Preparation and characterization of Ag(Au) bimetallic core–shell nanoparticles with new seed growth method

Ag(Au) bimetallic core–shell nanoparticles were prepared by a new seed growth method. Ascorbic acid was used to reduce the complex of HAuCl4 and hexadecyltrimethylammoniumbromide (CTAB). This resulted in the forming of colorless Au(I) (AuCl2−). It was used as the growth solution to prepare these bimetallic core–shell nanoparticles. These nanoparticles were characterized by UV–vis spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results showed these nanoparticles exhibited core–shell shape and there was large amount of Ag in the shell. These nanoparticles could be produced in a few minutes without violent stirring and the method was easy and convenient compared with others. The effect of amount of AuCl2− on the shape of nanoparticles was also studied. Many small gold nanoparticles were formed on the surface of bimetallic core–shell nanoparticles in the presence of excess AuCl2−. The mechanisms were also proposed to explain the process of colloidal preparation.