Dry photochemical synthesis of hydrotalcite, γ-Al2O3 and TiO2 supported gold nanoparticle catalysts

Gold nanoparticles (AuNP) supported on hydrotalcite, γ-Al2O3 and TiO2 P25 have been prepared photochemically under mild conditions using ketyl radicals as the primary reducing agent; these nanocomposites were prepared directly in the solid phase. Such dry, solventless methods are attractive from an environmental perspective. The composite materials were successfully characterized using diffuse reflectance UV–visible spectroscopy, SEM, TEM, X-ray diffraction spectroscopy (XRD) and X-ray photoelectron spectroscopy (XPS). The supported AuNP were predominantly spherical and ranged in size from 20–140 nm depending on the support and the percent Au loading, indicating the potential applications of these particles as photocatalysts. The catalytic activity of the supported AuNP was evaluated using the well-studied reduction of 4-nitrophenol. UV–visible spectroscopy was used to monitor the reaction and illustrated the ability of these easily prepared AuNP composites to act has heterogeneous catalysts. The role of percent Au loading and type of support on the catalytic activity of supported AuNP was also investigated. Composites with relatively large AuNP may hold promise as efficient catalysts in plasmon-mediated light-driven reactions.