Influence of pH on dendrimer-protected nanoparticles

Highly stable, isolated, and monodisperse Ag nanoparticles, protected by poly(amidoamine) (PAMAM) dendrimers, were prepared via direct chemical reduction. UV-visible absorption, dynamic light scattering, and transmission electron microscopy have been used to study the structure and behavior of the nanocomposites as a function of pH. The data show that pH is a critical determinant of aggregation in PAMAM dendrimers, and that dendrimer aggregation, in turn, strongly influences nanoparticle stability against flocculation, The results allow for a complete understanding of previously reported difficulties in preparing Ag nanoparticles by this method.