Fabrication of Cu–Ag core–shell bimetallic superfine powders by eco-friendly reagents and structures characterization

Superfine bimetallic Cu–Ag core–shell powders were synthesized by reduction of copper sulfate pentahydrate and silver nitrate with eco-friendly ascorbic acid as a reducing agent and cyclodextrins as a protective agent in an aqueous system. The influence of Ag/Cu ratio on coatings was investigated. Ag was homogeneously distributed on the surface of Cu particles at a mole ratio of Ag/Cu=1. FE–SEM showed an uniformity of Ag coatings on Cu particles. Antioxidation of Cu particles was improved by increasing Ag/Cu ratio. TEM–EDX and UV–vis spectra also revealed that Cu cores were covered by Ag nanoshells on the whole. The surface composition analysis by XPS indicated that only small parts of Cu atoms in the surface were oxidized. It was noted that the hindrance of cyclodextrins chemisorbed on particles plays an important role in forming high quality and good dispersity Cu–Ag (Cu@Ag) core–shell powders.