Berlin 2008 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 32: Oxides and Insulators: Clean Surfaces

O 32.11: Vortrag

Dienstag, 26. Februar 2008, 15:30–15:45, MA 042

Structural arrangement of room temperature ionic liquids at a hard wall — •Heiko Schröder, Markus Mezger, Sebastian Schramm, Harald Reichert, John Okasinski, and Helmut Dosch — Max-Planck-Institut für Metallforschung, Stuttgart

Interfacial phenomena in physical, chemical, and biological systems are of increasing relevance in many of today’s technological applications. In order to access solid-liquid interfaces and extract microscopic details of their local structure with high resolution, we have employed high energy x-ray microbeam reflectivity. Here, we discuss the analysis and interpretation of reflectivity data recorded at the interface between different room temperature ionic liquids (RTIL) and a hard wall (sapphire). Real space structures could be resolved with Å-resolution. Although crucial for the understanding of solvent properties, only little is known about the structural arrangement of anions and cations in RTILs at solid interfaces. We systematically examined different parameters altering the interfacial properties. By choosing different combinations of anions and cations, the ion-ion and ion-substrate interaction as well as the size ratio of the involved ions could be varied. By modifying the temperature, the ratio between entropy and interfacial energy can be tuned as well, favoring a disordered liquid or interfacial layering, respectively. This results in different structural arrangements at the molecular level.