Berlin 2015 – scientific programme

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O: Fachverband Oberflächenphysik

O 40: Solid-Liquid Interfaces

O 40.9: Poster

Tuesday, March 17, 2015, 18:15–21:00, Poster A

The hydrophobic gap under high hydrostatic pressure conditions — Florian Wirkert¹, •Michael Paulus¹, Julia Nase¹, Johannes Möller², Paul Salmen¹, Irena Kiesel³, Benedikt Nowak¹, Christian Sternemann¹, and Metin Tolan¹ — ¹Fakultät Physik/DELTA, TU Dortmund, 44221 Dortmund, Germany — ²ESRF - The European Synchrotron, 71 Avenue des Martyrs, F-38043 Grenoble, France — ³Institut Laue-Langevin, 71 Avenue des Martyrs, 38000 Grenoble, France

We present an x-ray reflectivity (XRR) study on the influence of high hydrostatic pressure (HHP) on the structure of the so-called hydrophobic gap, a small electron depleted region at the interface between a hydrophobic surface and water. The structure of this gap has been discussed controversially throughout the last few years. In order to obtain a deeper insight into the gap's structural composition, we investigated the interface between a hydrophobic silicon wafer and ultrapure water at HHP conditions using XRR measurements. This technique is known to reliably resolve the shape (thickness, roughness, electron density) of thin layered structures on a molecular length scale.

The experiments have been performed at the synchrotron radiation facilities DELTA (Dortmund, Germany), Diamond Light Source (Didcot, UK) and ESRF (Grenoble, France). It is shown that only a small fraction of the hydrophobic gap is compressed under HHP. The main compression occurs between 1 bar and 1 kbar.