Casey Laboratory

Equilibrium constants for aqueous systems that exist deep in the earth’s crust are of great importance for chemists and geochemists. There exists a number of theoretical methods to determine equilibrium constants but remain mostly untested above pressures of 0.5 GPa. Our group is interested in using NMR as an analytical technique to determine these equilibria for these aqueous systems. In order to do so, a wide bore high pressure NMR probe was constructed for the collection of spectra at pressures up to 2.0 GPa. NMR data for 2H, 27Al, 133Cs, 139La and other broadband nuclei can be collected. Some future work to be done is the construction of a narrow bore high pressure probe and the collection of high resolution 1H data using a low field permanent magnet.

Most chemistry affecting the environment is wet chemistry, here meaning particles and ions in water.  My group works almost exclusively in aqueous solutions and on the kinetics of aqueous reactions that are important to the environment.  Our goal is a comprehensive model for predicting ligand-exchange rates for complicated structures and we therefore work closely with computational chemists to treat these reactions using dynamic methods.  In one area of research we conduct experiments at small oxide clusters that yields elementary ligand-exchange reactions to computer simulations of the same reaction.  Our primary tools are ambient and high-pressure ¹⁷O-NMR together with ESI-MS, which we use to measure the rates of substitutions to derive activation parameters at the most fundamental level of elementary or near-elementary aqueous reactions.

Science is close to being able to calculate reaction trajectories in simple aqueous systems. What is missing are experimental data on nanometer-size aqueous clusters that are sufficiently well constrained to provide test cases.  Our work on polyoxoniobates is centered around oxygen activation, as polyoxometallates serve both as models for mineral oxide surfaces.

Iron - both in heme and non-heme forms - is central to the function of redox active enzymes. We are particularily interested in the non-heme forms, seen in enzymes such as purple acid phosphatase, and are actively studying the aqueous chemistry of this type of compounds. Furthermore, ferric iron is perhaps the most important metal in the near-surface of the Earth and accounts for much of the reactivity of soil.

Conducting research at an institution like UC Davis is a valuable part of undergraduate education. The Casey Lab is a strong proponent of undergraduate research and offers many facets of study related to aqueous chemistry. Some of the most recent undergraduate research projects include synthesis and EPR studies of water oxidation catalytic models. These models help in understanding the electronic and geometric structure of amorphous catalytic materials that split water for the production of renewable energy. Other projects include stable isotopic fractionation between mineral and solution phases which is valuable information to geochemists. Studying isotopic systems leads to the important understanding of CO₂ sequestration and water-mineral interactions. Other recent research includes the synthesis and design of mineral-like layered double hydroxide structures which have important applications in solar cells and supercapacitors, to name a few. Future projects involve synthesis of new polyoxoniobate clusters for polyoxometalates. The Casey Lab has high regards for undergraduate research and continues to engage not only students from UC Davis but also undergraduate students from around the country.