N-doped TiO 2 has been prepared by use of sol-gel systems containing titanium alkoxide, with nitric acid as the nitrogen source.The time needed for gelation of the systems was drastically reduced by ultrasonic irradiation. The peaks assigned to the nitrate and nitrous ions were observed by FT-IR measurement during the sol-gel reaction. The N-doping was confirmed by observation of N-O peaks in the XPS spectrum of the sample heated at 400 °C.The nitrate ion acted as an oxidizer of the ethanol solvent and titanium species. The TiO 2 became doped with nitrogen oxide species were doped as a result of reduction of nitrate ion incorporated into the dried gel samples. These results indicated that the added nitric acid was reduced during the sol-gel transition and heating process, and the resulting NO species were situated in the titania networks. The UV and visible photocatalytic activity of the samples was confirmed by the degradation of trichloroethylene.

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