Bimetallic Ag/Au nanoparticles: A low temperature ripening strategy in aqueous solution

Bimetallic Ag/Au nanoparticles (NPs) with alloyed and core–shell structures were synthesized at a low temperature (75 °C) from the preformed gold and silver NPs in aqueous solution. The transmission electron microscope (TEM) mapping images, as well as the evolution of UV/vis spectroscopy, revealed that both the digestive ripening and Ostwald ripening were responsible for the formation of above structures during the heating process. Higher Ag ratios led to the growth of silver shell on the surface of Ag/Au alloy core, while lower Ag ratios tended to the formation of alloy particles. Interparticle diffusion, ligands and chemical potential were presumed to play important roles in the formation of alloyed and core–shell bimetallic Ag/Au NPs.