Reducing ability and mechanism for polyvinylpyrrolidone (PVP) in silver nanoparticles synthesis

Recently, it has been found that polyvinylpyrrolidone (PVP), a popular stabilizer in nanoparticles syntheses, possesses reducing ability for Ag+. Previous explanations of the reduction are, however, thought to be plausible. Based on detailed characterizations including UV-Vis, FTIR-ATR and XPS, we uncover the existence of Ag+ -O interaction, and demonstrate that the Ag+ -PVP complex is first formed via the coordination between Ag+ and O in the carbonyl group, which facilitates electron exchange between Ag+ and adjacent N atom on the pyrrolidone ring. The N atoms with lone pair electrons serve as an electron donator, leading reduction of Ag- to form PVP-capped Ag nanoparticles ultimately.