Protection effects of hydrophile-grafted silicone copolymers on the formation of colloidal silver nanoparticles

Silicone copolymers with varying weight percents of hydrophilic groups with or without charge were used as protectors to stabilize the silver nanoparticles prepared by chemical reduction of Ag⁺ ion with sodium borohydride NaBH₄, and the effects of hydrophobic moiety and hydrophile on protection were investigated. UV-vis spectroscopy was employed to characterize the silver colloids, and transmission electron microscopy (TEM) was used to determine the metal particle sizes and morphologies. The silicone copolymer can effectively protect the formation of silver nanoparticle with sufficiently high concentration of polymer. It was found the high hydrophobic content rather than hydrophilic content results in better protection to nanoparticles. The results strongly suggest that the silicone copolymer of SHE cannot effectively protect the silver nanoparticle if its hydrophile cannot interact with metal ion or nanoparticles as it is positive-charged.