Materials Literature
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Side-chain fluorinated copolymers present very specific wetting and tacking properties that are strongly related to their organization. We have studied the structure of these systems by X-ray scattering in the liquid crystalline regime, as a function of the ratio of fluorinated groups on one hand and of the copolymeri…
The creation of a second-order nonlinear susceptibility ${\ensuremath{\chi}}^{(2)}$ in thermally poled silica glasses is known to be related to positive charge migration. As opposed to currently used models, we herein propose a model that takes into account charge dissociation and charge recombination occurring during…
Gold nanoparticles act as seeds for the growth of mesoporous silica shells according to the method described here for the synthesis of silica/gold nanocomposites. It is shown that the silica matrix is highly crystalline with mesopores that extend throughout the structure. The Figure depicts the procedure used and the…
The dielectric response of layered perovskite-related insulating ${\mathrm{SrNbO}}_{3.5}$ and conducting ${\mathrm{SrNbO}}_{3.41},$ ${\mathrm{SrNbO}}_{3.45},$ and ${\mathrm{La}}_{0.2}{\mathrm{Sr}}_{0.8}{\mathrm{NbO}}_{3.5}$ single crystals is investigated. The measurements are performed along the c axis, i.e., perpend…
We investigate numerically the structure of topological defects close to a spherical particle immersed in a uniformly aligned nematic liquid crystal. To this end we have implemented an adaptive mesh refinement scheme in an axi-symmetric three-dimensional system, which makes it feasible to take into account properly th…
We present three-dimensional simulations of field emission from single-wall and multi-wall carbon nanotubes. The structures considered are the metallic ideally open (5,5), (10,10), (15,15) and (5,5)@(10,10)@(15,15) nanotubes. For the multi-wall structure, flat and convex terminations are considered. The scattering cal…
Thermal conductivity, resistivity, Seebeck coefficient, and Hall measurements on polycrystalline Sn-clathrate compounds with the type-I hydrate crystal structure are reported. Interstitial alkali-metal atoms in these compounds reside inside polyhedral cavities formed by the tetrahedrally bonded Sn network atoms. Local…
An improved and efficient synthetic route to four functionalized bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF) derivatives 2-5 is reported. Tetrathiolate 1 was readily prepared from 2,2'-bis(1,3,4,6-tetrathiapentalen-5-one) under carefully controlled conditions. Subsequent reaction of 1 with selected primary alkyl…
Surface plasmon resonance of periodic narrow-grooved metallic thin films were studied with finite-difference time-domain simulations. Two distinguishable modes, surface plasmon polaritons and localized surface plasmons, are associated with different periods. The surface plasmon polaritons have widely extended near-fie…
We report first-principles total-energy electronic-structure calculations that provide energetics and electronic structures of double-walled BN nanotubes, $(n,0)$@(15,0) and $(m,0)$@(20,0). We find that the most favorable double-walled nanotubes studied here are (7,0)@(15,0) and (12,0)@(20,0) in which the interwall di…
Aligned calcite crystals have been grown in an hexagonal arrangement (see Figure) using highly oriented Au (111) films on monocrystalline mica substrates. This alignment is observed over distances larger than the dimensions of monocrystalline Au(111) domains. A change in nucleation face with pH during growth—reflectin…
A spine- or herringbone-like array of molecules characterizes the crystal structure of the organic semiconductor 2,5-bis(4-biphenylyl)thiophene (BP1T). Its bent molecular shape enforces an upright disposition of the molecular long axes against the ab-plane that parallels the crystal faces of the flake-like crystals (s…
Using results of first-principles band structure calculations and a model tight-binding approach, we investigate the local stability of the half-metallic ferrimagnetic (FiM) states in double perovskites ${\mathrm{Sr}}_{2}\mathrm{Fe}M{\mathrm{O}}_{6}$ $(M=\mathrm{Mo},$ Re, and W). In ordered compounds, a generalized do…
Tubular structures of an elementary bile steroid derivative (see Figure and front cover) can be obtained in dilute aqueous suspensions. They exhibit quite monodisperse cross sections (52 nm diameter) with a large inner cylindrical cavity of 49 nm diameter. The tubules can be easily oriented, which is a promising prope…
The conformational behavior of four [Ln(DOTA)(H(2)O)](-) systems (Ln = La, Gd, Ho, and Lu) has been characterized by means of ab initio calculations performed in vacuo and in aqueous solution, the latter by using the polarizable continuum model (PCM). Calculated molecular geometries and conformational energies of the…
The alkyltrimethylammonium templates, cited in the original patent for the preparation of MCM-41, have been replaced by a novel set of templates, 1-alkyl-3-methylimidazolium salts. Systematic studies have revealed subtle differences in the performance of the novel templates, and identify them as viable reagents in the…
Block copolymers were prepared by ring-opening polymerization of epsilon-caprolactone in the presence of monohydroxyl or dihydroxyl poly(ethylene glycol) (PEG), using Zn powder as catalyst. The resulting poly(epsilon-caprolactone) (PCL)-PEG diblock and PCL-PEG-PCL triblock copolymers were characterized by various anal…
We present fully atomistic molecular dynamics simulations for a realistic model of a glass-forming polymer: polyisoprene. The simulations are carried out at 363 K and extend until 20 ns. We calculate the self-part of the Van Hove correlation function G(s)(r,t), the mean-squared displacement <r(2)(t)>, the second-order…
We have evaluated the possible redox chemical methods for precisely determining the oxygen content in complex cobalt oxides that are being studied increasingly for their interesting electric and magnetic properties. For the evaluation, BaNdCo2O5 + δ and Sr2(Ca,Y)Co2O6 + δ phases are selected as reference materials to…
Thermally stable dipolar and octupolar (D2d, D3) NLO-phores are readily accessible by combining one, two, or three 4,4'-bis(dialkylaminostyryl)-[2,2']-bipyridyl ligands with zinc(II) salts. The off-resonant beta0 values point out the superiority of octupoles versus dipoles in terms of nonlinearity/transparency tradeof…