Water is more than a passive solvent: at interfaces and within crowded biological environments, its molecular structure, electrostatics, and reactivity can differ profoundly from those of bulk water. Our group develops advanced vibrational spectroscopic and imaging approaches to uncover these properties, and combines experiment with electron-transfer theory to understand how they enable unexpected chemistry. From aqueous microdroplets and intracellular water to biomolecular assemblies and microplastic surfaces, we seek to establish general principles linking water’s local environment to chemical and biological function.
Figure 1 | Spectroscopy of interfacial water. Vibrational Stark probes and Raman-based methods map molecular environments and quantify local electric fields at aqueous microdroplet, oil–water, and biomolecular interfaces.
Water at interfaces exhibits molecular structures and electrostatic environments distinct from those of bulk water, yet directly characterizing these properties remains a major experimental challenge. We develop interface-selective vibrational spectroscopic methods to uncover the molecular origins of these differences. Using vibrational Stark probes, we revealed exceptionally strong electric fields, on the order of 10⁷ V/cm, at aqueous microdroplet interfaces. More recently, Raman spectroscopy combined with multivariate curve resolution (Raman-MCR) enabled us to resolve the hydrogen-bonding structure of water at oil–water interfaces, revealing disrupted hydrogen-bond networks, red-shifted dangling OH groups, and local electric fields reaching approximately 50–90 MV/cm. Extending these approaches to biomolecular assemblies, we further identified strong interfacial electrostatic environments associated with amyloid-β aggregation and spontaneous redox activity. Together, these studies establish spectroscopic routes for connecting the molecular structure of interfacial water to its electrostatics and chemical behavior.
Figure 2 | Water inside living cells. Optical imaging and Raman spectra reveal spatially heterogeneous water environments and a small population of intracellular water with non-bulk-like hydrogen-bond structure.
Water constitutes the dominant molecular component of living cells, yet its organization and behavior in the crowded intracellular environment remain poorly understood. We develop advanced vibrational imaging and spectroscopic approaches to visualize and characterize biological water directly in living systems. Using stimulated Raman excited fluorescence microscopy, we mapped distinct water environments within individual living cells, revealing pronounced spatial heterogeneity between the nucleus and cytoplasm. Complementary Raman microspectroscopy identified a small but reproducible population of non-bulk-like intracellular water characterized by weakened hydrogen bonding and reduced tetrahedral ordering. These findings challenge the simplistic view of intracellular water as a uniform solvent and provide new opportunities to investigate how local hydration environments relate to cellular organization and biological function.
Figure 3 | Quantum tunneling on water. Schematic of partially desolvated interfacial hydroxide and the proposed concerted electron-transfer pathway, contrasted with sequential ionization and electron capture.
Water microdroplets exhibit remarkable redox chemistry, including spontaneous oxidation and reduction reactions that are strongly suppressed in bulk solution. What molecular mechanism allows a seemingly ordinary water interface to facilitate such unusual reactions? To address this question, we developed Quantum Tunneling on Water, a theoretical framework extending Marcus electron-transfer theory to heterogeneous aqueous interfaces. The central idea is that interfacial solvation can simultaneously influence the availability of reactive donor configurations, solvent reorganization energetics, and electronic coupling between electron donors and acceptors. In particular, partially desolvated interfacial hydroxide ions can undergo concerted electron transfer to nearby molecular acceptors through quantum tunneling, without requiring the formation of freely solvated electrons. This framework provides a molecular-level basis for understanding and quantitatively modeling spontaneous redox chemistry at water interfaces, connecting interfacial molecular organization to emergent chemical reactivity.
