Publikationen

This paper presents a high-stability, single-phase hybrid polyelectrolyte (SPHP) applied in a large EC device (5×10 cm2) using WO3 (electrochromic) and CeO2-TiO2 (counter-electrode-ion storage) electrodes, both produced by Leibniz-Institut of New Materials (Leibniz-INM, Germany). The electrochromic device exhibited excellent color and bleach reversibility, high coloration efficiency (>35 cm2/C) from the first cycle up to more than 60,000 CA cycles, and a maximum constant rate of deintercalation/intercalation (Oout/Qin=1). Its remarkable behavior and high stability render this material an excellent candidate for application in electrochromic devices.

In this paper, we discuss the high stability of a single-phase hybrid polyelectrolyte (SPHP) and nanocomposite hybrid polyelectrolyte (NHP) in a large electrochromic (EC) device (5 cm × 10 cm) mounted with different electrodes. The electrochromic device (K-glass/FTO/WO3/SPHP/CeO2-TiO2/FTO/K-glass—ECI,K-glass/FTO/WO3/NHP/CeO2-TiO2/FTO/K-glass—ECII,) exhibited excellent color and bleach reversibility, high coloration efficiency (CE) (>35 cm2/C) from the first cycle up to more than 60,000 CA cycles, and a maximum constant rate of deintercalation/intercalation (Oout/Qin = 1). Also, the life time of the EC device with Nb2O5:Mo (K-glass/FTO/Nb2O5:O/SPHP/CeO2-TiO2/FTO/K-glass—ECIII) was prolonged to up to more than 10,000 cycles with a fairly stable coloration efficiency (around 19 cm2/C) and Oout/Qin = 1. The SPHP and NHP were tested in a large EC device with different configurations to evaluate its successful performance. In conclusion, its remarkable behavior and high stability render this material an excellent candidate for application in EC devices.

Conclusion. Silica nanoparticles may serve as a nonviral delivery system to the sensory hair cells, spiral ganglion cells within the cochlea, and the vestibular organ, as well as the cochlear nucleus. Objectives. At present there are no targeted therapeutics for inner ear disease. A variety of viral vector systems have been tested in the inner ear with variable efficacy but they are still not regarded as safe systems for inner ear delivery. Nanoparticles are a nonviral method of delivering a variety of macromolecules that potentially can be used for delivery within the auditory system. In this study, we evaluated the distribution and safety of nanoparticles in the inner ear. Materials and methods. Cy3-labeled silica nanoparticles were placed on the round window membrane of adult mice. Hearing thresholds were determined after nanoparticle delivery by auditory brainstem responses (ABRs). Distribution of particles was determined by histological evaluation of the cochlea, vestibular organs, and brain stem. Results. Fluorescent microscopy demonstrated Cy3-labeled nanoparticles signals in the sensory hair cells and the spiral ganglion neurons of both the treated and contralateral inner ears. Additionally, the distal part of the central auditory pathway (dorsal cochlear nucleus, superior olivary complex) was found to be labeled with the Cy3-linked silica nanoparticles, indicating a retrograde axonal transport. No hearing loss or inflammation was noted in the treated cochlea.

Layers of the metastable, amorphous HAIO are synthesized by chemical vapor deposilion from he molecular compound tert-buloxyalane ([tBu-O-AlH2]2). At temperatures above 500 °C, these layers transform to biphasic Al center dot AlO3 due to the elimination of di-hydrogen. The interaction of HAIO films with short laser pulses causes partial transformation of amorphous HAIO into nano-crystalline Al∙Al2O3. Using an interference pattern of two coherent high-power Nd:YAG laser beams produces local and periodic heating, inducing crystallization at equally distant lines in the HAlO layer. Depending on the laser fluence, different morphologies and different amounts of crystalline phases are obtained. In this study, the surface morphology and the distribution of crystalline phases of the structured samples are analyzed using SEM, FIB and TEM. The two-dimensional structures consist of periodic variations of morphology, chemical composition, and phase identity with a well-defined long-range order. When bio-functionalized, the structured samples may be used as carriers for structurally controlled cell-cultivation.

Phase-selective synthesis of crystalline vanadium oxides is achieved by the CVD of vanadium oxo-tri-isopropoxide [VO(OiPr)3]. Preformed V-O and V=O units and their differential thermal stability present in the precursor enabled precise modulation of the vanadium/oxygen stoichiometry in the products of the CVD. No additional oxygen carrier is employed during the deposition processes. Subject to deposition temperature (400-700 °C), different phase compositions (V2O5, V7O13, and VO2) are directly obtained and are investigated regarding structural and electrical properties. Hall measurements on VO2 films show a sharp metal-to-semiconductor transition at 78 °C (single crystal, 68 °C) depending on their microstructure formed by an oriented aggregation of individual crystallites.

Single-molecular magnesium-boron precursors [Mg(C3H6-BC8H14)2] and [Mg{C3H6-B(C6H11)2}2] were applied in chemical vapour deposition processes and characterized using SEM, XRD, XPS, AFM and MS methods towards their fragmentation behaviour, film morphology, phase formation and film composition. Depositon procedures in a temperature range from 500 to 1000 °C produced smooth and thin films with Mg and B in the ration 1:2. It could be shown that the contamination of the deposits by a considerably fraction of residual carbon could be reduced by post-deposition in-situ tempering or additionally sputter processes which may lead to improved deposition of MgB2-films.

A simple and useful experimental alternative to field-effect transistors for measuring electrical properties (free electron concentration nd, electrical mobility µ, and conductivity σ) in individual nanowires has been developed. A combined model involving thermionic emission and tunneling through interface states is proposed to describe the electrical conduction through the platinum-nanowire contacts, fabricated by focused ion beam techniques. Current-voltage (I-V) plots of single nanowires measured in both two- and four-probe configurations revealed high contact resistances and rectifying characteristics. The observed electrical behavior was modeled using an equivalent circuit constituted by a resistance placed between two back-to-back Schottky barriers, arising from the metal-semiconductor-metal (M-S-M) junctions. Temperature-dependent I-V measurements revealed effective Schottky barrier heights up to ΦBE=0.4 eV.

Individual tin oxide nanowires (NWs), contacted to platinum electrodes using focused ion beam assisted nanolithography, were used for detecting water vapor (1500-32 000 ppm) in different gaseous environments. Responses obtained in synthetic air (SA) and nitrogen atmospheres suggested differences in the sensing mechanism, which were related to changes in surface density of the adsorbed oxygen species in the two cases. A model describing the different behaviors has been proposed together with comparative evaluation of NW responses against sensors based on bulk tin oxide. The results obtained on ten individual devices (tested > 6 times) revealed the interfering effect of water in the detection of carbon monoxide and illustrated the intrinsic potential of nanowire-based devices as humidity sensors. Investigations were made on sensitivity, recovery time and device stability as well as surface-humidity interactions. This is the first step towards fundamental understanding of single-crystalline one-dimensional (1D) tin oxide nanostructures for sensor applications, which could lead to integration in real devices.

In order to improve the conductivity of Sb:SnO2 (ATO) films, very thin multi-walled carbon nanotubes (MWNTs) functionalized with -NH2 and -COOH groups have been investigated. The new nanocomposites were prepared by the addition of such MWNTs pre-dispersed in a cationic surfactant (Hexadecyltrimethyl ammonium chloride) in the ATO sol at concentrations of 0.05 and 0.1 wt%. Coatings of pure ATO and nanocomposites were prepared by spin coating on borofloat glass substrates. Experiments showed that all coatings containing nanotubes present resistivities of the order of 10-1 to 10-2 Ω cm while pure ATO films prepared under the same conditions show resistivities which are about 16 times higher. Optical transmission in the visible range of all systems studied was about 90%. The results indicate the suitability of MWNTs as additives for enhancing electrical properties of transparent conductive coatings.