Preparation of noble metal nanoparticles in supercritical carbon dioxide

Silver, palladium, and silver-palladium nanoparticles have been prepared by reduction of silver acetylacetonate and palladium acetate with dimethylamine-borane in the presence of a fluorinated surfactant (FOMBLIN HC/P2-1000) in supercritical carbon dioxide. The sizes of silver and palladium nanoparticles increases with increasing concentrations of both the soluble precursors and FOMBLIN. The size of silver nanoparticles obtained is 3-12 nm, while that of palladium nanoparticles is 3-6 nm. For preparation of silver-palladium nanoparticles, the particle size is ranged between 4 and 5 nm and dependent on the feed molar ratio of palladium acetate. It is found that silver-palladium nanoparticles consist of a core-shell structure with enriched palladium in the surface. (C) 2002 Elsevier Science B.V. All rights reserved.