Salt effects on water/hydrophobic liquid interfaces: a molecular dynamics study.

We investigate structural and dynamical properties of NaCl and KCl solution/n-decane interfaces. We find that K(+) and Cl(-) ions localize close to the interface and modify the orientations of both first-layer and second-layer water molecules in the interfacial region. Na(+) and Cl(-) ions are also localized; however, they do not affect the orientation significantly. NaCl salts cause an increase of the surface tension and the residence time of interfacial water molecules. They also decrease the residence time of interfacial n-decane molecules. KCl salt has similar effects, although to a smaller extent. These findings may help us to better understand biological interfaces in physiological solutions.