Seeing the Invisible Order in Biological Materials using a Nonlinear Vibrational Spectroscopy Technique

E SC/E MCH 514 graduate Seminar

Sum Frequency Generation (SFG) vibrational spectroscopy is widely recognized as a premier surface-sensitive characterization tool providing molecular information of chemical species at interfaces of two bulk media (such as molecular species at gas/solid, vapor/liquid, and even liquid/liquid interfaces). While this interfacial sensitivity represents one important application, it reflects only one consequence of the deeper physical principle underlying SFG: the requirement of noncentrosymmetry for nonlinear optical process. Any noncentrosymmetric structure—whether located at a surface, within a crystalline domain, or dispersed throughout a macroscopically centrosymmetric or disordered environment—can generate a coherent SFG response. Based on this principle, SFG becomes a powerful spectroscopic method capable of selectively probing crystalline biopolymers embedded in complex biological materials. Polysaccharides such as cellulose, chitin, and starch, and fibrous proteins such as collagen and silk, all possess intrinsic molecular and supramolecular noncentrosymmetry across multiple length scales. In this talk, I will present how leveraging SFG’s fundamental symmetry-based selectivity enables multiscale structural analysis of hierarchical biopolymer assemblies in natural materials, and how these insights open new pathways for understanding and engineering bio-inspired materials.

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Dr. Seong H. Kim is the Department Head and Walter L. Robb Family Endowed Chair in the Robert V. Waltemyer Department of Chemical Engineering at The Pennsylvania State University. A globally recognized expert in surface science and tribology, Dr. Kim’s research spans a wide range of materials including silicate glasses, natural biopolymers, and advanced carbon coatings. His work has significantly advanced the understanding of surface chemistry, mechanochemistry, and the durability of materials under environmental and mechanical stresses. His recent research focuses on characterizing invisible subsurface damage in glass, tribochemical reactions at sliding interfaces, and the structural analysis of natural materials using advanced spectroscopic techniques. Dr. Kim’s interdisciplinary approach continues to influence both fundamental science and industrial applications, particularly in the fields of nuclear waste management, display glass technology, and sustainable materials. Dr. Kim earned his Ph.D. in Chemistry from Northwestern University and completed postdoctoral research at the University of California, Berkeley. Since joining Penn State in 2001, he has held numerous leadership roles and was named a Distinguished Professor in 2021. He has authored over 400 peer-reviewed publications (with h-index of 78), wrote textbook Surface and Interface Analysis: Principles and Applications, and is a Fellow of the Society of Tribologists and Lubrication Engineers.