Visible-Light-Responsive Photocatalytic Activity Significantly Enhanced by Active [VZn+VO+] Defects in Self-Assembled ZnO Nanoparticles

Defect influences on the photoactivity of ZnO nanoparticles prepared by a powdered coconut water (ACP) assisted synthesis have been studied. The crystalline phase and morphology of ZnO nanoparticles were effectively controlled by adjusting the calcination temperature (400-700 degrees C). An induced transition of hybrid Zn-5(CO3)(2)(OH)(6)/ZnO nanoparticles to single-phase ZnO nanoparticles was obtained at 480 degrees C. The morphological analysis revealed a formation of ZnO nanoparticles with semispherical (similar to 6.5 nm)- and rod-like (similar to 96 nm) shapes when the calcination temperatures were 400 and 700 degrees C, respectively. Photoluminescence characterizations revealed several defects types in the samples with V-Zn and V-O(+) being in the self-assembly of semispherical- and rod-like ZnO nanoparticles. The photocatalytic activity of the ZnO nanoparticles was examined by assessing the degradation of methylene blue in an aqueous solution under low-intensity visible-light irradiation (similar to 3 W m(-2)). The results point toward the self-assembly of semispherical- and rod-like ZnO nanoparticles that had significantly better photocatalytic activity (similar to 31%) in comparison to that of spherical-agglomerated- or near-spherical-like species within 120 min of irradiation. The possible photocatalytic mechanism is discussed in detail, and the morphology-driven intrinsic [V-Zn+V-O(+)] defects are proposed to be among the active sites of the ZnO nanoparticles enhancing the photocatalytic activity.