The interaction of DNA with other DNA and with charged interfaces is of utmost importance for understanding nonviral transfection and DNA diagnostics with optimized chips. This can be studied in detail using Langmuir monolayers of cationic lipids as soft surface of a DNA containing subphase. The positional order of the lipid and the DNA sublattices can be studied by synchrotron X-ray diffraction under continuous variation of parameters such as molecular density or surface pressure. It is shown that DNA binding condenses the membrane surface, and the resulting structure is determined by the interplay of DNA-lipid and DNA-DNA interactions.

A detailed analysis of a metallosupramolecular coordination polyelectrolyte-amphiphile complex (PAC) at the air/water interface is presented based on Langmuir isotherm measurements, Brewster angle microscopy as well as X-ray reflectance and diffraction measurements. The PAC is prepared in solution by metal-ion coordination of Fe(OAc)2 and 1,4-bis(2,2':6',2"-terpyridin-4'-yl)benzene followed by self-assembly with dihexadecyl phosphate (DHP). The spreading of the PAC at the air/water interface results in a Langmuir film with a stratified architecture, such that DHP forms a monolayer on the water surface, while the metallosupramolecular coordination polyelectrolyte (MEPE) is immersed in the aqueous subphase. Electrostatic interactions of MEPE and DHP force the alkyl chains into an upright, hexagonal lattice even at low surface pressures. This work illustrates how supramolecular, colloidal, and surface chemistry can be combined to create complex architectures with tailored characteristics that may not be accessible through self-organization in the liquid phase.

A detailed analysis of a metallosupramolecular polyelectrolyte-amphiphile complex (PAC) at the air-water interface is presented. Langmuir isotherms, Brewster angle microscopy, and X-ray reflectance and diffraction methods are employed to investigate the structure of the Langmuir monolayers. The PAC is self-assembled from 1,3-bis[4'-oxa-(2,2':6',2' '-terpyridinyl)]propane, iron acetate, and dihexadecyl phosphate (DHP). Spreading the PAC at the air-water interface results in a monolayer that consists of two strata. DHP forms a monolayer at the top of the interface, while the metallosupramolecular polyelectrolyte is immersed in the aqueous subphase. Both strata are coupled to each other through electrostatic interactions. The monolayers can be transferred onto solid substrates, resulting in well-ordered multilayers. Such multilayers are model systems for well-ordered metal ions in two dimensions.

A bottom-up approach is presented for the production of arrays of indium islands on a molybdenum layer on glass, which can serve as micro-sized precursors for indium compounds such as copper-indium-gallium-diselenide used in photovoltaics. Femtosecond laser ablation of glass and a subsequent deposition of a molybdenum film or direct laser processing of the molybdenum film both allow the preferential nucleation and growth of indium islands at the predefined locations in a following indium-based physical vapor deposition (PVD) process. A proper choice of laser and deposition parameters ensures the controlled growth of indium islands exclusively at the laser ablated spots. Based on a statistical analysis, these results are compared to the non-structured molybdenum surface, leading to randomly grown indium islands after PVD.

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Using specular x­ray reflectivity, we have examined the vertical structure of charge coupled polyelectrolyte (PDADMAC)-lipid (DPPA) films on the water surface and on a silicon substrate, prepared by means of the Langmuir-Blodgett technique. The complicated structure of these films, characterized by electron density variations on the sub­nanometre scale and low density contrast between sub­layers, causes failure of the standard box model fitting method - it yields poor matching to data and/or ambiguous density profiles. We show that this problem can be overcome utilizing a different, model­free fitting method, which yields perfect fits and less ambiguous electron density profiles for all investigated films. The ambiguity of results can be further reduced when the sets of possible density profiles obtained for several similar samples are compared to each other. Discussing the model­free fitting method in detail along with general questions of reflectivity data evaluation, we aim to give practical instructions for the structure analysis of thin organic films. The obtained density profiles, being in good agreement with the structure model based on previous diffraction experiments, reveal some new details: The DPPA's phosphate head groups penetrate inside the PDADMAC helix rather than being bound onto its surface. The structure remains almost unchanged after transferring one layer onto Si wafer, but subsequently transferred layers exhibit decreasing order.

Indium islands on molybdenum coated glass can be grown in ordered arrays by surface structuring using a femtosecond laser. The effect of varying the molybdenum coated glass substrate temperature and the indium deposition rate on island areal density, volume and geometry is investigated and evaluated in a physical vapor deposition (PVD) process. The joined impact of growth conditions and spacing of the femtosecond laser structured spots on the arrangement and morphology of indium islands is demonstrated. The results yield a deeper understanding of the island growth and its precise adjustment to industrial requirements, which is indispensable for a technological application of such structures at a high throughput, for instance as precursors for the preparation of Cu(In,Ga)Se2 micro concentrator solar cells.

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