Abstract

Reduction of two different precious metal ions by refluxing in ethanol/water in the presence of poly(N-vinyl-2-pyrrolidone) (PVP) gave a colloidal dispersion of core/shell structured bimetallic nanoparticles. In the case of Pd and Au ions, for example, the colloidal dispersions of bimetallic nanoparticles with a Au core/Pd shell structure are produced. In contrast, it is difficult to synthesize bimetallic nanoparticles with the inverted core/shell (in this case, Pd core/Au shell) structure. Here the sacrificial hydrogen strategy has been used to construct the inverted core/shell structure, where the colloidal dispersions of Pd cores are treated with hydrogen and then the solution of the second element, Au ions, is slowly added to the dispersions. This novel method, developed by us, gave the inverted core/shell structured bimetallic nanoparticles. The Pd core/Au shell structure has been confirmed by FT-IR spectra of adsorbed carbon monoxide. The hydrogenation of methyl acrylate catalyzed by the nanoparticles before and after heat treatment was investigated as well.