SiO2/RuO2 modified high surface area titania dioxide nanoparticles prepared by hydrogen reduction were examined for their catalytic properties towards the photodegradation of methyl orange (MO), a common water pollutant in the textile industry. The modified materials present enhanced photocatalytic activity and can decompose the MO faster than the unmodified TiO2. Results showed that doping with RuO2 only offered a marginal benefit over TiO2 alone. On the other hand, modification of TiO2 with RuO2 and SiO2 resulted in a marked increase in the rate constant and the photodegradation efficiency. These results are consistent with the unique structural, morphologoical and surface characteristics of the composite titania dioxide/ruthenium dioxide/silicon dioxide materials. The lower the average particle size and roughness of the materials, the higher the percentage of photodecomposition and the rate constant. The surface doping and modification effects thus appears synergetic to the charge separation process and the photocatalytic results are explained on the basis of the mechanism that involves efficient separation of electron-hole pairs induced by the silicon dioxide particles. This enhances the ability of the modified TiO2 particles to effectively capture protons. Results also show that the modified nanoparticles can be used repeatedly over a long time without loss of efficiency. (c) 2007 Elsevier B.V. All rights reserved.