4-(N,N-Dimethylamino)pyridine-Protected Au Nanoparticles:  Versatile Precursors for Water- and Organic-Soluble Gold Nanoparticles

Ligand-exchange reactions of 4-( N, N -dimethylamino)pyridine-capped gold nanoparticles (DMAP−Au NP) with functionalized thiols (RSH) were investigated. A simple, convenient, and facile synthesis method has been developed. An important feature of this method is its requirement of only very modest quantities of excess thiol ligand. DMAP−Au NP prove to be versatile precursors for both water- and organic-soluble gold NP. DMAP is readily displaced by various functionalized thiols ranging from mercaptocarboxylic acids to ferrocene-terminated thiols. UV−vis spectroscopy and transmission electron microscopy (TEM) confirm that the mean diameter and the size dispersity of the initial DMAP−Au NP were retained upon ligand exchange. The RS−Au NP thus prepared were efficiently purified by gel permeation chromatography (GPC) with neither residual DMAP nor RSH detected in the final product.