Materials Literature
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Making use of a combination of metal–ligand coordination interactions and solvophobic forces, an oligomer based on phenylacetylene incorporates Ag+ ions to form a highly ordered helical structure. The space-filling model shown makes clear the trigonal-planar coordination environment at silver.
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTControlled Growth of Gold Nanoparticles during Ligand ExchangeLeif O. Brown and James E. HutchisonView Author Information Department of Chemistry and the Materials Science Institute University of Oregon, Eugene, Oregon 97403-1253 Cite this: J. Am. Chem. Soc. 1999, 121,…
Die einzigartige Struktur von MCM-41-Silicaten (im Bild schematisch dargestellt) bietet äußerst attraktive Eigenschaften: einheitliche Porengrößen von mehr als 20 Å, innere Oberflächen von mehr als 1000 m2 g−1 sowie eine weitreichende Ordnung der Poren. Die Forschung auf dem Gebiet der mit supramolekularen Templaten h…
The electrical properties of dense nanocrystalline TiO2 ceramics with an average grain size of 35 nm were investigated by impedance spectroscopy and compared with a coarsened material with micron size grains. The nanocrystalline ceramics show an uncommon domain of ionic conductivity at high oxygen pressures and a stee…
Solutions of free base meso -tetraphenylporphyrin (H 2 TPP), meso -tetra(4-carboxyphenyl)porphyrin (H 2 TPPC), and meso -tetra(4-pyridyl)porphyrin (H 2 TPyP) under various conditions generate aggregates whose absorption spectra are characterized by invariant Soret bands with bandwidths that are independent of the prep…
The so-called “total yield” approach often fails to explain the measured sign of the surface potential, VS, and the shift of the nominal critical energy EC2∘ (where δ°+η°=1) of electron irradiated insulators. Here, a simple modification of this approach consists in including some extra interactions of the secondary an…
By means of an effective potential associated with a constrained equilibrium measure and apt to study frozen systems, we investigate glassy freezing in simple liquids in the hypernetted chain (HNC) approximation. Unlike other classical approximations of liquid theory, freezing is naturally embedded in the HNC approxim…
Several crystal structures of tungsten trioxide have been studied with a first-principles pseudopotential method. The electronic band gap increases significantly with the distortion of the octahedra that are the building blocks of the various crystal structures. Moreover, the tilting of the octahedra in the more compl…
A first-principles study of the birefringence and the frequency-dependent second-harmonic generation (SHG) coefficients of the ternary pnictide semiconductors with formula ${\mathrm{ABC}}_{2}$ $(A=\mathrm{Zn},$ Cd; $B=\mathrm{Si},$ Ge; $C=\mathrm{As},$ P) with the chalcopyrite structures was carried out. The zero-freq…
Using first-principles supercell calculations, we have investigated energetic, structural, and dielectric properties of three different ${A(B}^{\ensuremath{'}}{B}^{\ensuremath{''}}){\mathrm{O}}_{3}$ perovskite alloys: ${\mathrm{B}\mathrm{a}(\mathrm{Z}\mathrm{n}}_{1/3}{\mathrm{Nb}}_{2/3}){\mathrm{O}}_{3}$ (BZN), ${\mat…
The thermal diffusivity and heat capacity of uranium dioxide have been measured from 500 to 2900 K with an advanced laser-flash technique. These two quantities were determined simultaneously by means of an accurate numerical fitting of the experimental thermograms. At high temperatures the precision of the method used…
Previously published cosolvency models are critically evaluated in terms of their ability to mathematically correlate solute solubility in binary solvent mixtures as a function of solvent composition. Computational results show that the accuracy of the models is improved by increasing the number of curve-fit parameter…
The electronic-energy band structure, site and angular momentum decomposed density of states (DOS), and charge-density contours for ferroelectric sodium nitrite have been calculated using an accurate full-potential linear muffin-tin orbital method. The calculated total DOS is found to be in good agreement with experim…
We develop a method to incorporate the Kleinman-Bylander--type ab initio pseudopotential in the calculation of conductance in quantum wires using the Landauer formalism. This method is computationally efficient and mathematically stable; it does not involve singularity in inverting the transfer matrix. We also describ…
Fluorescence properties have been studied for Mn:ZnS crystallites with average diameter of 4 nm prepared by an aqueous colloidal method under 266 nm light excitation. The intensity ratio of the blue band at ∼430 nm to the orange band at ∼590 nm has decreased after the preparation on a time scale of hours in aqueous so…
Raman spectra of silicon nanowires (Si NW's) have been analyzed, and the observed Raman peaks were assigned. The typical features of the first-order Raman peaks of the optical phonons were found matching those predicted by the quantum confinement effect. However, the sizes of Si NW's, derived from the microcrystal mod…
The reduction of Ag + ions in N, N -dimethylformamide (DMF) is shown to take place spontaneously at room temperature. When no other additives are present in the system, the slow reduction leads to silver deposition on the glass walls of the container, while in the presence of 3-aminopropyltrimethoxysilane (APS) stable…
The history and character of macromolecular crystals principles of macromolecular structure and the applications of x-ray crystallography the purification and characterization of biological macromolecules some physical and energetic principles practical procedures for macromolecular crystallization important considera…
Rod-coil diblock copolymers in a selective solvent for the coil-like polymer self-organize into hollow spherical micelles having diameters of a few micrometers. Long-range, close-packed self-ordering of the micelles produced highly iridescent periodic microporous materials. Solution-cast micellar films consisted of mu…
We have measured the temperature-dependent thermal conductivity $\ensuremath{\kappa}(T)$ of crystalline ropes of single-walled carbon nanotubes from 350 K to 8 K. $\ensuremath{\kappa}(T)$ decreases smoothly with decreasing temperature, and displays linear temperature dependence below 30 K. Comparison with electrical c…