Materials Literature
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Abstract The effect of crystallization from the glassy state (cold crystallization) on the oxygen‐barrier properties of copolyesters based on ethylene terephthalate with up to 10 mol % isophthalate, phthalate, or naphthalate was examined. Generally, crystallization affected diffusivity D more than solubility S; thus,…
Two efficient synthetic routes to the first tetrathiafulvaleno-annelated porphyrins are reported. These novel porphyrin systems (see picture; Pe=pentyl) have been characterized by using a variety of techniques including EPR spectroscopy, cyclic voltammetry, and mass spectrometry. Langmuir-Blodgett films obtained from…
Four tetramers of MoV centers and four tetramers of CoII centers, linked by phosphate groups around a central isolated [Co(H2O)6]2+ octahedron form the key structural unit (see picture) in the molybdenum(V) cobaltophosphates 1 and 2, which were prepared by hydrothermal synthesis. These units are connected to produce t…
We report a holographic polymer-dispersed liquid crystal cell whose reflection peak can be tuned as a function of applied voltage. Electro-optic results are presented which are in excellent agreement with our model based on coupled wave theory.
Strong up-conversion luminescence of ${\mathrm{Mn}}^{2+}$ is observed in ${\mathrm{Z}\mathrm{n}\mathrm{S}:\mathrm{M}\mathrm{n}}^{2+}$ bulk and nanoparticles. The up-conversion emission band excited at 767 nm is redshifted from the photoluminescence emission excited at 300 nm with the bulk and the particles encapsulate…
Calculations are presented for thermoelectric transport in quantum well and quantum wire superlattices, using (i), the full superlattice electronic band structure in (ii) a multisubband inelastic Boltzmann equation for carrier-phonon scattering. The transport direction is taken to be in the quantum well planes and alo…
Der Halogenidligand entscheidet über den Grundzustand bei den Komplexen 1. Der Chloridkomplex hat einen reinen St=3/2-Zustand, der Iodidkomplex einen reinen St=1/2-Zustand, und im Bromidkomplex liegen Moleküle mit St=3/2- und St=1/2-Zustand im Verhältnis 1:1 nebeneinander vor. Eine starke intramolekulare, antiferromag…
Anziehende Wechselwirkungen mit dem Kation überwinden die elektrostatische Abstoßung zwischen zwei Tetracyanoethylen-Radikalanionen [TCNE].− und führen zur Bildung eines diamagnetischen Dimers, [TCNE]22− (siehe Bild), beispielsweise in [K(glyme)]2[TCNE]2. Die Bindung wird als Zwei-Elektronen-vier-Zentren-Bindung inter…
Transported to the other side: Cyclic D,L-α-peptides self-assemble in lipid bilayers into transmembrane ion channels that may allow efficient transport of glutamic acid. The molecular transport is size/shape selective, as evidenced by the high transport rates observed with cyclodecapeptide-based transmembrane pores bu…
A hexadecamer, first-generation, octasilsesquioxane liquid-crystalline dendrimer was synthesized by a platinum-catalyzed hydrosilylation reaction of the parent first-generation vinyl octasilsesquioxane dendrimer with a modified, laterally substituted mesogen. The structure and purity of the octasilsesquioxane substrat…
Molecular strands composed of alternating 2,6-diaminopyridine and 2,6-pyridinedicarbonyl units have been designed to self-organize into single stranded helical structures upon forming intramolecular hydrogen bonds. Pentameric strands 11, 12, and 14, heptameric strands 1 and 20, and undecameric strand 15 have been synt…
A model is proposed here to explain how the chemical features of metal oxide varistors can alter their nonohmic physical behavior, based on nonohmic similarities in the electrical properties of ZnO- and SnO2-based varistors. The proposed model explains the electrical properties of ZnO- and SnO2-based varistors before…
A simple template-mediated route, starting from triethalolamine 1, sodium hydride or caesium carbonate, and iron(III) chloride led to the six- and eight-membered iron coronates [Na c [Fe6[N(CH2CH2O)3]6]]+ (2) and [Cs c (Fe8[N(CH2CH2O)3]8]]+ (3). In the reaction of N-methyldiethanolamine 4 (H2L1) or N-(2,5-dimethylbenz…
Optical absorption measurements were performed on irradiated diamonds containing different concentrations of nitrogen defects. Analysis of the results suggests that the single substitutional nitrogen centres trap vacancies about eight times more efficiently than the substitutional nitrogen pairs. In irradiated diamond…
The halide ligand determines the ground state for the complexes 1. The chloride complex has a pure St=3/2 state, the iodide complex a pure St=1/2 state, and the bromide complex contains both spin-state isomers (St=3/2 and 1/2) in a 1:1 ratio. Strong intramolecular antiferromagnetic exchange coupling between the FeIII…
Systems with long-range interactions when quenced into a metastable state near the pseudo-spinodal exhibit nucleation processes that are quite different from the classical nucleation seen near the coexistence curve. In systems with long-range elastic forces the description of the nucleation process can be quite subtle…
Attractive interaction with the cation overcomes the electrostatic repulsion between two tetracyanoethylene radical anions, [TCNE].−, and leads to the formation of a diamagnetic dimer [TCNE]22− (see picture), for example, in [K(glyme)]2[TCNE]2. The bonding is described as two-electron, four-center bonding arising from…
Electronic transport calculations were carried out for Bi1−xSbx nanowires (0⩽x⩽0.30) of diameters 10 nm⩽dW⩽100 nm at 77 K. A band structure phase diagram was generated, showing the dependence of the relative band edge positions on diameter and composition. Calculations of the thermoelectric figure-of-merit (ZT) predic…
selectivity at ≤120°C. Lewis acidity, redox properties, and a high surface metal oxide concentration are essential for good catalytic performance.
Water after-etching of porous silicon in an external electric field is studied. The application of the electric field, irrespective of its strength and orientation, is shown to decrease the etch rate. When the field vector is directed from the porous layer inward to the sample, the electrode potential in the silicon-e…