Materials Literature
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More than 10 000 carboxylic acid groups are covalently coated on monodisperse silica nanoparticles (see schematic diagram) prepared by a Stöber synthesis. Colloidal super crystals form spontaneously on dissociation in aqueous dispersion with low ionic strength.
Secondary hydrogen-bonding interactions have been exploited to construct layered magnetic solids based on amidinium–carboxylate salt bridges. The salt bridge is utilized as a supramolecular synthon to set the structural organization in a layered motif; it also serves as a spin communication element. The magnetic mater…
In this work, we add a small amount of a guest–host dye G-206 in the polymer-dispersed liquid crystal mixtures to fabricate holographic gratings. Following formation, the grating is irradiated by a single Ar+ laser beam while probed by a He–Ne laser. Experimental results indicate that the first-order diffracted intens…
We report a technique which allows self-assembly of conducting nanoparticles into long continuous chains. Transport properties of such chains have been studied at low temperatures. At low bias voltages, the charges are pinned and the chain resistance is exponentially high. Above a certain threshold VT, the system ente…
A novel type of electron-rich (basic!) nanosized channels can be built up by linking giant ring-shaped building blocks, which occur in the layered compound of composition [Mo124VIMo28VO429(μ3-O)28H14(H2O)66.5]16− (see figure). The corresponding sodium salt is obtained by reduction of an acidified aqueous molybdate sol…
Direct reaction of ytterbium or europium metal with 2,6-diphenylphenol yields novel lanthanoid aryloxides, including a unique diytterbium(II) cation with aryloxides solely as bridging ligands (figure).
The anisotropic magnetic susceptibilities of single crystals of the isostructural layered antiferromagnets, MnPS 3 ( T N = 78 K) and MnPSe 3 ( T N = 74 K), have been measured as functions of temperature. In both compounds, divalent manganese is present in the high-spin S = 5/2 state. The anisotropies in the susceptibi…
We report on the direct observation of stretched exponential relaxation in low-temperature monatomic Lennard-Jones systems which were cooled slowly from the liquid phase to form crystals with a large number of defects. We use the cage correlation function [E. Rabani, J. D. Gezelter, and B. J. Berne, J. Chem. Phys. 107…
An experimental atomic resolution analysis of an undoped Σ5 36° [001] tilt grain boundary in SrTiO3 shows that the structure contains incomplete oxygen octahedra. These incomplete octahedra act as effective oxygen vacancies and lead to a fixed, positive boundary charge. Annealing the boundary in the presence of MnO2 d…
Mixed-metal mesocates [M2Pd3Br6L6]4− (M=TiIV, SnIV; L=4-diphenylphosphanyl-catecholate) have been synthesized, in which the two incommensurate symmetry elements generated by the different metal ions are linked by a rigid, bifunctional ligand to generate a C3h-symmetrical cluster (see picture).
We study both the longitudinal and transverse fluctuations of a semiflexible filament. Using scaling arguments and numerical simulations, we find several regimes for the longitudinal fluctuations which, for short times, scale as $〈\ensuremath{\delta}{r}_{\ensuremath{\Vert}}^{2}〉\ensuremath{\sim}{t}^{7/8}$ and are corr…
The fine-tuning of the critical temperature and the coercivity of compounds with two interpenetrating quasi-perpendicular honeycomblike networks (see diagram) are presented. Molecule-based magnets of formula [(Etrad)2M2{Cu(opba)}3]⋅S and mixed compounds of formula [Etrad2Mn2−2xCo2xCu3] were synthesized and their magne…
A molecular composite prepared by the solubilization of pyrene in poly(propyleneimine) dendrimers is investigated by fluorescence and absorption spectroscopy at a range of pH values. The release of pyrene is induced in acidic media, while pyrene incorporation is favored in basic environments, as shown here.
The morphology of surfaces of arbitrary orientation in the presence of step and kink Ehrlich-Schwoebel effects (SESE and KESE) during growth is studied within the framework of a model in which steps are continuous lines, and is illustrated by a simple solid-on-solid model. For vicinal surfaces KESE induces an instabil…
Annealing of amorphous Si/SiO2 superlattices produces Si nanocrystals. The crystallization has been studied by transmission electron microscopy and x-ray analysis. For a Si layer thinner than 7 nm, nearly perfect nanocrystals are found. For thicker layers, growth faults and dislocations exist. Decreasing the a-Si laye…
The normal state conductivity of a system of interacting large polarons is calculated within the Random Phase approximation and some numerical results are presented. The behaviour of the optical absorption as a function of the charge carrier density and of the temperature is analyzed for different values of the electr…
This paper contains the notes of lectures on the theory of interlayer exchange coupling presented at the 30-th Ferienschule of the Institut fuer Festkoerperforschung, Forschungszentrum Juelich, March 1999.
New framework materials composed of well-defined vanadium oxide clusters were prepared by low-temperature reactions and characterized by X-ray crystal structure analysis. The structures of these solids contain {V18O42} cages linked into two interpenetrating three-dimensional networks by bridging {M(H2O)4} groups (M=Fe…
In a recent Letter, Roling et al. [Phys. Rev. Lett. 78, 2160 (1997)] proposed a novel scaling approach, requiring no arbitrary parameters, for the analysis of the ac conductivity resulting from ionic motion in glasses. However, this approach cannot be applied to alkali germanate glasses whose alkali content varies by…
Noncompatibilized and compatibilized ABS–nylon1010 blends were prepared by melt mixing. Polystyrene and glycidyl methacrylate (SG) copolymer was used as a compatibilizer to enhance the interfacial adhesion and to control the morphology. This SG copolymer contains reactive glycidyl groups that are able to react with PA…