A solventless mix–bake–wash approach to the facile controlled synthesis of core–shell and alloy Ag–Cu bimetallic nanoparticles

We report a solventless mix–bake–wash method for the facile controlled synthesis of Ag–Cu core–shell and alloy bimetallic nanoparticles (NPs). Small bimetallic nanomaterials were prepared by a one-step heating process using salt powder as a template. The particle structure could be controlled by tuning the annealing temperature to generate hetero-structured core–shell NPs or homogeneous alloys. The NPs' bimetallic structure and elemental composition were characterized by HR-TEM, FE-SEM, EDX, HADDF-STEM, XRD and XPS. Whereas the as-synthesized Ag@Cu core–shell NPs consist of a core of face-centered cubic (fcc) polycrystalline Ag NPs and a shell of fcc Cu including trace amounts of copper oxides, the AgCu nanoalloy was found to comprise a single-phase NP with the same crystal structure as that of Ag, without the copper oxide species. Cyclic voltammetric measurements confirmed the chemical identification of the surface species and their stability to oxidation. This synthesis approach is facile, structure-controllable, and scalable, and is expected to be capable of producing other bimetallic or trimetallic nanomaterials.