Among TiO 2 nanostructures, TiO 2 nanotubes attracted mach attention because of its unique properties such as high surface to volume ratio and electron traort in one dimension. The band gap of TiO 2 is 3.1-3.2 eV, so TiO 2 is active only under UV irradiation. To reduce the band gap of TiO 2 , the method doping with other combinations is used. In this project, TiO 2 nanotubes doped with Cu, Fe, Cr, Zn, and Cd were synthesised by in-situ anodizing and mixing of anodizing-dipping method. The morphology, structure, optical and photocatalytic properties of these nanotubes were examined by FE-SEM, EDX, XRD and UV-Visible. FE-SEM images showed that TiO 2 nanotubes have been prepared by anodizing method. By studying the EDX and XRD spectra, the presence of used metals in this nanotubes was proven. The UV-Visible spectroscopy showed that by metal doping, band gap of TiO 2 has decreased. The band gap of doped TiO 2 nanotubes in solutions of 0.04M Cu(NO 3 ) 2 .3H 2 O, 0.005M KCrO 4 and 0.009M K 3 Fe(CN) 6 that were prepared by anodizing the same time, were 2.65, 2.82 and 2.6 eV, respectively. As well as the band gap of doped TiO 2 nanotubes by dipping method, for 3 hours dipping in 0.05M ZnSO 4 .7H 2 O, 1 hours dipping in 0.05M CdCl 2 .H 2 O, 3 hours dipping in 0.05M CrCl 3 .6H 2 O were 2.98, 2.9 and 2.85 eV, respectively. Then photocatalytic properties of these nanotubes was investigated. Samples irradiated with visible light, in methylene blue dye solution. Results showed that the doped samples irradiated with visible light are able to degrade the methylene blue dye. However degradation of methylene blue dye on bare TiO 2 nanotubes could be occured only in the presence of UV light. As a result, doping of Cu, Cr, Fe, Zn and Cd in TiO 2 nanotubes, improved their photocatalytic activity in the visible region.
