Physicochemical investigation of surfactant-coated gold nanoparticles synthesized in the confined space of dry reversed micelles

Gold nanoparticle/surfactant composites have been synthesized by a novel reduction reaction in the confined space of dry sodium bis(2ethylhexyl)sulfosuccinate (AOT) or lecithin reversed micelles dispersed in n-heptane and cyclohexane, respectively. The reaction was carried out by adding an opportune amount of anhydrous hydrazine/tetrahydrofuran solution to a suspension of HAuCl4-containing dry reversed micelles dispersed in organic solvent. UV-vis investigation ascertained the formation of stable metal gold nanoparticles and the analysis of Fr-IR spectra highlighted the formation of an oriented surfactant monolayer at the nanoparticle surface. Simple evaporation under vacuum of the organic solvent leads to the preparation of very interesting gold nanoparticle/surfactant liquid crystal composites. Such nanocomposites, characterized by WAXS and SAXS, showed the presence of small (radius similar to 14 angstrom) and stable gold nanoparticles dispersed in the surfactant matrix. It has been also emphasized that a simple washing process with ethanol is a suitable method to eliminate the excess of surfactant leaving a novel nanomaterial constituted by gold nanoparticles coated by a monolayer of opportunely oriented surfactant molecules. (c) 2005 Elsevier B.V. All rights reserved.