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

Abstract

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 (λ > 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 (•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.