mj (2016), a critical review of analytical methods in pretreatment of lignocelluloses: composition, imaging, and crystallinity, bioresource technology 200: 1008-1018. doi: org/10.1016/j. biortech.2015.11.022 maryana r, ma’rifatun d, wheni ai, satriyo kw and rizal wa (2014), alkaline pretreatment on sugarcane bagasse for bioethanol production, energy procedia, 47: 250-254. doi: org/10.1016/j.egypro.2014.01.221 mcintosh sand vancov t (2010), enhanced enzyme saccharification of sorghum bicolor straw using dilute alkali pretreatment, bioresource technology 101(17): 6718-6727. doi: org/10.1016/j.biortech.2010.03.116 meyer kh and misch l (1937), positions des atomes dans le nouveau modele spatial de la cellulose. helvetica chimica acta 20(1): 232-244. doi: org/10. 1002/hlca.19370200134 park s, baker jo, himmel me, parilla pa and johnson dk (2010), cellulose crystallinity index: measurement techniques and their impact on interpreting cellulase performance, biotechnology for biofuels 3(1): 10. sujan sma, bari ml and fakhruddin an (2018), effects of physical pretreatment (crushing and ball milling) on sugarcane bagasse for bioethanol production, bangladesh journal of botany 147(2): 257-64. wilkie js (1961), carl nägeli and the fine structure of living matter, nature 190: 1145-1150. wu l, arakane m, ike m, wada m, takai t, gau mand tokuyasu k (2011), low temperature alkali pretreatment for improving enzymatic digestibility of sweet sorghum bagasse for ethanol production, bioresource technology 102(7): 4793-4799. zhang w, okubayashi s and bechtold t (2005), fibrillation tendency of cellulosic fibers-part 4. effects of alkali pretreatment of various cellulosic fibers, carbohydrate polymers. 61(4): 427-433. zhao x, van der heide e, zhang tand liu d (2010), delignification of sugarcane bagasse with alkali and peracetic acid and characterization of the pulp, bioresources 5(3): 1565-1580. zhao x, zhang land liu d (2012), biomass recalcitrance. part ii: fundamentals of different pre‐treatments to increase the enzymatic digestibility of lignocellulose, biofuels, bioproducts and biorefining 6(5): 561-579. table ii. ultimate analysis of sugarcane bagasse (20-40 mesh) name of sample carbon (%) oxygen (%) hydrogen (%) nitrogen (%) sulfur (%) sb 44.89 49.6 5.51 0 0 table iii. chemical pretreatment of sb with different concentration of naoh, temperature and time for the yield of α-cellulose, pentosan and lignin yield alkali (naoh) solution (%) temperature (oc) time (min) α-cellulose yield (%) pentosan yield (%) lignin yield (%) 0% 80 60 34.66±0.05 22.43±0.02 19.57±0.03 0% 80 90 34.76±0.02 22.56±0.01 19.42±0.01 0% 100 60 34.88±0.01 22.68±0.03 19.39±0.01 0% 100 120 34.90±0.01 22.75±0.02 19.25±0.06 0% 120 90 34.98±0.02 22.88±0.02 19.16±0.01 2% 80 60 37.02±0.10 23.20±0.01 17.77±0.09 2% 80 90 37.32±0.08 23.35±0.03 17.23±0.05 2% 100 60 38.13±0.03 23.60±0.04 17.14±0.01 2% 100 90 38.99±0.05 23.84±0.03 17.05±0.02 2% 120 120 38.46±0.08 23.25±0.02 16.73±0.06 4% 80 90 44.98±0.13 23.96±0.05 14.96±0.08 4% 80 120 45.46±0.09 24.26±0.08 14.85±0.01 4% 100 60 47.43±0.11 24.53±0.04 14.66±0.05 4% 100 90 48.05±0.06 24.87±0.05 14.50±0.01 4% 120 60 47.86±0.09 24.95±0.02 14.41±0.06 6% 80 60 53.45±0.11 25.09±0.03 12.86±0.08 6% 80 90 53.95±0.08 25.21±0.02 12.58±0.06 6% 100 90 55.79±0.05 25.86±0.03 12.29±0.02 6% 100 120 54.35±0.03 25.89±0.01 12.11±0.02 6% 120 60 54.88±0.04 25.99±0.02 12.01±0.02 8% 80 60 59.24±0.14 26.15±0.04 10.79±0.10 8% 80 120 59.95±0.02 26.32±0.02 10.69±0.01 8% 100 60 61.67±0.11 26.56±0.03 10.17±0.08 8% 100 90 63.58±0.05 26.75±0.02 09.01±0.02 8% 120 90 62.59±0.04 26.86±0.02 09.30±0.04 12% 100 90 66.14±0.06 27.46±0.04 06.22±0.05 optimization of alkali concentration in the pretreatment of sugarcane bagasse 58(2) 202394 composed of vasculer bundles surrounded by non-fibrous parenchymatic cell (jahan et al. 2009). usually it is available as agricultural residue and byproduct from sugar mill industries. in the year of 2015-16, there was 2,95,162 metric ton sugarcane bagasse was obtained from sugar mills of bangladesh (http://www.bsfic.gov.bd). to enrich cellulose content in biomass for enzymatic saccarification, current research has focused on various pretreatment processes. currently, scientists have gone through a lot of studies on different pretreatment techniques to remove the compact and rigid composition by open up the cellulosic structure (alvira et al. 2010). pretreatment technologies are commonly abandoned to reduce the structural barriers and boost cellulose availability based on not only chemicals such as acid, alkali, oxidant, etc. but also several treatment settings. alkali treatment is one of the most widespread and economical methods used for surface modification of lignocellulosic biomass. in the field of biorefinary, alkali pretreatment is intensively employed to develop the cellulosic materials both mechanically as well as chemically and such properties include tensile strength, dyeability, stability of dimension and reactivity (wu et al. 2011). in alkali pretreatment biomass is treated under moderate reaction conditions ensuring inexpensiveness, inflated recycling possibilities of water and chemical agents (mcintosh and vancov, 2010). usually alkali treatment is the most effective pretreatment for agricultural residues, herbaceous crops and hardwood containing low lignin content in the compariosn of softwood containing high lignin content (agbor et al. 2011; canilha et al. 2012). this research aims is to investigate the alkaline pretreatment repercussions based on the chemical structure, surface morphology, structure and enzymatic digestion of sugarcane bagasse for sugars and ethanol production. materials and methods sugarcane bagasse (sb) was taken from street juice vendor. warm tap water was used for washing purpose to eliminate the residual free sugars once again. this washing and pressing step was then repeated for three times. after that drying was done in an oven at 65oc for 16 h. crushing of dried bagasse was done successively using a locally made crusher and sieved (retsch, d-42759, haan, germany) to have the particle size of 20-40 mesh on average. before usage, the 20-40 mesh bagasse was kept at room temperature in an airtight plastic container (sujan et al. 2018). moisture and ash content moisture content of raw materials was measured using the astm d 4442-07 procedure. in a glass crucible, 2 grams of pretreatment sample containing 20-40 mesh were dried in oven at 105±2°c. the moisture content was expressed in percent wet basis and weight measurements were taken every 3 h. a muffle furnace was used for burning the oven-dried samples at 575±25°c for ash content determination following the astm standard e 1755-01. volatile matter the volatile matter analysis was carried out in accordance with astm standard d 271-48. four grams of raw materials were heated in a furnace at 950±20°c for seven minutes. the weight loss, excluding the weight of moisture pushed off at 105°c, is then used to calculate volatile matter. fixed carbon the difference between 100 and the total of volatile matter, moisture, and ash content was used to compute the fixed carbon percentage. chemical analysis the technical association of the pulp and paper industry (tappi) method detects α-cellulose (t 203 cm-99), pentosan (t 223 cm-01), klason lignin (t211 om-83), and acid soluble lignin (t um 250) on a dry basis. ultimate analysis ultimate analysis of samples was done by following the procedure astm standard d 5291-02. organic elemental analyzer (flash 2000, thermo scientific, usa) was used with a specific condition (reactor temp. 900°c, he: 250 kpa, o2: 250 kpa, tcd). low concentration alkali pretreatment different alkali concentration (0%, 2%, 4%, 6% and 8%), time (60, 90 and 120 min) and temperature (80, 100 and 120oc) were applied on raw material to check alkali effect on sb shown in table 3. a portion of the ground bagasse 20-40 mesh (10g) was taken into plastic zipper bag (temperature 80oc, figure 2a and 2b) and stainless-steel reactor (temperature 100oc and 120oc, figure 2c and 2d). different alkali concentration was applied during the pretreatment process (alkali to sb ratio ranging between 1:12). the mixture was heated at a particular temperature such as in a water bath (80oc) and oil bath (100oc and 120oc) for a desired length of time. in the course of pretreatment process the sample was manually mixed 2-3 times to attain proper alkali treatment. the treated sb was placed into a polyester bag to remove excess alkali water by pressing it. after that it was vigorously washed with tap water (repeated for five times) to remove the remaining alkali. finally the sb was dried in an oven at 65oc for 72 h and stored in a close container at room temperature for further experiment. regression model regression model has been developed for prediction of α-cellulose, pentosan and lignin in sb. the general form of the model is: y=α+α1x1 + α2x2+........................+αnxn + ε.......................(1) where α is the constant term. αi are the coefficient of variables xi. ε is the random error term which is minimized with simple least squares regression (slsr). regression coefficients of the independent variables namely alkali concentration, temperature and time are estimated by slsr method for developing regression model to predict α-cellulose, pentosan and lignin. efficiencies of these models are expressed by coefficient of multiple determination (r2) and adjusted r2. 2.9 separate hydrolysis and fermentation (shf) the hydrolysis experiment took place in 100 ml conical flux 10ml enzyme solution with 200 mg (2% dry wt.) in citrate buffer (0.05 m, ph 5.0) at 50°c for 48 h. in this case trichoderma viride was used for hydrolysis. hydrolysate was then heated for 15 min in a boiling water bath and centrifugation was done to remove solid particles. the supernatant was used for analysis of released sugars as described by jamal et al. (2011). during fermentation process according to firoz et al. (2012), 100 ml media was prepared and 0.5 g of commercial yeast saccharomyces cerevisiae was used as inoculum which showed good performance to converts sugar into bioethanol. this inoculated media mixture was poured in a suitable glassware and was kept in a shaking incubator for 48 h. 10 ml of this medium was then added into the flask and it was properly covered with aluminum foil. then it was placed in the incubator at 30oc for 24 h, 48 h, 72 h and 96 h for fermentation of sugars to bio-ethanol according to sujan et al. (2018). samples from hydrolysis and fermentation were performed by hplc. high performance liquid chromatography (hplc) in characterize part, concentration of sugars and ethanol were determined by hplc (ultimate 3000, thermo scientific, usa) method using hyper rez xp carbohydrate h+ 8 µm column (100×7.7 mm) equipped with a refractive index (shodex ri-101) detector. the mobile phase was degassed with deionized water with a flow rate of 0.7 ml/min and column temperature was maintained at 70°c. it is possible to measure the total sugar concentration in the hydrolysis liquid fraction by comparing its peak area detected by hplc with peak area of 1% standard sugar which consists of two sugars namely glucose and xylose (sujan et al. 2018). the same column which is specialized for fermentation broth analysis is used for ethanol detection. the kinetic parameters of ethanol fermentation were determined as follows (islam et al. 2019): crystallinity measurement x-ray diffraction (xrd) was used to determine the crystalline structure of the sb samples using a diffractometer (gbc xrd) and filtered copper k radiation (λ = 0.1542 nm) by a monochromator at 35.50 kv voltage and 28 ma current, with a speed of about 2o/min and scanning in the range of 10 80ºc. the crystallinity index (cri) was obtained from the ratio between the intensity of the 002 peak (i002, 2θ = 22.5) and the minimum dip (iam, 2 θ = 18.5) according to the following equation (roberta et al., 2012): cri (%) = [(i002 iam)/i002] ×100 ...................................... (2) where i002 is the highest peak intensity of plane 002 and iam is related to the amorphous structure. in present study, the average crystallite sizes were determined from the scherrer equation by using the diffraction pattern obtained from the 002 (hkl) lattice planes of cellulose samples d(hkl) = [(kλ / b(hkl) cos2θ] ............................................... (3) where d(hkl) (crystallite size), k (scherrer constant, 0.84), λ (x-ray wavelength, 0.154nm), b(hkl)(full width half maximum of the measured hkl reflection), and 2θ (corresponding bragg angle). scanning electron microscopy (sem) analysis in this research, sem (zeiss evo 18 sem) was used to detect the change of pretreated bagasse fibers. sem images were taken of different pretreated bagasse samples with acceleration voltage of 2.0 kv. results and discussion proximate analysis proximate analysis of sb sample (20-40 mesh) are presented in table i. primarily this analysis usually evaluate the fuel characteristics of raw materials. according to sun et al., 2009, higher moisture and ashcontent in samples lessen the heating value. ultimate analysis ultimate analysis denotes the elemental configuration of sb such as carbon, hydrogen, oxygen, nitrogen and sulfur which are shown in table ii. this examination helps to measure the percentage of carbon and hydrogen content in biomass that is responsible to determine the amount of air is required for complete combustion, composition of combustion gases and heat is generated by it (poddar et al. 2014). chemical properties raw sb contained 34.66±12% α-cellulose, 22.43±08% pentosan and 19.57±06% klason lignin in which 1.75±04% acid soluble lignin (dry basis) was detected by technical association of the pulp and paper industry (tappi) method. the chemical composition of sb was determined by acid hydrolysis and it was calculatedby hplc method as 45.35% glucose and 30.64% xylose (sujan et al., 2018). α-cellulose yield bagasse is mainly composed of cellulose, hemicellulose and lignin. besides these there are some extractives such as ash, wax, gum, pectin etc. during alkali pretreatment usually most of the extractives are removed with the increasing of alkali concentration. pretreatment of sb with different alkali concentration based on raw material (0%, 2%, 4%, 6% and 8%), time (60, 90 and 120 min) and temperature (80, 100 and 120oc) are shown in table iii. consequences of each independent experiment varying with alkali concentration, temperature and time on the α-cellulose yield were analyzed using matlab software. apparently, it was observed that α-cellulose yield was considerably increased with changes of alkali concentration ranging from 0% to 8% (34.66% to 63.58%). but no noticeable variation was observed in temperature-time alteration during pretreatment of sb. based on cellulose percentage obtained in treated bagasse, the optimum conditions for pretreatment reaction were selected as alkali concentration 8%, time 90 min and temperature 100oc. although cellulose content in treated sb was slowly increased with the increase of alkali concentration 12% attime 90 min and temperature 100oc but as a consequence of huge chemical consumption, recovery problem, chance of losses cellulose and hemicellulose, alkali concentrations for pretreatment above 8% was not considered as ideal concentration. effect of alkali concentration (ac), cooking time and temperature (temp) charge on α-cellulose yield as well as their statistical significance on the basis of f-test number are presented in regression equations (4). as shown in equations, cooking time at the maximum temperature had no significant effect on α-cellulose yield followed by alkali concentration charge. effect of temperature on α-cellulose yield was less in employed cooking conditions. for α-cellulose yield: α-cellulose yield = 82.05-0.151×temp-1.56×time-0.69×ac (r2=0.89, adjusted r2=0.87) ............................................. (4) for pentosan: pentosan = 13.58+0.086 × tem p + 0.006 × time+0.445 × ac (r2=0.67, adjusted r2=0.63) ............................................. (5) for lignin: lignin = 27.662-0.041×temp-0.001×time-01.242×ac (r2=0.93, adjusted r2=0.92) ............................................. (6) for predicting α-cellulose, percentage of pentosan and lignin, the most influential factor was alkali concentration and then cooking temperature for α-cellulose yield, which exhibited an almost linear dependence on both operational variables. the coefficient of determinations is good for α-cellulose yield and lignin percentage which hovers around 90 percent, although the figure is moderate more than 60 percent for pentosan. all these three models are significant (p<0.05) at 5% level of significance. in order to perceive the impact of alkali concentration and temperature on these three parameters, three-dimensional (3d) response surface plots were created by plotting the response (α-cellulose yield) pentosan and lignin on the z-axis versus the most influential one independent variable alkali concentration and temperature as shown in fig. 3 (a), (b) and (c). xrd analysis in 19th century the cellulose crystalline structure has been discovered and later it was verified by x-ray crystallography (meyer and misch, 1937; wilkie, 1961). the crystallinity index (cri) of non-woody biomass, such as grasses and agricultural residues, varies depending on the type of biomass. generally, non-woody biomass has a lower crystallinity index than woody biomass, typically ranging from 20-40%. the crystallinity index of non-woody biomass affects its digestibility and energy production potential.recently, researchers are being paid more attention on cellulose index because of its potential use in bioenergy production. since then several different models of cellulose index have been proposed. the most popular two-phase cellulose model describes cellulose chains as containing both crystalline (ordered) and amorphous (less ordered) region (park et al., 2010). alkali treatment of bagasse has been found to increase the crystallinity index of the bagasse. alkali treatment breaks down hemicellulose, making the cellulose molecules more ordered and crystalline, resulting in a higher crystallinity index. alkali treatment also increases the digestibility of the bagasse, making it easier to break down and therefore more suitable for bioenergy production. x-ray diffraction spectra of the sb and alkali treated sb were presented in figure 4. it was observed that the intensity of 101 and 002 peaks were gradually increased. the relative amount of crystalline cellulose (cri) in the total solid were calculated based on the equation (2) and obtained 18.68%, 24.80%, 27.23%, 32.69%, 36.45% and 39.19% for raw sb, 0%, 2%, 4%, 6% and 8% alkali treated sb samples respectively. the cri of alkali treated sb samples (not cellulose crystallinity) were intensely influenced by the composition of the samples. in case of lignocellulosic biomass examples, cellulose cri measured the relative amount of crystalline cellulose in the total solid. therefore, amorphous part of lignin and hemicellulose in biomass specimens were partially removed with the delignification process as a result the proportion of α-cellulose was increased and hence cri would be increased gradually. this interpretation could be proved by the fact that alkali-treated sb had higher cri than raw sb (zhao et al. 2010) and the portion of cellulose in the treated sb was also increased gradually. according to the equation 3, the average sizes of crystallite obtained were 3.28, 3.51, 3.63, 3.78, 3.90 and 4.06 nm for raw sb, 0%, 2%, 4%, 6% and 8% alkali treated sb samples respectively. the experimental data revealed that during delignification, the size of crystallite was increased. sem analysis sem is one of the most commanding tools widely used to investigate the lignocellulosic biomass surface (amiri and karimi, 2015). sem is usually employed for surface characterization, morphology and inspection of microstructure. in respect of biomass example through sem images we can compare the untreated and pretreated models which may lead to different insight into the biomass (karimi and taherzadeh, 2016). sem provides two-dimensional images of raw sb and alkali treated sb, which were taken and compared to the outcome of naoh treatment. all testers were coated with carbon tape and magnification of 500x was used. figure 4 shows the wall of raw sb (figure 6a) was intact where the alkali treated sb (figures 6c-6f), the cell wall was ruptured or splitted and hence packing of the fibers were partially loosened (firoz et al. 2012). sugar and ethanol yield enzymatic digestibility is the ability of enzymes to break down molecules into smaller molecules, such as glucose. it is used to measure the efficiency of enzyme-catalyzed reactions and the digestibility of cellulose. the enzymatic digestibility of a compound is affected by factors such as the compound's crystallinity index, the type of enzyme used, and the temperature and ph of the reaction. in this study the enzymatic digestibility of the alkali pretreated sb was improved by increasing pretreatment conditions. typically the pretreatment settings are selected by considering various factors such as feedstock characteristics, pretreatment chemical cost, energy consumption and recovery efficiency (wu et al. 2011). α-cellulose obtained by 8% alkali treated of sb was used for hydrolysis reaction and the reaction was carried out at an optimum condition set by sujan et al. (2018). the most effective enzymatic hydrolysis was taken place with trichoderma virideat 48 h and the theoretical yield of sugars i.e. glucose and xylose were obtained 89.59% and 61.23%, respectively. through fermentation process generated sugars were used to check ethanol production. yeast saccharomyces cerevisiae presented worthy performance to convert c6 sugar into ethanol when it was incubated at 30°c for 24 h and 16.81±0.32% ethanol yield was detected. conclusion α-cellulose yield was optimized by varying alkali concentration, temperature and cooking time. the most vital influencing factor for α-cellulose yield was alkali concentration and after that temperature performed a little bit. the optimum α-cellulose yield (63.58±0.05%) was obtained at 8% alkali concentration, 100oc and 90 minutes. in hydrolysis step of sb, trichoderma viridaewas used to convert 8% alkali treated sb into sugars and it was attained 89.59% glucose and 61.23% xylose which gave higher yield in compare with our previous study such as ball milled and mesh size varied sb sample (sujan et al. 2018). at fermentation step saccharomyces cerevisiae was used to convert hydrolysate of 8% alkali treated sb sample and ethanol yield was obtained 16.81±0.32% at 24 h. compositional analysis, imaging and crystallinity are three methods were performed. sem images can give different clues about sb including morphology, surface disruption and creation of highly accessible surface area iii) cri (18.68% to 39.19%) and crystal size (3.28 nm to 4.06 nm) of sb are increased with different alkali treatment (0%-8%). in this case it was observed that crystallinity, crystal size, accessible surface area, porosity, particle size, lignin and hemicellulose content and enzyme adsorption/desorption were acted as the most impressive factors for digestibility of sugarcane bagasse. acknowledgement authors would like to acknowledge pulp and paper division, bcsir for their cooperation. authors also like to thanks for the sincere assistance of md. abdul hamid, junior technician, ifrd, bcsir. references alvira p, tomás-pejó e, ballesteros m and negro mj (2010), pretreatment technologies for an efficient bioethanol production process based on enzymatic hydrolysis: a review, bioresource technology 101(13): 4851-4861. doi: org/10.1016/j.biortech.2009.11.093 agbor vb, cicek n, sparling r, berlin a and levin, db (2011), biomass pretreatment: fundamentals toward application, biotechnology advances 29(6): 675-685. doi: org/10.1016/j.biotechadv.2011.05.005 amiri h and karimi k (2015), improvement of acetone, butanol, and ethanol production from woody biomass using organosolv pretreatment, bioprocess and biosystems engineering 38(10): 1959-1972. astm (2007), standard test members for instrumental determination of c, h, n in petroleum products and lubricants. astm d5291-02, astm international, west conshohocken, pa. canilha l, chandel ak, suzane dos santos milessi t, antunes faf, luiz da costa freitas w, das graças almeida felipe m and da silva ss (2012), bioconversion of sugarcane biomass into ethanol: an overview about composition, pretreatment methods, detoxification of hydrolysates, enzymatic saccharification and ethanol fermentation. journal of biomedicine and biotechnology, doi: org/10.1155/2012/989572 den w, sharma vk, lee m, nadadur g and varma rs (2018), lignocellulosic biomass transformations via greener oxidative pretreatment processes: access to energy and value-added chemicals, frontiers in chemistry 6: 141. doi: org/10.3389/fchem.2018.00141 ahmed fm, rahman sr and gomes dj (2012), saccharification of sugarcane bagasse by enzymatic treatment for bioethanol production, malays j microbiol 8(2), 97-103. hirani ah, javed n, asif m, basu sk and kumar a (2018), a review on first-and second-generation biofuel productions. in biofuels: greenhouse gas mitigation and global warming, springer, new delhi, pp 141-154. doi: 10.1007/978-81-322-3763-1_8 islam mz, asad ma, hossain mt, paul sc and sujan sma (2019), bioethanol production from banana pseudostem by using separate and cocultures of cellulase enzyme with saccharomyces cerevisiae, journal of environmental science and technology 12(4): 157-163. jahan ms, saeed a, ni y and he z (2009), pre-extraction and its impact on the alkaline pulping of bagasse, journal of biobased materials and bioenergy 3(4): 380-385. doi: org/10.1166/jbmb.2009.1053 janker-obermeier i, sieber v, faulstich mand schieder d (2012), solubilization of hemicellulose and lignin from wheat straw through microwave-assisted alkali treatment, industrial crops and products 39: 198-203. doi: org/10.1016/j.indcrop.2012.02.022 karimi k and taherzadeh mj (2016), a critical review of analytical methods in pretreatment of lignocelluloses: composition, imaging, and crystallinity, bioresource technology 200: 1008-1018. doi: org/10.1016/j. biortech.2015.11.022 maryana r, ma’rifatun d, wheni ai, satriyo kw and rizal wa (2014), alkaline pretreatment on sugarcane bagasse for bioethanol production, energy procedia, 47: 250-254. doi: org/10.1016/j.egypro.2014.01.221 mcintosh sand vancov t (2010), enhanced enzyme saccharification of sorghum bicolor straw using dilute alkali pretreatment, bioresource technology 101(17): 6718-6727. doi: org/10.1016/j.biortech.2010.03.116 meyer kh and misch l (1937), positions des atomes dans le nouveau modele spatial de la cellulose. helvetica chimica acta 20(1): 232-244. doi: org/10. 1002/hlca.19370200134 park s, baker jo, himmel me, parilla pa and johnson dk (2010), cellulose crystallinity index: measurement techniques and their impact on interpreting cellulase performance, biotechnology for biofuels 3(1): 10. sujan sma, bari ml and fakhruddin an (2018), effects of physical pretreatment (crushing and ball milling) on sugarcane bagasse for bioethanol production, bangladesh journal of botany 147(2): 257-64. wilkie js (1961), carl nägeli and the fine structure of living matter, nature 190: 1145-1150. wu l, arakane m, ike m, wada m, takai t, gau mand tokuyasu k (2011), low temperature alkali pretreatment for improving enzymatic digestibility of sweet sorghum bagasse for ethanol production, bioresource technology 102(7): 4793-4799. zhang w, okubayashi s and bechtold t (2005), fibrillation tendency of cellulosic fibers-part 4. effects of alkali pretreatment of various cellulosic fibers, carbohydrate polymers. 61(4): 427-433. zhao x, van der heide e, zhang tand liu d (2010), delignification of sugarcane bagasse with alkali and peracetic acid and characterization of the pulp, bioresources 5(3): 1565-1580. zhao x, zhang land liu d (2012), biomass recalcitrance. part ii: fundamentals of different pre‐treatments to increase the enzymatic digestibility of lignocellulose, biofuels, bioproducts and biorefining 6(5): 561-579. fig. 3. surface plot of (a) α-cellulose, (b) pentosan and (c) lignin against alkali concentration and temperature 120 a lfa cellulose 30 40 100 50 60 temperature0.0 2.5 805.0 7.5 a lk ali concentration 120 pentosan 20 100 22 24 26 t emperature 0.0 2.5 805.0 7.5 a lk ali concentr ation 120 lignin 10 100 15 20 t emper ature 25 0.0 2.5 805.0 7.5 a lk ali concentration 3a 3b 3c sujan, hossain, uddin and fakhruddin 95 composed of vasculer bundles surrounded by non-fibrous parenchymatic cell (jahan et al. 2009). usually it is available as agricultural residue and byproduct from sugar mill industries. in the year of 2015-16, there was 2,95,162 metric ton sugarcane bagasse was obtained from sugar mills of bangladesh (http://www.bsfic.gov.bd). to enrich cellulose content in biomass for enzymatic saccarification, current research has focused on various pretreatment processes. currently, scientists have gone through a lot of studies on different pretreatment techniques to remove the compact and rigid composition by open up the cellulosic structure (alvira et al. 2010). pretreatment technologies are commonly abandoned to reduce the structural barriers and boost cellulose availability based on not only chemicals such as acid, alkali, oxidant, etc. but also several treatment settings. alkali treatment is one of the most widespread and economical methods used for surface modification of lignocellulosic biomass. in the field of biorefinary, alkali pretreatment is intensively employed to develop the cellulosic materials both mechanically as well as chemically and such properties include tensile strength, dyeability, stability of dimension and reactivity (wu et al. 2011). in alkali pretreatment biomass is treated under moderate reaction conditions ensuring inexpensiveness, inflated recycling possibilities of water and chemical agents (mcintosh and vancov, 2010). usually alkali treatment is the most effective pretreatment for agricultural residues, herbaceous crops and hardwood containing low lignin content in the compariosn of softwood containing high lignin content (agbor et al. 2011; canilha et al. 2012). this research aims is to investigate the alkaline pretreatment repercussions based on the chemical structure, surface morphology, structure and enzymatic digestion of sugarcane bagasse for sugars and ethanol production. materials and methods sugarcane bagasse (sb) was taken from street juice vendor. warm tap water was used for washing purpose to eliminate the residual free sugars once again. this washing and pressing step was then repeated for three times. after that drying was done in an oven at 65oc for 16 h. crushing of dried bagasse was done successively using a locally made crusher and sieved (retsch, d-42759, haan, germany) to have the particle size of 20-40 mesh on average. before usage, the 20-40 mesh bagasse was kept at room temperature in an airtight plastic container (sujan et al. 2018). moisture and ash content moisture content of raw materials was measured using the astm d 4442-07 procedure. in a glass crucible, 2 grams of pretreatment sample containing 20-40 mesh were dried in oven at 105±2°c. the moisture content was expressed in percent wet basis and weight measurements were taken every 3 h. a muffle furnace was used for burning the oven-dried samples at 575±25°c for ash content determination following the astm standard e 1755-01. volatile matter the volatile matter analysis was carried out in accordance with astm standard d 271-48. four grams of raw materials were heated in a furnace at 950±20°c for seven minutes. the weight loss, excluding the weight of moisture pushed off at 105°c, is then used to calculate volatile matter. fixed carbon the difference between 100 and the total of volatile matter, moisture, and ash content was used to compute the fixed carbon percentage. chemical analysis the technical association of the pulp and paper industry (tappi) method detects α-cellulose (t 203 cm-99), pentosan (t 223 cm-01), klason lignin (t211 om-83), and acid soluble lignin (t um 250) on a dry basis. ultimate analysis ultimate analysis of samples was done by following the procedure astm standard d 5291-02. organic elemental analyzer (flash 2000, thermo scientific, usa) was used with a specific condition (reactor temp. 900°c, he: 250 kpa, o2: 250 kpa, tcd). low concentration alkali pretreatment different alkali concentration (0%, 2%, 4%, 6% and 8%), time (60, 90 and 120 min) and temperature (80, 100 and 120oc) were applied on raw material to check alkali effect on sb shown in table 3. a portion of the ground bagasse 20-40 mesh (10g) was taken into plastic zipper bag (temperature 80oc, figure 2a and 2b) and stainless-steel reactor (temperature 100oc and 120oc, figure 2c and 2d). different alkali concentration was applied during the pretreatment process (alkali to sb ratio ranging between 1:12). the mixture was heated at a particular temperature such as in a water bath (80oc) and oil bath (100oc and 120oc) for a desired length of time. in the course of pretreatment process the sample was manually mixed 2-3 times to attain proper alkali treatment. the treated sb was placed into a polyester bag to remove excess alkali water by pressing it. after that it was vigorously washed with tap water (repeated for five times) to remove the remaining alkali. finally the sb was dried in an oven at 65oc for 72 h and stored in a close container at room temperature for further experiment. regression model regression model has been developed for prediction of α-cellulose, pentosan and lignin in sb. the general form of the model is: y=α+α1x1 + α2x2+........................+αnxn + ε.......................(1) where α is the constant term. αi are the coefficient of variables xi. ε is the random error term which is minimized with simple least squares regression (slsr). regression coefficients of the independent variables namely alkali concentration, temperature and time are estimated by slsr method for developing regression model to predict α-cellulose, pentosan and lignin. efficiencies of these models are expressed by coefficient of multiple determination (r2) and adjusted r2. 2.9 separate hydrolysis and fermentation (shf) the hydrolysis experiment took place in 100 ml conical flux 10ml enzyme solution with 200 mg (2% dry wt.) in citrate buffer (0.05 m, ph 5.0) at 50°c for 48 h. in this case trichoderma viride was used for hydrolysis. hydrolysate was then heated for 15 min in a boiling water bath and centrifugation was done to remove solid particles. the supernatant was used for analysis of released sugars as described by jamal et al. (2011). during fermentation process according to firoz et al. (2012), 100 ml media was prepared and 0.5 g of commercial yeast saccharomyces cerevisiae was used as inoculum which showed good performance to converts sugar into bioethanol. this inoculated media mixture was poured in a suitable glassware and was kept in a shaking incubator for 48 h. 10 ml of this medium was then added into the flask and it was properly covered with aluminum foil. then it was placed in the incubator at 30oc for 24 h, 48 h, 72 h and 96 h for fermentation of sugars to bio-ethanol according to sujan et al. (2018). samples from hydrolysis and fermentation were performed by hplc. high performance liquid chromatography (hplc) in characterize part, concentration of sugars and ethanol were determined by hplc (ultimate 3000, thermo scientific, usa) method using hyper rez xp carbohydrate h+ 8 µm column (100×7.7 mm) equipped with a refractive index (shodex ri-101) detector. the mobile phase was degassed with deionized water with a flow rate of 0.7 ml/min and column temperature was maintained at 70°c. it is possible to measure the total sugar concentration in the hydrolysis liquid fraction by comparing its peak area detected by hplc with peak area of 1% standard sugar which consists of two sugars namely glucose and xylose (sujan et al. 2018). the same column which is specialized for fermentation broth analysis is used for ethanol detection. the kinetic parameters of ethanol fermentation were determined as follows (islam et al. 2019): crystallinity measurement x-ray diffraction (xrd) was used to determine the crystalline structure of the sb samples using a diffractometer (gbc xrd) and filtered copper k radiation (λ = 0.1542 nm) by a monochromator at 35.50 kv voltage and 28 ma current, with a speed of about 2o/min and scanning in the range of 10 80ºc. the crystallinity index (cri) was obtained from the ratio between the intensity of the 002 peak (i002, 2θ = 22.5) and the minimum dip (iam, 2 θ = 18.5) according to the following equation (roberta et al., 2012): cri (%) = [(i002 iam)/i002] ×100 ...................................... (2) where i002 is the highest peak intensity of plane 002 and iam is related to the amorphous structure. in present study, the average crystallite sizes were determined from the scherrer equation by using the diffraction pattern obtained from the 002 (hkl) lattice planes of cellulose samples d(hkl) = [(kλ / b(hkl) cos2θ] ............................................... (3) where d(hkl) (crystallite size), k (scherrer constant, 0.84), λ (x-ray wavelength, 0.154nm), b(hkl)(full width half maximum of the measured hkl reflection), and 2θ (corresponding bragg angle). scanning electron microscopy (sem) analysis in this research, sem (zeiss evo 18 sem) was used to detect the change of pretreated bagasse fibers. sem images were taken of different pretreated bagasse samples with acceleration voltage of 2.0 kv. results and discussion proximate analysis proximate analysis of sb sample (20-40 mesh) are presented in table i. primarily this analysis usually evaluate the fuel characteristics of raw materials. according to sun et al., 2009, higher moisture and ashcontent in samples lessen the heating value. ultimate analysis ultimate analysis denotes the elemental configuration of sb such as carbon, hydrogen, oxygen, nitrogen and sulfur which are shown in table ii. this examination helps to measure the percentage of carbon and hydrogen content in biomass that is responsible to determine the amount of air is required for complete combustion, composition of combustion gases and heat is generated by it (poddar et al. 2014). chemical properties raw sb contained 34.66±12% α-cellulose, 22.43±08% pentosan and 19.57±06% klason lignin in which 1.75±04% acid soluble lignin (dry basis) was detected by technical association of the pulp and paper industry (tappi) method. the chemical composition of sb was determined by acid hydrolysis and it was calculatedby hplc method as 45.35% glucose and 30.64% xylose (sujan et al., 2018). α-cellulose yield bagasse is mainly composed of cellulose, hemicellulose and lignin. besides these there are some extractives such as ash, wax, gum, pectin etc. during alkali pretreatment usually most of the extractives are removed with the increasing of alkali concentration. pretreatment of sb with different alkali concentration based on raw material (0%, 2%, 4%, 6% and 8%), time (60, 90 and 120 min) and temperature (80, 100 and 120oc) are shown in table iii. consequences of each independent experiment varying with alkali concentration, temperature and time on the α-cellulose yield were analyzed using matlab software. apparently, it was observed that α-cellulose yield was considerably increased with changes of alkali concentration ranging from 0% to 8% (34.66% to 63.58%). but no noticeable variation was observed in temperature-time alteration during pretreatment of sb. based on cellulose percentage obtained in treated bagasse, the optimum conditions for pretreatment reaction were selected as alkali concentration 8%, time 90 min and temperature 100oc. although cellulose content in treated sb was slowly increased with the increase of alkali concentration 12% attime 90 min and temperature 100oc but as a consequence of huge chemical consumption, recovery problem, chance of losses cellulose and hemicellulose, alkali concentrations for pretreatment above 8% was not considered as ideal concentration. effect of alkali concentration (ac), cooking time and temperature (temp) charge on α-cellulose yield as well as their statistical significance on the basis of f-test number are presented in regression equations (4). as shown in equations, cooking time at the maximum temperature had no significant effect on α-cellulose yield followed by alkali concentration charge. effect of temperature on α-cellulose yield was less in employed cooking conditions. for α-cellulose yield: α-cellulose yield = 82.05-0.151×temp-1.56×time-0.69×ac (r2=0.89, adjusted r2=0.87) ............................................. (4) for pentosan: pentosan = 13.58+0.086 × tem p + 0.006 × time+0.445 × ac (r2=0.67, adjusted r2=0.63) ............................................. (5) for lignin: lignin = 27.662-0.041×temp-0.001×time-01.242×ac (r2=0.93, adjusted r2=0.92) ............................................. (6) for predicting α-cellulose, percentage of pentosan and lignin, the most influential factor was alkali concentration and then cooking temperature for α-cellulose yield, which exhibited an almost linear dependence on both operational variables. the coefficient of determinations is good for α-cellulose yield and lignin percentage which hovers around 90 percent, although the figure is moderate more than 60 percent for pentosan. all these three models are significant (p<0.05) at 5% level of significance. in order to perceive the impact of alkali concentration and temperature on these three parameters, three-dimensional (3d) response surface plots were created by plotting the response (α-cellulose yield) pentosan and lignin on the z-axis versus the most influential one independent variable alkali concentration and temperature as shown in fig. 3 (a), (b) and (c). xrd analysis in 19th century the cellulose crystalline structure has been discovered and later it was verified by x-ray crystallography (meyer and misch, 1937; wilkie, 1961). the crystallinity index (cri) of non-woody biomass, such as grasses and agricultural residues, varies depending on the type of biomass. generally, non-woody biomass has a lower crystallinity index than woody biomass, typically ranging from 20-40%. the crystallinity index of non-woody biomass affects its digestibility and energy production potential.recently, researchers are being paid more attention on cellulose index because of its potential use in bioenergy production. since then several different models of cellulose index have been proposed. the most popular two-phase cellulose model describes cellulose chains as containing both crystalline (ordered) and amorphous (less ordered) region (park et al., 2010). alkali treatment of bagasse has been found to increase the crystallinity index of the bagasse. alkali treatment breaks down hemicellulose, making the cellulose molecules more ordered and crystalline, resulting in a higher crystallinity index. alkali treatment also increases the digestibility of the bagasse, making it easier to break down and therefore more suitable for bioenergy production. x-ray diffraction spectra of the sb and alkali treated sb were presented in figure 4. it was observed that the intensity of 101 and 002 peaks were gradually increased. the relative amount of crystalline cellulose (cri) in the total solid were calculated based on the equation (2) and obtained 18.68%, 24.80%, 27.23%, 32.69%, 36.45% and 39.19% for raw sb, 0%, 2%, 4%, 6% and 8% alkali treated sb samples respectively. the cri of alkali treated sb samples (not cellulose crystallinity) were intensely influenced by the composition of the samples. in case of lignocellulosic biomass examples, cellulose cri measured the relative amount of crystalline cellulose in the total solid. therefore, amorphous part of lignin and hemicellulose in biomass specimens were partially removed with the delignification process as a result the proportion of α-cellulose was increased and hence cri would be increased gradually. this interpretation could be proved by the fact that alkali-treated sb had higher cri than raw sb (zhao et al. 2010) and the portion of cellulose in the treated sb was also increased gradually. according to the equation 3, the average sizes of crystallite obtained were 3.28, 3.51, 3.63, 3.78, 3.90 and 4.06 nm for raw sb, 0%, 2%, 4%, 6% and 8% alkali treated sb samples respectively. the experimental data revealed that during delignification, the size of crystallite was increased. sem analysis sem is one of the most commanding tools widely used to investigate the lignocellulosic biomass surface (amiri and karimi, 2015). sem is usually employed for surface characterization, morphology and inspection of microstructure. in respect of biomass example through sem images we can compare the untreated and pretreated models which may lead to different insight into the biomass (karimi and taherzadeh, 2016). sem provides two-dimensional images of raw sb and alkali treated sb, which were taken and compared to the outcome of naoh treatment. all testers were coated with carbon tape and magnification of 500x was used. figure 4 shows the wall of raw sb (figure 6a) was intact where the alkali treated sb (figures 6c-6f), the cell wall was ruptured or splitted and hence packing of the fibers were partially loosened (firoz et al. 2012). sugar and ethanol yield enzymatic digestibility is the ability of enzymes to break down molecules into smaller molecules, such as glucose. it is used to measure the efficiency of enzyme-catalyzed reactions and the digestibility of cellulose. the enzymatic digestibility of a compound is affected by factors such as the compound's crystallinity index, the type of enzyme used, and the temperature and ph of the reaction. in this study the enzymatic digestibility of the alkali pretreated sb was improved by increasing pretreatment conditions. typically the pretreatment settings are selected by considering various factors such as feedstock characteristics, pretreatment chemical cost, energy consumption and recovery efficiency (wu et al. 2011). α-cellulose obtained by 8% alkali treated of sb was used for hydrolysis reaction and the reaction was carried out at an optimum condition set by sujan et al. (2018). the most effective enzymatic hydrolysis was taken place with trichoderma virideat 48 h and the theoretical yield of sugars i.e. glucose and xylose were obtained 89.59% and 61.23%, respectively. through fermentation process generated sugars were used to check ethanol production. yeast saccharomyces cerevisiae presented worthy performance to convert c6 sugar into ethanol when it was incubated at 30°c for 24 h and 16.81±0.32% ethanol yield was detected. conclusion α-cellulose yield was optimized by varying alkali concentration, temperature and cooking time. the most vital influencing factor for α-cellulose yield was alkali concentration and after that temperature performed a little bit. the optimum α-cellulose yield (63.58±0.05%) was obtained at 8% alkali concentration, 100oc and 90 minutes. in hydrolysis step of sb, trichoderma viridaewas used to convert 8% alkali treated sb into sugars and it was attained 89.59% glucose and 61.23% xylose which gave higher yield in compare with our previous study such as ball milled and mesh size varied sb sample (sujan et al. 2018). at fermentation step saccharomyces cerevisiae was used to convert hydrolysate of 8% alkali treated sb sample and ethanol yield was obtained 16.81±0.32% at 24 h. compositional analysis, imaging and crystallinity are three methods were performed. sem images can give different clues about sb including morphology, surface disruption and creation of highly accessible surface area iii) cri (18.68% to 39.19%) and crystal size (3.28 nm to 4.06 nm) of sb are increased with different alkali treatment (0%-8%). in this case it was observed that crystallinity, crystal size, accessible surface area, porosity, particle size, lignin and hemicellulose content and enzyme adsorption/desorption were acted as the most impressive factors for digestibility of sugarcane bagasse. acknowledgement authors would like to acknowledge pulp and paper division, bcsir for their cooperation. authors also like to thanks for the sincere assistance of md. abdul hamid, junior technician, ifrd, bcsir. references alvira p, tomás-pejó e, ballesteros m and negro mj (2010), pretreatment technologies for an efficient bioethanol production process based on enzymatic hydrolysis: a review, bioresource technology 101(13): 4851-4861. doi: org/10.1016/j.biortech.2009.11.093 agbor vb, cicek n, sparling r, berlin a and levin, db (2011), biomass pretreatment: fundamentals toward application, biotechnology advances 29(6): 675-685. doi: org/10.1016/j.biotechadv.2011.05.005 amiri h and karimi k (2015), improvement of acetone, butanol, and ethanol production from woody biomass using organosolv pretreatment, bioprocess and biosystems engineering 38(10): 1959-1972. astm (2007), standard test members for instrumental determination of c, h, n in petroleum products and lubricants. astm d5291-02, astm international, west conshohocken, pa. canilha l, chandel ak, suzane dos santos milessi t, antunes faf, luiz da costa freitas w, das graças almeida felipe m and da silva ss (2012), bioconversion of sugarcane biomass into ethanol: an overview about composition, pretreatment methods, detoxification of hydrolysates, enzymatic saccharification and ethanol fermentation. journal of biomedicine and biotechnology, doi: org/10.1155/2012/989572 den w, sharma vk, lee m, nadadur g and varma rs (2018), lignocellulosic biomass transformations via greener oxidative pretreatment processes: access to energy and value-added chemicals, frontiers in chemistry 6: 141. doi: org/10.3389/fchem.2018.00141 ahmed fm, rahman sr and gomes dj (2012), saccharification of sugarcane bagasse by enzymatic treatment for bioethanol production, malays j microbiol 8(2), 97-103. hirani ah, javed n, asif m, basu sk and kumar a (2018), a review on first-and second-generation biofuel productions. in biofuels: greenhouse gas mitigation and global warming, springer, new delhi, pp 141-154. doi: 10.1007/978-81-322-3763-1_8 islam mz, asad ma, hossain mt, paul sc and sujan sma (2019), bioethanol production from banana pseudostem by using separate and cocultures of cellulase enzyme with saccharomyces cerevisiae, journal of environmental science and technology 12(4): 157-163. jahan ms, saeed a, ni y and he z (2009), pre-extraction and its impact on the alkaline pulping of bagasse, journal of biobased materials and bioenergy 3(4): 380-385. doi: org/10.1166/jbmb.2009.1053 janker-obermeier i, sieber v, faulstich mand schieder d (2012), solubilization of hemicellulose and lignin from wheat straw through microwave-assisted alkali treatment, industrial crops and products 39: 198-203. doi: org/10.1016/j.indcrop.2012.02.022 karimi k and taherzadeh mj (2016), a critical review of analytical methods in pretreatment of lignocelluloses: composition, imaging, and crystallinity, bioresource technology 200: 1008-1018. doi: org/10.1016/j. biortech.2015.11.022 maryana r, ma’rifatun d, wheni ai, satriyo kw and rizal wa (2014), alkaline pretreatment on sugarcane bagasse for bioethanol production, energy procedia, 47: 250-254. doi: org/10.1016/j.egypro.2014.01.221 mcintosh sand vancov t (2010), enhanced enzyme saccharification of sorghum bicolor straw using dilute alkali pretreatment, bioresource technology 101(17): 6718-6727. doi: org/10.1016/j.biortech.2010.03.116 meyer kh and misch l (1937), positions des atomes dans le nouveau modele spatial de la cellulose. helvetica chimica acta 20(1): 232-244. doi: org/10. 1002/hlca.19370200134 park s, baker jo, himmel me, parilla pa and johnson dk (2010), cellulose crystallinity index: measurement techniques and their impact on interpreting cellulase performance, biotechnology for biofuels 3(1): 10. sujan sma, bari ml and fakhruddin an (2018), effects of physical pretreatment (crushing and ball milling) on sugarcane bagasse for bioethanol production, bangladesh journal of botany 147(2): 257-64. wilkie js (1961), carl nägeli and the fine structure of living matter, nature 190: 1145-1150. wu l, arakane m, ike m, wada m, takai t, gau mand tokuyasu k (2011), low temperature alkali pretreatment for improving enzymatic digestibility of sweet sorghum bagasse for ethanol production, bioresource technology 102(7): 4793-4799. zhang w, okubayashi s and bechtold t (2005), fibrillation tendency of cellulosic fibers-part 4. effects of alkali pretreatment of various cellulosic fibers, carbohydrate polymers. 61(4): 427-433. zhao x, van der heide e, zhang tand liu d (2010), delignification of sugarcane bagasse with alkali and peracetic acid and characterization of the pulp, bioresources 5(3): 1565-1580. zhao x, zhang land liu d (2012), biomass recalcitrance. part ii: fundamentals of different pre‐treatments to increase the enzymatic digestibility of lignocellulose, biofuels, bioproducts and biorefining 6(5): 561-579. fig. 4. xrd spectra of a) 20-40 mesh size sb; b) 0% alkali treated sample; c) 2% alkali treated sample; d) 4% alkali treated sample; e) 6% alkali treated sample; f) 8% alkali treated sample 002 101 a b c d e f fig. 5. average size of crystalline for raw sb, 0, 2, 4, 6 and 8% alkali treated sample optimization of alkali concentration in the pretreatment of sugarcane bagasse96 58(2) 2023 composed of vasculer bundles surrounded by non-fibrous parenchymatic cell (jahan et al. 2009). usually it is available as agricultural residue and byproduct from sugar mill industries. in the year of 2015-16, there was 2,95,162 metric ton sugarcane bagasse was obtained from sugar mills of bangladesh (http://www.bsfic.gov.bd). to enrich cellulose content in biomass for enzymatic saccarification, current research has focused on various pretreatment processes. currently, scientists have gone through a lot of studies on different pretreatment techniques to remove the compact and rigid composition by open up the cellulosic structure (alvira et al. 2010). pretreatment technologies are commonly abandoned to reduce the structural barriers and boost cellulose availability based on not only chemicals such as acid, alkali, oxidant, etc. but also several treatment settings. alkali treatment is one of the most widespread and economical methods used for surface modification of lignocellulosic biomass. in the field of biorefinary, alkali pretreatment is intensively employed to develop the cellulosic materials both mechanically as well as chemically and such properties include tensile strength, dyeability, stability of dimension and reactivity (wu et al. 2011). in alkali pretreatment biomass is treated under moderate reaction conditions ensuring inexpensiveness, inflated recycling possibilities of water and chemical agents (mcintosh and vancov, 2010). usually alkali treatment is the most effective pretreatment for agricultural residues, herbaceous crops and hardwood containing low lignin content in the compariosn of softwood containing high lignin content (agbor et al. 2011; canilha et al. 2012). this research aims is to investigate the alkaline pretreatment repercussions based on the chemical structure, surface morphology, structure and enzymatic digestion of sugarcane bagasse for sugars and ethanol production. materials and methods sugarcane bagasse (sb) was taken from street juice vendor. warm tap water was used for washing purpose to eliminate the residual free sugars once again. this washing and pressing step was then repeated for three times. after that drying was done in an oven at 65oc for 16 h. crushing of dried bagasse was done successively using a locally made crusher and sieved (retsch, d-42759, haan, germany) to have the particle size of 20-40 mesh on average. before usage, the 20-40 mesh bagasse was kept at room temperature in an airtight plastic container (sujan et al. 2018). moisture and ash content moisture content of raw materials was measured using the astm d 4442-07 procedure. in a glass crucible, 2 grams of pretreatment sample containing 20-40 mesh were dried in oven at 105±2°c. the moisture content was expressed in percent wet basis and weight measurements were taken every 3 h. a muffle furnace was used for burning the oven-dried samples at 575±25°c for ash content determination following the astm standard e 1755-01. volatile matter the volatile matter analysis was carried out in accordance with astm standard d 271-48. four grams of raw materials were heated in a furnace at 950±20°c for seven minutes. the weight loss, excluding the weight of moisture pushed off at 105°c, is then used to calculate volatile matter. fixed carbon the difference between 100 and the total of volatile matter, moisture, and ash content was used to compute the fixed carbon percentage. chemical analysis the technical association of the pulp and paper industry (tappi) method detects α-cellulose (t 203 cm-99), pentosan (t 223 cm-01), klason lignin (t211 om-83), and acid soluble lignin (t um 250) on a dry basis. ultimate analysis ultimate analysis of samples was done by following the procedure astm standard d 5291-02. organic elemental analyzer (flash 2000, thermo scientific, usa) was used with a specific condition (reactor temp. 900°c, he: 250 kpa, o2: 250 kpa, tcd). low concentration alkali pretreatment different alkali concentration (0%, 2%, 4%, 6% and 8%), time (60, 90 and 120 min) and temperature (80, 100 and 120oc) were applied on raw material to check alkali effect on sb shown in table 3. a portion of the ground bagasse 20-40 mesh (10g) was taken into plastic zipper bag (temperature 80oc, figure 2a and 2b) and stainless-steel reactor (temperature 100oc and 120oc, figure 2c and 2d). different alkali concentration was applied during the pretreatment process (alkali to sb ratio ranging between 1:12). the mixture was heated at a particular temperature such as in a water bath (80oc) and oil bath (100oc and 120oc) for a desired length of time. in the course of pretreatment process the sample was manually mixed 2-3 times to attain proper alkali treatment. the treated sb was placed into a polyester bag to remove excess alkali water by pressing it. after that it was vigorously washed with tap water (repeated for five times) to remove the remaining alkali. finally the sb was dried in an oven at 65oc for 72 h and stored in a close container at room temperature for further experiment. regression model regression model has been developed for prediction of α-cellulose, pentosan and lignin in sb. the general form of the model is: y=α+α1x1 + α2x2+........................+αnxn + ε.......................(1) where α is the constant term. αi are the coefficient of variables xi. ε is the random error term which is minimized with simple least squares regression (slsr). regression coefficients of the independent variables namely alkali concentration, temperature and time are estimated by slsr method for developing regression model to predict α-cellulose, pentosan and lignin. efficiencies of these models are expressed by coefficient of multiple determination (r2) and adjusted r2. 2.9 separate hydrolysis and fermentation (shf) the hydrolysis experiment took place in 100 ml conical flux 10ml enzyme solution with 200 mg (2% dry wt.) in citrate buffer (0.05 m, ph 5.0) at 50°c for 48 h. in this case trichoderma viride was used for hydrolysis. hydrolysate was then heated for 15 min in a boiling water bath and centrifugation was done to remove solid particles. the supernatant was used for analysis of released sugars as described by jamal et al. (2011). during fermentation process according to firoz et al. (2012), 100 ml media was prepared and 0.5 g of commercial yeast saccharomyces cerevisiae was used as inoculum which showed good performance to converts sugar into bioethanol. this inoculated media mixture was poured in a suitable glassware and was kept in a shaking incubator for 48 h. 10 ml of this medium was then added into the flask and it was properly covered with aluminum foil. then it was placed in the incubator at 30oc for 24 h, 48 h, 72 h and 96 h for fermentation of sugars to bio-ethanol according to sujan et al. (2018). samples from hydrolysis and fermentation were performed by hplc. high performance liquid chromatography (hplc) in characterize part, concentration of sugars and ethanol were determined by hplc (ultimate 3000, thermo scientific, usa) method using hyper rez xp carbohydrate h+ 8 µm column (100×7.7 mm) equipped with a refractive index (shodex ri-101) detector. the mobile phase was degassed with deionized water with a flow rate of 0.7 ml/min and column temperature was maintained at 70°c. it is possible to measure the total sugar concentration in the hydrolysis liquid fraction by comparing its peak area detected by hplc with peak area of 1% standard sugar which consists of two sugars namely glucose and xylose (sujan et al. 2018). the same column which is specialized for fermentation broth analysis is used for ethanol detection. the kinetic parameters of ethanol fermentation were determined as follows (islam et al. 2019): crystallinity measurement x-ray diffraction (xrd) was used to determine the crystalline structure of the sb samples using a diffractometer (gbc xrd) and filtered copper k radiation (λ = 0.1542 nm) by a monochromator at 35.50 kv voltage and 28 ma current, with a speed of about 2o/min and scanning in the range of 10 80ºc. the crystallinity index (cri) was obtained from the ratio between the intensity of the 002 peak (i002, 2θ = 22.5) and the minimum dip (iam, 2 θ = 18.5) according to the following equation (roberta et al., 2012): cri (%) = [(i002 iam)/i002] ×100 ...................................... (2) where i002 is the highest peak intensity of plane 002 and iam is related to the amorphous structure. in present study, the average crystallite sizes were determined from the scherrer equation by using the diffraction pattern obtained from the 002 (hkl) lattice planes of cellulose samples d(hkl) = [(kλ / b(hkl) cos2θ] ............................................... (3) where d(hkl) (crystallite size), k (scherrer constant, 0.84), λ (x-ray wavelength, 0.154nm), b(hkl)(full width half maximum of the measured hkl reflection), and 2θ (corresponding bragg angle). scanning electron microscopy (sem) analysis in this research, sem (zeiss evo 18 sem) was used to detect the change of pretreated bagasse fibers. sem images were taken of different pretreated bagasse samples with acceleration voltage of 2.0 kv. results and discussion proximate analysis proximate analysis of sb sample (20-40 mesh) are presented in table i. primarily this analysis usually evaluate the fuel characteristics of raw materials. according to sun et al., 2009, higher moisture and ashcontent in samples lessen the heating value. ultimate analysis ultimate analysis denotes the elemental configuration of sb such as carbon, hydrogen, oxygen, nitrogen and sulfur which are shown in table ii. this examination helps to measure the percentage of carbon and hydrogen content in biomass that is responsible to determine the amount of air is required for complete combustion, composition of combustion gases and heat is generated by it (poddar et al. 2014). chemical properties raw sb contained 34.66±12% α-cellulose, 22.43±08% pentosan and 19.57±06% klason lignin in which 1.75±04% acid soluble lignin (dry basis) was detected by technical association of the pulp and paper industry (tappi) method. the chemical composition of sb was determined by acid hydrolysis and it was calculatedby hplc method as 45.35% glucose and 30.64% xylose (sujan et al., 2018). α-cellulose yield bagasse is mainly composed of cellulose, hemicellulose and lignin. besides these there are some extractives such as ash, wax, gum, pectin etc. during alkali pretreatment usually most of the extractives are removed with the increasing of alkali concentration. pretreatment of sb with different alkali concentration based on raw material (0%, 2%, 4%, 6% and 8%), time (60, 90 and 120 min) and temperature (80, 100 and 120oc) are shown in table iii. consequences of each independent experiment varying with alkali concentration, temperature and time on the α-cellulose yield were analyzed using matlab software. apparently, it was observed that α-cellulose yield was considerably increased with changes of alkali concentration ranging from 0% to 8% (34.66% to 63.58%). but no noticeable variation was observed in temperature-time alteration during pretreatment of sb. based on cellulose percentage obtained in treated bagasse, the optimum conditions for pretreatment reaction were selected as alkali concentration 8%, time 90 min and temperature 100oc. although cellulose content in treated sb was slowly increased with the increase of alkali concentration 12% attime 90 min and temperature 100oc but as a consequence of huge chemical consumption, recovery problem, chance of losses cellulose and hemicellulose, alkali concentrations for pretreatment above 8% was not considered as ideal concentration. effect of alkali concentration (ac), cooking time and temperature (temp) charge on α-cellulose yield as well as their statistical significance on the basis of f-test number are presented in regression equations (4). as shown in equations, cooking time at the maximum temperature had no significant effect on α-cellulose yield followed by alkali concentration charge. effect of temperature on α-cellulose yield was less in employed cooking conditions. for α-cellulose yield: α-cellulose yield = 82.05-0.151×temp-1.56×time-0.69×ac (r2=0.89, adjusted r2=0.87) ............................................. (4) for pentosan: pentosan = 13.58+0.086 × tem p + 0.006 × time+0.445 × ac (r2=0.67, adjusted r2=0.63) ............................................. (5) for lignin: lignin = 27.662-0.041×temp-0.001×time-01.242×ac (r2=0.93, adjusted r2=0.92) ............................................. (6) for predicting α-cellulose, percentage of pentosan and lignin, the most influential factor was alkali concentration and then cooking temperature for α-cellulose yield, which exhibited an almost linear dependence on both operational variables. the coefficient of determinations is good for α-cellulose yield and lignin percentage which hovers around 90 percent, although the figure is moderate more than 60 percent for pentosan. all these three models are significant (p<0.05) at 5% level of significance. in order to perceive the impact of alkali concentration and temperature on these three parameters, three-dimensional (3d) response surface plots were created by plotting the response (α-cellulose yield) pentosan and lignin on the z-axis versus the most influential one independent variable alkali concentration and temperature as shown in fig. 3 (a), (b) and (c). xrd analysis in 19th century the cellulose crystalline structure has been discovered and later it was verified by x-ray crystallography (meyer and misch, 1937; wilkie, 1961). the crystallinity index (cri) of non-woody biomass, such as grasses and agricultural residues, varies depending on the type of biomass. generally, non-woody biomass has a lower crystallinity index than woody biomass, typically ranging from 20-40%. the crystallinity index of non-woody biomass affects its digestibility and energy production potential.recently, researchers are being paid more attention on cellulose index because of its potential use in bioenergy production. since then several different models of cellulose index have been proposed. the most popular two-phase cellulose model describes cellulose chains as containing both crystalline (ordered) and amorphous (less ordered) region (park et al., 2010). alkali treatment of bagasse has been found to increase the crystallinity index of the bagasse. alkali treatment breaks down hemicellulose, making the cellulose molecules more ordered and crystalline, resulting in a higher crystallinity index. alkali treatment also increases the digestibility of the bagasse, making it easier to break down and therefore more suitable for bioenergy production. x-ray diffraction spectra of the sb and alkali treated sb were presented in figure 4. it was observed that the intensity of 101 and 002 peaks were gradually increased. the relative amount of crystalline cellulose (cri) in the total solid were calculated based on the equation (2) and obtained 18.68%, 24.80%, 27.23%, 32.69%, 36.45% and 39.19% for raw sb, 0%, 2%, 4%, 6% and 8% alkali treated sb samples respectively. the cri of alkali treated sb samples (not cellulose crystallinity) were intensely influenced by the composition of the samples. in case of lignocellulosic biomass examples, cellulose cri measured the relative amount of crystalline cellulose in the total solid. therefore, amorphous part of lignin and hemicellulose in biomass specimens were partially removed with the delignification process as a result the proportion of α-cellulose was increased and hence cri would be increased gradually. this interpretation could be proved by the fact that alkali-treated sb had higher cri than raw sb (zhao et al. 2010) and the portion of cellulose in the treated sb was also increased gradually. according to the equation 3, the average sizes of crystallite obtained were 3.28, 3.51, 3.63, 3.78, 3.90 and 4.06 nm for raw sb, 0%, 2%, 4%, 6% and 8% alkali treated sb samples respectively. the experimental data revealed that during delignification, the size of crystallite was increased. sem analysis sem is one of the most commanding tools widely used to investigate the lignocellulosic biomass surface (amiri and karimi, 2015). sem is usually employed for surface characterization, morphology and inspection of microstructure. in respect of biomass example through sem images we can compare the untreated and pretreated models which may lead to different insight into the biomass (karimi and taherzadeh, 2016). sem provides two-dimensional images of raw sb and alkali treated sb, which were taken and compared to the outcome of naoh treatment. all testers were coated with carbon tape and magnification of 500x was used. figure 4 shows the wall of raw sb (figure 6a) was intact where the alkali treated sb (figures 6c-6f), the cell wall was ruptured or splitted and hence packing of the fibers were partially loosened (firoz et al. 2012). sugar and ethanol yield enzymatic digestibility is the ability of enzymes to break down molecules into smaller molecules, such as glucose. it is used to measure the efficiency of enzyme-catalyzed reactions and the digestibility of cellulose. the enzymatic digestibility of a compound is affected by factors such as the compound's crystallinity index, the type of enzyme used, and the temperature and ph of the reaction. in this study the enzymatic digestibility of the alkali pretreated sb was improved by increasing pretreatment conditions. typically the pretreatment settings are selected by considering various factors such as feedstock characteristics, pretreatment chemical cost, energy consumption and recovery efficiency (wu et al. 2011). α-cellulose obtained by 8% alkali treated of sb was used for hydrolysis reaction and the reaction was carried out at an optimum condition set by sujan et al. (2018). the most effective enzymatic hydrolysis was taken place with trichoderma virideat 48 h and the theoretical yield of sugars i.e. glucose and xylose were obtained 89.59% and 61.23%, respectively. through fermentation process generated sugars were used to check ethanol production. yeast saccharomyces cerevisiae presented worthy performance to convert c6 sugar into ethanol when it was incubated at 30°c for 24 h and 16.81±0.32% ethanol yield was detected. conclusion α-cellulose yield was optimized by varying alkali concentration, temperature and cooking time. the most vital influencing factor for α-cellulose yield was alkali concentration and after that temperature performed a little bit. the optimum α-cellulose yield (63.58±0.05%) was obtained at 8% alkali concentration, 100oc and 90 minutes. in hydrolysis step of sb, trichoderma viridaewas used to convert 8% alkali treated sb into sugars and it was attained 89.59% glucose and 61.23% xylose which gave higher yield in compare with our previous study such as ball milled and mesh size varied sb sample (sujan et al. 2018). at fermentation step saccharomyces cerevisiae was used to convert hydrolysate of 8% alkali treated sb sample and ethanol yield was obtained 16.81±0.32% at 24 h. compositional analysis, imaging and crystallinity are three methods were performed. sem images can give different clues about sb including morphology, surface disruption and creation of highly accessible surface area iii) cri (18.68% to 39.19%) and crystal size (3.28 nm to 4.06 nm) of sb are increased with different alkali treatment (0%-8%). in this case it was observed that crystallinity, crystal size, accessible surface area, porosity, particle size, lignin and hemicellulose content and enzyme adsorption/desorption were acted as the most impressive factors for digestibility of sugarcane bagasse. acknowledgement authors would like to acknowledge pulp and paper division, bcsir for their cooperation. authors also like to thanks for the sincere assistance of md. abdul hamid, junior technician, ifrd, bcsir. references alvira p, tomás-pejó e, ballesteros m and negro mj (2010), pretreatment technologies for an efficient bioethanol production process based on enzymatic hydrolysis: a review, bioresource technology 101(13): 4851-4861. doi: org/10.1016/j.biortech.2009.11.093 agbor vb, cicek n, sparling r, berlin a and levin, db (2011), biomass pretreatment: fundamentals toward application, biotechnology advances 29(6): 675-685. doi: org/10.1016/j.biotechadv.2011.05.005 amiri h and karimi k (2015), improvement of acetone, butanol, and ethanol production from woody biomass using organosolv pretreatment, bioprocess and biosystems engineering 38(10): 1959-1972. astm (2007), standard test members for instrumental determination of c, h, n in petroleum products and lubricants. astm d5291-02, astm international, west conshohocken, pa. canilha l, chandel ak, suzane dos santos milessi t, antunes faf, luiz da costa freitas w, das graças almeida felipe m and da silva ss (2012), bioconversion of sugarcane biomass into ethanol: an overview about composition, pretreatment methods, detoxification of hydrolysates, enzymatic saccharification and ethanol fermentation. journal of biomedicine and biotechnology, doi: org/10.1155/2012/989572 den w, sharma vk, lee m, nadadur g and varma rs (2018), lignocellulosic biomass transformations via greener oxidative pretreatment processes: access to energy and value-added chemicals, frontiers in chemistry 6: 141. doi: org/10.3389/fchem.2018.00141 ahmed fm, rahman sr and gomes dj (2012), saccharification of sugarcane bagasse by enzymatic treatment for bioethanol production, malays j microbiol 8(2), 97-103. hirani ah, javed n, asif m, basu sk and kumar a (2018), a review on first-and second-generation biofuel productions. in biofuels: greenhouse gas mitigation and global warming, springer, new delhi, pp 141-154. doi: 10.1007/978-81-322-3763-1_8 islam mz, asad ma, hossain mt, paul sc and sujan sma (2019), bioethanol production from banana pseudostem by using separate and cocultures of cellulase enzyme with saccharomyces cerevisiae, journal of environmental science and technology 12(4): 157-163. jahan ms, saeed a, ni y and he z (2009), pre-extraction and its impact on the alkaline pulping of bagasse, journal of biobased materials and bioenergy 3(4): 380-385. doi: org/10.1166/jbmb.2009.1053 janker-obermeier i, sieber v, faulstich mand schieder d (2012), solubilization of hemicellulose and lignin from wheat straw through microwave-assisted alkali treatment, industrial crops and products 39: 198-203. doi: org/10.1016/j.indcrop.2012.02.022 karimi k and taherzadeh mj (2016), a critical review of analytical methods in pretreatment of lignocelluloses: composition, imaging, and crystallinity, bioresource technology 200: 1008-1018. doi: org/10.1016/j. biortech.2015.11.022 maryana r, ma’rifatun d, wheni ai, satriyo kw and rizal wa (2014), alkaline pretreatment on sugarcane bagasse for bioethanol production, energy procedia, 47: 250-254. doi: org/10.1016/j.egypro.2014.01.221 mcintosh sand vancov t (2010), enhanced enzyme saccharification of sorghum bicolor straw using dilute alkali pretreatment, bioresource technology 101(17): 6718-6727. doi: org/10.1016/j.biortech.2010.03.116 meyer kh and misch l (1937), positions des atomes dans le nouveau modele spatial de la cellulose. helvetica chimica acta 20(1): 232-244. doi: org/10. 1002/hlca.19370200134 park s, baker jo, himmel me, parilla pa and johnson dk (2010), cellulose crystallinity index: measurement techniques and their impact on interpreting cellulase performance, biotechnology for biofuels 3(1): 10. sujan sma, bari ml and fakhruddin an (2018), effects of physical pretreatment (crushing and ball milling) on sugarcane bagasse for bioethanol production, bangladesh journal of botany 147(2): 257-64. wilkie js (1961), carl nägeli and the fine structure of living matter, nature 190: 1145-1150. wu l, arakane m, ike m, wada m, takai t, gau mand tokuyasu k (2011), low temperature alkali pretreatment for improving enzymatic digestibility of sweet sorghum bagasse for ethanol production, bioresource technology 102(7): 4793-4799. zhang w, okubayashi s and bechtold t (2005), fibrillation tendency of cellulosic fibers-part 4. effects of alkali pretreatment of various cellulosic fibers, carbohydrate polymers. 61(4): 427-433. zhao x, van der heide e, zhang tand liu d (2010), delignification of sugarcane bagasse with alkali and peracetic acid and characterization of the pulp, bioresources 5(3): 1565-1580. zhao x, zhang land liu d (2012), biomass recalcitrance. part ii: fundamentals of different pre‐treatments to increase the enzymatic digestibility of lignocellulose, biofuels, bioproducts and biorefining 6(5): 561-579. fig. 6(a-f). sem images a) 20-40 mesh size sb; b) 0% alkali treated sample; c) 2% alkali treated sample; d) 4% alkali treated sample; e) 6% alkali treated sample; f) 8% alkali treated sample 6a 6b 6c 6d 6e 6f ec: ethanol concentration table iv. the percentage of ethanol yield with different time of fermentation at 30oc time (h) 24 h 48 h 72 h 96 h ec (%) 16.81±0.32 13.25±0.16 12.12±0.20 10.41±0.23 composed of vasculer bundles surrounded by non-fibrous parenchymatic cell (jahan et al. 2009). usually it is available as agricultural residue and byproduct from sugar mill industries. in the year of 2015-16, there was 2,95,162 metric ton sugarcane bagasse was obtained from sugar mills of bangladesh (http://www.bsfic.gov.bd). to enrich cellulose content in biomass for enzymatic saccarification, current research has focused on various pretreatment processes. currently, scientists have gone through a lot of studies on different pretreatment techniques to remove the compact and rigid composition by open up the cellulosic structure (alvira et al. 2010). pretreatment technologies are commonly abandoned to reduce the structural barriers and boost cellulose availability based on not only chemicals such as acid, alkali, oxidant, etc. but also several treatment settings. alkali treatment is one of the most widespread and economical methods used for surface modification of lignocellulosic biomass. in the field of biorefinary, alkali pretreatment is intensively employed to develop the cellulosic materials both mechanically as well as chemically and such properties include tensile strength, dyeability, stability of dimension and reactivity (wu et al. 2011). in alkali pretreatment biomass is treated under moderate reaction conditions ensuring inexpensiveness, inflated recycling possibilities of water and chemical agents (mcintosh and vancov, 2010). usually alkali treatment is the most effective pretreatment for agricultural residues, herbaceous crops and hardwood containing low lignin content in the compariosn of softwood containing high lignin content (agbor et al. 2011; canilha et al. 2012). this research aims is to investigate the alkaline pretreatment repercussions based on the chemical structure, surface morphology, structure and enzymatic digestion of sugarcane bagasse for sugars and ethanol production. materials and methods sugarcane bagasse (sb) was taken from street juice vendor. warm tap water was used for washing purpose to eliminate the residual free sugars once again. this washing and pressing step was then repeated for three times. after that drying was done in an oven at 65oc for 16 h. crushing of dried bagasse was done successively using a locally made crusher and sieved (retsch, d-42759, haan, germany) to have the particle size of 20-40 mesh on average. before usage, the 20-40 mesh bagasse was kept at room temperature in an airtight plastic container (sujan et al. 2018). moisture and ash content moisture content of raw materials was measured using the astm d 4442-07 procedure. in a glass crucible, 2 grams of pretreatment sample containing 20-40 mesh were dried in oven at 105±2°c. the moisture content was expressed in percent wet basis and weight measurements were taken every 3 h. a muffle furnace was used for burning the oven-dried samples at 575±25°c for ash content determination following the astm standard e 1755-01. volatile matter the volatile matter analysis was carried out in accordance with astm standard d 271-48. four grams of raw materials were heated in a furnace at 950±20°c for seven minutes. the weight loss, excluding the weight of moisture pushed off at 105°c, is then used to calculate volatile matter. fixed carbon the difference between 100 and the total of volatile matter, moisture, and ash content was used to compute the fixed carbon percentage. chemical analysis the technical association of the pulp and paper industry (tappi) method detects α-cellulose (t 203 cm-99), pentosan (t 223 cm-01), klason lignin (t211 om-83), and acid soluble lignin (t um 250) on a dry basis. ultimate analysis ultimate analysis of samples was done by following the procedure astm standard d 5291-02. organic elemental analyzer (flash 2000, thermo scientific, usa) was used with a specific condition (reactor temp. 900°c, he: 250 kpa, o2: 250 kpa, tcd). low concentration alkali pretreatment different alkali concentration (0%, 2%, 4%, 6% and 8%), time (60, 90 and 120 min) and temperature (80, 100 and 120oc) were applied on raw material to check alkali effect on sb shown in table 3. a portion of the ground bagasse 20-40 mesh (10g) was taken into plastic zipper bag (temperature 80oc, figure 2a and 2b) and stainless-steel reactor (temperature 100oc and 120oc, figure 2c and 2d). different alkali concentration was applied during the pretreatment process (alkali to sb ratio ranging between 1:12). the mixture was heated at a particular temperature such as in a water bath (80oc) and oil bath (100oc and 120oc) for a desired length of time. in the course of pretreatment process the sample was manually mixed 2-3 times to attain proper alkali treatment. the treated sb was placed into a polyester bag to remove excess alkali water by pressing it. after that it was vigorously washed with tap water (repeated for five times) to remove the remaining alkali. finally the sb was dried in an oven at 65oc for 72 h and stored in a close container at room temperature for further experiment. regression model regression model has been developed for prediction of α-cellulose, pentosan and lignin in sb. the general form of the model is: y=α+α1x1 + α2x2+........................+αnxn + ε.......................(1) where α is the constant term. αi are the coefficient of variables xi. ε is the random error term which is minimized with simple least squares regression (slsr). regression coefficients of the independent variables namely alkali concentration, temperature and time are estimated by slsr method for developing regression model to predict α-cellulose, pentosan and lignin. efficiencies of these models are expressed by coefficient of multiple determination (r2) and adjusted r2. 2.9 separate hydrolysis and fermentation (shf) the hydrolysis experiment took place in 100 ml conical flux 10ml enzyme solution with 200 mg (2% dry wt.) in citrate buffer (0.05 m, ph 5.0) at 50°c for 48 h. in this case trichoderma viride was used for hydrolysis. hydrolysate was then heated for 15 min in a boiling water bath and centrifugation was done to remove solid particles. the supernatant was used for analysis of released sugars as described by jamal et al. (2011). during fermentation process according to firoz et al. (2012), 100 ml media was prepared and 0.5 g of commercial yeast saccharomyces cerevisiae was used as inoculum which showed good performance to converts sugar into bioethanol. this inoculated media mixture was poured in a suitable glassware and was kept in a shaking incubator for 48 h. 10 ml of this medium was then added into the flask and it was properly covered with aluminum foil. then it was placed in the incubator at 30oc for 24 h, 48 h, 72 h and 96 h for fermentation of sugars to bio-ethanol according to sujan et al. (2018). samples from hydrolysis and fermentation were performed by hplc. high performance liquid chromatography (hplc) in characterize part, concentration of sugars and ethanol were determined by hplc (ultimate 3000, thermo scientific, usa) method using hyper rez xp carbohydrate h+ 8 µm column (100×7.7 mm) equipped with a refractive index (shodex ri-101) detector. the mobile phase was degassed with deionized water with a flow rate of 0.7 ml/min and column temperature was maintained at 70°c. it is possible to measure the total sugar concentration in the hydrolysis liquid fraction by comparing its peak area detected by hplc with peak area of 1% standard sugar which consists of two sugars namely glucose and xylose (sujan et al. 2018). the same column which is specialized for fermentation broth analysis is used for ethanol detection. the kinetic parameters of ethanol fermentation were determined as follows (islam et al. 2019): crystallinity measurement x-ray diffraction (xrd) was used to determine the crystalline structure of the sb samples using a diffractometer (gbc xrd) and filtered copper k radiation (λ = 0.1542 nm) by a monochromator at 35.50 kv voltage and 28 ma current, with a speed of about 2o/min and scanning in the range of 10 80ºc. the crystallinity index (cri) was obtained from the ratio between the intensity of the 002 peak (i002, 2θ = 22.5) and the minimum dip (iam, 2 θ = 18.5) according to the following equation (roberta et al., 2012): cri (%) = [(i002 iam)/i002] ×100 ...................................... (2) where i002 is the highest peak intensity of plane 002 and iam is related to the amorphous structure. in present study, the average crystallite sizes were determined from the scherrer equation by using the diffraction pattern obtained from the 002 (hkl) lattice planes of cellulose samples d(hkl) = [(kλ / b(hkl) cos2θ] ............................................... (3) where d(hkl) (crystallite size), k (scherrer constant, 0.84), λ (x-ray wavelength, 0.154nm), b(hkl)(full width half maximum of the measured hkl reflection), and 2θ (corresponding bragg angle). scanning electron microscopy (sem) analysis in this research, sem (zeiss evo 18 sem) was used to detect the change of pretreated bagasse fibers. sem images were taken of different pretreated bagasse samples with acceleration voltage of 2.0 kv. results and discussion proximate analysis proximate analysis of sb sample (20-40 mesh) are presented in table i. primarily this analysis usually evaluate the fuel characteristics of raw materials. according to sun et al., 2009, higher moisture and ashcontent in samples lessen the heating value. ultimate analysis ultimate analysis denotes the elemental configuration of sb such as carbon, hydrogen, oxygen, nitrogen and sulfur which are shown in table ii. this examination helps to measure the percentage of carbon and hydrogen content in biomass that is responsible to determine the amount of air is required for complete combustion, composition of combustion gases and heat is generated by it (poddar et al. 2014). chemical properties raw sb contained 34.66±12% α-cellulose, 22.43±08% pentosan and 19.57±06% klason lignin in which 1.75±04% acid soluble lignin (dry basis) was detected by technical association of the pulp and paper industry (tappi) method. the chemical composition of sb was determined by acid hydrolysis and it was calculatedby hplc method as 45.35% glucose and 30.64% xylose (sujan et al., 2018). α-cellulose yield bagasse is mainly composed of cellulose, hemicellulose and lignin. besides these there are some extractives such as ash, wax, gum, pectin etc. during alkali pretreatment usually most of the extractives are removed with the increasing of alkali concentration. pretreatment of sb with different alkali concentration based on raw material (0%, 2%, 4%, 6% and 8%), time (60, 90 and 120 min) and temperature (80, 100 and 120oc) are shown in table iii. consequences of each independent experiment varying with alkali concentration, temperature and time on the α-cellulose yield were analyzed using matlab software. apparently, it was observed that α-cellulose yield was considerably increased with changes of alkali concentration ranging from 0% to 8% (34.66% to 63.58%). but no noticeable variation was observed in temperature-time alteration during pretreatment of sb. based on cellulose percentage obtained in treated bagasse, the optimum conditions for pretreatment reaction were selected as alkali concentration 8%, time 90 min and temperature 100oc. although cellulose content in treated sb was slowly increased with the increase of alkali concentration 12% attime 90 min and temperature 100oc but as a consequence of huge chemical consumption, recovery problem, chance of losses cellulose and hemicellulose, alkali concentrations for pretreatment above 8% was not considered as ideal concentration. effect of alkali concentration (ac), cooking time and temperature (temp) charge on α-cellulose yield as well as their statistical significance on the basis of f-test number are presented in regression equations (4). as shown in equations, cooking time at the maximum temperature had no significant effect on α-cellulose yield followed by alkali concentration charge. effect of temperature on α-cellulose yield was less in employed cooking conditions. for α-cellulose yield: α-cellulose yield = 82.05-0.151×temp-1.56×time-0.69×ac (r2=0.89, adjusted r2=0.87) ............................................. (4) for pentosan: pentosan = 13.58+0.086 × tem p + 0.006 × time+0.445 × ac (r2=0.67, adjusted r2=0.63) ............................................. (5) for lignin: lignin = 27.662-0.041×temp-0.001×time-01.242×ac (r2=0.93, adjusted r2=0.92) ............................................. (6) for predicting α-cellulose, percentage of pentosan and lignin, the most influential factor was alkali concentration and then cooking temperature for α-cellulose yield, which exhibited an almost linear dependence on both operational variables. the coefficient of determinations is good for α-cellulose yield and lignin percentage which hovers around 90 percent, although the figure is moderate more than 60 percent for pentosan. all these three models are significant (p<0.05) at 5% level of significance. in order to perceive the impact of alkali concentration and temperature on these three parameters, three-dimensional (3d) response surface plots were created by plotting the response (α-cellulose yield) pentosan and lignin on the z-axis versus the most influential one independent variable alkali concentration and temperature as shown in fig. 3 (a), (b) and (c). xrd analysis in 19th century the cellulose crystalline structure has been discovered and later it was verified by x-ray crystallography (meyer and misch, 1937; wilkie, 1961). the crystallinity index (cri) of non-woody biomass, such as grasses and agricultural residues, varies depending on the type of biomass. generally, non-woody biomass has a lower crystallinity index than woody biomass, typically ranging from 20-40%. the crystallinity index of non-woody biomass affects its digestibility and energy production potential.recently, researchers are being paid more attention on cellulose index because of its potential use in bioenergy production. since then several different models of cellulose index have been proposed. the most popular two-phase cellulose model describes cellulose chains as containing both crystalline (ordered) and amorphous (less ordered) region (park et al., 2010). alkali treatment of bagasse has been found to increase the crystallinity index of the bagasse. alkali treatment breaks down hemicellulose, making the cellulose molecules more ordered and crystalline, resulting in a higher crystallinity index. alkali treatment also increases the digestibility of the bagasse, making it easier to break down and therefore more suitable for bioenergy production. x-ray diffraction spectra of the sb and alkali treated sb were presented in figure 4. it was observed that the intensity of 101 and 002 peaks were gradually increased. the relative amount of crystalline cellulose (cri) in the total solid were calculated based on the equation (2) and obtained 18.68%, 24.80%, 27.23%, 32.69%, 36.45% and 39.19% for raw sb, 0%, 2%, 4%, 6% and 8% alkali treated sb samples respectively. the cri of alkali treated sb samples (not cellulose crystallinity) were intensely influenced by the composition of the samples. in case of lignocellulosic biomass examples, cellulose cri measured the relative amount of crystalline cellulose in the total solid. therefore, amorphous part of lignin and hemicellulose in biomass specimens were partially removed with the delignification process as a result the proportion of α-cellulose was increased and hence cri would be increased gradually. this interpretation could be proved by the fact that alkali-treated sb had higher cri than raw sb (zhao et al. 2010) and the portion of cellulose in the treated sb was also increased gradually. according to the equation 3, the average sizes of crystallite obtained were 3.28, 3.51, 3.63, 3.78, 3.90 and 4.06 nm for raw sb, 0%, 2%, 4%, 6% and 8% alkali treated sb samples respectively. the experimental data revealed that during delignification, the size of crystallite was increased. sem analysis sem is one of the most commanding tools widely used to investigate the lignocellulosic biomass surface (amiri and karimi, 2015). sem is usually employed for surface characterization, morphology and inspection of microstructure. in respect of biomass example through sem images we can compare the untreated and pretreated models which may lead to different insight into the biomass (karimi and taherzadeh, 2016). sem provides two-dimensional images of raw sb and alkali treated sb, which were taken and compared to the outcome of naoh treatment. all testers were coated with carbon tape and magnification of 500x was used. figure 4 shows the wall of raw sb (figure 6a) was intact where the alkali treated sb (figures 6c-6f), the cell wall was ruptured or splitted and hence packing of the fibers were partially loosened (firoz et al. 2012). sugar and ethanol yield enzymatic digestibility is the ability of enzymes to break down molecules into smaller molecules, such as glucose. it is used to measure the efficiency of enzyme-catalyzed reactions and the digestibility of cellulose. the enzymatic digestibility of a compound is affected by factors such as the compound's crystallinity index, the type of enzyme used, and the temperature and ph of the reaction. in this study the enzymatic digestibility of the alkali pretreated sb was improved by increasing pretreatment conditions. typically the pretreatment settings are selected by considering various factors such as feedstock characteristics, pretreatment chemical cost, energy consumption and recovery efficiency (wu et al. 2011). α-cellulose obtained by 8% alkali treated of sb was used for hydrolysis reaction and the reaction was carried out at an optimum condition set by sujan et al. (2018). the most effective enzymatic hydrolysis was taken place with trichoderma virideat 48 h and the theoretical yield of sugars i.e. glucose and xylose were obtained 89.59% and 61.23%, respectively. through fermentation process generated sugars were used to check ethanol production. yeast saccharomyces cerevisiae presented worthy performance to convert c6 sugar into ethanol when it was incubated at 30°c for 24 h and 16.81±0.32% ethanol yield was detected. conclusion α-cellulose yield was optimized by varying alkali concentration, temperature and cooking time. the most vital influencing factor for α-cellulose yield was alkali concentration and after that temperature performed a little bit. the optimum α-cellulose yield (63.58±0.05%) was obtained at 8% alkali concentration, 100oc and 90 minutes. in hydrolysis step of sb, trichoderma viridaewas used to convert 8% alkali treated sb into sugars and it was attained 89.59% glucose and 61.23% xylose which gave higher yield in compare with our previous study such as ball milled and mesh size varied sb sample (sujan et al. 2018). at fermentation step saccharomyces cerevisiae was used to convert hydrolysate of 8% alkali treated sb sample and ethanol yield was obtained 16.81±0.32% at 24 h. compositional analysis, imaging and crystallinity are three methods were performed. sem images can give different clues about sb including morphology, surface disruption and creation of highly accessible surface area iii) cri (18.68% to 39.19%) and crystal size (3.28 nm to 4.06 nm) of sb are increased with different alkali treatment (0%-8%). in this case it was observed that crystallinity, crystal size, accessible surface area, porosity, particle size, lignin and hemicellulose content and enzyme adsorption/desorption were acted as the most impressive factors for digestibility of sugarcane bagasse. acknowledgement authors would like to acknowledge pulp and paper division, bcsir for their cooperation. authors also like to thanks for the sincere assistance of md. abdul hamid, junior technician, ifrd, bcsir. references alvira p, tomás-pejó e, ballesteros m and negro mj (2010), pretreatment technologies for an efficient bioethanol production process based on enzymatic hydrolysis: a review, bioresource technology 101(13): 4851-4861. doi: org/10.1016/j.biortech.2009.11.093 agbor vb, cicek n, sparling r, berlin a and levin, db (2011), biomass pretreatment: fundamentals toward application, biotechnology advances 29(6): 675-685. doi: org/10.1016/j.biotechadv.2011.05.005 amiri h and karimi k (2015), improvement of acetone, butanol, and ethanol production from woody biomass using organosolv pretreatment, bioprocess and biosystems engineering 38(10): 1959-1972. astm (2007), standard test members for instrumental determination of c, h, n in petroleum products and lubricants. astm d5291-02, astm international, west conshohocken, pa. canilha l, chandel ak, suzane dos santos milessi t, antunes faf, luiz da costa freitas w, das graças almeida felipe m and da silva ss (2012), bioconversion of sugarcane biomass into ethanol: an overview about composition, pretreatment methods, detoxification of hydrolysates, enzymatic saccharification and ethanol fermentation. journal of biomedicine and biotechnology, doi: org/10.1155/2012/989572 den w, sharma vk, lee m, nadadur g and varma rs (2018), lignocellulosic biomass transformations via greener oxidative pretreatment processes: access to energy and value-added chemicals, frontiers in chemistry 6: 141. doi: org/10.3389/fchem.2018.00141 ahmed fm, rahman sr and gomes dj (2012), saccharification of sugarcane bagasse by enzymatic treatment for bioethanol production, malays j microbiol 8(2), 97-103. hirani ah, javed n, asif m, basu sk and kumar a (2018), a review on first-and second-generation biofuel productions. in biofuels: greenhouse gas mitigation and global warming, springer, new delhi, pp 141-154. doi: 10.1007/978-81-322-3763-1_8 islam mz, asad ma, hossain mt, paul sc and sujan sma (2019), bioethanol production from banana pseudostem by using separate and cocultures of cellulase enzyme with saccharomyces cerevisiae, journal of environmental science and technology 12(4): 157-163. jahan ms, saeed a, ni y and he z (2009), pre-extraction and its impact on the alkaline pulping of bagasse, journal of biobased materials and bioenergy 3(4): 380-385. doi: org/10.1166/jbmb.2009.1053 janker-obermeier i, sieber v, faulstich mand schieder d (2012), solubilization of hemicellulose and lignin from wheat straw through microwave-assisted alkali treatment, industrial crops and products 39: 198-203. doi: org/10.1016/j.indcrop.2012.02.022 karimi k and taherzadeh mj (2016), a critical review of analytical methods in pretreatment of lignocelluloses: composition, imaging, and crystallinity, bioresource technology 200: 1008-1018. doi: org/10.1016/j. biortech.2015.11.022 maryana r, ma’rifatun d, wheni ai, satriyo kw and rizal wa (2014), alkaline pretreatment on sugarcane bagasse for bioethanol production, energy procedia, 47: 250-254. doi: org/10.1016/j.egypro.2014.01.221 mcintosh sand vancov t (2010), enhanced enzyme saccharification of sorghum bicolor straw using dilute alkali pretreatment, bioresource technology 101(17): 6718-6727. doi: org/10.1016/j.biortech.2010.03.116 meyer kh and misch l (1937), positions des atomes dans le nouveau modele spatial de la cellulose. helvetica chimica acta 20(1): 232-244. doi: org/10. 1002/hlca.19370200134 park s, baker jo, himmel me, parilla pa and johnson dk (2010), cellulose crystallinity index: measurement techniques and their impact on interpreting cellulase performance, biotechnology for biofuels 3(1): 10. sujan sma, bari ml and fakhruddin an (2018), effects of physical pretreatment (crushing and ball milling) on sugarcane bagasse for bioethanol production, bangladesh journal of botany 147(2): 257-64. wilkie js (1961), carl nägeli and the fine structure of living matter, nature 190: 1145-1150. wu l, arakane m, ike m, wada m, takai t, gau mand tokuyasu k (2011), low temperature alkali pretreatment for improving enzymatic digestibility of sweet sorghum bagasse for ethanol production, bioresource technology 102(7): 4793-4799. zhang w, okubayashi s and bechtold t (2005), fibrillation tendency of cellulosic fibers-part 4. effects of alkali pretreatment of various cellulosic fibers, carbohydrate polymers. 61(4): 427-433. zhao x, van der heide e, zhang tand liu d (2010), delignification of sugarcane bagasse with alkali and peracetic acid and characterization of the pulp, bioresources 5(3): 1565-1580. zhao x, zhang land liu d (2012), biomass recalcitrance. part ii: fundamentals of different pre‐treatments to increase the enzymatic digestibility of lignocellulose, biofuels, bioproducts and biorefining 6(5): 561-579. sujan, hossain, uddin and fakhruddin 97 composed of vasculer bundles surrounded by non-fibrous parenchymatic cell (jahan et al. 2009). usually it is available as agricultural residue and byproduct from sugar mill industries. in the year of 2015-16, there was 2,95,162 metric ton sugarcane bagasse was obtained from sugar mills of bangladesh (http://www.bsfic.gov.bd). to enrich cellulose content in biomass for enzymatic saccarification, current research has focused on various pretreatment processes. currently, scientists have gone through a lot of studies on different pretreatment techniques to remove the compact and rigid composition by open up the cellulosic structure (alvira et al. 2010). pretreatment technologies are commonly abandoned to reduce the structural barriers and boost cellulose availability based on not only chemicals such as acid, alkali, oxidant, etc. but also several treatment settings. alkali treatment is one of the most widespread and economical methods used for surface modification of lignocellulosic biomass. in the field of biorefinary, alkali pretreatment is intensively employed to develop the cellulosic materials both mechanically as well as chemically and such properties include tensile strength, dyeability, stability of dimension and reactivity (wu et al. 2011). in alkali pretreatment biomass is treated under moderate reaction conditions ensuring inexpensiveness, inflated recycling possibilities of water and chemical agents (mcintosh and vancov, 2010). usually alkali treatment is the most effective pretreatment for agricultural residues, herbaceous crops and hardwood containing low lignin content in the compariosn of softwood containing high lignin content (agbor et al. 2011; canilha et al. 2012). this research aims is to investigate the alkaline pretreatment repercussions based on the chemical structure, surface morphology, structure and enzymatic digestion of sugarcane bagasse for sugars and ethanol production. materials and methods sugarcane bagasse (sb) was taken from street juice vendor. warm tap water was used for washing purpose to eliminate the residual free sugars once again. this washing and pressing step was then repeated for three times. after that drying was done in an oven at 65oc for 16 h. crushing of dried bagasse was done successively using a locally made crusher and sieved (retsch, d-42759, haan, germany) to have the particle size of 20-40 mesh on average. before usage, the 20-40 mesh bagasse was kept at room temperature in an airtight plastic container (sujan et al. 2018). moisture and ash content moisture content of raw materials was measured using the astm d 4442-07 procedure. in a glass crucible, 2 grams of pretreatment sample containing 20-40 mesh were dried in oven at 105±2°c. the moisture content was expressed in percent wet basis and weight measurements were taken every 3 h. a muffle furnace was used for burning the oven-dried samples at 575±25°c for ash content determination following the astm standard e 1755-01. volatile matter the volatile matter analysis was carried out in accordance with astm standard d 271-48. four grams of raw materials were heated in a furnace at 950±20°c for seven minutes. the weight loss, excluding the weight of moisture pushed off at 105°c, is then used to calculate volatile matter. fixed carbon the difference between 100 and the total of volatile matter, moisture, and ash content was used to compute the fixed carbon percentage. chemical analysis the technical association of the pulp and paper industry (tappi) method detects α-cellulose (t 203 cm-99), pentosan (t 223 cm-01), klason lignin (t211 om-83), and acid soluble lignin (t um 250) on a dry basis. ultimate analysis ultimate analysis of samples was done by following the procedure astm standard d 5291-02. organic elemental analyzer (flash 2000, thermo scientific, usa) was used with a specific condition (reactor temp. 900°c, he: 250 kpa, o2: 250 kpa, tcd). low concentration alkali pretreatment different alkali concentration (0%, 2%, 4%, 6% and 8%), time (60, 90 and 120 min) and temperature (80, 100 and 120oc) were applied on raw material to check alkali effect on sb shown in table 3. a portion of the ground bagasse 20-40 mesh (10g) was taken into plastic zipper bag (temperature 80oc, figure 2a and 2b) and stainless-steel reactor (temperature 100oc and 120oc, figure 2c and 2d). different alkali concentration was applied during the pretreatment process (alkali to sb ratio ranging between 1:12). the mixture was heated at a particular temperature such as in a water bath (80oc) and oil bath (100oc and 120oc) for a desired length of time. in the course of pretreatment process the sample was manually mixed 2-3 times to attain proper alkali treatment. the treated sb was placed into a polyester bag to remove excess alkali water by pressing it. after that it was vigorously washed with tap water (repeated for five times) to remove the remaining alkali. finally the sb was dried in an oven at 65oc for 72 h and stored in a close container at room temperature for further experiment. regression model regression model has been developed for prediction of α-cellulose, pentosan and lignin in sb. the general form of the model is: y=α+α1x1 + α2x2+........................+αnxn + ε.......................(1) where α is the constant term. αi are the coefficient of variables xi. ε is the random error term which is minimized with simple least squares regression (slsr). regression coefficients of the independent variables namely alkali concentration, temperature and time are estimated by slsr method for developing regression model to predict α-cellulose, pentosan and lignin. efficiencies of these models are expressed by coefficient of multiple determination (r2) and adjusted r2. 2.9 separate hydrolysis and fermentation (shf) the hydrolysis experiment took place in 100 ml conical flux 10ml enzyme solution with 200 mg (2% dry wt.) in citrate buffer (0.05 m, ph 5.0) at 50°c for 48 h. in this case trichoderma viride was used for hydrolysis. hydrolysate was then heated for 15 min in a boiling water bath and centrifugation was done to remove solid particles. the supernatant was used for analysis of released sugars as described by jamal et al. (2011). during fermentation process according to firoz et al. (2012), 100 ml media was prepared and 0.5 g of commercial yeast saccharomyces cerevisiae was used as inoculum which showed good performance to converts sugar into bioethanol. this inoculated media mixture was poured in a suitable glassware and was kept in a shaking incubator for 48 h. 10 ml of this medium was then added into the flask and it was properly covered with aluminum foil. then it was placed in the incubator at 30oc for 24 h, 48 h, 72 h and 96 h for fermentation of sugars to bio-ethanol according to sujan et al. (2018). samples from hydrolysis and fermentation were performed by hplc. high performance liquid chromatography (hplc) in characterize part, concentration of sugars and ethanol were determined by hplc (ultimate 3000, thermo scientific, usa) method using hyper rez xp carbohydrate h+ 8 µm column (100×7.7 mm) equipped with a refractive index (shodex ri-101) detector. the mobile phase was degassed with deionized water with a flow rate of 0.7 ml/min and column temperature was maintained at 70°c. it is possible to measure the total sugar concentration in the hydrolysis liquid fraction by comparing its peak area detected by hplc with peak area of 1% standard sugar which consists of two sugars namely glucose and xylose (sujan et al. 2018). the same column which is specialized for fermentation broth analysis is used for ethanol detection. the kinetic parameters of ethanol fermentation were determined as follows (islam et al. 2019): crystallinity measurement x-ray diffraction (xrd) was used to determine the crystalline structure of the sb samples using a diffractometer (gbc xrd) and filtered copper k radiation (λ = 0.1542 nm) by a monochromator at 35.50 kv voltage and 28 ma current, with a speed of about 2o/min and scanning in the range of 10 80ºc. the crystallinity index (cri) was obtained from the ratio between the intensity of the 002 peak (i002, 2θ = 22.5) and the minimum dip (iam, 2 θ = 18.5) according to the following equation (roberta et al., 2012): cri (%) = [(i002 iam)/i002] ×100 ...................................... (2) where i002 is the highest peak intensity of plane 002 and iam is related to the amorphous structure. in present study, the average crystallite sizes were determined from the scherrer equation by using the diffraction pattern obtained from the 002 (hkl) lattice planes of cellulose samples d(hkl) = [(kλ / b(hkl) cos2θ] ............................................... (3) where d(hkl) (crystallite size), k (scherrer constant, 0.84), λ (x-ray wavelength, 0.154nm), b(hkl)(full width half maximum of the measured hkl reflection), and 2θ (corresponding bragg angle). scanning electron microscopy (sem) analysis in this research, sem (zeiss evo 18 sem) was used to detect the change of pretreated bagasse fibers. sem images were taken of different pretreated bagasse samples with acceleration voltage of 2.0 kv. results and discussion proximate analysis proximate analysis of sb sample (20-40 mesh) are presented in table i. primarily this analysis usually evaluate the fuel characteristics of raw materials. according to sun et al., 2009, higher moisture and ashcontent in samples lessen the heating value. ultimate analysis ultimate analysis denotes the elemental configuration of sb such as carbon, hydrogen, oxygen, nitrogen and sulfur which are shown in table ii. this examination helps to measure the percentage of carbon and hydrogen content in biomass that is responsible to determine the amount of air is required for complete combustion, composition of combustion gases and heat is generated by it (poddar et al. 2014). chemical properties raw sb contained 34.66±12% α-cellulose, 22.43±08% pentosan and 19.57±06% klason lignin in which 1.75±04% acid soluble lignin (dry basis) was detected by technical association of the pulp and paper industry (tappi) method. the chemical composition of sb was determined by acid hydrolysis and it was calculatedby hplc method as 45.35% glucose and 30.64% xylose (sujan et al., 2018). α-cellulose yield bagasse is mainly composed of cellulose, hemicellulose and lignin. besides these there are some extractives such as ash, wax, gum, pectin etc. during alkali pretreatment usually most of the extractives are removed with the increasing of alkali concentration. pretreatment of sb with different alkali concentration based on raw material (0%, 2%, 4%, 6% and 8%), time (60, 90 and 120 min) and temperature (80, 100 and 120oc) are shown in table iii. consequences of each independent experiment varying with alkali concentration, temperature and time on the α-cellulose yield were analyzed using matlab software. apparently, it was observed that α-cellulose yield was considerably increased with changes of alkali concentration ranging from 0% to 8% (34.66% to 63.58%). but no noticeable variation was observed in temperature-time alteration during pretreatment of sb. based on cellulose percentage obtained in treated bagasse, the optimum conditions for pretreatment reaction were selected as alkali concentration 8%, time 90 min and temperature 100oc. although cellulose content in treated sb was slowly increased with the increase of alkali concentration 12% attime 90 min and temperature 100oc but as a consequence of huge chemical consumption, recovery problem, chance of losses cellulose and hemicellulose, alkali concentrations for pretreatment above 8% was not considered as ideal concentration. effect of alkali concentration (ac), cooking time and temperature (temp) charge on α-cellulose yield as well as their statistical significance on the basis of f-test number are presented in regression equations (4). as shown in equations, cooking time at the maximum temperature had no significant effect on α-cellulose yield followed by alkali concentration charge. effect of temperature on α-cellulose yield was less in employed cooking conditions. for α-cellulose yield: α-cellulose yield = 82.05-0.151×temp-1.56×time-0.69×ac (r2=0.89, adjusted r2=0.87) ............................................. (4) for pentosan: pentosan = 13.58+0.086 × tem p + 0.006 × time+0.445 × ac (r2=0.67, adjusted r2=0.63) ............................................. (5) for lignin: lignin = 27.662-0.041×temp-0.001×time-01.242×ac (r2=0.93, adjusted r2=0.92) ............................................. (6) for predicting α-cellulose, percentage of pentosan and lignin, the most influential factor was alkali concentration and then cooking temperature for α-cellulose yield, which exhibited an almost linear dependence on both operational variables. the coefficient of determinations is good for α-cellulose yield and lignin percentage which hovers around 90 percent, although the figure is moderate more than 60 percent for pentosan. all these three models are significant (p<0.05) at 5% level of significance. in order to perceive the impact of alkali concentration and temperature on these three parameters, three-dimensional (3d) response surface plots were created by plotting the response (α-cellulose yield) pentosan and lignin on the z-axis versus the most influential one independent variable alkali concentration and temperature as shown in fig. 3 (a), (b) and (c). xrd analysis in 19th century the cellulose crystalline structure has been discovered and later it was verified by x-ray crystallography (meyer and misch, 1937; wilkie, 1961). the crystallinity index (cri) of non-woody biomass, such as grasses and agricultural residues, varies depending on the type of biomass. generally, non-woody biomass has a lower crystallinity index than woody biomass, typically ranging from 20-40%. the crystallinity index of non-woody biomass affects its digestibility and energy production potential.recently, researchers are being paid more attention on cellulose index because of its potential use in bioenergy production. since then several different models of cellulose index have been proposed. the most popular two-phase cellulose model describes cellulose chains as containing both crystalline (ordered) and amorphous (less ordered) region (park et al., 2010). alkali treatment of bagasse has been found to increase the crystallinity index of the bagasse. alkali treatment breaks down hemicellulose, making the cellulose molecules more ordered and crystalline, resulting in a higher crystallinity index. alkali treatment also increases the digestibility of the bagasse, making it easier to break down and therefore more suitable for bioenergy production. x-ray diffraction spectra of the sb and alkali treated sb were presented in figure 4. it was observed that the intensity of 101 and 002 peaks were gradually increased. the relative amount of crystalline cellulose (cri) in the total solid were calculated based on the equation (2) and obtained 18.68%, 24.80%, 27.23%, 32.69%, 36.45% and 39.19% for raw sb, 0%, 2%, 4%, 6% and 8% alkali treated sb samples respectively. the cri of alkali treated sb samples (not cellulose crystallinity) were intensely influenced by the composition of the samples. in case of lignocellulosic biomass examples, cellulose cri measured the relative amount of crystalline cellulose in the total solid. therefore, amorphous part of lignin and hemicellulose in biomass specimens were partially removed with the delignification process as a result the proportion of α-cellulose was increased and hence cri would be increased gradually. this interpretation could be proved by the fact that alkali-treated sb had higher cri than raw sb (zhao et al. 2010) and the portion of cellulose in the treated sb was also increased gradually. according to the equation 3, the average sizes of crystallite obtained were 3.28, 3.51, 3.63, 3.78, 3.90 and 4.06 nm for raw sb, 0%, 2%, 4%, 6% and 8% alkali treated sb samples respectively. the experimental data revealed that during delignification, the size of crystallite was increased. sem analysis sem is one of the most commanding tools widely used to investigate the lignocellulosic biomass surface (amiri and karimi, 2015). sem is usually employed for surface characterization, morphology and inspection of microstructure. in respect of biomass example through sem images we can compare the untreated and pretreated models which may lead to different insight into the biomass (karimi and taherzadeh, 2016). sem provides two-dimensional images of raw sb and alkali treated sb, which were taken and compared to the outcome of naoh treatment. all testers were coated with carbon tape and magnification of 500x was used. figure 4 shows the wall of raw sb (figure 6a) was intact where the alkali treated sb (figures 6c-6f), the cell wall was ruptured or splitted and hence packing of the fibers were partially loosened (firoz et al. 2012). sugar and ethanol yield enzymatic digestibility is the ability of enzymes to break down molecules into smaller molecules, such as glucose. it is used to measure the efficiency of enzyme-catalyzed reactions and the digestibility of cellulose. the enzymatic digestibility of a compound is affected by factors such as the compound's crystallinity index, the type of enzyme used, and the temperature and ph of the reaction. in this study the enzymatic digestibility of the alkali pretreated sb was improved by increasing pretreatment conditions. typically the pretreatment settings are selected by considering various factors such as feedstock characteristics, pretreatment chemical cost, energy consumption and recovery efficiency (wu et al. 2011). α-cellulose obtained by 8% alkali treated of sb was used for hydrolysis reaction and the reaction was carried out at an optimum condition set by sujan et al. (2018). the most effective enzymatic hydrolysis was taken place with trichoderma virideat 48 h and the theoretical yield of sugars i.e. glucose and xylose were obtained 89.59% and 61.23%, respectively. through fermentation process generated sugars were used to check ethanol production. yeast saccharomyces cerevisiae presented worthy performance to convert c6 sugar into ethanol when it was incubated at 30°c for 24 h and 16.81±0.32% ethanol yield was detected. conclusion α-cellulose yield was optimized by varying alkali concentration, temperature and cooking time. the most vital influencing factor for α-cellulose yield was alkali concentration and after that temperature performed a little bit. the optimum α-cellulose yield (63.58±0.05%) was obtained at 8% alkali concentration, 100oc and 90 minutes. in hydrolysis step of sb, trichoderma viridaewas used to convert 8% alkali treated sb into sugars and it was attained 89.59% glucose and 61.23% xylose which gave higher yield in compare with our previous study such as ball milled and mesh size varied sb sample (sujan et al. 2018). at fermentation step saccharomyces cerevisiae was used to convert hydrolysate of 8% alkali treated sb sample and ethanol yield was obtained 16.81±0.32% at 24 h. compositional analysis, imaging and crystallinity are three methods were performed. sem images can give different clues about sb including morphology, surface disruption and creation of highly accessible surface area iii) cri (18.68% to 39.19%) and crystal size (3.28 nm to 4.06 nm) of sb are increased with different alkali treatment (0%-8%). in this case it was observed that crystallinity, crystal size, accessible surface area, porosity, particle size, lignin and hemicellulose content and enzyme adsorption/desorption were acted as the most impressive factors for digestibility of sugarcane bagasse. acknowledgement authors would like to acknowledge pulp and paper division, bcsir for their cooperation. authors also like to thanks for the 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applications n. lal1,3, a. kumar2, k. chawla1,4, s. sharma1,5 and c. lal1,2* 1department of physics, university of rajasthan, jaipur, rajasthan 302004, india 2centre for non-conventional energy resources, university of rajasthan, rajasthan 302004, india 3govt. girls college, jhunjhunu, rajasthan 333001, india 4govt. college, pratapgarh, rajasthan 312605, india 5govt. college, jhunjhunu, rajasthan 333001, india abstract magnesium oxide has long been intriguing due to several significant phenomena, including wide laser emission, spin electron reflectivity, and defect-induced magnetism. mgo nanostructures have a variety of applications, from spintronics to wastewater treatment, depending on their size and shape. mg is sensitive material for hydrogen and forms mgh2, so we used mg/mgo as a sensor to sense hydrogen gas in the present work. magnesium oxide thin films were synthesized by electrodeposition technique using magnesium nitrate salt. xrd results suggested that the deposited thin films have a face-centered cubic structure. x-ray photoelectron spectroscopy was used to detect the elemental composition and chemical state with the general electronic structure of the sample. the morphology and growth of deposited nanostructure with elemental mapping of the thin film were investigated by sem-eds. the uv-visible analysis shows the calculated band gap for mgo thin filmwas 4.16 ev which is in the ultraviolet region. the i-v characteristics have been studied to find out the effect of hydrogenation on the synthesized mgo nanostructure and the sensitivity responseof about 31%. it is quiteevident that mgo nanostructure may be used for gas sensing applications (such as h2 gas). keywords: magnesium oxide; nanostructure; electro-deposition; electronic structure; hydrogenation *corresponding author’s e-mail: clsaini52@gmail.com; clsaini52@uniraj.ac.in available online at www.banglajol.info bangladesh j. sci. ind. res. 58(2), 119-128, 2023 introduction nanostructure magnesium oxide thin films have drawn considerable attention because of their specific physical, chemical, and optical properties. magnesium oxide, an insulating ionic simple oxide, crystallizes in bulk in the rock salt structure. the synthesized metal oxides with proper phase and structures have great interest in order to realize their specific properties that not only depend on their chemical composition but also on their shape,size, phase, crystal, and electronic structure as well as absorption ability, catalytic ability, surface reaction activity (lan et al. 2011; chatterjee et al. 2009; bhatte et al. 2012). since the discovery of carbon nanotubes, researchers have focused intensely on developing nanostructures made of other materials in a variety of domains (huang et al. 2013; yourdkhani and caruntu 2011). nanocubes, nanorods, and nanoflowers are the most coveted types of nanostructures, in addition to nanoparticles and thin films.for many oxide systems, these kinds of nanostructures and their advantages are being examined (wang et al. 2016; weber et al. 2008). magnesium oxide is a non-toxic, non-corrosive material that is rapidly utilized in composite materials for space flight, medicine, toxic waste treatment, and catalysis (zou et al. 2008; jia et al. 2013; wang and xue 2006). a variety of electrochemical biosensors have recently been created employing nanoscale mgo material as a precise and sensitive tool for analytical application and diagnostic analysis (ma et al. 2011; li et al. 2009). magnesium oxide has strong thermal conductivity as well as an excellent electrical insulator so valuable as thermocouples and heating systems components. mgo was known asa low-cost and environment-friendly material that has so many applications like bioresorbable materials that dissolve in biofluids (huang, 2018), drug delivery (ravaei et al. 2019), electrodes in pharmaceuticals and human fluids (kairya et al. 2017), resistive switching (guo et al. 2019), luminescence (nikiforov et al. 2016), photo-catalytic properties (demirci et al. 2015) and ultra-violet (uv) photodetector (zhou et al. 2019). mgo nanostructures have also been reported to exhibit thermoluminescence (abramishvili et al. 2011), radioluminescence (skvortsova and trinkler 2009), and electroluminescence (benia et al. 2007). thin metal oxide films that are electrically insulating are a crucial component of many different technologies, so magnesium oxide (mgo) has received a lot of attention for applicationssuch as spintronic devices since it has a material with a reasonably high dielectric constant. under the influence of uv light, methyl orange, and methylene blue dyes were degraded using the photocatalytic activity of mgo nanoparticles (mageshwari et al. 2013). hydrogen storage properties of mg/ti bilayer thin films were reported (jangid et al. 2021) at a different hydrogen pressure of 15 to 45 psi to realize the effect of hydrogenation. hydrogen is the lightest element in the universe, which is typical to detect and magnesium is very sensitive to hydrogen in comparison to other metals. (chawla et al. 2022). although magnesium (mg) is one of the better aspects for absorbing hydrogen, difficult to use this material for mobile applications due to its slow dynamics and need for high temperatures during dehydrogenation. due to its extremely large reversible hydrogen capacity, magnesium hydride is particularly intriguing (jangid et al. 2021). the present work reports the electrical behaviour and sensitivity of magnesium oxide (mgo) asa sensor to sense h2 gas. in a similar work dip-coated cuo thin films were used to investigate the gas-sensing response of co2 vapor in air at room temperature and reported that the physical qualities that can be altered have a lot of potential for co2 gas-sensing applications. (musa et al. 2021). for the synthesis of thin films with nanostructures, an easy, affordable, and solution-based hybrid method is electro-deposition. mgo nanostructures have been grown successfully from an aqueous solution of magnesium nitrate mg(no3)2 using the electrodeposition method (taleatu et al. 2014). the deposition procedure can be applied to a variety of conductive substrates, including polymers, semiconductors and ito-coated glass. indium tin oxide (ito) is the most widely used substrate because of its outstanding transparency to visible light and high electric conductivity (muchuweni et al. 2017). in the present work, magnesium oxide nanostructure thin film deposited by electrode position technique using magnesium nitrate solution. to synthesize mgo nanostructure, a variety of experimental procedures have been proposed, including reactive sputtering (choi and kim 2004), metal-organic molecular beam epitaxy (niu et al. 2000), chemical vapor deposition (carta et al. 2007), sol-gel (zulkefle et al. 2011), and pulsed laser deposition (kaneko et al. 2013). materials and methods a conventional homemade two-electrode electrochemical bathsetup with labelled diagram shown in fig. 1(b) was used in which graphite sheet was used as a counter electrode and ito coated glass substrate as a working electrode. both electrodes were introduced in the bath through two steel tubes. the electrolyte solution of 0.25 m concentration was prepared using magnesium nitrate mg(no3)2 salt. before the deposition process, the ito-coated glass substrate was extensively cleaned in an ultrasonic bath and rinsed with ultrapure water prior to the deposition in order to remove any surface impurities. by applying a potential difference of 2.5 v at room temperature for 30 minutes by htc power supply dc 3002, a thin layer of mgo nanostructures was deposited on ito substrate. the deposited sample was dehydrated up to 350oc at a heating rate of 10oc/min in a furnace shown in fig. 1(c) and hold for 90 minutes and thencooled at natural/normal atmosphere conditions, finally, mgo nanostructure was formed. characterization of the nanostructure shimadzu uv-2600 uv-visible spectrometer was used to analyze the optical characteristics, and fourier transform infrared spectrometer (ftir) bruker alpha was used to collect data about various functional groups present in the samplein the range 4000–500 cm-1. the structural and morphological characterization of the deposited nanostructure thin films was characterized by x-ray diffraction (xrd, model: a siemens d-5000 x-ray diffractometer) using cu-kα [1.54å] radiation. the kinetic energy distribution of photoelectrons released from the specimen material was measured using x-ray photoemission spectroscopy (model: omicron esca (electron spectroscope for chemical analysis) oxford instrument germany). in this model aluminium anode was used for samplesthat have energy 1486.7 ev. sem (model: jsm-7610f plus & make: jeol) was used to analyze the surface morphology and microstructure of deposited mgo nanostructures. the i-v characteristics for hydrogensensing were measured by using a keithley electrometer 6517a and a pressure-composition-isotherm (pci) setupat vacuum (1 *10-3 mbar) and by introducing hydrogen (at 5 bar) in the stainless-steel chamber. results and discussion following equations (i-iv) show the overall chemical reaction for the deposition of mgo nanostructure thin film using magnesium nitrate salt in aquas medium (hashaikeh and szpunar 2009). x-ray diffraction (xrd) analysis diffraction measurement was carried out with an angular scanning range of (20° – 80°) to explore the nature of the material, purity, and crystallinity of the sample. fig. 2 shows the xrd pattern of synthesized nanostructure thin films. in fig. 2, spectrum (a) shows xrd pattern of theusedito substrate, (b) shows the xrd pattern of thin film before annealing and (c) shows the xrd pattern of thin film after annealing. as discussed in equation (iii) and (iv) the xrd pattern represented by fig. 2(b) for mg(oh)2 and fig. 2(c) for mgo. the substrate peak marked by (*) is visible after post annealing at 350°c when conversion of mg(oh)2 into mgo nanostructure at ito substrate (alsultany et al. 2014). fig. 2(c) has distinctive sharp peaks correspond to (111), (200), (220) and (222) planes related to fcc structure (cvetkovic et al. 2018). the sharp peaks illustrate that the synthesized nanostructure has a good crystalline nature. the debye-scherrer equation (ashok et al. 2016) was used to compute the crystallite size d (nm). where λ, β, and 2θ were the wavelength of the incident x-ray beam (cu kα1.54 å), full width at half maximum (fwhm) in radian and bragg’s diffraction angle of the preferred orientation. the mean calculated crystalline size (d) for the deposited nanostructure was determined to be approximately 36 nm. a surface-sensitive spectroscopic method (xps) was used to determine the various elements present in a material (also known as its elemental composition), as well as their chemical state, general electronic structure, and density of their electronic states. the investigations about surface composition and chemical state of deposited mgo nanostructures using core-level light emission were reported and shown in fig. 3. it was clear from the survey scan (fig. 3a) that the deposited nanostructures were the mgo nanostructure during the synthesis process and no substantial pollutant was present in the sample. in the survey scan of the sample, the presence of carbon (c), oxygen (o), and magnesium (mg) elements and no major contaminant can be seen which validate by the elemental signals received. contamination of carbon was due to the environmental presence during the synthesis process which can be seen in fig. 3a. the mg 1s core level at 1302.8 ev is the peak with the highest intensity in the spectrum of deposited mgo nanostructure. the peak observed at 531.64 ev corresponds to o2− in the lattice of mgo. the core level spectra of mg2p were also shown in fig. 3d, where a gaussian peak of mgo at b.e. 50.91 ev was fitted using the casa xps software, and results indicate that the nanostructure of mgo was present with mg lattice, which also confirms the existence in the core level spectra of mg 1s (fig. 3b) and o 1s (fig. 3c) where mgo peak also present with lattice oxygen in the sample. the mg 2p peak analysis in fig. 3d demonstrates that mg remains in a single chemical state throughout the development process, and the characteristic b.e determines its oxidation. the binding energy of all peaks related to elemental composition with the electronic state in the survey scan from fig. 3(a) is tabulated as follows: scanning electron micrograph (sem) analysis the sem micrographs of the deposited mgo nanostructured thin films were obtained and shown in fig. 4 together with the chemical elemental mapping. the inset table provides information about the elements which were found in the deposited nanostructure. the results indicate that the mgo nanostructure was synthesized with porous surface and deposited accurately by this method. as the number of porous was more on surface of deposited film than it would be easy for detecting the gas by increasing the amount of active area that is available for gas adsorption (liu et al. 2014; liu et al. 2016; musa et al. 2021). the chemical compositions of the deposited nanostructure thin film on ito substrate are also measured by edx detector which is inbuilt into sem. it is also evident that the nanostructure was adequately present in the form, which supports the xps results. uv-visible analysis the absorption spectra of the synthesized magnesium oxide nanostructure thin films were obtained in the range of 200 and 800 nm using uv-visible spectrometer. tauc's formula in equation (vi) was used to calculate the band gap of synthesized mgo nanostructure (tauc et al. 1966) where α, h, ν, c and eg are the absorption coefficient, plank’s constant, frequency of the incident photon, a constant, and the direct transition band gap respectively. the uv-visible spectra were shown in fig. 5, in which fig. (a) indicates the absorbance spectrum (b) represents tauc’s plot to determine the optical band gap while fig. (c) denotes the derivative of absorbance versus energy for verification of band gap and (d) transmittance spectrum for the deposited mgo nanostructure. the calculated band gap with the help of the above equation and extrapolation of the curve as shown in fig. 5(b) was found about 4.16 ev, which is less than the band gap of bulk magnesium oxide (7.8 ev) as reported by many authors (bilalbegovic et al. 2004; guney et al. 2018; egwunyenga et al. 2019; baghezza, 2019). the band gap was also verified by the derivative versus energy curve which has a peak at 4.2 ev as shown in fig. 5(c). the resultant curve was linear throughout a wide range of photon energy, showing that the deposited nanostructure was a direct transition material. the band gap of metal oxide nanostructure decreases due to presence of defect states, so these defectstates are responsible for the large difference in band gap energy. both nanoparticles and nanostructures exhibit the same trend in band gap energy fluctuation however, nanostructures have a lower band gap energy than nanoparticles of the same size because of increased lattice strain and a larger surface to volume ratio (abdullah et al. 2022). guney and iskenderoglu, (2018) found that the band gap of mgo nanostructures varied with thickness from 4.31 to 4.61 ev and that the band gaps were decreased as sample thickness increased. the reduction in band gap may be related to variations in the atomic distance with the rise in film thickness. tlili et al. (2021) studied the variation of band gap from 4.01 to 4.08 ev for different molar concentrations (0.05, 0.1, 0.15, 0.2 mol·l−1) of mg2+ ions by spray pyrolys is technique and reported that, as the molar concentration of mg2+ increases, the optical band gap decreases. ftir analysis ftir spectroscopy was used to detect the existence of organic or inorganic constituents in the deposited nanostructure, which was connected to various functional groups associated with specific absorbance peaks in the spectra. the ftir spectra of deposited mgo nanostructure thin film with transmission peaks ranging from 500 to 4000 cm-1 are shown in fig. 6. the peak obtained at 545 cm-1 indicates the stretching vibration of mgo. as a result of the chemicals used during the synthesis process, the sample also contained additional functional groups at various peaks corresponding to co2, -co, c-h and -oh, etc. electrical properties the electrical properties such as current-voltage (i–v) characteristics were measuredin vacuum and with hydrogen gas by keithley electrometer 6517a in the range from -3 volt to 3 voltat room temperature. this study provides detailed information about the electronic effects in presence of hydrogen gas on deposited mgo nanostructure thin film. the curve exhibits considerable nonlinearity compared to a thin mgo tunnel barrier. it can be seen from fig. 7 that in presence of hydrogen gas, the conductivity increases in forward bias as well as in reverse bias, which can be explained as the charge shift from hydrogen to the film structure because hydrogen acts like a donor element. this property of mgo offers useful information about gas sensing applications like hydrogen gas and also can be employed as hydrogen storage materials. a similar study has been reported for mg/ti bilayer thin films (jangid et al. 2021), mg-ni thin films (jangid and jangid, 2022) and for cdte/mn bilayer thin films (nehra et al. 2009) that show the hydrogen storage properties of these bilayer thin films. a stainless-steel sealed chamber containing the synthesized sample was usedto measurecurrent-voltage characteristics while exposed to h2 gas in vacuum. the block diagram and pci/pct set up sown in fig. 8. the resistance response of synthesized mgo thin film was converted into a sensitivity value using equation (vii) (moumen et al. 2019; musa et al. 2021). where r0 stands for the film's resistance in vacuum, and rg for its resistance after being exposed to h2 gas. using equation (vii), the mgo nanostructure's sensitivity response to h2 gas was estimated to be about 31%. conclusion the mgo nanostructure thin film was synthesized on ito-coated glass substrate at room temperature by a simplified electrodeposition method using aqueous solution of magnesium nitrate and investigated by different characterization techniques. a cubic structure of mgo with a predicted crystalline size of about 36 nm was calculated by xrd investigation. the sem-edx image confirms the porous structure, adherent to the substrate and atomic % of available elements in the deposited mgo nanostructure thin films. the elemental composition and chemical states with binding energy were obtained using xps. the uv-visible analysis confirmed the optical band gap of the deposited nanostructure was ~ 4.16 ev. the i-v characteristics of deposited nanostructure suggest the partial semiconductor nature and the conductivity increases in presence of hydrogen. the sensitivity response of deposited nanostructure was approximately 31% on exposure to h2 gas. the deposited mgo nanostructures provide useful information about gas sensing applications such as hydrogen gas and also can be employed as hydrogen storage materials. the ultrafine nanostructures (such as qds etc.) provide a large and sensitive surface area for a promising solution to decrease the operating temperature for metal oxide semiconductor-based gas sensors (liu et al. 2014; liu et al. 2016). their high surface energy allows for the absorption of gas molecules even at room temperature for the sensing application. acknowledgement this research work was performed in dept. of physics, university of rajasthan, jaipur, india. the author is high thanks to the director cncer, university of rajasthan, jaipur, rajasthan india for providing characterization facilities. references abdullah bj (2022), size effect of band gap in semiconductor nanocrystals and nanostructures from density functional theory within hse06, materials science in semiconductor processing, 137: 106214. doi: 10.1016/j.mssp.2021.106214. abramishvili m, akhvlediani z, galustashvili m, dekanozishvili g, kalabegishvili t, kvatchadze v and tavkhelidze v (2011), peculiarities of radiation effects in mgo: mn2+ crystals, journalof modern physics 2: 841–844. doi:10.4236/jmp.2011.28099. alsultany fh, ahmed nm and matjafri mz (2014), effects of cw co2 laser annealing on indium tin oxide thin films characteristics, soft nanoscience letters 4(04): 83. doi: 10.4236/snl.2014.44012. ashok c, rao kv, chakra cs and rao kg (2016), mgo nanoparticles prepared by microwave-irradiation technique and its seed germination application, nano trends: a journal of nanotechnology and its application 18: 10-17. doi: 10.3390/nano11113076 baghezza mohammad (2019), optical and electrical properties of mgo thin films. khider university, m. l. b. m. m, http://a rchives. univbiskra. dz/ handle/ 123456 789/13780. bilalbegovic, g. 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omotoso e, lal c, makinde wo, ogundele kt, ajenifuja e, lasisi ar, eleruja ma and mola gt (2014), xps and some surface characterizations of electrodeposited mgo nanostructure, surfaceand interface analysis 46: 372-377. doi: 10.1002/sia.5425 tauc j, grigorovici r and vancu a (1966), optical properties and electronic structure of amorphous germanium, basic solid-state physics 15: 627-637. doi: 10.1002/pssb.19660150224. tlili m, nefzi c, alhalaili b, bouzidi c, ajilil, jebbari n and turki kamoun n (2021), synthesis and characterization of mgo thin films obtained by spray technique for optoelectronic applications, nanomaterials 11(11): 3076 (1-15). doi: 10.3390/nano11113076. wang x, feng j, bai y, zhang q and yin y (2016), synthesis, properties, and applications of hollow micro-/nanostructures, chemical reviews 116: 10983-11060. doi: 10.1021/ acs.chemrev.5b00731 wang x and xue d (2006), direct observation of the shape evolution of mgo whiskers in a solution system, materialsletters 60: 3160-3164. doi: 10.1016/j.matlet.2006.02.066 weber j, singhal r, zekri s and kumar a (2008), one-dimensional nanostructures: fabrication, characterisation and applications, international materials review 53(4): 235-255. doi: 10.1179/174328008x348183 yourdkhani a and caruntu g (2011), highly ordered transition metal ferrite nanotube arrays synthesized by template-assisted liquid phase deposition, journal of material chemistry 21: 7145-7153. doi: 10.1039/c0jm04441e zhou c, ali q, chen x, gao x, liu k and shen d (2019), ultraviolet photodetectors based on wide bandgap oxide semiconductor films, chinese physics b 28: 048503. doi: 10.1088/1674-1056/28/4/048503 zou g, chen w, liu r and xu z (2008), morphology-tunable synthesis and characterizations of mg(oh)2 films via a cathodic electrochemical process, materials chemistry and physics 107: 85-90. doi: 10.1016/j.matchemphys. 2007.06.046 zulkefle h, ismail ln, bakar ra and mahmood mr (2011), molar concentration effect on mgo thin films properties, in proceedings of the ieee symposium on industrial electronics and applications, langkawi, malaysia, pp 468-471. doi: 10.1109/isiea.2011.6108754. doi: https://doi.org/10.3329/bjsir.v58i2.64166 received: 29 january 2023 revised: 21 may 2023 accepted: 21 may 2023 short communication synthesis of mgo nanostructure thin films via electrodeposition method 58(2) 2023120 mgo was known asa low-cost and environment-friendly material that has so many applications like bioresorbable materials that dissolve in biofluids (huang, 2018), drug delivery (ravaei et al. 2019), electrodes in pharmaceuticals and human fluids (kairya et al. 2017), resistive switching (guo et al. 2019), luminescence (nikiforov et al. 2016), photo-catalytic properties (demirci et al. 2015) and ultra-violet (uv) photodetector (zhou et al. 2019). mgo nanostructures have also been reported to exhibit thermoluminescence (abramishvili et al. 2011), radioluminescence (skvortsova and trinkler 2009), and electroluminescence (benia et al. 2007). thin metal oxide films that are electrically insulating are a crucial component of many different technologies, so magnesium oxide (mgo) has received a lot of attention for applicationssuch as spintronic devices since it has a material with a reasonably high dielectric constant. under the influence of uv light, methyl orange, and methylene blue dyes were degraded using the photocatalytic activity of mgo nanoparticles (mageshwari et al. 2013). hydrogen storage properties of mg/ti bilayer thin films were reported (jangid et al. 2021) at a different hydrogen pressure of 15 to 45 psi to realize the effect of hydrogenation. hydrogen is the lightest element in the universe, which is typical to detect and magnesium is very sensitive to hydrogen in comparison to other metals. (chawla et al. 2022). although magnesium (mg) is one of the better aspects for absorbing hydrogen, difficult to use this material for mobile applications due to its slow dynamics and need for high temperatures during dehydrogenation. due to its extremely large reversible hydrogen capacity, magnesium hydride is particularly intriguing (jangid et al. 2021). the present work reports the electrical behaviour and sensitivity of magnesium oxide (mgo) asa sensor to sense h2 gas. in a similar work dip-coated cuo thin films were used to investigate the gas-sensing response of co2 vapor in air at room temperature and reported that the physical qualities that can be altered have a lot of potential for co2 gas-sensing applications. (musa et al. 2021). for the synthesis of thin films with nanostructures, an easy, affordable, and solution-based hybrid method is electro-deposition. mgo nanostructures have been grown successfully from an aqueous solution of magnesium nitrate mg(no3)2 using the electrodeposition method (taleatu et al. 2014). the deposition procedure can be applied to a variety of conductive substrates, including polymers, semiconductors and ito-coated glass. indium tin oxide (ito) is the most widely used substrate because of its outstanding transparency to visible light and high electric conductivity (muchuweni et al. 2017). in the present work, magnesium oxide nanostructure thin film deposited by electrode position technique using magnesium nitrate solution. to synthesize mgo nanostructure, a variety of experimental procedures have been proposed, including reactive sputtering (choi and kim 2004), metal-organic molecular beam epitaxy (niu et al. 2000), chemical vapor deposition (carta et al. 2007), sol-gel (zulkefle et al. 2011), and pulsed laser deposition (kaneko et al. 2013). materials and methods a conventional homemade two-electrode electrochemical bathsetup with labelled diagram shown in fig. 1(b) was used in which graphite sheet was used as a counter electrode and ito coated glass substrate as a working electrode. both electrodes were introduced in the bath through two steel tubes. the electrolyte solution of 0.25 m concentration was prepared using magnesium nitrate mg(no3)2 salt. before the deposition process, the ito-coated glass substrate was extensively cleaned in an ultrasonic bath and rinsed with ultrapure water prior to the deposition in order to remove any surface impurities. by applying a potential difference of 2.5 v at room temperature for 30 minutes by htc power supply dc 3002, a thin layer of mgo nanostructures was deposited on ito substrate. the deposited sample was dehydrated up to 350oc at a heating rate of 10oc/min in a furnace shown in fig. 1(c) and hold for 90 minutes and thencooled at natural/normal atmosphere conditions, finally, mgo nanostructure was formed. characterization of the nanostructure shimadzu uv-2600 uv-visible spectrometer was used to analyze the optical characteristics, and fourier transform infrared spectrometer (ftir) bruker alpha was used to collect data about various functional groups present in the samplein the range 4000–500 cm-1. the structural and morphological characterization of the deposited nanostructure thin films was characterized by x-ray diffraction (xrd, model: a siemens d-5000 x-ray diffractometer) using cu-kα [1.54å] radiation. the kinetic energy distribution of photoelectrons released from the specimen material was measured using x-ray photoemission spectroscopy (model: omicron esca (electron spectroscope for chemical analysis) oxford instrument germany). in this model aluminium anode was used for samplesthat have energy 1486.7 ev. sem (model: jsm-7610f plus & make: jeol) was used to analyze the surface morphology and microstructure of deposited mgo nanostructures. the i-v characteristics for hydrogensensing were measured by using a keithley electrometer 6517a and a pressure-composition-isotherm (pci) setupat vacuum (1 *10-3 mbar) and by introducing hydrogen (at 5 bar) in the stainless-steel chamber. results and discussion following equations (i-iv) show the overall chemical reaction for the deposition of mgo nanostructure thin film using magnesium nitrate salt in aquas medium (hashaikeh and szpunar 2009). x-ray diffraction (xrd) analysis diffraction measurement was carried out with an angular scanning range of (20° – 80°) to explore the nature of the material, purity, and crystallinity of the sample. fig. 2 shows the xrd pattern of synthesized nanostructure thin films. in fig. 2, spectrum (a) shows xrd pattern of theusedito substrate, (b) shows the xrd pattern of thin film before annealing and (c) shows the xrd pattern of thin film after annealing. as discussed in equation (iii) and (iv) the xrd pattern represented by fig. 2(b) for mg(oh)2 and fig. 2(c) for mgo. the substrate peak marked by (*) is visible after post annealing at 350°c when conversion of mg(oh)2 into mgo nanostructure at ito substrate (alsultany et al. 2014). fig. 2(c) has distinctive sharp peaks correspond to (111), (200), (220) and (222) planes related to fcc structure (cvetkovic et al. 2018). the sharp peaks illustrate that the synthesized nanostructure has a good crystalline nature. the debye-scherrer equation (ashok et al. 2016) was used to compute the crystallite size d (nm). where λ, β, and 2θ were the wavelength of the incident x-ray beam (cu kα1.54 å), full width at half maximum (fwhm) in radian and bragg’s diffraction angle of the preferred orientation. the mean calculated crystalline size (d) for the deposited nanostructure was determined to be approximately 36 nm. a surface-sensitive spectroscopic method (xps) was used to determine the various elements present in a material (also known as its elemental composition), as well as their chemical state, general electronic structure, and density of their electronic states. the investigations about surface composition and chemical state of deposited mgo nanostructures using core-level light emission were reported and shown in fig. 3. it was clear from the survey scan (fig. 3a) that the deposited nanostructures were the mgo nanostructure during the synthesis process and no substantial pollutant was present in the sample. in the survey scan of the sample, the presence of carbon (c), oxygen (o), and magnesium (mg) elements and no major contaminant can be seen which validate by the elemental signals received. contamination of carbon was due to the environmental presence during the synthesis process which can be seen in fig. 3a. the mg 1s core level at 1302.8 ev is the peak with the highest intensity in the spectrum of deposited mgo nanostructure. the peak observed at 531.64 ev corresponds to o2− in the lattice of mgo. the core level spectra of mg2p were also shown in fig. 3d, where a gaussian peak of mgo at b.e. 50.91 ev was fitted using the casa xps software, and results indicate that the nanostructure of mgo was present with mg lattice, which also confirms the existence in the core level spectra of mg 1s (fig. 3b) and o 1s (fig. 3c) where mgo peak also present with lattice oxygen in the sample. the mg 2p peak analysis in fig. 3d demonstrates that mg remains in a single chemical state throughout the development process, and the characteristic b.e determines its oxidation. the binding energy of all peaks related to elemental composition with the electronic state in the survey scan from fig. 3(a) is tabulated as follows: scanning electron micrograph (sem) analysis the sem micrographs of the deposited mgo nanostructured thin films were obtained and shown in fig. 4 together with the chemical elemental mapping. the inset table provides information about the elements which were found in the deposited nanostructure. the results indicate that the mgo nanostructure was synthesized with porous surface and deposited accurately by this method. as the number of porous was more on surface of deposited film than it would be easy for detecting the gas by increasing the amount of active area that is available for gas adsorption (liu et al. 2014; liu et al. 2016; musa et al. 2021). the chemical compositions of the deposited nanostructure thin film on ito substrate are also measured by edx detector which is inbuilt into sem. it is also evident that the nanostructure was adequately present in the form, which supports the xps results. uv-visible analysis the absorption spectra of the synthesized magnesium oxide nanostructure thin films were obtained in the range of 200 and 800 nm using uv-visible spectrometer. tauc's formula in equation (vi) was used to calculate the band gap of synthesized mgo nanostructure (tauc et al. 1966) where α, h, ν, c and eg are the absorption coefficient, plank’s constant, frequency of the incident photon, a constant, and the direct transition band gap respectively. the uv-visible spectra were shown in fig. 5, in which fig. (a) indicates the absorbance spectrum (b) represents tauc’s plot to determine the optical band gap while fig. (c) denotes the derivative of absorbance versus energy for verification of band gap and (d) transmittance spectrum for the deposited mgo nanostructure. the calculated band gap with the help of the above equation and extrapolation of the curve as shown in fig. 5(b) was found about 4.16 ev, which is less than the band gap of bulk magnesium oxide (7.8 ev) as reported by many authors (bilalbegovic et al. 2004; guney et al. 2018; egwunyenga et al. 2019; baghezza, 2019). the band gap was also verified by the derivative versus energy curve which has a peak at 4.2 ev as shown in fig. 5(c). the resultant curve was linear throughout a wide range of photon energy, showing that the deposited nanostructure was a direct transition material. the band gap of metal oxide nanostructure decreases due to presence of defect states, so these defectstates are responsible for the large difference in band gap energy. both nanoparticles and nanostructures exhibit the same trend in band gap energy fluctuation however, nanostructures have a lower band gap energy than nanoparticles of the same size because of increased lattice strain and a larger surface to volume ratio (abdullah et al. 2022). guney and iskenderoglu, (2018) found that the band gap of mgo nanostructures varied with thickness from 4.31 to 4.61 ev and that the band gaps were decreased as sample thickness increased. the reduction in band gap may be related to variations in the atomic distance with the rise in film thickness. tlili et al. (2021) studied the variation of band gap from 4.01 to 4.08 ev for different molar concentrations (0.05, 0.1, 0.15, 0.2 mol·l−1) of mg2+ ions by spray pyrolys is technique and reported that, as the molar concentration of mg2+ increases, the optical band gap decreases. ftir analysis ftir spectroscopy was used to detect the existence of organic or inorganic constituents in the deposited nanostructure, which was connected to various functional groups associated with specific absorbance peaks in the spectra. the ftir spectra of deposited mgo nanostructure thin film with transmission peaks ranging from 500 to 4000 cm-1 are shown in fig. 6. the peak obtained at 545 cm-1 indicates the stretching vibration of mgo. as a result of the chemicals used during the synthesis process, the sample also contained additional functional groups at various peaks corresponding to co2, -co, c-h and -oh, etc. electrical properties the electrical properties such as current-voltage (i–v) characteristics were measuredin vacuum and with hydrogen gas by keithley electrometer 6517a in the range from -3 volt to 3 voltat room temperature. this study provides detailed information about the electronic effects in presence of hydrogen gas on deposited mgo nanostructure thin film. the curve exhibits considerable nonlinearity compared to a thin mgo tunnel barrier. it can be seen from fig. 7 that in presence of hydrogen gas, the conductivity increases in forward bias as well as in reverse bias, which can be explained as the charge shift from hydrogen to the film structure because hydrogen acts like a donor element. this property of mgo offers useful information about gas sensing applications like hydrogen gas and also can be employed as hydrogen storage materials. a similar study has been reported for mg/ti bilayer thin films (jangid et al. 2021), mg-ni thin films (jangid and jangid, 2022) and for cdte/mn bilayer thin films (nehra et al. 2009) that show the hydrogen storage properties of these bilayer thin films. a stainless-steel sealed chamber containing the synthesized sample was usedto measurecurrent-voltage characteristics while exposed to h2 gas in vacuum. the block diagram and pci/pct set up sown in fig. 8. the resistance response of synthesized mgo thin film was converted into a sensitivity value using equation (vii) (moumen et al. 2019; musa et al. 2021). where r0 stands for the film's resistance in vacuum, and rg for its resistance after being exposed to h2 gas. using equation (vii), the mgo nanostructure's sensitivity response to h2 gas was estimated to be about 31%. conclusion the mgo nanostructure thin film was synthesized on ito-coated glass substrate at room temperature by a simplified electrodeposition method using aqueous solution of magnesium nitrate and investigated by different characterization techniques. a cubic structure of mgo with a predicted crystalline size of about 36 nm was calculated by xrd investigation. the sem-edx image confirms the porous structure, adherent to the substrate and atomic % of available elements in the deposited mgo nanostructure thin films. the elemental composition and chemical states with binding energy were obtained using xps. the uv-visible analysis confirmed the optical band gap of the deposited nanostructure was ~ 4.16 ev. the i-v characteristics of deposited nanostructure suggest the partial semiconductor nature and the conductivity increases in presence of hydrogen. the sensitivity response of deposited nanostructure was approximately 31% on exposure to h2 gas. the deposited mgo nanostructures provide useful information about gas sensing applications such as hydrogen gas and also can be employed as hydrogen storage materials. the ultrafine nanostructures (such as qds etc.) provide a large and sensitive surface area for a promising solution to decrease the operating temperature for metal oxide semiconductor-based gas sensors (liu et al. 2014; liu et al. 2016). their high surface energy allows for the absorption of gas molecules even at room temperature for the sensing application. acknowledgement this research work was performed in dept. of physics, university of rajasthan, jaipur, india. the author is high thanks to the director cncer, university of rajasthan, jaipur, rajasthan india for providing characterization facilities. references abdullah bj (2022), size effect of band gap in semiconductor nanocrystals and nanostructures from density functional theory within hse06, materials science in semiconductor processing, 137: 106214. doi: 10.1016/j.mssp.2021.106214. abramishvili m, akhvlediani z, galustashvili m, dekanozishvili g, kalabegishvili t, kvatchadze v and tavkhelidze v (2011), peculiarities of radiation effects in mgo: mn2+ crystals, journalof modern physics 2: 841–844. doi:10.4236/jmp.2011.28099. alsultany fh, ahmed nm and matjafri mz (2014), effects of cw co2 laser annealing on indium tin oxide thin films characteristics, soft nanoscience letters 4(04): 83. doi: 10.4236/snl.2014.44012. ashok c, rao kv, chakra cs and rao kg (2016), mgo nanoparticles prepared by microwave-irradiation technique and its seed germination application, nano trends: a journal of nanotechnology and its application 18: 10-17. doi: 10.3390/nano11113076 baghezza mohammad (2019), optical and electrical properties of mgo thin films. khider university, m. l. b. m. m, http://a rchives. univbiskra. dz/ handle/ 123456 789/13780. bilalbegovic, g. 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hartiti b, comini e, arachchige hmm, fadili s and thevenin p (2019), preparation and characterization of nanostructured cuo thin films using spray pyrolysis technique, superlattices and microstructures 127: 2-10. doi: 10.1016/j.spmi.2018.06.061 muchuweni e, sathiaraj ts and nyakotyo h (2017), synthesis and characterization of zinc oxide thin films for optoelectronic applications, heliyon 3(4): e00285(1-18). doi: 10.1016/j.heliyon. 2017.e00285 musa amm, farhad sfu, gafur ma and jamil atmk (2021), effects of withdrawal speed on the structural, morphological, electrical, and optical properties of cuo thin films synthesized by dip-coating for co2 gas sensing, aip advances 11(11): 115004. doi: 10.1063/ 5.0060471 nehra sp, jangid mk, kumar a, singh m and vijay yk (2009), role of hydrogen in electrical and structural characteristics of bilayer cdte/mn diluted magnetic semiconductor thin films, international journal of hydrogen energy 34(17): 7306-7310. doi: 10.1016/j. ijhydene.2009.06.054 nikiforov sv, kortov vs and petrov mo (2016), luminescent and dosimetric properties of ultrafine magnesium oxide ceramics after high dose irradiation, radiationmeasurements 90: 252-256. doi: 10.1016/j.radmeas. 2015.12.018 niu f, hoerman bh and wessels bw (2000), metalorganic molecular beam epitaxy of magnesium oxide on silicon, mrs online proceedings library 619: 149-154. doi: 10.1557/proc-619-149. ravaei i, haghighat m and azami sm (2019), a dft, aim and nbo study of isoniazid drug delivery by mgo nanocage, applied surface science 469: 103-112. doi: 10.1016/j. apsusc.2018.11.005 shinji y, taro n, akio f, yoshishige s and koji a (2004), giant room-temperature magnetoresistance in single-crystal fe/mgo/fe magnetic tunnel junctions, nature materials 3: 868-871. doi:10.1038/nmat1257 skvortsova v and trinkler l (2009), luminescence of impurity and radiation defects in magnesium oxide irradiated by fast neutrons, physics procedia 2: 567-570. doi: 10.1016/j. phpro.2009.07.042 taleatu ba, omotoso e, lal c, makinde wo, ogundele kt, ajenifuja e, lasisi ar, eleruja ma and mola gt (2014), xps and some surface characterizations of electrodeposited mgo nanostructure, surfaceand interface analysis 46: 372-377. doi: 10.1002/sia.5425 tauc j, grigorovici r and vancu a (1966), optical properties and electronic structure of amorphous germanium, basic solid-state physics 15: 627-637. doi: 10.1002/pssb.19660150224. tlili m, nefzi c, alhalaili b, bouzidi c, ajilil, jebbari n and turki kamoun n (2021), synthesis and characterization of mgo thin films obtained by spray technique for optoelectronic applications, nanomaterials 11(11): 3076 (1-15). doi: 10.3390/nano11113076. wang x, feng j, bai y, zhang q and yin y (2016), synthesis, properties, and applications of hollow micro-/nanostructures, chemical reviews 116: 10983-11060. doi: 10.1021/ acs.chemrev.5b00731 wang x and xue d (2006), direct observation of the shape evolution of mgo whiskers in a solution system, materialsletters 60: 3160-3164. doi: 10.1016/j.matlet.2006.02.066 weber j, singhal r, zekri s and kumar a (2008), one-dimensional nanostructures: fabrication, characterisation and applications, international materials review 53(4): 235-255. doi: 10.1179/174328008x348183 yourdkhani a and caruntu g (2011), highly ordered transition metal ferrite nanotube arrays synthesized by template-assisted liquid phase deposition, journal of material chemistry 21: 7145-7153. doi: 10.1039/c0jm04441e zhou c, ali q, chen x, gao x, liu k and shen d (2019), ultraviolet photodetectors based on wide bandgap oxide semiconductor films, chinese physics b 28: 048503. doi: 10.1088/1674-1056/28/4/048503 zou g, chen w, liu r and xu z (2008), morphology-tunable synthesis and characterizations of mg(oh)2 films via a cathodic electrochemical process, materials chemistry and physics 107: 85-90. doi: 10.1016/j.matchemphys. 2007.06.046 zulkefle h, ismail ln, bakar ra and mahmood mr (2011), molar concentration effect on mgo thin films properties, in proceedings of the ieee symposium on industrial electronics and applications, langkawi, malaysia, pp 468-471. doi: 10.1109/isiea.2011.6108754. fig. 1: (a) schematic block diagram (b) electrodeposition working setup and (c) furnace for heating lal, kumar, chawla, sharma and lal 121 mgo was known asa low-cost and environment-friendly material that has so many applications like bioresorbable materials that dissolve in biofluids (huang, 2018), drug delivery (ravaei et al. 2019), electrodes in pharmaceuticals and human fluids (kairya et al. 2017), resistive switching (guo et al. 2019), luminescence (nikiforov et al. 2016), photo-catalytic properties (demirci et al. 2015) and ultra-violet (uv) photodetector (zhou et al. 2019). mgo nanostructures have also been reported to exhibit thermoluminescence (abramishvili et al. 2011), radioluminescence (skvortsova and trinkler 2009), and electroluminescence (benia et al. 2007). thin metal oxide films that are electrically insulating are a crucial component of many different technologies, so magnesium oxide (mgo) has received a lot of attention for applicationssuch as spintronic devices since it has a material with a reasonably high dielectric constant. under the influence of uv light, methyl orange, and methylene blue dyes were degraded using the photocatalytic activity of mgo nanoparticles (mageshwari et al. 2013). hydrogen storage properties of mg/ti bilayer thin films were reported (jangid et al. 2021) at a different hydrogen pressure of 15 to 45 psi to realize the effect of hydrogenation. hydrogen is the lightest element in the universe, which is typical to detect and magnesium is very sensitive to hydrogen in comparison to other metals. (chawla et al. 2022). although magnesium (mg) is one of the better aspects for absorbing hydrogen, difficult to use this material for mobile applications due to its slow dynamics and need for high temperatures during dehydrogenation. due to its extremely large reversible hydrogen capacity, magnesium hydride is particularly intriguing (jangid et al. 2021). the present work reports the electrical behaviour and sensitivity of magnesium oxide (mgo) asa sensor to sense h2 gas. in a similar work dip-coated cuo thin films were used to investigate the gas-sensing response of co2 vapor in air at room temperature and reported that the physical qualities that can be altered have a lot of potential for co2 gas-sensing applications. (musa et al. 2021). for the synthesis of thin films with nanostructures, an easy, affordable, and solution-based hybrid method is electro-deposition. mgo nanostructures have been grown successfully from an aqueous solution of magnesium nitrate mg(no3)2 using the electrodeposition method (taleatu et al. 2014). the deposition procedure can be applied to a variety of conductive substrates, including polymers, semiconductors and ito-coated glass. indium tin oxide (ito) is the most widely used substrate because of its outstanding transparency to visible light and high electric conductivity (muchuweni et al. 2017). in the present work, magnesium oxide nanostructure thin film deposited by electrode position technique using magnesium nitrate solution. to synthesize mgo nanostructure, a variety of experimental procedures have been proposed, including reactive sputtering (choi and kim 2004), metal-organic molecular beam epitaxy (niu et al. 2000), chemical vapor deposition (carta et al. 2007), sol-gel (zulkefle et al. 2011), and pulsed laser deposition (kaneko et al. 2013). materials and methods a conventional homemade two-electrode electrochemical bathsetup with labelled diagram shown in fig. 1(b) was used in which graphite sheet was used as a counter electrode and ito coated glass substrate as a working electrode. both electrodes were introduced in the bath through two steel tubes. the electrolyte solution of 0.25 m concentration was prepared using magnesium nitrate mg(no3)2 salt. before the deposition process, the ito-coated glass substrate was extensively cleaned in an ultrasonic bath and rinsed with ultrapure water prior to the deposition in order to remove any surface impurities. by applying a potential difference of 2.5 v at room temperature for 30 minutes by htc power supply dc 3002, a thin layer of mgo nanostructures was deposited on ito substrate. the deposited sample was dehydrated up to 350oc at a heating rate of 10oc/min in a furnace shown in fig. 1(c) and hold for 90 minutes and thencooled at natural/normal atmosphere conditions, finally, mgo nanostructure was formed. characterization of the nanostructure shimadzu uv-2600 uv-visible spectrometer was used to analyze the optical characteristics, and fourier transform infrared spectrometer (ftir) bruker alpha was used to collect data about various functional groups present in the samplein the range 4000–500 cm-1. the structural and morphological characterization of the deposited nanostructure thin films was characterized by x-ray diffraction (xrd, model: a siemens d-5000 x-ray diffractometer) using cu-kα [1.54å] radiation. the kinetic energy distribution of photoelectrons released from the specimen material was measured using x-ray photoemission spectroscopy (model: omicron esca (electron spectroscope for chemical analysis) oxford instrument germany). in this model aluminium anode was used for samplesthat have energy 1486.7 ev. sem (model: jsm-7610f plus & make: jeol) was used to analyze the surface morphology and microstructure of deposited mgo nanostructures. the i-v characteristics for hydrogensensing were measured by using a keithley electrometer 6517a and a pressure-composition-isotherm (pci) setupat vacuum (1 *10-3 mbar) and by introducing hydrogen (at 5 bar) in the stainless-steel chamber. results and discussion following equations (i-iv) show the overall chemical reaction for the deposition of mgo nanostructure thin film using magnesium nitrate salt in aquas medium (hashaikeh and szpunar 2009). x-ray diffraction (xrd) analysis diffraction measurement was carried out with an angular scanning range of (20° – 80°) to explore the nature of the material, purity, and crystallinity of the sample. fig. 2 shows the xrd pattern of synthesized nanostructure thin films. in fig. 2, spectrum (a) shows xrd pattern of theusedito substrate, (b) shows the xrd pattern of thin film before annealing and (c) shows the xrd pattern of thin film after annealing. as discussed in equation (iii) and (iv) the xrd pattern represented by fig. 2(b) for mg(oh)2 and fig. 2(c) for mgo. the substrate peak marked by (*) is visible after post annealing at 350°c when conversion of mg(oh)2 into mgo nanostructure at ito substrate (alsultany et al. 2014). fig. 2(c) has distinctive sharp peaks correspond to (111), (200), (220) and (222) planes related to fcc structure (cvetkovic et al. 2018). the sharp peaks illustrate that the synthesized nanostructure has a good crystalline nature. the debye-scherrer equation (ashok et al. 2016) was used to compute the crystallite size d (nm). where λ, β, and 2θ were the wavelength of the incident x-ray beam (cu kα1.54 å), full width at half maximum (fwhm) in radian and bragg’s diffraction angle of the preferred orientation. the mean calculated crystalline size (d) for the deposited nanostructure was determined to be approximately 36 nm. a surface-sensitive spectroscopic method (xps) was used to determine the various elements present in a material (also known as its elemental composition), as well as their chemical state, general electronic structure, and density of their electronic states. the investigations about surface composition and chemical state of deposited mgo nanostructures using core-level light emission were reported and shown in fig. 3. it was clear from the survey scan (fig. 3a) that the deposited nanostructures were the mgo nanostructure during the synthesis process and no substantial pollutant was present in the sample. in the survey scan of the sample, the presence of carbon (c), oxygen (o), and magnesium (mg) elements and no major contaminant can be seen which validate by the elemental signals received. contamination of carbon was due to the environmental presence during the synthesis process which can be seen in fig. 3a. the mg 1s core level at 1302.8 ev is the peak with the highest intensity in the spectrum of deposited mgo nanostructure. the peak observed at 531.64 ev corresponds to o2− in the lattice of mgo. the core level spectra of mg2p were also shown in fig. 3d, where a gaussian peak of mgo at b.e. 50.91 ev was fitted using the casa xps software, and results indicate that the nanostructure of mgo was present with mg lattice, which also confirms the existence in the core level spectra of mg 1s (fig. 3b) and o 1s (fig. 3c) where mgo peak also present with lattice oxygen in the sample. the mg 2p peak analysis in fig. 3d demonstrates that mg remains in a single chemical state throughout the development process, and the characteristic b.e determines its oxidation. the binding energy of all peaks related to elemental composition with the electronic state in the survey scan from fig. 3(a) is tabulated as follows: scanning electron micrograph (sem) analysis the sem micrographs of the deposited mgo nanostructured thin films were obtained and shown in fig. 4 together with the chemical elemental mapping. the inset table provides information about the elements which were found in the deposited nanostructure. the results indicate that the mgo nanostructure was synthesized with porous surface and deposited accurately by this method. as the number of porous was more on surface of deposited film than it would be easy for detecting the gas by increasing the amount of active area that is available for gas adsorption (liu et al. 2014; liu et al. 2016; musa et al. 2021). the chemical compositions of the deposited nanostructure thin film on ito substrate are also measured by edx detector which is inbuilt into sem. it is also evident that the nanostructure was adequately present in the form, which supports the xps results. uv-visible analysis the absorption spectra of the synthesized magnesium oxide nanostructure thin films were obtained in the range of 200 and 800 nm using uv-visible spectrometer. tauc's formula in equation (vi) was used to calculate the band gap of synthesized mgo nanostructure (tauc et al. 1966) where α, h, ν, c and eg are the absorption coefficient, plank’s constant, frequency of the incident photon, a constant, and the direct transition band gap respectively. the uv-visible spectra were shown in fig. 5, in which fig. (a) indicates the absorbance spectrum (b) represents tauc’s plot to determine the optical band gap while fig. (c) denotes the derivative of absorbance versus energy for verification of band gap and (d) transmittance spectrum for the deposited mgo nanostructure. the calculated band gap with the help of the above equation and extrapolation of the curve as shown in fig. 5(b) was found about 4.16 ev, which is less than the band gap of bulk magnesium oxide (7.8 ev) as reported by many authors (bilalbegovic et al. 2004; guney et al. 2018; egwunyenga et al. 2019; baghezza, 2019). the band gap was also verified by the derivative versus energy curve which has a peak at 4.2 ev as shown in fig. 5(c). the resultant curve was linear throughout a wide range of photon energy, showing that the deposited nanostructure was a direct transition material. the band gap of metal oxide nanostructure decreases due to presence of defect states, so these defectstates are responsible for the large difference in band gap energy. both nanoparticles and nanostructures exhibit the same trend in band gap energy fluctuation however, nanostructures have a lower band gap energy than nanoparticles of the same size because of increased lattice strain and a larger surface to volume ratio (abdullah et al. 2022). guney and iskenderoglu, (2018) found that the band gap of mgo nanostructures varied with thickness from 4.31 to 4.61 ev and that the band gaps were decreased as sample thickness increased. the reduction in band gap may be related to variations in the atomic distance with the rise in film thickness. tlili et al. (2021) studied the variation of band gap from 4.01 to 4.08 ev for different molar concentrations (0.05, 0.1, 0.15, 0.2 mol·l−1) of mg2+ ions by spray pyrolys is technique and reported that, as the molar concentration of mg2+ increases, the optical band gap decreases. ftir analysis ftir spectroscopy was used to detect the existence of organic or inorganic constituents in the deposited nanostructure, which was connected to various functional groups associated with specific absorbance peaks in the spectra. the ftir spectra of deposited mgo nanostructure thin film with transmission peaks ranging from 500 to 4000 cm-1 are shown in fig. 6. the peak obtained at 545 cm-1 indicates the stretching vibration of mgo. as a result of the chemicals used during the synthesis process, the sample also contained additional functional groups at various peaks corresponding to co2, -co, c-h and -oh, etc. electrical properties the electrical properties such as current-voltage (i–v) characteristics were measuredin vacuum and with hydrogen gas by keithley electrometer 6517a in the range from -3 volt to 3 voltat room temperature. this study provides detailed information about the electronic effects in presence of hydrogen gas on deposited mgo nanostructure thin film. the curve exhibits considerable nonlinearity compared to a thin mgo tunnel barrier. it can be seen from fig. 7 that in presence of hydrogen gas, the conductivity increases in forward bias as well as in reverse bias, which can be explained as the charge shift from hydrogen to the film structure because hydrogen acts like a donor element. this property of mgo offers useful information about gas sensing applications like hydrogen gas and also can be employed as hydrogen storage materials. a similar study has been reported for mg/ti bilayer thin films (jangid et al. 2021), mg-ni thin films (jangid and jangid, 2022) and for cdte/mn bilayer thin films (nehra et al. 2009) that show the hydrogen storage properties of these bilayer thin films. a stainless-steel sealed chamber containing the synthesized sample was usedto measurecurrent-voltage characteristics while exposed to h2 gas in vacuum. the block diagram and pci/pct set up sown in fig. 8. the resistance response of synthesized mgo thin film was converted into a sensitivity value using equation (vii) (moumen et al. 2019; musa et al. 2021). where r0 stands for the film's resistance in vacuum, and rg for its resistance after being exposed to h2 gas. using equation (vii), the mgo nanostructure's sensitivity response to h2 gas was estimated to be about 31%. conclusion the mgo nanostructure thin film was synthesized on ito-coated glass substrate at room temperature by a simplified electrodeposition method using aqueous solution of magnesium nitrate and investigated by different characterization techniques. a cubic structure of mgo with a predicted crystalline size of about 36 nm was calculated by xrd investigation. the sem-edx image confirms the porous structure, adherent to the substrate and atomic % of available elements in the deposited mgo nanostructure thin films. the elemental composition and chemical states with binding energy were obtained using xps. the uv-visible analysis confirmed the optical band gap of the deposited nanostructure was ~ 4.16 ev. the i-v characteristics of deposited nanostructure suggest the partial semiconductor nature and the conductivity increases in presence of hydrogen. the sensitivity response of deposited nanostructure was approximately 31% on exposure to h2 gas. the deposited mgo nanostructures provide useful information about gas sensing applications such as hydrogen gas and also can be employed as hydrogen storage materials. the ultrafine nanostructures (such as qds etc.) provide a large and sensitive surface area for a promising solution to decrease the operating temperature for metal oxide semiconductor-based gas sensors (liu et al. 2014; liu et al. 2016). their high surface energy allows for the absorption of gas molecules even at room temperature for the sensing application. acknowledgement this research work was performed in dept. of physics, university of rajasthan, jaipur, india. the author is high thanks to the director cncer, university of rajasthan, jaipur, rajasthan india for providing characterization facilities. references abdullah bj (2022), size effect of band gap in semiconductor nanocrystals and nanostructures from density functional theory within hse06, materials science in semiconductor processing, 137: 106214. doi: 10.1016/j.mssp.2021.106214. abramishvili m, akhvlediani z, galustashvili m, dekanozishvili g, kalabegishvili t, kvatchadze v and tavkhelidze v (2011), peculiarities of radiation effects in mgo: mn2+ crystals, journalof modern physics 2: 841–844. doi:10.4236/jmp.2011.28099. alsultany fh, ahmed nm and matjafri mz (2014), effects of cw co2 laser annealing on indium tin oxide thin films characteristics, soft nanoscience letters 4(04): 83. doi: 10.4236/snl.2014.44012. ashok c, rao kv, chakra cs and rao kg (2016), mgo nanoparticles prepared by microwave-irradiation technique and its seed germination application, nano trends: a journal of nanotechnology and its application 18: 10-17. doi: 10.3390/nano11113076 baghezza mohammad (2019), optical and electrical properties of mgo thin films. khider university, m. l. b. m. m, http://a rchives. univbiskra. dz/ handle/ 123456 789/13780. bilalbegovic, g. 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omotoso e, lal c, makinde wo, ogundele kt, ajenifuja e, lasisi ar, eleruja ma and mola gt (2014), xps and some surface characterizations of electrodeposited mgo nanostructure, surfaceand interface analysis 46: 372-377. doi: 10.1002/sia.5425 tauc j, grigorovici r and vancu a (1966), optical properties and electronic structure of amorphous germanium, basic solid-state physics 15: 627-637. doi: 10.1002/pssb.19660150224. tlili m, nefzi c, alhalaili b, bouzidi c, ajilil, jebbari n and turki kamoun n (2021), synthesis and characterization of mgo thin films obtained by spray technique for optoelectronic applications, nanomaterials 11(11): 3076 (1-15). doi: 10.3390/nano11113076. wang x, feng j, bai y, zhang q and yin y (2016), synthesis, properties, and applications of hollow micro-/nanostructures, chemical reviews 116: 10983-11060. doi: 10.1021/ acs.chemrev.5b00731 wang x and xue d (2006), direct observation of the shape evolution of mgo whiskers in a solution system, materialsletters 60: 3160-3164. doi: 10.1016/j.matlet.2006.02.066 weber j, singhal r, zekri s and kumar a (2008), one-dimensional nanostructures: fabrication, characterisation and applications, international materials review 53(4): 235-255. doi: 10.1179/174328008x348183 yourdkhani a and caruntu g (2011), highly ordered transition metal ferrite nanotube arrays synthesized by template-assisted liquid phase deposition, journal of material chemistry 21: 7145-7153. doi: 10.1039/c0jm04441e zhou c, ali q, chen x, gao x, liu k and shen d (2019), ultraviolet photodetectors based on wide bandgap oxide semiconductor films, chinese physics b 28: 048503. doi: 10.1088/1674-1056/28/4/048503 zou g, chen w, liu r and xu z (2008), morphology-tunable synthesis and characterizations of mg(oh)2 films via a cathodic electrochemical process, materials chemistry and physics 107: 85-90. doi: 10.1016/j.matchemphys. 2007.06.046 zulkefle h, ismail ln, bakar ra and mahmood mr (2011), molar concentration effect on mgo thin films properties, in proceedings of the ieee symposium on industrial electronics and applications, langkawi, malaysia, pp 468-471. doi: 10.1109/isiea.2011.6108754. fig. 2. xrd spectrum (a) bare ito (b) synthesized mg(oh)2 and (c) mgo thin film mg(no3)2 → mg 2+ + 2no3 – (i) h2o + 2e → h2 + 2oh (ii) mg2+ + 2oh → mg(oh)2 (iii) mg(oh)2→ mgo + h2o (iv) dehydration of mg(oh)2 produces mgo nanostructures onto ito substrate. synthesis of mgo nanostructure thin films via electrodeposition method 58(2) 2023122 mgo was known asa low-cost and environment-friendly material that has so many applications like bioresorbable materials that dissolve in biofluids (huang, 2018), drug delivery (ravaei et al. 2019), electrodes in pharmaceuticals and human fluids (kairya et al. 2017), resistive switching (guo et al. 2019), luminescence (nikiforov et al. 2016), photo-catalytic properties (demirci et al. 2015) and ultra-violet (uv) photodetector (zhou et al. 2019). mgo nanostructures have also been reported to exhibit thermoluminescence (abramishvili et al. 2011), radioluminescence (skvortsova and trinkler 2009), and electroluminescence (benia et al. 2007). thin metal oxide films that are electrically insulating are a crucial component of many different technologies, so magnesium oxide (mgo) has received a lot of attention for applicationssuch as spintronic devices since it has a material with a reasonably high dielectric constant. under the influence of uv light, methyl orange, and methylene blue dyes were degraded using the photocatalytic activity of mgo nanoparticles (mageshwari et al. 2013). hydrogen storage properties of mg/ti bilayer thin films were reported (jangid et al. 2021) at a different hydrogen pressure of 15 to 45 psi to realize the effect of hydrogenation. hydrogen is the lightest element in the universe, which is typical to detect and magnesium is very sensitive to hydrogen in comparison to other metals. (chawla et al. 2022). although magnesium (mg) is one of the better aspects for absorbing hydrogen, difficult to use this material for mobile applications due to its slow dynamics and need for high temperatures during dehydrogenation. due to its extremely large reversible hydrogen capacity, magnesium hydride is particularly intriguing (jangid et al. 2021). the present work reports the electrical behaviour and sensitivity of magnesium oxide (mgo) asa sensor to sense h2 gas. in a similar work dip-coated cuo thin films were used to investigate the gas-sensing response of co2 vapor in air at room temperature and reported that the physical qualities that can be altered have a lot of potential for co2 gas-sensing applications. (musa et al. 2021). for the synthesis of thin films with nanostructures, an easy, affordable, and solution-based hybrid method is electro-deposition. mgo nanostructures have been grown successfully from an aqueous solution of magnesium nitrate mg(no3)2 using the electrodeposition method (taleatu et al. 2014). the deposition procedure can be applied to a variety of conductive substrates, including polymers, semiconductors and ito-coated glass. indium tin oxide (ito) is the most widely used substrate because of its outstanding transparency to visible light and high electric conductivity (muchuweni et al. 2017). in the present work, magnesium oxide nanostructure thin film deposited by electrode position technique using magnesium nitrate solution. to synthesize mgo nanostructure, a variety of experimental procedures have been proposed, including reactive sputtering (choi and kim 2004), metal-organic molecular beam epitaxy (niu et al. 2000), chemical vapor deposition (carta et al. 2007), sol-gel (zulkefle et al. 2011), and pulsed laser deposition (kaneko et al. 2013). materials and methods a conventional homemade two-electrode electrochemical bathsetup with labelled diagram shown in fig. 1(b) was used in which graphite sheet was used as a counter electrode and ito coated glass substrate as a working electrode. both electrodes were introduced in the bath through two steel tubes. the electrolyte solution of 0.25 m concentration was prepared using magnesium nitrate mg(no3)2 salt. before the deposition process, the ito-coated glass substrate was extensively cleaned in an ultrasonic bath and rinsed with ultrapure water prior to the deposition in order to remove any surface impurities. by applying a potential difference of 2.5 v at room temperature for 30 minutes by htc power supply dc 3002, a thin layer of mgo nanostructures was deposited on ito substrate. the deposited sample was dehydrated up to 350oc at a heating rate of 10oc/min in a furnace shown in fig. 1(c) and hold for 90 minutes and thencooled at natural/normal atmosphere conditions, finally, mgo nanostructure was formed. characterization of the nanostructure shimadzu uv-2600 uv-visible spectrometer was used to analyze the optical characteristics, and fourier transform infrared spectrometer (ftir) bruker alpha was used to collect data about various functional groups present in the samplein the range 4000–500 cm-1. the structural and morphological characterization of the deposited nanostructure thin films was characterized by x-ray diffraction (xrd, model: a siemens d-5000 x-ray diffractometer) using cu-kα [1.54å] radiation. the kinetic energy distribution of photoelectrons released from the specimen material was measured using x-ray photoemission spectroscopy (model: omicron esca (electron spectroscope for chemical analysis) oxford instrument germany). in this model aluminium anode was used for samplesthat have energy 1486.7 ev. sem (model: jsm-7610f plus & make: jeol) was used to analyze the surface morphology and microstructure of deposited mgo nanostructures. the i-v characteristics for hydrogensensing were measured by using a keithley electrometer 6517a and a pressure-composition-isotherm (pci) setupat vacuum (1 *10-3 mbar) and by introducing hydrogen (at 5 bar) in the stainless-steel chamber. results and discussion following equations (i-iv) show the overall chemical reaction for the deposition of mgo nanostructure thin film using magnesium nitrate salt in aquas medium (hashaikeh and szpunar 2009). x-ray diffraction (xrd) analysis diffraction measurement was carried out with an angular scanning range of (20° – 80°) to explore the nature of the material, purity, and crystallinity of the sample. fig. 2 shows the xrd pattern of synthesized nanostructure thin films. in fig. 2, spectrum (a) shows xrd pattern of theusedito substrate, (b) shows the xrd pattern of thin film before annealing and (c) shows the xrd pattern of thin film after annealing. as discussed in equation (iii) and (iv) the xrd pattern represented by fig. 2(b) for mg(oh)2 and fig. 2(c) for mgo. the substrate peak marked by (*) is visible after post annealing at 350°c when conversion of mg(oh)2 into mgo nanostructure at ito substrate (alsultany et al. 2014). fig. 2(c) has distinctive sharp peaks correspond to (111), (200), (220) and (222) planes related to fcc structure (cvetkovic et al. 2018). the sharp peaks illustrate that the synthesized nanostructure has a good crystalline nature. the debye-scherrer equation (ashok et al. 2016) was used to compute the crystallite size d (nm). where λ, β, and 2θ were the wavelength of the incident x-ray beam (cu kα1.54 å), full width at half maximum (fwhm) in radian and bragg’s diffraction angle of the preferred orientation. the mean calculated crystalline size (d) for the deposited nanostructure was determined to be approximately 36 nm. a surface-sensitive spectroscopic method (xps) was used to determine the various elements present in a material (also known as its elemental composition), as well as their chemical state, general electronic structure, and density of their electronic states. the investigations about surface composition and chemical state of deposited mgo nanostructures using core-level light emission were reported and shown in fig. 3. it was clear from the survey scan (fig. 3a) that the deposited nanostructures were the mgo nanostructure during the synthesis process and no substantial pollutant was present in the sample. in the survey scan of the sample, the presence of carbon (c), oxygen (o), and magnesium (mg) elements and no major contaminant can be seen which validate by the elemental signals received. contamination of carbon was due to the environmental presence during the synthesis process which can be seen in fig. 3a. the mg 1s core level at 1302.8 ev is the peak with the highest intensity in the spectrum of deposited mgo nanostructure. the peak observed at 531.64 ev corresponds to o2− in the lattice of mgo. the core level spectra of mg2p were also shown in fig. 3d, where a gaussian peak of mgo at b.e. 50.91 ev was fitted using the casa xps software, and results indicate that the nanostructure of mgo was present with mg lattice, which also confirms the existence in the core level spectra of mg 1s (fig. 3b) and o 1s (fig. 3c) where mgo peak also present with lattice oxygen in the sample. the mg 2p peak analysis in fig. 3d demonstrates that mg remains in a single chemical state throughout the development process, and the characteristic b.e determines its oxidation. the binding energy of all peaks related to elemental composition with the electronic state in the survey scan from fig. 3(a) is tabulated as follows: scanning electron micrograph (sem) analysis the sem micrographs of the deposited mgo nanostructured thin films were obtained and shown in fig. 4 together with the chemical elemental mapping. the inset table provides information about the elements which were found in the deposited nanostructure. the results indicate that the mgo nanostructure was synthesized with porous surface and deposited accurately by this method. as the number of porous was more on surface of deposited film than it would be easy for detecting the gas by increasing the amount of active area that is available for gas adsorption (liu et al. 2014; liu et al. 2016; musa et al. 2021). the chemical compositions of the deposited nanostructure thin film on ito substrate are also measured by edx detector which is inbuilt into sem. it is also evident that the nanostructure was adequately present in the form, which supports the xps results. uv-visible analysis the absorption spectra of the synthesized magnesium oxide nanostructure thin films were obtained in the range of 200 and 800 nm using uv-visible spectrometer. tauc's formula in equation (vi) was used to calculate the band gap of synthesized mgo nanostructure (tauc et al. 1966) where α, h, ν, c and eg are the absorption coefficient, plank’s constant, frequency of the incident photon, a constant, and the direct transition band gap respectively. the uv-visible spectra were shown in fig. 5, in which fig. (a) indicates the absorbance spectrum (b) represents tauc’s plot to determine the optical band gap while fig. (c) denotes the derivative of absorbance versus energy for verification of band gap and (d) transmittance spectrum for the deposited mgo nanostructure. the calculated band gap with the help of the above equation and extrapolation of the curve as shown in fig. 5(b) was found about 4.16 ev, which is less than the band gap of bulk magnesium oxide (7.8 ev) as reported by many authors (bilalbegovic et al. 2004; guney et al. 2018; egwunyenga et al. 2019; baghezza, 2019). the band gap was also verified by the derivative versus energy curve which has a peak at 4.2 ev as shown in fig. 5(c). the resultant curve was linear throughout a wide range of photon energy, showing that the deposited nanostructure was a direct transition material. the band gap of metal oxide nanostructure decreases due to presence of defect states, so these defectstates are responsible for the large difference in band gap energy. both nanoparticles and nanostructures exhibit the same trend in band gap energy fluctuation however, nanostructures have a lower band gap energy than nanoparticles of the same size because of increased lattice strain and a larger surface to volume ratio (abdullah et al. 2022). guney and iskenderoglu, (2018) found that the band gap of mgo nanostructures varied with thickness from 4.31 to 4.61 ev and that the band gaps were decreased as sample thickness increased. the reduction in band gap may be related to variations in the atomic distance with the rise in film thickness. tlili et al. (2021) studied the variation of band gap from 4.01 to 4.08 ev for different molar concentrations (0.05, 0.1, 0.15, 0.2 mol·l−1) of mg2+ ions by spray pyrolys is technique and reported that, as the molar concentration of mg2+ increases, the optical band gap decreases. ftir analysis ftir spectroscopy was used to detect the existence of organic or inorganic constituents in the deposited nanostructure, which was connected to various functional groups associated with specific absorbance peaks in the spectra. the ftir spectra of deposited mgo nanostructure thin film with transmission peaks ranging from 500 to 4000 cm-1 are shown in fig. 6. the peak obtained at 545 cm-1 indicates the stretching vibration of mgo. as a result of the chemicals used during the synthesis process, the sample also contained additional functional groups at various peaks corresponding to co2, -co, c-h and -oh, etc. electrical properties the electrical properties such as current-voltage (i–v) characteristics were measuredin vacuum and with hydrogen gas by keithley electrometer 6517a in the range from -3 volt to 3 voltat room temperature. this study provides detailed information about the electronic effects in presence of hydrogen gas on deposited mgo nanostructure thin film. the curve exhibits considerable nonlinearity compared to a thin mgo tunnel barrier. it can be seen from fig. 7 that in presence of hydrogen gas, the conductivity increases in forward bias as well as in reverse bias, which can be explained as the charge shift from hydrogen to the film structure because hydrogen acts like a donor element. this property of mgo offers useful information about gas sensing applications like hydrogen gas and also can be employed as hydrogen storage materials. a similar study has been reported for mg/ti bilayer thin films (jangid et al. 2021), mg-ni thin films (jangid and jangid, 2022) and for cdte/mn bilayer thin films (nehra et al. 2009) that show the hydrogen storage properties of these bilayer thin films. a stainless-steel sealed chamber containing the synthesized sample was usedto measurecurrent-voltage characteristics while exposed to h2 gas in vacuum. the block diagram and pci/pct set up sown in fig. 8. the resistance response of synthesized mgo thin film was converted into a sensitivity value using equation (vii) (moumen et al. 2019; musa et al. 2021). where r0 stands for the film's resistance in vacuum, and rg for its resistance after being exposed to h2 gas. using equation (vii), the mgo nanostructure's sensitivity response to h2 gas was estimated to be about 31%. conclusion the mgo nanostructure thin film was synthesized on ito-coated glass substrate at room temperature by a simplified electrodeposition method using aqueous solution of magnesium nitrate and investigated by different characterization techniques. a cubic structure of mgo with a predicted crystalline size of about 36 nm was calculated by xrd investigation. the sem-edx image confirms the porous structure, adherent to the substrate and atomic % of available elements in the deposited mgo nanostructure thin films. the elemental composition and chemical states with binding energy were obtained using xps. the uv-visible analysis confirmed the optical band gap of the deposited nanostructure was ~ 4.16 ev. the i-v characteristics of deposited nanostructure suggest the partial semiconductor nature and the conductivity increases in presence of hydrogen. the sensitivity response of deposited nanostructure was approximately 31% on exposure to h2 gas. the deposited mgo nanostructures provide useful information about gas sensing applications such as hydrogen gas and also can be employed as hydrogen storage materials. the ultrafine nanostructures (such as qds etc.) provide a large and sensitive surface area for a promising solution to decrease the operating temperature for metal oxide semiconductor-based gas sensors (liu et al. 2014; liu et al. 2016). their high surface energy allows for the absorption of gas molecules even at room temperature for the sensing application. acknowledgement this research work was performed in dept. of physics, university of rajasthan, jaipur, india. the author is high thanks to the director cncer, university of rajasthan, jaipur, rajasthan india for providing characterization facilities. references abdullah bj (2022), size effect of band gap in semiconductor nanocrystals and nanostructures from density functional theory within hse06, materials science in semiconductor processing, 137: 106214. doi: 10.1016/j.mssp.2021.106214. abramishvili m, akhvlediani z, galustashvili m, dekanozishvili g, kalabegishvili t, kvatchadze v and tavkhelidze v (2011), peculiarities of radiation effects in mgo: mn2+ crystals, journalof modern physics 2: 841–844. doi:10.4236/jmp.2011.28099. alsultany fh, ahmed nm and matjafri mz (2014), effects of cw co2 laser annealing on indium tin oxide thin films characteristics, soft nanoscience letters 4(04): 83. doi: 10.4236/snl.2014.44012. ashok c, rao kv, chakra cs and rao kg (2016), mgo nanoparticles prepared by microwave-irradiation technique and its seed germination application, nano trends: a journal of nanotechnology and its application 18: 10-17. doi: 10.3390/nano11113076 baghezza mohammad (2019), optical and electrical properties of mgo thin films. khider university, m. l. b. m. m, http://a rchives. univbiskra. dz/ handle/ 123456 789/13780. bilalbegovic, g. 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omotoso e, lal c, makinde wo, ogundele kt, ajenifuja e, lasisi ar, eleruja ma and mola gt (2014), xps and some surface characterizations of electrodeposited mgo nanostructure, surfaceand interface analysis 46: 372-377. doi: 10.1002/sia.5425 tauc j, grigorovici r and vancu a (1966), optical properties and electronic structure of amorphous germanium, basic solid-state physics 15: 627-637. doi: 10.1002/pssb.19660150224. tlili m, nefzi c, alhalaili b, bouzidi c, ajilil, jebbari n and turki kamoun n (2021), synthesis and characterization of mgo thin films obtained by spray technique for optoelectronic applications, nanomaterials 11(11): 3076 (1-15). doi: 10.3390/nano11113076. wang x, feng j, bai y, zhang q and yin y (2016), synthesis, properties, and applications of hollow micro-/nanostructures, chemical reviews 116: 10983-11060. doi: 10.1021/ acs.chemrev.5b00731 wang x and xue d (2006), direct observation of the shape evolution of mgo whiskers in a solution system, materialsletters 60: 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properties, in proceedings of the ieee symposium on industrial electronics and applications, langkawi, malaysia, pp 468-471. doi: 10.1109/isiea.2011.6108754. fig. 3. (a) survey scan of deposited mgo nanostructure and core level of (b) mg 1s (c) o 1s (d) mg 2p lal, kumar, chawla, sharma and lal 123 mgo was known asa low-cost and environment-friendly material that has so many applications like bioresorbable materials that dissolve in biofluids (huang, 2018), drug delivery (ravaei et al. 2019), electrodes in pharmaceuticals and human fluids (kairya et al. 2017), resistive switching (guo et al. 2019), luminescence (nikiforov et al. 2016), photo-catalytic properties (demirci et al. 2015) and ultra-violet (uv) photodetector (zhou et al. 2019). mgo nanostructures have also been reported to exhibit thermoluminescence (abramishvili et al. 2011), radioluminescence (skvortsova and trinkler 2009), and electroluminescence (benia et al. 2007). thin metal oxide films that are electrically insulating are a crucial component of many different technologies, so magnesium oxide (mgo) has received a lot of attention for applicationssuch as spintronic devices since it has a material with a reasonably high dielectric constant. under the influence of uv light, methyl orange, and methylene blue dyes were degraded using the photocatalytic activity of mgo nanoparticles (mageshwari et al. 2013). hydrogen storage properties of mg/ti bilayer thin films were reported (jangid et al. 2021) at a different hydrogen pressure of 15 to 45 psi to realize the effect of hydrogenation. hydrogen is the lightest element in the universe, which is typical to detect and magnesium is very sensitive to hydrogen in comparison to other metals. (chawla et al. 2022). although magnesium (mg) is one of the better aspects for absorbing hydrogen, difficult to use this material for mobile applications due to its slow dynamics and need for high temperatures during dehydrogenation. due to its extremely large reversible hydrogen capacity, magnesium hydride is particularly intriguing (jangid et al. 2021). the present work reports the electrical behaviour and sensitivity of magnesium oxide (mgo) asa sensor to sense h2 gas. in a similar work dip-coated cuo thin films were used to investigate the gas-sensing response of co2 vapor in air at room temperature and reported that the physical qualities that can be altered have a lot of potential for co2 gas-sensing applications. (musa et al. 2021). for the synthesis of thin films with nanostructures, an easy, affordable, and solution-based hybrid method is electro-deposition. mgo nanostructures have been grown successfully from an aqueous solution of magnesium nitrate mg(no3)2 using the electrodeposition method (taleatu et al. 2014). the deposition procedure can be applied to a variety of conductive substrates, including polymers, semiconductors and ito-coated glass. indium tin oxide (ito) is the most widely used substrate because of its outstanding transparency to visible light and high electric conductivity (muchuweni et al. 2017). in the present work, magnesium oxide nanostructure thin film deposited by electrode position technique using magnesium nitrate solution. to synthesize mgo nanostructure, a variety of experimental procedures have been proposed, including reactive sputtering (choi and kim 2004), metal-organic molecular beam epitaxy (niu et al. 2000), chemical vapor deposition (carta et al. 2007), sol-gel (zulkefle et al. 2011), and pulsed laser deposition (kaneko et al. 2013). materials and methods a conventional homemade two-electrode electrochemical bathsetup with labelled diagram shown in fig. 1(b) was used in which graphite sheet was used as a counter electrode and ito coated glass substrate as a working electrode. both electrodes were introduced in the bath through two steel tubes. the electrolyte solution of 0.25 m concentration was prepared using magnesium nitrate mg(no3)2 salt. before the deposition process, the ito-coated glass substrate was extensively cleaned in an ultrasonic bath and rinsed with ultrapure water prior to the deposition in order to remove any surface impurities. by applying a potential difference of 2.5 v at room temperature for 30 minutes by htc power supply dc 3002, a thin layer of mgo nanostructures was deposited on ito substrate. the deposited sample was dehydrated up to 350oc at a heating rate of 10oc/min in a furnace shown in fig. 1(c) and hold for 90 minutes and thencooled at natural/normal atmosphere conditions, finally, mgo nanostructure was formed. characterization of the nanostructure shimadzu uv-2600 uv-visible spectrometer was used to analyze the optical characteristics, and fourier transform infrared spectrometer (ftir) bruker alpha was used to collect data about various functional groups present in the samplein the range 4000–500 cm-1. the structural and morphological characterization of the deposited nanostructure thin films was characterized by x-ray diffraction (xrd, model: a siemens d-5000 x-ray diffractometer) using cu-kα [1.54å] radiation. the kinetic energy distribution of photoelectrons released from the specimen material was measured using x-ray photoemission spectroscopy (model: omicron esca (electron spectroscope for chemical analysis) oxford instrument germany). in this model aluminium anode was used for samplesthat have energy 1486.7 ev. sem (model: jsm-7610f plus & make: jeol) was used to analyze the surface morphology and microstructure of deposited mgo nanostructures. the i-v characteristics for hydrogensensing were measured by using a keithley electrometer 6517a and a pressure-composition-isotherm (pci) setupat vacuum (1 *10-3 mbar) and by introducing hydrogen (at 5 bar) in the stainless-steel chamber. results and discussion following equations (i-iv) show the overall chemical reaction for the deposition of mgo nanostructure thin film using magnesium nitrate salt in aquas medium (hashaikeh and szpunar 2009). x-ray diffraction (xrd) analysis diffraction measurement was carried out with an angular scanning range of (20° – 80°) to explore the nature of the material, purity, and crystallinity of the sample. fig. 2 shows the xrd pattern of synthesized nanostructure thin films. in fig. 2, spectrum (a) shows xrd pattern of theusedito substrate, (b) shows the xrd pattern of thin film before annealing and (c) shows the xrd pattern of thin film after annealing. as discussed in equation (iii) and (iv) the xrd pattern represented by fig. 2(b) for mg(oh)2 and fig. 2(c) for mgo. the substrate peak marked by (*) is visible after post annealing at 350°c when conversion of mg(oh)2 into mgo nanostructure at ito substrate (alsultany et al. 2014). fig. 2(c) has distinctive sharp peaks correspond to (111), (200), (220) and (222) planes related to fcc structure (cvetkovic et al. 2018). the sharp peaks illustrate that the synthesized nanostructure has a good crystalline nature. the debye-scherrer equation (ashok et al. 2016) was used to compute the crystallite size d (nm). where λ, β, and 2θ were the wavelength of the incident x-ray beam (cu kα1.54 å), full width at half maximum (fwhm) in radian and bragg’s diffraction angle of the preferred orientation. the mean calculated crystalline size (d) for the deposited nanostructure was determined to be approximately 36 nm. a surface-sensitive spectroscopic method (xps) was used to determine the various elements present in a material (also known as its elemental composition), as well as their chemical state, general electronic structure, and density of their electronic states. the investigations about surface composition and chemical state of deposited mgo nanostructures using core-level light emission were reported and shown in fig. 3. it was clear from the survey scan (fig. 3a) that the deposited nanostructures were the mgo nanostructure during the synthesis process and no substantial pollutant was present in the sample. in the survey scan of the sample, the presence of carbon (c), oxygen (o), and magnesium (mg) elements and no major contaminant can be seen which validate by the elemental signals received. contamination of carbon was due to the environmental presence during the synthesis process which can be seen in fig. 3a. the mg 1s core level at 1302.8 ev is the peak with the highest intensity in the spectrum of deposited mgo nanostructure. the peak observed at 531.64 ev corresponds to o2− in the lattice of mgo. the core level spectra of mg2p were also shown in fig. 3d, where a gaussian peak of mgo at b.e. 50.91 ev was fitted using the casa xps software, and results indicate that the nanostructure of mgo was present with mg lattice, which also confirms the existence in the core level spectra of mg 1s (fig. 3b) and o 1s (fig. 3c) where mgo peak also present with lattice oxygen in the sample. the mg 2p peak analysis in fig. 3d demonstrates that mg remains in a single chemical state throughout the development process, and the characteristic b.e determines its oxidation. the binding energy of all peaks related to elemental composition with the electronic state in the survey scan from fig. 3(a) is tabulated as follows: scanning electron micrograph (sem) analysis the sem micrographs of the deposited mgo nanostructured thin films were obtained and shown in fig. 4 together with the chemical elemental mapping. the inset table provides information about the elements which were found in the deposited nanostructure. the results indicate that the mgo nanostructure was synthesized with porous surface and deposited accurately by this method. as the number of porous was more on surface of deposited film than it would be easy for detecting the gas by increasing the amount of active area that is available for gas adsorption (liu et al. 2014; liu et al. 2016; musa et al. 2021). the chemical compositions of the deposited nanostructure thin film on ito substrate are also measured by edx detector which is inbuilt into sem. it is also evident that the nanostructure was adequately present in the form, which supports the xps results. uv-visible analysis the absorption spectra of the synthesized magnesium oxide nanostructure thin films were obtained in the range of 200 and 800 nm using uv-visible spectrometer. tauc's formula in equation (vi) was used to calculate the band gap of synthesized mgo nanostructure (tauc et al. 1966) where α, h, ν, c and eg are the absorption coefficient, plank’s constant, frequency of the incident photon, a constant, and the direct transition band gap respectively. the uv-visible spectra were shown in fig. 5, in which fig. (a) indicates the absorbance spectrum (b) represents tauc’s plot to determine the optical band gap while fig. (c) denotes the derivative of absorbance versus energy for verification of band gap and (d) transmittance spectrum for the deposited mgo nanostructure. the calculated band gap with the help of the above equation and extrapolation of the curve as shown in fig. 5(b) was found about 4.16 ev, which is less than the band gap of bulk magnesium oxide (7.8 ev) as reported by many authors (bilalbegovic et al. 2004; guney et al. 2018; egwunyenga et al. 2019; baghezza, 2019). the band gap was also verified by the derivative versus energy curve which has a peak at 4.2 ev as shown in fig. 5(c). the resultant curve was linear throughout a wide range of photon energy, showing that the deposited nanostructure was a direct transition material. the band gap of metal oxide nanostructure decreases due to presence of defect states, so these defectstates are responsible for the large difference in band gap energy. both nanoparticles and nanostructures exhibit the same trend in band gap energy fluctuation however, nanostructures have a lower band gap energy than nanoparticles of the same size because of increased lattice strain and a larger surface to volume ratio (abdullah et al. 2022). guney and iskenderoglu, (2018) found that the band gap of mgo nanostructures varied with thickness from 4.31 to 4.61 ev and that the band gaps were decreased as sample thickness increased. the reduction in band gap may be related to variations in the atomic distance with the rise in film thickness. tlili et al. (2021) studied the variation of band gap from 4.01 to 4.08 ev for different molar concentrations (0.05, 0.1, 0.15, 0.2 mol·l−1) of mg2+ ions by spray pyrolys is technique and reported that, as the molar concentration of mg2+ increases, the optical band gap decreases. ftir analysis ftir spectroscopy was used to detect the existence of organic or inorganic constituents in the deposited nanostructure, which was connected to various functional groups associated with specific absorbance peaks in the spectra. the ftir spectra of deposited mgo nanostructure thin film with transmission peaks ranging from 500 to 4000 cm-1 are shown in fig. 6. the peak obtained at 545 cm-1 indicates the stretching vibration of mgo. as a result of the chemicals used during the synthesis process, the sample also contained additional functional groups at various peaks corresponding to co2, -co, c-h and -oh, etc. electrical properties the electrical properties such as current-voltage (i–v) characteristics were measuredin vacuum and with hydrogen gas by keithley electrometer 6517a in the range from -3 volt to 3 voltat room temperature. this study provides detailed information about the electronic effects in presence of hydrogen gas on deposited mgo nanostructure thin film. the curve exhibits considerable nonlinearity compared to a thin mgo tunnel barrier. it can be seen from fig. 7 that in presence of hydrogen gas, the conductivity increases in forward bias as well as in reverse bias, which can be explained as the charge shift from hydrogen to the film structure because hydrogen acts like a donor element. this property of mgo offers useful information about gas sensing applications like hydrogen gas and also can be employed as hydrogen storage materials. a similar study has been reported for mg/ti bilayer thin films (jangid et al. 2021), mg-ni thin films (jangid and jangid, 2022) and for cdte/mn bilayer thin films (nehra et al. 2009) that show the hydrogen storage properties of these bilayer thin films. a stainless-steel sealed chamber containing the synthesized sample was usedto measurecurrent-voltage characteristics while exposed to h2 gas in vacuum. the block diagram and pci/pct set up sown in fig. 8. the resistance response of synthesized mgo thin film was converted into a sensitivity value using equation (vii) (moumen et al. 2019; musa et al. 2021). where r0 stands for the film's resistance in vacuum, and rg for its resistance after being exposed to h2 gas. using equation (vii), the mgo nanostructure's sensitivity response to h2 gas was estimated to be about 31%. conclusion the mgo nanostructure thin film was synthesized on ito-coated glass substrate at room temperature by a simplified electrodeposition method using aqueous solution of magnesium nitrate and investigated by different characterization techniques. a cubic structure of mgo with a predicted crystalline size of about 36 nm was calculated by xrd investigation. the sem-edx image confirms the porous structure, adherent to the substrate and atomic % of available elements in the deposited mgo nanostructure thin films. the elemental composition and chemical states with binding energy were obtained using xps. the uv-visible analysis confirmed the optical band gap of the deposited nanostructure was ~ 4.16 ev. the i-v characteristics of deposited nanostructure suggest the partial semiconductor nature and the conductivity increases in presence of hydrogen. the sensitivity response of deposited nanostructure was approximately 31% on exposure to h2 gas. the deposited mgo nanostructures provide useful information about gas sensing applications such as hydrogen gas and also can be employed as hydrogen storage materials. the ultrafine nanostructures (such as qds etc.) provide a large and sensitive surface area for a promising solution to decrease the operating temperature for metal oxide semiconductor-based gas sensors (liu et al. 2014; liu et al. 2016). their high surface energy allows for the absorption of gas molecules even at room temperature for the sensing application. acknowledgement this research work was performed in dept. of physics, university of rajasthan, jaipur, india. the author is high thanks to the director cncer, university of rajasthan, jaipur, rajasthan india for providing characterization facilities. references abdullah bj (2022), size effect of band gap in semiconductor nanocrystals and nanostructures from density functional theory within hse06, materials science in semiconductor processing, 137: 106214. doi: 10.1016/j.mssp.2021.106214. abramishvili m, akhvlediani z, galustashvili m, dekanozishvili g, kalabegishvili t, kvatchadze v and tavkhelidze v (2011), peculiarities of radiation effects in mgo: mn2+ crystals, journalof modern physics 2: 841–844. doi:10.4236/jmp.2011.28099. alsultany fh, ahmed nm and matjafri mz (2014), effects of cw co2 laser annealing on indium tin oxide thin films characteristics, soft nanoscience letters 4(04): 83. doi: 10.4236/snl.2014.44012. ashok c, rao kv, chakra cs and rao kg (2016), mgo nanoparticles prepared by microwave-irradiation technique and its seed germination application, nano trends: a journal of nanotechnology and its application 18: 10-17. doi: 10.3390/nano11113076 baghezza mohammad (2019), optical and electrical properties of mgo thin films. khider university, m. l. b. m. m, http://a rchives. univbiskra. dz/ handle/ 123456 789/13780. bilalbegovic, g. 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omotoso e, lal c, makinde wo, ogundele kt, ajenifuja e, lasisi ar, eleruja ma and mola gt (2014), xps and some surface characterizations of electrodeposited mgo nanostructure, surfaceand interface analysis 46: 372-377. doi: 10.1002/sia.5425 tauc j, grigorovici r and vancu a (1966), optical properties and electronic structure of amorphous germanium, basic solid-state physics 15: 627-637. doi: 10.1002/pssb.19660150224. tlili m, nefzi c, alhalaili b, bouzidi c, ajilil, jebbari n and turki kamoun n (2021), synthesis and characterization of mgo thin films obtained by spray technique for optoelectronic applications, nanomaterials 11(11): 3076 (1-15). doi: 10.3390/nano11113076. wang x, feng j, bai y, zhang q and yin y (2016), synthesis, properties, and applications of hollow micro-/nanostructures, chemical reviews 116: 10983-11060. doi: 10.1021/ acs.chemrev.5b00731 wang x and xue d (2006), direct observation of the shape evolution of mgo whiskers in a solution system, materialsletters 60: 3160-3164. doi: 10.1016/j.matlet.2006.02.066 weber j, singhal r, zekri s and kumar a (2008), one-dimensional nanostructures: fabrication, characterisation and applications, international materials review 53(4): 235-255. doi: 10.1179/174328008x348183 yourdkhani a and caruntu g (2011), highly ordered transition metal ferrite nanotube arrays synthesized by template-assisted liquid phase deposition, journal of material chemistry 21: 7145-7153. doi: 10.1039/c0jm04441e zhou c, ali q, chen x, gao x, liu k and shen d (2019), ultraviolet photodetectors based on wide bandgap oxide semiconductor films, chinese physics b 28: 048503. doi: 10.1088/1674-1056/28/4/048503 zou g, chen w, liu r and xu z (2008), morphology-tunable synthesis and characterizations of mg(oh)2 films via a cathodic electrochemical process, materials chemistry and physics 107: 85-90. doi: 10.1016/j.matchemphys. 2007.06.046 zulkefle h, ismail ln, bakar ra and mahmood mr (2011), molar concentration effect on mgo thin films properties, in proceedings of the ieee symposium on industrial electronics and applications, langkawi, malaysia, pp 468-471. doi: 10.1109/isiea.2011.6108754. table 1. b.e. for different elements available in mgo nanostructure thin film elemental composition binding energy (ev) mg 1s 1302.8 o kll 976.23 o 1s 531.64 mg kll 304.64 c 1s 285.41 mg 2s 86.98 mg 2p 48.21 (αhν)2 = c(hν eg) (vi) fig. 4. micrograph of synthesized mgo with elemental mapping synthesis of mgo nanostructure thin films via electrodeposition method 58(2) 2023124 mgo was known asa low-cost and environment-friendly material that has so many applications like bioresorbable materials that dissolve in biofluids (huang, 2018), drug delivery (ravaei et al. 2019), electrodes in pharmaceuticals and human fluids (kairya et al. 2017), resistive switching (guo et al. 2019), luminescence (nikiforov et al. 2016), photo-catalytic properties (demirci et al. 2015) and ultra-violet (uv) photodetector (zhou et al. 2019). mgo nanostructures have also been reported to exhibit thermoluminescence (abramishvili et al. 2011), radioluminescence (skvortsova and trinkler 2009), and electroluminescence (benia et al. 2007). thin metal oxide films that are electrically insulating are a crucial component of many different technologies, so magnesium oxide (mgo) has received a lot of attention for applicationssuch as spintronic devices since it has a material with a reasonably high dielectric constant. under the influence of uv light, methyl orange, and methylene blue dyes were degraded using the photocatalytic activity of mgo nanoparticles (mageshwari et al. 2013). hydrogen storage properties of mg/ti bilayer thin films were reported (jangid et al. 2021) at a different hydrogen pressure of 15 to 45 psi to realize the effect of hydrogenation. hydrogen is the lightest element in the universe, which is typical to detect and magnesium is very sensitive to hydrogen in comparison to other metals. (chawla et al. 2022). although magnesium (mg) is one of the better aspects for absorbing hydrogen, difficult to use this material for mobile applications due to its slow dynamics and need for high temperatures during dehydrogenation. due to its extremely large reversible hydrogen capacity, magnesium hydride is particularly intriguing (jangid et al. 2021). the present work reports the electrical behaviour and sensitivity of magnesium oxide (mgo) asa sensor to sense h2 gas. in a similar work dip-coated cuo thin films were used to investigate the gas-sensing response of co2 vapor in air at room temperature and reported that the physical qualities that can be altered have a lot of potential for co2 gas-sensing applications. (musa et al. 2021). for the synthesis of thin films with nanostructures, an easy, affordable, and solution-based hybrid method is electro-deposition. mgo nanostructures have been grown successfully from an aqueous solution of magnesium nitrate mg(no3)2 using the electrodeposition method (taleatu et al. 2014). the deposition procedure can be applied to a variety of conductive substrates, including polymers, semiconductors and ito-coated glass. indium tin oxide (ito) is the most widely used substrate because of its outstanding transparency to visible light and high electric conductivity (muchuweni et al. 2017). in the present work, magnesium oxide nanostructure thin film deposited by electrode position technique using magnesium nitrate solution. to synthesize mgo nanostructure, a variety of experimental procedures have been proposed, including reactive sputtering (choi and kim 2004), metal-organic molecular beam epitaxy (niu et al. 2000), chemical vapor deposition (carta et al. 2007), sol-gel (zulkefle et al. 2011), and pulsed laser deposition (kaneko et al. 2013). materials and methods a conventional homemade two-electrode electrochemical bathsetup with labelled diagram shown in fig. 1(b) was used in which graphite sheet was used as a counter electrode and ito coated glass substrate as a working electrode. both electrodes were introduced in the bath through two steel tubes. the electrolyte solution of 0.25 m concentration was prepared using magnesium nitrate mg(no3)2 salt. before the deposition process, the ito-coated glass substrate was extensively cleaned in an ultrasonic bath and rinsed with ultrapure water prior to the deposition in order to remove any surface impurities. by applying a potential difference of 2.5 v at room temperature for 30 minutes by htc power supply dc 3002, a thin layer of mgo nanostructures was deposited on ito substrate. the deposited sample was dehydrated up to 350oc at a heating rate of 10oc/min in a furnace shown in fig. 1(c) and hold for 90 minutes and thencooled at natural/normal atmosphere conditions, finally, mgo nanostructure was formed. characterization of the nanostructure shimadzu uv-2600 uv-visible spectrometer was used to analyze the optical characteristics, and fourier transform infrared spectrometer (ftir) bruker alpha was used to collect data about various functional groups present in the samplein the range 4000–500 cm-1. the structural and morphological characterization of the deposited nanostructure thin films was characterized by x-ray diffraction (xrd, model: a siemens d-5000 x-ray diffractometer) using cu-kα [1.54å] radiation. the kinetic energy distribution of photoelectrons released from the specimen material was measured using x-ray photoemission spectroscopy (model: omicron esca (electron spectroscope for chemical analysis) oxford instrument germany). in this model aluminium anode was used for samplesthat have energy 1486.7 ev. sem (model: jsm-7610f plus & make: jeol) was used to analyze the surface morphology and microstructure of deposited mgo nanostructures. the i-v characteristics for hydrogensensing were measured by using a keithley electrometer 6517a and a pressure-composition-isotherm (pci) setupat vacuum (1 *10-3 mbar) and by introducing hydrogen (at 5 bar) in the stainless-steel chamber. results and discussion following equations (i-iv) show the overall chemical reaction for the deposition of mgo nanostructure thin film using magnesium nitrate salt in aquas medium (hashaikeh and szpunar 2009). x-ray diffraction (xrd) analysis diffraction measurement was carried out with an angular scanning range of (20° – 80°) to explore the nature of the material, purity, and crystallinity of the sample. fig. 2 shows the xrd pattern of synthesized nanostructure thin films. in fig. 2, spectrum (a) shows xrd pattern of theusedito substrate, (b) shows the xrd pattern of thin film before annealing and (c) shows the xrd pattern of thin film after annealing. as discussed in equation (iii) and (iv) the xrd pattern represented by fig. 2(b) for mg(oh)2 and fig. 2(c) for mgo. the substrate peak marked by (*) is visible after post annealing at 350°c when conversion of mg(oh)2 into mgo nanostructure at ito substrate (alsultany et al. 2014). fig. 2(c) has distinctive sharp peaks correspond to (111), (200), (220) and (222) planes related to fcc structure (cvetkovic et al. 2018). the sharp peaks illustrate that the synthesized nanostructure has a good crystalline nature. the debye-scherrer equation (ashok et al. 2016) was used to compute the crystallite size d (nm). where λ, β, and 2θ were the wavelength of the incident x-ray beam (cu kα1.54 å), full width at half maximum (fwhm) in radian and bragg’s diffraction angle of the preferred orientation. the mean calculated crystalline size (d) for the deposited nanostructure was determined to be approximately 36 nm. a surface-sensitive spectroscopic method (xps) was used to determine the various elements present in a material (also known as its elemental composition), as well as their chemical state, general electronic structure, and density of their electronic states. the investigations about surface composition and chemical state of deposited mgo nanostructures using core-level light emission were reported and shown in fig. 3. it was clear from the survey scan (fig. 3a) that the deposited nanostructures were the mgo nanostructure during the synthesis process and no substantial pollutant was present in the sample. in the survey scan of the sample, the presence of carbon (c), oxygen (o), and magnesium (mg) elements and no major contaminant can be seen which validate by the elemental signals received. contamination of carbon was due to the environmental presence during the synthesis process which can be seen in fig. 3a. the mg 1s core level at 1302.8 ev is the peak with the highest intensity in the spectrum of deposited mgo nanostructure. the peak observed at 531.64 ev corresponds to o2− in the lattice of mgo. the core level spectra of mg2p were also shown in fig. 3d, where a gaussian peak of mgo at b.e. 50.91 ev was fitted using the casa xps software, and results indicate that the nanostructure of mgo was present with mg lattice, which also confirms the existence in the core level spectra of mg 1s (fig. 3b) and o 1s (fig. 3c) where mgo peak also present with lattice oxygen in the sample. the mg 2p peak analysis in fig. 3d demonstrates that mg remains in a single chemical state throughout the development process, and the characteristic b.e determines its oxidation. the binding energy of all peaks related to elemental composition with the electronic state in the survey scan from fig. 3(a) is tabulated as follows: scanning electron micrograph (sem) analysis the sem micrographs of the deposited mgo nanostructured thin films were obtained and shown in fig. 4 together with the chemical elemental mapping. the inset table provides information about the elements which were found in the deposited nanostructure. the results indicate that the mgo nanostructure was synthesized with porous surface and deposited accurately by this method. as the number of porous was more on surface of deposited film than it would be easy for detecting the gas by increasing the amount of active area that is available for gas adsorption (liu et al. 2014; liu et al. 2016; musa et al. 2021). the chemical compositions of the deposited nanostructure thin film on ito substrate are also measured by edx detector which is inbuilt into sem. it is also evident that the nanostructure was adequately present in the form, which supports the xps results. uv-visible analysis the absorption spectra of the synthesized magnesium oxide nanostructure thin films were obtained in the range of 200 and 800 nm using uv-visible spectrometer. tauc's formula in equation (vi) was used to calculate the band gap of synthesized mgo nanostructure (tauc et al. 1966) where α, h, ν, c and eg are the absorption coefficient, plank’s constant, frequency of the incident photon, a constant, and the direct transition band gap respectively. the uv-visible spectra were shown in fig. 5, in which fig. (a) indicates the absorbance spectrum (b) represents tauc’s plot to determine the optical band gap while fig. (c) denotes the derivative of absorbance versus energy for verification of band gap and (d) transmittance spectrum for the deposited mgo nanostructure. the calculated band gap with the help of the above equation and extrapolation of the curve as shown in fig. 5(b) was found about 4.16 ev, which is less than the band gap of bulk magnesium oxide (7.8 ev) as reported by many authors (bilalbegovic et al. 2004; guney et al. 2018; egwunyenga et al. 2019; baghezza, 2019). the band gap was also verified by the derivative versus energy curve which has a peak at 4.2 ev as shown in fig. 5(c). the resultant curve was linear throughout a wide range of photon energy, showing that the deposited nanostructure was a direct transition material. the band gap of metal oxide nanostructure decreases due to presence of defect states, so these defectstates are responsible for the large difference in band gap energy. both nanoparticles and nanostructures exhibit the same trend in band gap energy fluctuation however, nanostructures have a lower band gap energy than nanoparticles of the same size because of increased lattice strain and a larger surface to volume ratio (abdullah et al. 2022). guney and iskenderoglu, (2018) found that the band gap of mgo nanostructures varied with thickness from 4.31 to 4.61 ev and that the band gaps were decreased as sample thickness increased. the reduction in band gap may be related to variations in the atomic distance with the rise in film thickness. tlili et al. (2021) studied the variation of band gap from 4.01 to 4.08 ev for different molar concentrations (0.05, 0.1, 0.15, 0.2 mol·l−1) of mg2+ ions by spray pyrolys is technique and reported that, as the molar concentration of mg2+ increases, the optical band gap decreases. ftir analysis ftir spectroscopy was used to detect the existence of organic or inorganic constituents in the deposited nanostructure, which was connected to various functional groups associated with specific absorbance peaks in the spectra. the ftir spectra of deposited mgo nanostructure thin film with transmission peaks ranging from 500 to 4000 cm-1 are shown in fig. 6. the peak obtained at 545 cm-1 indicates the stretching vibration of mgo. as a result of the chemicals used during the synthesis process, the sample also contained additional functional groups at various peaks corresponding to co2, -co, c-h and -oh, etc. electrical properties the electrical properties such as current-voltage (i–v) characteristics were measuredin vacuum and with hydrogen gas by keithley electrometer 6517a in the range from -3 volt to 3 voltat room temperature. this study provides detailed information about the electronic effects in presence of hydrogen gas on deposited mgo nanostructure thin film. the curve exhibits considerable nonlinearity compared to a thin mgo tunnel barrier. it can be seen from fig. 7 that in presence of hydrogen gas, the conductivity increases in forward bias as well as in reverse bias, which can be explained as the charge shift from hydrogen to the film structure because hydrogen acts like a donor element. this property of mgo offers useful information about gas sensing applications like hydrogen gas and also can be employed as hydrogen storage materials. a similar study has been reported for mg/ti bilayer thin films (jangid et al. 2021), mg-ni thin films (jangid and jangid, 2022) and for cdte/mn bilayer thin films (nehra et al. 2009) that show the hydrogen storage properties of these bilayer thin films. a stainless-steel sealed chamber containing the synthesized sample was usedto measurecurrent-voltage characteristics while exposed to h2 gas in vacuum. the block diagram and pci/pct set up sown in fig. 8. the resistance response of synthesized mgo thin film was converted into a sensitivity value using equation (vii) (moumen et al. 2019; musa et al. 2021). where r0 stands for the film's resistance in vacuum, and rg for its resistance after being exposed to h2 gas. using equation (vii), the mgo nanostructure's sensitivity response to h2 gas was estimated to be about 31%. conclusion the mgo nanostructure thin film was synthesized on ito-coated glass substrate at room temperature by a simplified electrodeposition method using aqueous solution of magnesium nitrate and investigated by different characterization techniques. a cubic structure of mgo with a predicted crystalline size of about 36 nm was calculated by xrd investigation. the sem-edx image confirms the porous structure, adherent to the substrate and atomic % of available elements in the deposited mgo nanostructure thin films. the elemental composition and chemical states with binding energy were obtained using xps. the uv-visible analysis confirmed the optical band gap of the deposited nanostructure was ~ 4.16 ev. the i-v characteristics of deposited nanostructure suggest the partial semiconductor nature and the conductivity increases in presence of hydrogen. the sensitivity response of deposited nanostructure was approximately 31% on exposure to h2 gas. the deposited mgo nanostructures provide useful information about gas sensing applications such as hydrogen gas and also can be employed as hydrogen storage materials. the ultrafine nanostructures (such as qds etc.) provide a large and sensitive surface area for a promising solution to decrease the operating temperature for metal oxide semiconductor-based gas sensors (liu et al. 2014; liu et al. 2016). their high surface energy allows for the absorption of gas molecules even at room temperature for the sensing application. acknowledgement this research work was performed in dept. of physics, university of rajasthan, jaipur, india. the author is high thanks to the director cncer, university of rajasthan, jaipur, rajasthan india for providing characterization facilities. references abdullah bj (2022), size effect of band gap in semiconductor nanocrystals and nanostructures from density functional theory within hse06, materials science in semiconductor processing, 137: 106214. doi: 10.1016/j.mssp.2021.106214. abramishvili m, akhvlediani z, galustashvili m, dekanozishvili g, kalabegishvili t, kvatchadze v and tavkhelidze v (2011), peculiarities of radiation effects in mgo: mn2+ crystals, journalof modern physics 2: 841–844. doi:10.4236/jmp.2011.28099. alsultany fh, ahmed nm and matjafri mz (2014), effects of cw co2 laser annealing on indium tin oxide thin films characteristics, soft nanoscience letters 4(04): 83. doi: 10.4236/snl.2014.44012. ashok c, rao kv, chakra cs and rao kg (2016), mgo nanoparticles prepared by microwave-irradiation technique and its seed germination application, nano trends: a journal of nanotechnology and its application 18: 10-17. doi: 10.3390/nano11113076 baghezza mohammad (2019), optical and electrical properties of mgo thin films. khider university, m. l. b. m. m, http://a rchives. univbiskra. dz/ handle/ 123456 789/13780. bilalbegovic, g. 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nikiforov sv, kortov vs and petrov mo (2016), luminescent and dosimetric properties of ultrafine magnesium oxide ceramics after high dose irradiation, radiationmeasurements 90: 252-256. doi: 10.1016/j.radmeas. 2015.12.018 niu f, hoerman bh and wessels bw (2000), metalorganic molecular beam epitaxy of magnesium oxide on silicon, mrs online proceedings library 619: 149-154. doi: 10.1557/proc-619-149. ravaei i, haghighat m and azami sm (2019), a dft, aim and nbo study of isoniazid drug delivery by mgo nanocage, applied surface science 469: 103-112. doi: 10.1016/j. apsusc.2018.11.005 shinji y, taro n, akio f, yoshishige s and koji a (2004), giant room-temperature magnetoresistance in single-crystal fe/mgo/fe magnetic tunnel junctions, nature materials 3: 868-871. doi:10.1038/nmat1257 skvortsova v and trinkler l (2009), luminescence of impurity and radiation defects in magnesium oxide irradiated by fast neutrons, physics procedia 2: 567-570. doi: 10.1016/j. phpro.2009.07.042 taleatu ba, omotoso e, lal c, makinde wo, ogundele kt, ajenifuja e, lasisi ar, eleruja ma and mola gt (2014), xps and some surface characterizations of electrodeposited mgo nanostructure, surfaceand interface analysis 46: 372-377. doi: 10.1002/sia.5425 tauc j, grigorovici r and vancu a (1966), optical properties and electronic structure of amorphous germanium, basic solid-state physics 15: 627-637. doi: 10.1002/pssb.19660150224. tlili m, nefzi c, alhalaili b, bouzidi c, ajilil, jebbari n and turki kamoun n (2021), synthesis and characterization of mgo thin films obtained by spray technique for optoelectronic applications, nanomaterials 11(11): 3076 (1-15). doi: 10.3390/nano11113076. wang x, feng j, bai y, zhang q and yin y (2016), synthesis, properties, and applications of hollow micro-/nanostructures, chemical reviews 116: 10983-11060. doi: 10.1021/ acs.chemrev.5b00731 wang x and xue d (2006), direct observation of the shape evolution of mgo whiskers in a solution system, materialsletters 60: 3160-3164. doi: 10.1016/j.matlet.2006.02.066 weber j, singhal r, zekri s and kumar a (2008), one-dimensional nanostructures: fabrication, characterisation and applications, international materials review 53(4): 235-255. doi: 10.1179/174328008x348183 yourdkhani a and caruntu g (2011), highly ordered transition metal ferrite nanotube arrays synthesized by template-assisted liquid phase deposition, journal of material chemistry 21: 7145-7153. doi: 10.1039/c0jm04441e zhou c, ali q, chen x, gao x, liu k and shen d (2019), ultraviolet photodetectors based on wide bandgap oxide semiconductor films, chinese physics b 28: 048503. doi: 10.1088/1674-1056/28/4/048503 zou g, chen w, liu r and xu z (2008), morphology-tunable synthesis and characterizations of mg(oh)2 films via a cathodic electrochemical process, materials chemistry and physics 107: 85-90. doi: 10.1016/j.matchemphys. 2007.06.046 zulkefle h, ismail ln, bakar ra and mahmood mr (2011), molar concentration effect on mgo thin films properties, in proceedings of the ieee symposium on industrial electronics and applications, langkawi, malaysia, pp 468-471. doi: 10.1109/isiea.2011.6108754. fig. 5. uv-visible spectra of synthesized mgo thin film(a) absorbance spectrum (b) tauc’s plot (c) derivative of absorbance versus energy (d) transmittance spectrum fig. 6. ftir spectra of synthesized mgo nanostructure lal, kumar, chawla, sharma and lal 125 mgo was known asa low-cost and environment-friendly material that has so many applications like bioresorbable materials that dissolve in biofluids (huang, 2018), drug delivery (ravaei et al. 2019), electrodes in pharmaceuticals and human fluids (kairya et al. 2017), resistive switching (guo et al. 2019), luminescence (nikiforov et al. 2016), photo-catalytic properties (demirci et al. 2015) and ultra-violet (uv) photodetector (zhou et al. 2019). mgo nanostructures have also been reported to exhibit thermoluminescence (abramishvili et al. 2011), radioluminescence (skvortsova and trinkler 2009), and electroluminescence (benia et al. 2007). thin metal oxide films that are electrically insulating are a crucial component of many different technologies, so magnesium oxide (mgo) has received a lot of attention for applicationssuch as spintronic devices since it has a material with a reasonably high dielectric constant. under the influence of uv light, methyl orange, and methylene blue dyes were degraded using the photocatalytic activity of mgo nanoparticles (mageshwari et al. 2013). hydrogen storage properties of mg/ti bilayer thin films were reported (jangid et al. 2021) at a different hydrogen pressure of 15 to 45 psi to realize the effect of hydrogenation. hydrogen is the lightest element in the universe, which is typical to detect and magnesium is very sensitive to hydrogen in comparison to other metals. (chawla et al. 2022). although magnesium (mg) is one of the better aspects for absorbing hydrogen, difficult to use this material for mobile applications due to its slow dynamics and need for high temperatures during dehydrogenation. due to its extremely large reversible hydrogen capacity, magnesium hydride is particularly intriguing (jangid et al. 2021). the present work reports the electrical behaviour and sensitivity of magnesium oxide (mgo) asa sensor to sense h2 gas. in a similar work dip-coated cuo thin films were used to investigate the gas-sensing response of co2 vapor in air at room temperature and reported that the physical qualities that can be altered have a lot of potential for co2 gas-sensing applications. (musa et al. 2021). for the synthesis of thin films with nanostructures, an easy, affordable, and solution-based hybrid method is electro-deposition. mgo nanostructures have been grown successfully from an aqueous solution of magnesium nitrate mg(no3)2 using the electrodeposition method (taleatu et al. 2014). the deposition procedure can be applied to a variety of conductive substrates, including polymers, semiconductors and ito-coated glass. indium tin oxide (ito) is the most widely used substrate because of its outstanding transparency to visible light and high electric conductivity (muchuweni et al. 2017). in the present work, magnesium oxide nanostructure thin film deposited by electrode position technique using magnesium nitrate solution. to synthesize mgo nanostructure, a variety of experimental procedures have been proposed, including reactive sputtering (choi and kim 2004), metal-organic molecular beam epitaxy (niu et al. 2000), chemical vapor deposition (carta et al. 2007), sol-gel (zulkefle et al. 2011), and pulsed laser deposition (kaneko et al. 2013). materials and methods a conventional homemade two-electrode electrochemical bathsetup with labelled diagram shown in fig. 1(b) was used in which graphite sheet was used as a counter electrode and ito coated glass substrate as a working electrode. both electrodes were introduced in the bath through two steel tubes. the electrolyte solution of 0.25 m concentration was prepared using magnesium nitrate mg(no3)2 salt. before the deposition process, the ito-coated glass substrate was extensively cleaned in an ultrasonic bath and rinsed with ultrapure water prior to the deposition in order to remove any surface impurities. by applying a potential difference of 2.5 v at room temperature for 30 minutes by htc power supply dc 3002, a thin layer of mgo nanostructures was deposited on ito substrate. the deposited sample was dehydrated up to 350oc at a heating rate of 10oc/min in a furnace shown in fig. 1(c) and hold for 90 minutes and thencooled at natural/normal atmosphere conditions, finally, mgo nanostructure was formed. characterization of the nanostructure shimadzu uv-2600 uv-visible spectrometer was used to analyze the optical characteristics, and fourier transform infrared spectrometer (ftir) bruker alpha was used to collect data about various functional groups present in the samplein the range 4000–500 cm-1. the structural and morphological characterization of the deposited nanostructure thin films was characterized by x-ray diffraction (xrd, model: a siemens d-5000 x-ray diffractometer) using cu-kα [1.54å] radiation. the kinetic energy distribution of photoelectrons released from the specimen material was measured using x-ray photoemission spectroscopy (model: omicron esca (electron spectroscope for chemical analysis) oxford instrument germany). in this model aluminium anode was used for samplesthat have energy 1486.7 ev. sem (model: jsm-7610f plus & make: jeol) was used to analyze the surface morphology and microstructure of deposited mgo nanostructures. the i-v characteristics for hydrogensensing were measured by using a keithley electrometer 6517a and a pressure-composition-isotherm (pci) setupat vacuum (1 *10-3 mbar) and by introducing hydrogen (at 5 bar) in the stainless-steel chamber. results and discussion following equations (i-iv) show the overall chemical reaction for the deposition of mgo nanostructure thin film using magnesium nitrate salt in aquas medium (hashaikeh and szpunar 2009). x-ray diffraction (xrd) analysis diffraction measurement was carried out with an angular scanning range of (20° – 80°) to explore the nature of the material, purity, and crystallinity of the sample. fig. 2 shows the xrd pattern of synthesized nanostructure thin films. in fig. 2, spectrum (a) shows xrd pattern of theusedito substrate, (b) shows the xrd pattern of thin film before annealing and (c) shows the xrd pattern of thin film after annealing. as discussed in equation (iii) and (iv) the xrd pattern represented by fig. 2(b) for mg(oh)2 and fig. 2(c) for mgo. the substrate peak marked by (*) is visible after post annealing at 350°c when conversion of mg(oh)2 into mgo nanostructure at ito substrate (alsultany et al. 2014). fig. 2(c) has distinctive sharp peaks correspond to (111), (200), (220) and (222) planes related to fcc structure (cvetkovic et al. 2018). the sharp peaks illustrate that the synthesized nanostructure has a good crystalline nature. the debye-scherrer equation (ashok et al. 2016) was used to compute the crystallite size d (nm). where λ, β, and 2θ were the wavelength of the incident x-ray beam (cu kα1.54 å), full width at half maximum (fwhm) in radian and bragg’s diffraction angle of the preferred orientation. the mean calculated crystalline size (d) for the deposited nanostructure was determined to be approximately 36 nm. a surface-sensitive spectroscopic method (xps) was used to determine the various elements present in a material (also known as its elemental composition), as well as their chemical state, general electronic structure, and density of their electronic states. the investigations about surface composition and chemical state of deposited mgo nanostructures using core-level light emission were reported and shown in fig. 3. it was clear from the survey scan (fig. 3a) that the deposited nanostructures were the mgo nanostructure during the synthesis process and no substantial pollutant was present in the sample. in the survey scan of the sample, the presence of carbon (c), oxygen (o), and magnesium (mg) elements and no major contaminant can be seen which validate by the elemental signals received. contamination of carbon was due to the environmental presence during the synthesis process which can be seen in fig. 3a. the mg 1s core level at 1302.8 ev is the peak with the highest intensity in the spectrum of deposited mgo nanostructure. the peak observed at 531.64 ev corresponds to o2− in the lattice of mgo. the core level spectra of mg2p were also shown in fig. 3d, where a gaussian peak of mgo at b.e. 50.91 ev was fitted using the casa xps software, and results indicate that the nanostructure of mgo was present with mg lattice, which also confirms the existence in the core level spectra of mg 1s (fig. 3b) and o 1s (fig. 3c) where mgo peak also present with lattice oxygen in the sample. the mg 2p peak analysis in fig. 3d demonstrates that mg remains in a single chemical state throughout the development process, and the characteristic b.e determines its oxidation. the binding energy of all peaks related to elemental composition with the electronic state in the survey scan from fig. 3(a) is tabulated as follows: scanning electron micrograph (sem) analysis the sem micrographs of the deposited mgo nanostructured thin films were obtained and shown in fig. 4 together with the chemical elemental mapping. the inset table provides information about the elements which were found in the deposited nanostructure. the results indicate that the mgo nanostructure was synthesized with porous surface and deposited accurately by this method. as the number of porous was more on surface of deposited film than it would be easy for detecting the gas by increasing the amount of active area that is available for gas adsorption (liu et al. 2014; liu et al. 2016; musa et al. 2021). the chemical compositions of the deposited nanostructure thin film on ito substrate are also measured by edx detector which is inbuilt into sem. it is also evident that the nanostructure was adequately present in the form, which supports the xps results. uv-visible analysis the absorption spectra of the synthesized magnesium oxide nanostructure thin films were obtained in the range of 200 and 800 nm using uv-visible spectrometer. tauc's formula in equation (vi) was used to calculate the band gap of synthesized mgo nanostructure (tauc et al. 1966) where α, h, ν, c and eg are the absorption coefficient, plank’s constant, frequency of the incident photon, a constant, and the direct transition band gap respectively. the uv-visible spectra were shown in fig. 5, in which fig. (a) indicates the absorbance spectrum (b) represents tauc’s plot to determine the optical band gap while fig. (c) denotes the derivative of absorbance versus energy for verification of band gap and (d) transmittance spectrum for the deposited mgo nanostructure. the calculated band gap with the help of the above equation and extrapolation of the curve as shown in fig. 5(b) was found about 4.16 ev, which is less than the band gap of bulk magnesium oxide (7.8 ev) as reported by many authors (bilalbegovic et al. 2004; guney et al. 2018; egwunyenga et al. 2019; baghezza, 2019). the band gap was also verified by the derivative versus energy curve which has a peak at 4.2 ev as shown in fig. 5(c). the resultant curve was linear throughout a wide range of photon energy, showing that the deposited nanostructure was a direct transition material. the band gap of metal oxide nanostructure decreases due to presence of defect states, so these defectstates are responsible for the large difference in band gap energy. both nanoparticles and nanostructures exhibit the same trend in band gap energy fluctuation however, nanostructures have a lower band gap energy than nanoparticles of the same size because of increased lattice strain and a larger surface to volume ratio (abdullah et al. 2022). guney and iskenderoglu, (2018) found that the band gap of mgo nanostructures varied with thickness from 4.31 to 4.61 ev and that the band gaps were decreased as sample thickness increased. the reduction in band gap may be related to variations in the atomic distance with the rise in film thickness. tlili et al. (2021) studied the variation of band gap from 4.01 to 4.08 ev for different molar concentrations (0.05, 0.1, 0.15, 0.2 mol·l−1) of mg2+ ions by spray pyrolys is technique and reported that, as the molar concentration of mg2+ increases, the optical band gap decreases. ftir analysis ftir spectroscopy was used to detect the existence of organic or inorganic constituents in the deposited nanostructure, which was connected to various functional groups associated with specific absorbance peaks in the spectra. the ftir spectra of deposited mgo nanostructure thin film with transmission peaks ranging from 500 to 4000 cm-1 are shown in fig. 6. the peak obtained at 545 cm-1 indicates the stretching vibration of mgo. as a result of the chemicals used during the synthesis process, the sample also contained additional functional groups at various peaks corresponding to co2, -co, c-h and -oh, etc. electrical properties the electrical properties such as current-voltage (i–v) characteristics were measuredin vacuum and with hydrogen gas by keithley electrometer 6517a in the range from -3 volt to 3 voltat room temperature. this study provides detailed information about the electronic effects in presence of hydrogen gas on deposited mgo nanostructure thin film. the curve exhibits considerable nonlinearity compared to a thin mgo tunnel barrier. it can be seen from fig. 7 that in presence of hydrogen gas, the conductivity increases in forward bias as well as in reverse bias, which can be explained as the charge shift from hydrogen to the film structure because hydrogen acts like a donor element. this property of mgo offers useful information about gas sensing applications like hydrogen gas and also can be employed as hydrogen storage materials. a similar study has been reported for mg/ti bilayer thin films (jangid et al. 2021), mg-ni thin films (jangid and jangid, 2022) and for cdte/mn bilayer thin films (nehra et al. 2009) that show the hydrogen storage properties of these bilayer thin films. a stainless-steel sealed chamber containing the synthesized sample was usedto measurecurrent-voltage characteristics while exposed to h2 gas in vacuum. the block diagram and pci/pct set up sown in fig. 8. the resistance response of synthesized mgo thin film was converted into a sensitivity value using equation (vii) (moumen et al. 2019; musa et al. 2021). where r0 stands for the film's resistance in vacuum, and rg for its resistance after being exposed to h2 gas. using equation (vii), the mgo nanostructure's sensitivity response to h2 gas was estimated to be about 31%. conclusion the mgo nanostructure thin film was synthesized on ito-coated glass substrate at room temperature by a simplified electrodeposition method using aqueous solution of magnesium nitrate and investigated by different characterization techniques. a cubic structure of mgo with a predicted crystalline size of about 36 nm was calculated by xrd investigation. the sem-edx image confirms the porous structure, adherent to the substrate and atomic % of available elements in the deposited mgo nanostructure thin films. the elemental composition and chemical states with binding energy were obtained using xps. the uv-visible analysis confirmed the optical band gap of the deposited nanostructure was ~ 4.16 ev. the i-v characteristics of deposited nanostructure suggest the partial semiconductor nature and the conductivity increases in presence of hydrogen. the sensitivity response of deposited nanostructure was approximately 31% on exposure to h2 gas. the deposited mgo nanostructures provide useful information about gas sensing applications such as hydrogen gas and also can be employed as hydrogen storage materials. the ultrafine nanostructures (such as qds etc.) provide a large and sensitive surface area for a promising solution to decrease the operating temperature for metal oxide semiconductor-based gas sensors (liu et al. 2014; liu et al. 2016). their high surface energy allows for the absorption of gas molecules even at room temperature for the sensing application. acknowledgement this research work was performed in dept. of physics, university of rajasthan, jaipur, india. the author is high thanks to the director cncer, university of rajasthan, jaipur, rajasthan india for providing characterization facilities. references abdullah bj (2022), size effect of band gap in semiconductor nanocrystals and nanostructures from density functional theory within hse06, materials science in semiconductor processing, 137: 106214. doi: 10.1016/j.mssp.2021.106214. abramishvili m, akhvlediani z, galustashvili m, dekanozishvili g, kalabegishvili t, kvatchadze v and tavkhelidze v (2011), peculiarities of radiation effects in mgo: mn2+ crystals, journalof modern physics 2: 841–844. doi:10.4236/jmp.2011.28099. alsultany fh, ahmed nm and matjafri mz (2014), effects of cw co2 laser annealing on indium tin oxide thin films characteristics, soft nanoscience letters 4(04): 83. doi: 10.4236/snl.2014.44012. ashok c, rao kv, chakra cs and rao kg (2016), mgo nanoparticles prepared by microwave-irradiation technique and its seed germination application, nano trends: a journal of nanotechnology and its application 18: 10-17. doi: 10.3390/nano11113076 baghezza mohammad (2019), optical and electrical properties of mgo thin films. khider university, m. l. b. m. m, http://a rchives. univbiskra. dz/ handle/ 123456 789/13780. bilalbegovic, g. 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hartiti b, comini e, arachchige hmm, fadili s and thevenin p (2019), preparation and characterization of nanostructured cuo thin films using spray pyrolysis technique, superlattices and microstructures 127: 2-10. doi: 10.1016/j.spmi.2018.06.061 muchuweni e, sathiaraj ts and nyakotyo h (2017), synthesis and characterization of zinc oxide thin films for optoelectronic applications, heliyon 3(4): e00285(1-18). doi: 10.1016/j.heliyon. 2017.e00285 musa amm, farhad sfu, gafur ma and jamil atmk (2021), effects of withdrawal speed on the structural, morphological, electrical, and optical properties of cuo thin films synthesized by dip-coating for co2 gas sensing, aip advances 11(11): 115004. doi: 10.1063/ 5.0060471 nehra sp, jangid mk, kumar a, singh m and vijay yk (2009), role of hydrogen in electrical and structural characteristics of bilayer cdte/mn diluted magnetic semiconductor thin films, international journal of hydrogen energy 34(17): 7306-7310. doi: 10.1016/j. ijhydene.2009.06.054 nikiforov sv, kortov vs and petrov mo (2016), luminescent and dosimetric properties of ultrafine magnesium oxide ceramics after high dose irradiation, radiationmeasurements 90: 252-256. doi: 10.1016/j.radmeas. 2015.12.018 niu f, hoerman bh and wessels bw (2000), metalorganic molecular beam epitaxy of magnesium oxide on silicon, mrs online proceedings library 619: 149-154. doi: 10.1557/proc-619-149. ravaei i, haghighat m and azami sm (2019), a dft, aim and nbo study of isoniazid drug delivery by mgo nanocage, applied surface science 469: 103-112. doi: 10.1016/j. apsusc.2018.11.005 shinji y, taro n, akio f, yoshishige s and koji a (2004), giant room-temperature magnetoresistance in single-crystal fe/mgo/fe magnetic tunnel junctions, nature materials 3: 868-871. doi:10.1038/nmat1257 skvortsova v and trinkler l (2009), luminescence of impurity and radiation defects in magnesium oxide irradiated by fast neutrons, physics procedia 2: 567-570. doi: 10.1016/j. phpro.2009.07.042 taleatu ba, omotoso e, lal c, makinde wo, ogundele kt, ajenifuja e, lasisi ar, eleruja ma and mola gt (2014), xps and some surface characterizations of electrodeposited mgo nanostructure, surfaceand interface analysis 46: 372-377. doi: 10.1002/sia.5425 tauc j, grigorovici r and vancu a (1966), optical properties and electronic structure of amorphous germanium, basic solid-state physics 15: 627-637. doi: 10.1002/pssb.19660150224. tlili m, nefzi c, alhalaili b, bouzidi c, ajilil, jebbari n and turki kamoun n (2021), synthesis and characterization of mgo thin films obtained by spray technique for optoelectronic applications, nanomaterials 11(11): 3076 (1-15). doi: 10.3390/nano11113076. wang x, feng j, bai y, zhang q and yin y (2016), synthesis, properties, and applications of hollow micro-/nanostructures, chemical reviews 116: 10983-11060. doi: 10.1021/ acs.chemrev.5b00731 wang x and xue d (2006), direct observation of the shape evolution of mgo whiskers in a solution system, materialsletters 60: 3160-3164. doi: 10.1016/j.matlet.2006.02.066 weber j, singhal r, zekri s and kumar a (2008), one-dimensional nanostructures: fabrication, characterisation and applications, international materials review 53(4): 235-255. doi: 10.1179/174328008x348183 yourdkhani a and caruntu g (2011), highly ordered transition metal ferrite nanotube arrays synthesized by template-assisted liquid phase deposition, journal of material chemistry 21: 7145-7153. doi: 10.1039/c0jm04441e zhou c, ali q, chen x, gao x, liu k and shen d (2019), ultraviolet photodetectors based on wide bandgap oxide semiconductor films, chinese physics b 28: 048503. doi: 10.1088/1674-1056/28/4/048503 zou g, chen w, liu r and xu z (2008), morphology-tunable synthesis and characterizations of mg(oh)2 films via a cathodic electrochemical process, materials chemistry and physics 107: 85-90. doi: 10.1016/j.matchemphys. 2007.06.046 zulkefle h, ismail ln, bakar ra and mahmood mr (2011), molar concentration effect on mgo thin films properties, in proceedings of the ieee symposium on industrial electronics and applications, langkawi, malaysia, pp 468-471. doi: 10.1109/isiea.2011.6108754. fig. 7. current-voltage characteristics of synthesized mgo nanostructure thin film (in vacuum and with hydrogen) fig. 8. experimental gas sensitivity measurementsetup (a) schematic block diagram (b) pct/pci setup vii synthesis of mgo nanostructure thin films via electrodeposition method126 58(2) 2023 mgo was known asa low-cost and environment-friendly material that has so many applications like bioresorbable materials that dissolve in biofluids (huang, 2018), drug delivery (ravaei et al. 2019), electrodes in pharmaceuticals and human fluids (kairya et al. 2017), resistive switching (guo et al. 2019), luminescence (nikiforov et al. 2016), photo-catalytic properties (demirci et al. 2015) and ultra-violet (uv) photodetector (zhou et al. 2019). mgo nanostructures have also been reported to exhibit thermoluminescence (abramishvili et al. 2011), radioluminescence (skvortsova and trinkler 2009), and electroluminescence (benia et al. 2007). thin metal oxide films that are electrically insulating are a crucial component of many different technologies, so magnesium oxide (mgo) has received a lot of attention for applicationssuch as spintronic devices since it has a material with a reasonably high dielectric constant. under the influence of uv light, methyl orange, and methylene blue dyes were degraded using the photocatalytic activity of mgo nanoparticles (mageshwari et al. 2013). hydrogen storage properties of mg/ti bilayer thin films were reported (jangid et al. 2021) at a different hydrogen pressure of 15 to 45 psi to realize the effect of hydrogenation. hydrogen is the lightest element in the universe, which is typical to detect and magnesium is very sensitive to hydrogen in comparison to other metals. (chawla et al. 2022). although magnesium (mg) is one of the better aspects for absorbing hydrogen, difficult to use this material for mobile applications due to its slow dynamics and need for high temperatures during dehydrogenation. due to its extremely large reversible hydrogen capacity, magnesium hydride is particularly intriguing (jangid et al. 2021). the present work reports the electrical behaviour and sensitivity of magnesium oxide (mgo) asa sensor to sense h2 gas. in a similar work dip-coated cuo thin films were used to investigate the gas-sensing response of co2 vapor in air at room temperature and reported that the physical qualities that can be altered have a lot of potential for co2 gas-sensing applications. (musa et al. 2021). for the synthesis of thin films with nanostructures, an easy, affordable, and solution-based hybrid method is electro-deposition. mgo nanostructures have been grown successfully from an aqueous solution of magnesium nitrate mg(no3)2 using the electrodeposition method (taleatu et al. 2014). the deposition procedure can be applied to a variety of conductive substrates, including polymers, semiconductors and ito-coated glass. indium tin oxide (ito) is the most widely used substrate because of its outstanding transparency to visible light and high electric conductivity (muchuweni et al. 2017). in the present work, magnesium oxide nanostructure thin film deposited by electrode position technique using magnesium nitrate solution. to synthesize mgo nanostructure, a variety of experimental procedures have been proposed, including reactive sputtering (choi and kim 2004), metal-organic molecular beam epitaxy (niu et al. 2000), chemical vapor deposition (carta et al. 2007), sol-gel (zulkefle et al. 2011), and pulsed laser deposition (kaneko et al. 2013). materials and methods a conventional homemade two-electrode electrochemical bathsetup with labelled diagram shown in fig. 1(b) was used in which graphite sheet was used as a counter electrode and ito coated glass substrate as a working electrode. both electrodes were introduced in the bath through two steel tubes. the electrolyte solution of 0.25 m concentration was prepared using magnesium nitrate mg(no3)2 salt. before the deposition process, the ito-coated glass substrate was extensively cleaned in an ultrasonic bath and rinsed with ultrapure water prior to the deposition in order to remove any surface impurities. by applying a potential difference of 2.5 v at room temperature for 30 minutes by htc power supply dc 3002, a thin layer of mgo nanostructures was deposited on ito substrate. the deposited sample was dehydrated up to 350oc at a heating rate of 10oc/min in a furnace shown in fig. 1(c) and hold for 90 minutes and thencooled at natural/normal atmosphere conditions, finally, mgo nanostructure was formed. characterization of the nanostructure shimadzu uv-2600 uv-visible spectrometer was used to analyze the optical characteristics, and fourier transform infrared spectrometer (ftir) bruker alpha was used to collect data about various functional groups present in the samplein the range 4000–500 cm-1. the structural and morphological characterization of the deposited nanostructure thin films was characterized by x-ray diffraction (xrd, model: a siemens d-5000 x-ray diffractometer) using cu-kα [1.54å] radiation. the kinetic energy distribution of photoelectrons released from the specimen material was measured using x-ray photoemission spectroscopy (model: omicron esca (electron spectroscope for chemical analysis) oxford instrument germany). in this model aluminium anode was used for samplesthat have energy 1486.7 ev. sem (model: jsm-7610f plus & make: jeol) was used to analyze the surface morphology and microstructure of deposited mgo nanostructures. the i-v characteristics for hydrogensensing were measured by using a keithley electrometer 6517a and a pressure-composition-isotherm (pci) setupat vacuum (1 *10-3 mbar) and by introducing hydrogen (at 5 bar) in the stainless-steel chamber. results and discussion following equations (i-iv) show the overall chemical reaction for the deposition of mgo nanostructure thin film using magnesium nitrate salt in aquas medium (hashaikeh and szpunar 2009). x-ray diffraction (xrd) analysis diffraction measurement was carried out with an angular scanning range of (20° – 80°) to explore the nature of the material, purity, and crystallinity of the sample. fig. 2 shows the xrd pattern of synthesized nanostructure thin films. in fig. 2, spectrum (a) shows xrd pattern of theusedito substrate, (b) shows the xrd pattern of thin film before annealing and (c) shows the xrd pattern of thin film after annealing. as discussed in equation (iii) and (iv) the xrd pattern represented by fig. 2(b) for mg(oh)2 and fig. 2(c) for mgo. the substrate peak marked by (*) is visible after post annealing at 350°c when conversion of mg(oh)2 into mgo nanostructure at ito substrate (alsultany et al. 2014). fig. 2(c) has distinctive sharp peaks correspond to (111), (200), (220) and (222) planes related to fcc structure (cvetkovic et al. 2018). the sharp peaks illustrate that the synthesized nanostructure has a good crystalline nature. the debye-scherrer equation (ashok et al. 2016) was used to compute the crystallite size d (nm). where λ, β, and 2θ were the wavelength of the incident x-ray beam (cu kα1.54 å), full width at half maximum (fwhm) in radian and bragg’s diffraction angle of the preferred orientation. the mean calculated crystalline size (d) for the deposited nanostructure was determined to be approximately 36 nm. a surface-sensitive spectroscopic method (xps) was used to determine the various elements present in a material (also known as its elemental composition), as well as their chemical state, general electronic structure, and density of their electronic states. the investigations about surface composition and chemical state of deposited mgo nanostructures using core-level light emission were reported and shown in fig. 3. it was clear from the survey scan (fig. 3a) that the deposited nanostructures were the mgo nanostructure during the synthesis process and no substantial pollutant was present in the sample. in the survey scan of the sample, the presence of carbon (c), oxygen (o), and magnesium (mg) elements and no major contaminant can be seen which validate by the elemental signals received. contamination of carbon was due to the environmental presence during the synthesis process which can be seen in fig. 3a. the mg 1s core level at 1302.8 ev is the peak with the highest intensity in the spectrum of deposited mgo nanostructure. the peak observed at 531.64 ev corresponds to o2− in the lattice of mgo. the core level spectra of mg2p were also shown in fig. 3d, where a gaussian peak of mgo at b.e. 50.91 ev was fitted using the casa xps software, and results indicate that the nanostructure of mgo was present with mg lattice, which also confirms the existence in the core level spectra of mg 1s (fig. 3b) and o 1s (fig. 3c) where mgo peak also present with lattice oxygen in the sample. the mg 2p peak analysis in fig. 3d demonstrates that mg remains in a single chemical state throughout the development process, and the characteristic b.e determines its oxidation. the binding energy of all peaks related to elemental composition with the electronic state in the survey scan from fig. 3(a) is tabulated as follows: scanning electron micrograph (sem) analysis the sem micrographs of the deposited mgo nanostructured thin films were obtained and shown in fig. 4 together with the chemical elemental mapping. the inset table provides information about the elements which were found in the deposited nanostructure. the results indicate that the mgo nanostructure was synthesized with porous surface and deposited accurately by this method. as the number of porous was more on surface of deposited film than it would be easy for detecting the gas by increasing the amount of active area that is available for gas adsorption (liu et al. 2014; liu et al. 2016; musa et al. 2021). the chemical compositions of the deposited nanostructure thin film on ito substrate are also measured by edx detector which is inbuilt into sem. it is also evident that the nanostructure was adequately present in the form, which supports the xps results. uv-visible analysis the absorption spectra of the synthesized magnesium oxide nanostructure thin films were obtained in the range of 200 and 800 nm using uv-visible spectrometer. tauc's formula in equation (vi) was used to calculate the band gap of synthesized mgo nanostructure (tauc et al. 1966) where α, h, ν, c and eg are the absorption coefficient, plank’s constant, frequency of the incident photon, a constant, and the direct transition band gap respectively. the uv-visible spectra were shown in fig. 5, in which fig. (a) indicates the absorbance spectrum (b) represents tauc’s plot to determine the optical band gap while fig. (c) denotes the derivative of absorbance versus energy for verification of band gap and (d) transmittance spectrum for the deposited mgo nanostructure. the calculated band gap with the help of the above equation and extrapolation of the curve as shown in fig. 5(b) was found about 4.16 ev, which is less than the band gap of bulk magnesium oxide (7.8 ev) as reported by many authors (bilalbegovic et al. 2004; guney et al. 2018; egwunyenga et al. 2019; baghezza, 2019). the band gap was also verified by the derivative versus energy curve which has a peak at 4.2 ev as shown in fig. 5(c). the resultant curve was linear throughout a wide range of photon energy, showing that the deposited nanostructure was a direct transition material. the band gap of metal oxide nanostructure decreases due to presence of defect states, so these defectstates are responsible for the large difference in band gap energy. both nanoparticles and nanostructures exhibit the same trend in band gap energy fluctuation however, nanostructures have a lower band gap energy than nanoparticles of the same size because of increased lattice strain and a larger surface to volume ratio (abdullah et al. 2022). guney and iskenderoglu, (2018) found that the band gap of mgo nanostructures varied with thickness from 4.31 to 4.61 ev and that the band gaps were decreased as sample thickness increased. the reduction in band gap may be related to variations in the atomic distance with the rise in film thickness. tlili et al. (2021) studied the variation of band gap from 4.01 to 4.08 ev for different molar concentrations (0.05, 0.1, 0.15, 0.2 mol·l−1) of mg2+ ions by spray pyrolys is technique and reported that, as the molar concentration of mg2+ increases, the optical band gap decreases. ftir analysis ftir spectroscopy was used to detect the existence of organic or inorganic constituents in the deposited nanostructure, which was connected to various functional groups associated with specific absorbance peaks in the spectra. the ftir spectra of deposited mgo nanostructure thin film with transmission peaks ranging from 500 to 4000 cm-1 are shown in fig. 6. the peak obtained at 545 cm-1 indicates the stretching vibration of mgo. as a result of the chemicals used during the synthesis process, the sample also contained additional functional groups at various peaks corresponding to co2, -co, c-h and -oh, etc. electrical properties the electrical properties such as current-voltage (i–v) characteristics were measuredin vacuum and with hydrogen gas by keithley electrometer 6517a in the range from -3 volt to 3 voltat room temperature. this study provides detailed information about the electronic effects in presence of hydrogen gas on deposited mgo nanostructure thin film. the curve exhibits considerable nonlinearity compared to a thin mgo tunnel barrier. it can be seen from fig. 7 that in presence of hydrogen gas, the conductivity increases in forward bias as well as in reverse bias, which can be explained as the charge shift from hydrogen to the film structure because hydrogen acts like a donor element. this property of mgo offers useful information about gas sensing applications like hydrogen gas and also can be employed as hydrogen storage materials. a similar study has been reported for mg/ti bilayer thin films (jangid et al. 2021), mg-ni thin films (jangid and jangid, 2022) and for cdte/mn bilayer thin films (nehra et al. 2009) that show the hydrogen storage properties of these bilayer thin films. a stainless-steel sealed chamber containing the synthesized sample was usedto measurecurrent-voltage characteristics while exposed to h2 gas in vacuum. the block diagram and pci/pct set up sown in fig. 8. the resistance response of synthesized mgo thin film was converted into a sensitivity value using equation (vii) (moumen et al. 2019; musa et al. 2021). where r0 stands for the film's resistance in vacuum, and rg for its resistance after being exposed to h2 gas. using equation (vii), the mgo nanostructure's sensitivity response to h2 gas was estimated to be about 31%. conclusion the mgo nanostructure thin film was synthesized on ito-coated glass substrate at room temperature by a simplified electrodeposition method using aqueous solution of magnesium nitrate and investigated by different characterization techniques. a cubic structure of mgo with a predicted crystalline size of about 36 nm was calculated by xrd investigation. the sem-edx image confirms the porous structure, adherent to the substrate and atomic % of available elements in the deposited mgo nanostructure thin films. the elemental composition and chemical states with binding energy were obtained using xps. the uv-visible analysis confirmed the optical band gap of the deposited nanostructure was ~ 4.16 ev. the i-v characteristics of deposited nanostructure suggest the partial semiconductor nature and the conductivity increases in presence of hydrogen. the sensitivity response of deposited nanostructure was approximately 31% on exposure to h2 gas. the deposited mgo nanostructures provide useful information about gas sensing applications such as hydrogen gas and also can be employed as hydrogen storage materials. the ultrafine nanostructures (such as qds etc.) provide a large and sensitive surface area for a promising solution to decrease the operating temperature for metal oxide semiconductor-based gas sensors (liu et al. 2014; liu et al. 2016). their high surface energy allows for the absorption of gas molecules even at room temperature for the sensing application. acknowledgement this research work was performed in dept. of physics, university of rajasthan, jaipur, india. the author is high thanks to the director cncer, university of rajasthan, jaipur, rajasthan india for providing characterization facilities. references abdullah bj (2022), size effect of band gap in semiconductor nanocrystals and nanostructures from density functional theory within hse06, materials science in semiconductor processing, 137: 106214. doi: 10.1016/j.mssp.2021.106214. abramishvili m, akhvlediani z, galustashvili m, dekanozishvili g, kalabegishvili t, kvatchadze v and tavkhelidze v (2011), peculiarities of radiation effects in mgo: mn2+ crystals, journalof modern physics 2: 841–844. doi:10.4236/jmp.2011.28099. alsultany fh, ahmed nm and matjafri mz (2014), effects of cw co2 laser annealing on indium tin oxide thin films characteristics, soft nanoscience letters 4(04): 83. doi: 10.4236/snl.2014.44012. ashok c, rao kv, chakra cs and rao kg (2016), mgo nanoparticles prepared by microwave-irradiation technique and its seed germination application, nano trends: a journal of nanotechnology and its application 18: 10-17. doi: 10.3390/nano11113076 baghezza mohammad (2019), optical and electrical properties of mgo thin films. khider university, m. l. b. m. m, http://a rchives. univbiskra. dz/ handle/ 123456 789/13780. bilalbegovic, g. (2004), structural and electronic properties of mgo nanotube clusters, physical review b 70(4): 045407. doi: 10.1103/physrevb.70.045407. benia hm, lin x, gao hj, nilius l and freund hj (2007), nucleation and growth of gold on mgo thin films: a combined stm and luminescence study, journal of physical chemistry c111: 10528-10533. doi:10. 1021/jp0726891 bhatte kd, sawant dn, deshmukh km, bhanage bm, rusdi r, kamarudin n, llanos m and lopez-salinas (2012), additive free microwave assisted synthesis of nanocrystalline mg(oh)2 and mgo, the lancet 10: 384-387. doi: 10.1016/j.partic.2011.05.004 carta g, habra n el, crociani l, rossetto g, zanella p, paolucci g, barreca d and tondello e (2007), cvd of mgo thin films from bis(methylcyclopentadienyl) magnesium, chemical vapor deposition 13(4): 185-189. doi:10.1002/cvde.200606574 chatterjee s, gohil s, chalke band ayyub p (2009), optimization of the morphology of zno nanorods grown by an electrochemical process, journalof nanoscience and nanotechnology 9(8): 47924796. doi: 10. 1166/jnn.2009.1094 chawla k, yadav dk, bajpai a, kumar s, jain ip and lal c (2022), effect of pdcl2 catalyst on the hydrogenation properties and sorption kinetics of mg, international journal of hydrogen energy 51: 101981. doi: 10.1016/ j.seta.2022.101981 choi yw and kim j (2004), reactive sputtering of magnesium oxide thin film for plasma display panel applications, thin solid films 460: 295-299. doi: 10.5370/jeet.2006.1.1.110 cvetkovic vs, vukicevic nm, nikolic nd, brankovic g, barudzija ts and jovicevic jn (2018), formation of needle-like and honeycomb-like magnesium oxide/hydroxide structures by electrodeposition from magnesium nitrate melts. electrochimica acta 268: 494-502. doi: 10.1016/j.electacta.2018.02.121. demirci so, zturk b, yildirim s, bakal f, erol m, sancakoglu o, yigit r, celik re and batar t (2015), synthesis and comparison of the photocatalytic activities of flame spray pyrolysis and sol-gel derived magnesium oxide nano-scale 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10.1039/c3ra23340e. kaneko s, ito t, soga m, motoizumi y, yasui m, hirabayashi y, ozawa t and yoshimoto m (2013), growth of nanocubic mgo on silicon substrate by pulsed laser deposition, japanese journal of applied physics 52(15): 01an02(1-3). doi: 10.7567/jjap.52.01an02 khairya m, khorshed aa, rashwan fa, salah ga, abdel-wadood hm and banksd ce (2017), simultaneous voltametric determination of antihypertensive drugs nifedipine and atenolol utilizing mgo nanoplatelet modified screen-printed electrodes in pharmaceuticals and human fluids, sensorand actuators b: chemical 252: 1045-1054. doi: 10.1016/ j.snb.2017.06.105 lan x, zhang jy, gao h and wang tm (2011), morphology-controlled hydrothermal synthesis and growth mechanism of microcrystal cu2o, crystal engineering communication (royal society of chemistry) 13: 630-636. doi: 10.1039/c0ce00232a. li cf, ho wh and yen sk (2009), effects of applied voltage on morphology and crystal orientation of mg(oh)2 coating on pt by electrochemical synthesis, journal of electrochemistry society 156: e29-e34. doi: 10.1149/1.3032174. liu h, li m, voznyy o, hu l, fu q, zhou d, sargent eh, tang j and xia z (2014), physically flexible, rapid-response gas sensor based on colloidal quantum dot solids, advanced materials 26: 2718-2724. doi: 10.1002/adma.201304366 liu h, zhang w, yu h, gao l, song z, xu s, li m, wang y, song h and tang j (2016), solution-processed gas sensors employing sno2 quantum dot/mwcnt nanocomposites, acs applied materials & interfaces 8: 840-846. doi: 10.1021/acsami.5b10188 ma j, chen cz, wang dg and hu jh (2011), synthesis characterization and in vitro bioactivity of magnesium-doped sol-gel glass and glass-ceramics, ceramic international 37: 1637-1644. doi: 10.1016/j.ceramint.2011.01.043 mageshwari k, mali ss, sathyamoorthy r and patil ps (2013), template-free synthesis of mgo nanoparticles for effective photocatalytic applications, powder technology 249: 456-462. doi: 10.1016/j.powtec.2013.09.016. moumen a, hartiti b, comini e, arachchige hmm, fadili s and thevenin p (2019), preparation and characterization of nanostructured cuo thin films using spray pyrolysis technique, superlattices and microstructures 127: 2-10. doi: 10.1016/j.spmi.2018.06.061 muchuweni e, sathiaraj ts and nyakotyo h (2017), synthesis and characterization of zinc oxide thin films for optoelectronic applications, heliyon 3(4): e00285(1-18). doi: 10.1016/j.heliyon. 2017.e00285 musa amm, farhad sfu, gafur ma and jamil atmk (2021), effects of withdrawal speed on the structural, morphological, electrical, and optical properties of cuo thin films synthesized by dip-coating for co2 gas sensing, aip advances 11(11): 115004. doi: 10.1063/ 5.0060471 nehra sp, jangid mk, kumar a, singh m and vijay yk (2009), role of hydrogen in electrical and structural characteristics of bilayer cdte/mn diluted magnetic semiconductor thin films, international journal of hydrogen energy 34(17): 7306-7310. doi: 10.1016/j. ijhydene.2009.06.054 nikiforov sv, kortov vs and petrov mo (2016), luminescent and dosimetric properties of ultrafine magnesium oxide ceramics after high dose irradiation, radiationmeasurements 90: 252-256. doi: 10.1016/j.radmeas. 2015.12.018 niu f, hoerman bh and wessels bw (2000), metalorganic molecular beam epitaxy of magnesium oxide on silicon, mrs online proceedings library 619: 149-154. doi: 10.1557/proc-619-149. ravaei i, haghighat m and azami sm (2019), a dft, aim and nbo study of isoniazid drug delivery by mgo nanocage, applied surface science 469: 103-112. doi: 10.1016/j. apsusc.2018.11.005 shinji y, taro n, akio f, yoshishige s and koji a (2004), giant room-temperature magnetoresistance in single-crystal fe/mgo/fe magnetic tunnel junctions, nature materials 3: 868-871. doi:10.1038/nmat1257 skvortsova v and trinkler l (2009), luminescence of impurity and radiation defects in magnesium oxide irradiated by fast neutrons, physics procedia 2: 567-570. doi: 10.1016/j. phpro.2009.07.042 taleatu ba, omotoso e, lal c, makinde wo, ogundele kt, ajenifuja e, lasisi ar, eleruja ma and mola gt (2014), xps and some surface characterizations of electrodeposited mgo nanostructure, surfaceand interface analysis 46: 372-377. doi: 10.1002/sia.5425 tauc j, grigorovici r and vancu a (1966), optical properties and electronic structure of amorphous germanium, basic solid-state physics 15: 627-637. doi: 10.1002/pssb.19660150224. tlili m, nefzi c, alhalaili b, bouzidi c, ajilil, jebbari n and turki kamoun n (2021), synthesis and characterization of mgo thin films obtained by spray technique for optoelectronic applications, nanomaterials 11(11): 3076 (1-15). doi: 10.3390/nano11113076. wang x, feng j, bai y, zhang q and yin y (2016), synthesis, properties, and applications of hollow micro-/nanostructures, chemical reviews 116: 10983-11060. doi: 10.1021/ acs.chemrev.5b00731 wang x and xue d (2006), direct observation of the shape evolution of mgo whiskers in a solution system, materialsletters 60: 3160-3164. doi: 10.1016/j.matlet.2006.02.066 weber j, singhal r, zekri s and kumar a (2008), one-dimensional nanostructures: fabrication, characterisation and applications, international materials review 53(4): 235-255. doi: 10.1179/174328008x348183 yourdkhani a and caruntu g (2011), highly ordered transition metal ferrite nanotube arrays synthesized by template-assisted liquid phase deposition, journal of material chemistry 21: 7145-7153. doi: 10.1039/c0jm04441e zhou c, ali q, chen x, gao x, liu k and shen d (2019), ultraviolet photodetectors based on wide bandgap oxide semiconductor films, chinese physics b 28: 048503. doi: 10.1088/1674-1056/28/4/048503 zou g, chen w, liu r and xu z (2008), morphology-tunable synthesis and characterizations of mg(oh)2 films via a cathodic electrochemical process, materials chemistry and physics 107: 85-90. doi: 10.1016/j.matchemphys. 2007.06.046 zulkefle h, ismail ln, bakar ra and mahmood mr (2011), molar concentration effect on mgo thin films properties, in proceedings of the ieee symposium on industrial electronics and applications, langkawi, malaysia, pp 468-471. doi: 10.1109/isiea.2011.6108754. mgo was known asa low-cost and environment-friendly material that has so many applications like bioresorbable materials that dissolve in biofluids (huang, 2018), drug delivery (ravaei et al. 2019), electrodes in pharmaceuticals and human fluids (kairya et al. 2017), resistive switching (guo et al. 2019), luminescence (nikiforov et al. 2016), photo-catalytic properties (demirci et al. 2015) and ultra-violet (uv) photodetector (zhou et al. 2019). mgo nanostructures have also been reported to exhibit thermoluminescence (abramishvili et al. 2011), radioluminescence (skvortsova and trinkler 2009), and electroluminescence (benia et al. 2007). thin metal oxide films that are electrically insulating are a crucial component of many different technologies, so magnesium oxide (mgo) has received a lot of attention for applicationssuch as spintronic devices since it has a material with a reasonably high dielectric constant. under the influence of uv light, methyl orange, and methylene blue dyes were degraded using the photocatalytic activity of mgo nanoparticles (mageshwari et al. 2013). hydrogen storage properties of mg/ti bilayer thin films were reported (jangid et al. 2021) at a different hydrogen pressure of 15 to 45 psi to realize the effect of hydrogenation. hydrogen is the lightest element in the universe, which is typical to detect and magnesium is very sensitive to hydrogen in comparison to other metals. (chawla et al. 2022). although magnesium (mg) is one of the better aspects for absorbing hydrogen, difficult to use this material for mobile applications due to its slow dynamics and need for high temperatures during dehydrogenation. due to its extremely large reversible hydrogen capacity, magnesium hydride is particularly intriguing (jangid et al. 2021). the present work reports the electrical behaviour and sensitivity of magnesium oxide (mgo) asa sensor to sense h2 gas. in a similar work dip-coated cuo thin films were used to investigate the gas-sensing response of co2 vapor in air at room temperature and reported that the physical qualities that can be altered have a lot of potential for co2 gas-sensing applications. (musa et al. 2021). for the synthesis of thin films with nanostructures, an easy, affordable, and solution-based hybrid method is electro-deposition. mgo nanostructures have been grown successfully from an aqueous solution of magnesium nitrate mg(no3)2 using the electrodeposition method (taleatu et al. 2014). the deposition procedure can be applied to a variety of conductive substrates, including polymers, semiconductors and ito-coated glass. indium tin oxide (ito) is the most widely used substrate because of its outstanding transparency to visible light and high electric conductivity (muchuweni et al. 2017). in the present work, magnesium oxide nanostructure thin film deposited by electrode position technique using magnesium nitrate solution. to synthesize mgo nanostructure, a variety of experimental procedures have been proposed, including reactive sputtering (choi and kim 2004), metal-organic molecular beam epitaxy (niu et al. 2000), chemical vapor deposition (carta et al. 2007), sol-gel (zulkefle et al. 2011), and pulsed laser deposition (kaneko et al. 2013). materials and methods a conventional homemade two-electrode electrochemical bathsetup with labelled diagram shown in fig. 1(b) was used in which graphite sheet was used as a counter electrode and ito coated glass substrate as a working electrode. both electrodes were introduced in the bath through two steel tubes. the electrolyte solution of 0.25 m concentration was prepared using magnesium nitrate mg(no3)2 salt. before the deposition process, the ito-coated glass substrate was extensively cleaned in an ultrasonic bath and rinsed with ultrapure water prior to the deposition in order to remove any surface impurities. by applying a potential difference of 2.5 v at room temperature for 30 minutes by htc power supply dc 3002, a thin layer of mgo nanostructures was deposited on ito substrate. the deposited sample was dehydrated up to 350oc at a heating rate of 10oc/min in a furnace shown in fig. 1(c) and hold for 90 minutes and thencooled at natural/normal atmosphere conditions, finally, mgo nanostructure was formed. characterization of the nanostructure shimadzu uv-2600 uv-visible spectrometer was used to analyze the optical characteristics, and fourier transform infrared spectrometer (ftir) bruker alpha was used to collect data about various functional groups present in the samplein the range 4000–500 cm-1. the structural and morphological characterization of the deposited nanostructure thin films was characterized by x-ray diffraction (xrd, model: a siemens d-5000 x-ray diffractometer) using cu-kα [1.54å] radiation. the kinetic energy distribution of photoelectrons released from the specimen material was measured using x-ray photoemission spectroscopy (model: omicron esca (electron spectroscope for chemical analysis) oxford instrument germany). in this model aluminium anode was used for samplesthat have energy 1486.7 ev. sem (model: jsm-7610f plus & make: jeol) was used to analyze the surface morphology and microstructure of deposited mgo nanostructures. the i-v characteristics for hydrogensensing were measured by using a keithley electrometer 6517a and a pressure-composition-isotherm (pci) setupat vacuum (1 *10-3 mbar) and by introducing hydrogen (at 5 bar) in the stainless-steel chamber. results and discussion following equations (i-iv) show the overall chemical reaction for the deposition of mgo nanostructure thin film using magnesium nitrate salt in aquas medium (hashaikeh and szpunar 2009). x-ray diffraction (xrd) analysis diffraction measurement was carried out with an angular scanning range of (20° – 80°) to explore the nature of the material, purity, and crystallinity of the sample. fig. 2 shows the xrd pattern of synthesized nanostructure thin films. in fig. 2, spectrum (a) shows xrd pattern of theusedito substrate, (b) shows the xrd pattern of thin film before annealing and (c) shows the xrd pattern of thin film after annealing. as discussed in equation (iii) and (iv) the xrd pattern represented by fig. 2(b) for mg(oh)2 and fig. 2(c) for mgo. the substrate peak marked by (*) is visible after post annealing at 350°c when conversion of mg(oh)2 into mgo nanostructure at ito substrate (alsultany et al. 2014). fig. 2(c) has distinctive sharp peaks correspond to (111), (200), (220) and (222) planes related to fcc structure (cvetkovic et al. 2018). the sharp peaks illustrate that the synthesized nanostructure has a good crystalline nature. the debye-scherrer equation (ashok et al. 2016) was used to compute the crystallite size d (nm). where λ, β, and 2θ were the wavelength of the incident x-ray beam (cu kα1.54 å), full width at half maximum (fwhm) in radian and bragg’s diffraction angle of the preferred orientation. the mean calculated crystalline size (d) for the deposited nanostructure was determined to be approximately 36 nm. a surface-sensitive spectroscopic method (xps) was used to determine the various elements present in a material (also known as its elemental composition), as well as their chemical state, general electronic structure, and density of their electronic states. the investigations about surface composition and chemical state of deposited mgo nanostructures using core-level light emission were reported and shown in fig. 3. it was clear from the survey scan (fig. 3a) that the deposited nanostructures were the mgo nanostructure during the synthesis process and no substantial pollutant was present in the sample. in the survey scan of the sample, the presence of carbon (c), oxygen (o), and magnesium (mg) elements and no major contaminant can be seen which validate by the elemental signals received. contamination of carbon was due to the environmental presence during the synthesis process which can be seen in fig. 3a. the mg 1s core level at 1302.8 ev is the peak with the highest intensity in the spectrum of deposited mgo nanostructure. the peak observed at 531.64 ev corresponds to o2− in the lattice of mgo. the core level spectra of mg2p were also shown in fig. 3d, where a gaussian peak of mgo at b.e. 50.91 ev was fitted using the casa xps software, and results indicate that the nanostructure of mgo was present with mg lattice, which also confirms the existence in the core level spectra of mg 1s (fig. 3b) and o 1s (fig. 3c) where mgo peak also present with lattice oxygen in the sample. the mg 2p peak analysis in fig. 3d demonstrates that mg remains in a single chemical state throughout the development process, and the characteristic b.e determines its oxidation. the binding energy of all peaks related to elemental composition with the electronic state in the survey scan from fig. 3(a) is tabulated as follows: scanning electron micrograph (sem) analysis the sem micrographs of the deposited mgo nanostructured thin films were obtained and shown in fig. 4 together with the chemical elemental mapping. the inset table provides information about the elements which were found in the deposited nanostructure. the results indicate that the mgo nanostructure was synthesized with porous surface and deposited accurately by this method. as the number of porous was more on surface of deposited film than it would be easy for detecting the gas by increasing the amount of active area that is available for gas adsorption (liu et al. 2014; liu et al. 2016; musa et al. 2021). the chemical compositions of the deposited nanostructure thin film on ito substrate are also measured by edx detector which is inbuilt into sem. it is also evident that the nanostructure was adequately present in the form, which supports the xps results. uv-visible analysis the absorption spectra of the synthesized magnesium oxide nanostructure thin films were obtained in the range of 200 and 800 nm using uv-visible spectrometer. tauc's formula in equation (vi) was used to calculate the band gap of synthesized mgo nanostructure (tauc et al. 1966) where α, h, ν, c and eg are the absorption coefficient, plank’s constant, frequency of the incident photon, a constant, and the direct transition band gap respectively. the uv-visible spectra were shown in fig. 5, in which fig. (a) indicates the absorbance spectrum (b) represents tauc’s plot to determine the optical band gap while fig. (c) denotes the derivative of absorbance versus energy for verification of band gap and (d) transmittance spectrum for the deposited mgo nanostructure. the calculated band gap with the help of the above equation and extrapolation of the curve as shown in fig. 5(b) was found about 4.16 ev, which is less than the band gap of bulk magnesium oxide (7.8 ev) as reported by many authors (bilalbegovic et al. 2004; guney et al. 2018; egwunyenga et al. 2019; baghezza, 2019). the band gap was also verified by the derivative versus energy curve which has a peak at 4.2 ev as shown in fig. 5(c). the resultant curve was linear throughout a wide range of photon energy, showing that the deposited nanostructure was a direct transition material. the band gap of metal oxide nanostructure decreases due to presence of defect states, so these defectstates are responsible for the large difference in band gap energy. both nanoparticles and nanostructures exhibit the same trend in band gap energy fluctuation however, nanostructures have a lower band gap energy than nanoparticles of the same size because of increased lattice strain and a larger surface to volume ratio (abdullah et al. 2022). guney and iskenderoglu, (2018) found that the band gap of mgo nanostructures varied with thickness from 4.31 to 4.61 ev and that the band gaps were decreased as sample thickness increased. the reduction in band gap may be related to variations in the atomic distance with the rise in film thickness. tlili et al. (2021) studied the variation of band gap from 4.01 to 4.08 ev for different molar concentrations (0.05, 0.1, 0.15, 0.2 mol·l−1) of mg2+ ions by spray pyrolys is technique and reported that, as the molar concentration of mg2+ increases, the optical band gap decreases. ftir analysis ftir spectroscopy was used to detect the existence of organic or inorganic constituents in the deposited nanostructure, which was connected to various functional groups associated with specific absorbance peaks in the spectra. the ftir spectra of deposited mgo nanostructure thin film with transmission peaks ranging from 500 to 4000 cm-1 are shown in fig. 6. the peak obtained at 545 cm-1 indicates the stretching vibration of mgo. as a result of the chemicals used during the synthesis process, the sample also contained additional functional groups at various peaks corresponding to co2, -co, c-h and -oh, etc. electrical properties the electrical properties such as current-voltage (i–v) characteristics were measuredin vacuum and with hydrogen gas by keithley electrometer 6517a in the range from -3 volt to 3 voltat room temperature. this study provides detailed information about the electronic effects in presence of hydrogen gas on deposited mgo nanostructure thin film. the curve exhibits considerable nonlinearity compared to a thin mgo tunnel barrier. it can be seen from fig. 7 that in presence of hydrogen gas, the conductivity increases in forward bias as well as in reverse bias, which can be explained as the charge shift from hydrogen to the film structure because hydrogen acts like a donor element. this property of mgo offers useful information about gas sensing applications like hydrogen gas and also can be employed as hydrogen storage materials. a similar study has been reported for mg/ti bilayer thin films (jangid et al. 2021), mg-ni thin films (jangid and jangid, 2022) and for cdte/mn bilayer thin films (nehra et al. 2009) that show the hydrogen storage properties of these bilayer thin films. a stainless-steel sealed chamber containing the synthesized sample was usedto measurecurrent-voltage characteristics while exposed to h2 gas in vacuum. the block diagram and pci/pct set up sown in fig. 8. the resistance response of synthesized mgo thin film was converted into a sensitivity value using equation (vii) (moumen et al. 2019; musa et al. 2021). where r0 stands for the film's resistance in vacuum, and rg for its resistance after being exposed to h2 gas. using equation (vii), the mgo nanostructure's sensitivity response to h2 gas was estimated to be about 31%. conclusion the mgo nanostructure thin film was synthesized on ito-coated glass substrate at room temperature by a simplified electrodeposition method using aqueous solution of magnesium nitrate and investigated by different characterization techniques. a cubic structure of mgo with a predicted crystalline size of about 36 nm was calculated by xrd investigation. the sem-edx image confirms the porous structure, adherent to the substrate and atomic % of available elements in the deposited mgo nanostructure thin films. the elemental composition and chemical states with binding energy were obtained using xps. the uv-visible analysis confirmed the optical band gap of the deposited nanostructure was ~ 4.16 ev. the i-v characteristics of deposited nanostructure suggest the partial semiconductor nature and the conductivity increases in presence of hydrogen. the sensitivity response of deposited nanostructure was approximately 31% on exposure to h2 gas. the deposited mgo nanostructures provide useful information about gas sensing applications such as hydrogen gas and also can be employed as hydrogen storage materials. the ultrafine nanostructures (such as qds etc.) provide a large and sensitive surface area for a promising solution to decrease the operating temperature for metal oxide semiconductor-based gas sensors (liu et al. 2014; liu et al. 2016). their high surface energy allows for the absorption of gas molecules even at room temperature for the sensing application. acknowledgement this research work was performed in dept. of physics, university of rajasthan, jaipur, india. the author is high thanks to the director cncer, university of rajasthan, jaipur, rajasthan india for providing characterization facilities. references abdullah bj (2022), size effect of band gap in semiconductor nanocrystals and nanostructures from density functional theory within hse06, materials science in semiconductor processing, 137: 106214. doi: 10.1016/j.mssp.2021.106214. abramishvili m, akhvlediani z, galustashvili m, dekanozishvili g, kalabegishvili t, kvatchadze v and tavkhelidze v (2011), peculiarities of radiation effects in mgo: mn2+ crystals, journalof modern physics 2: 841–844. doi:10.4236/jmp.2011.28099. alsultany fh, ahmed nm and matjafri mz (2014), effects of cw co2 laser annealing on indium tin oxide thin films characteristics, soft nanoscience letters 4(04): 83. doi: 10.4236/snl.2014.44012. ashok c, rao kv, chakra cs and rao kg (2016), mgo nanoparticles prepared by microwave-irradiation technique and its seed germination application, nano trends: a journal of nanotechnology and its application 18: 10-17. doi: 10.3390/nano11113076 baghezza mohammad (2019), optical and electrical properties of mgo thin films. khider university, m. l. b. m. m, http://a rchives. univbiskra. dz/ handle/ 123456 789/13780. bilalbegovic, g. (2004), structural and electronic properties of mgo nanotube clusters, physical review b 70(4): 045407. doi: 10.1103/physrevb.70.045407. benia hm, lin x, gao hj, nilius l and freund hj (2007), nucleation and growth of gold on mgo thin films: a combined stm and luminescence study, journal of physical chemistry c111: 10528-10533. doi:10. 1021/jp0726891 bhatte kd, sawant dn, deshmukh km, bhanage bm, rusdi r, kamarudin n, llanos m and lopez-salinas (2012), additive free microwave assisted synthesis of nanocrystalline mg(oh)2 and mgo, the lancet 10: 384-387. doi: 10.1016/j.partic.2011.05.004 carta g, habra n el, crociani l, rossetto g, zanella p, paolucci g, barreca d and tondello e (2007), cvd of mgo thin films from bis(methylcyclopentadienyl) magnesium, chemical vapor deposition 13(4): 185-189. doi:10.1002/cvde.200606574 chatterjee s, gohil s, chalke band ayyub p (2009), optimization of the morphology of zno nanorods grown by an electrochemical process, journalof nanoscience and nanotechnology 9(8): 47924796. doi: 10. 1166/jnn.2009.1094 chawla k, yadav dk, bajpai a, kumar s, jain ip and lal c (2022), effect of pdcl2 catalyst on the hydrogenation properties and sorption kinetics of mg, international journal of hydrogen energy 51: 101981. doi: 10.1016/ j.seta.2022.101981 choi yw and kim j (2004), reactive sputtering of magnesium oxide thin film for plasma display panel applications, thin solid films 460: 295-299. doi: 10.5370/jeet.2006.1.1.110 cvetkovic vs, vukicevic nm, nikolic nd, brankovic g, barudzija ts and jovicevic jn (2018), formation of needle-like and honeycomb-like magnesium oxide/hydroxide structures by electrodeposition from magnesium nitrate melts. electrochimica acta 268: 494-502. doi: 10.1016/j.electacta.2018.02.121. demirci so, zturk b, yildirim s, bakal f, erol m, sancakoglu o, yigit r, celik re and batar t (2015), synthesis and comparison of the photocatalytic activities of flame spray pyrolysis and sol-gel derived magnesium oxide nano-scale particles, materials science in semiconductor processing 34: 154-161. doi: 10.1016/j.mssp. 2015.02.029 egwunyenga nj, ezenwa ia and ezenwaka ln (2019), optical properties of electrodeposited magnesium oxide thin films, coou journal of physical sciences 1(2): 11-18.https:// coou.edu.ng/ journals/ cjops/cjps1219002.pdf. guo y, song q and yan h (2019), the influence of interaction between oxygen vacancies on set process in resistive switching: a case of mgo,aip advances 9: 055230(1-7). doi:10.1063/1.5092690. guney h and iskenderoglu d (2018), synthesis of mgo thin films grown by silar technique, ceramics international 44(7): 7788-7793. doi: 10.1016/j.ceramint. 2018.01.210 hashaikeh r and szpunar ja (2009), electrolytic processing of mgo coatings, conference series, international conference on advanced structural and functional materials design, journal of physics 165: 012008:1-4. doi:10.1088/1742-6596/165/1/012008 huang x (2018), materials and applications of bioresorbable electronics, 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10.1039/c3ra23340e. kaneko s, ito t, soga m, motoizumi y, yasui m, hirabayashi y, ozawa t and yoshimoto m (2013), growth of nanocubic mgo on silicon substrate by pulsed laser deposition, japanese journal of applied physics 52(15): 01an02(1-3). doi: 10.7567/jjap.52.01an02 khairya m, khorshed aa, rashwan fa, salah ga, abdel-wadood hm and banksd ce (2017), simultaneous voltametric determination of antihypertensive drugs nifedipine and atenolol utilizing mgo nanoplatelet modified screen-printed electrodes in pharmaceuticals and human fluids, sensorand actuators b: chemical 252: 1045-1054. doi: 10.1016/ j.snb.2017.06.105 lan x, zhang jy, gao h and wang tm (2011), morphology-controlled hydrothermal synthesis and growth mechanism of microcrystal cu2o, crystal engineering communication (royal society of chemistry) 13: 630-636. doi: 10.1039/c0ce00232a. li cf, ho wh and yen sk (2009), effects of applied voltage on morphology and crystal orientation of mg(oh)2 coating on pt by electrochemical synthesis, journal of electrochemistry society 156: e29-e34. doi: 10.1149/1.3032174. liu h, li m, voznyy o, hu l, fu q, zhou d, sargent eh, tang j and xia z (2014), physically flexible, rapid-response gas sensor based on colloidal quantum dot solids, advanced materials 26: 2718-2724. doi: 10.1002/adma.201304366 liu h, zhang w, yu h, gao l, song z, xu s, li m, wang y, song h and tang j (2016), solution-processed gas sensors employing sno2 quantum dot/mwcnt nanocomposites, acs applied materials & interfaces 8: 840-846. doi: 10.1021/acsami.5b10188 ma j, chen cz, wang dg and hu jh (2011), synthesis characterization and in vitro bioactivity of magnesium-doped sol-gel glass and glass-ceramics, ceramic international 37: 1637-1644. doi: 10.1016/j.ceramint.2011.01.043 mageshwari k, mali ss, sathyamoorthy r and patil ps (2013), template-free synthesis of mgo nanoparticles for effective photocatalytic applications, powder technology 249: 456-462. doi: 10.1016/j.powtec.2013.09.016. moumen a, hartiti b, comini e, arachchige hmm, fadili s and thevenin p (2019), preparation and characterization of nanostructured cuo thin films using spray pyrolysis technique, superlattices and microstructures 127: 2-10. doi: 10.1016/j.spmi.2018.06.061 muchuweni e, sathiaraj ts and nyakotyo h (2017), synthesis and characterization of zinc oxide thin films for optoelectronic applications, heliyon 3(4): e00285(1-18). doi: 10.1016/j.heliyon. 2017.e00285 musa amm, farhad sfu, gafur ma and jamil atmk (2021), effects of withdrawal speed on the structural, morphological, electrical, and optical properties of cuo thin films synthesized by dip-coating for co2 gas sensing, aip advances 11(11): 115004. doi: 10.1063/ 5.0060471 nehra sp, jangid mk, kumar a, singh m and vijay yk (2009), role of hydrogen in electrical and structural characteristics of bilayer cdte/mn diluted magnetic semiconductor thin films, international journal of hydrogen energy 34(17): 7306-7310. doi: 10.1016/j. ijhydene.2009.06.054 nikiforov sv, kortov vs and petrov mo (2016), luminescent and dosimetric properties of ultrafine magnesium oxide ceramics after high dose irradiation, radiationmeasurements 90: 252-256. doi: 10.1016/j.radmeas. 2015.12.018 niu f, hoerman bh and wessels bw (2000), metalorganic molecular beam epitaxy of magnesium oxide on silicon, mrs online proceedings library 619: 149-154. doi: 10.1557/proc-619-149. ravaei i, haghighat m and azami sm (2019), a dft, aim and nbo study of isoniazid drug delivery by mgo nanocage, applied surface science 469: 103-112. doi: 10.1016/j. apsusc.2018.11.005 shinji y, taro n, akio f, yoshishige s and koji a (2004), giant room-temperature magnetoresistance in single-crystal fe/mgo/fe magnetic tunnel junctions, nature materials 3: 868-871. doi:10.1038/nmat1257 skvortsova v and trinkler l (2009), luminescence of impurity and radiation defects in magnesium oxide irradiated by fast neutrons, physics procedia 2: 567-570. doi: 10.1016/j. phpro.2009.07.042 taleatu ba, omotoso e, lal c, makinde wo, ogundele kt, ajenifuja e, lasisi ar, eleruja ma and mola gt (2014), xps and some surface characterizations of electrodeposited mgo nanostructure, surfaceand interface analysis 46: 372-377. doi: 10.1002/sia.5425 tauc j, grigorovici r and vancu a (1966), optical properties and electronic structure of amorphous germanium, basic solid-state physics 15: 627-637. doi: 10.1002/pssb.19660150224. tlili m, nefzi c, alhalaili b, bouzidi c, ajilil, jebbari n and turki kamoun n (2021), synthesis and characterization of mgo thin films obtained by spray technique for optoelectronic applications, nanomaterials 11(11): 3076 (1-15). doi: 10.3390/nano11113076. wang x, feng j, bai y, zhang q and yin y (2016), synthesis, properties, and applications of hollow micro-/nanostructures, chemical reviews 116: 10983-11060. doi: 10.1021/ acs.chemrev.5b00731 wang x and xue d (2006), direct observation of the shape evolution of mgo whiskers in a solution system, materialsletters 60: 3160-3164. doi: 10.1016/j.matlet.2006.02.066 weber j, singhal r, zekri s and kumar a (2008), one-dimensional nanostructures: fabrication, characterisation and applications, international materials review 53(4): 235-255. doi: 10.1179/174328008x348183 yourdkhani a and caruntu g (2011), highly ordered transition metal ferrite nanotube arrays synthesized by template-assisted liquid phase deposition, journal of material chemistry 21: 7145-7153. doi: 10.1039/c0jm04441e zhou c, ali q, chen x, gao x, liu k and shen d (2019), ultraviolet photodetectors based on wide bandgap oxide semiconductor films, chinese physics b 28: 048503. doi: 10.1088/1674-1056/28/4/048503 zou g, chen w, liu r and xu z (2008), morphology-tunable synthesis and characterizations of mg(oh)2 films via a cathodic electrochemical process, materials chemistry and physics 107: 85-90. doi: 10.1016/j.matchemphys. 2007.06.046 zulkefle h, ismail ln, bakar ra and mahmood mr (2011), molar concentration effect on mgo thin films properties, in proceedings of the ieee symposium on industrial electronics and applications, langkawi, malaysia, pp 468-471. doi: 10.1109/isiea.2011.6108754. lal, kumar, chawla, sharma and lal 127 mgo was known asa low-cost and environment-friendly material that has so many applications like bioresorbable materials that dissolve in biofluids (huang, 2018), drug delivery (ravaei et al. 2019), electrodes in pharmaceuticals and human fluids (kairya et al. 2017), resistive switching (guo et al. 2019), luminescence (nikiforov et al. 2016), photo-catalytic properties (demirci et al. 2015) and ultra-violet (uv) photodetector (zhou et al. 2019). mgo nanostructures have also been reported to exhibit thermoluminescence (abramishvili et al. 2011), radioluminescence (skvortsova and trinkler 2009), and electroluminescence (benia et al. 2007). thin metal oxide films that are electrically insulating are a crucial component of many different technologies, so magnesium oxide (mgo) has received a lot of attention for applicationssuch as spintronic devices since it has a material with a reasonably high dielectric constant. under the influence of uv light, methyl orange, and methylene blue dyes were degraded using the photocatalytic activity of mgo nanoparticles (mageshwari et al. 2013). hydrogen storage properties of mg/ti bilayer thin films were reported (jangid et al. 2021) at a different hydrogen pressure of 15 to 45 psi to realize the effect of hydrogenation. hydrogen is the lightest element in the universe, which is typical to detect and magnesium is very sensitive to hydrogen in comparison to other metals. (chawla et al. 2022). although magnesium (mg) is one of the better aspects for absorbing hydrogen, difficult to use this material for mobile applications due to its slow dynamics and need for high temperatures during dehydrogenation. due to its extremely large reversible hydrogen capacity, magnesium hydride is particularly intriguing (jangid et al. 2021). the present work reports the electrical behaviour and sensitivity of magnesium oxide (mgo) asa sensor to sense h2 gas. in a similar work dip-coated cuo thin films were used to investigate the gas-sensing response of co2 vapor in air at room temperature and reported that the physical qualities that can be altered have a lot of potential for co2 gas-sensing applications. (musa et al. 2021). for the synthesis of thin films with nanostructures, an easy, affordable, and solution-based hybrid method is electro-deposition. mgo nanostructures have been grown successfully from an aqueous solution of magnesium nitrate mg(no3)2 using the electrodeposition method (taleatu et al. 2014). the deposition procedure can be applied to a variety of conductive substrates, including polymers, semiconductors and ito-coated glass. indium tin oxide (ito) is the most widely used substrate because of its outstanding transparency to visible light and high electric conductivity (muchuweni et al. 2017). in the present work, magnesium oxide nanostructure thin film deposited by electrode position technique using magnesium nitrate solution. to synthesize mgo nanostructure, a variety of experimental procedures have been proposed, including reactive sputtering (choi and kim 2004), metal-organic molecular beam epitaxy (niu et al. 2000), chemical vapor deposition (carta et al. 2007), sol-gel (zulkefle et al. 2011), and pulsed laser deposition (kaneko et al. 2013). materials and methods a conventional homemade two-electrode electrochemical bathsetup with labelled diagram shown in fig. 1(b) was used in which graphite sheet was used as a counter electrode and ito coated glass substrate as a working electrode. both electrodes were introduced in the bath through two steel tubes. the electrolyte solution of 0.25 m concentration was prepared using magnesium nitrate mg(no3)2 salt. before the deposition process, the ito-coated glass substrate was extensively cleaned in an ultrasonic bath and rinsed with ultrapure water prior to the deposition in order to remove any surface impurities. by applying a potential difference of 2.5 v at room temperature for 30 minutes by htc power supply dc 3002, a thin layer of mgo nanostructures was deposited on ito substrate. the deposited sample was dehydrated up to 350oc at a heating rate of 10oc/min in a furnace shown in fig. 1(c) and hold for 90 minutes and thencooled at natural/normal atmosphere conditions, finally, mgo nanostructure was formed. characterization of the nanostructure shimadzu uv-2600 uv-visible spectrometer was used to analyze the optical characteristics, and fourier transform infrared spectrometer (ftir) bruker alpha was used to collect data about various functional groups present in the samplein the range 4000–500 cm-1. the structural and morphological characterization of the deposited nanostructure thin films was characterized by x-ray diffraction (xrd, model: a siemens d-5000 x-ray diffractometer) using cu-kα [1.54å] radiation. the kinetic energy distribution of photoelectrons released from the specimen material was measured using x-ray photoemission spectroscopy (model: omicron esca (electron spectroscope for chemical analysis) oxford instrument germany). in this model aluminium anode was used for samplesthat have energy 1486.7 ev. sem (model: jsm-7610f plus & make: jeol) was used to analyze the surface morphology and microstructure of deposited mgo nanostructures. the i-v characteristics for hydrogensensing were measured by using a keithley electrometer 6517a and a pressure-composition-isotherm (pci) setupat vacuum (1 *10-3 mbar) and by introducing hydrogen (at 5 bar) in the stainless-steel chamber. results and discussion following equations (i-iv) show the overall chemical reaction for the deposition of mgo nanostructure thin film using magnesium nitrate salt in aquas medium (hashaikeh and szpunar 2009). x-ray diffraction (xrd) analysis diffraction measurement was carried out with an angular scanning range of (20° – 80°) to explore the nature of the material, purity, and crystallinity of the sample. fig. 2 shows the xrd pattern of synthesized nanostructure thin films. in fig. 2, spectrum (a) shows xrd pattern of theusedito substrate, (b) shows the xrd pattern of thin film before annealing and (c) shows the xrd pattern of thin film after annealing. as discussed in equation (iii) and (iv) the xrd pattern represented by fig. 2(b) for mg(oh)2 and fig. 2(c) for mgo. the substrate peak marked by (*) is visible after post annealing at 350°c when conversion of mg(oh)2 into mgo nanostructure at ito substrate (alsultany et al. 2014). fig. 2(c) has distinctive sharp peaks correspond to (111), (200), (220) and (222) planes related to fcc structure (cvetkovic et al. 2018). the sharp peaks illustrate that the synthesized nanostructure has a good crystalline nature. the debye-scherrer equation (ashok et al. 2016) was used to compute the crystallite size d (nm). where λ, β, and 2θ were the wavelength of the incident x-ray beam (cu kα1.54 å), full width at half maximum (fwhm) in radian and bragg’s diffraction angle of the preferred orientation. the mean calculated crystalline size (d) for the deposited nanostructure was determined to be approximately 36 nm. a surface-sensitive spectroscopic method (xps) was used to determine the various elements present in a material (also known as its elemental composition), as well as their chemical state, general electronic structure, and density of their electronic states. the investigations about surface composition and chemical state of deposited mgo nanostructures using core-level light emission were reported and shown in fig. 3. it was clear from the survey scan (fig. 3a) that the deposited nanostructures were the mgo nanostructure during the synthesis process and no substantial pollutant was present in the sample. in the survey scan of the sample, the presence of carbon (c), oxygen (o), and magnesium (mg) elements and no major contaminant can be seen which validate by the elemental signals received. contamination of carbon was due to the environmental presence during the synthesis process which can be seen in fig. 3a. the mg 1s core level at 1302.8 ev is the peak with the highest intensity in the spectrum of deposited mgo nanostructure. the peak observed at 531.64 ev corresponds to o2− in the lattice of mgo. the core level spectra of mg2p were also shown in fig. 3d, where a gaussian peak of mgo at b.e. 50.91 ev was fitted using the casa xps software, and results indicate that the nanostructure of mgo was present with mg lattice, which also confirms the existence in the core level spectra of mg 1s (fig. 3b) and o 1s (fig. 3c) where mgo peak also present with lattice oxygen in the sample. the mg 2p peak analysis in fig. 3d demonstrates that mg remains in a single chemical state throughout the development process, and the characteristic b.e determines its oxidation. the binding energy of all peaks related to elemental composition with the electronic state in the survey scan from fig. 3(a) is tabulated as follows: scanning electron micrograph (sem) analysis the sem micrographs of the deposited mgo nanostructured thin films were obtained and shown in fig. 4 together with the chemical elemental mapping. the inset table provides information about the elements which were found in the deposited nanostructure. the results indicate that the mgo nanostructure was synthesized with porous surface and deposited accurately by this method. as the number of porous was more on surface of deposited film than it would be easy for detecting the gas by increasing the amount of active area that is available for gas adsorption (liu et al. 2014; liu et al. 2016; musa et al. 2021). the chemical compositions of the deposited nanostructure thin film on ito substrate are also measured by edx detector which is inbuilt into sem. it is also evident that the nanostructure was adequately present in the form, which supports the xps results. uv-visible analysis the absorption spectra of the synthesized magnesium oxide nanostructure thin films were obtained in the range of 200 and 800 nm using uv-visible spectrometer. tauc's formula in equation (vi) was used to calculate the band gap of synthesized mgo nanostructure (tauc et al. 1966) where α, h, ν, c and eg are the absorption coefficient, plank’s constant, frequency of the incident photon, a constant, and the direct transition band gap respectively. the uv-visible spectra were shown in fig. 5, in which fig. (a) indicates the absorbance spectrum (b) represents tauc’s plot to determine the optical band gap while fig. (c) denotes the derivative of absorbance versus energy for verification of band gap and (d) transmittance spectrum for the deposited mgo nanostructure. the calculated band gap with the help of the above equation and extrapolation of the curve as shown in fig. 5(b) was found about 4.16 ev, which is less than the band gap of bulk magnesium oxide (7.8 ev) as reported by many authors (bilalbegovic et al. 2004; guney et al. 2018; egwunyenga et al. 2019; baghezza, 2019). the band gap was also verified by the derivative versus energy curve which has a peak at 4.2 ev as shown in fig. 5(c). the resultant curve was linear throughout a wide range of photon energy, showing that the deposited nanostructure was a direct transition material. the band gap of metal oxide nanostructure decreases due to presence of defect states, so these defectstates are responsible for the large difference in band gap energy. both nanoparticles and nanostructures exhibit the same trend in band gap energy fluctuation however, nanostructures have a lower band gap energy than nanoparticles of the same size because of increased lattice strain and a larger surface to volume ratio (abdullah et al. 2022). guney and iskenderoglu, (2018) found that the band gap of mgo nanostructures varied with thickness from 4.31 to 4.61 ev and that the band gaps were decreased as sample thickness increased. the reduction in band gap may be related to variations in the atomic distance with the rise in film thickness. tlili et al. (2021) studied the variation of band gap from 4.01 to 4.08 ev for different molar concentrations (0.05, 0.1, 0.15, 0.2 mol·l−1) of mg2+ ions by spray pyrolys is technique and reported that, as the molar concentration of mg2+ increases, the optical band gap decreases. ftir analysis ftir spectroscopy was used to detect the existence of organic or inorganic constituents in the deposited nanostructure, which was connected to various functional groups associated with specific absorbance peaks in the spectra. the ftir spectra of deposited mgo nanostructure thin film with transmission peaks ranging from 500 to 4000 cm-1 are shown in fig. 6. the peak obtained at 545 cm-1 indicates the stretching vibration of mgo. as a result of the chemicals used during the synthesis process, the sample also contained additional functional groups at various peaks corresponding to co2, -co, c-h and -oh, etc. electrical properties the electrical properties such as current-voltage (i–v) characteristics were measuredin vacuum and with hydrogen gas by keithley electrometer 6517a in the range from -3 volt to 3 voltat room temperature. this study provides detailed information about the electronic effects in presence of hydrogen gas on deposited mgo nanostructure thin film. the curve exhibits considerable nonlinearity compared to a thin mgo tunnel barrier. it can be seen from fig. 7 that in presence of hydrogen gas, the conductivity increases in forward bias as well as in reverse bias, which can be explained as the charge shift from hydrogen to the film structure because hydrogen acts like a donor element. this property of mgo offers useful information about gas sensing applications like hydrogen gas and also can be employed as hydrogen storage materials. a similar study has been reported for mg/ti bilayer thin films (jangid et al. 2021), mg-ni thin films (jangid and jangid, 2022) and for cdte/mn bilayer thin films (nehra et al. 2009) that show the hydrogen storage properties of these bilayer thin films. a stainless-steel sealed chamber containing the synthesized sample was usedto measurecurrent-voltage characteristics while exposed to h2 gas in vacuum. the block diagram and pci/pct set up sown in fig. 8. the resistance response of synthesized mgo thin film was converted into a sensitivity value using equation (vii) (moumen et al. 2019; musa et al. 2021). where r0 stands for the film's resistance in vacuum, and rg for its resistance after being exposed to h2 gas. using equation (vii), the mgo nanostructure's sensitivity response to h2 gas was estimated to be about 31%. conclusion the mgo nanostructure thin film was synthesized on ito-coated glass substrate at room temperature by a simplified electrodeposition method using aqueous solution of magnesium nitrate and investigated by different characterization techniques. a cubic structure of mgo with a predicted crystalline size of about 36 nm was calculated by xrd investigation. the sem-edx image confirms the porous structure, adherent to the substrate and atomic % of available elements in the deposited mgo nanostructure thin films. the elemental composition and chemical states with binding energy were obtained using xps. the uv-visible analysis confirmed the optical band gap of the deposited nanostructure was ~ 4.16 ev. the i-v characteristics of deposited nanostructure suggest the partial semiconductor nature and the conductivity increases in presence of hydrogen. the sensitivity response of deposited nanostructure was approximately 31% on exposure to h2 gas. the deposited mgo nanostructures provide useful information about gas sensing applications such as hydrogen gas and also can be employed as hydrogen storage materials. the ultrafine nanostructures (such as qds etc.) provide a large and sensitive surface area for a promising solution to decrease the operating temperature for metal oxide semiconductor-based gas sensors (liu et al. 2014; liu et al. 2016). their high surface energy allows for the absorption of gas molecules even at room temperature for the sensing application. acknowledgement this research work was performed in dept. of physics, university of rajasthan, jaipur, india. the author is high thanks to the director cncer, university of rajasthan, jaipur, rajasthan india for providing characterization facilities. references abdullah bj (2022), size effect of band gap in semiconductor nanocrystals and nanostructures from density functional theory within hse06, materials science in semiconductor processing, 137: 106214. doi: 10.1016/j.mssp.2021.106214. abramishvili m, akhvlediani z, galustashvili m, dekanozishvili g, kalabegishvili t, kvatchadze v and tavkhelidze v (2011), peculiarities of radiation effects in mgo: mn2+ crystals, journalof modern physics 2: 841–844. doi:10.4236/jmp.2011.28099. alsultany fh, ahmed nm and matjafri mz (2014), effects of cw co2 laser annealing on indium tin oxide thin films characteristics, soft nanoscience letters 4(04): 83. doi: 10.4236/snl.2014.44012. ashok c, rao kv, chakra cs and rao kg (2016), mgo nanoparticles prepared by microwave-irradiation technique and its seed germination application, nano trends: a journal of nanotechnology and its application 18: 10-17. doi: 10.3390/nano11113076 baghezza mohammad (2019), optical and electrical properties of mgo thin films. khider university, m. l. b. m. m, http://a rchives. univbiskra. dz/ handle/ 123456 789/13780. bilalbegovic, g. (2004), structural and electronic properties of mgo nanotube clusters, physical review b 70(4): 045407. doi: 10.1103/physrevb.70.045407. benia hm, lin x, gao hj, nilius l and freund hj (2007), nucleation and growth of gold on mgo thin films: a combined stm and luminescence study, journal of physical chemistry c111: 10528-10533. doi:10. 1021/jp0726891 bhatte kd, sawant dn, deshmukh km, bhanage bm, rusdi r, kamarudin n, llanos m and lopez-salinas (2012), additive free microwave assisted synthesis of nanocrystalline mg(oh)2 and mgo, the lancet 10: 384-387. doi: 10.1016/j.partic.2011.05.004 carta g, habra n el, crociani l, rossetto g, zanella p, paolucci g, barreca d and tondello e (2007), cvd of mgo thin films from bis(methylcyclopentadienyl) magnesium, chemical vapor deposition 13(4): 185-189. doi:10.1002/cvde.200606574 chatterjee s, gohil s, chalke band ayyub p (2009), optimization of the morphology of zno nanorods grown by an electrochemical process, journalof nanoscience and 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properties, in proceedings of the ieee symposium on industrial electronics and applications, langkawi, malaysia, pp 468-471. doi: 10.1109/isiea.2011.6108754. synthesis of mgo nanostructure thin films via electrodeposition method 58(2) 2023128 53 electronic, structural and optical properties of gd-doped zno powder synthesized by solid-state reaction method m. k. gora1*, a. kumar1, b. l. choudhary2, s. n. dolia1, s. kumar1 and r. k. singhal1 1department of physics, university of rajasthan, jaipur-302004, rajasthan, india 2department of physics, bansathalividhyapith, banasthali-304022, rajasthan, india abstract we explored the impact of gd doping on the structural, electronic and optical characteristics of the zno powder. the gd-doped zno (0, 2% and 5%) powder samples have been synthesized using the conventional solid-state reaction process with varied gd concentrations. the xrd pattern confirmed that all the studied samples are in the hexagonal wurtzite crystalline structure. the morphology has been explored using sem images, which exhibited an agglomerated rod-like particle structure. the xps results indicate the presence of oxygen vacancies (vo) in the gd-doped zno samples and the vo’s are found to increase with increasing gd amount. according to pl findings, the intensity ratio of the green and ultra-violet emission peaks is found to increase from 0.090 to 0.418 with increasing gd-doping concentrations, confirming that vo’s are increasing with gd-doping. the uv-visible spectroscopy results reveal that the energy band gap (eg) decreased from 3.31 ev to 3.23 ev with increasing gd-doping concentration. keywords: polycrystalline; rietveld refinement; wurtzite structure; oxygen vacancies; xps; pl *corresponding author e-mail: gora.phy@gmail.com available online at www.banglajol.info bangladesh j. sci. ind. res. 58(1), 53-64, 2023 introduction diluted magnetic semiconductor materials are used in optoelectronic and magneto-electronic devices that involve electron charge and spin (thangeeswari et al. 2015). when a traditional semiconductor like zno is doped with transition metal (tm) ions or rare-earth (re) metals, the dms material could realize. numerous applications in the spintronics of zinc oxide have piqued the curiosity of researchers. the wide band gap energy of the zno is 3.37 ev and the exciton binding energy is 60 m ev, making it perfect for use in light-emitting diodes (shimogaki et al. 2015; thangeeswari et al. 2015). the magnetic, optical, and electrical characteristics of zno could be modified by the doping of tm ions and re elements, which depend on the dopants' nature, quantity, and synthesis process (deshmukh et al. 2010). in particular, zno is receiving much attention as a potential material for uv and visible light emitters (ozgür et al. 2005; fan et al. 2013). the visible emission of zno is because of several bands associated with various lattice flaws. consequently, defect-related emission in zno displays a wide unstructured band spanning the blue to red spectral regions. because of this uniqueness, zno is a promising phosphor for white-light emitters with a high colour rendering index (fan et al. 2013). zno has unique characteristics like affordability, long-term stability, an environmentally friendly nature, better radiation resistance, etc. additionally, zno is an excellent material for several photonic applications when doped with a suitable dopant (bahadur et al. 2007). doping is a valuable method for modifying the optical characteristics of zno due to its ability to exhibit many absorption transitions in the visible region. re elements, such as gd, may introduce additional capabilities to the zno system because they may be capable of constructing combined practical devices on a single chip by combining magnetic and optical properties (ohno et al. 1996; tawil et al. 2011). rare-earth (re) metal doping in the dilute magnetic semiconductor (dms) systems has recently received immense attention due to its potential usage in magneto electronic and photonic devices (monteiro et al. 2006). the influence of gd doping on the optical and electrical properties of zno is crucial for developing optoelectronic devices and understanding the genesis of ferromagnetism. ma and wang (2012) synthesized the gd-doped zno nanocrystals using the thermal evaporation deposition method. according to their findings, gd doping has an appreciable impact on the optical characteristics of the zno. the strong uv and blue emissions are detected at low gd concentrations because gd impurities introduce a mid-gap state into zno. in comparison, the uv and blue emissions reduce for high doping concentrations as a significant broad defect emission appears because of the vast numbers of defects, impurities, and excess gd2o3 produced. gd-doped zno nanocrystals can be used in optoelectronic devices. the optical and electrical tuning of the carrier density and optical band gap energy is essential for developing luminescent materials and equipment based on the zno dms systems. the optical band gap and carrier concentration are essential parameters to yield information about the emission wavelength. several development characteristics, like the synthesis methods, impurity concentration and substrate variety have been reported to influence these parameters (wakano et al. 2001; tan et al. 2011; murtaza et al. 2011). the synthesis of dms materials with unique optical, photocatalytic and magnetic characteristics seems to be the most promising candidate for the subsequent generation of electronic, optoelectronic and spintronic appliances (kumar and sahare 2014). the low-dimension materials with imperfection-free lattice structures have excellent electrical and magnetic characteristics; purposefully made or accidental structural defects play a significant role in altering their features (li et al. 2016; obeid et al. 2018). thus, the presence of different kinds of cation or anion vacancies and interstitials in zno nanocrystals may change their magnetic properties, photoluminescence, and photocatalytic properties (coey et al. 2005). although certain experimental and theoretical findings based on dft indicate that gd-doped zno exhibits the room temperature ferromagnetism (rtfm) (potzger et al. 2006; aravindh et al. 2014) property, several studies have demonstrated that the rtfm is not present (sambasivam et al. 2015). in addition to their magnetic qualities, the 4f ions eth 30 kv evo-18 carl zeiss, with a tilt of 0° to 60° and a rotation of 360°, has been used for taking sem images.the defect-related states and chemical analysis of the samples have been determined using x-ray photoelectron spectroscopy. a hemispherical analyzer with a 128-channel detector and a monochromated, fully integrated k-alpha small-spot x-ray photoelectron spectrometer system of 180° double focusing is used in xps (thermo scientific made). the uv-visible absorption spectroscopy (model: shimadzu uv-3600 uv-vis-nir spectrophotometer) was used to explore the prepared samples' optical absorption and band gap. the measurements of uv-visible absorption spectra have been taken using the powder form of the samples. pl spectroscopy was used to analyze defect-related states in the prepared samples. photoluminescence spectra have been recorded at room temperature using the fluorescence spectrometer (model: perkin elmer fl 8500). results and discussion xrd analysis fig. 1. depicts the powder xrd patterns of the gd-doped zno (gd = 0%, 2%, and 5%) samples. all the diffraction peaks detected in the zno sample match with the standard jcpds card number (36-1451). this confirms a hexagonal wurtzite crystal structure of the samples. the diffraction peaks were observed at 31.88°, 34.50°, 36.25°, 47.72°, 56.69°, 63.03°, 66.59°, 68.17°, and 69.35°, which are related to the planes (100), (002), (101), (102), (110), (103), (200), (112), and (201), respectively (ganesh et al. 2018; bharathi et al. 2020). further, some additional small peaks have been observed at 28.61°, 33.21°, and 39.14° with increasing gd doping. these secondary peaks representing a crystallite phase have been identified as gd2o3, which is well consistent with earlier reports (das et al. 2012). as shown in fig. 2, the highest intense peak related to the (101) plane shifted slightly higher angles with the increasing concentration of gd doping. the shift is because of the substitution of bigger-sized gd3+ (0.94 å) ions than zn2+ (0.74 å) ions in the hexagonal wurtzite structure. the peak shift may indicate that gd3+ ions have occupied the crystallographic positions of zn2+ ions in the zno host lattice, or itmay be because of the structural strain caused by the formation of internal compressive micro stress (dakhel and el-hilo 2010; kumar et al. 2014; sahu et al. 2017). rietveld refinements have been performed using the full prof programme (shown in fig. 3). the pseudo-voigt function has been used for rietveld refinement of all the samples with the space group p63mc. the estimated lattice parameters have been listed in table i. the lattice parameters are found to decrease with gd doping, similar to those reported in earlier studies (kaur et al. 2016; obeid et al. 2019). the factors like the induced deficiencies (vacancies, interstitial) and the ionic radius of zn and gd ions can be responsible for the observed change (kaur et al. 2016; kumar and thangavel 2017). sem analysis scanning electron micrographs have been used to analyze the morphology of the gd-doped zno powder samples. the sem images reveal a rod-like morphology in pure zno (gora et al. 2022) and the gd-doped zno polycrystalline samples with some proof of agglomeration and phase segregation, as depicted in fig. 4 (a, b and c). profound observation of the particles exhibits that the crystallite size is above 100 nm. the particles were intensive and incompatibly distributed all over the mass. a distinct boundary between neighbouring crystallites can be noticed, despite the proximity of these smaller crystallites. xps analysis the xps technique is an excellent tool for determining the surface chemistry and electron configuration of the various elements present in a multicomponent material. the carbon c1s peak (284.6 ev) has been used as a reference to calibrate all the binding energies of the spectra. the survey spectrum of the gd-doped zno samples is shown in fig. 5. the survey spectra revealed the existence of o, zn, and gd elements without any impurity in the samples. for zno and 2% gd-doped zno powder samples, the binding energies of the zn2p3/2 and zn2p1/2 peaks are found to be 1021.25 ev, 1044.25 ev, 1021.43 ev, and 1044.43 ev, respectively. however, for the 5% gd-doped zno sample, these peaks are at 1021.83 and 1044.83 ev energy positions. the small shift could be assigned to the creation of zn interstitials in zno upon gd doping. the binding energy gap between the zinc doublet peaks has been found at about 23 ev. this indicates that zn in the zno crystal structure is in the zn2+ oxidation state (khataee et al. 2015; gawai et al. 2019) as the spin-orbital splitting of zn2p is 23 ev. this difference does not change with the gd doping pointing out that gd doping has no discernible effect on the chemical position of zno. the o1s asymmetric xps spectraare shown in fig.7 (a) which is asymmetric in shape. the o1s xps spectra of all these samples i.e. the zno, the zn0.98gd0.02o, and the zn0.95gd0.05o have been deconvoluted mainly into two gaussian peaks, as shown in fig. 7 (b, c, and d). the lower binding peaks for pure and gd-doped zno (gd = 2% and 5%) polycrystalline samples have been detected at 529.93 ev, 529.93 ev and 529.78 ev, respectively, which attributed to the lattice oxygen in the hexagonal structure of the zno. the higher binding peak for the pure and the gd-doped zno samples have been found at 531.51 ev, 531.66 ev, and 531.49 ev, respectively, which is due to the presence of oxygen vacancies in the zno structure (bharathi et al. 2020; sukumaran et al. 2021). an additional signal centered at 528.29 ev has been detected in the 5% gd-doped zno powder sample, which could be ascribed to the coordination of oxygen in gd-o-zn along grain boundaries because of the excessive gd dopants and also attributed to the presence of gd2o3 in the sample (yi et al. 2017). the lattice oxygen peak has slightly shifted to the lower binding energy with increasing gd concentration, which has been due to the increased oxygen vacancies with increasing gd doping. the estimated area ratios of the oxygen vacancies peak and the lattice oxygen peak for the samples zno, zn0.98gd0.02o, and zn0.95gd0.05o comes out to be 0.53, 1.30, and 2.49, respectively. these results show that the oxygen vacancies increase with increasing gd concentration. the fig. 8 (a, b) depicts the high-resolution gd4d xps spectra of the gd-doped samples.in the gd4d state, the spin-orbit splatted peaks are at 144.6 ev for gd4d3/2 and 139.6 ev for gd4d5/2 for the 2% gd-doped sample, whereas for the 5% gd-doped zno sample, the spin-orbit splits at 145.5 ev for gd4d3/2 and 139.7 ev for gd4d5/2 as shown in fig. 8 (a, b). this indicates that gd is present in the gd3+ state in the zno hexagonal structure. the shift in peak values of gd4d3/2 and gd4d5/2 from 144.6 ev and 139.6 ev, respectively; in the case of 2% gd-doped sample to 145.5 ev and 139.7 ev, respectively, in the case of 5% gd-doped sample. this shift in gd4d peaks is ascribed to the electron transfer from plasmonics gd to zno because of the strong electronic interaction (covalent bond) between gd and the oxide (ahmad et al. 2011; wang et al. 2012; bharathi et al. 2020). uv visible spectroscopy analysis the uv–visible spectroscopy is a powerful tool for estimating band gap of materials. uv–vis absorbance spectra and tauc plots for the gd-doped zno samples (gd = 0% (gora et al. 2022), 2%, and 5%) samples are shown in figs.9 (a, b, c, and d). the spectra show a red shift with increasing gd amount in the zno.the uv–vis absorption intensity of the synthesized polycrystalline samples is found to reduce with the increasing gd concentration (mazhdi and tafreshi 2018). tauc's plot has been used to calculate the direct band gap of the samples (jain et al. 2006). the direct band gap has been estimated using the following equation: here, α is the absorption coefficient,υ is frequency, h is the planck constant, a is a constant, and eg is the energy band gap of the substance. extrapolating the linear component of the curve plotted among (αhυ) 2 and hυ depicted in fig. 9 (b, c, and d) has been used to obtain the band gap (farhad et al. 2018; ghos et al. 2021). the band gap values calculated for the gd-doped zno samples, i.e.are 3.31 ev (gora et al. 2022), 3.27 ev, and 3.23ev, for the samples gd = 0%, 2% and 5%, respectively. the small redshift observed in the band gap of gd-doped zno samples is because of the changes in electronic structure as well as enhanced oxygen vacancies with the increasing gd doping (yi et al. 2017; flemban et al. 2016), which is responsible for the band gap reduction. photoluminescence spectroscopy analysis the structural flaws like ionic and atomic vacancies, replacements and interstitials have been explored using the pl spectra of the synthesized polycrystalline samples. fig. 10 (a, b and c) shows the deconvoluted, gaussian-fitted pl spectra of the synthesized gd-doped zno polycrystalline powder samples. the pl spectra of the samples were recorded at room temperature in order to determine the types of vacancies, defect band emission etc. (lin et al. 2001; yi et al. 2017). the photoluminescence spectra have been deconvoluted and the different peaks responsible for the emission have been gaussian fitted. for these samples the band edge emission peaksare detected at 381 nm, 384 nm, and 383 nm, for the gd = 0%, 2% and 5% samples, respectively. the uv emission is responsible for the excitonic interaction related to the band edge emission. the intense violet emission exhibited in the gd-doped zno at about 415 nm could be because ofthe oxygen vacancies. the exciton interaction between the holes in the valence band and electrons located in the interstitial zinc could be responsible for the violet emission peak at about 447 nm. intrinsic deficiencies like interstitial zinc and oxygen can be attributed to the peak at 477 nm (singh et al. 2009; kaur et al. 2016). the transformation between singly ionized oxygen deficiency and the photo-created holes (kennedy et al. 2014) or the surface imperfection and electrons near the conduction band, might be responsible for the green emission peak seen for the gd-doped znoat around 525 nm. the green emissions are commonly attributed to theoxygen vacancies (studenikin et al. 1998). for gd-doped zno polycrystalline powder samples, the intensity ratio of the green and ultra-violet emission peaks is found to be 0.090 for zno, 0.204 for the 2% gd-doped zno, and 0.418 for the 5% gd-doped zno. the defect-related emissions enhanced with increasing gd doping in the zno indicate that a large number of deficiencies, such as oxygen vacancies, are most usually related to crystal deformation (yi et al. 2017). the results reveal that the gd doping enhances the zni and vo flaws. it could be attributed to structural deformation created by gd atoms with different ionic sizes than zn in the zno (bandopadhyay and mitra 2015; sukumaran et al. 2021). increasing gd doping in zno indicates an increase in defect states, which matches well with the xps results. we compared our pl results with farhad et al. (2019), who prepared zno dc (drop casting) and zno nanorods. their pl results detected the pl peak at 380 nm and a barely observable green-yellow emission peak; in our case, we find it at 381 nm for zno, 384 nm for 2% gd-doped zno and 383 nm for the 5% gd-doped zno polycrystalline sample. this peak represented zno's near band edge (nbe) transition because of free excitons recombinations and this pl property indicates high crystalline quality. the luminescent characteristics in the visible region are responsible for the different defects, like zinc interstitials (zni), oxygen vacancies (vo), etc., present in the zno crystal matrix. as a result, they reported that both zno (dc) and zno nanorods were found to be defect-free good crystalline and optical properties materials. in our case, all the prepared gd-doped zno powder samples have been found to be with single ionized oxygen vacancies, which are confirmed by the green emission peak at 525 nm in the pl spectra. conclusion the gd-doped zno powder samples were synthesized by the solid-state reaction method. the xrd patterns affirm that gd has been successfully incorporated into the zno lattice and confirm the hexagonal wurtzite structure. sem images have been used to reveal the morphologies of the synthesized samples, which appear as rod-like structures. the xps results showed that the oxygen vacancy-related states in gd-doped samples increased with increasing gd doping. pl findings confirmed that the defect-related states are present in the gd-doped zno polycrystalline samples. the green emission and ultra-violet emission peaks' intensity ratio is 0.418 for the 5% gd-doped zno sample, which is the maximum compared to the pure zno and 2% gd-doped zno polycrystalline powder sample. these findings confirmed that the oxygen vacancies increase as the gd concentration increases and the pl results agree well with the xps results. the uv absorption spectra findings reveal that the band gap in the 5% gd-doped zno sample is found to be 3.23 ev, which is the minimum compared to both the pure zno and the 2% gd-doped zno samples, confirming that eg is reduced with increasing gd concentration. acknowledgment the authors are thankful to usic, university of rajasthan, jaipur, rajasthan (india), for providing sem images of the prepared samples. we also thank department of physics, banasthalividhyapith, banasthali, jaipur, rajasthan (india) for rendering xrd data. funding sources this research is not financed by any agency. authors' contribution sample preparation, data analysis, manuscript composition and writing (mahendra kumar gora); 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properties of gd doped zno films, thin solid films. 636: 339-345. https://doi.org/10.1016/j.tsf.2017.05.020 doped zno nanocrystals also have an attractive optical responsiveness. many theoretical and experimental studies showed that re-doped zno could reportedly absorb ultraviolet (uv) light (chakraborty et al. 2017). obeid et al. (2019) prepared undoped and gd-doped zno nanocrystalline samples using the thermal decomposition method. they observed that the optical absorption spectra of pristine zno increased with a 6% gd doping concentration and the magnetic properties changed with changing dopant amounts. their pl spectroscopy results showed the existence of defects, which increased with increasing gd doping concentrations. they suggested that these dms nanoparticles can be used for magneto-optoelectronic practical device applications. undoubtedly, the re-doped zno nanostructures have been intensively studied recently because this is a rapidly growing field due to their multi-functionality and their use in possible new generation applications. with an aim to understand the effect of gd doping in zno in terms of its electronic and optical properties we have synthesize gd-doped zno powder series of different gd (0%, 2%, and 5%) values. various characterization techniques have been utilized to explore the electronic, structural and optical features of the synthesized powder series. gd doping into zno produced changes in the band gap and enhanced oxygen vacancies related states in the compound. materials and methods the gd-doped zno powder samples with varying gd (0%, 2%, and 5%) concentrations have been synthesized using the conventional solid-state reaction method. a suitable amount of high-purity (99.999% sigma-aldrich) zinc oxide (zno) and gadolinium oxide (gd2o3) powder have been used for their preparation. for achieving perfect homogeneity, the ingredients were properly pounded for ~8 hours in an agate mortar and pestle. the prepared material has been sintered for ~8h at~550°c and cooled at room temperature. again, the mixture was ground for ~2 hours and sintered for ~6 hours at ~550°c. the mixture was milled for ~4 hours before being turned into pellets. finally, these pellets were sintered for around ~8 hours at about ~600°c. finally, we ground the pellets to make the powder. the powder form of the prepared samples has been used for further characterization. characterization techniques the crystallographic structures of the samples have been explored using an x-ray diffractometer (make: panalytical x'pert pro) using the photon energy of cu kα (λ= 1.5406å). sem images have been used for the morphology study of the synthesized samples. the sem equipment model electronic, structural and optical properties of gd-doped zno powder 58(1) 202354 re elements, such as gd, may introduce additional capabilities to the zno system because they may be capable of constructing combined practical devices on a single chip by combining magnetic and optical properties (ohno et al. 1996; tawil et al. 2011). rare-earth (re) metal doping in the dilute magnetic semiconductor (dms) systems has recently received immense attention due to its potential usage in magneto electronic and photonic devices (monteiro et al. 2006). the influence of gd doping on the optical and electrical properties of zno is crucial for developing optoelectronic devices and understanding the genesis of ferromagnetism. ma and wang (2012) synthesized the gd-doped zno nanocrystals using the thermal evaporation deposition method. according to their findings, gd doping has an appreciable impact on the optical characteristics of the zno. the strong uv and blue emissions are detected at low gd concentrations because gd impurities introduce a mid-gap state into zno. in comparison, the uv and blue emissions reduce for high doping concentrations as a significant broad defect emission appears because of the vast numbers of defects, impurities, and excess gd2o3 produced. gd-doped zno nanocrystals can be used in optoelectronic devices. the optical and electrical tuning of the carrier density and optical band gap energy is essential for developing luminescent materials and equipment based on the zno dms systems. the optical band gap and carrier concentration are essential parameters to yield information about the emission wavelength. several development characteristics, like the synthesis methods, impurity concentration and substrate variety have been reported to influence these parameters (wakano et al. 2001; tan et al. 2011; murtaza et al. 2011). the synthesis of dms materials with unique optical, photocatalytic and magnetic characteristics seems to be the most promising candidate for the subsequent generation of electronic, optoelectronic and spintronic appliances (kumar and sahare 2014). the low-dimension materials with imperfection-free lattice structures have excellent electrical and magnetic characteristics; purposefully made or accidental structural defects play a significant role in altering their features (li et al. 2016; obeid et al. 2018). thus, the presence of different kinds of cation or anion vacancies and interstitials in zno nanocrystals may change their magnetic properties, photoluminescence, and photocatalytic properties (coey et al. 2005). although certain experimental and theoretical findings based on dft indicate that gd-doped zno exhibits the room temperature ferromagnetism (rtfm) (potzger et al. 2006; aravindh et al. 2014) property, several studies have demonstrated that the rtfm is not present (sambasivam et al. 2015). in addition to their magnetic qualities, the 4f ions eth 30 kv evo-18 carl zeiss, with a tilt of 0° to 60° and a rotation of 360°, has been used for taking sem images.the defect-related states and chemical analysis of the samples have been determined using x-ray photoelectron spectroscopy. a hemispherical analyzer with a 128-channel detector and a monochromated, fully integrated k-alpha small-spot x-ray photoelectron spectrometer system of 180° double focusing is used in xps (thermo scientific made). the uv-visible absorption spectroscopy (model: shimadzu uv-3600 uv-vis-nir spectrophotometer) was used to explore the prepared samples' optical absorption and band gap. the measurements of uv-visible absorption spectra have been taken using the powder form of the samples. pl spectroscopy was used to analyze defect-related states in the prepared samples. photoluminescence spectra have been recorded at room temperature using the fluorescence spectrometer (model: perkin elmer fl 8500). results and discussion xrd analysis fig. 1. depicts the powder xrd patterns of the gd-doped zno (gd = 0%, 2%, and 5%) samples. all the diffraction peaks detected in the zno sample match with the standard jcpds card number (36-1451). this confirms a hexagonal wurtzite crystal structure of the samples. the diffraction peaks were observed at 31.88°, 34.50°, 36.25°, 47.72°, 56.69°, 63.03°, 66.59°, 68.17°, and 69.35°, which are related to the planes (100), (002), (101), (102), (110), (103), (200), (112), and (201), respectively (ganesh et al. 2018; bharathi et al. 2020). further, some additional small peaks have been observed at 28.61°, 33.21°, and 39.14° with increasing gd doping. these secondary peaks representing a crystallite phase have been identified as gd2o3, which is well consistent with earlier reports (das et al. 2012). as shown in fig. 2, the highest intense peak related to the (101) plane shifted slightly higher angles with the increasing concentration of gd doping. the shift is because of the substitution of bigger-sized gd3+ (0.94 å) ions than zn2+ (0.74 å) ions in the hexagonal wurtzite structure. the peak shift may indicate that gd3+ ions have occupied the crystallographic positions of zn2+ ions in the zno host lattice, or itmay be because of the structural strain caused by the formation of internal compressive micro stress (dakhel and el-hilo 2010; kumar et al. 2014; sahu et al. 2017). rietveld refinements have been performed using the full prof programme (shown in fig. 3). the pseudo-voigt function has been used for rietveld refinement of all the samples with the space group p63mc. the estimated lattice parameters have been listed in table i. the lattice parameters are found to decrease with gd doping, similar to those reported in earlier studies (kaur et al. 2016; obeid et al. 2019). the factors like the induced deficiencies (vacancies, interstitial) and the ionic radius of zn and gd ions can be responsible for the observed change (kaur et al. 2016; kumar and thangavel 2017). sem analysis scanning electron micrographs have been used to analyze the morphology of the gd-doped zno powder samples. the sem images reveal a rod-like morphology in pure zno (gora et al. 2022) and the gd-doped zno polycrystalline samples with some proof of agglomeration and phase segregation, as depicted in fig. 4 (a, b and c). profound observation of the particles exhibits that the crystallite size is above 100 nm. the particles were intensive and incompatibly distributed all over the mass. a distinct boundary between neighbouring crystallites can be noticed, despite the proximity of these smaller crystallites. xps analysis the xps technique is an excellent tool for determining the surface chemistry and electron configuration of the various elements present in a multicomponent material. the carbon c1s peak (284.6 ev) has been used as a reference to calibrate all the binding energies of the spectra. the survey spectrum of the gd-doped zno samples is shown in fig. 5. the survey spectra revealed the existence of o, zn, and gd elements without any impurity in the samples. for zno and 2% gd-doped zno powder samples, the binding energies of the zn2p3/2 and zn2p1/2 peaks are found to be 1021.25 ev, 1044.25 ev, 1021.43 ev, and 1044.43 ev, respectively. however, for the 5% gd-doped zno sample, these peaks are at 1021.83 and 1044.83 ev energy positions. the small shift could be assigned to the creation of zn interstitials in zno upon gd doping. the binding energy gap between the zinc doublet peaks has been found at about 23 ev. this indicates that zn in the zno crystal structure is in the zn2+ oxidation state (khataee et al. 2015; gawai et al. 2019) as the spin-orbital splitting of zn2p is 23 ev. this difference does not change with the gd doping pointing out that gd doping has no discernible effect on the chemical position of zno. the o1s asymmetric xps spectraare shown in fig.7 (a) which is asymmetric in shape. the o1s xps spectra of all these samples i.e. the zno, the zn0.98gd0.02o, and the zn0.95gd0.05o have been deconvoluted mainly into two gaussian peaks, as shown in fig. 7 (b, c, and d). the lower binding peaks for pure and gd-doped zno (gd = 2% and 5%) polycrystalline samples have been detected at 529.93 ev, 529.93 ev and 529.78 ev, respectively, which attributed to the lattice oxygen in the hexagonal structure of the zno. the higher binding peak for the pure and the gd-doped zno samples have been found at 531.51 ev, 531.66 ev, and 531.49 ev, respectively, which is due to the presence of oxygen vacancies in the zno structure (bharathi et al. 2020; sukumaran et al. 2021). an additional signal centered at 528.29 ev has been detected in the 5% gd-doped zno powder sample, which could be ascribed to the coordination of oxygen in gd-o-zn along grain boundaries because of the excessive gd dopants and also attributed to the presence of gd2o3 in the sample (yi et al. 2017). the lattice oxygen peak has slightly shifted to the lower binding energy with increasing gd concentration, which has been due to the increased oxygen vacancies with increasing gd doping. the estimated area ratios of the oxygen vacancies peak and the lattice oxygen peak for the samples zno, zn0.98gd0.02o, and zn0.95gd0.05o comes out to be 0.53, 1.30, and 2.49, respectively. these results show that the oxygen vacancies increase with increasing gd concentration. the fig. 8 (a, b) depicts the high-resolution gd4d xps spectra of the gd-doped samples.in the gd4d state, the spin-orbit splatted peaks are at 144.6 ev for gd4d3/2 and 139.6 ev for gd4d5/2 for the 2% gd-doped sample, whereas for the 5% gd-doped zno sample, the spin-orbit splits at 145.5 ev for gd4d3/2 and 139.7 ev for gd4d5/2 as shown in fig. 8 (a, b). this indicates that gd is present in the gd3+ state in the zno hexagonal structure. the shift in peak values of gd4d3/2 and gd4d5/2 from 144.6 ev and 139.6 ev, respectively; in the case of 2% gd-doped sample to 145.5 ev and 139.7 ev, respectively, in the case of 5% gd-doped sample. this shift in gd4d peaks is ascribed to the electron transfer from plasmonics gd to zno because of the strong electronic interaction (covalent bond) between gd and the oxide (ahmad et al. 2011; wang et al. 2012; bharathi et al. 2020). uv visible spectroscopy analysis the uv–visible spectroscopy is a powerful tool for estimating band gap of materials. uv–vis absorbance spectra and tauc plots for the gd-doped zno samples (gd = 0% (gora et al. 2022), 2%, and 5%) samples are shown in figs.9 (a, b, c, and d). the spectra show a red shift with increasing gd amount in the zno.the uv–vis absorption intensity of the synthesized polycrystalline samples is found to reduce with the increasing gd concentration (mazhdi and tafreshi 2018). tauc's plot has been used to calculate the direct band gap of the samples (jain et al. 2006). the direct band gap has been estimated using the following equation: here, α is the absorption coefficient,υ is frequency, h is the planck constant, a is a constant, and eg is the energy band gap of the substance. extrapolating the linear component of the curve plotted among (αhυ) 2 and hυ depicted in fig. 9 (b, c, and d) has been used to obtain the band gap (farhad et al. 2018; ghos et al. 2021). the band gap values calculated for the gd-doped zno samples, i.e.are 3.31 ev (gora et al. 2022), 3.27 ev, and 3.23ev, for the samples gd = 0%, 2% and 5%, respectively. the small redshift observed in the band gap of gd-doped zno samples is because of the changes in electronic structure as well as enhanced oxygen vacancies with the increasing gd doping (yi et al. 2017; flemban et al. 2016), which is responsible for the band gap reduction. photoluminescence spectroscopy analysis the structural flaws like ionic and atomic vacancies, replacements and interstitials have been explored using the pl spectra of the synthesized polycrystalline samples. fig. 10 (a, b and c) shows the deconvoluted, gaussian-fitted pl spectra of the synthesized gd-doped zno polycrystalline powder samples. the pl spectra of the samples were recorded at room temperature in order to determine the types of vacancies, defect band emission etc. (lin et al. 2001; yi et al. 2017). the photoluminescence spectra have been deconvoluted and the different peaks responsible for the emission have been gaussian fitted. for these samples the band edge emission peaksare detected at 381 nm, 384 nm, and 383 nm, for the gd = 0%, 2% and 5% samples, respectively. the uv emission is responsible for the excitonic interaction related to the band edge emission. the intense violet emission exhibited in the gd-doped zno at about 415 nm could be because ofthe oxygen vacancies. the exciton interaction between the holes in the valence band and electrons located in the interstitial zinc could be responsible for the violet emission peak at about 447 nm. intrinsic deficiencies like interstitial zinc and oxygen can be attributed to the peak at 477 nm (singh et al. 2009; kaur et al. 2016). the transformation between singly ionized oxygen deficiency and the photo-created holes (kennedy et al. 2014) or the surface imperfection and electrons near the conduction band, might be responsible for the green emission peak seen for the gd-doped znoat around 525 nm. the green emissions are commonly attributed to theoxygen vacancies (studenikin et al. 1998). for gd-doped zno polycrystalline powder samples, the intensity ratio of the green and ultra-violet emission peaks is found to be 0.090 for zno, 0.204 for the 2% gd-doped zno, and 0.418 for the 5% gd-doped zno. the defect-related emissions enhanced with increasing gd doping in the zno indicate that a large number of deficiencies, such as oxygen vacancies, are most usually related to crystal deformation (yi et al. 2017). the results reveal that the gd doping enhances the zni and vo flaws. it could be attributed to structural deformation created by gd atoms with different ionic sizes than zn in the zno (bandopadhyay and mitra 2015; sukumaran et al. 2021). increasing gd doping in zno indicates an increase in defect states, which matches well with the xps results. we compared our pl results with farhad et al. (2019), who prepared zno dc (drop casting) and zno nanorods. their pl results detected the pl peak at 380 nm and a barely observable green-yellow emission peak; in our case, we find it at 381 nm for zno, 384 nm for 2% gd-doped zno and 383 nm for the 5% gd-doped zno polycrystalline sample. this peak represented zno's near band edge (nbe) transition because of free excitons recombinations and this pl property indicates high crystalline quality. the luminescent characteristics in the visible region are responsible for the different defects, like zinc interstitials (zni), oxygen vacancies (vo), etc., present in the zno crystal matrix. as a result, they reported that both zno (dc) and zno nanorods were found to be defect-free good crystalline and optical properties materials. in our case, all the prepared gd-doped zno powder samples have been found to be with single ionized oxygen vacancies, which are confirmed by the green emission peak at 525 nm in the pl spectra. conclusion the gd-doped zno powder samples were synthesized by the solid-state reaction method. the xrd patterns affirm that gd has been successfully incorporated into the zno lattice and confirm the hexagonal wurtzite structure. sem images have been used to reveal the morphologies of the synthesized samples, which appear as rod-like structures. the xps results showed that the oxygen vacancy-related states in gd-doped samples increased with increasing gd doping. pl findings confirmed that the defect-related states are present in the gd-doped zno polycrystalline samples. the green emission and ultra-violet emission peaks' intensity ratio is 0.418 for the 5% gd-doped zno sample, which is the maximum compared to the pure zno and 2% gd-doped zno polycrystalline powder sample. these findings confirmed that the oxygen vacancies increase as the gd concentration increases and the pl results agree well with the xps results. the uv absorption spectra findings reveal that the band gap in the 5% gd-doped zno sample is found to be 3.23 ev, which is the minimum compared to both the pure zno and the 2% gd-doped zno samples, confirming that eg is reduced with increasing gd concentration. acknowledgment the authors are thankful to usic, university of rajasthan, jaipur, rajasthan (india), for providing sem images of the prepared samples. we also thank department of physics, banasthalividhyapith, banasthali, jaipur, rajasthan (india) for rendering xrd data. funding sources this research is not financed by any agency. authors' contribution sample preparation, data analysis, manuscript composition and writing (mahendra kumar gora); 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351-354. https://doi.org/10. 1016/j.jcrysgro.2010.11.166 thangeeswari t, murugasen p and velmurugan j (2015), influence of co and dy doping on the optical and magnetic properties of zno nanoparticles for dms application, j. supercond. nov. magn. 28: 2505-2515. https://doi.org/10.1007/s10948-015-3045-2 wakano t, fujimura n, morinaga y, abe n, ashida a and ito t (2001), magnetic and magneto-transport properties of zno: ni films, physica e: low-dimensional systems and nanostructures. 10: 260-264. doi:10. 1016/s1386-9477(01)00095-9 wang xj, wang w and liu yl (2012), enhanced acetone sensing performance of au nanoparticles functionalized flower-like zno, sensors actuators b: chemical. 168: 39-45. https://doi.org/10.1016/j.snb.2012.01.006 yi xy, ma cy, yuan f, wang n, qin fw, hu bc and zhang qy (2017), structural, morphological, photoluminescence and photocatalytic properties of gd doped zno films, thin solid films. 636: 339-345. https://doi.org/10.1016/j.tsf.2017.05.020 doped zno nanocrystals also have an attractive optical responsiveness. many theoretical and experimental studies showed that re-doped zno could reportedly absorb ultraviolet (uv) light (chakraborty et al. 2017). obeid et al. (2019) prepared undoped and gd-doped zno nanocrystalline samples using the thermal decomposition method. they observed that the optical absorption spectra of pristine zno increased with a 6% gd doping concentration and the magnetic properties changed with changing dopant amounts. their pl spectroscopy results showed the existence of defects, which increased with increasing gd doping concentrations. they suggested that these dms nanoparticles can be used for magneto-optoelectronic practical device applications. undoubtedly, the re-doped zno nanostructures have been intensively studied recently because this is a rapidly growing field due to their multi-functionality and their use in possible new generation applications. with an aim to understand the effect of gd doping in zno in terms of its electronic and optical properties we have synthesize gd-doped zno powder series of different gd (0%, 2%, and 5%) values. various characterization techniques have been utilized to explore the electronic, structural and optical features of the synthesized powder series. gd doping into zno produced changes in the band gap and enhanced oxygen vacancies related states in the compound. materials and methods the gd-doped zno powder samples with varying gd (0%, 2%, and 5%) concentrations have been synthesized using the conventional solid-state reaction method. a suitable amount of high-purity (99.999% sigma-aldrich) zinc oxide (zno) and gadolinium oxide (gd2o3) powder have been used for their preparation. for achieving perfect homogeneity, the ingredients were properly pounded for ~8 hours in an agate mortar and pestle. the prepared material has been sintered for ~8h at~550°c and cooled at room temperature. again, the mixture was ground for ~2 hours and sintered for ~6 hours at ~550°c. the mixture was milled for ~4 hours before being turned into pellets. finally, these pellets were sintered for around ~8 hours at about ~600°c. finally, we ground the pellets to make the powder. the powder form of the prepared samples has been used for further characterization. characterization techniques the crystallographic structures of the samples have been explored using an x-ray diffractometer (make: panalytical x'pert pro) using the photon energy of cu kα (λ= 1.5406å). sem images have been used for the morphology study of the synthesized samples. the sem equipment model gora, kumar, choudhary, dolia, kumar and singhal 55 re elements, such as gd, may introduce additional capabilities to the zno system because they may be capable of constructing combined practical devices on a single chip by combining magnetic and optical properties (ohno et al. 1996; tawil et al. 2011). rare-earth (re) metal doping in the dilute magnetic semiconductor (dms) systems has recently received immense attention due to its potential usage in magneto electronic and photonic devices (monteiro et al. 2006). the influence of gd doping on the optical and electrical properties of zno is crucial for developing optoelectronic devices and understanding the genesis of ferromagnetism. ma and wang (2012) synthesized the gd-doped zno nanocrystals using the thermal evaporation deposition method. according to their findings, gd doping has an appreciable impact on the optical characteristics of the zno. the strong uv and blue emissions are detected at low gd concentrations because gd impurities introduce a mid-gap state into zno. in comparison, the uv and blue emissions reduce for high doping concentrations as a significant broad defect emission appears because of the vast numbers of defects, impurities, and excess gd2o3 produced. gd-doped zno nanocrystals can be used in optoelectronic devices. the optical and electrical tuning of the carrier density and optical band gap energy is essential for developing luminescent materials and equipment based on the zno dms systems. the optical band gap and carrier concentration are essential parameters to yield information about the emission wavelength. several development characteristics, like the synthesis methods, impurity concentration and substrate variety have been reported to influence these parameters (wakano et al. 2001; tan et al. 2011; murtaza et al. 2011). the synthesis of dms materials with unique optical, photocatalytic and magnetic characteristics seems to be the most promising candidate for the subsequent generation of electronic, optoelectronic and spintronic appliances (kumar and sahare 2014). the low-dimension materials with imperfection-free lattice structures have excellent electrical and magnetic characteristics; purposefully made or accidental structural defects play a significant role in altering their features (li et al. 2016; obeid et al. 2018). thus, the presence of different kinds of cation or anion vacancies and interstitials in zno nanocrystals may change their magnetic properties, photoluminescence, and photocatalytic properties (coey et al. 2005). although certain experimental and theoretical findings based on dft indicate that gd-doped zno exhibits the room temperature ferromagnetism (rtfm) (potzger et al. 2006; aravindh et al. 2014) property, several studies have demonstrated that the rtfm is not present (sambasivam et al. 2015). in addition to their magnetic qualities, the 4f ions eth 30 kv evo-18 carl zeiss, with a tilt of 0° to 60° and a rotation of 360°, has been used for taking sem images.the defect-related states and chemical analysis of the samples have been determined using x-ray photoelectron spectroscopy. a hemispherical analyzer with a 128-channel detector and a monochromated, fully integrated k-alpha small-spot x-ray photoelectron spectrometer system of 180° double focusing is used in xps (thermo scientific made). the uv-visible absorption spectroscopy (model: shimadzu uv-3600 uv-vis-nir spectrophotometer) was used to explore the prepared samples' optical absorption and band gap. the measurements of uv-visible absorption spectra have been taken using the powder form of the samples. pl spectroscopy was used to analyze defect-related states in the prepared samples. photoluminescence spectra have been recorded at room temperature using the fluorescence spectrometer (model: perkin elmer fl 8500). results and discussion xrd analysis fig. 1. depicts the powder xrd patterns of the gd-doped zno (gd = 0%, 2%, and 5%) samples. all the diffraction peaks detected in the zno sample match with the standard jcpds card number (36-1451). this confirms a hexagonal wurtzite crystal structure of the samples. the diffraction peaks were observed at 31.88°, 34.50°, 36.25°, 47.72°, 56.69°, 63.03°, 66.59°, 68.17°, and 69.35°, which are related to the planes (100), (002), (101), (102), (110), (103), (200), (112), and (201), respectively (ganesh et al. 2018; bharathi et al. 2020). further, some additional small peaks have been observed at 28.61°, 33.21°, and 39.14° with increasing gd doping. these secondary peaks representing a crystallite phase have been identified as gd2o3, which is well consistent with earlier reports (das et al. 2012). as shown in fig. 2, the highest intense peak related to the (101) plane shifted slightly higher angles with the increasing concentration of gd doping. the shift is because of the substitution of bigger-sized gd3+ (0.94 å) ions than zn2+ (0.74 å) ions in the hexagonal wurtzite structure. the peak shift may indicate that gd3+ ions have occupied the crystallographic positions of zn2+ ions in the zno host lattice, or itmay be because of the structural strain caused by the formation of internal compressive micro stress (dakhel and el-hilo 2010; kumar et al. 2014; sahu et al. 2017). rietveld refinements have been performed using the full prof programme (shown in fig. 3). the pseudo-voigt function has been used for rietveld refinement of all the samples with the space group p63mc. the estimated lattice parameters have been listed in table i. the lattice parameters are found to decrease with gd doping, similar to those reported in earlier studies (kaur et al. 2016; obeid et al. 2019). the factors like the induced deficiencies (vacancies, interstitial) and the ionic radius of zn and gd ions can be responsible for the observed change (kaur et al. 2016; kumar and thangavel 2017). sem analysis scanning electron micrographs have been used to analyze the morphology of the gd-doped zno powder samples. the sem images reveal a rod-like morphology in pure zno (gora et al. 2022) and the gd-doped zno polycrystalline samples with some proof of agglomeration and phase segregation, as depicted in fig. 4 (a, b and c). profound observation of the particles exhibits that the crystallite size is above 100 nm. the particles were intensive and incompatibly distributed all over the mass. a distinct boundary between neighbouring crystallites can be noticed, despite the proximity of these smaller crystallites. xps analysis the xps technique is an excellent tool for determining the surface chemistry and electron configuration of the various elements present in a multicomponent material. the carbon c1s peak (284.6 ev) has been used as a reference to calibrate all the binding energies of the spectra. the survey spectrum of the gd-doped zno samples is shown in fig. 5. the survey spectra revealed the existence of o, zn, and gd elements without any impurity in the samples. for zno and 2% gd-doped zno powder samples, the binding energies of the zn2p3/2 and zn2p1/2 peaks are found to be 1021.25 ev, 1044.25 ev, 1021.43 ev, and 1044.43 ev, respectively. however, for the 5% gd-doped zno sample, these peaks are at 1021.83 and 1044.83 ev energy positions. the small shift could be assigned to the creation of zn interstitials in zno upon gd doping. the binding energy gap between the zinc doublet peaks has been found at about 23 ev. this indicates that zn in the zno crystal structure is in the zn2+ oxidation state (khataee et al. 2015; gawai et al. 2019) as the spin-orbital splitting of zn2p is 23 ev. this difference does not change with the gd doping pointing out that gd doping has no discernible effect on the chemical position of zno. the o1s asymmetric xps spectraare shown in fig.7 (a) which is asymmetric in shape. the o1s xps spectra of all these samples i.e. the zno, the zn0.98gd0.02o, and the zn0.95gd0.05o have been deconvoluted mainly into two gaussian peaks, as shown in fig. 7 (b, c, and d). the lower binding peaks for pure and gd-doped zno (gd = 2% and 5%) polycrystalline samples have been detected at 529.93 ev, 529.93 ev and 529.78 ev, respectively, which attributed to the lattice oxygen in the hexagonal structure of the zno. the higher binding peak for the pure and the gd-doped zno samples have been found at 531.51 ev, 531.66 ev, and 531.49 ev, respectively, which is due to the presence of oxygen vacancies in the zno structure (bharathi et al. 2020; sukumaran et al. 2021). an additional signal centered at 528.29 ev has been detected in the 5% gd-doped zno powder sample, which could be ascribed to the coordination of oxygen in gd-o-zn along grain boundaries because of the excessive gd dopants and also attributed to the presence of gd2o3 in the sample (yi et al. 2017). the lattice oxygen peak has slightly shifted to the lower binding energy with increasing gd concentration, which has been due to the increased oxygen vacancies with increasing gd doping. the estimated area ratios of the oxygen vacancies peak and the lattice oxygen peak for the samples zno, zn0.98gd0.02o, and zn0.95gd0.05o comes out to be 0.53, 1.30, and 2.49, respectively. these results show that the oxygen vacancies increase with increasing gd concentration. the fig. 8 (a, b) depicts the high-resolution gd4d xps spectra of the gd-doped samples.in the gd4d state, the spin-orbit splatted peaks are at 144.6 ev for gd4d3/2 and 139.6 ev for gd4d5/2 for the 2% gd-doped sample, whereas for the 5% gd-doped zno sample, the spin-orbit splits at 145.5 ev for gd4d3/2 and 139.7 ev for gd4d5/2 as shown in fig. 8 (a, b). this indicates that gd is present in the gd3+ state in the zno hexagonal structure. the shift in peak values of gd4d3/2 and gd4d5/2 from 144.6 ev and 139.6 ev, respectively; in the case of 2% gd-doped sample to 145.5 ev and 139.7 ev, respectively, in the case of 5% gd-doped sample. this shift in gd4d peaks is ascribed to the electron transfer from plasmonics gd to zno because of the strong electronic interaction (covalent bond) between gd and the oxide (ahmad et al. 2011; wang et al. 2012; bharathi et al. 2020). uv visible spectroscopy analysis the uv–visible spectroscopy is a powerful tool for estimating band gap of materials. uv–vis absorbance spectra and tauc plots for the gd-doped zno samples (gd = 0% (gora et al. 2022), 2%, and 5%) samples are shown in figs.9 (a, b, c, and d). the spectra show a red shift with increasing gd amount in the zno.the uv–vis absorption intensity of the synthesized polycrystalline samples is found to reduce with the increasing gd concentration (mazhdi and tafreshi 2018). tauc's plot has been used to calculate the direct band gap of the samples (jain et al. 2006). the direct band gap has been estimated using the following equation: here, α is the absorption coefficient,υ is frequency, h is the planck constant, a is a constant, and eg is the energy band gap of the substance. extrapolating the linear component of the curve plotted among (αhυ) 2 and hυ depicted in fig. 9 (b, c, and d) has been used to obtain the band gap (farhad et al. 2018; ghos et al. 2021). the band gap values calculated for the gd-doped zno samples, i.e.are 3.31 ev (gora et al. 2022), 3.27 ev, and 3.23ev, for the samples gd = 0%, 2% and 5%, respectively. the small redshift observed in the band gap of gd-doped zno samples is because of the changes in electronic structure as well as enhanced oxygen vacancies with the increasing gd doping (yi et al. 2017; flemban et al. 2016), which is responsible for the band gap reduction. photoluminescence spectroscopy analysis the structural flaws like ionic and atomic vacancies, replacements and interstitials have been explored using the pl spectra of the synthesized polycrystalline samples. fig. 10 (a, b and c) shows the deconvoluted, gaussian-fitted pl spectra of the synthesized gd-doped zno polycrystalline powder samples. the pl spectra of the samples were recorded at room temperature in order to determine the types of vacancies, defect band emission etc. (lin et al. 2001; yi et al. 2017). the photoluminescence spectra have been deconvoluted and the different peaks responsible for the emission have been gaussian fitted. for these samples the band edge emission peaksare detected at 381 nm, 384 nm, and 383 nm, for the gd = 0%, 2% and 5% samples, respectively. the uv emission is responsible for the excitonic interaction related to the band edge emission. the intense violet emission exhibited in the gd-doped zno at about 415 nm could be because ofthe oxygen vacancies. the exciton interaction between the holes in the valence band and electrons located in the interstitial zinc could be responsible for the violet emission peak at about 447 nm. intrinsic deficiencies like interstitial zinc and oxygen can be attributed to the peak at 477 nm (singh et al. 2009; kaur et al. 2016). the transformation between singly ionized oxygen deficiency and the photo-created holes (kennedy et al. 2014) or the surface imperfection and electrons near the conduction band, might be responsible for the green emission peak seen for the gd-doped znoat around 525 nm. the green emissions are commonly attributed to theoxygen vacancies (studenikin et al. 1998). for gd-doped zno polycrystalline powder samples, the intensity ratio of the green and ultra-violet emission peaks is found to be 0.090 for zno, 0.204 for the 2% gd-doped zno, and 0.418 for the 5% gd-doped zno. the defect-related emissions enhanced with increasing gd doping in the zno indicate that a large number of deficiencies, such as oxygen vacancies, are most usually related to crystal deformation (yi et al. 2017). the results reveal that the gd doping enhances the zni and vo flaws. it could be attributed to structural deformation created by gd atoms with different ionic sizes than zn in the zno (bandopadhyay and mitra 2015; sukumaran et al. 2021). increasing gd doping in zno indicates an increase in defect states, which matches well with the xps results. we compared our pl results with farhad et al. (2019), who prepared zno dc (drop casting) and zno nanorods. their pl results detected the pl peak at 380 nm and a barely observable green-yellow emission peak; in our case, we find it at 381 nm for zno, 384 nm for 2% gd-doped zno and 383 nm for the 5% gd-doped zno polycrystalline sample. this peak represented zno's near band edge (nbe) transition because of free excitons recombinations and this pl property indicates high crystalline quality. the luminescent characteristics in the visible region are responsible for the different defects, like zinc interstitials (zni), oxygen vacancies (vo), etc., present in the zno crystal matrix. as a result, they reported that both zno (dc) and zno nanorods were found to be defect-free good crystalline and optical properties materials. in our case, all the prepared gd-doped zno powder samples have been found to be with single ionized oxygen vacancies, which are confirmed by the green emission peak at 525 nm in the pl spectra. conclusion the gd-doped zno powder samples were synthesized by the solid-state reaction method. the xrd patterns affirm that gd has been successfully incorporated into the zno lattice and confirm the hexagonal wurtzite structure. sem images have been used to reveal the morphologies of the synthesized samples, which appear as rod-like structures. the xps results showed that the oxygen vacancy-related states in gd-doped samples increased with increasing gd doping. pl findings confirmed that the defect-related states are present in the gd-doped zno polycrystalline samples. the green emission and ultra-violet emission peaks' intensity ratio is 0.418 for the 5% gd-doped zno sample, which is the maximum compared to the pure zno and 2% gd-doped zno polycrystalline powder sample. these findings confirmed that the oxygen vacancies increase as the gd concentration increases and the pl results agree well with the xps results. the uv absorption spectra findings reveal that the band gap in the 5% gd-doped zno sample is found to be 3.23 ev, which is the minimum compared to both the pure zno and the 2% gd-doped zno samples, confirming that eg is reduced with increasing gd concentration. acknowledgment the authors are thankful to usic, university of rajasthan, jaipur, rajasthan (india), for providing sem images of the prepared samples. we also thank department of physics, banasthalividhyapith, banasthali, jaipur, rajasthan (india) for rendering xrd data. funding sources this research is not financed by any agency. authors' contribution sample preparation, data analysis, manuscript composition and writing (mahendra kumar gora); 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nanocrystals also have an attractive optical responsiveness. many theoretical and experimental studies showed that re-doped zno could reportedly absorb ultraviolet (uv) light (chakraborty et al. 2017). obeid et al. (2019) prepared undoped and gd-doped zno nanocrystalline samples using the thermal decomposition method. they observed that the optical absorption spectra of pristine zno increased with a 6% gd doping concentration and the magnetic properties changed with changing dopant amounts. their pl spectroscopy results showed the existence of defects, which increased with increasing gd doping concentrations. they suggested that these dms nanoparticles can be used for magneto-optoelectronic practical device applications. undoubtedly, the re-doped zno nanostructures have been intensively studied recently because this is a rapidly growing field due to their multi-functionality and their use in possible new generation applications. with an aim to understand the effect of gd doping in zno in terms of its electronic and optical properties we have synthesize gd-doped zno powder series of different gd (0%, 2%, and 5%) values. various characterization techniques have been utilized to explore the electronic, structural and optical features of the synthesized powder series. gd doping into zno produced changes in the band gap and enhanced oxygen vacancies related states in the compound. materials and methods the gd-doped zno powder samples with varying gd (0%, 2%, and 5%) concentrations have been synthesized using the conventional solid-state reaction method. a suitable amount of high-purity (99.999% sigma-aldrich) zinc oxide (zno) and gadolinium oxide (gd2o3) powder have been used for their preparation. for achieving perfect homogeneity, the ingredients were properly pounded for ~8 hours in an agate mortar and pestle. the prepared material has been sintered for ~8h at~550°c and cooled at room temperature. again, the mixture was ground for ~2 hours and sintered for ~6 hours at ~550°c. the mixture was milled for ~4 hours before being turned into pellets. finally, these pellets were sintered for around ~8 hours at about ~600°c. finally, we ground the pellets to make the powder. the powder form of the prepared samples has been used for further characterization. characterization techniques the crystallographic structures of the samples have been explored using an x-ray diffractometer (make: panalytical x'pert pro) using the photon energy of cu kα (λ= 1.5406å). sem images have been used for the morphology study of the synthesized samples. the sem equipment model fig. 1. xrd patterns for the pure zno powder (gora et al. 2022) and (2% and 5%) gd-doped zno powder samples fig. 2. extended xrd patterns for the (101) peak of undoped zno powder (gora et al. 2022) and gd-doped zno (gd = 2% and 5%) powder samples electronic, structural and optical properties of gd-doped zno powder 58(1) 202356 re elements, such as gd, may introduce additional capabilities to the zno system because they may be capable of constructing combined practical devices on a single chip by combining magnetic and optical properties (ohno et al. 1996; tawil et al. 2011). rare-earth (re) metal doping in the dilute magnetic semiconductor (dms) systems has recently received immense attention due to its potential usage in magneto electronic and photonic devices (monteiro et al. 2006). the influence of gd doping on the optical and electrical properties of zno is crucial for developing optoelectronic devices and understanding the genesis of ferromagnetism. ma and wang (2012) synthesized the gd-doped zno nanocrystals using the thermal evaporation deposition method. according to their findings, gd doping has an appreciable impact on the optical characteristics of the zno. the strong uv and blue emissions are detected at low gd concentrations because gd impurities introduce a mid-gap state into zno. in comparison, the uv and blue emissions reduce for high doping concentrations as a significant broad defect emission appears because of the vast numbers of defects, impurities, and excess gd2o3 produced. gd-doped zno nanocrystals can be used in optoelectronic devices. the optical and electrical tuning of the carrier density and optical band gap energy is essential for developing luminescent materials and equipment based on the zno dms systems. the optical band gap and carrier concentration are essential parameters to yield information about the emission wavelength. several development characteristics, like the synthesis methods, impurity concentration and substrate variety have been reported to influence these parameters (wakano et al. 2001; tan et al. 2011; murtaza et al. 2011). the synthesis of dms materials with unique optical, photocatalytic and magnetic characteristics seems to be the most promising candidate for the subsequent generation of electronic, optoelectronic and spintronic appliances (kumar and sahare 2014). the low-dimension materials with imperfection-free lattice structures have excellent electrical and magnetic characteristics; purposefully made or accidental structural defects play a significant role in altering their features (li et al. 2016; obeid et al. 2018). thus, the presence of different kinds of cation or anion vacancies and interstitials in zno nanocrystals may change their magnetic properties, photoluminescence, and photocatalytic properties (coey et al. 2005). although certain experimental and theoretical findings based on dft indicate that gd-doped zno exhibits the room temperature ferromagnetism (rtfm) (potzger et al. 2006; aravindh et al. 2014) property, several studies have demonstrated that the rtfm is not present (sambasivam et al. 2015). in addition to their magnetic qualities, the 4f ions eth 30 kv evo-18 carl zeiss, with a tilt of 0° to 60° and a rotation of 360°, has been used for taking sem images.the defect-related states and chemical analysis of the samples have been determined using x-ray photoelectron spectroscopy. a hemispherical analyzer with a 128-channel detector and a monochromated, fully integrated k-alpha small-spot x-ray photoelectron spectrometer system of 180° double focusing is used in xps (thermo scientific made). the uv-visible absorption spectroscopy (model: shimadzu uv-3600 uv-vis-nir spectrophotometer) was used to explore the prepared samples' optical absorption and band gap. the measurements of uv-visible absorption spectra have been taken using the powder form of the samples. pl spectroscopy was used to analyze defect-related states in the prepared samples. photoluminescence spectra have been recorded at room temperature using the fluorescence spectrometer (model: perkin elmer fl 8500). results and discussion xrd analysis fig. 1. depicts the powder xrd patterns of the gd-doped zno (gd = 0%, 2%, and 5%) samples. all the diffraction peaks detected in the zno sample match with the standard jcpds card number (36-1451). this confirms a hexagonal wurtzite crystal structure of the samples. the diffraction peaks were observed at 31.88°, 34.50°, 36.25°, 47.72°, 56.69°, 63.03°, 66.59°, 68.17°, and 69.35°, which are related to the planes (100), (002), (101), (102), (110), (103), (200), (112), and (201), respectively (ganesh et al. 2018; bharathi et al. 2020). further, some additional small peaks have been observed at 28.61°, 33.21°, and 39.14° with increasing gd doping. these secondary peaks representing a crystallite phase have been identified as gd2o3, which is well consistent with earlier reports (das et al. 2012). as shown in fig. 2, the highest intense peak related to the (101) plane shifted slightly higher angles with the increasing concentration of gd doping. the shift is because of the substitution of bigger-sized gd3+ (0.94 å) ions than zn2+ (0.74 å) ions in the hexagonal wurtzite structure. the peak shift may indicate that gd3+ ions have occupied the crystallographic positions of zn2+ ions in the zno host lattice, or itmay be because of the structural strain caused by the formation of internal compressive micro stress (dakhel and el-hilo 2010; kumar et al. 2014; sahu et al. 2017). rietveld refinements have been performed using the full prof programme (shown in fig. 3). the pseudo-voigt function has been used for rietveld refinement of all the samples with the space group p63mc. the estimated lattice parameters have been listed in table i. the lattice parameters are found to decrease with gd doping, similar to those reported in earlier studies (kaur et al. 2016; obeid et al. 2019). the factors like the induced deficiencies (vacancies, interstitial) and the ionic radius of zn and gd ions can be responsible for the observed change (kaur et al. 2016; kumar and thangavel 2017). sem analysis scanning electron micrographs have been used to analyze the morphology of the gd-doped zno powder samples. the sem images reveal a rod-like morphology in pure zno (gora et al. 2022) and the gd-doped zno polycrystalline samples with some proof of agglomeration and phase segregation, as depicted in fig. 4 (a, b and c). profound observation of the particles exhibits that the crystallite size is above 100 nm. the particles were intensive and incompatibly distributed all over the mass. a distinct boundary between neighbouring crystallites can be noticed, despite the proximity of these smaller crystallites. xps analysis the xps technique is an excellent tool for determining the surface chemistry and electron configuration of the various elements present in a multicomponent material. the carbon c1s peak (284.6 ev) has been used as a reference to calibrate all the binding energies of the spectra. the survey spectrum of the gd-doped zno samples is shown in fig. 5. the survey spectra revealed the existence of o, zn, and gd elements without any impurity in the samples. for zno and 2% gd-doped zno powder samples, the binding energies of the zn2p3/2 and zn2p1/2 peaks are found to be 1021.25 ev, 1044.25 ev, 1021.43 ev, and 1044.43 ev, respectively. however, for the 5% gd-doped zno sample, these peaks are at 1021.83 and 1044.83 ev energy positions. the small shift could be assigned to the creation of zn interstitials in zno upon gd doping. the binding energy gap between the zinc doublet peaks has been found at about 23 ev. this indicates that zn in the zno crystal structure is in the zn2+ oxidation state (khataee et al. 2015; gawai et al. 2019) as the spin-orbital splitting of zn2p is 23 ev. this difference does not change with the gd doping pointing out that gd doping has no discernible effect on the chemical position of zno. the o1s asymmetric xps spectraare shown in fig.7 (a) which is asymmetric in shape. the o1s xps spectra of all these samples i.e. the zno, the zn0.98gd0.02o, and the zn0.95gd0.05o have been deconvoluted mainly into two gaussian peaks, as shown in fig. 7 (b, c, and d). the lower binding peaks for pure and gd-doped zno (gd = 2% and 5%) polycrystalline samples have been detected at 529.93 ev, 529.93 ev and 529.78 ev, respectively, which attributed to the lattice oxygen in the hexagonal structure of the zno. the higher binding peak for the pure and the gd-doped zno samples have been found at 531.51 ev, 531.66 ev, and 531.49 ev, respectively, which is due to the presence of oxygen vacancies in the zno structure (bharathi et al. 2020; sukumaran et al. 2021). an additional signal centered at 528.29 ev has been detected in the 5% gd-doped zno powder sample, which could be ascribed to the coordination of oxygen in gd-o-zn along grain boundaries because of the excessive gd dopants and also attributed to the presence of gd2o3 in the sample (yi et al. 2017). the lattice oxygen peak has slightly shifted to the lower binding energy with increasing gd concentration, which has been due to the increased oxygen vacancies with increasing gd doping. the estimated area ratios of the oxygen vacancies peak and the lattice oxygen peak for the samples zno, zn0.98gd0.02o, and zn0.95gd0.05o comes out to be 0.53, 1.30, and 2.49, respectively. these results show that the oxygen vacancies increase with increasing gd concentration. the fig. 8 (a, b) depicts the high-resolution gd4d xps spectra of the gd-doped samples.in the gd4d state, the spin-orbit splatted peaks are at 144.6 ev for gd4d3/2 and 139.6 ev for gd4d5/2 for the 2% gd-doped sample, whereas for the 5% gd-doped zno sample, the spin-orbit splits at 145.5 ev for gd4d3/2 and 139.7 ev for gd4d5/2 as shown in fig. 8 (a, b). this indicates that gd is present in the gd3+ state in the zno hexagonal structure. the shift in peak values of gd4d3/2 and gd4d5/2 from 144.6 ev and 139.6 ev, respectively; in the case of 2% gd-doped sample to 145.5 ev and 139.7 ev, respectively, in the case of 5% gd-doped sample. this shift in gd4d peaks is ascribed to the electron transfer from plasmonics gd to zno because of the strong electronic interaction (covalent bond) between gd and the oxide (ahmad et al. 2011; wang et al. 2012; bharathi et al. 2020). uv visible spectroscopy analysis the uv–visible spectroscopy is a powerful tool for estimating band gap of materials. uv–vis absorbance spectra and tauc plots for the gd-doped zno samples (gd = 0% (gora et al. 2022), 2%, and 5%) samples are shown in figs.9 (a, b, c, and d). the spectra show a red shift with increasing gd amount in the zno.the uv–vis absorption intensity of the synthesized polycrystalline samples is found to reduce with the increasing gd concentration (mazhdi and tafreshi 2018). tauc's plot has been used to calculate the direct band gap of the samples (jain et al. 2006). the direct band gap has been estimated using the following equation: here, α is the absorption coefficient,υ is frequency, h is the planck constant, a is a constant, and eg is the energy band gap of the substance. extrapolating the linear component of the curve plotted among (αhυ) 2 and hυ depicted in fig. 9 (b, c, and d) has been used to obtain the band gap (farhad et al. 2018; ghos et al. 2021). the band gap values calculated for the gd-doped zno samples, i.e.are 3.31 ev (gora et al. 2022), 3.27 ev, and 3.23ev, for the samples gd = 0%, 2% and 5%, respectively. the small redshift observed in the band gap of gd-doped zno samples is because of the changes in electronic structure as well as enhanced oxygen vacancies with the increasing gd doping (yi et al. 2017; flemban et al. 2016), which is responsible for the band gap reduction. photoluminescence spectroscopy analysis the structural flaws like ionic and atomic vacancies, replacements and interstitials have been explored using the pl spectra of the synthesized polycrystalline samples. fig. 10 (a, b and c) shows the deconvoluted, gaussian-fitted pl spectra of the synthesized gd-doped zno polycrystalline powder samples. the pl spectra of the samples were recorded at room temperature in order to determine the types of vacancies, defect band emission etc. (lin et al. 2001; yi et al. 2017). the photoluminescence spectra have been deconvoluted and the different peaks responsible for the emission have been gaussian fitted. for these samples the band edge emission peaksare detected at 381 nm, 384 nm, and 383 nm, for the gd = 0%, 2% and 5% samples, respectively. the uv emission is responsible for the excitonic interaction related to the band edge emission. the intense violet emission exhibited in the gd-doped zno at about 415 nm could be because ofthe oxygen vacancies. the exciton interaction between the holes in the valence band and electrons located in the interstitial zinc could be responsible for the violet emission peak at about 447 nm. intrinsic deficiencies like interstitial zinc and oxygen can be attributed to the peak at 477 nm (singh et al. 2009; kaur et al. 2016). the transformation between singly ionized oxygen deficiency and the photo-created holes (kennedy et al. 2014) or the surface imperfection and electrons near the conduction band, might be responsible for the green emission peak seen for the gd-doped znoat around 525 nm. the green emissions are commonly attributed to theoxygen vacancies (studenikin et al. 1998). for gd-doped zno polycrystalline powder samples, the intensity ratio of the green and ultra-violet emission peaks is found to be 0.090 for zno, 0.204 for the 2% gd-doped zno, and 0.418 for the 5% gd-doped zno. the defect-related emissions enhanced with increasing gd doping in the zno indicate that a large number of deficiencies, such as oxygen vacancies, are most usually related to crystal deformation (yi et al. 2017). the results reveal that the gd doping enhances the zni and vo flaws. it could be attributed to structural deformation created by gd atoms with different ionic sizes than zn in the zno (bandopadhyay and mitra 2015; sukumaran et al. 2021). increasing gd doping in zno indicates an increase in defect states, which matches well with the xps results. we compared our pl results with farhad et al. (2019), who prepared zno dc (drop casting) and zno nanorods. their pl results detected the pl peak at 380 nm and a barely observable green-yellow emission peak; in our case, we find it at 381 nm for zno, 384 nm for 2% gd-doped zno and 383 nm for the 5% gd-doped zno polycrystalline sample. this peak represented zno's near band edge (nbe) transition because of free excitons recombinations and this pl property indicates high crystalline quality. the luminescent characteristics in the visible region are responsible for the different defects, like zinc interstitials (zni), oxygen vacancies (vo), etc., present in the zno crystal matrix. as a result, they reported that both zno (dc) and zno nanorods were found to be defect-free good crystalline and optical properties materials. in our case, all the prepared gd-doped zno powder samples have been found to be with single ionized oxygen vacancies, which are confirmed by the green emission peak at 525 nm in the pl spectra. conclusion the gd-doped zno powder samples were synthesized by the solid-state reaction method. the xrd patterns affirm that gd has been successfully incorporated into the zno lattice and confirm the hexagonal wurtzite structure. sem images have been used to reveal the morphologies of the synthesized samples, which appear as rod-like structures. the xps results showed that the oxygen vacancy-related states in gd-doped samples increased with increasing gd doping. pl findings confirmed that the defect-related states are present in the gd-doped zno polycrystalline samples. the green emission and ultra-violet emission peaks' intensity ratio is 0.418 for the 5% gd-doped zno sample, which is the maximum compared to the pure zno and 2% gd-doped zno polycrystalline powder sample. these findings confirmed that the oxygen vacancies increase as the gd concentration increases and the pl results agree well with the xps results. the uv absorption spectra findings reveal that the band gap in the 5% gd-doped zno sample is found to be 3.23 ev, which is the minimum compared to both the pure zno and the 2% gd-doped zno samples, confirming that eg is reduced with increasing gd concentration. acknowledgment the authors are thankful to usic, university of rajasthan, jaipur, rajasthan (india), for providing sem images of the prepared samples. we also thank department of physics, banasthalividhyapith, banasthali, jaipur, rajasthan (india) for rendering xrd data. funding sources this research is not financed by any agency. authors' contribution sample preparation, data analysis, manuscript composition and writing (mahendra kumar gora); 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vc (2009), synthesis, effect of capping agents, structural, optical and photoluminescence properties of zno nanoparticles, j. lumin. 129: 874-878. https://doi.org/ 10.1016/j.jlumin.2009.03.027 studenikin sa, golego n and cocivera m (1998), fabrication of green and photoluminescent, undoped zno films using spray pyrolysis, j. appl. phys. 84: 2287-2294. https://doi.org/10.1063/1.368295 sukumaran a, sivanantham n, vinoth e and gopalakrishnan n (2021), ferromagnetism in gd-doped zno thin films mediated by defects, bull. mater. sci. 44: 259. http://dx.doi.org/ 10.1007/s12034-021-02550-y tan y, fang z, chen w and he p (2011),structural, optical and magnetic properties of eu-doped zno films,j. alloys compd. 509: 6321-6324. https://doi.org/ 10.1016/j.jallcom.2011.03.084 tawil snm, krishnamurthy d, kakimi r, emura s, hasegawa s and ashi h (2011), studies on the ingagdn/gan magnetic semiconductor heterostructures grown by plasma-assisted molecular-beam epitaxy, journal of crystal growth. 323: 351-354. https://doi.org/10. 1016/j.jcrysgro.2010.11.166 thangeeswari t, murugasen p and velmurugan j (2015), influence of co and dy doping on the optical and magnetic properties of zno nanoparticles for dms application, j. supercond. nov. magn. 28: 2505-2515. https://doi.org/10.1007/s10948-015-3045-2 wakano t, fujimura n, morinaga y, abe n, ashida a and ito t (2001), magnetic and magneto-transport properties of zno: ni films, physica e: low-dimensional systems and nanostructures. 10: 260-264. doi:10. 1016/s1386-9477(01)00095-9 wang xj, wang w and liu yl (2012), enhanced acetone sensing performance of au nanoparticles functionalized flower-like zno, sensors actuators b: chemical. 168: 39-45. https://doi.org/10.1016/j.snb.2012.01.006 yi xy, ma cy, yuan f, wang n, qin fw, hu bc and zhang qy (2017), structural, morphological, photoluminescence and photocatalytic properties of gd doped zno films, thin solid films. 636: 339-345. https://doi.org/10.1016/j.tsf.2017.05.020 doped zno nanocrystals also have an attractive optical responsiveness. many theoretical and experimental studies showed that re-doped zno could reportedly absorb ultraviolet (uv) light (chakraborty et al. 2017). obeid et al. (2019) prepared undoped and gd-doped zno nanocrystalline samples using the thermal decomposition method. they observed that the optical absorption spectra of pristine zno increased with a 6% gd doping concentration and the magnetic properties changed with changing dopant amounts. their pl spectroscopy results showed the existence of defects, which increased with increasing gd doping concentrations. they suggested that these dms nanoparticles can be used for magneto-optoelectronic practical device applications. undoubtedly, the re-doped zno nanostructures have been intensively studied recently because this is a rapidly growing field due to their multi-functionality and their use in possible new generation applications. with an aim to understand the effect of gd doping in zno in terms of its electronic and optical properties we have synthesize gd-doped zno powder series of different gd (0%, 2%, and 5%) values. various characterization techniques have been utilized to explore the electronic, structural and optical features of the synthesized powder series. gd doping into zno produced changes in the band gap and enhanced oxygen vacancies related states in the compound. materials and methods the gd-doped zno powder samples with varying gd (0%, 2%, and 5%) concentrations have been synthesized using the conventional solid-state reaction method. a suitable amount of high-purity (99.999% sigma-aldrich) zinc oxide (zno) and gadolinium oxide (gd2o3) powder have been used for their preparation. for achieving perfect homogeneity, the ingredients were properly pounded for ~8 hours in an agate mortar and pestle. the prepared material has been sintered for ~8h at~550°c and cooled at room temperature. again, the mixture was ground for ~2 hours and sintered for ~6 hours at ~550°c. the mixture was milled for ~4 hours before being turned into pellets. finally, these pellets were sintered for around ~8 hours at about ~600°c. finally, we ground the pellets to make the powder. the powder form of the prepared samples has been used for further characterization. characterization techniques the crystallographic structures of the samples have been explored using an x-ray diffractometer (make: panalytical x'pert pro) using the photon energy of cu kα (λ= 1.5406å). sem images have been used for the morphology study of the synthesized samples. the sem equipment model sample lattice parameter å c/a a c zno 3.2505 5.2077 1.6 2% gd@zno 3.2498 5.2059 1.6 5% gd@zno 3.2490 5.2047 1.6 table i. lattice parameters and c/a ratio of the gd-doped zno polycrystalline powder samples fig. 3. rietveld refined xrd patterns for polycrystalline powder samples of (a) the pure zno (gora et al. 2022), (b) the 2% gd-doped zno and (c) the 5% gd-doped zno. observed data is shown by red dots and black solid line is the fitted profile. bragg peak positions are marked by vertical green lines. the lower plot in blue is the residual curve gora, kumar, choudhary, dolia, kumar and singhal 57 re elements, such as gd, may introduce additional capabilities to the zno system because they may be capable of constructing combined practical devices on a single chip by combining magnetic and optical properties (ohno et al. 1996; tawil et al. 2011). rare-earth (re) metal doping in the dilute magnetic semiconductor (dms) systems has recently received immense attention due to its potential usage in magneto electronic and photonic devices (monteiro et al. 2006). the influence of gd doping on the optical and electrical properties of zno is crucial for developing optoelectronic devices and understanding the genesis of ferromagnetism. ma and wang (2012) synthesized the gd-doped zno nanocrystals using the thermal evaporation deposition method. according to their findings, gd doping has an appreciable impact on the optical characteristics of the zno. the strong uv and blue emissions are detected at low gd concentrations because gd impurities introduce a mid-gap state into zno. in comparison, the uv and blue emissions reduce for high doping concentrations as a significant broad defect emission appears because of the vast numbers of defects, impurities, and excess gd2o3 produced. gd-doped zno nanocrystals can be used in optoelectronic devices. the optical and electrical tuning of the carrier density and optical band gap energy is essential for developing luminescent materials and equipment based on the zno dms systems. the optical band gap and carrier concentration are essential parameters to yield information about the emission wavelength. several development characteristics, like the synthesis methods, impurity concentration and substrate variety have been reported to influence these parameters (wakano et al. 2001; tan et al. 2011; murtaza et al. 2011). the synthesis of dms materials with unique optical, photocatalytic and magnetic characteristics seems to be the most promising candidate for the subsequent generation of electronic, optoelectronic and spintronic appliances (kumar and sahare 2014). the low-dimension materials with imperfection-free lattice structures have excellent electrical and magnetic characteristics; purposefully made or accidental structural defects play a significant role in altering their features (li et al. 2016; obeid et al. 2018). thus, the presence of different kinds of cation or anion vacancies and interstitials in zno nanocrystals may change their magnetic properties, photoluminescence, and photocatalytic properties (coey et al. 2005). although certain experimental and theoretical findings based on dft indicate that gd-doped zno exhibits the room temperature ferromagnetism (rtfm) (potzger et al. 2006; aravindh et al. 2014) property, several studies have demonstrated that the rtfm is not present (sambasivam et al. 2015). in addition to their magnetic qualities, the 4f ions eth 30 kv evo-18 carl zeiss, with a tilt of 0° to 60° and a rotation of 360°, has been used for taking sem images.the defect-related states and chemical analysis of the samples have been determined using x-ray photoelectron spectroscopy. a hemispherical analyzer with a 128-channel detector and a monochromated, fully integrated k-alpha small-spot x-ray photoelectron spectrometer system of 180° double focusing is used in xps (thermo scientific made). the uv-visible absorption spectroscopy (model: shimadzu uv-3600 uv-vis-nir spectrophotometer) was used to explore the prepared samples' optical absorption and band gap. the measurements of uv-visible absorption spectra have been taken using the powder form of the samples. pl spectroscopy was used to analyze defect-related states in the prepared samples. photoluminescence spectra have been recorded at room temperature using the fluorescence spectrometer (model: perkin elmer fl 8500). results and discussion xrd analysis fig. 1. depicts the powder xrd patterns of the gd-doped zno (gd = 0%, 2%, and 5%) samples. all the diffraction peaks detected in the zno sample match with the standard jcpds card number (36-1451). this confirms a hexagonal wurtzite crystal structure of the samples. the diffraction peaks were observed at 31.88°, 34.50°, 36.25°, 47.72°, 56.69°, 63.03°, 66.59°, 68.17°, and 69.35°, which are related to the planes (100), (002), (101), (102), (110), (103), (200), (112), and (201), respectively (ganesh et al. 2018; bharathi et al. 2020). further, some additional small peaks have been observed at 28.61°, 33.21°, and 39.14° with increasing gd doping. these secondary peaks representing a crystallite phase have been identified as gd2o3, which is well consistent with earlier reports (das et al. 2012). as shown in fig. 2, the highest intense peak related to the (101) plane shifted slightly higher angles with the increasing concentration of gd doping. the shift is because of the substitution of bigger-sized gd3+ (0.94 å) ions than zn2+ (0.74 å) ions in the hexagonal wurtzite structure. the peak shift may indicate that gd3+ ions have occupied the crystallographic positions of zn2+ ions in the zno host lattice, or itmay be because of the structural strain caused by the formation of internal compressive micro stress (dakhel and el-hilo 2010; kumar et al. 2014; sahu et al. 2017). rietveld refinements have been performed using the full prof programme (shown in fig. 3). the pseudo-voigt function has been used for rietveld refinement of all the samples with the space group p63mc. the estimated lattice parameters have been listed in table i. the lattice parameters are found to decrease with gd doping, similar to those reported in earlier studies (kaur et al. 2016; obeid et al. 2019). the factors like the induced deficiencies (vacancies, interstitial) and the ionic radius of zn and gd ions can be responsible for the observed change (kaur et al. 2016; kumar and thangavel 2017). sem analysis scanning electron micrographs have been used to analyze the morphology of the gd-doped zno powder samples. the sem images reveal a rod-like morphology in pure zno (gora et al. 2022) and the gd-doped zno polycrystalline samples with some proof of agglomeration and phase segregation, as depicted in fig. 4 (a, b and c). profound observation of the particles exhibits that the crystallite size is above 100 nm. the particles were intensive and incompatibly distributed all over the mass. a distinct boundary between neighbouring crystallites can be noticed, despite the proximity of these smaller crystallites. xps analysis the xps technique is an excellent tool for determining the surface chemistry and electron configuration of the various elements present in a multicomponent material. the carbon c1s peak (284.6 ev) has been used as a reference to calibrate all the binding energies of the spectra. the survey spectrum of the gd-doped zno samples is shown in fig. 5. the survey spectra revealed the existence of o, zn, and gd elements without any impurity in the samples. for zno and 2% gd-doped zno powder samples, the binding energies of the zn2p3/2 and zn2p1/2 peaks are found to be 1021.25 ev, 1044.25 ev, 1021.43 ev, and 1044.43 ev, respectively. however, for the 5% gd-doped zno sample, these peaks are at 1021.83 and 1044.83 ev energy positions. the small shift could be assigned to the creation of zn interstitials in zno upon gd doping. the binding energy gap between the zinc doublet peaks has been found at about 23 ev. this indicates that zn in the zno crystal structure is in the zn2+ oxidation state (khataee et al. 2015; gawai et al. 2019) as the spin-orbital splitting of zn2p is 23 ev. this difference does not change with the gd doping pointing out that gd doping has no discernible effect on the chemical position of zno. the o1s asymmetric xps spectraare shown in fig.7 (a) which is asymmetric in shape. the o1s xps spectra of all these samples i.e. the zno, the zn0.98gd0.02o, and the zn0.95gd0.05o have been deconvoluted mainly into two gaussian peaks, as shown in fig. 7 (b, c, and d). the lower binding peaks for pure and gd-doped zno (gd = 2% and 5%) polycrystalline samples have been detected at 529.93 ev, 529.93 ev and 529.78 ev, respectively, which attributed to the lattice oxygen in the hexagonal structure of the zno. the higher binding peak for the pure and the gd-doped zno samples have been found at 531.51 ev, 531.66 ev, and 531.49 ev, respectively, which is due to the presence of oxygen vacancies in the zno structure (bharathi et al. 2020; sukumaran et al. 2021). an additional signal centered at 528.29 ev has been detected in the 5% gd-doped zno powder sample, which could be ascribed to the coordination of oxygen in gd-o-zn along grain boundaries because of the excessive gd dopants and also attributed to the presence of gd2o3 in the sample (yi et al. 2017). the lattice oxygen peak has slightly shifted to the lower binding energy with increasing gd concentration, which has been due to the increased oxygen vacancies with increasing gd doping. the estimated area ratios of the oxygen vacancies peak and the lattice oxygen peak for the samples zno, zn0.98gd0.02o, and zn0.95gd0.05o comes out to be 0.53, 1.30, and 2.49, respectively. these results show that the oxygen vacancies increase with increasing gd concentration. the fig. 8 (a, b) depicts the high-resolution gd4d xps spectra of the gd-doped samples.in the gd4d state, the spin-orbit splatted peaks are at 144.6 ev for gd4d3/2 and 139.6 ev for gd4d5/2 for the 2% gd-doped sample, whereas for the 5% gd-doped zno sample, the spin-orbit splits at 145.5 ev for gd4d3/2 and 139.7 ev for gd4d5/2 as shown in fig. 8 (a, b). this indicates that gd is present in the gd3+ state in the zno hexagonal structure. the shift in peak values of gd4d3/2 and gd4d5/2 from 144.6 ev and 139.6 ev, respectively; in the case of 2% gd-doped sample to 145.5 ev and 139.7 ev, respectively, in the case of 5% gd-doped sample. this shift in gd4d peaks is ascribed to the electron transfer from plasmonics gd to zno because of the strong electronic interaction (covalent bond) between gd and the oxide (ahmad et al. 2011; wang et al. 2012; bharathi et al. 2020). uv visible spectroscopy analysis the uv–visible spectroscopy is a powerful tool for estimating band gap of materials. uv–vis absorbance spectra and tauc plots for the gd-doped zno samples (gd = 0% (gora et al. 2022), 2%, and 5%) samples are shown in figs.9 (a, b, c, and d). the spectra show a red shift with increasing gd amount in the zno.the uv–vis absorption intensity of the synthesized polycrystalline samples is found to reduce with the increasing gd concentration (mazhdi and tafreshi 2018). tauc's plot has been used to calculate the direct band gap of the samples (jain et al. 2006). the direct band gap has been estimated using the following equation: here, α is the absorption coefficient,υ is frequency, h is the planck constant, a is a constant, and eg is the energy band gap of the substance. extrapolating the linear component of the curve plotted among (αhυ) 2 and hυ depicted in fig. 9 (b, c, and d) has been used to obtain the band gap (farhad et al. 2018; ghos et al. 2021). the band gap values calculated for the gd-doped zno samples, i.e.are 3.31 ev (gora et al. 2022), 3.27 ev, and 3.23ev, for the samples gd = 0%, 2% and 5%, respectively. the small redshift observed in the band gap of gd-doped zno samples is because of the changes in electronic structure as well as enhanced oxygen vacancies with the increasing gd doping (yi et al. 2017; flemban et al. 2016), which is responsible for the band gap reduction. photoluminescence spectroscopy analysis the structural flaws like ionic and atomic vacancies, replacements and interstitials have been explored using the pl spectra of the synthesized polycrystalline samples. fig. 10 (a, b and c) shows the deconvoluted, gaussian-fitted pl spectra of the synthesized gd-doped zno polycrystalline powder samples. the pl spectra of the samples were recorded at room temperature in order to determine the types of vacancies, defect band emission etc. (lin et al. 2001; yi et al. 2017). the photoluminescence spectra have been deconvoluted and the different peaks responsible for the emission have been gaussian fitted. for these samples the band edge emission peaksare detected at 381 nm, 384 nm, and 383 nm, for the gd = 0%, 2% and 5% samples, respectively. the uv emission is responsible for the excitonic interaction related to the band edge emission. the intense violet emission exhibited in the gd-doped zno at about 415 nm could be because ofthe oxygen vacancies. the exciton interaction between the holes in the valence band and electrons located in the interstitial zinc could be responsible for the violet emission peak at about 447 nm. intrinsic deficiencies like interstitial zinc and oxygen can be attributed to the peak at 477 nm (singh et al. 2009; kaur et al. 2016). the transformation between singly ionized oxygen deficiency and the photo-created holes (kennedy et al. 2014) or the surface imperfection and electrons near the conduction band, might be responsible for the green emission peak seen for the gd-doped znoat around 525 nm. the green emissions are commonly attributed to theoxygen vacancies (studenikin et al. 1998). for gd-doped zno polycrystalline powder samples, the intensity ratio of the green and ultra-violet emission peaks is found to be 0.090 for zno, 0.204 for the 2% gd-doped zno, and 0.418 for the 5% gd-doped zno. the defect-related emissions enhanced with increasing gd doping in the zno indicate that a large number of deficiencies, such as oxygen vacancies, are most usually related to crystal deformation (yi et al. 2017). the results reveal that the gd doping enhances the zni and vo flaws. it could be attributed to structural deformation created by gd atoms with different ionic sizes than zn in the zno (bandopadhyay and mitra 2015; sukumaran et al. 2021). increasing gd doping in zno indicates an increase in defect states, which matches well with the xps results. we compared our pl results with farhad et al. (2019), who prepared zno dc (drop casting) and zno nanorods. their pl results detected the pl peak at 380 nm and a barely observable green-yellow emission peak; in our case, we find it at 381 nm for zno, 384 nm for 2% gd-doped zno and 383 nm for the 5% gd-doped zno polycrystalline sample. this peak represented zno's near band edge (nbe) transition because of free excitons recombinations and this pl property indicates high crystalline quality. the luminescent characteristics in the visible region are responsible for the different defects, like zinc interstitials (zni), oxygen vacancies (vo), etc., present in the zno crystal matrix. as a result, they reported that both zno (dc) and zno nanorods were found to be defect-free good crystalline and optical properties materials. in our case, all the prepared gd-doped zno powder samples have been found to be with single ionized oxygen vacancies, which are confirmed by the green emission peak at 525 nm in the pl spectra. conclusion the gd-doped zno powder samples were synthesized by the solid-state reaction method. the xrd patterns affirm that gd has been successfully incorporated into the zno lattice and confirm the hexagonal wurtzite structure. sem images have been used to reveal the morphologies of the synthesized samples, which appear as rod-like structures. the xps results showed that the oxygen vacancy-related states in gd-doped samples increased with increasing gd doping. pl findings confirmed that the defect-related states are present in the gd-doped zno polycrystalline samples. the green emission and ultra-violet emission peaks' intensity ratio is 0.418 for the 5% gd-doped zno sample, which is the maximum compared to the pure zno and 2% gd-doped zno polycrystalline powder sample. these findings confirmed that the oxygen vacancies increase as the gd concentration increases and the pl results agree well with the xps results. the uv absorption spectra findings reveal that the band gap in the 5% gd-doped zno sample is found to be 3.23 ev, which is the minimum compared to both the pure zno and the 2% gd-doped zno samples, confirming that eg is reduced with increasing gd concentration. acknowledgment the authors are thankful to usic, university of rajasthan, jaipur, rajasthan (india), for providing sem images of the prepared samples. we also thank department of physics, banasthalividhyapith, banasthali, jaipur, rajasthan (india) for rendering xrd data. funding sources this research is not financed by any agency. authors' contribution sample preparation, data analysis, manuscript composition and writing (mahendra kumar gora); 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https://doi.org/10.1063/1.1394173 ma x and wang z (2012), the optical properties of rare earth gd doped zno nanocrystals, materials science in semiconductor processing. 15: 227-231. doi:10.1016/ j.mssp.2011.05.013 mazhdi m and tafreshi mj (2018), the effect of gadolinium doping on the structural, morphological, optical, and photoluminescence properties of zinc oxide nanoparticles prepared by co-precipitation method, applied physics a. 124: 863. https://doi.org/10.1007/ s00339 018-2291-0 monteiro t, neves aj, carmo mc, soares mj, peres m, alves e, rita e and wahl u (2006), optical and structural analysis of bulk zno samples undoped and rare earth doped by ion implantation, superlattices and microstructures. 39: 202-210. https://doi.org/10.1016/ j.spmi.2005.08.043 murtaza g, iqbal ma, xu yb, will ig and huang zc (2011), study of sm-doped zno samples sintered in a nitrogen atmosphere and deposited on n-si (1 0 0) by evaporation technique, j.magn. magn. mater. 323: 3239-3245. https://doi. org/10.1016/j.jmmm. 2011.07.021 obeid mm, jappor hr, almarzoki k, al-hydary ia, edrees sj and shukur mm (2019), unraveling the effect of gd doping on the structural, optical, and magnetic properties of zno based diluted magnetic semiconductor nanorods, rsc adv. 9: 33207-33221. doi: 10.1039/ c9ra04750f obeid mm, mogulkoc y, edress sj, ciftci yo, shukur mm and al-marzooqee mmh (2018), analysis of the structural, electronic, elastic and thermodynamic properties of cual2x4 (x = o, s) spinel structure, mater. res. bull. 108: 255-265. https://doi.org/10.1016/j.materresbull.2018.09.013 ohno h, shen a, matsukura f, oiwa a, endo a, katsumoto s and iye y (1996), (ga, mn) as: a new diluted magnetic semiconductor based on gaas, applied physics letters. 69: 363-365. https://doi.org/10.1063/1.118061 ozgür u, alivov yi, liu c, teke a, reshchikov ma, dogan s, avrutin v, cho sj and morkoc h (2005), a comprehensive review of zno materials and devices, journal of applied physics. 98: 41-301. https://doi.org/ 10.1063/1.1992666 potzger k, zhou s, eichhorn f, helm m, skorupa w, mucklich a and fassbender j (2006), ferromagnetic gd-implanted zno single crystals, j. appl. phys. 99: 63-906. https://doi.org/10.1063/1.2183350 sahu d, panda nr and acharya bs (2017), effect of gd doping on structure and photoluminescence properties of zno nanocrystals, mater. res. express. 4: 114001. https://doi.org/10.1088/2053-1591/aa9597 sambasivam s, joseph dp, naidu sa, hui kn, hui ks and choi bc (2015), intense violet–blue emission and paramagnetism of nanocrystalline gd3+ doped zno ceramics, j. adv. ceram. 4: 300-306. doi: 10.1007/s40145-015-0164-y shimogaki t, kawahara h, nakao s, higashihata m, ikenoue h, nakata y, nakamura d and okada t (2015), controlling znonano wire surface density during its growth by altering morphological properties of a zno buffer layer by uv laser irradiation, appl. phys. a. 118: 1239-1246. http://dx.doi.org/ 10.1007/ s00339-014 8822-4 singh ak, viswanath v and janu vc (2009), synthesis, effect of capping agents, structural, optical and photoluminescence properties of zno nanoparticles, j. lumin. 129: 874-878. https://doi.org/ 10.1016/j.jlumin.2009.03.027 studenikin sa, golego n and cocivera m (1998), fabrication of green and photoluminescent, undoped zno films using spray pyrolysis, j. appl. phys. 84: 2287-2294. https://doi.org/10.1063/1.368295 sukumaran a, sivanantham n, vinoth e and gopalakrishnan n (2021), ferromagnetism in gd-doped zno thin films mediated by defects, bull. mater. sci. 44: 259. http://dx.doi.org/ 10.1007/s12034-021-02550-y tan y, fang z, chen w and he p (2011),structural, optical and magnetic properties of eu-doped zno films,j. alloys compd. 509: 6321-6324. https://doi.org/ 10.1016/j.jallcom.2011.03.084 tawil snm, krishnamurthy d, kakimi r, emura s, hasegawa s and ashi h (2011), studies on the ingagdn/gan magnetic semiconductor heterostructures grown by plasma-assisted molecular-beam epitaxy, journal of crystal growth. 323: 351-354. https://doi.org/10. 1016/j.jcrysgro.2010.11.166 thangeeswari t, murugasen p and velmurugan j (2015), influence of co and dy doping on the optical and magnetic properties of zno nanoparticles for dms application, j. supercond. nov. magn. 28: 2505-2515. https://doi.org/10.1007/s10948-015-3045-2 wakano t, fujimura n, morinaga y, abe n, ashida a and ito t (2001), magnetic and magneto-transport properties of zno: ni films, physica e: low-dimensional systems and nanostructures. 10: 260-264. doi:10. 1016/s1386-9477(01)00095-9 wang xj, wang w and liu yl (2012), enhanced acetone sensing performance of au nanoparticles functionalized flower-like zno, sensors actuators b: chemical. 168: 39-45. https://doi.org/10.1016/j.snb.2012.01.006 yi xy, ma cy, yuan f, wang n, qin fw, hu bc and zhang qy (2017), structural, morphological, photoluminescence and photocatalytic properties of gd doped zno films, thin solid films. 636: 339-345. https://doi.org/10.1016/j.tsf.2017.05.020 doped zno nanocrystals also have an attractive optical responsiveness. many theoretical and experimental studies showed that re-doped zno could reportedly absorb ultraviolet (uv) light (chakraborty et al. 2017). obeid et al. (2019) prepared undoped and gd-doped zno nanocrystalline samples using the thermal decomposition method. they observed that the optical absorption spectra of pristine zno increased with a 6% gd doping concentration and the magnetic properties changed with changing dopant amounts. their pl spectroscopy results showed the existence of defects, which increased with increasing gd doping concentrations. they suggested that these dms nanoparticles can be used for magneto-optoelectronic practical device applications. undoubtedly, the re-doped zno nanostructures have been intensively studied recently because this is a rapidly growing field due to their multi-functionality and their use in possible new generation applications. with an aim to understand the effect of gd doping in zno in terms of its electronic and optical properties we have synthesize gd-doped zno powder series of different gd (0%, 2%, and 5%) values. various characterization techniques have been utilized to explore the electronic, structural and optical features of the synthesized powder series. gd doping into zno produced changes in the band gap and enhanced oxygen vacancies related states in the compound. materials and methods the gd-doped zno powder samples with varying gd (0%, 2%, and 5%) concentrations have been synthesized using the conventional solid-state reaction method. a suitable amount of high-purity (99.999% sigma-aldrich) zinc oxide (zno) and gadolinium oxide (gd2o3) powder have been used for their preparation. for achieving perfect homogeneity, the ingredients were properly pounded for ~8 hours in an agate mortar and pestle. the prepared material has been sintered for ~8h at~550°c and cooled at room temperature. again, the mixture was ground for ~2 hours and sintered for ~6 hours at ~550°c. the mixture was milled for ~4 hours before being turned into pellets. finally, these pellets were sintered for around ~8 hours at about ~600°c. finally, we ground the pellets to make the powder. the powder form of the prepared samples has been used for further characterization. characterization techniques the crystallographic structures of the samples have been explored using an x-ray diffractometer (make: panalytical x'pert pro) using the photon energy of cu kα (λ= 1.5406å). sem images have been used for the morphology study of the synthesized samples. the sem equipment model fig. 4. sem images of prepared polycrystalline powder samples: (a) for the zno (gora et al. 2022), (b) for the 2% gd-doped zno and (c) for the 5% gddoped zno electronic, structural and optical properties of gd-doped zno powder 58(1) 202358 re elements, such as gd, may introduce additional capabilities to the zno system because they may be capable of constructing combined practical devices on a single chip by combining magnetic and optical properties (ohno et al. 1996; tawil et al. 2011). rare-earth (re) metal doping in the dilute magnetic semiconductor (dms) systems has recently received immense attention due to its potential usage in magneto electronic and photonic devices (monteiro et al. 2006). the influence of gd doping on the optical and electrical properties of zno is crucial for developing optoelectronic devices and understanding the genesis of ferromagnetism. ma and wang (2012) synthesized the gd-doped zno nanocrystals using the thermal evaporation deposition method. according to their findings, gd doping has an appreciable impact on the optical characteristics of the zno. the strong uv and blue emissions are detected at low gd concentrations because gd impurities introduce a mid-gap state into zno. in comparison, the uv and blue emissions reduce for high doping concentrations as a significant broad defect emission appears because of the vast numbers of defects, impurities, and excess gd2o3 produced. gd-doped zno nanocrystals can be used in optoelectronic devices. the optical and electrical tuning of the carrier density and optical band gap energy is essential for developing luminescent materials and equipment based on the zno dms systems. the optical band gap and carrier concentration are essential parameters to yield information about the emission wavelength. several development characteristics, like the synthesis methods, impurity concentration and substrate variety have been reported to influence these parameters (wakano et al. 2001; tan et al. 2011; murtaza et al. 2011). the synthesis of dms materials with unique optical, photocatalytic and magnetic characteristics seems to be the most promising candidate for the subsequent generation of electronic, optoelectronic and spintronic appliances (kumar and sahare 2014). the low-dimension materials with imperfection-free lattice structures have excellent electrical and magnetic characteristics; purposefully made or accidental structural defects play a significant role in altering their features (li et al. 2016; obeid et al. 2018). thus, the presence of different kinds of cation or anion vacancies and interstitials in zno nanocrystals may change their magnetic properties, photoluminescence, and photocatalytic properties (coey et al. 2005). although certain experimental and theoretical findings based on dft indicate that gd-doped zno exhibits the room temperature ferromagnetism (rtfm) (potzger et al. 2006; aravindh et al. 2014) property, several studies have demonstrated that the rtfm is not present (sambasivam et al. 2015). in addition to their magnetic qualities, the 4f ions eth 30 kv evo-18 carl zeiss, with a tilt of 0° to 60° and a rotation of 360°, has been used for taking sem images.the defect-related states and chemical analysis of the samples have been determined using x-ray photoelectron spectroscopy. a hemispherical analyzer with a 128-channel detector and a monochromated, fully integrated k-alpha small-spot x-ray photoelectron spectrometer system of 180° double focusing is used in xps (thermo scientific made). the uv-visible absorption spectroscopy (model: shimadzu uv-3600 uv-vis-nir spectrophotometer) was used to explore the prepared samples' optical absorption and band gap. the measurements of uv-visible absorption spectra have been taken using the powder form of the samples. pl spectroscopy was used to analyze defect-related states in the prepared samples. photoluminescence spectra have been recorded at room temperature using the fluorescence spectrometer (model: perkin elmer fl 8500). results and discussion xrd analysis fig. 1. depicts the powder xrd patterns of the gd-doped zno (gd = 0%, 2%, and 5%) samples. all the diffraction peaks detected in the zno sample match with the standard jcpds card number (36-1451). this confirms a hexagonal wurtzite crystal structure of the samples. the diffraction peaks were observed at 31.88°, 34.50°, 36.25°, 47.72°, 56.69°, 63.03°, 66.59°, 68.17°, and 69.35°, which are related to the planes (100), (002), (101), (102), (110), (103), (200), (112), and (201), respectively (ganesh et al. 2018; bharathi et al. 2020). further, some additional small peaks have been observed at 28.61°, 33.21°, and 39.14° with increasing gd doping. these secondary peaks representing a crystallite phase have been identified as gd2o3, which is well consistent with earlier reports (das et al. 2012). as shown in fig. 2, the highest intense peak related to the (101) plane shifted slightly higher angles with the increasing concentration of gd doping. the shift is because of the substitution of bigger-sized gd3+ (0.94 å) ions than zn2+ (0.74 å) ions in the hexagonal wurtzite structure. the peak shift may indicate that gd3+ ions have occupied the crystallographic positions of zn2+ ions in the zno host lattice, or itmay be because of the structural strain caused by the formation of internal compressive micro stress (dakhel and el-hilo 2010; kumar et al. 2014; sahu et al. 2017). rietveld refinements have been performed using the full prof programme (shown in fig. 3). the pseudo-voigt function has been used for rietveld refinement of all the samples with the space group p63mc. the estimated lattice parameters have been listed in table i. the lattice parameters are found to decrease with gd doping, similar to those reported in earlier studies (kaur et al. 2016; obeid et al. 2019). the factors like the induced deficiencies (vacancies, interstitial) and the ionic radius of zn and gd ions can be responsible for the observed change (kaur et al. 2016; kumar and thangavel 2017). sem analysis scanning electron micrographs have been used to analyze the morphology of the gd-doped zno powder samples. the sem images reveal a rod-like morphology in pure zno (gora et al. 2022) and the gd-doped zno polycrystalline samples with some proof of agglomeration and phase segregation, as depicted in fig. 4 (a, b and c). profound observation of the particles exhibits that the crystallite size is above 100 nm. the particles were intensive and incompatibly distributed all over the mass. a distinct boundary between neighbouring crystallites can be noticed, despite the proximity of these smaller crystallites. xps analysis the xps technique is an excellent tool for determining the surface chemistry and electron configuration of the various elements present in a multicomponent material. the carbon c1s peak (284.6 ev) has been used as a reference to calibrate all the binding energies of the spectra. the survey spectrum of the gd-doped zno samples is shown in fig. 5. the survey spectra revealed the existence of o, zn, and gd elements without any impurity in the samples. for zno and 2% gd-doped zno powder samples, the binding energies of the zn2p3/2 and zn2p1/2 peaks are found to be 1021.25 ev, 1044.25 ev, 1021.43 ev, and 1044.43 ev, respectively. however, for the 5% gd-doped zno sample, these peaks are at 1021.83 and 1044.83 ev energy positions. the small shift could be assigned to the creation of zn interstitials in zno upon gd doping. the binding energy gap between the zinc doublet peaks has been found at about 23 ev. this indicates that zn in the zno crystal structure is in the zn2+ oxidation state (khataee et al. 2015; gawai et al. 2019) as the spin-orbital splitting of zn2p is 23 ev. this difference does not change with the gd doping pointing out that gd doping has no discernible effect on the chemical position of zno. the o1s asymmetric xps spectraare shown in fig.7 (a) which is asymmetric in shape. the o1s xps spectra of all these samples i.e. the zno, the zn0.98gd0.02o, and the zn0.95gd0.05o have been deconvoluted mainly into two gaussian peaks, as shown in fig. 7 (b, c, and d). the lower binding peaks for pure and gd-doped zno (gd = 2% and 5%) polycrystalline samples have been detected at 529.93 ev, 529.93 ev and 529.78 ev, respectively, which attributed to the lattice oxygen in the hexagonal structure of the zno. the higher binding peak for the pure and the gd-doped zno samples have been found at 531.51 ev, 531.66 ev, and 531.49 ev, respectively, which is due to the presence of oxygen vacancies in the zno structure (bharathi et al. 2020; sukumaran et al. 2021). an additional signal centered at 528.29 ev has been detected in the 5% gd-doped zno powder sample, which could be ascribed to the coordination of oxygen in gd-o-zn along grain boundaries because of the excessive gd dopants and also attributed to the presence of gd2o3 in the sample (yi et al. 2017). the lattice oxygen peak has slightly shifted to the lower binding energy with increasing gd concentration, which has been due to the increased oxygen vacancies with increasing gd doping. the estimated area ratios of the oxygen vacancies peak and the lattice oxygen peak for the samples zno, zn0.98gd0.02o, and zn0.95gd0.05o comes out to be 0.53, 1.30, and 2.49, respectively. these results show that the oxygen vacancies increase with increasing gd concentration. the fig. 8 (a, b) depicts the high-resolution gd4d xps spectra of the gd-doped samples.in the gd4d state, the spin-orbit splatted peaks are at 144.6 ev for gd4d3/2 and 139.6 ev for gd4d5/2 for the 2% gd-doped sample, whereas for the 5% gd-doped zno sample, the spin-orbit splits at 145.5 ev for gd4d3/2 and 139.7 ev for gd4d5/2 as shown in fig. 8 (a, b). this indicates that gd is present in the gd3+ state in the zno hexagonal structure. the shift in peak values of gd4d3/2 and gd4d5/2 from 144.6 ev and 139.6 ev, respectively; in the case of 2% gd-doped sample to 145.5 ev and 139.7 ev, respectively, in the case of 5% gd-doped sample. this shift in gd4d peaks is ascribed to the electron transfer from plasmonics gd to zno because of the strong electronic interaction (covalent bond) between gd and the oxide (ahmad et al. 2011; wang et al. 2012; bharathi et al. 2020). uv visible spectroscopy analysis the uv–visible spectroscopy is a powerful tool for estimating band gap of materials. uv–vis absorbance spectra and tauc plots for the gd-doped zno samples (gd = 0% (gora et al. 2022), 2%, and 5%) samples are shown in figs.9 (a, b, c, and d). the spectra show a red shift with increasing gd amount in the zno.the uv–vis absorption intensity of the synthesized polycrystalline samples is found to reduce with the increasing gd concentration (mazhdi and tafreshi 2018). tauc's plot has been used to calculate the direct band gap of the samples (jain et al. 2006). the direct band gap has been estimated using the following equation: here, α is the absorption coefficient,υ is frequency, h is the planck constant, a is a constant, and eg is the energy band gap of the substance. extrapolating the linear component of the curve plotted among (αhυ) 2 and hυ depicted in fig. 9 (b, c, and d) has been used to obtain the band gap (farhad et al. 2018; ghos et al. 2021). the band gap values calculated for the gd-doped zno samples, i.e.are 3.31 ev (gora et al. 2022), 3.27 ev, and 3.23ev, for the samples gd = 0%, 2% and 5%, respectively. the small redshift observed in the band gap of gd-doped zno samples is because of the changes in electronic structure as well as enhanced oxygen vacancies with the increasing gd doping (yi et al. 2017; flemban et al. 2016), which is responsible for the band gap reduction. photoluminescence spectroscopy analysis the structural flaws like ionic and atomic vacancies, replacements and interstitials have been explored using the pl spectra of the synthesized polycrystalline samples. fig. 10 (a, b and c) shows the deconvoluted, gaussian-fitted pl spectra of the synthesized gd-doped zno polycrystalline powder samples. the pl spectra of the samples were recorded at room temperature in order to determine the types of vacancies, defect band emission etc. (lin et al. 2001; yi et al. 2017). the photoluminescence spectra have been deconvoluted and the different peaks responsible for the emission have been gaussian fitted. for these samples the band edge emission peaksare detected at 381 nm, 384 nm, and 383 nm, for the gd = 0%, 2% and 5% samples, respectively. the uv emission is responsible for the excitonic interaction related to the band edge emission. the intense violet emission exhibited in the gd-doped zno at about 415 nm could be because ofthe oxygen vacancies. the exciton interaction between the holes in the valence band and electrons located in the interstitial zinc could be responsible for the violet emission peak at about 447 nm. intrinsic deficiencies like interstitial zinc and oxygen can be attributed to the peak at 477 nm (singh et al. 2009; kaur et al. 2016). the transformation between singly ionized oxygen deficiency and the photo-created holes (kennedy et al. 2014) or the surface imperfection and electrons near the conduction band, might be responsible for the green emission peak seen for the gd-doped znoat around 525 nm. the green emissions are commonly attributed to theoxygen vacancies (studenikin et al. 1998). for gd-doped zno polycrystalline powder samples, the intensity ratio of the green and ultra-violet emission peaks is found to be 0.090 for zno, 0.204 for the 2% gd-doped zno, and 0.418 for the 5% gd-doped zno. the defect-related emissions enhanced with increasing gd doping in the zno indicate that a large number of deficiencies, such as oxygen vacancies, are most usually related to crystal deformation (yi et al. 2017). the results reveal that the gd doping enhances the zni and vo flaws. it could be attributed to structural deformation created by gd atoms with different ionic sizes than zn in the zno (bandopadhyay and mitra 2015; sukumaran et al. 2021). increasing gd doping in zno indicates an increase in defect states, which matches well with the xps results. we compared our pl results with farhad et al. (2019), who prepared zno dc (drop casting) and zno nanorods. their pl results detected the pl peak at 380 nm and a barely observable green-yellow emission peak; in our case, we find it at 381 nm for zno, 384 nm for 2% gd-doped zno and 383 nm for the 5% gd-doped zno polycrystalline sample. this peak represented zno's near band edge (nbe) transition because of free excitons recombinations and this pl property indicates high crystalline quality. the luminescent characteristics in the visible region are responsible for the different defects, like zinc interstitials (zni), oxygen vacancies (vo), etc., present in the zno crystal matrix. as a result, they reported that both zno (dc) and zno nanorods were found to be defect-free good crystalline and optical properties materials. in our case, all the prepared gd-doped zno powder samples have been found to be with single ionized oxygen vacancies, which are confirmed by the green emission peak at 525 nm in the pl spectra. conclusion the gd-doped zno powder samples were synthesized by the solid-state reaction method. the xrd patterns affirm that gd has been successfully incorporated into the zno lattice and confirm the hexagonal wurtzite structure. sem images have been used to reveal the morphologies of the synthesized samples, which appear as rod-like structures. the xps results showed that the oxygen vacancy-related states in gd-doped samples increased with increasing gd doping. pl findings confirmed that the defect-related states are present in the gd-doped zno polycrystalline samples. the green emission and ultra-violet emission peaks' intensity ratio is 0.418 for the 5% gd-doped zno sample, which is the maximum compared to the pure zno and 2% gd-doped zno polycrystalline powder sample. these findings confirmed that the oxygen vacancies increase as the gd concentration increases and the pl results agree well with the xps results. the uv absorption spectra findings reveal that the band gap in the 5% gd-doped zno sample is found to be 3.23 ev, which is the minimum compared to both the pure zno and the 2% gd-doped zno samples, confirming that eg is reduced with increasing gd concentration. acknowledgment the authors are thankful to usic, university of rajasthan, jaipur, rajasthan (india), for providing sem images of the prepared samples. we also thank department of physics, banasthalividhyapith, banasthali, jaipur, rajasthan (india) for rendering xrd data. funding sources this research is not financed by any agency. authors' contribution sample preparation, data analysis, manuscript composition and writing (mahendra kumar gora); 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vc (2009), synthesis, effect of capping agents, structural, optical and photoluminescence properties of zno nanoparticles, j. lumin. 129: 874-878. https://doi.org/ 10.1016/j.jlumin.2009.03.027 studenikin sa, golego n and cocivera m (1998), fabrication of green and photoluminescent, undoped zno films using spray pyrolysis, j. appl. phys. 84: 2287-2294. https://doi.org/10.1063/1.368295 sukumaran a, sivanantham n, vinoth e and gopalakrishnan n (2021), ferromagnetism in gd-doped zno thin films mediated by defects, bull. mater. sci. 44: 259. http://dx.doi.org/ 10.1007/s12034-021-02550-y tan y, fang z, chen w and he p (2011),structural, optical and magnetic properties of eu-doped zno films,j. alloys compd. 509: 6321-6324. https://doi.org/ 10.1016/j.jallcom.2011.03.084 tawil snm, krishnamurthy d, kakimi r, emura s, hasegawa s and ashi h (2011), studies on the ingagdn/gan magnetic semiconductor heterostructures grown by plasma-assisted molecular-beam epitaxy, journal of crystal growth. 323: 351-354. https://doi.org/10. 1016/j.jcrysgro.2010.11.166 thangeeswari t, murugasen p and velmurugan j (2015), influence of co and dy doping on the optical and magnetic properties of zno nanoparticles for dms application, j. supercond. nov. magn. 28: 2505-2515. https://doi.org/10.1007/s10948-015-3045-2 wakano t, fujimura n, morinaga y, abe n, ashida a and ito t (2001), magnetic and magneto-transport properties of zno: ni films, physica e: low-dimensional systems and nanostructures. 10: 260-264. doi:10. 1016/s1386-9477(01)00095-9 wang xj, wang w and liu yl (2012), enhanced acetone sensing performance of au nanoparticles functionalized flower-like zno, sensors actuators b: chemical. 168: 39-45. https://doi.org/10.1016/j.snb.2012.01.006 yi xy, ma cy, yuan f, wang n, qin fw, hu bc and zhang qy (2017), structural, morphological, photoluminescence and photocatalytic properties of gd doped zno films, thin solid films. 636: 339-345. https://doi.org/10.1016/j.tsf.2017.05.020 doped zno nanocrystals also have an attractive optical responsiveness. many theoretical and experimental studies showed that re-doped zno could reportedly absorb ultraviolet (uv) light (chakraborty et al. 2017). obeid et al. (2019) prepared undoped and gd-doped zno nanocrystalline samples using the thermal decomposition method. they observed that the optical absorption spectra of pristine zno increased with a 6% gd doping concentration and the magnetic properties changed with changing dopant amounts. their pl spectroscopy results showed the existence of defects, which increased with increasing gd doping concentrations. they suggested that these dms nanoparticles can be used for magneto-optoelectronic practical device applications. undoubtedly, the re-doped zno nanostructures have been intensively studied recently because this is a rapidly growing field due to their multi-functionality and their use in possible new generation applications. with an aim to understand the effect of gd doping in zno in terms of its electronic and optical properties we have synthesize gd-doped zno powder series of different gd (0%, 2%, and 5%) values. various characterization techniques have been utilized to explore the electronic, structural and optical features of the synthesized powder series. gd doping into zno produced changes in the band gap and enhanced oxygen vacancies related states in the compound. materials and methods the gd-doped zno powder samples with varying gd (0%, 2%, and 5%) concentrations have been synthesized using the conventional solid-state reaction method. a suitable amount of high-purity (99.999% sigma-aldrich) zinc oxide (zno) and gadolinium oxide (gd2o3) powder have been used for their preparation. for achieving perfect homogeneity, the ingredients were properly pounded for ~8 hours in an agate mortar and pestle. the prepared material has been sintered for ~8h at~550°c and cooled at room temperature. again, the mixture was ground for ~2 hours and sintered for ~6 hours at ~550°c. the mixture was milled for ~4 hours before being turned into pellets. finally, these pellets were sintered for around ~8 hours at about ~600°c. finally, we ground the pellets to make the powder. the powder form of the prepared samples has been used for further characterization. characterization techniques the crystallographic structures of the samples have been explored using an x-ray diffractometer (make: panalytical x'pert pro) using the photon energy of cu kα (λ= 1.5406å). sem images have been used for the morphology study of the synthesized samples. the sem equipment model fig. 5. the xps survey spectra of the pure zno (gora et al. 2022), the zn0.98gd0.02o and the zn0.95gd0. 05o powder samples fig. 6. the zn2p core level xps spectra of the gd-doped zno polycrystalline powder samples the zn2p core level spectra of the gd-doped zno samples are depicted in fig. 6. αhυ = a (hυ eg) 1/2 gora, kumar, choudhary, dolia, kumar and singhal 59 re elements, such as gd, may introduce additional capabilities to the zno system because they may be capable of constructing combined practical devices on a single chip by combining magnetic and optical properties (ohno et al. 1996; tawil et al. 2011). rare-earth (re) metal doping in the dilute magnetic semiconductor (dms) systems has recently received immense attention due to its potential usage in magneto electronic and photonic devices (monteiro et al. 2006). the influence of gd doping on the optical and electrical properties of zno is crucial for developing optoelectronic devices and understanding the genesis of ferromagnetism. ma and wang (2012) synthesized the gd-doped zno nanocrystals using the thermal evaporation deposition method. according to their findings, gd doping has an appreciable impact on the optical characteristics of the zno. the strong uv and blue emissions are detected at low gd concentrations because gd impurities introduce a mid-gap state into zno. in comparison, the uv and blue emissions reduce for high doping concentrations as a significant broad defect emission appears because of the vast numbers of defects, impurities, and excess gd2o3 produced. gd-doped zno nanocrystals can be used in optoelectronic devices. the optical and electrical tuning of the carrier density and optical band gap energy is essential for developing luminescent materials and equipment based on the zno dms systems. the optical band gap and carrier concentration are essential parameters to yield information about the emission wavelength. several development characteristics, like the synthesis methods, impurity concentration and substrate variety have been reported to influence these parameters (wakano et al. 2001; tan et al. 2011; murtaza et al. 2011). the synthesis of dms materials with unique optical, photocatalytic and magnetic characteristics seems to be the most promising candidate for the subsequent generation of electronic, optoelectronic and spintronic appliances (kumar and sahare 2014). the low-dimension materials with imperfection-free lattice structures have excellent electrical and magnetic characteristics; purposefully made or accidental structural defects play a significant role in altering their features (li et al. 2016; obeid et al. 2018). thus, the presence of different kinds of cation or anion vacancies and interstitials in zno nanocrystals may change their magnetic properties, photoluminescence, and photocatalytic properties (coey et al. 2005). although certain experimental and theoretical findings based on dft indicate that gd-doped zno exhibits the room temperature ferromagnetism (rtfm) (potzger et al. 2006; aravindh et al. 2014) property, several studies have demonstrated that the rtfm is not present (sambasivam et al. 2015). in addition to their magnetic qualities, the 4f ions eth 30 kv evo-18 carl zeiss, with a tilt of 0° to 60° and a rotation of 360°, has been used for taking sem images.the defect-related states and chemical analysis of the samples have been determined using x-ray photoelectron spectroscopy. a hemispherical analyzer with a 128-channel detector and a monochromated, fully integrated k-alpha small-spot x-ray photoelectron spectrometer system of 180° double focusing is used in xps (thermo scientific made). the uv-visible absorption spectroscopy (model: shimadzu uv-3600 uv-vis-nir spectrophotometer) was used to explore the prepared samples' optical absorption and band gap. the measurements of uv-visible absorption spectra have been taken using the powder form of the samples. pl spectroscopy was used to analyze defect-related states in the prepared samples. photoluminescence spectra have been recorded at room temperature using the fluorescence spectrometer (model: perkin elmer fl 8500). results and discussion xrd analysis fig. 1. depicts the powder xrd patterns of the gd-doped zno (gd = 0%, 2%, and 5%) samples. all the diffraction peaks detected in the zno sample match with the standard jcpds card number (36-1451). this confirms a hexagonal wurtzite crystal structure of the samples. the diffraction peaks were observed at 31.88°, 34.50°, 36.25°, 47.72°, 56.69°, 63.03°, 66.59°, 68.17°, and 69.35°, which are related to the planes (100), (002), (101), (102), (110), (103), (200), (112), and (201), respectively (ganesh et al. 2018; bharathi et al. 2020). further, some additional small peaks have been observed at 28.61°, 33.21°, and 39.14° with increasing gd doping. these secondary peaks representing a crystallite phase have been identified as gd2o3, which is well consistent with earlier reports (das et al. 2012). as shown in fig. 2, the highest intense peak related to the (101) plane shifted slightly higher angles with the increasing concentration of gd doping. the shift is because of the substitution of bigger-sized gd3+ (0.94 å) ions than zn2+ (0.74 å) ions in the hexagonal wurtzite structure. the peak shift may indicate that gd3+ ions have occupied the crystallographic positions of zn2+ ions in the zno host lattice, or itmay be because of the structural strain caused by the formation of internal compressive micro stress (dakhel and el-hilo 2010; kumar et al. 2014; sahu et al. 2017). rietveld refinements have been performed using the full prof programme (shown in fig. 3). the pseudo-voigt function has been used for rietveld refinement of all the samples with the space group p63mc. the estimated lattice parameters have been listed in table i. the lattice parameters are found to decrease with gd doping, similar to those reported in earlier studies (kaur et al. 2016; obeid et al. 2019). the factors like the induced deficiencies (vacancies, interstitial) and the ionic radius of zn and gd ions can be responsible for the observed change (kaur et al. 2016; kumar and thangavel 2017). sem analysis scanning electron micrographs have been used to analyze the morphology of the gd-doped zno powder samples. the sem images reveal a rod-like morphology in pure zno (gora et al. 2022) and the gd-doped zno polycrystalline samples with some proof of agglomeration and phase segregation, as depicted in fig. 4 (a, b and c). profound observation of the particles exhibits that the crystallite size is above 100 nm. the particles were intensive and incompatibly distributed all over the mass. a distinct boundary between neighbouring crystallites can be noticed, despite the proximity of these smaller crystallites. xps analysis the xps technique is an excellent tool for determining the surface chemistry and electron configuration of the various elements present in a multicomponent material. the carbon c1s peak (284.6 ev) has been used as a reference to calibrate all the binding energies of the spectra. the survey spectrum of the gd-doped zno samples is shown in fig. 5. the survey spectra revealed the existence of o, zn, and gd elements without any impurity in the samples. for zno and 2% gd-doped zno powder samples, the binding energies of the zn2p3/2 and zn2p1/2 peaks are found to be 1021.25 ev, 1044.25 ev, 1021.43 ev, and 1044.43 ev, respectively. however, for the 5% gd-doped zno sample, these peaks are at 1021.83 and 1044.83 ev energy positions. the small shift could be assigned to the creation of zn interstitials in zno upon gd doping. the binding energy gap between the zinc doublet peaks has been found at about 23 ev. this indicates that zn in the zno crystal structure is in the zn2+ oxidation state (khataee et al. 2015; gawai et al. 2019) as the spin-orbital splitting of zn2p is 23 ev. this difference does not change with the gd doping pointing out that gd doping has no discernible effect on the chemical position of zno. the o1s asymmetric xps spectraare shown in fig.7 (a) which is asymmetric in shape. the o1s xps spectra of all these samples i.e. the zno, the zn0.98gd0.02o, and the zn0.95gd0.05o have been deconvoluted mainly into two gaussian peaks, as shown in fig. 7 (b, c, and d). the lower binding peaks for pure and gd-doped zno (gd = 2% and 5%) polycrystalline samples have been detected at 529.93 ev, 529.93 ev and 529.78 ev, respectively, which attributed to the lattice oxygen in the hexagonal structure of the zno. the higher binding peak for the pure and the gd-doped zno samples have been found at 531.51 ev, 531.66 ev, and 531.49 ev, respectively, which is due to the presence of oxygen vacancies in the zno structure (bharathi et al. 2020; sukumaran et al. 2021). an additional signal centered at 528.29 ev has been detected in the 5% gd-doped zno powder sample, which could be ascribed to the coordination of oxygen in gd-o-zn along grain boundaries because of the excessive gd dopants and also attributed to the presence of gd2o3 in the sample (yi et al. 2017). the lattice oxygen peak has slightly shifted to the lower binding energy with increasing gd concentration, which has been due to the increased oxygen vacancies with increasing gd doping. the estimated area ratios of the oxygen vacancies peak and the lattice oxygen peak for the samples zno, zn0.98gd0.02o, and zn0.95gd0.05o comes out to be 0.53, 1.30, and 2.49, respectively. these results show that the oxygen vacancies increase with increasing gd concentration. the fig. 8 (a, b) depicts the high-resolution gd4d xps spectra of the gd-doped samples.in the gd4d state, the spin-orbit splatted peaks are at 144.6 ev for gd4d3/2 and 139.6 ev for gd4d5/2 for the 2% gd-doped sample, whereas for the 5% gd-doped zno sample, the spin-orbit splits at 145.5 ev for gd4d3/2 and 139.7 ev for gd4d5/2 as shown in fig. 8 (a, b). this indicates that gd is present in the gd3+ state in the zno hexagonal structure. the shift in peak values of gd4d3/2 and gd4d5/2 from 144.6 ev and 139.6 ev, respectively; in the case of 2% gd-doped sample to 145.5 ev and 139.7 ev, respectively, in the case of 5% gd-doped sample. this shift in gd4d peaks is ascribed to the electron transfer from plasmonics gd to zno because of the strong electronic interaction (covalent bond) between gd and the oxide (ahmad et al. 2011; wang et al. 2012; bharathi et al. 2020). uv visible spectroscopy analysis the uv–visible spectroscopy is a powerful tool for estimating band gap of materials. uv–vis absorbance spectra and tauc plots for the gd-doped zno samples (gd = 0% (gora et al. 2022), 2%, and 5%) samples are shown in figs.9 (a, b, c, and d). the spectra show a red shift with increasing gd amount in the zno.the uv–vis absorption intensity of the synthesized polycrystalline samples is found to reduce with the increasing gd concentration (mazhdi and tafreshi 2018). tauc's plot has been used to calculate the direct band gap of the samples (jain et al. 2006). the direct band gap has been estimated using the following equation: here, α is the absorption coefficient,υ is frequency, h is the planck constant, a is a constant, and eg is the energy band gap of the substance. extrapolating the linear component of the curve plotted among (αhυ) 2 and hυ depicted in fig. 9 (b, c, and d) has been used to obtain the band gap (farhad et al. 2018; ghos et al. 2021). the band gap values calculated for the gd-doped zno samples, i.e.are 3.31 ev (gora et al. 2022), 3.27 ev, and 3.23ev, for the samples gd = 0%, 2% and 5%, respectively. the small redshift observed in the band gap of gd-doped zno samples is because of the changes in electronic structure as well as enhanced oxygen vacancies with the increasing gd doping (yi et al. 2017; flemban et al. 2016), which is responsible for the band gap reduction. photoluminescence spectroscopy analysis the structural flaws like ionic and atomic vacancies, replacements and interstitials have been explored using the pl spectra of the synthesized polycrystalline samples. fig. 10 (a, b and c) shows the deconvoluted, gaussian-fitted pl spectra of the synthesized gd-doped zno polycrystalline powder samples. the pl spectra of the samples were recorded at room temperature in order to determine the types of vacancies, defect band emission etc. (lin et al. 2001; yi et al. 2017). the photoluminescence spectra have been deconvoluted and the different peaks responsible for the emission have been gaussian fitted. for these samples the band edge emission peaksare detected at 381 nm, 384 nm, and 383 nm, for the gd = 0%, 2% and 5% samples, respectively. the uv emission is responsible for the excitonic interaction related to the band edge emission. the intense violet emission exhibited in the gd-doped zno at about 415 nm could be because ofthe oxygen vacancies. the exciton interaction between the holes in the valence band and electrons located in the interstitial zinc could be responsible for the violet emission peak at about 447 nm. intrinsic deficiencies like interstitial zinc and oxygen can be attributed to the peak at 477 nm (singh et al. 2009; kaur et al. 2016). the transformation between singly ionized oxygen deficiency and the photo-created holes (kennedy et al. 2014) or the surface imperfection and electrons near the conduction band, might be responsible for the green emission peak seen for the gd-doped znoat around 525 nm. the green emissions are commonly attributed to theoxygen vacancies (studenikin et al. 1998). for gd-doped zno polycrystalline powder samples, the intensity ratio of the green and ultra-violet emission peaks is found to be 0.090 for zno, 0.204 for the 2% gd-doped zno, and 0.418 for the 5% gd-doped zno. the defect-related emissions enhanced with increasing gd doping in the zno indicate that a large number of deficiencies, such as oxygen vacancies, are most usually related to crystal deformation (yi et al. 2017). the results reveal that the gd doping enhances the zni and vo flaws. it could be attributed to structural deformation created by gd atoms with different ionic sizes than zn in the zno (bandopadhyay and mitra 2015; sukumaran et al. 2021). increasing gd doping in zno indicates an increase in defect states, which matches well with the xps results. we compared our pl results with farhad et al. (2019), who prepared zno dc (drop casting) and zno nanorods. their pl results detected the pl peak at 380 nm and a barely observable green-yellow emission peak; in our case, we find it at 381 nm for zno, 384 nm for 2% gd-doped zno and 383 nm for the 5% gd-doped zno polycrystalline sample. this peak represented zno's near band edge (nbe) transition because of free excitons recombinations and this pl property indicates high crystalline quality. the luminescent characteristics in the visible region are responsible for the different defects, like zinc interstitials (zni), oxygen vacancies (vo), etc., present in the zno crystal matrix. as a result, they reported that both zno (dc) and zno nanorods were found to be defect-free good crystalline and optical properties materials. in our case, all the prepared gd-doped zno powder samples have been found to be with single ionized oxygen vacancies, which are confirmed by the green emission peak at 525 nm in the pl spectra. conclusion the gd-doped zno powder samples were synthesized by the solid-state reaction method. the xrd patterns affirm that gd has been successfully incorporated into the zno lattice and confirm the hexagonal wurtzite structure. sem images have been used to reveal the morphologies of the synthesized samples, which appear as rod-like structures. the xps results showed that the oxygen vacancy-related states in gd-doped samples increased with increasing gd doping. pl findings confirmed that the defect-related states are present in the gd-doped zno polycrystalline samples. the green emission and ultra-violet emission peaks' intensity ratio is 0.418 for the 5% gd-doped zno sample, which is the maximum compared to the pure zno and 2% gd-doped zno polycrystalline powder sample. these findings confirmed that the oxygen vacancies increase as the gd concentration increases and the pl results agree well with the xps results. the uv absorption spectra findings reveal that the band gap in the 5% gd-doped zno sample is found to be 3.23 ev, which is the minimum compared to both the pure zno and the 2% gd-doped zno samples, confirming that eg is reduced with increasing gd concentration. acknowledgment the authors are thankful to usic, university of rajasthan, jaipur, rajasthan (india), for providing sem images of the prepared samples. we also thank department of physics, banasthalividhyapith, banasthali, jaipur, rajasthan (india) for rendering xrd data. funding sources this research is not financed by any agency. authors' contribution sample preparation, data analysis, manuscript composition and writing (mahendra kumar gora); 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351-354. https://doi.org/10. 1016/j.jcrysgro.2010.11.166 thangeeswari t, murugasen p and velmurugan j (2015), influence of co and dy doping on the optical and magnetic properties of zno nanoparticles for dms application, j. supercond. nov. magn. 28: 2505-2515. https://doi.org/10.1007/s10948-015-3045-2 wakano t, fujimura n, morinaga y, abe n, ashida a and ito t (2001), magnetic and magneto-transport properties of zno: ni films, physica e: low-dimensional systems and nanostructures. 10: 260-264. doi:10. 1016/s1386-9477(01)00095-9 wang xj, wang w and liu yl (2012), enhanced acetone sensing performance of au nanoparticles functionalized flower-like zno, sensors actuators b: chemical. 168: 39-45. https://doi.org/10.1016/j.snb.2012.01.006 yi xy, ma cy, yuan f, wang n, qin fw, hu bc and zhang qy (2017), structural, morphological, photoluminescence and photocatalytic properties of gd doped zno films, thin solid films. 636: 339-345. https://doi.org/10.1016/j.tsf.2017.05.020 doped zno nanocrystals also have an attractive optical responsiveness. many theoretical and experimental studies showed that re-doped zno could reportedly absorb ultraviolet (uv) light (chakraborty et al. 2017). obeid et al. (2019) prepared undoped and gd-doped zno nanocrystalline samples using the thermal decomposition method. they observed that the optical absorption spectra of pristine zno increased with a 6% gd doping concentration and the magnetic properties changed with changing dopant amounts. their pl spectroscopy results showed the existence of defects, which increased with increasing gd doping concentrations. they suggested that these dms nanoparticles can be used for magneto-optoelectronic practical device applications. undoubtedly, the re-doped zno nanostructures have been intensively studied recently because this is a rapidly growing field due to their multi-functionality and their use in possible new generation applications. with an aim to understand the effect of gd doping in zno in terms of its electronic and optical properties we have synthesize gd-doped zno powder series of different gd (0%, 2%, and 5%) values. various characterization techniques have been utilized to explore the electronic, structural and optical features of the synthesized powder series. gd doping into zno produced changes in the band gap and enhanced oxygen vacancies related states in the compound. materials and methods the gd-doped zno powder samples with varying gd (0%, 2%, and 5%) concentrations have been synthesized using the conventional solid-state reaction method. a suitable amount of high-purity (99.999% sigma-aldrich) zinc oxide (zno) and gadolinium oxide (gd2o3) powder have been used for their preparation. for achieving perfect homogeneity, the ingredients were properly pounded for ~8 hours in an agate mortar and pestle. the prepared material has been sintered for ~8h at~550°c and cooled at room temperature. again, the mixture was ground for ~2 hours and sintered for ~6 hours at ~550°c. the mixture was milled for ~4 hours before being turned into pellets. finally, these pellets were sintered for around ~8 hours at about ~600°c. finally, we ground the pellets to make the powder. the powder form of the prepared samples has been used for further characterization. characterization techniques the crystallographic structures of the samples have been explored using an x-ray diffractometer (make: panalytical x'pert pro) using the photon energy of cu kα (λ= 1.5406å). sem images have been used for the morphology study of the synthesized samples. the sem equipment model fig. 7. o1s xps spectra: (a) asymmetric spectra for all gd-doped zno bulk samples (gd = 0%, 2% and 5%); (b) for the zno: fitted with two gaussian peaks; (c) for the 2% gd-doped zno polycrystalline sample: fitted with two gaussian peaks; (d) for the 5% gd-doped zno polycrystalline powder sample: fitted with three gaussian peaks electronic, structural and optical properties of gd-doped zno powder60 58(1) 2023 re elements, such as gd, may introduce additional capabilities to the zno system because they may be capable of constructing combined practical devices on a single chip by combining magnetic and optical properties (ohno et al. 1996; tawil et al. 2011). rare-earth (re) metal doping in the dilute magnetic semiconductor (dms) systems has recently received immense attention due to its potential usage in magneto electronic and photonic devices (monteiro et al. 2006). the influence of gd doping on the optical and electrical properties of zno is crucial for developing optoelectronic devices and understanding the genesis of ferromagnetism. ma and wang (2012) synthesized the gd-doped zno nanocrystals using the thermal evaporation deposition method. according to their findings, gd doping has an appreciable impact on the optical characteristics of the zno. the strong uv and blue emissions are detected at low gd concentrations because gd impurities introduce a mid-gap state into zno. in comparison, the uv and blue emissions reduce for high doping concentrations as a significant broad defect emission appears because of the vast numbers of defects, impurities, and excess gd2o3 produced. gd-doped zno nanocrystals can be used in optoelectronic devices. the optical and electrical tuning of the carrier density and optical band gap energy is essential for developing luminescent materials and equipment based on the zno dms systems. the optical band gap and carrier concentration are essential parameters to yield information about the emission wavelength. several development characteristics, like the synthesis methods, impurity concentration and substrate variety have been reported to influence these parameters (wakano et al. 2001; tan et al. 2011; murtaza et al. 2011). the synthesis of dms materials with unique optical, photocatalytic and magnetic characteristics seems to be the most promising candidate for the subsequent generation of electronic, optoelectronic and spintronic appliances (kumar and sahare 2014). the low-dimension materials with imperfection-free lattice structures have excellent electrical and magnetic characteristics; purposefully made or accidental structural defects play a significant role in altering their features (li et al. 2016; obeid et al. 2018). thus, the presence of different kinds of cation or anion vacancies and interstitials in zno nanocrystals may change their magnetic properties, photoluminescence, and photocatalytic properties (coey et al. 2005). although certain experimental and theoretical findings based on dft indicate that gd-doped zno exhibits the room temperature ferromagnetism (rtfm) (potzger et al. 2006; aravindh et al. 2014) property, several studies have demonstrated that the rtfm is not present (sambasivam et al. 2015). in addition to their magnetic qualities, the 4f ions eth 30 kv evo-18 carl zeiss, with a tilt of 0° to 60° and a rotation of 360°, has been used for taking sem images.the defect-related states and chemical analysis of the samples have been determined using x-ray photoelectron spectroscopy. a hemispherical analyzer with a 128-channel detector and a monochromated, fully integrated k-alpha small-spot x-ray photoelectron spectrometer system of 180° double focusing is used in xps (thermo scientific made). the uv-visible absorption spectroscopy (model: shimadzu uv-3600 uv-vis-nir spectrophotometer) was used to explore the prepared samples' optical absorption and band gap. the measurements of uv-visible absorption spectra have been taken using the powder form of the samples. pl spectroscopy was used to analyze defect-related states in the prepared samples. photoluminescence spectra have been recorded at room temperature using the fluorescence spectrometer (model: perkin elmer fl 8500). results and discussion xrd analysis fig. 1. depicts the powder xrd patterns of the gd-doped zno (gd = 0%, 2%, and 5%) samples. all the diffraction peaks detected in the zno sample match with the standard jcpds card number (36-1451). this confirms a hexagonal wurtzite crystal structure of the samples. the diffraction peaks were observed at 31.88°, 34.50°, 36.25°, 47.72°, 56.69°, 63.03°, 66.59°, 68.17°, and 69.35°, which are related to the planes (100), (002), (101), (102), (110), (103), (200), (112), and (201), respectively (ganesh et al. 2018; bharathi et al. 2020). further, some additional small peaks have been observed at 28.61°, 33.21°, and 39.14° with increasing gd doping. these secondary peaks representing a crystallite phase have been identified as gd2o3, which is well consistent with earlier reports (das et al. 2012). as shown in fig. 2, the highest intense peak related to the (101) plane shifted slightly higher angles with the increasing concentration of gd doping. the shift is because of the substitution of bigger-sized gd3+ (0.94 å) ions than zn2+ (0.74 å) ions in the hexagonal wurtzite structure. the peak shift may indicate that gd3+ ions have occupied the crystallographic positions of zn2+ ions in the zno host lattice, or itmay be because of the structural strain caused by the formation of internal compressive micro stress (dakhel and el-hilo 2010; kumar et al. 2014; sahu et al. 2017). rietveld refinements have been performed using the full prof programme (shown in fig. 3). the pseudo-voigt function has been used for rietveld refinement of all the samples with the space group p63mc. the estimated lattice parameters have been listed in table i. the lattice parameters are found to decrease with gd doping, similar to those reported in earlier studies (kaur et al. 2016; obeid et al. 2019). the factors like the induced deficiencies (vacancies, interstitial) and the ionic radius of zn and gd ions can be responsible for the observed change (kaur et al. 2016; kumar and thangavel 2017). sem analysis scanning electron micrographs have been used to analyze the morphology of the gd-doped zno powder samples. the sem images reveal a rod-like morphology in pure zno (gora et al. 2022) and the gd-doped zno polycrystalline samples with some proof of agglomeration and phase segregation, as depicted in fig. 4 (a, b and c). profound observation of the particles exhibits that the crystallite size is above 100 nm. the particles were intensive and incompatibly distributed all over the mass. a distinct boundary between neighbouring crystallites can be noticed, despite the proximity of these smaller crystallites. xps analysis the xps technique is an excellent tool for determining the surface chemistry and electron configuration of the various elements present in a multicomponent material. the carbon c1s peak (284.6 ev) has been used as a reference to calibrate all the binding energies of the spectra. the survey spectrum of the gd-doped zno samples is shown in fig. 5. the survey spectra revealed the existence of o, zn, and gd elements without any impurity in the samples. for zno and 2% gd-doped zno powder samples, the binding energies of the zn2p3/2 and zn2p1/2 peaks are found to be 1021.25 ev, 1044.25 ev, 1021.43 ev, and 1044.43 ev, respectively. however, for the 5% gd-doped zno sample, these peaks are at 1021.83 and 1044.83 ev energy positions. the small shift could be assigned to the creation of zn interstitials in zno upon gd doping. the binding energy gap between the zinc doublet peaks has been found at about 23 ev. this indicates that zn in the zno crystal structure is in the zn2+ oxidation state (khataee et al. 2015; gawai et al. 2019) as the spin-orbital splitting of zn2p is 23 ev. this difference does not change with the gd doping pointing out that gd doping has no discernible effect on the chemical position of zno. the o1s asymmetric xps spectraare shown in fig.7 (a) which is asymmetric in shape. the o1s xps spectra of all these samples i.e. the zno, the zn0.98gd0.02o, and the zn0.95gd0.05o have been deconvoluted mainly into two gaussian peaks, as shown in fig. 7 (b, c, and d). the lower binding peaks for pure and gd-doped zno (gd = 2% and 5%) polycrystalline samples have been detected at 529.93 ev, 529.93 ev and 529.78 ev, respectively, which attributed to the lattice oxygen in the hexagonal structure of the zno. the higher binding peak for the pure and the gd-doped zno samples have been found at 531.51 ev, 531.66 ev, and 531.49 ev, respectively, which is due to the presence of oxygen vacancies in the zno structure (bharathi et al. 2020; sukumaran et al. 2021). an additional signal centered at 528.29 ev has been detected in the 5% gd-doped zno powder sample, which could be ascribed to the coordination of oxygen in gd-o-zn along grain boundaries because of the excessive gd dopants and also attributed to the presence of gd2o3 in the sample (yi et al. 2017). the lattice oxygen peak has slightly shifted to the lower binding energy with increasing gd concentration, which has been due to the increased oxygen vacancies with increasing gd doping. the estimated area ratios of the oxygen vacancies peak and the lattice oxygen peak for the samples zno, zn0.98gd0.02o, and zn0.95gd0.05o comes out to be 0.53, 1.30, and 2.49, respectively. these results show that the oxygen vacancies increase with increasing gd concentration. the fig. 8 (a, b) depicts the high-resolution gd4d xps spectra of the gd-doped samples.in the gd4d state, the spin-orbit splatted peaks are at 144.6 ev for gd4d3/2 and 139.6 ev for gd4d5/2 for the 2% gd-doped sample, whereas for the 5% gd-doped zno sample, the spin-orbit splits at 145.5 ev for gd4d3/2 and 139.7 ev for gd4d5/2 as shown in fig. 8 (a, b). this indicates that gd is present in the gd3+ state in the zno hexagonal structure. the shift in peak values of gd4d3/2 and gd4d5/2 from 144.6 ev and 139.6 ev, respectively; in the case of 2% gd-doped sample to 145.5 ev and 139.7 ev, respectively, in the case of 5% gd-doped sample. this shift in gd4d peaks is ascribed to the electron transfer from plasmonics gd to zno because of the strong electronic interaction (covalent bond) between gd and the oxide (ahmad et al. 2011; wang et al. 2012; bharathi et al. 2020). uv visible spectroscopy analysis the uv–visible spectroscopy is a powerful tool for estimating band gap of materials. uv–vis absorbance spectra and tauc plots for the gd-doped zno samples (gd = 0% (gora et al. 2022), 2%, and 5%) samples are shown in figs.9 (a, b, c, and d). the spectra show a red shift with increasing gd amount in the zno.the uv–vis absorption intensity of the synthesized polycrystalline samples is found to reduce with the increasing gd concentration (mazhdi and tafreshi 2018). tauc's plot has been used to calculate the direct band gap of the samples (jain et al. 2006). the direct band gap has been estimated using the following equation: here, α is the absorption coefficient,υ is frequency, h is the planck constant, a is a constant, and eg is the energy band gap of the substance. extrapolating the linear component of the curve plotted among (αhυ) 2 and hυ depicted in fig. 9 (b, c, and d) has been used to obtain the band gap (farhad et al. 2018; ghos et al. 2021). the band gap values calculated for the gd-doped zno samples, i.e.are 3.31 ev (gora et al. 2022), 3.27 ev, and 3.23ev, for the samples gd = 0%, 2% and 5%, respectively. the small redshift observed in the band gap of gd-doped zno samples is because of the changes in electronic structure as well as enhanced oxygen vacancies with the increasing gd doping (yi et al. 2017; flemban et al. 2016), which is responsible for the band gap reduction. photoluminescence spectroscopy analysis the structural flaws like ionic and atomic vacancies, replacements and interstitials have been explored using the pl spectra of the synthesized polycrystalline samples. fig. 10 (a, b and c) shows the deconvoluted, gaussian-fitted pl spectra of the synthesized gd-doped zno polycrystalline powder samples. the pl spectra of the samples were recorded at room temperature in order to determine the types of vacancies, defect band emission etc. (lin et al. 2001; yi et al. 2017). the photoluminescence spectra have been deconvoluted and the different peaks responsible for the emission have been gaussian fitted. for these samples the band edge emission peaksare detected at 381 nm, 384 nm, and 383 nm, for the gd = 0%, 2% and 5% samples, respectively. the uv emission is responsible for the excitonic interaction related to the band edge emission. the intense violet emission exhibited in the gd-doped zno at about 415 nm could be because ofthe oxygen vacancies. the exciton interaction between the holes in the valence band and electrons located in the interstitial zinc could be responsible for the violet emission peak at about 447 nm. intrinsic deficiencies like interstitial zinc and oxygen can be attributed to the peak at 477 nm (singh et al. 2009; kaur et al. 2016). the transformation between singly ionized oxygen deficiency and the photo-created holes (kennedy et al. 2014) or the surface imperfection and electrons near the conduction band, might be responsible for the green emission peak seen for the gd-doped znoat around 525 nm. the green emissions are commonly attributed to theoxygen vacancies (studenikin et al. 1998). for gd-doped zno polycrystalline powder samples, the intensity ratio of the green and ultra-violet emission peaks is found to be 0.090 for zno, 0.204 for the 2% gd-doped zno, and 0.418 for the 5% gd-doped zno. the defect-related emissions enhanced with increasing gd doping in the zno indicate that a large number of deficiencies, such as oxygen vacancies, are most usually related to crystal deformation (yi et al. 2017). the results reveal that the gd doping enhances the zni and vo flaws. it could be attributed to structural deformation created by gd atoms with different ionic sizes than zn in the zno (bandopadhyay and mitra 2015; sukumaran et al. 2021). increasing gd doping in zno indicates an increase in defect states, which matches well with the xps results. we compared our pl results with farhad et al. (2019), who prepared zno dc (drop casting) and zno nanorods. their pl results detected the pl peak at 380 nm and a barely observable green-yellow emission peak; in our case, we find it at 381 nm for zno, 384 nm for 2% gd-doped zno and 383 nm for the 5% gd-doped zno polycrystalline sample. this peak represented zno's near band edge (nbe) transition because of free excitons recombinations and this pl property indicates high crystalline quality. the luminescent characteristics in the visible region are responsible for the different defects, like zinc interstitials (zni), oxygen vacancies (vo), etc., present in the zno crystal matrix. as a result, they reported that both zno (dc) and zno nanorods were found to be defect-free good crystalline and optical properties materials. in our case, all the prepared gd-doped zno powder samples have been found to be with single ionized oxygen vacancies, which are confirmed by the green emission peak at 525 nm in the pl spectra. conclusion the gd-doped zno powder samples were synthesized by the solid-state reaction method. the xrd patterns affirm that gd has been successfully incorporated into the zno lattice and confirm the hexagonal wurtzite structure. sem images have been used to reveal the morphologies of the synthesized samples, which appear as rod-like structures. the xps results showed that the oxygen vacancy-related states in gd-doped samples increased with increasing gd doping. pl findings confirmed that the defect-related states are present in the gd-doped zno polycrystalline samples. the green emission and ultra-violet emission peaks' intensity ratio is 0.418 for the 5% gd-doped zno sample, which is the maximum compared to the pure zno and 2% gd-doped zno polycrystalline powder sample. these findings confirmed that the oxygen vacancies increase as the gd concentration increases and the pl results agree well with the xps results. the uv absorption spectra findings reveal that the band gap in the 5% gd-doped zno sample is found to be 3.23 ev, which is the minimum compared to both the pure zno and the 2% gd-doped zno samples, confirming that eg is reduced with increasing gd concentration. acknowledgment the authors are thankful to usic, university of rajasthan, jaipur, rajasthan (india), for providing sem images of the prepared samples. we also thank department of physics, banasthalividhyapith, banasthali, jaipur, rajasthan (india) for rendering xrd data. funding sources this research is not financed by any agency. authors' contribution sample preparation, data analysis, manuscript composition and writing (mahendra kumar gora); 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nanocrystals also have an attractive optical responsiveness. many theoretical and experimental studies showed that re-doped zno could reportedly absorb ultraviolet (uv) light (chakraborty et al. 2017). obeid et al. (2019) prepared undoped and gd-doped zno nanocrystalline samples using the thermal decomposition method. they observed that the optical absorption spectra of pristine zno increased with a 6% gd doping concentration and the magnetic properties changed with changing dopant amounts. their pl spectroscopy results showed the existence of defects, which increased with increasing gd doping concentrations. they suggested that these dms nanoparticles can be used for magneto-optoelectronic practical device applications. undoubtedly, the re-doped zno nanostructures have been intensively studied recently because this is a rapidly growing field due to their multi-functionality and their use in possible new generation applications. with an aim to understand the effect of gd doping in zno in terms of its electronic and optical properties we have synthesize gd-doped zno powder series of different gd (0%, 2%, and 5%) values. various characterization techniques have been utilized to explore the electronic, structural and optical features of the synthesized powder series. gd doping into zno produced changes in the band gap and enhanced oxygen vacancies related states in the compound. materials and methods the gd-doped zno powder samples with varying gd (0%, 2%, and 5%) concentrations have been synthesized using the conventional solid-state reaction method. a suitable amount of high-purity (99.999% sigma-aldrich) zinc oxide (zno) and gadolinium oxide (gd2o3) powder have been used for their preparation. for achieving perfect homogeneity, the ingredients were properly pounded for ~8 hours in an agate mortar and pestle. the prepared material has been sintered for ~8h at~550°c and cooled at room temperature. again, the mixture was ground for ~2 hours and sintered for ~6 hours at ~550°c. the mixture was milled for ~4 hours before being turned into pellets. finally, these pellets were sintered for around ~8 hours at about ~600°c. finally, we ground the pellets to make the powder. the powder form of the prepared samples has been used for further characterization. characterization techniques the crystallographic structures of the samples have been explored using an x-ray diffractometer (make: panalytical x'pert pro) using the photon energy of cu kα (λ= 1.5406å). sem images have been used for the morphology study of the synthesized samples. the sem equipment model fig. 8. the gd4dxps spectra for (a) 2% gd-doped zno bulk sample and (b) 5% gd-doped zno bulk sample fig. 9. (a) uv–visible spectra of gd-doped zno (pure zno (gora et al. 2022); gd = 2% and 5%) and tauc plots of the synthesized powder samples: (b) for the zno (gora et al. 2022), (c) for the 2% gd-doped zno and (d) for the 5% gd-doped zno re elements, such as gd, may introduce additional capabilities to the zno system because they may be capable of constructing combined practical devices on a single chip by combining magnetic and optical properties (ohno et al. 1996; tawil et al. 2011). rare-earth (re) metal doping in the dilute magnetic semiconductor (dms) systems has recently received immense attention due to its potential usage in magneto electronic and photonic devices (monteiro et al. 2006). the influence of gd doping on the optical and electrical properties of zno is crucial for developing optoelectronic devices and understanding the genesis of ferromagnetism. ma and wang (2012) synthesized the gd-doped zno nanocrystals using the thermal evaporation deposition method. according to their findings, gd doping has an appreciable impact on the optical characteristics of the zno. the strong uv and blue emissions are detected at low gd concentrations because gd impurities introduce a mid-gap state into zno. in comparison, the uv and blue emissions reduce for high doping concentrations as a significant broad defect emission appears because of the vast numbers of defects, impurities, and excess gd2o3 produced. gd-doped zno nanocrystals can be used in optoelectronic devices. the optical and electrical tuning of the carrier density and optical band gap energy is essential for developing luminescent materials and equipment based on the zno dms systems. the optical band gap and carrier concentration are essential parameters to yield information about the emission wavelength. several development characteristics, like the synthesis methods, impurity concentration and substrate variety have been reported to influence these parameters (wakano et al. 2001; tan et al. 2011; murtaza et al. 2011). the synthesis of dms materials with unique optical, photocatalytic and magnetic characteristics seems to be the most promising candidate for the subsequent generation of electronic, optoelectronic and spintronic appliances (kumar and sahare 2014). the low-dimension materials with imperfection-free lattice structures have excellent electrical and magnetic characteristics; purposefully made or accidental structural defects play a significant role in altering their features (li et al. 2016; obeid et al. 2018). thus, the presence of different kinds of cation or anion vacancies and interstitials in zno nanocrystals may change their magnetic properties, photoluminescence, and photocatalytic properties (coey et al. 2005). although certain experimental and theoretical findings based on dft indicate that gd-doped zno exhibits the room temperature ferromagnetism (rtfm) (potzger et al. 2006; aravindh et al. 2014) property, several studies have demonstrated that the rtfm is not present (sambasivam et al. 2015). in addition to their magnetic qualities, the 4f ions eth 30 kv evo-18 carl zeiss, with a tilt of 0° to 60° and a rotation of 360°, has been used for taking sem images.the defect-related states and chemical analysis of the samples have been determined using x-ray photoelectron spectroscopy. a hemispherical analyzer with a 128-channel detector and a monochromated, fully integrated k-alpha small-spot x-ray photoelectron spectrometer system of 180° double focusing is used in xps (thermo scientific made). the uv-visible absorption spectroscopy (model: shimadzu uv-3600 uv-vis-nir spectrophotometer) was used to explore the prepared samples' optical absorption and band gap. the measurements of uv-visible absorption spectra have been taken using the powder form of the samples. pl spectroscopy was used to analyze defect-related states in the prepared samples. photoluminescence spectra have been recorded at room temperature using the fluorescence spectrometer (model: perkin elmer fl 8500). results and discussion xrd analysis fig. 1. depicts the powder xrd patterns of the gd-doped zno (gd = 0%, 2%, and 5%) samples. all the diffraction peaks detected in the zno sample match with the standard jcpds card number (36-1451). this confirms a hexagonal wurtzite crystal structure of the samples. the diffraction peaks were observed at 31.88°, 34.50°, 36.25°, 47.72°, 56.69°, 63.03°, 66.59°, 68.17°, and 69.35°, which are related to the planes (100), (002), (101), (102), (110), (103), (200), (112), and (201), respectively (ganesh et al. 2018; bharathi et al. 2020). further, some additional small peaks have been observed at 28.61°, 33.21°, and 39.14° with increasing gd doping. these secondary peaks representing a crystallite phase have been identified as gd2o3, which is well consistent with earlier reports (das et al. 2012). as shown in fig. 2, the highest intense peak related to the (101) plane shifted slightly higher angles with the increasing concentration of gd doping. the shift is because of the substitution of bigger-sized gd3+ (0.94 å) ions than zn2+ (0.74 å) ions in the hexagonal wurtzite structure. the peak shift may indicate that gd3+ ions have occupied the crystallographic positions of zn2+ ions in the zno host lattice, or itmay be because of the structural strain caused by the formation of internal compressive micro stress (dakhel and el-hilo 2010; kumar et al. 2014; sahu et al. 2017). rietveld refinements have been performed using the full prof programme (shown in fig. 3). the pseudo-voigt function has been used for rietveld refinement of all the samples with the space group p63mc. the estimated lattice parameters have been listed in table i. the lattice parameters are found to decrease with gd doping, similar to those reported in earlier studies (kaur et al. 2016; obeid et al. 2019). the factors like the induced deficiencies (vacancies, interstitial) and the ionic radius of zn and gd ions can be responsible for the observed change (kaur et al. 2016; kumar and thangavel 2017). sem analysis scanning electron micrographs have been used to analyze the morphology of the gd-doped zno powder samples. the sem images reveal a rod-like morphology in pure zno (gora et al. 2022) and the gd-doped zno polycrystalline samples with some proof of agglomeration and phase segregation, as depicted in fig. 4 (a, b and c). profound observation of the particles exhibits that the crystallite size is above 100 nm. the particles were intensive and incompatibly distributed all over the mass. a distinct boundary between neighbouring crystallites can be noticed, despite the proximity of these smaller crystallites. xps analysis the xps technique is an excellent tool for determining the surface chemistry and electron configuration of the various elements present in a multicomponent material. the carbon c1s peak (284.6 ev) has been used as a reference to calibrate all the binding energies of the spectra. the survey spectrum of the gd-doped zno samples is shown in fig. 5. the survey spectra revealed the existence of o, zn, and gd elements without any impurity in the samples. for zno and 2% gd-doped zno powder samples, the binding energies of the zn2p3/2 and zn2p1/2 peaks are found to be 1021.25 ev, 1044.25 ev, 1021.43 ev, and 1044.43 ev, respectively. however, for the 5% gd-doped zno sample, these peaks are at 1021.83 and 1044.83 ev energy positions. the small shift could be assigned to the creation of zn interstitials in zno upon gd doping. the binding energy gap between the zinc doublet peaks has been found at about 23 ev. this indicates that zn in the zno crystal structure is in the zn2+ oxidation state (khataee et al. 2015; gawai et al. 2019) as the spin-orbital splitting of zn2p is 23 ev. this difference does not change with the gd doping pointing out that gd doping has no discernible effect on the chemical position of zno. the o1s asymmetric xps spectraare shown in fig.7 (a) which is asymmetric in shape. the o1s xps spectra of all these samples i.e. the zno, the zn0.98gd0.02o, and the zn0.95gd0.05o have been deconvoluted mainly into two gaussian peaks, as shown in fig. 7 (b, c, and d). the lower binding peaks for pure and gd-doped zno (gd = 2% and 5%) polycrystalline samples have been detected at 529.93 ev, 529.93 ev and 529.78 ev, respectively, which attributed to the lattice oxygen in the hexagonal structure of the zno. the higher binding peak for the pure and the gd-doped zno samples have been found at 531.51 ev, 531.66 ev, and 531.49 ev, respectively, which is due to the presence of oxygen vacancies in the zno structure (bharathi et al. 2020; sukumaran et al. 2021). an additional signal centered at 528.29 ev has been detected in the 5% gd-doped zno powder sample, which could be ascribed to the coordination of oxygen in gd-o-zn along grain boundaries because of the excessive gd dopants and also attributed to the presence of gd2o3 in the sample (yi et al. 2017). the lattice oxygen peak has slightly shifted to the lower binding energy with increasing gd concentration, which has been due to the increased oxygen vacancies with increasing gd doping. the estimated area ratios of the oxygen vacancies peak and the lattice oxygen peak for the samples zno, zn0.98gd0.02o, and zn0.95gd0.05o comes out to be 0.53, 1.30, and 2.49, respectively. these results show that the oxygen vacancies increase with increasing gd concentration. the fig. 8 (a, b) depicts the high-resolution gd4d xps spectra of the gd-doped samples.in the gd4d state, the spin-orbit splatted peaks are at 144.6 ev for gd4d3/2 and 139.6 ev for gd4d5/2 for the 2% gd-doped sample, whereas for the 5% gd-doped zno sample, the spin-orbit splits at 145.5 ev for gd4d3/2 and 139.7 ev for gd4d5/2 as shown in fig. 8 (a, b). this indicates that gd is present in the gd3+ state in the zno hexagonal structure. the shift in peak values of gd4d3/2 and gd4d5/2 from 144.6 ev and 139.6 ev, respectively; in the case of 2% gd-doped sample to 145.5 ev and 139.7 ev, respectively, in the case of 5% gd-doped sample. this shift in gd4d peaks is ascribed to the electron transfer from plasmonics gd to zno because of the strong electronic interaction (covalent bond) between gd and the oxide (ahmad et al. 2011; wang et al. 2012; bharathi et al. 2020). uv visible spectroscopy analysis the uv–visible spectroscopy is a powerful tool for estimating band gap of materials. uv–vis absorbance spectra and tauc plots for the gd-doped zno samples (gd = 0% (gora et al. 2022), 2%, and 5%) samples are shown in figs.9 (a, b, c, and d). the spectra show a red shift with increasing gd amount in the zno.the uv–vis absorption intensity of the synthesized polycrystalline samples is found to reduce with the increasing gd concentration (mazhdi and tafreshi 2018). tauc's plot has been used to calculate the direct band gap of the samples (jain et al. 2006). the direct band gap has been estimated using the following equation: here, α is the absorption coefficient,υ is frequency, h is the planck constant, a is a constant, and eg is the energy band gap of the substance. extrapolating the linear component of the curve plotted among (αhυ) 2 and hυ depicted in fig. 9 (b, c, and d) has been used to obtain the band gap (farhad et al. 2018; ghos et al. 2021). the band gap values calculated for the gd-doped zno samples, i.e.are 3.31 ev (gora et al. 2022), 3.27 ev, and 3.23ev, for the samples gd = 0%, 2% and 5%, respectively. the small redshift observed in the band gap of gd-doped zno samples is because of the changes in electronic structure as well as enhanced oxygen vacancies with the increasing gd doping (yi et al. 2017; flemban et al. 2016), which is responsible for the band gap reduction. photoluminescence spectroscopy analysis the structural flaws like ionic and atomic vacancies, replacements and interstitials have been explored using the pl spectra of the synthesized polycrystalline samples. fig. 10 (a, b and c) shows the deconvoluted, gaussian-fitted pl spectra of the synthesized gd-doped zno polycrystalline powder samples. the pl spectra of the samples were recorded at room temperature in order to determine the types of vacancies, defect band emission etc. (lin et al. 2001; yi et al. 2017). the photoluminescence spectra have been deconvoluted and the different peaks responsible for the emission have been gaussian fitted. for these samples the band edge emission peaksare detected at 381 nm, 384 nm, and 383 nm, for the gd = 0%, 2% and 5% samples, respectively. the uv emission is responsible for the excitonic interaction related to the band edge emission. the intense violet emission exhibited in the gd-doped zno at about 415 nm could be because ofthe oxygen vacancies. the exciton interaction between the holes in the valence band and electrons located in the interstitial zinc could be responsible for the violet emission peak at about 447 nm. intrinsic deficiencies like interstitial zinc and oxygen can be attributed to the peak at 477 nm (singh et al. 2009; kaur et al. 2016). the transformation between singly ionized oxygen deficiency and the photo-created holes (kennedy et al. 2014) or the surface imperfection and electrons near the conduction band, might be responsible for the green emission peak seen for the gd-doped znoat around 525 nm. the green emissions are commonly attributed to theoxygen vacancies (studenikin et al. 1998). for gd-doped zno polycrystalline powder samples, the intensity ratio of the green and ultra-violet emission peaks is found to be 0.090 for zno, 0.204 for the 2% gd-doped zno, and 0.418 for the 5% gd-doped zno. the defect-related emissions enhanced with increasing gd doping in the zno indicate that a large number of deficiencies, such as oxygen vacancies, are most usually related to crystal deformation (yi et al. 2017). the results reveal that the gd doping enhances the zni and vo flaws. it could be attributed to structural deformation created by gd atoms with different ionic sizes than zn in the zno (bandopadhyay and mitra 2015; sukumaran et al. 2021). increasing gd doping in zno indicates an increase in defect states, which matches well with the xps results. we compared our pl results with farhad et al. (2019), who prepared zno dc (drop casting) and zno nanorods. their pl results detected the pl peak at 380 nm and a barely observable green-yellow emission peak; in our case, we find it at 381 nm for zno, 384 nm for 2% gd-doped zno and 383 nm for the 5% gd-doped zno polycrystalline sample. this peak represented zno's near band edge (nbe) transition because of free excitons recombinations and this pl property indicates high crystalline quality. the luminescent characteristics in the visible region are responsible for the different defects, like zinc interstitials (zni), oxygen vacancies (vo), etc., present in the zno crystal matrix. as a result, they reported that both zno (dc) and zno nanorods were found to be defect-free good crystalline and optical properties materials. in our case, all the prepared gd-doped zno powder samples have been found to be with single ionized oxygen vacancies, which are confirmed by the green emission peak at 525 nm in the pl spectra. conclusion the gd-doped zno powder samples were synthesized by the solid-state reaction method. the xrd patterns affirm that gd has been successfully incorporated into the zno lattice and confirm the hexagonal wurtzite structure. sem images have been used to reveal the morphologies of the synthesized samples, which appear as rod-like structures. the xps results showed that the oxygen vacancy-related states in gd-doped samples increased with increasing gd doping. pl findings confirmed that the defect-related states are present in the gd-doped zno polycrystalline samples. the green emission and ultra-violet emission peaks' intensity ratio is 0.418 for the 5% gd-doped zno sample, which is the maximum compared to the pure zno and 2% gd-doped zno polycrystalline powder sample. these findings confirmed that the oxygen vacancies increase as the gd concentration increases and the pl results agree well with the xps results. the uv absorption spectra findings reveal that the band gap in the 5% gd-doped zno sample is found to be 3.23 ev, which is the minimum compared to both the pure zno and the 2% gd-doped zno samples, confirming that eg is reduced with increasing gd concentration. acknowledgment the authors are thankful to usic, university of rajasthan, jaipur, rajasthan (india), for providing sem images of the prepared samples. we also thank department of physics, banasthalividhyapith, banasthali, jaipur, rajasthan (india) for rendering xrd data. funding sources this research is not financed by any agency. authors' contribution sample preparation, data analysis, manuscript composition and writing (mahendra kumar gora); 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by plasma-assisted molecular-beam epitaxy, journal of crystal growth. 323: 351-354. https://doi.org/10. 1016/j.jcrysgro.2010.11.166 thangeeswari t, murugasen p and velmurugan j (2015), influence of co and dy doping on the optical and magnetic properties of zno nanoparticles for dms application, j. supercond. nov. magn. 28: 2505-2515. https://doi.org/10.1007/s10948-015-3045-2 wakano t, fujimura n, morinaga y, abe n, ashida a and ito t (2001), magnetic and magneto-transport properties of zno: ni films, physica e: low-dimensional systems and nanostructures. 10: 260-264. doi:10. 1016/s1386-9477(01)00095-9 wang xj, wang w and liu yl (2012), enhanced acetone sensing performance of au nanoparticles functionalized flower-like zno, sensors actuators b: chemical. 168: 39-45. https://doi.org/10.1016/j.snb.2012.01.006 yi xy, ma cy, yuan f, wang n, qin fw, hu bc and zhang qy (2017), structural, morphological, photoluminescence and photocatalytic properties of gd doped zno films, thin solid films. 636: 339-345. https://doi.org/10.1016/j.tsf.2017.05.020 doped zno nanocrystals also have an attractive optical responsiveness. many theoretical and experimental studies showed that re-doped zno could reportedly absorb ultraviolet (uv) light (chakraborty et al. 2017). obeid et al. (2019) prepared undoped and gd-doped zno nanocrystalline samples using the thermal decomposition method. they observed that the optical absorption spectra of pristine zno increased with a 6% gd doping concentration and the magnetic properties changed with changing dopant amounts. their pl spectroscopy results showed the existence of defects, which increased with increasing gd doping concentrations. they suggested that these dms nanoparticles can be used for magneto-optoelectronic practical device applications. undoubtedly, the re-doped zno nanostructures have been intensively studied recently because this is a rapidly growing field due to their multi-functionality and their use in possible new generation applications. with an aim to understand the effect of gd doping in zno in terms of its electronic and optical properties we have synthesize gd-doped zno powder series of different gd (0%, 2%, and 5%) values. various characterization techniques have been utilized to explore the electronic, structural and optical features of the synthesized powder series. gd doping into zno produced changes in the band gap and enhanced oxygen vacancies related states in the compound. materials and methods the gd-doped zno powder samples with varying gd (0%, 2%, and 5%) concentrations have been synthesized using the conventional solid-state reaction method. a suitable amount of high-purity (99.999% sigma-aldrich) zinc oxide (zno) and gadolinium oxide (gd2o3) powder have been used for their preparation. for achieving perfect homogeneity, the ingredients were properly pounded for ~8 hours in an agate mortar and pestle. the prepared material has been sintered for ~8h at~550°c and cooled at room temperature. again, the mixture was ground for ~2 hours and sintered for ~6 hours at ~550°c. the mixture was milled for ~4 hours before being turned into pellets. finally, these pellets were sintered for around ~8 hours at about ~600°c. finally, we ground the pellets to make the powder. the powder form of the prepared samples has been used for further characterization. characterization techniques the crystallographic structures of the samples have been explored using an x-ray diffractometer (make: panalytical x'pert pro) using the photon energy of cu kα (λ= 1.5406å). sem images have been used for the morphology study of the synthesized samples. the sem equipment model fig. 10. pl spectra: (a) for zno (gora et al., 2022), (b) for 2% gd-doped zno (c) for 5% gd-doped zno powder sample re elements, such as gd, may introduce additional capabilities to the zno system because they may be capable of constructing combined practical devices on a single chip by combining magnetic and optical properties (ohno et al. 1996; tawil et al. 2011). rare-earth (re) metal doping in the dilute magnetic semiconductor (dms) systems has recently received immense attention due to its potential usage in magneto electronic and photonic devices (monteiro et al. 2006). the influence of gd doping on the optical and electrical properties of zno is crucial for developing optoelectronic devices and understanding the genesis of ferromagnetism. ma and wang (2012) synthesized the gd-doped zno nanocrystals using the thermal evaporation deposition method. according to their findings, gd doping has an appreciable impact on the optical characteristics of the zno. the strong uv and blue emissions are detected at low gd concentrations because gd impurities introduce a mid-gap state into zno. in comparison, the uv and blue emissions reduce for high doping concentrations as a significant broad defect emission appears because of the vast numbers of defects, impurities, and excess gd2o3 produced. gd-doped zno nanocrystals can be used in optoelectronic devices. the optical and electrical tuning of the carrier density and optical band gap energy is essential for developing luminescent materials and equipment based on the zno dms systems. the optical band gap and carrier concentration are essential parameters to yield information about the emission wavelength. several development characteristics, like the synthesis methods, impurity concentration and substrate variety have been reported to influence these parameters (wakano et al. 2001; tan et al. 2011; murtaza et al. 2011). the synthesis of dms materials with unique optical, photocatalytic and magnetic characteristics seems to be the most promising candidate for the subsequent generation of electronic, optoelectronic and spintronic appliances (kumar and sahare 2014). the low-dimension materials with imperfection-free lattice structures have excellent electrical and magnetic characteristics; purposefully made or accidental structural defects play a significant role in altering their features (li et al. 2016; obeid et al. 2018). thus, the presence of different kinds of cation or anion vacancies and interstitials in zno nanocrystals may change their magnetic properties, photoluminescence, and photocatalytic properties (coey et al. 2005). although certain experimental and theoretical findings based on dft indicate that gd-doped zno exhibits the room temperature ferromagnetism (rtfm) (potzger et al. 2006; aravindh et al. 2014) property, several studies have demonstrated that the rtfm is not present (sambasivam et al. 2015). in addition to their magnetic qualities, the 4f ions eth 30 kv evo-18 carl zeiss, with a tilt of 0° to 60° and a rotation of 360°, has been used for taking sem images.the defect-related states and chemical analysis of the samples have been determined using x-ray photoelectron spectroscopy. a hemispherical analyzer with a 128-channel detector and a monochromated, fully integrated k-alpha small-spot x-ray photoelectron spectrometer system of 180° double focusing is used in xps (thermo scientific made). the uv-visible absorption spectroscopy (model: shimadzu uv-3600 uv-vis-nir spectrophotometer) was used to explore the prepared samples' optical absorption and band gap. the measurements of uv-visible absorption spectra have been taken using the powder form of the samples. pl spectroscopy was used to analyze defect-related states in the prepared samples. photoluminescence spectra have been recorded at room temperature using the fluorescence spectrometer (model: perkin elmer fl 8500). results and discussion xrd analysis fig. 1. depicts the powder xrd patterns of the gd-doped zno (gd = 0%, 2%, and 5%) samples. all the diffraction peaks detected in the zno sample match with the standard jcpds card number (36-1451). this confirms a hexagonal wurtzite crystal structure of the samples. the diffraction peaks were observed at 31.88°, 34.50°, 36.25°, 47.72°, 56.69°, 63.03°, 66.59°, 68.17°, and 69.35°, which are related to the planes (100), (002), (101), (102), (110), (103), (200), (112), and (201), respectively (ganesh et al. 2018; bharathi et al. 2020). further, some additional small peaks have been observed at 28.61°, 33.21°, and 39.14° with increasing gd doping. these secondary peaks representing a crystallite phase have been identified as gd2o3, which is well consistent with earlier reports (das et al. 2012). as shown in fig. 2, the highest intense peak related to the (101) plane shifted slightly higher angles with the increasing concentration of gd doping. the shift is because of the substitution of bigger-sized gd3+ (0.94 å) ions than zn2+ (0.74 å) ions in the hexagonal wurtzite structure. the peak shift may indicate that gd3+ ions have occupied the crystallographic positions of zn2+ ions in the zno host lattice, or itmay be because of the structural strain caused by the formation of internal compressive micro stress (dakhel and el-hilo 2010; kumar et al. 2014; sahu et al. 2017). rietveld refinements have been performed using the full prof programme (shown in fig. 3). the pseudo-voigt function has been used for rietveld refinement of all the samples with the space group p63mc. the estimated lattice parameters have been listed in table i. the lattice parameters are found to decrease with gd doping, similar to those reported in earlier studies (kaur et al. 2016; obeid et al. 2019). the factors like the induced deficiencies (vacancies, interstitial) and the ionic radius of zn and gd ions can be responsible for the observed change (kaur et al. 2016; kumar and thangavel 2017). sem analysis scanning electron micrographs have been used to analyze the morphology of the gd-doped zno powder samples. the sem images reveal a rod-like morphology in pure zno (gora et al. 2022) and the gd-doped zno polycrystalline samples with some proof of agglomeration and phase segregation, as depicted in fig. 4 (a, b and c). profound observation of the particles exhibits that the crystallite size is above 100 nm. the particles were intensive and incompatibly distributed all over the mass. a distinct boundary between neighbouring crystallites can be noticed, despite the proximity of these smaller crystallites. xps analysis the xps technique is an excellent tool for determining the surface chemistry and electron configuration of the various elements present in a multicomponent material. the carbon c1s peak (284.6 ev) has been used as a reference to calibrate all the binding energies of the spectra. the survey spectrum of the gd-doped zno samples is shown in fig. 5. the survey spectra revealed the existence of o, zn, and gd elements without any impurity in the samples. for zno and 2% gd-doped zno powder samples, the binding energies of the zn2p3/2 and zn2p1/2 peaks are found to be 1021.25 ev, 1044.25 ev, 1021.43 ev, and 1044.43 ev, respectively. however, for the 5% gd-doped zno sample, these peaks are at 1021.83 and 1044.83 ev energy positions. the small shift could be assigned to the creation of zn interstitials in zno upon gd doping. the binding energy gap between the zinc doublet peaks has been found at about 23 ev. this indicates that zn in the zno crystal structure is in the zn2+ oxidation state (khataee et al. 2015; gawai et al. 2019) as the spin-orbital splitting of zn2p is 23 ev. this difference does not change with the gd doping pointing out that gd doping has no discernible effect on the chemical position of zno. the o1s asymmetric xps spectraare shown in fig.7 (a) which is asymmetric in shape. the o1s xps spectra of all these samples i.e. the zno, the zn0.98gd0.02o, and the zn0.95gd0.05o have been deconvoluted mainly into two gaussian peaks, as shown in fig. 7 (b, c, and d). the lower binding peaks for pure and gd-doped zno (gd = 2% and 5%) polycrystalline samples have been detected at 529.93 ev, 529.93 ev and 529.78 ev, respectively, which attributed to the lattice oxygen in the hexagonal structure of the zno. the higher binding peak for the pure and the gd-doped zno samples have been found at 531.51 ev, 531.66 ev, and 531.49 ev, respectively, which is due to the presence of oxygen vacancies in the zno structure (bharathi et al. 2020; sukumaran et al. 2021). an additional signal centered at 528.29 ev has been detected in the 5% gd-doped zno powder sample, which could be ascribed to the coordination of oxygen in gd-o-zn along grain boundaries because of the excessive gd dopants and also attributed to the presence of gd2o3 in the sample (yi et al. 2017). the lattice oxygen peak has slightly shifted to the lower binding energy with increasing gd concentration, which has been due to the increased oxygen vacancies with increasing gd doping. the estimated area ratios of the oxygen vacancies peak and the lattice oxygen peak for the samples zno, zn0.98gd0.02o, and zn0.95gd0.05o comes out to be 0.53, 1.30, and 2.49, respectively. these results show that the oxygen vacancies increase with increasing gd concentration. the fig. 8 (a, b) depicts the high-resolution gd4d xps spectra of the gd-doped samples.in the gd4d state, the spin-orbit splatted peaks are at 144.6 ev for gd4d3/2 and 139.6 ev for gd4d5/2 for the 2% gd-doped sample, whereas for the 5% gd-doped zno sample, the spin-orbit splits at 145.5 ev for gd4d3/2 and 139.7 ev for gd4d5/2 as shown in fig. 8 (a, b). this indicates that gd is present in the gd3+ state in the zno hexagonal structure. the shift in peak values of gd4d3/2 and gd4d5/2 from 144.6 ev and 139.6 ev, respectively; in the case of 2% gd-doped sample to 145.5 ev and 139.7 ev, respectively, in the case of 5% gd-doped sample. this shift in gd4d peaks is ascribed to the electron transfer from plasmonics gd to zno because of the strong electronic interaction (covalent bond) between gd and the oxide (ahmad et al. 2011; wang et al. 2012; bharathi et al. 2020). uv visible spectroscopy analysis the uv–visible spectroscopy is a powerful tool for estimating band gap of materials. uv–vis absorbance spectra and tauc plots for the gd-doped zno samples (gd = 0% (gora et al. 2022), 2%, and 5%) samples are shown in figs.9 (a, b, c, and d). the spectra show a red shift with increasing gd amount in the zno.the uv–vis absorption intensity of the synthesized polycrystalline samples is found to reduce with the increasing gd concentration (mazhdi and tafreshi 2018). tauc's plot has been used to calculate the direct band gap of the samples (jain et al. 2006). the direct band gap has been estimated using the following equation: here, α is the absorption coefficient,υ is frequency, h is the planck constant, a is a constant, and eg is the energy band gap of the substance. extrapolating the linear component of the curve plotted among (αhυ) 2 and hυ depicted in fig. 9 (b, c, and d) has been used to obtain the band gap (farhad et al. 2018; ghos et al. 2021). the band gap values calculated for the gd-doped zno samples, i.e.are 3.31 ev (gora et al. 2022), 3.27 ev, and 3.23ev, for the samples gd = 0%, 2% and 5%, respectively. the small redshift observed in the band gap of gd-doped zno samples is because of the changes in electronic structure as well as enhanced oxygen vacancies with the increasing gd doping (yi et al. 2017; flemban et al. 2016), which is responsible for the band gap reduction. photoluminescence spectroscopy analysis the structural flaws like ionic and atomic vacancies, replacements and interstitials have been explored using the pl spectra of the synthesized polycrystalline samples. fig. 10 (a, b and c) shows the deconvoluted, gaussian-fitted pl spectra of the synthesized gd-doped zno polycrystalline powder samples. the pl spectra of the samples were recorded at room temperature in order to determine the types of vacancies, defect band emission etc. (lin et al. 2001; yi et al. 2017). the photoluminescence spectra have been deconvoluted and the different peaks responsible for the emission have been gaussian fitted. for these samples the band edge emission peaksare detected at 381 nm, 384 nm, and 383 nm, for the gd = 0%, 2% and 5% samples, respectively. the uv emission is responsible for the excitonic interaction related to the band edge emission. the intense violet emission exhibited in the gd-doped zno at about 415 nm could be because ofthe oxygen vacancies. the exciton interaction between the holes in the valence band and electrons located in the interstitial zinc could be responsible for the violet emission peak at about 447 nm. intrinsic deficiencies like interstitial zinc and oxygen can be attributed to the peak at 477 nm (singh et al. 2009; kaur et al. 2016). the transformation between singly ionized oxygen deficiency and the photo-created holes (kennedy et al. 2014) or the surface imperfection and electrons near the conduction band, might be responsible for the green emission peak seen for the gd-doped znoat around 525 nm. the green emissions are commonly attributed to theoxygen vacancies (studenikin et al. 1998). for gd-doped zno polycrystalline powder samples, the intensity ratio of the green and ultra-violet emission peaks is found to be 0.090 for zno, 0.204 for the 2% gd-doped zno, and 0.418 for the 5% gd-doped zno. the defect-related emissions enhanced with increasing gd doping in the zno indicate that a large number of deficiencies, such as oxygen vacancies, are most usually related to crystal deformation (yi et al. 2017). the results reveal that the gd doping enhances the zni and vo flaws. it could be attributed to structural deformation created by gd atoms with different ionic sizes than zn in the zno (bandopadhyay and mitra 2015; sukumaran et al. 2021). increasing gd doping in zno indicates an increase in defect states, which matches well with the xps results. we compared our pl results with farhad et al. (2019), who prepared zno dc (drop casting) and zno nanorods. their pl results detected the pl peak at 380 nm and a barely observable green-yellow emission peak; in our case, we find it at 381 nm for zno, 384 nm for 2% gd-doped zno and 383 nm for the 5% gd-doped zno polycrystalline sample. this peak represented zno's near band edge (nbe) transition because of free excitons recombinations and this pl property indicates high crystalline quality. the luminescent characteristics in the visible region are responsible for the different defects, like zinc interstitials (zni), oxygen vacancies (vo), etc., present in the zno crystal matrix. as a result, they reported that both zno (dc) and zno nanorods were found to be defect-free good crystalline and optical properties materials. in our case, all the prepared gd-doped zno powder samples have been found to be with single ionized oxygen vacancies, which are confirmed by the green emission peak at 525 nm in the pl spectra. conclusion the gd-doped zno powder samples were synthesized by the solid-state reaction method. the xrd patterns affirm that gd has been successfully incorporated into the zno lattice and confirm the hexagonal wurtzite structure. sem images have been used to reveal the morphologies of the synthesized samples, which appear as rod-like structures. the xps results showed that the oxygen vacancy-related states in gd-doped samples increased with increasing gd doping. pl findings confirmed that the defect-related states are present in the gd-doped zno polycrystalline samples. the green emission and ultra-violet emission peaks' intensity ratio is 0.418 for the 5% gd-doped zno sample, which is the maximum compared to the pure zno and 2% gd-doped zno polycrystalline powder sample. these findings confirmed that the oxygen vacancies increase as the gd concentration increases and the pl results agree well with the xps results. the uv absorption spectra findings reveal that the band gap in the 5% gd-doped zno sample is found to be 3.23 ev, which is the minimum compared to both the pure zno and the 2% gd-doped zno samples, confirming that eg is reduced with increasing gd concentration. acknowledgment the authors are thankful to usic, university of rajasthan, jaipur, rajasthan (india), for providing sem images of the prepared samples. we also thank department of physics, banasthalividhyapith, banasthali, jaipur, rajasthan (india) for rendering xrd data. funding sources this research is not financed by any agency. authors' contribution sample preparation, data analysis, manuscript composition and writing (mahendra kumar gora); 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0 0) by evaporation technique, j.magn. magn. mater. 323: 3239-3245. https://doi. org/10.1016/j.jmmm. 2011.07.021 obeid mm, jappor hr, almarzoki k, al-hydary ia, edrees sj and shukur mm (2019), unraveling the effect of gd doping on the structural, optical, and magnetic properties of zno based diluted magnetic semiconductor nanorods, rsc adv. 9: 33207-33221. doi: 10.1039/ c9ra04750f obeid mm, mogulkoc y, edress sj, ciftci yo, shukur mm and al-marzooqee mmh (2018), analysis of the structural, electronic, elastic and thermodynamic properties of cual2x4 (x = o, s) spinel structure, mater. res. bull. 108: 255-265. https://doi.org/10.1016/j.materresbull.2018.09.013 ohno h, shen a, matsukura f, oiwa a, endo a, katsumoto s and iye y (1996), (ga, mn) as: a new diluted magnetic semiconductor based on gaas, applied physics letters. 69: 363-365. https://doi.org/10.1063/1.118061 ozgür u, alivov yi, liu c, teke a, reshchikov ma, dogan s, avrutin v, cho sj and morkoc h (2005), a comprehensive review 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http://dx.doi.org/ 10.1007/ s00339-014 8822-4 singh ak, viswanath v and janu vc (2009), synthesis, effect of capping agents, structural, optical and photoluminescence properties of zno nanoparticles, j. lumin. 129: 874-878. https://doi.org/ 10.1016/j.jlumin.2009.03.027 studenikin sa, golego n and cocivera m (1998), fabrication of green and photoluminescent, undoped zno films using spray pyrolysis, j. appl. phys. 84: 2287-2294. https://doi.org/10.1063/1.368295 sukumaran a, sivanantham n, vinoth e and gopalakrishnan n (2021), ferromagnetism in gd-doped zno thin films mediated by defects, bull. mater. sci. 44: 259. http://dx.doi.org/ 10.1007/s12034-021-02550-y tan y, fang z, chen w and he p (2011),structural, optical and magnetic properties of eu-doped zno films,j. alloys compd. 509: 6321-6324. https://doi.org/ 10.1016/j.jallcom.2011.03.084 tawil snm, krishnamurthy d, kakimi r, emura s, hasegawa s and ashi h (2011), studies on the ingagdn/gan magnetic semiconductor heterostructures grown by plasma-assisted molecular-beam epitaxy, journal of crystal growth. 323: 351-354. https://doi.org/10. 1016/j.jcrysgro.2010.11.166 thangeeswari t, murugasen p and velmurugan j (2015), influence of co and dy doping on the optical and magnetic properties of zno nanoparticles for dms application, j. supercond. nov. magn. 28: 2505-2515. https://doi.org/10.1007/s10948-015-3045-2 wakano t, fujimura n, morinaga y, abe n, ashida a and ito t (2001), magnetic and magneto-transport properties of zno: ni films, physica e: low-dimensional systems and nanostructures. 10: 260-264. doi:10. 1016/s1386-9477(01)00095-9 wang xj, wang w and liu yl (2012), enhanced acetone sensing performance of au nanoparticles functionalized flower-like zno, sensors actuators b: chemical. 168: 39-45. https://doi.org/10.1016/j.snb.2012.01.006 yi xy, ma cy, yuan f, wang n, qin fw, hu bc and zhang qy (2017), structural, morphological, photoluminescence and photocatalytic properties of gd doped zno films, thin solid films. 636: 339-345. https://doi.org/10.1016/j.tsf.2017.05.020 doped zno nanocrystals also have an attractive optical responsiveness. many theoretical and experimental studies showed that re-doped zno could reportedly absorb ultraviolet (uv) light (chakraborty et al. 2017). obeid et al. (2019) prepared undoped and gd-doped zno nanocrystalline samples using the thermal decomposition method. they observed that the optical absorption spectra of pristine zno increased with a 6% gd doping concentration and the magnetic properties changed with changing dopant amounts. their pl spectroscopy results showed the existence of defects, which increased with increasing gd doping concentrations. they suggested that these dms nanoparticles can be used for magneto-optoelectronic practical device applications. undoubtedly, the re-doped zno nanostructures have been intensively studied recently because this is a rapidly growing field due to their multi-functionality and their use in possible new generation applications. with an aim to understand the effect of gd doping in zno in terms of its electronic and optical properties we have synthesize gd-doped zno powder series of different gd (0%, 2%, and 5%) values. various characterization techniques have been utilized to explore the electronic, structural and optical features of the synthesized powder series. gd doping into zno produced changes in the band gap and enhanced oxygen vacancies related states in the compound. materials and methods the gd-doped zno powder samples with varying gd (0%, 2%, and 5%) concentrations have been synthesized using the conventional solid-state reaction method. a suitable amount of high-purity (99.999% sigma-aldrich) zinc oxide (zno) and gadolinium oxide (gd2o3) powder have been used for their preparation. for achieving perfect homogeneity, the ingredients were properly pounded for ~8 hours in an agate mortar and pestle. the prepared material has been sintered for ~8h at~550°c and cooled at room temperature. again, the mixture was ground for ~2 hours and sintered for ~6 hours at ~550°c. the mixture was milled for ~4 hours before being turned into pellets. finally, these pellets were sintered for around ~8 hours at about ~600°c. finally, we ground the pellets to make the powder. the powder form of the prepared samples has been used for further characterization. characterization techniques the crystallographic structures of the samples have been explored using an x-ray diffractometer (make: panalytical x'pert pro) using the photon energy of cu kα (λ= 1.5406å). sem images have been used for the morphology study of the synthesized samples. the sem equipment model re elements, such as gd, may introduce additional capabilities to the zno system because they may be capable of constructing combined practical devices on a single chip by combining magnetic and optical properties (ohno et al. 1996; tawil et al. 2011). rare-earth (re) metal doping in the dilute magnetic semiconductor (dms) systems has recently received immense attention due to its potential usage in magneto electronic and photonic devices (monteiro et al. 2006). the influence of gd doping on the optical and electrical properties of zno is crucial for developing optoelectronic devices and understanding the genesis of ferromagnetism. ma and wang (2012) synthesized the gd-doped zno nanocrystals using the thermal evaporation deposition method. according to their findings, gd doping has an appreciable impact on the optical characteristics of the zno. the strong uv and blue emissions are detected at low gd concentrations because gd impurities introduce a mid-gap state into zno. in comparison, the uv and blue emissions reduce for high doping concentrations as a significant broad defect emission appears because of the vast numbers of defects, impurities, and excess gd2o3 produced. gd-doped zno nanocrystals can be used in optoelectronic devices. the optical and electrical tuning of the carrier density and optical band gap energy is essential for developing luminescent materials and equipment based on the zno dms systems. the optical band gap and carrier concentration are essential parameters to yield information about the emission wavelength. several development characteristics, like the synthesis methods, impurity concentration and substrate variety have been reported to influence these parameters (wakano et al. 2001; tan et al. 2011; murtaza et al. 2011). the synthesis of dms materials with unique optical, photocatalytic and magnetic characteristics seems to be the most promising candidate for the subsequent generation of electronic, optoelectronic and spintronic appliances (kumar and sahare 2014). the low-dimension materials with imperfection-free lattice structures have excellent electrical and magnetic characteristics; purposefully made or accidental structural defects play a significant role in altering their features (li et al. 2016; obeid et al. 2018). thus, the presence of different kinds of cation or anion vacancies and interstitials in zno nanocrystals may change their magnetic properties, photoluminescence, and photocatalytic properties (coey et al. 2005). although certain experimental and theoretical findings based on dft indicate that gd-doped zno exhibits the room temperature ferromagnetism (rtfm) (potzger et al. 2006; aravindh et al. 2014) property, several studies have demonstrated that the rtfm is not present (sambasivam et al. 2015). in addition to their magnetic qualities, the 4f ions eth 30 kv evo-18 carl zeiss, with a tilt of 0° to 60° and a rotation of 360°, has been used for taking sem images.the defect-related states and chemical analysis of the samples have been determined using x-ray photoelectron spectroscopy. a hemispherical analyzer with a 128-channel detector and a monochromated, fully integrated k-alpha small-spot x-ray photoelectron spectrometer system of 180° double focusing is used in xps (thermo scientific made). the uv-visible absorption spectroscopy (model: shimadzu uv-3600 uv-vis-nir spectrophotometer) was used to explore the prepared samples' optical absorption and band gap. the measurements of uv-visible absorption spectra have been taken using the powder form of the samples. pl spectroscopy was used to analyze defect-related states in the prepared samples. photoluminescence spectra have been recorded at room temperature using the fluorescence spectrometer (model: perkin elmer fl 8500). results and discussion xrd analysis fig. 1. depicts the powder xrd patterns of the gd-doped zno (gd = 0%, 2%, and 5%) samples. all the diffraction peaks detected in the zno sample match with the standard jcpds card number (36-1451). this confirms a hexagonal wurtzite crystal structure of the samples. the diffraction peaks were observed at 31.88°, 34.50°, 36.25°, 47.72°, 56.69°, 63.03°, 66.59°, 68.17°, and 69.35°, which are related to the planes (100), (002), (101), (102), (110), (103), (200), (112), and (201), respectively (ganesh et al. 2018; bharathi et al. 2020). further, some additional small peaks have been observed at 28.61°, 33.21°, and 39.14° with increasing gd doping. these secondary peaks representing a crystallite phase have been identified as gd2o3, which is well consistent with earlier reports (das et al. 2012). as shown in fig. 2, the highest intense peak related to the (101) plane shifted slightly higher angles with the increasing concentration of gd doping. the shift is because of the substitution of bigger-sized gd3+ (0.94 å) ions than zn2+ (0.74 å) ions in the hexagonal wurtzite structure. the peak shift may indicate that gd3+ ions have occupied the crystallographic positions of zn2+ ions in the zno host lattice, or itmay be because of the structural strain caused by the formation of internal compressive micro stress (dakhel and el-hilo 2010; kumar et al. 2014; sahu et al. 2017). rietveld refinements have been performed using the full prof programme (shown in fig. 3). the pseudo-voigt function has been used for rietveld refinement of all the samples with the space group p63mc. the estimated lattice parameters have been listed in table i. the lattice parameters are found to decrease with gd doping, similar to those reported in earlier studies (kaur et al. 2016; obeid et al. 2019). the factors like the induced deficiencies (vacancies, interstitial) and the ionic radius of zn and gd ions can be responsible for the observed change (kaur et al. 2016; kumar and thangavel 2017). sem analysis scanning electron micrographs have been used to analyze the morphology of the gd-doped zno powder samples. the sem images reveal a rod-like morphology in pure zno (gora et al. 2022) and the gd-doped zno polycrystalline samples with some proof of agglomeration and phase segregation, as depicted in fig. 4 (a, b and c). profound observation of the particles exhibits that the crystallite size is above 100 nm. the particles were intensive and incompatibly distributed all over the mass. a distinct boundary between neighbouring crystallites can be noticed, despite the proximity of these smaller crystallites. xps analysis the xps technique is an excellent tool for determining the surface chemistry and electron configuration of the various elements present in a multicomponent material. the carbon c1s peak (284.6 ev) has been used as a reference to calibrate all the binding energies of the spectra. the survey spectrum of the gd-doped zno samples is shown in fig. 5. the survey spectra revealed the existence of o, zn, and gd elements without any impurity in the samples. for zno and 2% gd-doped zno powder samples, the binding energies of the zn2p3/2 and zn2p1/2 peaks are found to be 1021.25 ev, 1044.25 ev, 1021.43 ev, and 1044.43 ev, respectively. however, for the 5% gd-doped zno sample, these peaks are at 1021.83 and 1044.83 ev energy positions. the small shift could be assigned to the creation of zn interstitials in zno upon gd doping. the binding energy gap between the zinc doublet peaks has been found at about 23 ev. this indicates that zn in the zno crystal structure is in the zn2+ oxidation state (khataee et al. 2015; gawai et al. 2019) as the spin-orbital splitting of zn2p is 23 ev. this difference does not change with the gd doping pointing out that gd doping has no discernible effect on the chemical position of zno. the o1s asymmetric xps spectraare shown in fig.7 (a) which is asymmetric in shape. the o1s xps spectra of all these samples i.e. the zno, the zn0.98gd0.02o, and the zn0.95gd0.05o have been deconvoluted mainly into two gaussian peaks, as shown in fig. 7 (b, c, and d). the lower binding peaks for pure and gd-doped zno (gd = 2% and 5%) polycrystalline samples have been detected at 529.93 ev, 529.93 ev and 529.78 ev, respectively, which attributed to the lattice oxygen in the hexagonal structure of the zno. the higher binding peak for the pure and the gd-doped zno samples have been found at 531.51 ev, 531.66 ev, and 531.49 ev, respectively, which is due to the presence of oxygen vacancies in the zno structure (bharathi et al. 2020; sukumaran et al. 2021). an additional signal centered at 528.29 ev has been detected in the 5% gd-doped zno powder sample, which could be ascribed to the coordination of oxygen in gd-o-zn along grain boundaries because of the excessive gd dopants and also attributed to the presence of gd2o3 in the sample (yi et al. 2017). the lattice oxygen peak has slightly shifted to the lower binding energy with increasing gd concentration, which has been due to the increased oxygen vacancies with increasing gd doping. the estimated area ratios of the oxygen vacancies peak and the lattice oxygen peak for the samples zno, zn0.98gd0.02o, and zn0.95gd0.05o comes out to be 0.53, 1.30, and 2.49, respectively. these results show that the oxygen vacancies increase with increasing gd concentration. the fig. 8 (a, b) depicts the high-resolution gd4d xps spectra of the gd-doped samples.in the gd4d state, the spin-orbit splatted peaks are at 144.6 ev for gd4d3/2 and 139.6 ev for gd4d5/2 for the 2% gd-doped sample, whereas for the 5% gd-doped zno sample, the spin-orbit splits at 145.5 ev for gd4d3/2 and 139.7 ev for gd4d5/2 as shown in fig. 8 (a, b). this indicates that gd is present in the gd3+ state in the zno hexagonal structure. the shift in peak values of gd4d3/2 and gd4d5/2 from 144.6 ev and 139.6 ev, respectively; in the case of 2% gd-doped sample to 145.5 ev and 139.7 ev, respectively, in the case of 5% gd-doped sample. this shift in gd4d peaks is ascribed to the electron transfer from plasmonics gd to zno because of the strong electronic interaction (covalent bond) between gd and the oxide (ahmad et al. 2011; wang et al. 2012; bharathi et al. 2020). uv visible spectroscopy analysis the uv–visible spectroscopy is a powerful tool for estimating band gap of materials. uv–vis absorbance spectra and tauc plots for the gd-doped zno samples (gd = 0% (gora et al. 2022), 2%, and 5%) samples are shown in figs.9 (a, b, c, and d). the spectra show a red shift with increasing gd amount in the zno.the uv–vis absorption intensity of the synthesized polycrystalline samples is found to reduce with the increasing gd concentration (mazhdi and tafreshi 2018). tauc's plot has been used to calculate the direct band gap of the samples (jain et al. 2006). the direct band gap has been estimated using the following equation: here, α is the absorption coefficient,υ is frequency, h is the planck constant, a is a constant, and eg is the energy band gap of the substance. extrapolating the linear component of the curve plotted among (αhυ) 2 and hυ depicted in fig. 9 (b, c, and d) has been used to obtain the band gap (farhad et al. 2018; ghos et al. 2021). the band gap values calculated for the gd-doped zno samples, i.e.are 3.31 ev (gora et al. 2022), 3.27 ev, and 3.23ev, for the samples gd = 0%, 2% and 5%, respectively. the small redshift observed in the band gap of gd-doped zno samples is because of the changes in electronic structure as well as enhanced oxygen vacancies with the increasing gd doping (yi et al. 2017; flemban et al. 2016), which is responsible for the band gap reduction. photoluminescence spectroscopy analysis the structural flaws like ionic and atomic vacancies, replacements and interstitials have been explored using the pl spectra of the synthesized polycrystalline samples. fig. 10 (a, b and c) shows the deconvoluted, gaussian-fitted pl spectra of the synthesized gd-doped zno polycrystalline powder samples. the pl spectra of the samples were recorded at room temperature in order to determine the types of vacancies, defect band emission etc. (lin et al. 2001; yi et al. 2017). the photoluminescence spectra have been deconvoluted and the different peaks responsible for the emission have been gaussian fitted. for these samples the band edge emission peaksare detected at 381 nm, 384 nm, and 383 nm, for the gd = 0%, 2% and 5% samples, respectively. the uv emission is responsible for the excitonic interaction related to the band edge emission. the intense violet emission exhibited in the gd-doped zno at about 415 nm could be because ofthe oxygen vacancies. the exciton interaction between the holes in the valence band and electrons located in the interstitial zinc could be responsible for the violet emission peak at about 447 nm. intrinsic deficiencies like interstitial zinc and oxygen can be attributed to the peak at 477 nm (singh et al. 2009; kaur et al. 2016). the transformation between singly ionized oxygen deficiency and the photo-created holes (kennedy et al. 2014) or the surface imperfection and electrons near the conduction band, might be responsible for the green emission peak seen for the gd-doped znoat around 525 nm. the green emissions are commonly attributed to theoxygen vacancies (studenikin et al. 1998). for gd-doped zno polycrystalline powder samples, the intensity ratio of the green and ultra-violet emission peaks is found to be 0.090 for zno, 0.204 for the 2% gd-doped zno, and 0.418 for the 5% gd-doped zno. the defect-related emissions enhanced with increasing gd doping in the zno indicate that a large number of deficiencies, such as oxygen vacancies, are most usually related to crystal deformation (yi et al. 2017). the results reveal that the gd doping enhances the zni and vo flaws. it could be attributed to structural deformation created by gd atoms with different ionic sizes than zn in the zno (bandopadhyay and mitra 2015; sukumaran et al. 2021). increasing gd doping in zno indicates an increase in defect states, which matches well with the xps results. we compared our pl results with farhad et al. (2019), who prepared zno dc (drop casting) and zno nanorods. their pl results detected the pl peak at 380 nm and a barely observable green-yellow emission peak; in our case, we find it at 381 nm for zno, 384 nm for 2% gd-doped zno and 383 nm for the 5% gd-doped zno polycrystalline sample. this peak represented zno's near band edge (nbe) transition because of free excitons recombinations and this pl property indicates high crystalline quality. the luminescent characteristics in the visible region are responsible for the different defects, like zinc interstitials (zni), oxygen vacancies (vo), etc., present in the zno crystal matrix. as a result, they reported that both zno (dc) and zno nanorods were found to be defect-free good crystalline and optical properties materials. in our case, all the prepared gd-doped zno powder samples have been found to be with single ionized oxygen vacancies, which are confirmed by the green emission peak at 525 nm in the pl spectra. conclusion the gd-doped zno powder samples were synthesized by the solid-state reaction method. the xrd patterns affirm that gd has been successfully incorporated into the zno lattice and confirm the hexagonal wurtzite structure. sem images have been used to reveal the morphologies of the synthesized samples, which appear as rod-like structures. the xps results showed that the oxygen vacancy-related states in gd-doped samples increased with increasing gd doping. pl findings confirmed that the defect-related states are present in the gd-doped zno polycrystalline samples. the green emission and ultra-violet emission peaks' intensity ratio is 0.418 for the 5% gd-doped zno sample, which is the maximum compared to the pure zno and 2% gd-doped zno polycrystalline powder sample. these findings confirmed that the oxygen vacancies increase as the gd concentration increases and the pl results agree well with the xps results. the uv absorption spectra findings reveal that the band gap in the 5% gd-doped zno sample is found to be 3.23 ev, which is the minimum compared to both the pure zno and the 2% gd-doped zno samples, confirming that eg is reduced with increasing gd concentration. acknowledgment the authors are thankful to usic, university of rajasthan, jaipur, rajasthan (india), for providing sem images of the prepared samples. we also thank department of physics, banasthalividhyapith, banasthali, jaipur, rajasthan (india) for rendering xrd data. funding sources this research is not financed by any agency. authors' contribution sample preparation, data analysis, manuscript composition and writing (mahendra kumar gora); sample synthesis and data characterization (arvind kumar); data recording (banwari lal choudhary); data analysis and interpretation (sanjay kumar); reviewing and editing (satya naraindolia); supervision, writing, reviewing and editing (rishi kumar singhal). conflicts of interest or competing interests all authors declare that we have no conflict of interest or competing interests. data availability on request, data will be available. ethical approval not applicable. references ahmad m, yingying s, nisar a, sun h, shen w, wei m and zhu j (2011), synthesis of hierarchical flower-like zno nanostructures and their functionalization by au nanoparticles for improved photocatalytic and high performance li-ion battery anodes, j. mater. chem. 21: 7723-7729. https://doi.org/10.1039/c1jm10720h aravindh sa, schwingenschloegl u and roqan is (2014), ferromagnetism in gd doped zno nanowires: a first principles study, j. appl. phys. 116: 233-906. https://doi.org/10.1063/1.4904860 bahadur h, srivastava ak, divi h, chander h, basu a, samanta sb, sood kn, kishore r, sharma rk, bhatt v, pal p and chandra s (2007), nano-structured zno films by sol-gel process, indian journal of pure and applied physics. 45: 395-399 bandopadhyay k and mitra j (2015), zn interstitials and o vacancies responsible for n-type zno: what do the emission spectra reveal?, rsc adv. 5: 23540-23547. https://doi.org/10.1039/c5ra00355e bharathi p, mohan mk, shalini v, harish s, navaneethan m, archana j, kumar mg, dhivya p, ponnusamy s, shimomura m and hayakawa y (2020), growth and influence of gd doping on zno nanostructures for enhanced optical, structural properties and gas sensing applications, applied surface science. 499: 143857. https://doi.org/10.1016/j.apsusc.2019.143857 chakraborty a, jong cs, ganguli n and dasgupta i (2017), a comparative study of magnetic and optical properties of mn-, gd-, and nd-doped zno nanowires, int. j. mod. phys. b. 31: 165-241. https://doi.org/10.1142/ s0217979216502416 coey jmd, venkatesan m and fitzgerald c (2005), donor impurity band exchange in dilute ferromagnetic oxides, nat. mater. 4: 173-179. https://doi.org/10.1038/nmat1310 dakhel aa and el-hilo m (2010), ferromagnetic nanocrystallinegd-doped zno powder synthesizedby coprecipitation, journal of applied physics. 107: 123-905. doi: 10.1063/1.3448026 das j, mishra dk, sahu dr and roul bk (2012), structural and magnetic property of mn: zno bulk ceramic doped with rare earth (gd/sm) atoms, physica b: condensed matter. 407: 3575-3579. https://doi.org/ 10.1016/j. physb. 2012.05.028 deshmukh av, patil si, yusuf sm, rajarajan ak and lalla np (2010), structural, chemical and magnetic investigations of polycrystalline zn1-xmnxo, journal of magnetism and magnetic materials. 322: 536-541. https://doi.org/10.1016/j.jmmm.2009.10.011 fan jc, chang sl and xie z (2013), zno-based light-emitting diodes, optoelectronic-advanced materials and devices. 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zinc oxides films deposited on silicon substrates, appl. phys. lett. 79: 943-945. https://doi.org/10.1063/1.1394173 ma x and wang z (2012), the optical properties of rare earth gd doped zno nanocrystals, materials science in semiconductor processing. 15: 227-231. doi:10.1016/ j.mssp.2011.05.013 mazhdi m and tafreshi mj (2018), the effect of gadolinium doping on the structural, morphological, optical, and photoluminescence properties of zinc oxide nanoparticles prepared by co-precipitation method, applied physics a. 124: 863. https://doi.org/10.1007/ s00339 018-2291-0 monteiro t, neves aj, carmo mc, soares mj, peres m, alves e, rita e and wahl u (2006), optical and structural analysis of bulk zno samples undoped and rare earth doped by ion implantation, superlattices and microstructures. 39: 202-210. https://doi.org/10.1016/ j.spmi.2005.08.043 murtaza g, iqbal ma, xu yb, will ig and huang zc (2011), study of sm-doped zno samples sintered in a nitrogen atmosphere and deposited on n-si (1 0 0) by evaporation technique, j.magn. magn. mater. 323: 3239-3245. https://doi. org/10.1016/j.jmmm. 2011.07.021 obeid mm, jappor hr, almarzoki k, al-hydary ia, edrees sj and shukur mm (2019), unraveling the effect of gd doping on the structural, optical, and magnetic properties of zno based diluted magnetic semiconductor nanorods, rsc adv. 9: 33207-33221. doi: 10.1039/ c9ra04750f obeid mm, mogulkoc y, edress sj, ciftci yo, shukur mm and al-marzooqee mmh (2018), analysis of the structural, electronic, elastic and thermodynamic properties of cual2x4 (x = o, s) spinel structure, mater. res. bull. 108: 255-265. https://doi.org/10.1016/j.materresbull.2018.09.013 ohno h, shen a, matsukura f, oiwa a, endo a, katsumoto s and iye y (1996), (ga, mn) as: a new diluted magnetic semiconductor based on gaas, applied physics letters. 69: 363-365. https://doi.org/10.1063/1.118061 ozgür u, alivov yi, liu c, teke a, reshchikov ma, dogan s, avrutin v, cho sj and morkoc h (2005), a comprehensive review 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http://dx.doi.org/ 10.1007/ s00339-014 8822-4 singh ak, viswanath v and janu vc (2009), synthesis, effect of capping agents, structural, optical and photoluminescence properties of zno nanoparticles, j. lumin. 129: 874-878. https://doi.org/ 10.1016/j.jlumin.2009.03.027 studenikin sa, golego n and cocivera m (1998), fabrication of green and photoluminescent, undoped zno films using spray pyrolysis, j. appl. phys. 84: 2287-2294. https://doi.org/10.1063/1.368295 sukumaran a, sivanantham n, vinoth e and gopalakrishnan n (2021), ferromagnetism in gd-doped zno thin films mediated by defects, bull. mater. sci. 44: 259. http://dx.doi.org/ 10.1007/s12034-021-02550-y tan y, fang z, chen w and he p (2011),structural, optical and magnetic properties of eu-doped zno films,j. alloys compd. 509: 6321-6324. https://doi.org/ 10.1016/j.jallcom.2011.03.084 tawil snm, krishnamurthy d, kakimi r, emura s, hasegawa s and ashi h (2011), studies on the ingagdn/gan magnetic semiconductor heterostructures grown by plasma-assisted molecular-beam epitaxy, journal of crystal growth. 323: 351-354. https://doi.org/10. 1016/j.jcrysgro.2010.11.166 thangeeswari t, murugasen p and velmurugan j (2015), influence of co and dy doping on the optical and magnetic properties of zno nanoparticles for dms application, j. supercond. nov. magn. 28: 2505-2515. https://doi.org/10.1007/s10948-015-3045-2 wakano t, fujimura n, morinaga y, abe n, ashida a and ito t (2001), magnetic and magneto-transport properties of zno: ni films, physica e: low-dimensional systems and nanostructures. 10: 260-264. doi:10. 1016/s1386-9477(01)00095-9 wang xj, wang w and liu yl (2012), enhanced acetone sensing performance of au nanoparticles functionalized flower-like zno, sensors actuators b: chemical. 168: 39-45. https://doi.org/10.1016/j.snb.2012.01.006 yi xy, ma cy, yuan f, wang n, qin fw, hu bc and zhang qy (2017), structural, morphological, photoluminescence and photocatalytic properties of gd doped zno films, thin solid films. 636: 339-345. https://doi.org/10.1016/j.tsf.2017.05.020 doped zno nanocrystals also have an attractive optical responsiveness. many theoretical and experimental studies showed that re-doped zno could reportedly absorb ultraviolet (uv) light (chakraborty et al. 2017). obeid et al. (2019) prepared undoped and gd-doped zno nanocrystalline samples using the thermal decomposition method. they observed that the optical absorption spectra of pristine zno increased with a 6% gd doping concentration and the magnetic properties changed with changing dopant amounts. their pl spectroscopy results showed the existence of defects, which increased with increasing gd doping concentrations. they suggested that these dms nanoparticles can be used for magneto-optoelectronic practical device applications. undoubtedly, the re-doped zno nanostructures have been intensively studied recently because this is a rapidly growing field due to their multi-functionality and their use in possible new generation applications. with an aim to understand the effect of gd doping in zno in terms of its electronic and optical properties we have synthesize gd-doped zno powder series of different gd (0%, 2%, and 5%) values. various characterization techniques have been utilized to explore the electronic, structural and optical features of the synthesized powder series. gd doping into zno produced changes in the band gap and enhanced oxygen vacancies related states in the compound. materials and methods the gd-doped zno powder samples with varying gd (0%, 2%, and 5%) concentrations have been synthesized using the conventional solid-state reaction method. a suitable amount of high-purity (99.999% sigma-aldrich) zinc oxide (zno) and gadolinium oxide (gd2o3) powder have been used for their preparation. for achieving perfect homogeneity, the ingredients were properly pounded for ~8 hours in an agate mortar and pestle. the prepared material has been sintered for ~8h at~550°c and cooled at room temperature. again, the mixture was ground for ~2 hours and sintered for ~6 hours at ~550°c. the mixture was milled for ~4 hours before being turned into pellets. finally, these pellets were sintered for around ~8 hours at about ~600°c. finally, we ground the pellets to make the powder. the powder form of the prepared samples has been used for further characterization. characterization techniques the crystallographic structures of the samples have been explored using an x-ray diffractometer (make: panalytical x'pert pro) using the photon energy of cu kα (λ= 1.5406å). sem images have been used for the morphology study of the synthesized samples. the sem equipment model re elements, such as gd, may introduce additional capabilities to the zno system because they may be capable of constructing combined practical devices on a single chip by combining magnetic and optical properties (ohno et al. 1996; tawil et al. 2011). rare-earth (re) metal doping in the dilute magnetic semiconductor (dms) systems has recently received immense attention due to its potential usage in magneto electronic and photonic devices (monteiro et al. 2006). the influence of gd doping on the optical and electrical properties of zno is crucial for developing optoelectronic devices and understanding the genesis of ferromagnetism. ma and wang (2012) synthesized the gd-doped zno nanocrystals using the thermal evaporation deposition method. according to their findings, gd doping has an appreciable impact on the optical characteristics of the zno. the strong uv and blue emissions are detected at low gd concentrations because gd impurities introduce a mid-gap state into zno. in comparison, the uv and blue emissions reduce for high doping concentrations as a significant broad defect emission appears because of the vast numbers of defects, impurities, and excess gd2o3 produced. gd-doped zno nanocrystals can be used in optoelectronic devices. the optical and electrical tuning of the carrier density and optical band gap energy is essential for developing luminescent materials and equipment based on the zno dms systems. the optical band gap and carrier concentration are essential parameters to yield information about the emission wavelength. several development characteristics, like the synthesis methods, impurity concentration and substrate variety have been reported to influence these parameters (wakano et al. 2001; tan et al. 2011; murtaza et al. 2011). the synthesis of dms materials with unique optical, photocatalytic and magnetic characteristics seems to be the most promising candidate for the subsequent generation of electronic, optoelectronic and spintronic appliances (kumar and sahare 2014). the low-dimension materials with imperfection-free lattice structures have excellent electrical and magnetic characteristics; purposefully made or accidental structural defects play a significant role in altering their features (li et al. 2016; obeid et al. 2018). thus, the presence of different kinds of cation or anion vacancies and interstitials in zno nanocrystals may change their magnetic properties, photoluminescence, and photocatalytic properties (coey et al. 2005). although certain experimental and theoretical findings based on dft indicate that gd-doped zno exhibits the room temperature ferromagnetism (rtfm) (potzger et al. 2006; aravindh et al. 2014) property, several studies have demonstrated that the rtfm is not present (sambasivam et al. 2015). in addition to their magnetic qualities, the 4f ions eth 30 kv evo-18 carl zeiss, with a tilt of 0° to 60° and a rotation of 360°, has been used for taking sem images.the defect-related states and chemical analysis of the samples have been determined using x-ray photoelectron spectroscopy. a hemispherical analyzer with a 128-channel detector and a monochromated, fully integrated k-alpha small-spot x-ray photoelectron spectrometer system of 180° double focusing is used in xps (thermo scientific made). the uv-visible absorption spectroscopy (model: shimadzu uv-3600 uv-vis-nir spectrophotometer) was used to explore the prepared samples' optical absorption and band gap. the measurements of uv-visible absorption spectra have been taken using the powder form of the samples. pl spectroscopy was used to analyze defect-related states in the prepared samples. photoluminescence spectra have been recorded at room temperature using the fluorescence spectrometer (model: perkin elmer fl 8500). results and discussion xrd analysis fig. 1. depicts the powder xrd patterns of the gd-doped zno (gd = 0%, 2%, and 5%) samples. all the diffraction peaks detected in the zno sample match with the standard jcpds card number (36-1451). this confirms a hexagonal wurtzite crystal structure of the samples. the diffraction peaks were observed at 31.88°, 34.50°, 36.25°, 47.72°, 56.69°, 63.03°, 66.59°, 68.17°, and 69.35°, which are related to the planes (100), (002), (101), (102), (110), (103), (200), (112), and (201), respectively (ganesh et al. 2018; bharathi et al. 2020). further, some additional small peaks have been observed at 28.61°, 33.21°, and 39.14° with increasing gd doping. these secondary peaks representing a crystallite phase have been identified as gd2o3, which is well consistent with earlier reports (das et al. 2012). as shown in fig. 2, the highest intense peak related to the (101) plane shifted slightly higher angles with the increasing concentration of gd doping. the shift is because of the substitution of bigger-sized gd3+ (0.94 å) ions than zn2+ (0.74 å) ions in the hexagonal wurtzite structure. the peak shift may indicate that gd3+ ions have occupied the crystallographic positions of zn2+ ions in the zno host lattice, or itmay be because of the structural strain caused by the formation of internal compressive micro stress (dakhel and el-hilo 2010; kumar et al. 2014; sahu et al. 2017). rietveld refinements have been performed using the full prof programme (shown in fig. 3). the pseudo-voigt function has been used for rietveld refinement of all the samples with the space group p63mc. the estimated lattice parameters have been listed in table i. the lattice parameters are found to decrease with gd doping, similar to those reported in earlier studies (kaur et al. 2016; obeid et al. 2019). the factors like the induced deficiencies (vacancies, interstitial) and the ionic radius of zn and gd ions can be responsible for the observed change (kaur et al. 2016; kumar and thangavel 2017). sem analysis scanning electron micrographs have been used to analyze the morphology of the gd-doped zno powder samples. the sem images reveal a rod-like morphology in pure zno (gora et al. 2022) and the gd-doped zno polycrystalline samples with some proof of agglomeration and phase segregation, as depicted in fig. 4 (a, b and c). profound observation of the particles exhibits that the crystallite size is above 100 nm. the particles were intensive and incompatibly distributed all over the mass. a distinct boundary between neighbouring crystallites can be noticed, despite the proximity of these smaller crystallites. xps analysis the xps technique is an excellent tool for determining the surface chemistry and electron configuration of the various elements present in a multicomponent material. the carbon c1s peak (284.6 ev) has been used as a reference to calibrate all the binding energies of the spectra. the survey spectrum of the gd-doped zno samples is shown in fig. 5. the survey spectra revealed the existence of o, zn, and gd elements without any impurity in the samples. for zno and 2% gd-doped zno powder samples, the binding energies of the zn2p3/2 and zn2p1/2 peaks are found to be 1021.25 ev, 1044.25 ev, 1021.43 ev, and 1044.43 ev, respectively. however, for the 5% gd-doped zno sample, these peaks are at 1021.83 and 1044.83 ev energy positions. the small shift could be assigned to the creation of zn interstitials in zno upon gd doping. the binding energy gap between the zinc doublet peaks has been found at about 23 ev. this indicates that zn in the zno crystal structure is in the zn2+ oxidation state (khataee et al. 2015; gawai et al. 2019) as the spin-orbital splitting of zn2p is 23 ev. this difference does not change with the gd doping pointing out that gd doping has no discernible effect on the chemical position of zno. the o1s asymmetric xps spectraare shown in fig.7 (a) which is asymmetric in shape. the o1s xps spectra of all these samples i.e. the zno, the zn0.98gd0.02o, and the zn0.95gd0.05o have been deconvoluted mainly into two gaussian peaks, as shown in fig. 7 (b, c, and d). the lower binding peaks for pure and gd-doped zno (gd = 2% and 5%) polycrystalline samples have been detected at 529.93 ev, 529.93 ev and 529.78 ev, respectively, which attributed to the lattice oxygen in the hexagonal structure of the zno. the higher binding peak for the pure and the gd-doped zno samples have been found at 531.51 ev, 531.66 ev, and 531.49 ev, respectively, which is due to the presence of oxygen vacancies in the zno structure (bharathi et al. 2020; sukumaran et al. 2021). an additional signal centered at 528.29 ev has been detected in the 5% gd-doped zno powder sample, which could be ascribed to the coordination of oxygen in gd-o-zn along grain boundaries because of the excessive gd dopants and also attributed to the presence of gd2o3 in the sample (yi et al. 2017). the lattice oxygen peak has slightly shifted to the lower binding energy with increasing gd concentration, which has been due to the increased oxygen vacancies with increasing gd doping. the estimated area ratios of the oxygen vacancies peak and the lattice oxygen peak for the samples zno, zn0.98gd0.02o, and zn0.95gd0.05o comes out to be 0.53, 1.30, and 2.49, respectively. these results show that the oxygen vacancies increase with increasing gd concentration. the fig. 8 (a, b) depicts the high-resolution gd4d xps spectra of the gd-doped samples.in the gd4d state, the spin-orbit splatted peaks are at 144.6 ev for gd4d3/2 and 139.6 ev for gd4d5/2 for the 2% gd-doped sample, whereas for the 5% gd-doped zno sample, the spin-orbit splits at 145.5 ev for gd4d3/2 and 139.7 ev for gd4d5/2 as shown in fig. 8 (a, b). this indicates that gd is present in the gd3+ state in the zno hexagonal structure. the shift in peak values of gd4d3/2 and gd4d5/2 from 144.6 ev and 139.6 ev, respectively; in the case of 2% gd-doped sample to 145.5 ev and 139.7 ev, respectively, in the case of 5% gd-doped sample. this shift in gd4d peaks is ascribed to the electron transfer from plasmonics gd to zno because of the strong electronic interaction (covalent bond) between gd and the oxide (ahmad et al. 2011; wang et al. 2012; bharathi et al. 2020). uv visible spectroscopy analysis the uv–visible spectroscopy is a powerful tool for estimating band gap of materials. uv–vis absorbance spectra and tauc plots for the gd-doped zno samples (gd = 0% (gora et al. 2022), 2%, and 5%) samples are shown in figs.9 (a, b, c, and d). the spectra show a red shift with increasing gd amount in the zno.the uv–vis absorption intensity of the synthesized polycrystalline samples is found to reduce with the increasing gd concentration (mazhdi and tafreshi 2018). tauc's plot has been used to calculate the direct band gap of the samples (jain et al. 2006). the direct band gap has been estimated using the following equation: here, α is the absorption coefficient,υ is frequency, h is the planck constant, a is a constant, and eg is the energy band gap of the substance. extrapolating the linear component of the curve plotted among (αhυ) 2 and hυ depicted in fig. 9 (b, c, and d) has been used to obtain the band gap (farhad et al. 2018; ghos et al. 2021). the band gap values calculated for the gd-doped zno samples, i.e.are 3.31 ev (gora et al. 2022), 3.27 ev, and 3.23ev, for the samples gd = 0%, 2% and 5%, respectively. the small redshift observed in the band gap of gd-doped zno samples is because of the changes in electronic structure as well as enhanced oxygen vacancies with the increasing gd doping (yi et al. 2017; flemban et al. 2016), which is responsible for the band gap reduction. photoluminescence spectroscopy analysis the structural flaws like ionic and atomic vacancies, replacements and interstitials have been explored using the pl spectra of the synthesized polycrystalline samples. fig. 10 (a, b and c) shows the deconvoluted, gaussian-fitted pl spectra of the synthesized gd-doped zno polycrystalline powder samples. the pl spectra of the samples were recorded at room temperature in order to determine the types of vacancies, defect band emission etc. (lin et al. 2001; yi et al. 2017). the photoluminescence spectra have been deconvoluted and the different peaks responsible for the emission have been gaussian fitted. for these samples the band edge emission peaksare detected at 381 nm, 384 nm, and 383 nm, for the gd = 0%, 2% and 5% samples, respectively. the uv emission is responsible for the excitonic interaction related to the band edge emission. the intense violet emission exhibited in the gd-doped zno at about 415 nm could be because ofthe oxygen vacancies. the exciton interaction between the holes in the valence band and electrons located in the interstitial zinc could be responsible for the violet emission peak at about 447 nm. intrinsic deficiencies like interstitial zinc and oxygen can be attributed to the peak at 477 nm (singh et al. 2009; kaur et al. 2016). the transformation between singly ionized oxygen deficiency and the photo-created holes (kennedy et al. 2014) or the surface imperfection and electrons near the conduction band, might be responsible for the green emission peak seen for the gd-doped znoat around 525 nm. the green emissions are commonly attributed to theoxygen vacancies (studenikin et al. 1998). for gd-doped zno polycrystalline powder samples, the intensity ratio of the green and ultra-violet emission peaks is found to be 0.090 for zno, 0.204 for the 2% gd-doped zno, and 0.418 for the 5% gd-doped zno. the defect-related emissions enhanced with increasing gd doping in the zno indicate that a large number of deficiencies, such as oxygen vacancies, are most usually related to crystal deformation (yi et al. 2017). the results reveal that the gd doping enhances the zni and vo flaws. it could be attributed to structural deformation created by gd atoms with different ionic sizes than zn in the zno (bandopadhyay and mitra 2015; sukumaran et al. 2021). increasing gd doping in zno indicates an increase in defect states, which matches well with the xps results. we compared our pl results with farhad et al. (2019), who prepared zno dc (drop casting) and zno nanorods. their pl results detected the pl peak at 380 nm and a barely observable green-yellow emission peak; in our case, we find it at 381 nm for zno, 384 nm for 2% gd-doped zno and 383 nm for the 5% gd-doped zno polycrystalline sample. this peak represented zno's near band edge (nbe) transition because of free excitons recombinations and this pl property indicates high crystalline quality. the luminescent characteristics in the visible region are responsible for the different defects, like zinc interstitials (zni), oxygen vacancies (vo), etc., present in the zno crystal matrix. as a result, they reported that both zno (dc) and zno nanorods were found to be defect-free good crystalline and optical properties materials. in our case, all the prepared gd-doped zno powder samples have been found to be with single ionized oxygen vacancies, which are confirmed by the green emission peak at 525 nm in the pl spectra. conclusion the gd-doped zno powder samples were synthesized by the solid-state reaction method. the xrd patterns affirm that gd has been successfully incorporated into the zno lattice and confirm the hexagonal wurtzite structure. sem images have been used to reveal the morphologies of the synthesized samples, which appear as rod-like structures. the xps results showed that the oxygen vacancy-related states in gd-doped samples increased with increasing gd doping. pl findings confirmed that the defect-related states are present in the gd-doped zno polycrystalline samples. the green emission and ultra-violet emission peaks' intensity ratio is 0.418 for the 5% gd-doped zno sample, which is the maximum compared to the pure zno and 2% gd-doped zno polycrystalline powder sample. these findings confirmed that the oxygen vacancies increase as the gd concentration increases and the pl results agree well with the xps results. the uv absorption spectra findings reveal that the band gap in the 5% gd-doped zno sample is found to be 3.23 ev, which is the minimum compared to both the pure zno and the 2% gd-doped zno samples, confirming that eg is reduced with increasing gd concentration. acknowledgment the authors are thankful to usic, university of rajasthan, jaipur, rajasthan (india), for providing sem images of the prepared samples. we also thank department of physics, banasthalividhyapith, banasthali, jaipur, rajasthan (india) for rendering xrd data. funding sources this research is not financed by any agency. authors' contribution sample preparation, data analysis, manuscript composition and writing (mahendra kumar gora); 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636: 339-345. https://doi.org/10.1016/j.tsf.2017.05.020 doped zno nanocrystals also have an attractive optical responsiveness. many theoretical and experimental studies showed that re-doped zno could reportedly absorb ultraviolet (uv) light (chakraborty et al. 2017). obeid et al. (2019) prepared undoped and gd-doped zno nanocrystalline samples using the thermal decomposition method. they observed that the optical absorption spectra of pristine zno increased with a 6% gd doping concentration and the magnetic properties changed with changing dopant amounts. their pl spectroscopy results showed the existence of defects, which increased with increasing gd doping concentrations. they suggested that these dms nanoparticles can be used for magneto-optoelectronic practical device applications. undoubtedly, the re-doped zno nanostructures have been intensively studied recently because this is a rapidly growing field due to their multi-functionality and their use in possible new generation applications. with an aim to understand the effect of gd doping in zno in terms of its electronic and optical properties we have synthesize gd-doped zno powder series of different gd (0%, 2%, and 5%) values. various characterization techniques have been utilized to explore the electronic, structural and optical features of the synthesized powder series. gd doping into zno produced changes in the band gap and enhanced oxygen vacancies related states in the compound. materials and methods the gd-doped zno powder samples with varying gd (0%, 2%, and 5%) concentrations have been synthesized using the conventional solid-state reaction method. a suitable amount of high-purity (99.999% sigma-aldrich) zinc oxide (zno) and gadolinium oxide (gd2o3) powder have been used for their preparation. for achieving perfect homogeneity, the ingredients were properly pounded for ~8 hours in an agate mortar and pestle. the prepared material has been sintered for ~8h at~550°c and cooled at room temperature. again, the mixture was ground for ~2 hours and sintered for ~6 hours at ~550°c. the mixture was milled for ~4 hours before being turned into pellets. finally, these pellets were sintered for around ~8 hours at about ~600°c. finally, we ground the pellets to make the powder. the powder form of the prepared samples has been used for further characterization. characterization techniques the crystallographic structures of the samples have been explored using an x-ray diffractometer (make: panalytical x'pert pro) using the photon energy of cu kα (λ= 1.5406å). sem images have been used for the morphology study of the synthesized samples. the sem equipment model