Ionic profiles close to dielectric discontinuities: Specific ion-surface interactions

Abstract

We study, by incorporating short-range ion-surface interactions, ionic profiles of electrolyte solutions close to a non-charged interface between two dielectric media. In order to account for important correlation effects close to the interface, the ionic profiles are calculated beyond mean-field theory, using the loop expansion of the free energy. We show that how it is possible to overcome the well-known deficiency of the regular loop expansion close to the dielectric jump and treat the non-linear boundary conditions within the framework of field theory. The ionic profiles are obtained analytically to one-loop order in the free energy, and their dependence on different ion-surface interactions is investigated. The Gibbs adsorption isotherm as well as the ionic profiles is used to calculate the surface tension, in agreement with the reverse Hofmeister series. Consequently, from the experimentally measured surface tension, one can extract a single adhesivity parameter, which can be used within our model to quantitatively predict hard to measure ionic profiles.