The Cu particles or clusters dispersed mesoporous SiO2 composite films were prepared by a new method: first the matrix SiO2 films were prepared by sol-gel process combined with the dip-coating technique, and then they were soaked in Cu(NO3)(2) solutions followed by gamma-ray irradiation at room temperature and in ambient pressure. Thus, the prepared Cu/SiO2 composite films were examined by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and optical absorption spectroscopy. It has been shown that the Cu particles grown within the porous SiO2 films are very small, and they are isolated and dispersed from each other with very narrow size distributions. With the Cu particles size changing, ail interesting peak shift was observed in the optical absorption measurement. Possible mechanisms of this behavior are discussed in this paper. (C) 2007 Elsevier Ltd. All rights reserved.