Reduction and Stabilization of Silver Nanoparticles in Ethanol by Nonionic Surfactants

Abstract

The reduction of Ag + ions in ethanol when certain surfactants are also present in the solution is shown to take place, even in the total absence of light. The reduction process leads to dispersions of silver nanoparticles, which are stable for weeks, although they show a certain tendency to stick to glass walls. Several surfactants were tested, showing that there is a dependency on their nature and concentration. Nonionic ethoxylated surfactants proved to be the most effective of all the surfactants tested, the reduction then being due to the oxidation of oxyethylene groups. In any case, the yield is very low (around 1%). Colloidal stability is achieved by adsorption of surfactant molecules onto the particles, which permits easy transfer of the particles into nonpolar solvents. The reduction rate markedly depends in a first-order fashion on silver salt concentration and depends on temperature according to Arrhenius's law. The optical properties of the obtained colloids are influenced by the surfactant molecules attached to the particle surface.