Materials Literature
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At U <1 V nearly the entire voltage in liquid crystals (LC) and in solutions of dyes in LC is applied to the near-electrode regions. In this range of voltages, the Schottky emission through a dielectric layer is the electric current flow mechanism transport. A thin (several nanometres) dielectric layer is formed throu…
Vier ausgehöhlte PW9O349−-Ionen (siehe Bild, blaue Polyeder) werden in den Heteropolyoxometallaten [(PM2W10O38)4(W3O14)]30− (M=Y, Eu) durch acht MIII-Ionen und sieben W-Atome zusammengehalten, welche zusammen ein [M8W7O30]6+-Gerüst aufbauen (Bildmitte). Im Festkörper besteht eine starke Wechselwirkung zwischen den Ani…
Upon continuous wave excitation around 1 μm, a YVO4 crystal codoped with ytterbium and holmium exhibits intense red emission originating in the F55 level and considerably weaker green emission originating in the S52 level of Ho3+. The ratio of the red to green emission intensities is 17:1 at 300 K. The dependence of t…
Nanoporous silica thin films with low dielectric constants were deposited by gas evaporation of SiO2 nanoparticles in an argon atmosphere. With increasing gas pressure during the evaporation, the dielectric constant decreases, while the porosity increases. The correlation between the dielectric constant and porosity i…
Polydentate bridging ligands can be used to link small polyoxo-alkoxo-metalate units to form supramolecular clusters. In the title compound, twelve μ4-bridging squarato groups connect eight trinuclear methoxo-oxo-vanadate units to form a tetradodecanuclear cubic framework (see picture), in whose cavity six n-butyl gro…
Bent by oxidation! A polyaniline (PAn, blue) coated cantilever acts as an electro-driven microdevice. Reversible oxidation/reduction of the PAn results in reversible deflection of the cantilever (see picture) originating from the electrostatic repulsion of the charged polymer chains of PAn2+ (green).
Ultrasound radiation can be used to synthesize a variety of mesporous materials. The reaction time is considerably shorter than the conventional methods. Ultrasonic waves can be further used for the insertion of amorphous nanosized catalysts into the mesopores. A detailed study demonstrates that the nanoparticles are…
Oxo anions of p- and d-block elements, for example, SiO(4)(4-), PO(4)(3-), SO(4)(2-), and CrO(4)(2-), are commonly encountered species. The full or partial replacement of the oxo ligands by isoelectronic imido (NR) groups generates homoleptic polyimido anions of the type [E(NR)(x)](z-) or heteroleptic imidooxo anions…
Exciton-coupled circular dichroism of the porphyrin Soret band of triblock copolymers prepared from chiral isocyanide monomers and an achiral tetraphenylporphyrin derivative (TPP) provides a novel method for determining the helical sense of poly(aryl isocyanide)s (see the schematic representation of the structure).
We consider the quantum properties of an elastic bar subject to compression. If strain rather than stress is held fixed, the system remains stable beyond the buckling instability, supporting two potential minima. The classical equilibrium transverse displacement is analogous to a Ginsburg-Landau order parameter, with…
Synthesis of highly ordered three-dimensionally interconnected mesoporous hydrocarbon polymer networks exhibiting Bragg X-ray diffraction is reported by replicating the mesoporous MCM-48 and SBA-15 channel frameworks.
Rigid, dendritic poly(paraphenylene)s are excellently suited as sensitive and selective coatings for gravimetric sensors (quartz microbalances), since they incorporate guest molecules reversibly into their interior voids. The variety of their potential designs allows an optimal match of these multitalented hosts to th…
Precise control of thermal evaporation deposition parameters allows the production of silver island films on glass substrates with tunable surface plasmon resonance wavelengths. Specific combinations of substrate temperature, deposition rate, and film thickness produce films exhibiting surface plasmon resonance wavele…
A strongly enhanced hysteresis with a width of &gt;34 °C has been observed in the semiconductor-to-metal phase transition of submicron-scale VO2 precipitates formed in the near-surface region of amorphous SiO2 by the stoichiometric coimplantation of vanadium and oxygen and subsequent thermal processing. This width…
The closest cubic approximant to the MCd5.7 (M = Ca, Yb) quasicrystals known so far, namely Ca13Cd76, was obtained by high-temperature reaction of the elements. It exhibits a new type of structure for intermetallic compounds with an unprecedented arrangement of triacontahedral clusters (see structure), which could pro…
Aligned, open-tipped carbon nanotube arrays of high density and uniformity were synthesized via a flame method on silicon substrates using a nanoporous template of anodized aluminum oxide from which the nanotubes were grown. The diameter and length of the nanotubes are controlled by the geometry of the aluminum oxide…
Using photoemission and inverse photoemission, we have been able to characterize the Cr2O3 oxide surface of CrO2 thin films. The Cr2O3 surface oxide exhibits a band gap of about 3 eV, although the bulk CrO2 is conducting. The thickness of this insulating Cr2O3 layer is twice the photoelectron escape depth which is abo…
Activated reactive evaporation has been used to grow copper oxide nanoparticles in the size range of 8–100 nm. X-ray diffraction spectra clearly show the presence of a single Cu2O phase. Detailed x-ray photoelectron spectroscopy studies show an increase in the ionicity of the Cu2O system with decreasing particle size.…
"Living"/controlled radical polymerization according to the atom transfer radical polymerization mechanism is a suitable method for the graft-polymerization of nanoparticles. With this method, in which the core nanoparticles remain unchanged, the chain length and therefore the thickness of the polymer shell can be adj…
The complete symmetry characterization of eigenstates in bare opal systems is obtained by means of group theory. This symmetry assignment has allowed us to identify several bands that cannot couple with an incident external plane wave. Our prediction is supported by layer-KKR calculations, which are also performed: th…