Copper-doped zinc oxide nanoparticles as efficient antimicrobial agents: bridging electronic properties with biological properties

Zinc oxide nanoparticles (ZnO NPs) have already shown potential applications as antimicrobial agents. However, the large band gap and charge carrier recombination of ZnO NPs reduce the production of reactive oxygen species, which limits their antibacterial activity; therefore, further modifications of their structural and electronic properties are required. Herein, Cu doping of ZnO NPs has been carried out by a microwave-assisted method to modify their structural, electronic, and biological properties. The structural and morphological analysis of the prepared Cu-doped ZnO NPs confirmed that Cu is well incorporated into the ZnO NPs lattice, and the morphology is quasi-spherical with a diameter range of 20-25 nm. The changes in the band gap and defect states in ZnO NPs, formed upon Cu doping, were confirmed by UV-visible and theoretical analysis. The antimicrobial potential of ZnO and Cu-doped ZnO NPs against S. aureus, E. coli, P. aeruginosa, and C. albicans has been evaluated by measuring the zone of inhibition, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC). The results showed an enhancement of the antimicrobial potential of ZnO NPs upon Cu doping, which could be related to modifications of the electronic structure that could potentially affect redox properties.