(C S Sm)-tridoped mesoporous TiO2 is prepared by one-step hydrothermal method and characterized by X-ray diffraction (XRD) scanning electronic microscopy (SEM) X-ray photoelectron spectroscopy (XPS) Brunauer-Emmett-Teller (BET) method UV-vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectroscopy By analyzing the structures and photocatalytic activities of (C S Sm)-tridoped TiO2 under visible light irradiation the probable mechanism of tridoped TiO2 is investigated It is assumed that the co-operation of nonmetal elements (C S) and samarium not only leads to appreciable narrowing of the band gap but also promotes the separation of the photo-generated electrons and holes thus greatly improving the photocatalytic activity under visible light irradiation The photocatalyst doped with C S and 1 0% Sm3+ shows the highest photocatalytic activity (C) 2010 Elsevier B V All rights reserved