The mechanism of stabilization of silver nanoparticles by chitosan in carbonic acid solutions

The aim of the current study was to investigate the growth mechanisms of the silver nanoparticles (Ag NPs) in chitosan macrogels and microgels acting both as reductants and stabilizing agents in self-neutralizing, biocompatible, and environmentally benign carbonic acid solutions. The chitosan-hydroquinone microgels loaded with Ag NPs incorporated in carbonic acid solutions were successfully prepared. However, it was found that during the reduction of nanoparticles by hydrogen, the microgels tend to deteriorate. Yet, it was found that the duration of the process of silver reduction by chitosan in the composite macrogels obtained in a solution of carbonic acid took no more than 1 month. The process of the reduction was accompanied by the appearance of relatively small aggregates of Ag NPs uniformly distributed in the volume of the hydrogel. Such a "gentle" reduction of Ag NPs allows to avoid the loss of mechanical stability of the gel.