The nano-sized particles of anatase titanium oxide (TiO_2) were obtained by hydrolysis of titanium ester (TNB) in basic media and dehydrated in acid media. And then the anatase titanium oxide was treated with nitrogen plasma. The effect of nitrogen plasma treating time on the activity of photo-catalytic reduction of the Cr_2O_7^(2-) for sample obtained was investigated. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Transmission Electron Microscope (TEM) and Ultraviolet (UV). A peak of 396 eV in the N1s XPS spectra of sample obtained with nitrogen plasma treated TiO_2 showed that nitrogen-doped titanium oxide (TiO_(2-x)N_x) has been obtained. The spectra of UV showed that the light absorption of TiO_(2-x)N_x obtained by nitrogen plasma treated TiO_2 for 10min. had moved to the visible region. The picture of TEM and spectra of XRD indicated that the crystallographic forms and particle dimension had no apparent change for both the modified and the unmodified TiO_2. When the TiO_2 sample was treated for 7 min with nitrogen plasma, it exhibited best photo-catalytic activity.
