Electrochemical deposition of N-doped ZnO film and its superior potential to inactivate microorganisms

Nitrogen-doped ZnO (ZnO:N) is a semiconductor with enhanced photocatalytic properties, which makes it a promising material for antimicrobial applications. In this study, the photoelectrocatalytic inactivation of Staphylococcus aureus, Escherichia coli and Candida albican on ZnO:N films was investigated. The films were prepared by electrochemical deposition with different doping concentrations (20, 40, 60 cm³ min⁻¹). X-ray diffraction patterns showed that pure ZnO and ZnO:N films displayed a crystalline wurtzite structure. Scanning electron micrograph revealed a hexagonal nanorod morphology for samples. The substitutional doping that occurred in ZnO favored the formation of oxygen vacancies, as shown by X-ray photoelectron spectroscopy measurements. The nitrogen doping caused a decrease in the values of the band gap energy (E_bg) from 3.17 to 3.12 eV. Photoelectrochemical studies showed higher photocurrent density for ZnO:N compared to ZnO films, reaching 60 µA cm⁻² at 0.70 V (vs. Ag/AgCl). The chronopotentiometry curves showed that all films present n-type semiconductor behavior and flat band potentials suitable for generating reactive oxygen species capable of inactivating microorganisms. Under irradiation, all ZnO:N films inhibited S. aureus. Also, ZnO:N-40 film showed complete inhibitory effects on E. coli and C. albicans. These results highlight the potential of nitrogen-doped ZnO films for antimicrobial applications.