A simple preparative route to highly stable dispersions of uniform silver nanoparticles.

Stable dispersions of uniform silver nanoparticles were prepared by heating silver salts in polyols in the presence of a naphthalene sulfonate/formaldehyde copolymer as dispersant. In the temperature range explored (150-190 degrees C) the modal size and the size distribution of the particles depended on the nature and concentration of the silver salt and the polyol used. Highly dispersed uniform nanoparticles with a diameter of approximately 12 nm were obtained by reducing silver salicylate in diethylene glycol at a metal concentration of 2.5 x 10(-2) mol x cm(-3). Larger silver nanoparticles (approximately 30 nm) and more concentrated dispersions (1.0 mol x cm(-3)) were prepared in ethylene glycol. In all cases the selected dispersant yielded remarkably stable silver sols and facilitated the transfer of the nanoparticles into water, while preserving the stability of the dispersions.