Berlin 2008 – scientific programme
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O: Fachverband Oberflächenphysik
O 55: Poster Session III - MA 141/144 (Methods: Atomic and Electronic Structure; Particles and Clusters; Heterogeneous Catalysis; Semiconductor Substrates: Epitaxy and Growth+Adsorption+Clean Surfaces+Solid-Liquid Interfaces; Oxides and Insulators: Solid-Liquid Interfaces+Epitaxy and Growth; Phase Transitions; Metal Substrates: Adsorption of Inorganic Molecules+Epitaxy and Growth; Surface Chemical Reactions; Bimetallic Nanosystems: Tuning Physical and Chemical Properties; Oxides and insulators: Adsorption; Organic, polymeric, biomolecular films; etc.)
O 55.34: Poster
Wednesday, February 27, 2008, 18:30–19:30, Poster F
High energy x-ray reflectivity study of the room temperature ionic liquids [bmim]+ [PF6]− and [bmim]+ [BF4]− at solid interfaces — •Sebastian Schramm1, Markus Mezger1, Heiko Schröder1, Harald Reichert1, John Okasinski1, Moshe Deutsch2, Benjamin Ocko3, Emerson De Souza1, and Helmut Dosch1 — 1Max-Planck-Institut für Metallforschung, Stuttgart — 2Bar-Ilan University, Ramat-Gan, Israel — 3Brookhaven National Laboratory, Upton, NY, USA
Room temperature ionic liquids (RTILs), being composed solely of ions, are very promising new materials. Their physical properties make them suitable for many technological processes, e.g. as solvents in catalytic reactions and electrolysis. In particular for the understanding of reactions at an interface, knowledge on the spatial arrangement of the ions at hard walls is essential. In our study, we used high energy (∼ 70 keV) x-ray reflectivity to probe the structure of these liquids at the sapphire interface. The results give evidence for interfacial layering in 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]+ [PF6]−), in contrast to 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]+ [BF4]−) where no layering was found. In combination with the analysis of the bulk liquid structure factor, the recorded reflection patterns give both the molecular layer spacing, as well as the decay length of the spatial ordering. We compare the x-ray scattering results with optically obtained surface and interfacial tension data to gain detailed information about the nature of the chemical interaction between the sapphire substrate and the ions of the RTIL.