Synthesis, stabilization, and applications of nanoscopic siloxane-metal particle conjugates

This account reports the new directions in the synthesis and characterization of polysiloxane-encapsulated metal nanoparticles and their applications to catalysis. These materials are prepared by sequestering metal ions with hydropolysiloxanes followed by chemical reduction to yield the corresponding zerovalent metal nanoparticles. The size and processability of such particles depends on the metal to polysiloxane ratios. Our method enables routine formation of stable nanometallic reservoirs in organic solvents avoiding particle aggregation during the storage as well as nucleation and growth process. Catalytic activity of nanoparticles vs metal complexes compares favorably for silaesterification reactions. We also demonstrate the utility of such reservoirs in grafting the surface properties of nanosized silver particles by ligand exchange reactions with thiols and phosphine oxide surfactants. (C) 2003 Elsevier B.V. All rights reserved.