Unraveling Molecular Structure in Stern Layer at Charged Water Interface using sum-frequency vibrational spectroscopy
Yu-Chieh Wen1,2,3*, Shuai Zha3, Shanshan Yang3, Chuanshan Tian3, Y. Ron Shen2
1Institute of Physics, Academia Sinica, Taiwan, Taiwan
2Department of Physics, University of California, Berkeley, California, United States of America
3Department of Physics, Fudan University, Shanghai, China
* presenting author:Yu-Chieh Wen, email:yuchiehwen@gmail.com
Charged aqueous interfaces, such as membrane/water and electrochemical interfaces, are essential in many chemical, biological, and environmental processes. Interactions between heterogeneous interfacial molecules and the consequent molecular network dictate properties and functions of the interfaces; however, the microscopic-level picture of the charged water interfaces remains substantially unclear. Here we demonstrate probing of the molecular structure in Stern layer at aqueous interfaces using sum-frequency vibrational spectroscopy. We show that at ionic surfactant/water interfaces, the hydrogen- (H-)bonding strength and network in the Stern layer depend sensitively on conformation and ionization of the surfactants, suggesting a relevant influence of the surfactant-water charge transfer. In addition, ion adsorption to the interface is shown to distort the interfacial water structure. Our study offers exciting opportunities to acquire microscopic insights into interfaces for catalytic and electrochemical applications.

Keywords: Chemical Physics, Surface Science, Laser Spectroscopy, Nonlinear Optics