Date/Time
Date(s) - 11/07/2024
11:30 am - 12:30 pm

Title: Structure of Molecules at Air/Aqueous Interface: An Insight into the Impact of Hofmeister Ions Using Nonlinear Vibrational Spectroscopy

Date: Thursday July 11, 2024

Time: 11:30am

Room: ABB 165

Host: Dr. Peter Kruse

Abstract:
Interfaces are ubiquitous in nature and defined as the boundaries separating two different media. Due to the breakdown of the centrosymmetric environment, the behavior of molecules at the interface are expected to be unique and different from those in the bulk. In my talk, I will focus on water and aqueous interfaces relevant to various research fields ranging from chemistry, physics, and engineering to industrial applications. Understanding interfacial structure, particularly the hydrogen bonding network and the complicated vibrational coupling of interfacial water molecules, is not straightforward to infer. In order to investigate the interfacial properties, it is necessary to implement superior spectroscopic tools to extract new insights into the existing understating of various interfacial mechanisms. We have implemented sum frequency generation (SFG) vibrational spectroscopy for our studies. SFG is a surface-specific and molecularly sensitive laser spectroscopic tool based on the second-order nonlinear optical process. Here, we use two pump beams (Vis and tunable IR) and allow them to satisfy the spatial and temporal coherence at the interfacial region to generate the SFG signal. The SFG signal carries the vibrational signature of the molecules residing at the interfacial region. In my talk, I will give detailed insight into the role of the hydrogen bonding environment of the interfacial water molecules in the evaporation process¹. I would also highlight the spectroscopic signature of ion-specific water-macromolecule interactions in a complicated ternary molecular system². In both the molecular systems, the detailed insight into the Hofmeister effect will be explained using kosmotropic (structure-makers) and chaotropic (structure-breakers) ions.

References:
1. Bhawna Rana, David J. Fairhurst, and Kailash C. Jena, “Investigation of Water Evaporation Process at Air/Water Interface using Hofmeister Ions”, J. Am. Chem. Soc., 144 (2022) 17832.
2. Bhawna Rana, David J. Fairhurst, and Kailash C. Jena, “Ion-Specific Water Macromolecule Interactions at Air/Aqueous Interface: An Insight into Hofmeister Effect”, J. Am. Chem. Soc., 145 (2023) 033703.

Biography:
Dr. Kailash Jena, is currently working as an Associate Professor in the Department of Physics, Indian Institute of Technology, Ropar, Punjab. His research focus is in the field of nonlinear sum-frequency generation (SFG) vibrational spectroscopy of surfaces and interfaces and its application to probe the molecular structure of various biomolecules, polymers, nanomaterials, and ions and their interactions with interfacial water molecules at air/water interfaces. He received his Ph.D. degree in 2008 from the Indian Institute of Technology, Madras, under the mentorship of Prof. Prem B. Bisht and Prof. S. Kasiviswanathan. During his Ph.D., he studied the nonlinear optical properties and relaxation processes of organic molecules using laser-induced transient grating technique. After finishing his doctorate degree from IIT Madras, he joined Prof. Dennis Hore’s research group in 2007 as a postdoctoral researcher at the University of Victoria, Canada. He studied interfacial water structure at solid / water interface in the presence of ions using sum frequency generation vibrational spectroscopy. In 2011, he joined Prof. Sylvie Roke’s research group at the prestigious Max-Planck Institute for Intelligent Systems, Stuttgart, Germany, and moved to École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland. There, he worked on sum Frequency Generation Scattering spectroscopy to probe the formation and characterization of model membrane systems at the water / nanoscopic oil droplet interfaces.