Nucleation and growth of silver nanoparticles monitored by titration microcalorimetry

Abstract

The nucleation and the growth of silver nanoparticles were studied by spectrophotometry and transmission electron microscopy, with simultaneous recording of the concomitant enthalpy changes. Silver nanoparticles were stabilized by sodium citrate and reduction was brought about by the addition of hydroquinone in aqueous medium. It was established that nucleation is an exothermic process and heat effects are basically determined by the ratio of silver ions to hydroquinone. The process of nanoparticle formation was divided to three phases: the nucleation phase is exothermic, the growth phase is endothermic and further addition of the reducing agent results in the aggregation of silver nanoparticles, which produces a second exothermic heat effect.