Dresden 2014 – scientific programme
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O: Fachverband Oberflächenphysik
O 36: Posters: Bio/organic Molecules on Surfaces, Graphene, Solid/liquid interfaces, Metal Substrates, Electronic Structure Theory
O 36.66: Poster
Tuesday, April 1, 2014, 18:30–22:00, P1
Experimental and theoretical studies of water orientation at the CaF2 interface at different pH. — •Maria Jose Perez-Haro1, Remi Khatib2, Mischa Bonn1, Marialore Sulpizi2, and Ellen H.G. Backus1 — 1Max Planck Inst Polymer Res, D-55128 Mainz, Germany — 2Johannes Gutenberg Univ Mainz, Dept Phys, D-55099 Mainz, Germany
The molecular arrangement of water molecules at solid-aqueous interfaces is important in numerous areas of science. It is very challenging to obtain molecular insights into this type of interfaces. We present here a combined experimental and theoretical approach to obtain those molecular insights into water at the interface between CaF2 and aqueous solutions at different pH.
The experimental results have been obtained with the surface-sensitive spectroscopy technique Vibrational Sum Frequency Generation (SFG), and the recently developed expansion of this technique: phase-sensitive SFG. The vibrational spectrum of the interfacial water molecules thus obtained with SFG reflects the organization and arrangement of interfacial water. We have unraveled the structure, including the absolute orientation of the water molecules at the interface. We clearly see an orientation inversion, 'flip-flop', of the water molecules as the pH of the aqueous phase is changed from acidic to alkaline. The experimental spectra are compared to calculated spectra obtained from first principles molecular dynamics simulations. This comparison provides new insight in the molecular species present at the interface.