In this CAREER award, supported by the Chemical Structure, Dynamics and Mechanisms Program of the Chemistry Division, Professor John McGuire and his research group at Michigan State University will study vibrational relaxation, orientational dynamics, and couplings between vibrational modes of water at aqueous interfaces. The properties of water, such as its anomalously high boiling point and heat capacity, derive largely from its hydrogen-bond network. The properties of this network are often a product of its dynamics, which are characterized by picoseconds to sub-picosecond timescales. The termination of the hydrogen-bond network at interfaces leads to dynamics distinct from those widely measured in the bulk. However, to date, the vast majority of experimental studies of aqueous interfaces have focused on their static properties. By exciting a non-equilibrium distribution of water molecules and then measuring the surface-sensitive sum-frequency response, the surface dynamics can be probed. This offers the opportunity for new insights into the interfacial hydrogen-bond network. Professor McGuire's group will employ new multidimensional and phase-sensitive techniques for the detection of sum-frequency signals to enhance the sensitivity to weak surface nonlinear optical processes. Investigations will address the differences in the dynamical properties of a range of chemically and physically important aqueous interfaces including hydrophobic and hydrophilic interfaces and aqueous interfaces characterized by varying concentrations of solutes such as salts.
Understanding dynamics and vibrational couplings at aqueous interfaces will impact our understanding of a broad range of phenomena at aqueous interfaces, such as solvation and charge transfer, that are central to such varied processes as protein folding, electrochemical energy generation and storage, heterogeneous catalysis, and atmospheric chemistry. The techniques developed will also find application in studies of other interfacial and non-centrosymmetric bulk systems. Students involved in this project will receive training in vibrational and ultrafast spectroscopy and nonlinear optical techniques broadly applicable to studies of chemical and physical systems. Through activities such as engagement of high school teachers in research and hands-on workshops for K-12 teachers, the process and results of scientific discovery and an appreciation for a scientific understanding of water will be disseminated to students in K-12.
