Materials Literature
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We report the first computer experiments with supercooled polymer melts of chains long enough to form chain-folded structures. These structures resemble the lamellae of polymer crystals, and the inverse of the lamellar thickness is related linearly to the crystallization temperature as found in experiments. The small-…
Silicalite nanoparticles and starch gel templates have been used to fabricate zeolite materials with a hierarchical micro/meso/macropore organization. Two methods were investigated. First, macroporous monoliths consisting of a continuous mesoporous framework of microporous silicalite were prepared by incorporating 50-…
ZnS and ZnSe precursors (ZnS x 0.5en and ZnSe x 0.5en, en = ethylenediamine) were prepared via a solvothermal process using ethylenediamine as solvent. Phase-pure hexagonal wurtzite ZnS and ZnSe products were obtained by annealing the precursors in argon stream at temperatures above 350 degrees C. The role of ethylene…
Metal, metal oxide, and plastic surfaces were modified with poly(vinylpyridine) using adsorption, spin-coating, and dip-coating techniques and various metal, semiconductor, and dielectric nanoparticles were subsequently attached. Prior to the modification, the substrates were treated with glow discharge plasma for cle…
124 Silberatome und 57 Selenidliganden enthält der Clusterkomplex [Ag124Se57(SePtBu2)4Cl6(tBu2P(CH2)3PtBu2)12]. Er hat Abmessungen von etwa 3 nm. Das Selenteilgerüst (siehe Bild) zeigt einen schalenartigen Aufbau mit einem Frank-Kasper-Polyeder (rot) im Zentrum. Außer der Struktur dieses Komplexes werden auch die von…
The dependence of the flow-induced isotropic-to-nematic (I−N) phase transition phenomenon on the spacer length is investigated using the well-behaved thermotropic polymers, PSHQ n, with n representing the number of methylene groups as flexible spacer in the main chain. Using optical microrheology methods and mechanica…
The kinetic study of the total oxidation of methane over a La 0.9 Ce 0.1 CoO 3 catalyst has been achieved. A discrimination among the five multistep rate-controlling models, preselected in a preceding study ( Stud. Surf. Sci. Cat. 2001, 133, 599−604), was carried out on the basis of experimental data from an integral…
Instantaneous normal modes (INM's) are calculated during a conjugate-gradient (CG) descent of the potential energy landscape, starting from an equilibrium configuration of a liquid or crystal. A small number (approximately equal to 4) of CG steps removes all the Im-omega modes in the crystal and leaves the liquid with…
The free energy of the supercooled liquid near freezing is studied in the density-functional approach using the modified weighted density approximation. A class of minima corresponding to heterogeneous structures characterized by weak mass localization are detected. The stability of these structures is found to be gre…
A tight-binding simulation of the atom-by-atom deposition of amorphous carbon (a-C) at 100 eV incident energy is presented. More than 500 atoms were deposited. Chains are observed to form on the surface, some of which are sputtered. The good agreement with the experimental sputter frequency data and observation that a…
The new oxothiomolybdate anion [Mo8S8O8(OH)8[HWO5(H2O)]]3- (denoted HMo8W3-) has been synthesized in aqueous solution by an acido-basic condensation reaction. Four (Mo(V)2S2O2) building blocks are connected through hydroxo bridges around a central [W(VI)O6] octahedron. X-ray and neutron diffraction studies have been p…
The interaction between trivalent lanthanide ions and the polyelectrolyte poly(vinyl sulfonate) (PVS) has been studied in aqueous solutions by monitoring lanthanide luminescence. The existence of specific binding of cations by PVS is indicated by blue-shifts in the maximum of the emission of cerium(III), effects on th…
Bicontinuous cubic (Q II ) phases composed of hydrated lipids are a unique mesoporous organic material. The diameter of the water channels in the range of 5−10 nm could be used as a reservoir for macromolecular therapeutic agents. Here, we describe the synthesis of water-soluble poly(amidoamine) (PAMAM) dendrimer deri…
Hypsochromic or bathochromic? Depending upon the acceptor group (A=H, CN, CHO, NO2) the position and intensity of the absorption maxima of a series of substituted oligo(phenylenevinylene)s change (see picture). Supported by semi-empirical calculations, the extent and direction of the shift (hypsochromic or bathochromi…
124 silver atoms and 57 selenido ligands are contained in the cluster complex [Ag124Se57(SePtBu2)4Cl6(tBu2P(CH2)3PtBu2)12]. The molecule has an approximate diameter of 3 nm. The selenium substructure (see picture) is formed of spheres with a central Frank–Kasper polyhedron (red). Apart from this silver selenide cluste…
We present results reflecting the analogies between the Kob-Andersen model and other glassy systems. Studying the stability of the blocked configurations above and below the transition we also give arguments that support their relevance for the glassy behavior of the model. However, we find, surprisingly, that the org…
New synthesis procedures are described to tetranuclear manganese carboxylate complexes containing the [Mn(4)O(2)](8+) or [Mn(4)O(3)X](6+) (X(-) = MeCO(2)(-), F(-), Cl(-), Br(-), NO(3)(-)) core. These involve acidolysis reactions of [Mn(4)O(3)(O(2)CMe)(4)(dbm)(3)] (1; dbm is the anion of dibenzoylmethane) or [Mn(4)O(2)…
The contribution of interface phonons to first-order Raman scattering in nanocrystals with nonspherical geometry is analyzed. Interface optical phonons in the spheroidal geometry are discussed and the corresponding Fr\"ohlich-like electron-phonon interaction is reported in the framework of the dielectric continuum app…
In this work, the evolution of gas-filled cracks under gas implantation and subsequent annealing is studied on the basis of an elastic continuum approach. The observed growth limitation of He-filled nanocracks in SiC is attributed to their stabilization by the formation of circular dislocation dipoles. The formation a…
Mesoporöse Materialien auf Silicat-Basis wurden erstmals in den frühen neunziger Jahren bei Mobil untersucht. Diese Verbindungen wiesen Porengrößen zwischen 20 und 500 Å sowie spezifische Oberflächen von bis zu 1500 m2 g−1 auf und wurden nach einem neuartigen Flüssigkristalltemplatansatz hergestellt. Die Methode wurde…