PREPARATION OF GOLD MICROCRYSTAL-DOPED OXIDE OPTICAL COATINGS THROUGHADSORPTION OF TETRACHLOROAURATE IONS ON GEL FILMS

Transparent oxide films containing gold microcrystals for non-linear o ptics are prepared by a new sol-gel process, in which dip-coated gel f ilms prepared from metal alkoxide solutions are immersed in NaAuCl4 . 2H(2)O aqueous solution and subsequently heat-treated. AuCl4- ions can be incorporated in alumina and titania gel films and thus gold crysta ls in the films can be formed. On the other hand, the ions are poorly incorporated in zirconia gel and not incorporated in silica gel. This difference is explained by the point of zero charge of these gels. Inc rease of the concentration of NaAuCl4 . 2H(2)O aqueous solution is not effective in increasing the amount of gold incorporated in the gels. (C) 1997 Elsevier Science B.V.