Ta-doped photocatalysts were prepared using three different techniques: reactive d.c.-magnetron sputtering, sol-gel and grafting of tantalum on MCM-41 and TiO2. The composition of the catalysts prepared by reactive d.c.-magnetron sputtering consisted in tantalum and titania, while that of sol-gel and grafted catalysts of Ta-titania-silica mixed oxides. The characterization of these catalysts was carried out using the adsorption-desorption isotherms of N-2 at 77 K, X-ray diffraction (XRD) patterns, small-angle X-ray scattering (SAXS), atomic force microscopy (AFM), XPS, TEM. and Si-29- and Ta-181-CP/MAS NMR spectra. The behavior of these photocatalysts was checked in acetone degradation. The photocatalytic tests indicate that, depending on the preparation conditions and tantalum content, an enhancement of the activity occurs as compared with pure titania. Sol-get and Ta-grafted MCM and TiO2 catalysts exhibited a rather poor activity, which was correlated with the lack of crystallinity of titania. (c) 2006 Elsevier B.V. All rights reserved.