Preparation of colloidal silver dispersions by the polyol process

In a previous paper (J. Mater. Chem., 1996, 6, 573), we reported that colloidal silver dispersions can be synthezised by the polyol process, using an ethylene glycol–polyvinylpyrolidone (PVP) solution to reduce silver nitrate under precise temperature conditions. Quasi-spherical particles with a narrow size distribution were obtained. Low precursor and PVP concentrations, in contrast to high silver nitrate concentrations, were found to yield monodisperse systems with an average particle size of 15 to 21 nm. To understand the particle formation mechanism, the evolution of particle size and shape during the reaction was monitored by TEM and UV absorption spectroscopy techniques. An Ostwald ripening mechanism is proposed to account for the formation of the silver particles, even though the variation of temperature with time is not ideal for a complete mechanistic understanding.