In this study, nanocrystalline TiO2/Ag composite thin films were prepared by a sol-gel spin-coating technique. By introducing polystyrene (PS) spheres into the precursor solution, porous TiO2/Ag thin films were prepared after calcination at a temperature of 500 degrees C for 4 h. Three different sizes (50, 200, and 400 nm) of PS spheres were used to prepare porous TiO2 films. The as-prepared TiO2 and TiO2/Ag thin films were characterized by X-ray diffractometry (XRD) and by scanning electron microscopy to reveal structural and morphological differences. In addition, the photocatalytic properties of these films were investigated by degrading rnethylene blue under UV irradiation. When PS spheres of different sizes were introduced after calcination, the as-prepared TiO2 films exhibited different porous structures. XRD results showed that all TiO2/Ag films exhibited a major anatase phase. The photodegradation of porous TiO2 thin films prepared with 200 nm PS spheres and doped with 1 mol% Ag exhibited the best photocatalytic efficiency where similar to 100% methylene blue was decomposed within 8 h under UV exposure. (c) 2007 Elsevier B.V. All rights reserved.