Morphology-dependent photo-catalysis of bare zinc oxide nanocrystals

Three kinds of ZnO nanocrystals (NCs) with different morphologies including multilayer disks, truncated hexagonal cones and short rods have been successfully synthesized by a solvothermal method without participation of surface capping agents. The water content in used N,N-dimethylformamide (DMF) solvent has been found to play an important role in controlling the formation of crystal planes, concentration of defects, and morphology of the ZnO NCs. The photocatalytic degradation of methyl orange in aqueous solution has been investigated in detail by employing the three kinds of ZnO NCs as photocatalysts under UV irradiation separately. Apparent reaction rates for different morphological ZnO NCs follow the order of short rods > truncated hexagonal cones > multilayer disks, implying strong photostability-dependent photocatalysis behavior of the ZnO NCs. Combined with photocorrosion, possible reasons for the difference of photocatalytic activity among them are discussed.