Gold-nanocluster-doped inorganic-organic hybrid coatings on polycarbonate and isolation of shaped gold microcrystals from the coating sol

Au-nanocluster-doped inorganic-organic hybrid coatings on polycarbonate sub strates were prepared for the application of abrasion-resistant colored coa tings as well as nonlinear optical material. The Au-doped sol was prepared by incorporating HAuCl(4)(.)4H(2)O into a composite sol derived from 3-(gly cidoxypropyl)trimethoxysilane, tetraethylorthosilicate, and 3-(methacryloxy propyl)trimethoxysilane via hydrolysis-condensation and epoxy polymerizatio n reactions. When the coated substrates were exposed under UV light, three reactions occurred simultaneously: (i) reduction of Au ions into metallic A u nanoclusters, (ii) polymerization of methacrylate groups, and (iii) stren gthening of the silica network. As a result, the UV-cured coatings became r eddish-purple and more abrasion-resistant than the polycarbonate substrate. W-vis spectroscopy and TEM of the films showed a peak at 530 nm due to the surface plasmon resonance of Au nanoclusters and the presence of 8-10 nm s pherical Au nanoclusters, respectively. XRD of the films also showed the ch aracteristic peaks of metallic Au nanoclusters. The inorganic-organic hybri d network at the sol stage also acted as a new breeding medium for the gene ration of shaped (triangular, hexagonal, prismatic, etc.) Au microcrystals from the Au-doped sol without W irradiation. Electron diffraction suggests that these were single crystals with a preferential growth along the Au (11 1) plane.