Influence of the sequence of the reagents addition in the citrate-mediated synthesis of gold nanoparticles

The role of sodium citrate (SC) in the formation and growing mechanism of gold nanoparticles was systematically examined. Obtained results show that oxidation of SC can be induced either by the presence of HAuCl4 or by its thermal decomposition under air. By exchanging the order of reagent addition, it is possible to increase the oxidation rate of SC and hence control the size and morphology, thus allowing preparation of nanoparticles with a narrower size distribution than the standard Turkevich approach. © 2011 American Chemical Society.