N-Doped TiO2 Nanoparticle Based Visible Light Photocatalyst by Modified Peroxide Sol−Gel Method

The peroxide gel route is employed to synthesize N-doped TiO 2 nanoparticles (NP) at low temperature using titanium tetraisopropoxide, ethylmethylamine, and hydrogen peroxide as precursors. Structural studies show anatase phase in the undoped titania NPs as well as at 5 at. % N-doped titania NPs, although with a degree of matrix disorder in the latter case. The annealing of N-doped titania NPs at different temperatures shows that above 400 °C nitrogen escapes the O−Ti−O matrix and at 500 °C the sample becomes crystalline. Transmission electron microscopy reveals that the particle size is in the range of 20−30 nm for the undoped TiO 2 but only 5−10 nm for N-doped TiO 2 . At higher nitrogen concentration (10 at. %) bubble-like agglomerates form. FTIR and photoluminescence quenching also confirm the incorporation of nitrogen in anatase TiO 2 . Optical properties reveal an extended tailing of the absorption edge toward the visible region upon nitrogen doping. X-ray photoelectron spectroscopy is used to examine the electronic state of doped nitrogen and the associated possible electronic modification of the TiO 2 matrix. Under visible light irradiation the undoped TiO 2 NPs do not show any significant photocatalytic activity, as expected; however, the 5 at. % N-doped TiO 2 NPs show excellent activity.