Berlin 2015 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 60: Dielectric and Molecular/Water Interfaces
O 60.7: Vortrag
Mittwoch, 18. März 2015, 16:30–16:45, MA 043
Solid/water interfaces from theory and experiments: the fluorite/water interface — •Rémi Khatib1, Ellen H. G. Backus2, Marie-Pierre Gaigeot3, and Marialore Sulpizi1 — 1Johannes Gutenberg Universität, 55128 Mainz, Germany — 2Max Planck Institute for Polymer Research, 55128 Mainz, Germany — 3Université d’Evry val d’Essonne, 91025 Evry, France
Vibration Sum Frequency Generation (VSFG) spectroscopy is a powerful technique which is able to provide information about surfaces and interfaces selectively excluding the centrosymmetric contribution from bulk. The experimental spectra contain information which is crucial to characterize e.g. solid/liquid interfaces (including hydrogen bond strength, water dipole orientation) but they call for a microscopic/molecular level interpretation.
Here we present a collaborative theoretical/experimental study which provides a new microscopic understanding of the fluorite (CaF2)/water interface as function of pH. Our interest is twofold: 1) from the theoretical point of view we develop and test new tools to calculate the VSFG spectra including an ab initio description of the models; 2) from the experimental point of view, we move beyond the current state of the art providing the first Phase-Sensitive VSFG spectra for CaF2/water interfaces.
The results are encouraging. We provide an atomistic description of the interfaces CaF2/water according to a wide range of pH. We can understand the impact of the surface termination on the water orientation and we can show in particular the importance of the electrical field due to ions in solution on the VSFG response.