Solute-free interfacial zones in polar liquids.

Large, solute-free interfacial zones have recently been described in aqueous solutions. Found next to hydrophilic surfaces, these "exclusion zones" are commonly several hundred micrometers wide and represent regions of water that appear to be more ordered than bulk water. We report here that other polar solvents including methanol, ethanol, isopropanol, acetic acid, D(2)O, and dimethyl sulfoxide (DMSO) show similar near-surface exclusion zones, albeit of smaller magnitude. Microelectrode measurements show that these zones are negatively charged and grow in response to incident infrared radiation, similar to exclusion zones in aqueous solutions. Hence, near-surface exclusion zones appear to be features characteristic not only of water but of other polar liquids as well.