Regensburg 2007 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 44: Poster Session II (Semiconductors; Oxides and Insulators: Adsorption, Clean Surfaces, Epitaxy and Growth; Surface Chemical Reactions and Heterogeneous Catalysis; Surface or Interface Magnetism; Solid-Liquid Interfaces; Organic, Polymeric, Biomolecular Films; Particles and Clusters; Methods: Atomic and Electronic Structure; Time-resolved Spectroscopies)

O 44.13: Poster

Mittwoch, 28. März 2007, 17:00–19:30, Poster C

Subphase dependent (2D) ordering in monolayers of amphiphile molecules — •Saskia Schmacke¹, Bernd Struth², Lutz Wiegart³, Henri Gleyzolle³, and Metin Tolan¹ — ¹Experimentelle Physik E1a, Universität Dortmund, Otto-Hahn-Str. 4, D-44221 Dortmund — ²Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, D-22607 Hamburg — ³ESRF, 6 rue Jules Horowitz, BP 220, F-38043 Grenoble Cedex

Layers of amphiphile molecules on liquid subphases show a different phase behaviour depending on enviromental parameters like temperature, surface pressure and subphase. Gaseous, liquid and solid phases are observable. In this work the influence of different subphases on the crystal structure of the Phospholipid monolayers DPPA (dipalmitoyl-phosphatidic acid) and DPPC (dipalmitoyl-glycerophosphocholine) was investigated. The crystal structure was determined by using Gracing Incidence X-Ray Diffraction technique (GID) at the beamline ID10b, ESRF. The obtained diffraction patterns are analysed in two steps: First the information about the 2D unit cell of the crystalline phase, e.g. lattice spacings, lattice type (2D Bravais lattice) and the deformation of the lattice was determined. Secondly the intensity dependence on wave vector transfers perpendicular to the surface was analysed leading to information about the scatterer itself, like chain length, diameter, tilt angle and orientation within the lattice of the molecules forming the monolayer. The calculation of the differential cross section using a cylinder model for the lipid molecules shows very good agreement with the experiment for all subphases.