Effect of organic solvents on crystal shape and ultraviolet absorption of zinc oxide synthesized via solvothermal method

Abstract

ZnO nanoparticles were successfully synthesized by solvothermal reaction of zinc acetate 10-25 g in various organic solvents at 200-300ฺC for 2h. The as-synthesized ZnO shape represented an aggregation of nanorods. Moreover, hexagonal structure was observed at the end of rod. It was found that when the amount of zinc acetate and the temperature of reaction increased, the average length and diameter were increased. However, the growing ratio between ZnO planes was constant. It suggests that the amount of zinc acetate and the temperature of reaction did not affect the growing rate ratio between planes of ZnO crystal. The aspect ratio of ZnO as-synthesized in glycol (1,3 propanediol, 1,4 butanediol, 1,5 pentanediol and 1,6 hexanediol) increased when the boiling point of glycol increased. The ZnO synthesized in alcoholic solvents (1-butanol, 1-hexanol, 1-octanol and 1-decanol) exhibited the aspect ratio similarly to those synthesized in inert solvents (benzene, toluene and xylene) and the aspect ratios of both were increased proportionally to boiling point of different solvents. The aspect ratio of using an individual solvent was constant without changing synthesis condition. The effect of reaction conditions and crystallization mechanism were proposed by interpretation of SEM, TEM, IR and EDS results. It could propose that a mechanism of solvothermal reaction might be an esterification of starting zinc acetate precursor and alcohol on surface of zinc acetate seeds.