Copper metal nanoparticles have been formed by irradiation with 253.7 nm light from a low pressure Hg-arc lamp in the presence of a protective agent gelatin. The nanoparticles were characterized by their absorption maxima and transmission electron micrographs, The quantum yields of formation of the metal nanoparticles increase in the presence of the stabilizer as well as in the presence of a photosensitizer, benzophenone (BP). Damping of copper plasmon absorption band was not observed in the presence of benzotriazole. (C) 2002 Published by Elsevier Science B.V.