PREPARATION FROM ORGANOMETALLIC PRECURSORS, CHARACTERIZATION AND SOMEREACTIVITY OF COPPER AND GOLD COLLOIDS STERICALLY PROTECTED BY NITROCELLULOSE, POLYVINYLPYRROLIDONE OR POLYDIMETHYL PHENYLENE OXIDE

Decomposition of the organometallic precursor CpCu(Bu(t)NC) by CO (1 o r 3 atm) at room temperature in the presence of polyvinylpyrrolidone ( PVP) in CH2Cl2 or polydimethylphenylene oxide (PPO) in anisole leads t o the formation of colloidal copper. ESCA analysis demonstrates the re duction to metallic copper, whereas under the same conditions but usin g nitrocellulose (NC) particles of CuO are formed. The particle sizes were measured by TEM and found to be near 35 Angstrom for Cu/PPO at 5 wt.% metal/polymer, 50 Angstrom for Cu/PPO at 15 wt.% and 60 Angstrom for Cu/PVP (2.5 or 5 wt.%). The colloidal copper does not adsorb CO, b ut it reacts with air to give large hexagonal polycrystals containing Cu2O and some Cu metal as revealed by electron diffraction. A similar reaction for AUCl(THT) (THT = tetrahydrothiophene) under 1 or 3 bars o f CO or H-2 in the presence of PVP or NC leads to stable gold colloids containing up to 25 wt.% gold/polymer. In PVP, a mean size of 15 a wi th a low size dispersity was found for Au/PVP 5 wt.% whereas larger pa rticles are found (ca. 30 Angstrom) for Au/PVP 25 wt.%. In NC a higher range was found in the size and morphology of the particles. The coll oidal gold and copper sols were characterized by TEM and optical spect roscopy.