Metal vapour synthesis of stabilized transition metal nanoparticles: characterization, studies on factors affecting particle size and catalytic applications

This PhD thesis is focused on the synthesis, characterization and evaluation of catalytic activity of stabilized platinum and gold nanoparticles, generated by use of the metal vaporization technique. Metal vapour synthesis allows to obtain platinum and gold particles with diameters in the range of few nanometers. The introduction of suitable organic molecules at various stage of the synthesis has proven to be useful in order to control the final size of the produced particles. The metal nanoparticles obtained by this new approach are very stable and can be easily handled and characterized in solution. In particular, NMR based measurement of diffusion parameters has proven to be useful for the quick determination of particles size in solution. The choice of organic stabilizing ligand is crucial in determining both the particle size and the catalytic activity and selectivity of the system. Platinum particles characterized by small diameters and good catalytic performances are obtained using vinylsiloxanes and aromatic solvents while, in the synthesis of gold particles, branched thiols and alkylamines demonstrated to be a better choices over linear alkylthiols if catalytic activity is required. A new application of gold nanoparticles in catalytic silane alcoholysis reaction has also been discovered.