Visible light-induced photocatalytic and antibacterial activity of N-doped TiO₂

Previous reports of some studies have described that nitrogen (N)-doped titanium dioxide (TiO₂ ) exhibits photocatalytic antibacterial activity under visible light irradiation and that reactive oxygen species (ROS) is involved in its activity. For prevention and treatment of peri-implantitis, an inflammatory lesion caused by the bacterial infection of plaque adhering to the circumference of an implant, we considered that applying N-doped TiO₂ to dental implant surfaces can be effective. For this study, we aimed at evaluating visible light-induced antibacterial activity of titanium (Ti) treated with NaOH and hot water, and subsequently heated in an ammonia (NH₃ ) gas atmosphere at 500°C for 3 hr to quantify the generated amount of ROS available for antibacterial activity. N-doped anatase-type titania (TiO₂ -xNx) is formed on the Ti substrate surface. Under visible light, markedly more hydroxyl radicals were generated with a nitrogen-doped titanium dioxide plate than with a pure titanium plate. Hydrogen peroxide exhibited the same tendency. Furthermore, it showed visible light-induced antibacterial effects over Escherichia coli. Results demonstrate that N-doped TiO₂ can be useful as a dental implant surface with low risk of postoperative infection when using visible light irradiation.