Ultrafast dynamics of interfacial water with high-resolution 2D-SFG spectroscopy

• Applicant: Professor Dr. Poul Bering Petersen
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 544667190

Aqueous interfaces play a critical role in a wealth of natural and chemical processes ranging from atmospheric and biological processes to chemical processes in technological applications. The chemical nature of the interface dictates the boundary conditions to the bulk hydrogen-bonded network and determines the properties of water in the interfacial region. The properties of interfacial water in turn define the local chemical environment where the chemical species react. Water can furthermore play direct active roles in mediating chemical contacts and proton transfer reactions. In order to understand interfacial processes in molecular details, we need to understand how water behaves in interfacial regions as a function of the surface chemistry. Unfortunately, interfacial water under ambient conditions is notoriously difficult to study, requiring methods that can single out the surface water from the bulk and operates on the time scale of the ultrafast dynamics of hydrogen‐bonded network. The overall goal of this research project is to develop a molecular understanding of not only the structure and but also, in particular, the dynamics of interfacial water as a function of the surface chemistry. Here characterizing the dynamics of the hydrogen-bonded network with high-time and frequency-resolution is key to understand how many micro-environments exists for the water at a given surface, their fluctuations, and the timescale of their interchange. Analogous to the high-resolution bulk 2D IR studies, which revealed the ultrafast dynamics of bulk water and laid the foundation for our current understanding of bulk water, we need to perform high-resolution surface-specific versions of the same experiments in order to understand interfacial water. The proposed experiments will produce the first such high-resolution 2D sum-frequency generation experimental data. We will furthermore perform high-resolution 2D SFG experiments on both the classical air-water interface as well as buried solid-water interfaces with variable surface chemistry. The experimental project will in combination with theoretical simulations, uncover the structure-function relationships between the boundary conditions imposed by the surface chemistry on the hydrogen-bonded dynamics of interfacial water. These will greatly help understand the hydrophobic effect and how water interacts with surfaces in natural and technological systems that impact a wide range of fields and applications involving heterogeneous aqueous chemistry, encompassing biological systems, atmospheric reactions, and fuel cell membranes and electrochemistry.

• DFG Programme: Research Grants