Materials Literature
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NMR data have revealed that γ-alumina surfaces do not contain any three-coordinated Al atoms, despite the fact that their presence is expected on the basis of the bulk structure of the material. We report density-functional calculations of γ-alumina (110) surfaces that reveal a massive spontaneous reconstruction of th…
Pathways and generated surface species of adsorption and consequent surface reactions of acetone vapor on characterized silica, alumina, and ∼5 wt % silica−alumina were examined by in-situ infrared (IR) spectroscopy, following degassing at room (RT) and higher temperatures (100−400 °C). For reference and confirmatory…
We report on the synthesis and characterization of rod-shaped PbS nanocrystals dispersed in a polymer film using a functionalized lead(II) salt of the surfactant anion AOT -, Pb(AOT) 2, as the precursor. Essentially all the PbS nanocrystallites prepared using this method have been oriented with their (100) lattice pla…
The continuous random network (CRN) model is an idealized model for perfectly coordinated amorphous semiconductors. The quality of a CRN can be assessed in terms of topological and configurational properties, including coordination, bond-angle distributions and deformation energy. Using a variation on the sillium appr…
The performance of various density functional approaches for the calculation of electron paramagnetic resonance (EPR) hyperfine coupling constants in transition metal complexes has been evaluated critically by comparison with experimental data and high-level coupled-cluster results for 21 systems, representing a large…
A heating treatment strategy for inducing size and shape change of composite nanoparticles in solutions is described. The composite nanoparticles are ∼2 nm gold cores encapsulated with alkanethiolate monolayers. The development of abilities in size and shape controls constitutes the motivation of this work. We demonst…
Epoxy resin is moulded to produce high voltage insulation components. To release the component from the mould, among other techniques, silicon-based release agents are used. The authors demonstrate that release agent is absorbed by resin during casting, and describe the change in reaction to electrical discharge stres…
Micrometer thick coatings of the hydroxides of La and Nd can be electrodeposited on stainless steel substrates by cathodic reduction of aqueous solutions of the corresponding nitrates. The coatings are uniform, adherent, and stable to thermal treatment up to moderate temperatures. At high temperatures (>900 °C), the c…
GRLite and GRTensorJ are first and second generation graphical user interfaces to the computer algebra system GRTensorII. Current development centers on GRTensorJ, which provides fully customizable symbolic procedures that reduce many complex calculations to "elementary functions". Although still in development, GRTen…
Trotz ähnlicher Ringdeformationen in Lösung und im Festkörper weist das synthetische Chloroeisen(III)-Derivat von 2,3,7,8,12,13,17,18-Octaethyl-5,10,15,20-tetraphenylporphyrin (oetpp), [FeCl(oetpp)] (hier schematisch dargestellt), nur eine sehr schwache quantenmechanische Beimischung eines S=3/2-Spinzustands (nur 4–10…
Shape-selective catalysis is important for synthesis of organic chemicals and for processing of petroleum fractions and fuels. This article provides an introductory overview of the principles and applications of shape selective catalysis. It also discusses current areas of research on shape-selective catalysis.
Ein vierfach substituiertes Derivat von 1,4,7,10-Tetraazacyclododecan mit koordinierenden Amidgruppen und seitlichen, nichtkoordinierenden Phosphonatgruppen bildet einen Komplex (siehe Struktur) mit Gadolinium(III), der ein langsam austauschendes Innensphärenwassermolekül enthält (τM=21 μs). Die 20-MHz-Wasserprotonenr…
Riesenpolyoxometallate mit katalytischen, magnetischen und antiviralen Eigenschaften, die zumindest teilweise auf ihre Strukturen zurückzuführen sind, sind derzeit von großem Interesse. Hier wird die Synthese und Charakterisierung von 1 beschrieben, einem strukturell neuartigen tetrameren Komplex aus Keggin-Ionen (sie…
Ein neuartiger Austausch von Liganden und Gastmolekülen läßt sich an molekularen Riesenkugeln (Beispiel siehe Bild) vornehmen, die sich in Lösung mit entsprechenden Riesenkörben im Gleichgewicht befinden.
A new series of acceptor-substituted nickel tetraphenylporphyrins were synthesized in order to examine the efficiency of the π-conjugation through the olefinic linkages to the β-carbon of porphyrins. Perturbed absorption spectra were found for the substituted porphyrins and may be attributed to the reduced symmetry of…
Despite similar ring deformations in solution and in the solid state, the chloroiron(III) derivative of 2,3,7,8,12,13,17,18-octaethyl-5,10,15,20-tetraphenylporphyrin ([FeCl(oetpp)], shown schematically) prepared in this study exhibits only a very weak quantum-mechanical admixture of spin S=3/2 (only 4-10 %) with spin…
Modern research is increasingly focusing on structuring matter on a nanometer length scale rather than producing molecularly new species. This article describes a method for synthesizing porous solids from rigid colloidal templates in three steps (see scheme): a) assembly of colloidal particles into a regular array, b…
Pythagoräische Harmonie besteht bei den hier beschriebenen kugelförmigen Polyoxometallat-Clustern (Strukturbeispiel siehe Bild), da es interessante Beziehungen zwischen den sogenannten magischen Zahlen (12, 32, 42, 72, 132; für sphärische Viren relevant) und der Zahl der Baueinheiten der Cluster gibt. Die Größe dieser…
A novel exchange between ligands and/or guest molecules can be accomplished in giant molecular spheres (an example is shown in the picture) which are in equilibrium with the corresponding giant baskets in solution.
Giant polyoxometalates with catalytic, magnetic, and antiviral properties, which are in part attributable to their structures, are currently of great interest. Herein is described the synthesis and characterization of 1, a structurally novel tetrameric complex from Keggin ions (see picture). This complex is stable und…