TY - JOUR A1 - Reiche, Jürgen A1 - Penacorada, Florencio A1 - Geue, Thomas A1 - Pietsch, Ullrich A1 - Brehmer, Ludwig T1 - Monolayers and multilayers of uranyl arachidate : in-plane structure of uranyl arachidate multilayers N2 - The molecular in-plane structure of uranyl arachidate Langmuir-Blodgett (LB) films formed at different subphase pH values was analysed by means of X-ray grazing-incidence diffraction. For multilayers formed at low subphase pH a reorganisation of the arachidic acid film structure is confirmed. At appropriate subphase pH values, reorganisation of the film structure, e.g. via the formation of three-dimensional crystallites, is prevented by the presence of the uranyl ions and by the subsequent introduction of conformational disorder (gauche defects) in the alkyl chains. The observation of a macroscopic flow-induced in-plane texture in these uranyl arachidate LB films has profound implications for the design of ordered, supramolecular structures by the Langmuir-Blodgett technique. Y1 - 1997 ER - TY - JOUR A1 - Henneberg, Oliver A1 - Pietsch, Ullrich A1 - Panzner, Tobias A1 - Geue, Thomas A1 - Finkelstein, Kenneth D. T1 - Simultaneous X-ray and visible light diffraction for the investigation of surface relief and density grating formation in azobenzene containing polymer films N2 - The development of surface relief and density patterns in azobenzene polymer films was studied by diffraction at two different wavelengths. We used x-ray diffraction of synchrotron radiation at 0.124 nm in combination with visible light diffraction at a wavelength of 633 nm. In contrast to visible light scattering x-ray diffraction allows the separation of a surface relief and a density grating contribution due to the different functional dependence of the scattering power. Additionally, the x-ray probe is most sensitive for the onset of the surface grating formation Y1 - 2006 UR - http://www.informaworld.com/smpp/title~content=t713644168~db=all U6 - https://doi.org/10.1080/15421400500383345 SN - 1542-1406 ER - TY - JOUR A1 - Kopec, Maciej A1 - Rozpedzik, Anna A1 - Lapok, Lukasz A1 - Geue, Thomas A1 - Laschewsky, Andre A1 - Zapotoczny, Szczepan T1 - Stratified Micellar Multilayers-Toward Nanostructured Photoreactors JF - Chemistry of materials : a publication of the American Chemical Society N2 - Polyelectrolyte multilayers (PEMs) with stratification of the internal structure were assembled from statistical amphiphilic copolyelectrolytes of opposite charges. These polyelectrolytes organize in aqueous solutions into micellar structures with fluoroalkyl and aromatic nanodomains, respectively, that were also preserved after deposition as thin films via layer-by-layer (LbL) electrostatic self-assembly. The unimolecular micelles, formed due to statistical compositions of amphiphilic polyelectrolytes used, were shown to suppress chain interdiffusion between adjacent layers in resulting micellar PEMs, as evidenced by spectroscopic ellipsometry, atomic force microscopy (AFM), and neutron reflectometry (NR) measurements. Additionally, hydrophobic cores of the micelles were used as hosts for photoactive molecules, namely, ferrocene and perfluorinated magnesium phthalocyanine. Stratified micellar multilayers were then deposited as hollow capsules using CaCO3 microparticles as templates. Photoinduced electron transfer (PET) between ferrocene and phthalocyanine solubilized in the polymer micelles was demonstrated to occur efficiently inside the stratified, polyelectrolyte walls of the capsules, due to the polarity gradient created by the incompatible aromatic and fluoroalkyl domains. The obtained results present a new approach to construct well-organized, self-assembled nanostructured materials for solar energy conversion. Y1 - 2016 U6 - https://doi.org/10.1021/acs.chemmater.6b00161 SN - 0897-4756 SN - 1520-5002 VL - 28 SP - 2219 EP - 2228 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Poloucek, P. A1 - Pietsch, Ullrich A1 - Geue, Thomas A1 - Symietz, Christian A1 - Brezesinski, Gerald T1 - X-ray reflectivity analysis of thin complex Langmuir-Blodgett films Y1 - 2001 ER - TY - JOUR A1 - Pietsch, Ullrich A1 - Grenzer, Jörg A1 - Geue, Thomas A1 - Neißendorfer, Frank A1 - Brezesinski, Gerald A1 - Symietz, Christian A1 - Möhwald, Helmuth A1 - Gudat, Wolfgang T1 - The energy dispersive reflectometer at BESSY II : a challenge for thin film analysis Y1 - 2001 SN - 0167- 5087 ER - TY - JOUR A1 - Grenzer, Jörg A1 - Darowski, Nora A1 - Geue, Thomas A1 - Pietsch, Ullrich A1 - Daniel, A. A1 - Rennon, Siegfried A1 - Reithmaier, Johann-Peter A1 - Forchel, Alfred T1 - Strain analysis and quantum well intermixing of a laterally modulated multiquantum well system produced by focused ion beam implantation Y1 - 2001 ER - TY - JOUR A1 - Mukhopadhyay, M. K. A1 - Datta, A. A1 - Sanyal, M. K. A1 - Geue, Thomas A1 - Pietsch, Ullrich T1 - Synchrotron Studies of Melting of Langmuir-Blodgett Films Y1 - 2001 ER - TY - JOUR A1 - Neumann, Werner A1 - Buchsteiner, Alexandra A1 - Mahler, Willy A1 - Geue, Thomas A1 - Pietsch, Ullrich T1 - Dielectric loss spectroscopy at fatty acid salt multilayers N2 - Dielectric loss spectroscopy (DLS) was performed at compact samples and lamellary organized Langmuir-Blodgett (LB) films from various fatty acid salts. Previous thermoanalytical measurements at compact samples revealed the appearance of two different phase transition temperatures; the lower one is related to the acid the second one to the acid salt molecules. In spite of ill defined electrical contacts with the film the characteristic DLS frequencies obtained from about 100nm thick multilayer films are similar to those recorded from bulk samples. No significant variations of frequencies were found changing the counter ions. Besides conductivity influence at low frequncies we found two relaxations related to the mobility of the dipolar carboxylat-metal group at about 100 and 10000Hz. One of these frequencies is related to the rotation around the chain axis. The strength of this relaxation increases significantly with increasing the sample temperature above 105°C. This temperature is connected with a structural phase transition observed by X-ray reflectometry. In case of Pb-stearate the results of the dielectric measurements help to interprete this structural change as a transition from an orthorhombic into a free-rotator phase. The uncorrelated rotation of molecules around their molecular axes initiates a much increased relaxation strength at the carboxylat-metal sites. Y1 - 2000 ER - TY - JOUR A1 - Stahn, Jochen A1 - Geue, Thomas A1 - Grenzer, Jörg A1 - Pietsch, Ullrich T1 - Interaction of short-chain alkanes with surface and interfaces of multilayer films built from amphiphilic molecules: an in-situ X-ray and neutron scattering probe Y1 - 2000 ER - TY - JOUR A1 - Karcenko, Anatolij V. A1 - Englisch, Uwe A1 - Grenzer, Jörg A1 - Geue, Thomas A1 - Pietsch, Ullrich A1 - Siebrecht, R. T1 - Investigation of partially deuterated multilayers by means of X-ray and polarized neutron reflectometry Y1 - 2000 SN - 1044-8632 ER -