We report a photochemical procedure induced by ultraviolet (UV) radiation for the preparation of palladium (Pd) nanoparticles on silicon surface at room temperature. Palladium acetate (Pdac, Pd(OCOCH3)(2)) was used as the precursor which was sprayed-on to the Si and irradiated by UV light at a wavelength of 172 nm. Scanning electron microscope (SEM), AFM, XRD, and UV-Vis spectroscopy have been used to characterize the as-prepared nanoparticles. The mechanism of growth of Pd particles and the photo-reduction induced by UV radiation are discussed. The effects of precursor concentration, UV-irradiation time, and annealing conditions on the size and distribution of the palladium nanoparticles on Si are also reported. (C) 2004 Elsevier B.V. All rights reserved.