SYNTHESIS, PROPERTIES, AND CHARACTERIZATION OF NANOMETER-SIZE METAL PARTICLES BY HOMOGENEOUS REDUCTION WITH ALKALIDES AND ELECTRIDES IN APROTIC-SOLVENTS

A new method for the preparation of small metal/oxidized metal particles is described that utilizes homogeneous reduction of metal salts by dissolved alkalides or electrides in an aprotic solvent such as dimethyl ether or tetrahydrofuran. Soluble compounds of transition metals and post-transition metals in dimethyl ether or tetrahydrofuran were rapidly reduced at -50-degrees-C by dissolved alkalides or electrides to produce metal particles with crystallite sizes from <3 to 15 nm. The products were characterized by X-ray photoelectron spectroscopy. Confirmation by electron diffraction was made in the case of air-stable samples. The average particle size was estimated from powder X-ray diffraction line broadening. Particle size distributions were determined by counting the particles on electron micrographs obtained by transmission electron microscopy. Salts of Au, Cu, Te, and Pt formed metallic particles with little or no oxidation even when washed with degassed methanol. Reduction of salts of Ni, Zn, Ga, Mo, Sn, and Sb yielded surface oxidation over a metallic core. Stoichiometric amounts of the alkalide or electride were used; these were prepared either separately or in situ. FT-IR spectroscopy was used to demonstrate the presence of organic decomposition products on the surface of the metal particles. This method is also applicable to the formation of finely divided metals on oxide supports.