Materials Literature
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In this paper we report first-principles calculations on the ground-state electronic structure of two infinite one-dimensional systems: (a) a chain of carbon atoms and (b) a chain of alternating boron and nitrogen atoms. Meanfield results were obtained using the restricted Hartree-Fock approach, while the many-body ef…
We observe (by optical interferometry) the contact of a rubber cap squeezing a nonwetting liquid against a plate moving at velocity U. At low velocities, the contact is dry. It becomes partially wet above a threshold velocity V(c1), with two symmetrical dry patches on the rear part. Above a second velocity V(c2), the…
Abstract An influence of the structure of a globule of polyethyleneimine on the complex formation of one with the copper(II), nickel(II), and cobalt(II) ions is described. A change of the coordination number from the pH of solution for complexes of ethylenediamine, diethylenetriamine, and polyethyleneimine with metal…
The electronic structure and magnetocrystalline anisotropy energy of strained fcc ${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}$ have been studied by using the linear muffin-tin orbital method within density functional theory. A uniaxial strain applied along the [001] direction of the magnetite is considered. It is found that th…
Laser action in a dye-doped ferroelectric liquid crystal (FLC)—at the edge of the photonic stop band—has been demonstrated for the first time. The FLC used is a multicomponent mixture with a well-controlled short pitch of its helical structure whose periodic is equivalent to visible optical wavelengths. The laser emis…
Using computer simulations, we identify the mechanisms causing aggregation and structural arrest of colloidal suspensions interacting with a short-ranged attraction at moderate and high densities. Two different nonergodicity transitions are observed. As the density is increased, a glass transition takes place, driven…
Rare earth oxide nanotubes (see Figure) templated by dodecylsulfate assemblies have been fabricated for the first time by the homogeneous precipitation method using urea. Conversion into hollow nanotubes with an inner diameter of 3 nm and outer diameter of 6 nm can then be effected by anion exchange treatment to remov…
Adsorption of CO on Ni−ZSM-5 reveals the existence of two kinds of Ni 2+ ions, with the respective stretching frequencies being at 2220 and 2212 cm -1 . The carbonyl complexes are resistant to evacuation at room temperature, which is explained by the high electrophilicity of cations in a ZSM matrix. At 85 K and in the…
Thin polymer films with cylindrical microdomains of controlled size (see Figure for an AFM image) have been produced from diblock copolymer/homopolymer mixtures. It is demonstrated that not only do the spatial order and orientation of the domains remain unperturbed but also that two distinct sizes of pores can be acce…
The discrete nature of the vibrational modes of an isolated nanometer-scale solid dramatically modifies its low-energy electron and phonon dynamics from that of a bulk crystal. However, nanocrystals are usually coupled--even if only weakly--to an environment consisting of other nanocrystals, a support matrix, or a sol…
Using Korringa-Kohn-Rostoker coherent-potential approximation in the atomic-sphere approximation (KKR-ASA CPA) method for taking into account the effects of disorder, Gaspari-Gyorffy formalism for calculating the electron-phonon coupling constant $λ$, and Allen-Dynes equation for calculating T_c, we have studied the v…
The formation of hafnium silicate films (HfSixOy) for use as gate oxides with large dielectric constant by solid state reaction of Hf metal and SiO2 was investigated. Thin, fully reacted silicate films could be formed, and were thermally stable in vacuum to temperatures in excess of 800 C. The interface between a hafn…
The utilization of surface-attached gold nanoparticles as templates for generating Pt-group particles displaying near-optimal surface-enhanced Raman scattering (SERS) characteristics is described. Essentially epitaxial transition metal coatings down to the monolayer level can be prepared, most readily by the spontaneo…
The morphology of calcium carbonate can be tuned by using aqueous double-hydrophilic block copolymer (DHBC)–surfactant mixtures in a chemical synthesis. Calcite hollow spheres (see Figure) and vaterite discs were obtained at different concentrations of sodium dodecylsulfate (SDS) in a DHBC–SDS system. In contrast, pin…
Collagen-like peptides of the type (Pro-Pro-Gly)(10) fold into stable triple helices. An electron-withdrawing substituent at the H(gamma)(3) ring position of the second proline residue stabilizes these triple helices. The aim of this study was to reveal the structural and energetic origins of this effect. The approach…
Tellurium nanotubes with well-controlled structures (see Figure) are obtained via concentration depletion at the surfaces of seeds. The lengths of these inorganic nanotubes can be varied by adjusting the growth time (see cover), and the outer diameters of the tubes can be controlled by changing the initial concentrati…
Unusual two-dimensional ZnS nanosheets with micrometer scale lateral dimensions and flake-like ZnO dendrites (see Figure) can be rapidly generated with high yield (>96 %) by using a simple template method. The molecular precursor ZnS·(NH2CH2CH2NH2)0.5, which shows a strong ultraviolet emission band centered at 380 nm…
Lasers based on colloidal semiconductor nanostructures can benefit from the remarkable spectral coverage afforded through the quantum confinement effect. The first observation of lasing for colloidal CdSe/ZnS quantum rods in solution using a cylindrical microcavity is reported here (see also inside front cover). Lasin…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSubphthalocyanines: Singular Nonplanar Aromatic CompoundsSynthesis, Reactivity, and Physical PropertiesChristian G. Claessens, David González-Rodríguez, and Tomás TorresView Author Information Departamento de Química Orgánica (C−I), Facultad de Ciencias, Universidad Autónoma…
Phenylacetaldehyde (PhA) has been observed as a by-product in H2O2 metalloporphyrin catalytic oxidation of styrene. We have found that the mechanism of these oxidations depends on the relative amount of the carboxylic acid that is used as co-catalyst. With an excess of the organic acid less PhA is formed due to the in…