Carbon-doped ZnO nanostructures synthesized using vitamin C for visible light photocatalysis

We report the synthesis of carbon-doped zinc oxide nanostructures using vitamin C, and their visible light photocatalytic activity. Amorphous/crystalline vitamin C-ZnO (VitC-ZnO) structures were obtained from a solution of zinc nitrate hexahydrate, HMT, and vitamin C through heating at 95 degrees C for 1 h. VitC-ZnO structures were calcined in air at 500 degrees C for 2 h to create C-doped ZnO nanostructures. Calcined structures were polycrystalline, with an average crystal domain size of 7 nm. EDS, XPS, and XRD analysis revealed the substitution of oxygen with carbon and the formation of Zn-C bonds in the C-doped ZnO nanostructures. The carbon concentrations, in the form of carbide, were controlled by varying the concentrations of vitamin C (more than 1 mM) added to reaction solutions. On the basis of these experimental results, we propose a possible formation mechanism for C-doped ZnO nanostructures. The C-doped ZnO nanostructures exhibited visible light absorption bands that were red-shifted relative to the UV exciton absorption of pure ZnO nanostructures. The visible light (lambda >= 420 nm) photocatalytic activities of C-doped ZnO nanostructures were much better than the activities of pure ZnO nanostructures.