Copper nanoparticles with sizes between 10nm and 50nm were grown by condensation in hydrogen at pressures from 10 Pa to 1200 Pa. The crystallite size ranged from 10nm to 25nm using the Scherrer method. X-ray diffraction showed the reflections of metallic copper occasionally mixed with an oxidized phase (CuO or Cu2O). As shown by TEM examination, the smaller particles that did not exceed 25nm exhibited faceted morphologies whereas the bigger ones had ovaled-spherical forms sometimes containing twins. X-ray photoelectron spectroscopy revealed that the nanoparticles consist of a copper core, completely surrounded by a Cu2O shell, which is oxidized to CuO at the surface layer. (C) 2010 Elsevier B.V. All rights reserved.