NANOCOMPOSITES CONTAINING NANOCLUSTERS OF AG, CO, PT, OS, CO3C, FE2P,NI2P, GE, OR PT SO/

Neutral, low-valent complexes of transition metals or an organometalli c compound of Ge are prepared containing ancillary ligands which bear silicate ester or (alkoxy)silicon functional groups. Inclusion of thes e molecules as dopant species in a conventional sol-gel synthesis of s ilica xerogels affords silica xerogels in which dopant molecules have presumably been covalently incorporated into the xerogel matrix with u niform and high dispersion. Subsequent thermal treatment of these mole cularly doped xerogels under reducing or oxidizing/reducing conditions gives nanocomposites containing nanoclusters of metals or semiconduct or substances. Nanocomposites containing nanoclusters of Ag, Cu, Pt, O s, Co3C, Fe2P, Ni2P, or Ge have been prepared. Preliminary evidence fo r the formation of a nanocomposite containing Pt-Sn nanoclusters deriv ed from a bimetallic molecular precursor is also presented. These resu lts support the hypothesis that covalent incorporation of molecular pr ecu,aors containing low-valent metals into a silica xerogel can afford nanocluster phases with high dispersion, relatively small particle si ze, and unusual elemental composition.