A recent research investigation conducted by teams from Columbia University and UC Berkeley reveals how water behaves during interface interactions between oil and water molecules. The publication, featured in Nature and referenced below, returns to long held assumptions about hydrophobic surface inactivity and reveals potential applications for energy and biomedicine as well as catalysis.
Shi, L., LaCour, R.A., Qian, N. et al. Water structure and electric fields at the interface of oil droplets. Nature (2025). https://doi.org/10.1038/s41586-025-08702-y
Sum frequency generation (SFG) spectroscopy has been the tool of choice for probing water at interfaces for many a year. However, the gaps in Sum frequency generation (SFG) spectroscopy motivated scientists to create new examination approaches. The research applied high-resolution Raman spectroscopy with multivariate curve resolution (MCR) algorithms. The team achieved better clarity of signals related to solutes by using this approach which enabled nanoresolution of interfacial layers in oil–water emulsions.
its limitations have encouraged researchers to explore alternatives. In this study, a combination of high-resolution Raman spectroscopy and multivariate curve resolution (MCR) algorithms was employed. This approach allowed the team to isolate solute-correlated signals from the solvent background with greater clarity, resulting in nanoscale resolution of interfacial layers in oil–water emulsions.
The measurements indicated a significant disruption in the hydrogen-bonding network. In particular, the characteristic OH-stretch feature, usually observed around 3250 cm⁻¹ in bulk water, diminishes at the interface. Molecular dynamics simulations suggest that approximately 25% of the interfacial water molecules exhibit “free” OH groups, a finding that goes against the traditional view of a highly ordered, ice-like structure.
Another key result is the observation of ultrahigh electrostatic fields at the oil–water interface, with measurements ranging between 40 and 90 MV/cm. By analysing redshifts in the resonance peaks, around 3575 cm⁻¹, associated with free OH bonds, the researchers linked these intense fields to variations in the droplet ζ-potential. Adjustments in the ζ-potential—from −60 mV to −20 mV—were found to reduce the redshift, meaning charge distribution changes such as hydroxide adsorption or oil–water charge transfer.
Transition state theory calculations in the study indicate that these fields could reduce the activation free energy by nearly 5 kcal/mol. This reduction is enough to potentially enhance reaction rates by over 3,000 times at room temperature.
The research could affect how scientists approach challenges in water purification, oil-spill remediation, and the development of triboelectric nanogenerators, among other areas.
The research was done by a collaborative team led by Prof. Wei Min of Columbia University and Prof. Teresa Head-Gordon of UC Berkeley. Co-first authors are Dr. Lixue Shi and Dr. Allen LaCour, with critical contributions from Naixin Qian, Joseph Heindel, Xiaoqi Lang, and Ruoqi Zhao. Their work demonstrates how integrating advanced spectroscopic techniques with modern data analysis can yield insights that refine our understanding of long-studied phenomena.
Hassan graduated with a Master’s degree in Chemical Engineering from the University of Chester (UK). He currently works as a design engineering consultant for one of the largest engineering firms in the world along with being an associate member of the Institute of Chemical Engineers (IChemE).
