Synthesis of ZnO Nanoparticles Assisted by N Sources and their Application in the Photodegradation of Organic Contaminants

A modified polymeric precursor method assisted by N sources (urea or melamine) was used to obtain anion-doped ZnO nanoparticles. The influence of these molecules on the physical-chemical and photocatalytic properties of the as-synthesized samples was investigated. The ZnO nanoparticles exhibited a hexagonal wurtzite phase and crystallite sizes of approximately 20 nm. The addition of urea or melamine to the Zn2+ precursor solution improved the surface properties of the materials and resulted in controlled growth of the N-doped ZnO nanoparticles, with urea showing superior performance for this purpose. These changes led to improved photocatalytic performance in the degradation of methylene blue (MB) dye and ethionamide antibiotic under UVC irradiation. It was observed that the indirect mechanism involving (OH)-O-center dot radical attack played the main role in both photodegradation reactions catalyzed by the as-synthesized ZnO samples, whereas the photosensitization mechanism had a negligible influence. The use of ESI-MS analyses showed that the MB dye molecules were broken up by the action of the ZnO photocatalyst, indicating the occurrence of a mineralization process.