Structure and Depletion at Fluoro- and Hydro-carbon/Water Liquid/Liquid Interfaces

TL;DR

This study uses x-ray reflectivity to investigate oil/water interfaces, finding no evidence of a vapor-like depletion layer, thus supporting the idea that water is in close contact with hydrophobic liquids.

Contribution

It provides experimental evidence against the existence of a vapor-like depletion region at hydrophobic/aqueous interfaces, challenging recent theoretical predictions.

Findings

No vapor-like depletion layer detected at oil/water interfaces

Water is in close proximity to hydrophobic liquids within sub-angstrom distances

Results support direct contact between water and hydrophobic materials

Abstract

The results of x-ray reflectivity studies of two oil/water (liquid/liquid) interfaces are inconsistent with recent predictions of the presence of a vapor-like depletion region at hydrophobic/aqueous interfaces. One of the oils, perfluorohexane, is a fluorocarbon whose super-hydrophobic interface with water provides a stringent test for the presence of a depletion layer. The other oil, heptane, is a hydrocarbon and, therefore, is more relevant to the study of biomolecular hydrophobicity. These results are consistent with the sub-angstrom proximity of water to soft hydrophobic materials.