The preparation of gold nanoparticle composites using supercritical carbon dioxide

In this paper we present the synthesis of gold nanoparticles supported on silica using supercritical carbon dioxide (scCO2). Average gold particle sizes ranged from 3.7 to 6.6 nm. We also demonstrate the flexibility of this supercritical fluid processing technique by successfully incorporating gold nanoparticles into polyamide, polypropylene and poly(tetrafluoroethylene) (PTFE). Under the conditions employed, it was found that dimethylacetylacetonato gold(III) (Au(acac)Me2) produced samples with sufficiently high metal loadings which allowed in-depth sample analysis. Surprisingly, the fluorinated analogue, dimethylhexafluoroacetylacetonato gold(III) (Au(hfac)Me2) did not yield samples suitable for characterisation. X-ray diffraction (XRD), transmission electron microscopy (TEM) and solid-state UV–vis were applied to determine average particle sizes and to confirm the nature of the metallic particles obtained. To date, scCO2 processing is the only method known to us capable of both depositing and impregnating a wide range of substrates with gold nanoparticles.