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Davis Research Group
Fundamental Laboratory Studies of Microenvironments
Overview: The Davis Research Group utilizes elements of chemistry, physics, engineering, and computer science to develop advanced analytical techniques to study the unique properties of microenvironments and address science questions relevant to atmospheric chemistry, sustainability, climate, human health and indoor air quality. Microenvironments are ubiquitous in nature and science. Examples include biological cells and atmospheric aerosols. Understanding the chemistry and physics occurring in these small, isolated compartments is essential to understanding human health and global climate, among other things. From the sea to the atmosphere to our bodies, these microscopic environments influence our daily lives in ways yet to be understood. Our research aims to increase our understanding of micro-environmental properties to increase our understanding of the world and how we can improve it.
Outcomes: In the Davis Research Group, there will be ample opportunities for students to develop instrumental techniques, design and build control electronics, write and develop software, perform experiments, process data, and present their work through presentations and publications.
Marine polysaccharides are known to self-assemble into ordered aggregates, such as polymer gels, at the ocean surface. Recently, marine polymer gels have also been observed in cloud/fog droplets. Due to their dense, compact nature, self-assembled gels in atmospheric particles are speculated to change the microstructural properties and chemical reactivity of that particle. However, these points remain largely unexplored. One initial project within my research group will study self-assembly of polymer material under the complex conditions relevant to the atmosphere, thus advancing fundamental physical chemistry knowledge and constraining important properties relevant to atmospheric science in terms of understanding air quality and climate.
To date, bridging the gap between atmospheric models and atmospheric observations has proven difficult. This difficulty is largely due to the extreme chemical complexity of atmospheric particles and the unique but poorly understood properties of microenvironments. In the Davis Research Group, there are opportunities to study how these unique microdroplet properties lead to unique chemistry that cannot be replicated through “beaker synthesis”. One example includes studying the production of reactive oxygen species (ROS), including hydroxyl radical production under atmospheric conditions, as shown in image to the right.
We spend the majority of our time inside a building. However, less is known about indoor air chemistry than the chemistry occurring in the outdoor environment. A recent research push has led to an explosion of information about indoor air quality, but there is much research to be done. In the Davis Research Group, there will be opportunities to pursue research related to indoor air quality in the workspace, studying the types of particulate generated under “blue-collar” labor conditions.
Physical and Chemical Properties of Nanoparticle Metal Catalysts
Focus: Physical Chemistry
Professor: Christopher Pursell, Ph.D.
Overview: Fundamental studies of the unique physical and chemical properties of metal nanoparticle catalysts are an important area of scientific research. An important aspect of these catalysts concerns the interaction of the metal nanoparticles with the underlying support. This is especially true for reducible metal oxide supports. The literature contains a number of examples that demonstrate how electronic metal – support interactions (EMSI) between metal nanoparticles and the support material are very important as they control electronic transfer and catalytic transformations that occur at the catalytic active site.
Understanding the mechanisms that control charge transfer and the activation of reactive species at specific sites can therefore aid in the design of more efficient and selective catalysts. Research in our laboratory therefore concerns fundamental EMSI studies examining adsorbate-induced charge transfer: from adsorbate to metal nanoparticle to the support.
Outcomes: Our research goals are: (1) to provide a deeper understanding of electronic metal – support interactions for these catalysts; and (2) to develop greater knowledge of the mechanism associated with hydrogen adsorption and dissociation, including hydrogen spillover. The ultimate outcome of these studies will be the further development of our understanding of metal nanoparticle catalysts.
Projects: Previously students in our laboratory discovered that chemisorption of carbon monoxide on the gold nanoparticles causes electronic transfer from the gold to the titania support, leading to the reduction of the titania. This caused the transmission of infrared light through the catalyst to decrease (due to light scattering) as the surface of the titania roughened. More recently students discovered the same phenomena with the adsorption of hydrogen on gold catalysts. Through systematic laboratory experimentation utilizing infrared spectroscopy, we will be conducting a thorough investigation of this interesting metal-to-support electronic interaction. This work will provide a greater understanding of catalytic reactions involving hydrogen, along with a better understanding of the importance of metal – support electronic interactions in gold catalysts.