Sarip, R; (2012) Gold Molecular Clusters to Nanoparticles : A Bottom-up Approach to Supported Nanoparticles for Heterogeneous Catalysis. Doctoral thesis , UCL (University College London).

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Abstract

This thesis covers a number of different aspects of chemistry including molecular inorganic chemistry, nanochemistry and heterogeneous catalysis. The key aspect of our research is a bottom-up approach towards generating gold nano-particulate heterogeneous catalysts. Two phosphine-stabilised gold clusters containing Au9 and Au13 cores were prepared and used as molecular precursors to tailor specific size of gold nanoparticles. A number of techniques were employed to characterise the clusters as well as the catalysts in order to follow the nano-particulate creation. The conventional incipient wetness impregnation (WI) method was used to deposit clusters onto SiO2 nanosphere and Al2O3 supports followed by high temperature calcination (300°C and 500°C) for catalyst activation. A highlight of this thesis is the development of the tert-butyl hydroperoxide (TBHP) assisted deposition-precipitation method towards producing smaller size of gold nano-particulate catalysts. Catalyst activation at relatively low temperatures (95°C) via the TBHP method minimised gold agglomeration, gold nanoparticles obtained by this method being < 10 nm in diameter. The relationship between catalytic activity and the size of clusters used as well as the catalyst preparation method (WI vs TBHP) was studied by liquid phase oxidation of benzyl alcohol. Higher turnover frequencies (TOF) were observed employing catalysts prepared via the TBHP method and proved to be recyclable up to at least six times with only minimal decrease in catalytic performance. Attempts had also been made to synthesise heterobimetallic gold-metal catalysts containing palladium and tin. The synthesis, characterisation and catalytic activity of both heterobimetallic catalysts are also reported.

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