Reduction and aggregation of silver ions in aqueous citrate solutions.

Radiolytic reduction of Ag(+) ions and the subsequent formation of Ag clusters were studied in aqueous citrate solutions. Pulse-radiolysis studies show that the presence of citrate in the solution affects the early processes, via complexation of Ag(+) ions with the carboxyl moieties of the citrate. The ratio of citrate to Ag(+) determines the kinetic consequences of the reduction and agglomeration processes. The complexation reduces somewhat the rate of reduction by hydrated electrons. However, when all the ions are complexed to the citrate, the surface plasmon absorption band becomes broader, albeit small, but nevertheless it provides extreme stability to the formed nanoparticles.