Raman spectroscopy of solutions and interfaces containing nitrogen dioxide, water, and 1,4 dioxane: evidence for repulsion of surface water by NO2 gas.

The interaction of water, 1,4 dioxane, and gaseous nitrogen dioxide, has been studied as a function of distance measured through the liquid-vapour interface by Raman spectroscopy with a narrow (<0.1 mm) laser beam directed parallel to the interface. The Raman spectra show that water is present at the surface of a dioxane-water mixture when gaseous NO2 is absent, but is virtually absent from the surface of a dioxane-water mixture when gaseous NO2 is present. This is consistent with recent theoretical calculations that show NO2 to be mildly hydrophobic.