Thursday, 13 February, 2014
UT Host: Dr. Craig Barnes
Speaker: Dr. Robert Rioux - Pennsylvania State University
Title: "Single Molecule Investigations of Heterogeneous Catalysts: Probing Solvent Effects, Adsorbate Dynamics Active Site Heterogeneity"
Abstract: Metal nanoparticles are key components in the advancement of future energy technologies since they are catalytically active for several organic-inorganic syntheses, electron-transfer, and energy conversion reactions. They directly promote chemical conversion and/or facilitate chemical transport to active interfaces. A detailed understanding of the relation between structure and properties of nanoparticles will lead to tailored catalytic properties. Although these structure-function relationships are pursued by many researchers; they are typically limited to ensemble-level approaches where the intrinsic catalytic behavior of individuals is masked due to the asynchronicity of their behaviors during catalytic turnover. We employ a single molecule approach utilizing a two-state (pro-fluorescent to fluorescent) reduction reaction to examine the catalytic behavior of individual Au nanoparticles with single turnover resolution. Through kinetic modeling and isotopic labeling, we demonstrate competitive binding between solvent and substrate accounts for differences in observed catalytic rates at the ensemble level. Temperature-dependent measurements of the catalytic activity of single nanoparticles reveals heterogeneous in reactivity and kinetic parameters which are due to static dispersion even though the dispersion varies temporally; these variations are ascribed to the intrinsic reactivity of populations of indistinguishable active sites. Approaches to selectively titrate distinct active site populations on the surface of individual Au nanoparticles have enabled us to distinguish between their intrinsic kinetic behavior and utilizing ideal models of nanoparticle structures confirm their identity and concentration. The ability to probe reaction dynamics during single molecule catalysis studies utilizing an experimental and theoretical approach to understand delayed rise times in fluorescent response will be discussed time permitting.
Seminar is not web cast.
Visit https://www.chem.utk.edu/seminars-programs/departmental-seminar to view the Chemistry seminar schedule & get directions to view the web cast.