2015, Schirmer, Marie-Luis, Spannenberg, Anke, Werner, Thomas

The title compound, C17H18O5, was synthesized by a base-free catalytic Wittig reaction. The mol­ecule consists of a diethyl itaconate unit, which is connected via the C=C double bond to a benzo­furan moiety. The benzo­furan ring system (r.m.s. deviation = 0.007 Å) forms dihedral angles of 79.58 (4) and 12.12 (10)° with the mean planes through the cis and trans eth­oxy­carbonyl groups, respectively. An intra­molecular C-H...O hydrogen bond involving the O atom of the benzo­furan moiety is observed. In the crystal, mol­ecules are linked into ribbons running parallel to the b axis by C-H...O hydrogen bonds.

2015, Sonneck, Marcel, Peppel, Tim, Spannenberg, Anke, Wohlrab, Sebastian

In the mol­ecule of the title low-melting [alpha],[beta]-unsaturated carb­oxy­lic acid, C11H20O2, the least-squares mean line through the octyl chain forms an angle of 60.10 (13)° with the normal to plane of the acrylic acid fragment (r.m.s. deviation = 0.008 Å). In the crystal, centrosymmetrically related mol­ecules are linked by pairs of O-H...O hydrogen bonds into dimers, forming layers parallel to the (041) plane.

2016, Scheffler, C., Wölfel, E., Förster, T., Poitzsch, C., Kotte, L., Mäder, G., Madsen, Bo, Biel, A., Kusano, Y., Lilholt, H., Mikkelsen, L.P., Mishnaevsky Jr., L., Sørensen, B.F.

A commercially available carbon fiber (CF) with an epoxy-based sizing (EP-sized CF) and an unsized CF have been plasma treated to study the effect on the fiber-matrix adhesion towards a polypropylene matrix. The EP-sized fiber was chosen because of its predictable low adhesion in a polypropylene (PP) matrix. The fibers have been modified using a microwave low-pressure O2/CO2/N2-gas plasma source (Cyrannus®) developed at IWS in a batch process. One aim of this study was the evaluation of parameters using high energies and short time periods in the plasma chamber to see the effect on mechanical performance of CF. These results will be the fundamental work for a planned continuous plasma modification line. The CF surface was characterized by determining the surface energies, single fiber tensile strength and XPS analysis. The adhesion behavior before and after plasma treatment was studied by single fiber pull-out test (SFPO) and scanning electron microscopy (SEM). It was shown that the CO2- and O2-plasma increases the number of functional groups on the fiber surface during short time plasma treatment of 30 s. Carboxylic groups on the unsized CF surface resulting from O2-plasma treatment lead to an enhanced fiber-matrix adhesion, whereas the fiber strength was merely reduced.

2015, Alexander Schmidt, Markus, Argyros, Alexander, Sorin, Fabien

The field of hybrid optical fibers is one of the most active research areas in current fiber optics and has the vision of integrating sophisticated materials inside fibers, which are not traditionally used in fiber optics. Novel in-fiber devices with unique properties have been developed, opening up new directions for fiber optics in fields of critical interest in modern research, such as biophotonics, environmental science, optoelectronics, metamaterials, remote sensing, medicine, or quantum optics. Here the recent progress in the field of hybrid optical fibers is reviewed from an application perspective, focusing on fiber-integrated devices enabled by including novel materials inside polymer and glass fibers. The topics discussed range from nanowire-based plasmonics and hyperlenses, to integrated semiconductor devices such as optoelectronic detectors, and intense light generation unlocked by highly nonlinear hybrid waveguides.

2015, Becker, Lisanne, Spannenberg, Anke, Arndt, Perdita, Rosenthal, Uwe

The title compound, [Zr2(C10H15)4(C6H6N2)2]·C6H14, was obtained by the stoichiometric reaction of adipo­nitrile with [Zr(C10H15)2([eta]2-Me3SiC2SiMe3)]. Intra­molecular nitrile-nitrile couplings and deprotonation of the substrate produced the (1-imino-2-enimino)­cyclo­pentane ligand, which functions as a five-membered bridge between the two metal atoms. The ZrIV atom exhibits a distorted tetra­hedral coordination sphere defined by two penta­methyl­cyclo­penta­dienyl ligands, by the imino unit of one (1-imino-2-enimino)­cyclo­pentane and by the enimino unit of the second (1-imino-2-enimino)­cyclo­pentane. The cyclo­pentane ring of the ligand shows an envelope conformation. The asymmetric unit contains one half of the complex and one half of the hexane solvent mol­ecule, both being completed by the application of inversion symmetry. One of the penta­methyl­cyclo­penta­dienyl ligands is disordered over two sets of sites with a refined occupancy ratio of 0.8111 (3):0.189 (3). In the crystal, the complex mol­ecules are packed into rods extending along [100], with the solvent mol­ecules located in between. The rods are arranged in a distorted hexa­gonal packing.

2016, Kessler, Monty, Godemann, Christian, Spannenberg, Anke, Beweries, Torsten

The crystal structures of two ansa-titanocene tri-fluoro-methane-sulfonate complexes bearing the Me2Si(C5Me4)2 ligand are reported, namely [di-methylbis-(η5-tetra-methyl-cyclo-penta-dien-yl)silane](tri-fluoro-methane-sulfonato-κ2O,O')titanium(III) toluene monosolvate, [Ti(CF3O3S)(C20H30Si)]·C7H8, 1, and chlorido-[di-methyl-bis-(η5-tetra-methyl-cyclo-penta-dien-yl)silane](tri-fluoro-methane-sulfonato-κO)titanium(IV), [Ti(CF3O3S)(C20H30Si)Cl], 2. Both complexes display a bent metallocene unit, the metal atom being coordinated in a distorted tetra-hedral geometry, with the tri-fluoro-methane-sulfonate anion acting as a bidentate or monodentate ligand in 1 and 2, respectively. In 1, weak π-π stacking inter-actions involving the toluene solvent mol-ecules [centroid-to-centroid distance = 3.9491 (11) Å] are observed.

2015, Alebrahim, M.A., Krafft, C., Popp, J., El-Khateeb, Mohammad Y.

The structure and chemical features of the human dentin enamel junction (DEJ) were characterized using Raman spectroscopic imaging. Slices were prepared from 10 German, and 10 Turkish teeth. Raman images were collected at 785 nm excitation and the average Raman spectra were calculated for analysis. Univariate and multivariate spectral analysis were applied for investigation. Raman images were obtained based on the intensity ratios of CH at 1450 cm-1 (matrix) to phosphate at 960 cm-1 (mineral), and carbonate to phosphate (1070/960) ratios. Different algorithms (HCA, K-means cluster and VCA) also used to study the DEJ. The obtained results showed that the width of DEJ is about 5 pm related to univariate method while it varies from 6 to 12 μm based on multivariate spectral technique. Both spectral analyses showed increasing in carbonate content inside the DEJ compared to the dentin, and the amide I (collagen) peak in dentin spectra is higher than DEJ spectra peak.

2015, Sonneck, Marcel, Peppel, Tim, Spannenberg, Anke, Wohlrab, Sebastian

The crystal structure of (E)-dodec-2-enoic acid, C12H22O2, an [alpha],[beta]-unsaturated carb­oxy­lic acid with a melting point (295 K) near room temperature, is characterized by carb­oxy­lic acid inversion dimers linked by pairs of O-H...O hydrogen bonds. The carb­oxy­lic acid group and the following three carbon atoms of the chain of the (E)-dodec-2-enoic acid mol­ecule lie almost in one plane (r.m.s. deviation for the four C atoms and two O atoms = 0.012 Å), whereas the remaining carbon atoms of the hydro­carbon chain adopt a nearly fully staggered conformation [moduli of torsion angles vary from 174.01 (13) to 179.97 (13)°].

2015, Arndt, Perdita, Schubert,Kathleen, Burlakov, Vladimir V., Spannenberg, Anke, Rosenthal, Uwe

The crystal structure of the title compound, [Hf(C10H15)2(C4H9)2], reveals two independent mol­ecules in the asymmetric unit. The diffraction experiment was performed with a racemically twinned crystal showing a 0.529 (5):0.471 (5) component ratio. Each HfIV atom is coordinated by two penta­methyl­cyclo­penta­dienyl and two n-butyl ligands in a distorted tetra­hedral geometry, with the cyclo­penta­dienyl rings inclined to one another by 45.11 (15) and 45.37 (16)°. In contrast to the isostructural di(n-butyl)bis([eta]5-penta­methyl­cyclo­penta­dien­yl)zirconium(IV) complex with a noticeable difference in the Zr-butyl bonding, the Hf-Cbut­yl bond lengths differ from each other by no more than 0.039 (3) Å.

2016, Stiller, M., Barzola-Quiquia, J., Esquinazi, P., Spemann, D., Meijer, J., Lorenz, M., Grundmann, M.

The temperature and field dependence of the magnetization of epitaxial, undoped anatase TiO2 thin films on SrTiO3 substrates was investigated. Low-energy ion irradiation was used to modify the surface of the films within a few nanometers, yet with high enough energy to produce oxygen and titanium vacancies. The as-prepared thin film shows ferromagnetism which increases after irradiation with low-energy ions. An optimal and clear magnetic anisotropy was observed after the first irradiation, opposite to the expected form anisotropy. Taking into account the experimental parameters, titanium vacancies as di-Frenkel pairs appear to be responsible for the enhanced ferromagnetism and the strong anisotropy observed in our films. The magnetic impurities concentrations was measured by particle-induced X-ray emission with ppm resolution. They are ruled out as a source of the observed ferromagnetism before and after irradiation.