Abstract: The 3d transition metal ions [Cr(Ⅲ), Fe(Ⅲ), Mn(Ⅱ), Co(Ⅱ), Ni(Ⅱ), Cu(Ⅱ), Zn(Ⅱ)] nanocrystalline doped with TiO₂(abbr. m^3d-TiO₂) were characterized by AFMand XRD. The m^3d-TiO₂ nanostructured film electroede was prepared and investigated with photoelectrochemical techniques. The results show that the size of m^3d-TiO₂ nanocrystalline particles was quite uniform and the radii were about 15 nm. The m^3d-TiO₂ nanocrystalline particles were a mixture of brookite and anatase crystal forms. Of all the m^3d-TiO₂ investigated in this paper, however, the photocurrent intensity of Zn²⁺-TiO₂ nanostructured film electode was higher than that of the electrode undoped with TiO₂. The phenomenon of p-n type inversion was observed in certain wavelength range, which was caused by 3d transition ions doping.

Key words: Doping of 3d transition metal, TiO₂ nanostructured porous film electrode, n-p Type inver sion, Photoelectrochemistry