PPI–SA and PAMAM–SA dendrimers assisted synthesis of silver nanoparticles: structure, optical properties and stability

Abstract

"Poly(propylene-imine) (PPI) and poly(amidoamine) (PAMAM) dendrimers of different generations functionalized with 4-(4′-pentoxybenzoyloxy)salicylaldehyde (SA) promesogenic units were applied for the synthesis of silver (Ag) nanoparticles in tetrahydrofuran–water mixture solution. Influence of the dendrimer type and their generations on formation and stability of nanoparticles were studied. Structural and optical properties of Ag nanoparticles, and their modifications with aging were characterized by means of transmission electron microscopy, UV–vis absorption and Fourier transform infrared spectroscopy. Experimental investigations showed that immediately after the synthesis the particles were of spherical shapes with slightly different sizes depending on the used dendrimer type, but independent of their generation. The dendrimer type strongly influenced particle modifications during the aging: particles protected with PPI–SA dendrimers undergone significant alterations in time both in their sizes and shapes, while the particles remained almost unchanged when PAMAM–SA dendrimers were used for their protection. We, therefore, presume that morphological differences of aged nanoparticles are mainly determined by different chemical structures of dendrimer cores rather than by their terminal groups; additional carbonyl groups in PAMAM–SA dendrimer core units play an important role in stabilizing Ag nanoparticles.