New X-ray method isolates faint signals from water at material surfaces

Researchers from Toyohashi University of Technology, the Institute for Molecular Science, and the Institute of Science Tokyo have devised a novel technique to detect weak signals of interfacial water near material surfaces using X-rays. Led by Yu Kinjo and Professor Ryugo Tero, the team integrated X-ray absorption spectroscopy with data analysis to isolate the feeble signals of interfacial water from the dominant bulk water.

This method allowed them to discern differences in water's state between inorganic material surfaces and lipid bilayers, which resemble biological membranes. Interfacial water, crucial for molecular adsorption, chemical reactions, and biological functions, often gets drowned out in conventional measurements. The new approach involves varying the thickness of the water layer and applying multivariate curve resolution–alternating least squares (MCR-ALS) data analysis.

Applied to an oxide layer on silicon nitride and lipid bilayers, the method revealed distinct spectral features for interfacial water near the oxide surface, indicative of surface interactions, while the lipid bilayer showed a smoother profile and a greater relative contribution of interfacial water, reflecting varied hydrogen-bonding environments.

The study, published in Applied Physics Express, opens new avenues for understanding water-material interfaces across various materials, including polymers, and paves the way for designing functional materials in aqueous environments and elucidating biological membrane-water interactions.