Formation and Stabilization of Silver Nanoparticles through Reduction by <i>N</i>,<i>N</i>-Dimethylformamide

The reduction of Ag+ ions in N,N-dimethylformamide (DMF) is shown to take place spontaneously at room temperature. When no other additives are present in the system, the slow reduction leads to silver deposition on the glass walls of the container, while in the presence of 3-aminopropyltrimethoxysilane (APS) stable dispersions of silver nanoparticles are obtained. Even though the reduction can be performed at room temperature, higher temperatures markedly increase the reaction rate and improve the monodispersity of the colloid. The reduction rate and morphology of the colloidal particles also depend on the ratio [Ag]/[APS]. The reduction takes place both with nitrate and perchlorate as counterions, which confirms that DMF plays the role of a reducing agent. Additionally, when excess APS is used, a thin, homogeneous silica shell is formed on the silver particle surface.