Day: March 9, 2015

Exploring environmentally relevant aqueous interfaces and reactions on solid surfaces

Chemistry Department Seminar Faculty Candidate
Dr. Kathryn A. Perrine

Department of Chemistry, University of California Irvine
Monday March 16, 2015
Chem-Sci 101
4:00 pm

Abstract:

Ions and solutes impact chemistry at the aqueous liquid/vapor interface, particularly in environmental chemistry where aerosols can carry pollutants into the atmosphere and react to form harmful byproducts. Liquid Jet X-ray Photoelectron Spectroscopy technique probes the surface and bulk of aqueous solutions. Low photoelectron kinetic energies are used to probe the surface layers of solutions and higher photoelectron kinetic energies probe deeper into the bulk of aqueous solutions. Binary acetonitrile-water mixtures are shown to be inhomogeneous and that the surface forms a saturated dipole layer near 0.2 mole fraction. These studies are contrasted to ternary solutions that have added ions from salts that affect the interface of organic solutes. Potassium iodide was added to aqueous acetonitrile and propionitrile solutions to observe the effects of ions on the surface nitrile distributions. Results from other salt solutions suggest specific cation effects are unexpected and apparent at the aqueous interface. These studies help elucidate the role ions play at the interface of aqueous organic solutions.

Solid interfaces can also have an impact on reactions in catalysis and in the environment. Supported metal oxide structures that are commonly found in urban and rural environments can produce various byproducts with pollutants through core-hole activation in the presence of UV and visible light. In order to understand how the interface is impacted on heterogeneous surfaces, thermal desorption studies of water on different heterogeneous structured TiO2 materials were investigated. Results suggest as the size of the metal oxide decreases, its physical properties change its chemistry and reactivity. Monolayer and second layer activation energies of water were determined on different graphite supported TiO2 structures, ranging from supported nanoparticles to thin films. These studies compare the reactivity of small molecules, representative of those in the air/water environment, and will help explain gas/solid reactions on heterogeneous supported metal oxide materials for catalysis and environmental applications.

Biosketch:
Dr. Kathryn A. Perrine found a passion for surface science as an undergraduate student at the University of South Carolina, where she worked on characterizing the decomposition of metal encapsulated dendrimers for supported metal catalysis applications. She then attended graduate school and earned her PhD at the University of Delaware, where she studied semiconductor surface science. Her work there focused on understanding how Cu nanostructures grow on different functionalized silicon surfaces from chemical vapor deposition of copper metal-organic precursors. She also collaborated with researchers at the Materials Science Department to examine how organic molecules react on silicon for future use in organic electronics. There she won the competitive University of Delaware Professional Development Award for her research accomplishments. She also completed a full year in teaching in higher education by completing the Higher Education Teaching Certification.

She later went on to do postdoctoral work at the University of California, Irvine mainly focused on Liquid-Jet X-ray Photoelectron Spectroscopy (LJ-XPS). She collaborated with researchers at the BESSY II light source at the Helmholtz Center for Materials and Energy on aqueous and acidic systems. She helped build a separate LJ-XPS system at Beam line 11.0.2 end station at the Advanced Light Source at Lawrence Berkeley National Laboratory to continue aqueous liquid jet studies in a higher pressure environment. She collaborated with others in the Hemminger group to investigate other projects, including hydrocarbon decomposition on supported Pt nanoparticles and understanding the reactivity of supported TiO2 materials for heterogeneous catalysis applications. There she was a member of the Postdoctoral association and received the UCI postdoctoral service award for developing a seminar series for postdoctoral teaching. She currently works as a visiting postdoctoral scholar at the Joint Center for Photosynthesis at the California Institute of Technology on heterogeneous catalysts for electrochemical solar energy conversion.

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