The fundamental force driving my research is the desire to understand the chemistry of the natural world (i.e. the environment). This includes the chemistry of both ‘natural’ and ‘unnatural’ species. My initial research consisted of applied studies of the pollution of natural waters. For my graduate career, I decided to take a first principles approach to environmental work by studying the physics and chemistry of clusters of atoms and molecules. My current and future work aims to unite my interests in pure chemical physics and applied environmental chemistry. I believe that a bottom up method is the correct approach to the complicated chemistry of the natural world. My unique skills as an experimentalist, theoretician, and as a designer and builder of scientific instruments affords me the opportunity to approach the questions of the environment in a new way.
Past Research
Undergraduate:
In 2000, I worked with Dr. Patrick Brezonik at the University of Minnesota Department of Water Resources Science. My research focused on the ability of alum (Al2(SO4)3·24H2O) to remove bio-available phosphorus from urban ponds. The excess phosphorus causes lethal algal blooms. The work involved field studies at local ponds with pilot installations of alum injection systems. Analysis of the effectiveness was performed by quantization of the levels of chlorophyll present in the treated waters (both natural and laboratory samples).
In 2002-2003, I began a research collaboration with the group of Dr. Glen R. Boyd at Tulane University in cooperation with the Tulane Center for Bioenvironmental Research. Dr. Boyd’s group was on the cutting edge of the national push to analyze the levels of pharmaceuticals and personal care products (PPCPs) in natural waters. They had found that Naproxen ((+)-(S)-2-(6-methoxynaphthalen-2-yl) propanoic acid) was present in nearly sample drawn from the Mississippi River Delta as well as Lake Ponchartrain. The levels of contamination were on the parts per trillion level (ppt), but work had already shown that ppt concentrations of hormones can seriously affect aquatic organisms. My work investigated the ability of powdered activated carbon (PAC) to remove Naproxen during a simulated drinking water treatment scenario. It was determined that the PAS was effective, but only with contact times much greater than found in most drinking water facilities. Furthermore, HPLC-MS analysis showed that contact with hypochlorite yielded a multitude of disinfection byproducts.
Graduate:
In 2003, I began my M.A. / Ph.D. work with Dr. Kit Bowen at the Johns Hopkins University in Baltimore, MD. His work focuses on the study of molecular and atomic clusters. My dissertation presented new work on he hydration of hydrophibic and hydrophillic molecules as well as the behavior of acid-base pairs in the gas phase.
Clusters are generated by a supersonic expansion from pressures of 1+ atmospheres to near vacuum (10-6 torr). The rapid expansion causes extreme cooling and subsequent condensation into clusters of all sizes. Modifying the conditions and starting mixtures allows one to obtain clusters of nearly any composition. Using this method, I investigated the electronic structure of intact molecular clusters of the form (x)(H2O)n-, where x is the solute of interest. By generating molecular beams of intact, solvated, anionic molecules physical parameters such as enthalpy of hydration, electron affinity, extend of dissociation (for acidic species), and even molecular structure via comparison with theoretical models.
Through this work I became interested in the possibility of ab initio theoretical methods to compliment experimental work. In collaboration with theoretical groups throughout the world I became proficient in the use of MP2, CCSD, DFT, and other methods for prediction of electron affinities as well other physiochemical parameters including molecular and electronic structure. Through my work in the Bowen Group I became skilled in experimental design and technique, theoretical methods, as well as scientific instrument design and fabrication.
Postdoctoral:
Currently I am working with Dr. Kristopher McNeill at the Eidgenössische Technische Hochschule (aka ETH or the Swiss Federal Institute of Technology). I am in the process of setting up a femtosecond transient absorption experiment to probe the lifetimes of photochemically active species. The work will investigate how different environmentally relevant compounds undergo direct photolysis or indirect photolysis via excited state energy transfer involving natural organic matter (NOM). Additional studies will probe the reactivity of the hydrated electron with pollutants in natural water matrices. In addition to the femtosecond laser experiments, I am developing a reliable theoretical protocol to evaluate the excited state geometries and energies using time dependant density functional theory (TD-DFT).
Future Research:
I am strongly motivated to move forward into an academic career which focuses on vigorous fundamental and applied research. My future work will focus on the process of solvation and its effect on the nature of environmental chemical and photochemical processes. I envision a four-pronged approach:
- Studies of gas phase pollutants
- Molecular beam experiments on environmentally relevant species (ERS)
- Reactions with reactive oxygen species (ROS) (i.e. O3, singlet O2)
- Interaction with UV/Vis photons
- Probes
- Photoelectron spectroscopy (PES) / Time resolved PES
- Raman and IR spectroscopy
- Mass selection (QMS, TOF)
- Ion trap spectroscopy
- Studies of intermediate states
- Molecular beam experiments of solvated (ERS)
- Effect of solvation on physical/electronic/optical properties
- Molecular beam experiments of binary systems
- Triplet energy donor paired with energy acceptor
- Monitor triplet state reactions
- ROS-ERS pairs
- Kinetics of ROS reaction with ERS
- Aerosols
- Optical properties of aerosols
- Radiative forcing and climate change issues
- Mass-spectrometric analysis of aerosols
- Studies of bulk systems
- Natural waters and natural water mimics
- Laser flash photolysis (fs/ns) studies of pollutants reacting with NOM and generated ROS
- Investigations of air water interfaces
- Chamber studies of known atmospheres interacting with pure H2O
- SFG analysis
- IR (gas and liquid)
- Raman
- Computational chemistry
- Using ab initio and DFT methods to predict and supplement experimental results
- High level ab initio calculations on gas-phase systems
- Addition of implicit and explicit solvent models
- Prediction of photochemical processes
- TD-DFT optimization and vertical energies for singlet and triplet excited states
- IR and Raman spectral simulations