Insights into the antimicrobial mechanism of Ag and I incorporated ZnO nanoparticle derivatives under visible light.

ZnO nanoparticles doped with I and Ag were prepared via a solvothermal method. Characterizations of the as-synthesised samples were carried out using X-ray diffraction, X-ray photoelectron spectroscopy, UV-Vis spectrometry, Photoluminescence, transmission electron microscopy and scanning electron microscopy. The nanoparticles exhibit light absorption for wide spectra from ultra-violet (UV) to visible light. The antimicrobial efficacy was evaluated against Escherichia coli (MG1655) and Staphylococcus aureus (USA300) as models of Gram-negative and Gram-positive microorganisms, respectively. The double-doped nanoparticles demonstrated their potent efficacy against both types of microorganisms and they may have great potential in combating infectious diseases. More importantly, the insights into the mechanisms underlying the antimicrobial effects were revealed: synergistic effect of reactive oxygen species (ROS) generation and Ag+ release. Specifically, the ROS generation was believed to be dominant in the I:Ag:ZnO sample under visible light, while both ROS generation and Ag+ release were found to play an important role in the bacteria-killing by Ag:I:ZnO in the visible light and dark conditions. The Ag+ release was found to be the dominant antimicrobial mechanism for the Ag:ZnO NP sample in our experiment.