Scientific publications

When the polycyclic alumosiloxane [Ph2SiO]8[AlO(OH)]4 is allowed to react with either cyclopentadienyl sodium in tetrahydrofuran or with dimethyl zinc in diethyl ether the organic ligands on the metal elements are eliminated as cyclopentadiene or methane and the metals are bonded to oxygen atoms in the alumosiloxane forming [Ph2SiO]8[AlO2(Na)]4∙5(THF) or [Ph2SiO]8[AlO(OH)]2[AlO2]2[Zn(OH)]2∙2(OEt2), respectively. X-ray structure determinations reveal that in the sodium derivative the original polycycle rests almost unchanged while in the zinc derivative the inner skeleton is rearranged.

Bis(hexamethyldisilazyl)tin(II) in excess reacts with the molecular alumosiloxane (Ph2SiO)8(AlO(OH))4 to yield the well known tin(II) derivative (Ph2SiO)8(AlO2)4Sn2 and the novel bicyclic [(Me3Si)2N]Sn[N(SiMe3)SiMe2CH2]2Sn[N(SiMe3)2] containing a tin-tin bond, which is formally related to the starting molecule by a missing hydrogen atom. From X-ray diffraction studies on single crystals it follows that the new compound has almost C2 point symmetry (the twofold axis intersecting the tin-tin bond) and that this tin-tin bond is the fusion edge of anellated fivefold Sn-Sn-N-Si-C rings. The bond connecting the almost tetrahedrally coordinated tin atoms (2.737(2) Å) is astonishingly very short. This feature is also reflected in the spectroscopic data (1H, 13C, 21Si, 119Sn-NMR) of the compound with a coupling constant 1J (117Sn/119Sn) of 9529 Hz.

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.