Synthesis of reduced graphene oxide nanosheets from sugarcane dry leaves by two-stage pyrolysis for antibacterial activity

Oxidative-exfoliation methods were in vogue in the production of rGO from graphite.Processing of such synthetic graphite needs high temperatures(2500℃).Thus,such process is not cost-effective.The present study is made on the dry leaves of sugarcane(Saccharum officinarum)as an alternative raw material so as to be economical and environmentally benign.The dry leaves are subjected to two-step pyrolysis without any catalyst or reducing agent in far divergent temperatures to produce as prepared and acid treated rGOs.They were evaluated by UV–Vis.,FTIR,XRD,Raman spectroscopy,TGA/DTG,BET,FESEM-EDS and TEM.The as prepared rGO has few layers with irregular and folded architecture whereas acid-treated rGO has thinly stacked crumpled sheets with many wrinkles on its surface.The prepared rGOs have multilayered graphitic structure due to the unique ratio between G and D bands.Acid treated rGO has poor thermal stability as compared to that of as-prepared rGO at high temperatures due to the variation in the oxygen-containing functional groups.Acid treated rGO has low antibacterial activity as compared to that of the as-prepared rGO due to the paucity of the functional groups.

Flexible sodium-ion batteries using electrodes from Samanea saman tree leaf-derived carbon quantum dots decorated with SnO_(2) and NaVO_(3)

Carbonaceous materials with large interlayer spacing and disordered structure are considered suitable as electrodes in sodium-ion batteries so as to overcome the problem encountered in conventional electrodes.In this study,carbon quantum dots(CQDs)decorated with SnO_(2)and NaVO_(3)are used as electrodes in the fabrication of flexible Na-ion batteries.CQDs are prepared from dead leaves of the Samanea saman tree through alkaline-peroxide treatment and hydrothermal carbonization.As-prepared CQDs exhibit a quantum yield of 21.03%at an excitation wavelength of 360 nm.Various separators such as indium-doped tin oxide/polyoxyethylene tridecyl ether(ITO/PTE),rice paper(RP),silicone with three big holes(SIL BH),silicone with many small holes(SIL SH)and cellulose paper(CP)have been tried in flexible Na-ion batteries.SIL SH achieved higher specific capacitance(881 F g-1)than other separators due to the function of many small holes on the surface of the silicone.The SIL SH separator delivered higher discharge capacities of 141 and 114 mC g-1 at 1.5 and 2.5 V than SIL BH.The RP separator delivered specific discharge capacities of 1087 and 347 mC g-1 in the 1st and 50th cycles,respectively,at 1 V.The RP separator delivered a high initial specific discharge capacity of 698 mC g-1 at 2 V and maintained a good discharge capacity of 222 mC g-1 in the 50th cycle.As compared to RP,SIL SH delivered high specific discharge capacity of 4246 in 1st cycle at 2 V but maintained a capacity of 71 mC g-1 in the 50th cycle.This study reveals the scope of developing flexible Na-ion batteries with high capacity and cyclability using carbonaceous materials derived from the leaves of the S.saman tree.

Effect of various ratios of poly(3-hexylthiophene)with polyvinyl alcohol gel-polymer electrolytes in flexible sodium-ion batteries using Samanea saman tree-leaf-derived carbon quantum dots decorated with SnO_(2)and NaVO_(3)

Gel-polymer electrolytes with high thermal stability and mechanical properties were considered suitable in rechargeable batteries so as to overcome the problems encountered in liquid electrolytes.In a previous study,flexible sodium-ion batteries(FSIBs)were fabri-cated using electrodes made of carbon quantum dots(CQDs)decorated with SnO_(2) and NaVO_(3) utilizing a polyvinyl alcohol(PVA)/P3HT gel-polymer electrolyte at a ratio of 1:0.05.In addition,various separators such as indium-doped tin oxide/polyoxyethylene tridecyl ether(ITO/PTE),rice paper(RP),silicone with three big holes(SIL BH),silicone with many small holes(SIL SH)and cellulose paper(CP)were tested in flexible Na-ion batteries.The SIL SH delivered a high specific discharge capacity of 4246 mAh g^(-1) in the initial cycle at 2 V and maintained a value of 71 mAh g^(-1) in the 50th cycle.With the aim of improving the cyclic ability of FSIBs,different weight ratios of PVA/P3HT(1:0.025,1:0.05,1:0.1,1:0.15,1:0.2)were tried in this work using the electrodes CQDs@SnO_(2) and CQDs@NaVO_(3).The above ratios were referred to as B25,B50,B100,B150 and B200,respectively.SIL SH was used as a separator.Cyclic voltammetry studies indicated that B150 had a high specific capacitance of 13062 F g^(-1).B25 and B100 exhibited high discharge capacities(171 mAh g^(-1))and(151 mAh g^(-1))compared to that of other ratios B50(75 mAh g^(-1)),B150(88 mAh g^(-1))and B200(54 mAh g^(-1))in the 50th cycle at 2.0 V.This study reveals the scope of developing FSIBs of high capacity and cyclability at different voltages using carbonaceous electrodes and gel-polymer electrolytes with different ratios of PVA/P3HT.The focus of the present study is to bring out the optimum ratio of PVA/P3HT for maximizing the cyclic ability of FSIBs.