Dresden 2017 – wissenschaftliches Programm
CPP 49.5: Poster
Mittwoch, 22. März 2017, 18:30–21:00, P2-OG1
Specific Ion Effects on the Adsorption and Structure of Dodecyl Sulfate Modified Air/Water Interfaces — Eric Weißenborn1, •Christian Sauerbeck2, and Björn Braunschweig1 — 1Institut für Physikalische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstraße 28/30, 48149 Münster, Germany — 2Institute of Particle Technology (LFG), Friedrich-Alexander University of Erlangen-Nürnberg (FAU), Cauerstrasse 4, 91058 Erlangen, Germany
The influence of Li+, Na+ and Cs+ cations on the coverage and structure of dodecyl sulfate (DS) anions at the air/water interface was investigated with a thin film pressure balance (TFPB) and vibrational sum-frequency generation (SFG). Particularly we have addressed the change in amplitude of O-H stretching bands which provides information on the charging state of the interface. That is because the static electric field within the interfacial’s double layer can polar order and polarize interfacial H2O molecules. As a consequence, the amplitude of O-H bands in SFG spectra becomes strongly dependent on the interfacial net charge. In addition, an analysis of the symmetric S-O stretching band at 1070 1/cm as a function of bulk salt and DS concentration provides information on the surface coverage and Gibbs free energies of adsorption when an adsorption isotherm is fitted to the experimental data. Here, we can show that the latter are a function of the bulk salt concentration and are ion specific. The magnitude of this ion specific effect decreases with the size of the alkali cation in the following way Cs+ >Na+ >Li+.