Materials Literature
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Highly stable, isolated, and monodisperse Ag nanoparticles, protected by poly(amidoamine) (PAMAM) dendrimers, were prepared via direct chemical reduction. UV−visible absorption, dynamic light scattering, and transmission electron microscopy have been used to study the structure and behavior of the nanocomposites as a…
The propionyl-CoA synthetase (PrpE) enzyme of Salmonella enterica catalyzes the first step of propionate catabolism, i.e., the activation of propionate to propionyl-CoA. The PrpE enzyme was purified, and its kinetic properties were determined. Evidence is presented that the conversion of propionate to propionyl-CoA pr…
We have prepared a green chromophore, 1,7-bis(pyrrolidin-1-yl)-3,4:9,10-perylene-bis(dicarboximide) (5PDI), that exhibits photophysical and redox properties similar to those of chlorophyll a (Chl a ), yet unlike Chl a, it can be easily functionalized and incorporated into a wide variety of biomimetic electron donor−ac…
We find that photoexcited electrons in an n-GaAs epilayer rapidly (< 50 ps) spin-polarize due to the proximity of an epitaxial ferromagnetic metal. Comparison between MnAs/GaAs and Fe/GaAs structures reveals that this coherent spin polarization is aligned antiparallel and parallel to their magnetizations, respectively…
We report the formation of open nanoporous polymer films composed of homogeneous polysulfone/polyimide blends. Porosity is introduced by expansion of carbon dioxide-saturated films at elevated temperatures. To interpret details of the porous morphologies in terms of the experimental conditions during expansion, the gl…
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…