Materials Literature
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The colloidal synthesis of ZnO−WO 3 heteroaggregates composed of 3−5 nm particles is presented. These sols can be used to prepare nanocrystalline ZnWO 4 xerogels, powders, and thin films with strong blue fluorescence (quantum yield between 25 and 50% at room temperature). The conversion of the precursor aggregates int…
HRTEM image of a single Ge nanocrystal. The image has been rotationally filtered to improve clarity. The lattice fringes imaged are for Ge 〈111〉, with a d spacing of 3.27 Å. Reaction between the Zintl salt NaGe and GeCl4 is shown to produce Ge nanocrystals. The reaction proceeds readily in refluxing diglyme at ambient…
Hydrothermal treatment of elemental indium and sulfur in the presence of the organic structure directing agent dimethylamine yields the novel open framework material DMA-InS-SB1. This material contains [In10S20]10- supertetrahedra that corner link to form an interpenetrating “double-diamond” lattice.
The origin of the first-sharp diffraction peak (FSDP) in supercooled liquid ${\mathrm{ZnCl}}_{2}$ (a network-forming, intermediate strength fluid) is studied by computer simulation. Measures are introduced to characterize voids in the spatial distribution of cations and the existence of transient layered structures an…
A strong enhancement of the 1.54 μm fluorescence of Er 3+ has been achieved in highly concentrated II−VI semiconductor quantum dot environments. A new preparation strategy allowed to incorporate up to 20 at. % Er 3+ into ZnS, CdS, and CdSe as well as ZnO semiconductor clusters and nanocrystals (sizes 1.5−5 nm). All cl…
A detailed analysis of polarization reversal in ferroelectrics has been performed, in the framework of the Landau model for phase transitions. Some important characteristics of homogeneous switching have been emphasized and later used in studying the more general case of inhomogeneous switching. The two extremes of sw…
Details of the synthesis and structural and physical characterization of oxides with the nominal composition NaTiO 2 are presented. The highest sodium loading we have achieved is Na 0.99(2) TiO 2 determined using diffraction methods. The results are not consistent with a localized moment d 1 system. High-resolution ne…
We present a theoretical and experimental study of the magnetic field dependence of the relaxation of the ${\mathrm{Mn}}_{12}{\mathrm{O}}_{12}$ acetate compound. For $T\ensuremath{\ge}2\mathrm{K}$ the molecule which starts from the $|\ensuremath{-}S〉$ state climbs to the excited states by means of thermal mechanism, w…
The dicarboxylate anions 1,4-benzenedicarboxylate and fumarate can be selectively intercalated into the layered double hydroxide [LiAl 2 (OH) 6 ]Cl·H 2 O from equimolar molar mixtures of the 1,2-, 1,3-, and 1,4-benzenedicarboxylate and fumarate and maleate isomers, respectively. Time-resolved in situ energy-dispersive…
The ability of a dendritic shell to afford site isolation to a porphyrin core was evaluated using electron-transfer experiments with a series of porphyrin-core dendrimers. Cyclic voltammograms show that surrounding a porphyrin site with even a small generation ( G ∼ 2) dendrimer can significantly lower the rate of int…
The equilibrium short-range order (SRO) in Cu-Pd alloys is studied theoretically. The evolution of the Fermi surface-related splitting of the (110) diffuse intensity peak with changing temperature is examined. The results are compared with experimental observations for electron-irradiated samples in a steady state, fo…
The site isolation of lanthanide cations (Er 3+, Tb 3+, and Eu 3+ ) has been achieved through the self-assembly of three convergent polyether dendrons, each with a carboxylate anion focal point, around the central trivalent cation. Evidence for the self-assembly of the dendritic complexes can be obtained by a variety…
The optical absorption of the colloidal nanoparticles is investigated, formed by the UV illumination of aqueous solutions containing AgClO 4 ((1−4) × 10 - 4 M), acetone (2 × 10 - 2 M), 2-propanol (1 M), and various polymer stabilizers. The 7 nm particles, which are produced in the presence of polyethyleneimine, posses…
We have developed a new approach for preparing graphitic carbon nanofiber and nanotube ensembles. This approach entails chemical vapor deposition (CVD) based synthesis of carbon within the pores of an alumina template membrane with or without a Ni catalyst. Ethylene or pyrene was used in the CVD process with reactor t…
Nitrile rubbers, both common and hydrogenated, revealed some kind of ordering, as detected by WAXS. Strain-induced crystallization is responsible for the enhanced degree of crystallinity for HNBR. In the case of NBR, another mechanism has been proposed, namely specific interactions between carbon-carbon double bonds f…
The profile of molecular orientation within injection-molded tensile bars of the liquid crystalline copolyesters Vectra A, Vectra B, and Vectra C, as well as blends of these polymers, was investigated by means of wide-angle X-ray scattering (WAXS) using synchrotron radiation (HASYLAB, Hamburg). The local variation of…
1,3,5-Triisopropoxy-1,3,5-tris(4-aminophenoxy)-cyclotriphosphazene-[CTP (I)], 1,3,5-trineopentoxy-1,3,5-tris(4-aminophenoxy)-cyclotriphosphazene [CTP (II)], and 1,1,3,5-tetraneopentoxy-3,5-bis(4-aminophenoxy)-cyclotriphosphazene [CTP (III)] were prepared from hexachlorotricylophosphazene. Thermal decomposition of the…
This article is a part of a study of model and bulk composites, based on isotactic polypropylene (i-PP) and glass (or carbon) fibers, produced from knitted textile preforms of hybrid yarns. First, we report the results on crystallization and fusion of textile-grade i-PP, used for the processing of hybrid yarns and the…
A study of the carboxymethylation of wood pulp cellulose and cotton linters cellulose in different organic media, namely, ethanol, acetone, and ethanol-acetone mixtures, is performed. Previously, the ethanol-acetone 1 : 1 (w/w) mixture used as reaction medium was found to give a higher degree of substitution (DS) than…
We support and generalize a weak selection rule predicted recently for the self-similar asymptotics of the distribution function (DF) in the zero-volume-fraction limit of Ostwald ripening (OR). An asymptotic perturbation theory is developed that, when combined with an exact invariance property of the system, yields th…