(2gi) The Signal in the Noise: Fluctuations in Interfacial Chemistry, Quantum Molecular Machines and Photosynthesis

From chemical reactions driven by thermal fluctuations to photosynthetic light harvesting excited by sunlight, chemistry is defined by the study of noise driven molecular processes. My research applies the modern theory of statistical mechanics and quantum dynamics alongside computational molecular models to understand how seemingly random noise can reliably produce specific outcomes and how we can harness these insights to:

1. optimize chemical reactions near interfaces,
2. design quantum molecular machines that use quantum interference to exceed classical performance bound, and
3. understand the molecular mechanisms plants employ to regulate photosynthetic light harvesting.

(1) Chemical reactions in liquids couple strongly to the fluctuations of the solvent. The presence of the reactants constrains these fluctuations leading to a solvent-induced entropic driving force on the reaction. The presence of an interface breaks the symmetry of the solvent, modifying its fluctuations and therefore the entropic driving force on reactions near the interface. My research will apply molecular dynamics simulations alongside recent developments in liquid state theory to describe how the interface-modified solvent fluctuations alter reaction thermodynamics and how we can engineer the structure and composition of the interface and solvent to optimize reaction outcomes. These insights will be applied to electrochemistry at nano-structured electrodes, atmospherically relevant aerosol chemistry and the self assembly of membrane-bound proteins.

(2) A growing body of theoretical work has demonstrated that when sunlight strikes a molecule, it excites specific quantum superposition states. This superposition leads to room temperature quantum interference that can alter the subsequent photochemistry and energy and charge transfer pathways, breaking classical limits on efficiency, quantum yield and maximum power output. These studies suggest the tantalizing possibility of molecular machines that harness quantum mechanics for improved performance. My research will focus on designing two classes of experimentally realizable quantum molecular machines. The first class consists of molecular dyes held in specific configurations by a synthetic DNA or protein scaffolds. By designing the spatial arrangement of these molecular dyes, quantum interference driven by sunlight can be used to alter the direction of energy transfer in these dye assemblies. In the second class, molecular photo switches will be designed that exploit quantum interference in molecular photoisomerization to build molecular pistons that transform light to mechanical energy with power outputs that exceed classical limits.

(3) Whenever a photosynthetic organism absorbs sunlight, it must decide if the absorbed energy is transported to a reaction center, where it drives photoinduced reactions that store biochemical energy, or if it is dissipated as heat into the environment. The ability to balance these outcomes under varying light intensity is essential to the survival of the organism. If too much energy is dissipated into the environment, the organism will not generate the biochemical energy required to survive. If too much energy is directed to the reaction center, photoinduced side-reactions generate toxic byproducts that destroy the cell’s protein machinery. As a result, photosynthetic organisms have evolved a remarkable variety of mechanisms for regulating energy transport, known collectively as nonphotochemical quenching, which allow a limited cast of pigments and proteins to optimally respond to variations in light intensity spanning many time scales and orders of magnitude. Understanding how these systems control energy transport can provide fundamental insights into the mechanisms of biological control and enable the application of these concepts to design robust artificial optoelectronics and sensors. Unfortunately, several important questions remain unanswered. What conformational and chemical changes happen in light harvesting proteins that direct energy to a desired target? (2) What controls these mechanisms and how does this control system generate reliable responses despite microscopic fluctuations? My research will apply computational and theoretical tools from non-equilibrium statistical mechanics, molecular dynamics, and quantum dynamics in order to provide new microscopic insight into these systems.

Teaching Interests

The interdisciplinary nature of my research leaves me well equipped to teach a broad range of graduate and undergraduate courses including:

• Thermodynamics
• Statistical Mechanics
• Quantum Mechanics
• Mathematical Methods in Chemistry and Engineering
• Molecular Simulations

In particular, I have developed syllabi and teaching materials for two courses. First, I developed a modern introductory undergraduate course on quantum mechanics while completing MIT’s Kaufman Teaching Certificate Program. Second, I have developed an intensive graduate course teaching statistical mechanics through molecular simulations during my postdoctoral research. I have had the opportunity to teach and refine the materials for this course while mentoring undergraduate students, graduate students and junior postdoctoral researchers.

I have demonstrated a strong track record of teaching and mentorship excellence throughout my academic career. My formal classroom teaching has been recognized with an MIT Department of Chemistry Graduate Teaching Excellence Award while my mentorship as a Postdoc has earned me a Lawrence Berkeley National Lab Spot Award for Mentorship.