Research: Science Beyond Category
From Fundamental Physical Chemistry to Applied Atmospheric Science
Microenvironments: The Overarching Scope
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. Synthetic nanoparticles are becoming increasingly utilized in a wide range of applications. How these nanoparticles influence chemistry in the environment and in our bodies is unclear and thus an important area of research as more people are exposed to these tiny pieces of matter. Interfaces (the place where two phases meet) are microenvironments that can spread over a wide surface area.
In this sense, the sea surface microlayer, or the topmost layer of the ocean, is perhaps the largest microenvironment, forming a semi-continuous web of interfacial material across 70% of the globe. 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.
Experimental Approaches: Levitation and Contactless Microfluidics
Studying microenvironments requires specialized approaches. My research utilizes particle levitation (both optical and electrostatic) and contactless microfluidics to isolate small microvolumes for study with spectroscopy and mass spectrometry. A necessary by-product of our research is the development of new experimental and instrumental techniques that are suited for studying microenvironments. Examples include the development of:
- New levitation techniques for isolating small particles more easily
- Surface-sensitive spectroscopic techniques to study levitated particles
- Contactless microfluidics that reduce consumption of reagents and facilitate novel chemistry
- Computer programs that extract the maximum amount of information from cost-effective imaging techniques such as laser light scatter imaging
- Mass spectrometric techniques to study aqueous-phase aerosol chemical kinetics and products.
Physical Transformations: Nucleation and Self-Assembly
Nucleation is one of the most fundamentally important processes in science. Crystal nucleation and growth from a liquid solution (i.e., crystallization) is of particular importance due to its widespread relevance in atmospheric science, pharmaceuticals, biology, architectural preservation, and many other applications where the overarching goals are to predict, control, inhibit and/or reverse nucleation. In atmospheric science, crystallization of an aqueous particle alters the particle’s effect on air quality and climate through impacts on heterogeneous chemical reactivity and optical properties of the particle. In pharmaceuticals, tight control of nucleation is essential because the crystalline form of a particular medication often dictates its bioavailability and efficacy. In many soft matter applications, inhibiting the formation of crystals is necessary to maintain the desired material properties. In biology, the formation of protein crystals or other crystal-like aggregates underlies multiple health concerns. Amazingly, despite this widespread importance, there is no comprehensive understanding of crystal nucleation. Included in our research focus is the goal to develop a more comprehensive understanding of crystal nucleation.
Crystallization is not the only possible fate of a liquid. For example, proteins and some simple inorganics can instead form self-assembled polymer aggregates and gels. One particular exciting and emerging area of research involves self-assembled marine polymer gels formed from dissolved organic carbon in sea water. Recently, marine gels have been detected in atmospheric particles, as well. These airborne gels have been proposed as important sources of cloud condensation nuclei when emitted into the atmosphere along with sea spray aerosol.
Chemical Transformations: Production of Reactive Oxygen Species
The formation of reactive oxygen species (ROS) is of growing interest and concern in atmospheric chemistry and biophysical processes. In the atmosphere, the formation of ROS is a driver of atmospheric chemistry, particularly in clouds/fog droplets in urban environments, such as that shown in the image below. In the human body, the formation of ROS is known to be damaging and thought to be linked to cancer. However, the processes that lead to ROS formation are currently not understood. Our research aims to bring a greater understanding of ROS production and the effects such reactive species have in the environment and the human body.
Green Chemistry: Sustainable Innovation
A new direction in the Davis Group is toward green chemistry practices. Our research focus in sustainable "green chemistry" is to reduce the global impact of scientific research and education by developing novel micro-devices that minimize waste and consumption of reagents and by utilizing the unique properties of microdroplets to facilitate chemical reactions in benign solvents such as water. As the innovation economy grows, so does its environmental footprint. In the Davis Group, we hope to reduce that footprint for a sustainable future