Collaborative Research: Soft Interfaces and Charge Separation Stabilization

With funding from the Chemical Structure Dynamics and Mechanisms-A (CSDM-A) Program of the Chemistry Division, Heather C. Allen at Ohio State University and David T. Limmer at University of California-Berkeley are using state-of-the-art experimental and computational tools to understand chemistry at soft interfaces.

Soft interfaces are those involving two phases, like liquid water and its vapor, with a transition zone of molecular width. Properties of these interfaces can be difficult to predict, especially how they affect the outcomes of chemical reactions. The PIs will overcome these technical challenges by examining related gas phase molecules that have distinctly different electronic structures at the surface of different solvents.

This systematic approach is expected to provide insight into how chemical reactions occur at soft surfaces generally, with potential implications to atmospheric and industrial chemistry. This project is supporting the training of a graduate student and a post-doctoral associate at Ohio State, and a graduate student at UC-Berkeley. In addition to formal research training and education, the project will support the development of videos on molecular dynamics (MD) simulation of interfacial dynamics that can be used in General Chemistry courses to reinforce equilibrium and interfacial chemistry concepts.

The project focuses on tuning the dielectric constant and viscosity of solutions and will utilize gas phase molecules, N2O5 and N2O4, as interfacial probes of their resultant charge stabilization. These molecules possess significantly different reactivities at interfaces, as N2O5 elicits a significant level of charge separation whereas N2O4 does not.

Solvents with different polarities, chain lengths and structures will be studied to modulate these intrinsic differences. Experimental observations will be interpreted with the help of molecular dynamics simulations employing artificial neural network potentials. The broader impacts of this research include societal benefits from an increased understanding interfacial reactivity, with particular attention to the interfacial accommodation of atmospheric aerosols.

In addition, this highly collaborative and combined theoretical and experimental inquiry will provide good opportunities for the training of graduate students and postdoctoral research associates.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.