Deposition of Silver Nanoparticles on Silica Spheres by Pretreatment Steps in Electroless Plating

A new method was developed for the homogeneous deposition of silver nanoparticles on colloid silica spheres. The method does not make use of an external electron source, but of a chemical moiety adsorbed on the surface, which can easily get oxidized. The process is mainly performed in two steps: a first step in which the adsorption of Sn2+ ions occurs on the surface of the silica particles and a second step comprising the addition of Ag+ ions, which are reduced and simultaneously adsorbed on the surface, while Sn2+ oxidizes to Sn4+. The whole process can be repeated to obtain a denser coating on the surface.