Visible-Light-Induced Bactericidal Activity of Titanium Dioxide Codoped with Nitrogen and Silver

Titanium dioxide nanoparticles codoped with nitrogen and silver (Ag2O/TiON) were synthesized by the sol-gel process and found to be an effective visible light driven photocatalyst. The catalyst showed strong bactericidal activity against Escherichia coli (E. coli) under visible light irradiation (lambda > 400 nm). In X-ray photoelectron spectroscopy and X-ray diffraction characterization of the samples, the as-added Ag species mainly exist as Ag2O. Spin trapping EPR study showed Ag addition greatly enhanced the production of hydroxyl radicals (center dot OH) under visible light irradiation. The results indicate that the Ag2O species trapped e(CB)(-) in the process of Ag2O/TiON photocatalytic reaction, thus inhibiting the recombination of e(CB)(-) and h(VB)(+) in agreement with the stronger photocatalytic bactericidal activity of Ag2O/TiON. The killing mechanism of Ag2O/TiON under visible light irradiation is shown to be related to oxidative damages in the forms of cell wall thinning and cell disconfiguration.