Preparation of Ag/Rh and Ag/Pd Bimetallic Nano-Organized Systems by Mixing Two Kinds of Monometallic Nanoparticles

Recently, interests in the nanoscopic materials and their applications to catalyses have greatly stimulated the research on metal nanoparticles. Self-organization of nanoparticles is also one of the most interesting concepts, because it can control the structure of nano-organized systems. In this study we report the construction of bimetallic nanoparticles by mixing two kinds of monometallic nanoparticles. The mixing of colloidal dispersions of Ag nanoparticles with those of Rh nanoparticles can produce Ag/Rh bimetallic nanoparticles, in which Ag forms a core and Rh surrounds the Ag core to form a shell. Formation of the Ag-core/Rh-shell structures was confirmed by disappearance of the surface plasmon band of Ag nanoparticles and by transmission electron micrograph (TEM) observation, including distribution analyses of elements with energy filtered-TEM. Hydrogenation of olefin, catalyzed by Ag/Rh bimetallic nanoparticles, was performed in ethanol under 1 atm of hydrogen. The Ag/Rh bimetallic assemblies showed higher catalytic activity than the Rh monometallic nanoparticles did.