Synthesis and pH Dependent Optical Properties of Gold Nanoparticles Capped with Mercaptopropionic Acid

摘要

A simple method is reported for preparing goldnanoparticles capped with 3-mercaptopropionic acid(MPA). Thecapped Au nanoparticles can be isolated as a dark brown solidwhich can be re-dispersed in sodium hydrate solution. Theaverage size of nanoparticles is 4.9+-0.7 nm, determined byHRTEM. The surface plasmon band of Au nanoparticles around520 nm was found red-shifted together with a slight damping andbroadening, as the pH of the colloid is adjusted from 11 to 3.5.Such a shift is attributed to the pH dependent surface charge ofthe nanoparticles.