Dispersion of Gold Nanoparticles into a New Polymeric Matrix

I. E. DELL'ERBA, C.E. HOPPE AND R. J. J. WILLIAMS

San José

Simposio; XII Simposio Latinoamericano de Polímeros; 2010

Gold nanoparticles (NPs) are of interest because of their high chemical stability, and their catalytic, electronic and optical properties. Nanostructured materials with new functional properties may be obtained by the dispersion of gold nanoparticles into polymers. In this work we show the synthesis of a novel crosslinked polymer obtained by hydrolytic condensation of a high functionality silane, and the further modification of this polymer with gold nanoparticles. A high functionality silane monomer was prepared by reacting glycerine with 3-isocyanate propyl triethoxysilane (IPTES). Molar relation between reactants can be varied in the range 0<IPTES/Gly<3, thus varying the functionality of the monomer (i.e. nine reactive groups per molecule for the highest molar relation). Reaction was carried out at 50ºC with 0,5 wt% dibutyl tin dilaureate (DBTDL) as a catalyst, attaining complete reaction in 3 h. These monomers were crosslinked by hydrolytic condensation of silane groups. Water slightly acidified with HCOOH (pH = 4) was added up to molar relation H2O / Si = 3, and reaction was carried out at 50ºC for 3 days in an open container, allowing continuous evaporation of volatiles. Homogeneous colorless products were obtained, with crosslinking densities depending on the molar relation IPTES/Gly. OH-functionalized gold nanoparticles were prepared by a modified Brust-Schiffrin method[1], using 6-mercapto-1-hexanol (MCH) as a surfactant. HAuCl4 was transferred from an aqueous to a toluene solution using tetraoctylammonium bromide (TOAB) as a phase transfer agent, then MCH was added up to the desired S/Au relation and finally, Au@MCH nanoparticles were obtained by reduction with an aqueous solution of NaBH4 at 0ºC. Au NPs can be stored as stable dispersions using N,N-dimethylformamyde (DMF) as a solvent. UV-Visible spectra performed on DMF dispersions of Au@MCH NPs showed a weak absorption band centered around 520 nm, which can be ascribed to NPs smaller than 2 nm in diameter These monomers were crosslinked by hydrolytic condensation of silane groups. Water slightly acidified with HCOOH (pH = 4) was added up to molar relation H2O / Si = 3, and reaction was carried out at 50ºC for 3 days in an open container, allowing continuous evaporation of volatiles. Homogeneous colorless products were obtained, with crosslinking densities depending on the molar relation IPTES/Gly. OH-functionalized gold nanoparticles were prepared by a modified Brust-Schiffrin method[1], using 6-mercapto-1-hexanol (MCH) as a surfactant. HAuCl4 was transferred from an aqueous to a toluene solution using tetraoctylammonium bromide (TOAB) as a phase transfer agent, then MCH was added up to the desired S/Au relation and finally, Au@MCH nanoparticles were obtained by reduction with an aqueous solution of NaBH4 at 0ºC. Au NPs can be stored as stable dispersions using N,N-dimethylformamyde (DMF) as a solvent. UV-Visible spectra performed on DMF dispersions of Au@MCH NPs showed a weak absorption band centered around 520 nm, which can be ascribed to NPs smaller than 2 nm in diameter