Wednesday, November 4, 2009: 8:50 AM
Charolais (Camino Real Hotel)
The need to understand the physico-chemical functions of solid catalysts down to single nanocrystal level are of great importance not only to elucidate which changes—atomic, molecular, or nanoparticulate— take place along the course of catalytic turnover, but also to devise novel, superior catalysts. Monochromatic beams of electrons and electron-optical assemblies with very low coefficients of spherical-aberration enable atomic-resolution in High-Resolution Transmission Electron Microscopy (HRTEM) and Scanning-TEM (HRSTEM), for advanced characterization of homogeneous and heterogeneous catalysts. Both of these techniques hold the key for understanding structure (in sub-Angstrom detail), crystallographic phase, chemical composition, morphology and oxidation states of constituent chemical elements. The work herein described presents the structure and morphology of Au/Pd bimetallic particles, displaying a three-layer core/shell configuration. Our findings indicate that the surface layer of these nanoparticles contains kinks, terraces and steps at the nanoscale. The effect of adding a second metal induces the formation of such defects, which might affect the catalytic activity of this system. Biologically-inspired catalysts have also been analyzed. Platinum nanoparticles stabilized by a protein, bovine serum albumin, were successfully synthesized with two different morphologies, cuboctahedra and nanorods. These nanoparticles have been applied as catalysts for the hydrogenation of allyl alcohol in aqueous solution.