Visible light-induced OH radicals in Ga₂O₃: An EPR study

Reactive oxygen species (ROS) were found to exist in water suspensions of several metal oxide nanoparticles (NPs), such as CuO, TiO₂ and ZnO. Visible light irradiation enhanced the capability of TiO₂ and ZnO NPs to generate ROS, thus increasing their antibacterial effects. Because of the possible toxic effects on the host tissue it is desired to find nano-metal oxides which do not produce ROS under room light, but only upon a strong external stimulus. Using the technique of electron-spin resonance (ESR) coupled with spin trapping, we examined the ability of Ga₂O₃ submicron-particle suspensions in water to produce reactive oxygen species with and without visible light irradiation. We found that in contrast to ZnO and TiO₂ NPs, no ROS are produced by Ga₂O₃ under room light. Nevertheless blue light induced hydroxyl radical formation in Ga₂O₃. This finding might suggest that NPs of Ga ₂O₃ could be used safely for infected skin sterilization.