Water at the Edge: On-Water Spectroscopy across Oil Droplets, Protein Surfaces, and Living Cells

Interfacial water exhibits rich and complex behavior, playing a critical role in chemistry, biology, geology, and engineering. Despite its importance, fundamental properties of water at hydrophobic interfaces - such as orientational ordering, hydronium and hydroxide concentrations, improper hydrogen bonding, and the presence of strong electric fields - remain highly debated. These controversies arise from the inherent challenges in probing interfacial systems, even with state-of-the-art experimental techniques. In this seminar, I will present newly developed on-water optical spectroscopy capable of investigating diverse interfacial systems, including oil-water emulsions, protein hydration shell, and even the interior of living cells. These techniques provide insights into key properties such as interfacial water’s tetrahedral structure, free O-H groups, electrostatics, illuminating the remarkable chemical activity observed at hydrophobic-water interfaces such as in microdroplets and contact electro-catalysis. Additionally, I will discuss the broader implications for materials science, environmental studies, and biomedical research.

Speaker: Wei Min, Columbia University