Publikationen

AbstractThe effects of engineered nanomaterials on human health are still intensively studied in order to facilitate their safe application. However, relatively little is known how mechanical strain as induced in alveolar epithelial cells by breathing movements modifies biological responses to nanoparticles (NPs). In this study, A549 cells as a model for alveolar epithelial cells were exposed to 25?nm amorphous colloidal silica NPs under dynamic and static culture conditions. Gene array data, qPCR, and ELISA revealed an amplified effect of NPs when cells were mechanically stretched in order to model the physiological mechanical deformation during breathing. In contrast, treatment of cells with either strain or NPs alone only led to minor changes in gene expression or interleukin-8 (IL-8) secretion. Confocal microscopy revealed that stretching does not lead to an increased internalization of NPs, indicating that elevated intracellular NP accumulation is not responsible for the observed effect. Gene expression alterations induced by combined exposure to NPs and mechanical strain showed a high similarity to those known to be induced by TNF-α. This study suggests that the inclusion of mechanical strain into in vitro models of the human lung may have a strong influence on the test results.

Abstract Due to their importance for the outcome of the inflammatory response, the motile myeloid cells are a focus of novel treatment options. The interplay of selectins and their ligands with leukocytes and endothelial cells, which mediate endothelial attachment and transmigration of immune cells, can be modulated by selectin-binding structures. Here, a library of selectin-targeting ligands coupled to either gold, silver, iron oxide nanospheres, or quantum dots of 5–10 nm in size is used to systematically study their impact on immune cell motility. The multivalent presentation of the carbohydrate mimetics results in very low sub-nanomolar binding to L-selectin. Using human primary monocytes, granulocytes, lymphocytes, and macrophages, it is shown that the ligands exhibit only minor effects on uptake, whereas the motility of leukocytes is critically affected as observed in migration assays evaluated by flow cytometry. The carbohydrate mimetic ring structure, sulfation, in particular, and the degree of ligand presentation, are constituents which cohere in this process. Specific carbohydrate ligands can thus selectively regulate leukocyte subsets. These data form the basis for advanced immunotherapy which inhibits the amplification of inflammation by restricting leukocyte influx to injured tissue sites. Furthermore, the targeting ligands may complement existing treatment options for inflammatory diseases.

Thin films of Transparent Conducting Oxide (TCO) using Aluminum and Galium doped Zinc Oxide (AZO and GZO) nanoparticulate suspension were doposited via simple wet chemichal deposition technique on borosilicate glass substrate. The electrical properties of the obtained films are competitive with similar layers made of tin doped indium oxide (ITO) suspension. GZO nanoparticles have smaller grain size and higher BET surface area than the AZO one. The GZO layers show better electrical conductivity than the AZO one, where a denser layer was obtained with higher charge carrier concentration and mobility. The obtained results are competitive to the reported result of tin doped indium oxide based on the similar method. Although the number of charge carriers of the metal doped zinc oxide layers are still not in a level to be replaced by ITO coatings, however it has larger charge carrier mobility, which is an emerging step to be developed to enhance the electrical conductivity of such cost effective materials. Both GZO and AZO layers exhibit a high transparency in the visible region for greater than 87%.

In this work, easy and simple structured perovskite solar cells (PSCs) are designed and characterized. Our effort was to reduce the cost of the fabrication of such PSC devices, first by using an inexpensive starting precursor (aqueous methylamine solution) for the perovskite materials and second by design in a PSC structure free of the expensive hole transport layer (HTL). The CH3NH3PbI3 perovskite sols were deposited onto a conductive FTO glass using the spin coating technique followed by heating at 100 °C for 10 min. The structure of the films was characterized by X-ray diffraction (XRD) and their optical properties by UV–VIS spectrophotometry and photoluminescence (PL). The obtained phase confirmed the formation of a tetragonal perovskite structure. Two different solvents have been used, dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). The effect of the type and the concentration of the used solvent DMF and DMSO on the performance of the solar cells have been investigated. It was found that a 40% concentration of the perovskite material resulted in the optimum film thickness that gives the best photoelectric performance. The DMF-based PSC assembled solar cell exhibited the best performance with an open circuit voltage of 750 mV, a photocurrent density of 12.5 mA/cm2, and an overall photon to electric conversion efficiency of 5.7%; all these results are higher than those of cells made with DMSO.

We propose a novel optical effect that involves switching the nonlinear refractive index of colloids and solutions by applying an external field. The third-order nonlinear optical properties of the colloidal aluminum-doped zinc oxide nanoparticles were studied using the z-scan technique by employing a polarized continuous-wave laser beam. To produce the anisotropic effect in the nanocolloids, an external electric field was applied. The nonlinear refraction index switches from minus values to positive ones as the magnitude of the electric field increases. Enhancement of linear and nonlinear absorption coefficients due to the amplitude of the electric field confirms potential application of the colloidal nanoparticles for optical switches. This phenomenon was described theoretically using the re-orientation effect and birefringence of the media. This effect could be interesting for application in nonlinear optical devices and sensors.

Tin doped indium oxide (ITO) thin films provide excellent transparency and conductivity for electrodes in displays and photovoltaic systems. Current advances in producing printable ITO inks are reducing the volume of wasted indium during thin film patterning. However, their applicability to flexible electronics is hindered by the need for high temperature processing that results in damage to conventional polymer substrates. Here, we detail the conditions under which laser heating can be used as a replacement for oven and furnace treatments. Measurements of the optical properties of both the printed ITO film and the polymer substrate (polyethylene terephthalate, PET) identify that in the 1.5–2.0 μm wavelength band there is absorption in the ITO film but good transparency in PET. Hence, laser light that is not absorbed in the film does not go on to add a deleterious energy loading to the substrate. Localization of the energy deposition in the film is further enhanced by using ultrashort laser pulses (~1 ps) thus limiting heat flow during the interaction. Under these conditions, laser processing of the printed ITO films results in an improvement of the conductivity without damage to the PET.

ZnO nanoparticles (NPs) were synthesized using solution combustion method with different urea percent (UP) i.e. U1, U2, U3 and U4. The obtained ZnO NPs were characterized using X-ray diffraction (XRD), high-resolution transmission electron microscope (HR-TEM), UV–Vis spectroscopy and photoluminescence spectroscopy (PL). XRD analysis confirmed the wurtzite structure of the prepared ZnO NPs and the estimated average crystallite size reduced from 28.03 nm to 17.33 nm with increasing of UP. HR-TEM image showed an irregular spherical shape for the prepared ZnO NPs. The absorption spectra analysis exhibited that the optical energy band gap (Eg) for the ZnO NPs increased with increasing of UP from 2.84 eV to 3.13 eV. Two groups (I and II) of dye sensitized solar cell (DSSCs) device based on the synthesized ZnO NPs were fabricated. In group I, 0.32 mM Eosin B (EB) used as photosensitizer for the samples U1, U2, U3 and U4, which showed that the overall conversion efficiency (η) increased from 0.09% to 0.13%, under a light intensity of 100 mW/cm2 due to the increasing of UP. Group II, different photosensitizer EB, Eosin Y (EY) and Rhodamine B (RB) used to sensitized the U4, where the EY exhibited the best all of them. The conversion efficiency presented a significant improvement from 0.13 to 1.26%. The combustion method can be considered as a promising method to produce good photoanode semiconductors such ZnO subsequently increase the efficiency of the solar cell.

Paper spray mass spectrometry (PSMS) is currently used in different analytical fields, but less effort has been made so far to use PSMS for highly polar compounds. Such analytes usually show poor performance in PSMS due to their high affinity for common paper substrates in addition to high matrix effects. In this study, strategies for hydrophobic modifications of commercially available paper substrates using ten different organosilanes were developed. The modified substrates were generated, characterized, and applied for PSMS analysis of polar toxins. By using the modified paper, PSMS performance of some of the toxins could be considerably increased, especially for orellanine, showing a more than 80-fold signal enhancement when substrates modified with chlorotrimethylsilane were used. For other toxins like ricinine, only small beneficial effects could be shown on PSMS performance when using modified substrates. Statistical equivalence tests showed sufficient ruggedness of the developed procedures also compared to conventional substrates. Thus, further systematic development of paper substrates modified with organosilane derivatives based on the presented study for application in PSMS should be encouraged.

The preparation of ordered macroporous SiCN ceramics has attracted significant interest and is an attractive area for various applications, e.g., in the fields of catalysis, gas adsorption, or membranes. Non-oxidic ceramics, such as SiCN, own a great stability based on the covalent bonds between the containing elements, which leads to interesting properties concerning resistance and stability at high temperature. Their peculiar properties have become more and more important for a manifold of applications, like catalysis or separation processes, at high temperatures. Within this work, a feasible approach for the preparation of ordered porous materials by taking advantage of polymer-derived ceramics is presented. To gain access to free-standing films consisting of porous ceramic materials, the combination of monodisperse organic polymer-based colloids with diameters of 130 nm and 180 nm featuring a processable preceramic polymer is essential. For this purpose, the tailored design of hybrid organic/inorganic particles featuring anchoring sites for a preceramic polymer in the soft shell material is developed. Moreover, polymer-based core particles are used as sacrificial template for the generation of pores, while the preceramic shell polymer can be converted to the ceramic matrix after thermal treatment. Two different routes for the polymer particles, which can be obtained by emulsion polymerization, are followed for covalently linking the preceramic polysilazane Durazane1800 (Merck, Germany): (i) Free radical polymerization and (ii) atom transfer radical polymerization (ATRP) conditions. These hybrid hard core/soft shell particles can be processed via the so-called melt-shear organization for the one-step preparation of free-standing particle films. A major advantage of this technique is the absence of any solvent or dispersion medium, enabling the core particles to merge into ordered particle stacks based on the soft preceramic shell. Subsequent ceramization of the colloidal crystal films leads to core particle degradation and transformation into porous ceramics with ceramic yields of 18–54%.