Materials Literature
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In this letter, we report the results of phototunable lasing in dye-doped cholesteric liquid crystals (DD–CLC). Photoexcitation of DD–CLC films gives rise to laser emission in the violet-UV range. Control of the structure of the chiral dopant driven by UV phototransformation is exploited in order to obtain a permanent…
We studied the conditions under which optical gain is measured in nanocrystalline silicon (nc-Si) using the variable stripe length method. Waveguide samples have been produced by magnetron sputtering of alternating layers of Si and SiO2, followed by high temperature annealing. No optical gain was observed under contin…
The best solution? A highly crystalline hybrid silica has been obtained through the hydrolysis of a precursor in the solution phase. The self-organized structure of the lamellar material consists of diureido–phenylene bridging units (see picture); structural comparisons of this material and its molecular precursor sho…
We discuss electronic excitation processes at two ionic insulator surfaces, $\mathrm{L}\mathrm{i}\mathrm{F}(001)\mathrm{\text{\ensuremath{-}}}(1\ifmmode\times\else\texttimes\fi{}1)$ and $\mathrm{M}\mathrm{g}\mathrm{O}(001)\mathrm{\text{\ensuremath{-}}}(1\ifmmode\times\else\texttimes\fi{}1)$, within ab initio many-body…
The simulation of electron beam induced welding of crossed carbon nanotubes is considered with classical molecular dynamics simulations. Covalent junctions are predicted to form between various types of carbon nanotubes that contain many defects and are likely to be representative of experimentally welded nanotubes un…
Europium beta diketonates are easily synthesized highly luminescent complexes with high temperature sensitivity. We report on the temperature dependence of the luminescence of recently synthesized europium complexes originally prepared for use as light emitting diodes. It has been discovered that when incorporated in…
We investigate the thermal activated magnetisation reversal in a single ferromagnetic nanoparticle with uniaxial anisotropy using Monte Carlo simulations. The aim of this work is to reproduce the reversal magnetisation by uniform rotation at very low temperature in the high energy barrier hypothesis, that is to realiz…
We perform a theoretical study of a non-collinear Ising ferrimagnetic spin chain inspired by the compound Co(hfac)2NITPhOMe. The basic building block of its structure contains one Cobalt ion and one organic radical each with a spin 1/2. The exchange interaction is strongly anisotropic and the corresponding axes of ani…
We report simultaneous measurements of the permeability and effective porosity of oil-reservoir rock cores using one-dimensional NMR imaging of the penetrating flow of laser-polarized xenon gas. The permeability result agrees well with industry standard techniques, whereas effective porosity is not easily determined b…
We report a detailed set of ac magnetic measurements carried out on bulk large grain La-Ca-Mn-O samples extracted from a floating zone method-grown rod. Three samples with ${\mathrm{La}}_{0.78}{\mathrm{Ca}}_{0.22}{\mathrm{Mn}}_{0.90}{\mathrm{O}}_{x}$ stoichiometry but differing in their microstructure were investigate…
Single-crystalline whiskers of thermoelectric cobalt oxide, NaxCoO2, have been grown by an unconventional method from potassium-containing compositions, and their transport properties, and chemical compositions were determined. The growth mechanism was analyzed and interpreted by means of thermogravimetric analysis. A…
We present a simple method for the optical manipulation and spectroscopy of colloidal silver nanoparticles in aqueous solution using optical tweezers combined with dark-field microscopy. Because of their localized plasmon resonances, single trapped metal nanoparticles can be used as efficient near-field optical probes…
Autocatalysis during the thermal dehydrochlorination of poly(vinyl chloride) (PVC) is shown to be a free-radical process that converts the ordinary monomer units of the polymer into chloroallylic structures that have low thermal stabilities. In the first stage of dehydrochlorination, conjugated polyene sequences are c…
Fibers of single wall carbon nanotubes extruded from super-acid suspensions exhibit preferred orientation along their axes. We characterize the alignment by x-ray fiber diagrams and polarized Raman scattering, using a model which allows for a completely unaligned fraction. This fraction ranges from 0.17 to 0.05±0.02 f…
ZnS:Mn was produced in nanocrystalline form by a chemical method using polyvinylpyroledone as a chemical capping agent. Mn was stoichiometrically substituted for Zn in ZnS. The manganese (Mn) concentration was varied over its whole solid solution limit in ZnS, i.e., from 0 to 40%. In the high concentration regime this…
We investigated three different modeling approaches to simulate the crystallization behavior of Ge2Sb2Te5 in optical and, very recently, electrical phase-change memories. The first of these models is based on the Johnson–Mehl–Avrami–Kolmogorov (JMAK) formalism to calculate the fraction of crystallized material during…
We present a conduction model aimed at describing bipolar transport and space charge phenomena in low density polyethylene under dc stress. In the first part we recall the basic requirements for the description of charge transport and charge storage in disordered media with emphasis on the case of polyethylene. A quic…
Clusters of magnets: The first examples of manganese single-molecule magnets (SMMs) consisting exclusively of trivalent metal centers are reported. These are hexanuclear clusters containing the [MnIII6(μ3-O)2(μ2-OR)2]12+ core (see picture, Mn yellow, O red) and have an S=4 ground state. Variation of the oxygen-contain…
The magnetic and structural properties of cobalt-implanted ZnO single crystals are reported. High-quality, (110)-oriented single-crystal Sn-doped ZnO substrates were implanted at ∼350 °C with Co to yield transition metal concentrations of 3–5 at. % in the near-surface (∼2000 Å) region. After implantation, the samples…
Platinum, palladium, and silver nanotubes of 6–7-nm outer diameters are synthesized by the reduction of metal salts confined to lyotropic mixed-surfactant liquid crystals (see picture). The lyotropic liquid crystals act as a template and are formed by the 1:1 combination of medium and large surfactant molecules into a…