| A new method for the preparation of small metal/oxidized metal or alloy particles and reduction in zeolite pores 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 are rapidly reduced at {dollar}-30spcirc{dollar}C by dissolved alkalides or electrides to produce metal particles with crystallite sizes from {dollar}<{dollar}3 to 15 nm. The average particle size was estimated from the line broadening of powder X-ray diffraction. Particle size distributions were determined by counting the particles on electron micrographs obtained by transmission electron microscopy. Salts of Au, Pt, Cu, Te, Fe, and Ta formed metallic particles with little or no oxidation even when washed with methanol or liquid ammonia. Reduction of salts of Ni, Fe, Zn, Ga, Si, Mo, W, In, Sn, and Sb yields surface oxidation over a metallic core. This method is also applicable to the formation of finely divided metals on oxide supports.; Alloys or intermetallic compounds formed when two different metal salts were used, as indicated by X-ray photoelectron spectroscopy. Confirmation by electron diffraction was made in the case of air-stable samples. Reduction of salts of Au-Cu, Au-Zn, Cu-Te, Zn-Te, Au-Ti, Fe-Ta formed particles that contained intermetallic compounds.; Stoichiometric amounts of the alkalide or electride were used; these were prepared separately or in situ. FT-IR spectroscopy was used to demonstrate that the presence of organic complexants and solvents often resulted in the inclusion of organic decomposition products due to the high reactivity of nanoscale metal particles. Elemental analysis showed that both carbon and hydrogen were less than one percent in atomic concentration on the surface of gold.; Electrides, the most powerful reducing agents, were used to reduce Cu{dollar}sp{lcub}2+{rcub},{dollar} Pd{dollar}sp{lcub}2+{rcub},{dollar} Ag{dollar}sp+{dollar} in zeolite-Y. X-ray photoelectron spectroscopy data show that these cations were completely reduced to the zero oxidation state at {dollar}-30spcirc{dollar}C. Cu and Pd remain trapped in the interior and an alkali metal cation balances the counter charge upon reduction. In contrast, Ag formed 40 A diameter particles uniformly on the external surface. This method should also be applicable to the synthesis of organometallic compounds. |
