A library of single-crystal metal-tin nanorods: Using diffusion as a tool for controlling the morphology of intermetallic nanocrystals

We describe a unified and general template-based strategy for synthesizing a library of morphology-controllable M-Sn (M = Co, Ni, Cu, Ag, Au, Pt, Ru) intermetallic nanorods. The reaction of beta-Sn nanorod templates with appropriate metal salt solutions under reducing conditions yields single-crystal intermetallic nanorods of CoSn3, Ni3Sn4, Cu6Sn5, Ag4Sn, AuSn, PtSn, and RuSn2. Temperature plays a key role in maintaining the morphology of the beta-Sn nanorod templates in the final M-Sn products and also selectively generating spherical nanocrystals vs dense nanorods vs hollow nanorods, in some cases (e.g., CoSn3) within the same system. These observations are linked to the diffusion process, and accordingly, the melting points of the transition elements used in this study can help us understand and predict the morphologies that can be formed, as well as the lowest temperature at which a particular intermetallic compound can form using low-temperature solution routes.