Comparison of structural, optical properties and photocatalytic activity of ZnO with different morphologies: Effect of synthesis methods and reaction media

Highly crystalline ZnO with different morphologies were synthesized by solvothermal and sol–gel synthesis methods in various solvents as the reaction medium. Ethanol, ethylene glycol, 1,4-butanediol and polyethylene glycol 600 (PEG 600) were used as solvents. Without use of any extra surfactant or template and ZnO seed layer, XRD data showed hexagonal single-phase ZnO with the wurtzite crystal structure for all solvents. SEM imaging indicated that ZnO with well-faceted hexagonal, spherical, agglomerated particles and nearly hexagonal rods were produced when ethanol, ethylene glycol, PEG 600 and 1,4-butanediol were used, respectively, in solvothermal synthesis method. In sol–gel synthesis method, nearly spherical and square particles were observed in ethanol and other solvents, respectively. However, no well-ordered structures and architectures were obtained at all. The optical properties of synthesized ZnO were investigated by UV–vis absorption and room temperature photoluminescence (RTPL). The optical properties showed well-defined relationship with solvent viscosity. Photocatalytic activity (PCA) of ZnO with different morphologies have been examined toward photodegradation of phenol. The ZnO prepared via both methods using ethanol as the solvent showed highest PCA. Influences of the solvents and synthesis methods on the morphology of ZnO samples and the effect of the morphologies on the PCA are discussed.