BACKGROUND: In this study, visible-light-derived photocatalytic activity of metal-doped titanium dioxide nanosphere (TS) stacking layers, prepared by chemical vapor deposition (CVD), was investigated. The as-grown IS spheres, having an average diameter of 100-300 nm, formed a layer-by-layer stacking layer on a glass substrate. The crystalline structures of the TS samples were of anatase-type. RESULTS: Ultraviolet (UV) absorption confirmed that metallic doping (i.e. Co and Ni) shifted the light absorption of the spheres to the visible-light region. With increasing dopant density, the optical band gap of the nanospheres became narrower, e.g. the smallest band gap of Co-doped TS was 2.61 eV. Both Ni- and Co-doped TS catalysts showed a photocatalytic capability in decomposing organic dyes under visible irradiation. In comparison, Co-doped TiO2 catalyst not only displays the adsorption capacity, but also the photocatalytic activity higher than the N-doped TiO2 catalyst. CONCLUSION: This result can be attributed to the fact that the narrower band gap easily generates electron - hole pairs over the TS catalysts under visible irradiation, thus, leading to the higher photocatalytic activity. Accordingly, this study shed some light on the one-step efficient CVD approach to synthesize metal-doped TS catalysts for decomposing dye compounds in aqueous solution. (C) 2010 Society of Chemical Industry