Generation of Ag Nanoparticles by PAMAM Dendrimers and their Size Dependence on the Aggregation Behavior of Dendrimers

Stable silver nanoparticles were generated in aqueous medium by amine, hydroxy and carboxylate terminated poly(amidoamine) (PAMAM) dendrimers in the absence of conventional reducing agents and light irradiation. Mechanistic studies suggest that, in spite of their lower pK(a) values, tertiary amines present in the dendritic structures act as the reducing agent. Dynamic light scattering and electron microscopic studies reveal that PAMAM dendrimers aggregate in presence of silver ions and the aggregation propensity plays a pivotal role in altering the size and shape of the nanoparticles generated in the dendritic milieu. The formation of metal nanoamine particles with uniform size and shape by terminated PAMAM dendrimer is attributed to the unique aggregation propensity of amine terminated PAMAM.