Molecular semiconducting materials are comprised of many individual
molecules whose individual electronic properties combine to yeild
material-wide semiconducting properties. Unlike traditional
crystalline semiconductors, the electronic structure of
these materials is often spatially and temporally heterogeneous due to the relatively weak
van der Waals forces that drive molecular association. Predicting
how this heterogeneity affects the electronic properties of these
materials is a significant theoretical challenge because the characteristic
length scales involved are beyond the capabilities of most quantum
Our research combines methods of statistical mechanics and quantum dynamics in order to explore how nanoscale disorder affects the emergent electronic properties in molecular semiconducting materials. This relationship is mediated by the static and dynamic properties of excitons, Coulombically bound excited electron-hole pairs. These energetic quasiparticles mediate molecular-scale energy transport in a wide range of systems ranging from modern organic light-emitting diodes (OLEDs) to the light-harvesting machinery in photosynthetic systems. Our approach is focused on developing models that describe the subtle dependence of electronic structure on molecular configuration while simultaneously accounting for the nanoscale correlations that arise through collective molecular fluctuations.
This research project is aimed at enabling the rational design of a
new class of metal-coordinated polymer materials. These materials
utilize the strong but reversible bonds of coordination chemistry as
a cross-linking motif. Because these coordination bonds are tunable
through molecular design these materials can be engineered to
exhibit novel structural and chemical properties. Recent advances in
synthetic techniques, pioneered by our collaborators in the lab of
Jeremiah Johnson (MIT Chemistry), have enabled precise control over
the molecular precursors that comprise these materials. However,
predicting the emergent properties of these materials based on the
molecular details of their precursors continues to be a significant
Our approach utilizes a hierarchy of simulation techniques ranging from all-atom molecular dynamics to abstract models for simulating the dynamic topology of polymer networks. We focus on exploring how heterogeneity in microscopic network structure affects macroscopic material properties such as the viscoelasticity and how these properties can be controlled through systematic variations in molecular structure.
Water plays a fundamental role in processes that cut across all
branches of science. Irrespective of its prevalence, water is
particularly interesting because of its unique microscopic
structure, which consists of a disordered array of molecules engaged
in a three-dimensional hydrogen bonding network. Resolving this picture and how it relates to macroscopic properties
has been a problem of long-standing scientific interest. At the
interface between liquid water and a disordered substrate (such as
the surface of a protein) the microscopic details of interfacial
structure reflect a competition between water-water and
water-substrate interactions. Variations in the balance between these interactions, along with their
effect on the termination of water's three-dimensional hydrogen
bonding network account for the large array of observed hydrophilic
interfacial structures. This forms the basis for a rich and challenging problem in statistical mechanics.
Our research is aimed at providing a statistical mechanical framework for analyzing the molecular structure and dynamics of liquid water interfaces. Specifically, we apply tools from information theory to the analysis of atomistic simulation data as a novel and minimally subjective methodology for quantifying the molecular details of interfacial structure. We apply these tools to investigate protein hydration to explore how heterogeneous surface chemistry and conformational dynamics affect the microscopic properties of the protein's hydration shell.
The process of electrochemical water splitting is of general
scientific interest due to its potentially major role in future renewable energy solutions. It is among a large number of aqueous electrode processes that intimately involve the dynamics of protons and/or
hydroxide ions, the products of water auto-ionization. The aqueous dynamics
of these ions (and many other reactive species) in the vicinity of the
water-electrode interface and their dependence on applied voltage
represent an important yet poorly understood aspect of aqueous electrochemistry.
We are interested in using molecular simulation in order to elucidate the dynamics of hydroxide and hydronium ions at the aqueous electrode interface. We study the interplay between the dynamics of electrode-adsorbed molecules and solvent fluctuations, along with the concomitant influence on electrochemical dynamics near the electrode.