The preparation of nano-size Ag particles and their application for forming nanostructured catalysts on various surfaces are described. Silver colloid solutions were prepared by reduction of Ag(I) salt by tin(II) and characterized by electron microscopy, X-ray diffraction and light absorption spectra. Depending on the colloid preparation conditions metal particles of 5-100 nm size were obtained. According to XRD data, the colloid particles contain Ag and SnO2 phases and no metallic Sn. The Ag nanoparticles were found to be efficient electrocatalysts for anodic oxidation of formaldehyde in alkaline solutions. The catalytic activity of a glassy carbon electrode with Ag surface coverage of 0.3-1 mu g cm(-2) is similar or even exceeds that of the metallic electrode. The silver particles were used for the initiation of the electroless copper deposition process on dielectrics; for that 1-2 mu g cm(-2) Ag is needed. (C) 2005 Elsevier Ltd. All rights reserved.