Abstract
Recently, it was reported that the band gap of titania could be narrowed by doping with nitrogen. In the present study, nitrogen ion-doped titania nanoparticles were prepared by the solvothermal reactions. After dissolving urea or hexamethylenetetramine in titanium trichloride aqueous solution, the sample was obtained by heating the solution at 90oC for 1 h to precipitate amorphous titania by the homogeneous precipitation reaction, followed by crystallization at desired temperatures. Various phases of titania such as anatase, rutile and brookite were obtained. Crystallite size, specific surface area and color also greatly changed as 5-50 nm, 20-200 m2g-1 and light gray-yellow, respectively, depending on the reaction condition. All colored titania showed photocatalytic activity under visible light irradiation for the oxidative decomposition of NO in air. Especially, the nanoparticles of brookite obtained by the homogeneous precipitation using hexamethylenetetramine followed by heat treatment around 200oC showed excellent photocatalytic activity under visible light irradiation.
