Materials Literature
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Oxygen intercalation into a pyrochlore at room temperature is reported. A simple chemical route was employed. Previously only perovskite or a few closely related phase have demonstrated an ability to act as hosts for such intercalation. The specific system studied was the interstitial solid solution Ce 2 Zr 2 O 7+ x (…
Using dynamic NMR spectroscopy, the kinetic isotope effects of the degenerate single hydron transfer in the conjugate 15 N-labeled porphyrin anion Por-H - dissolved in organic solvents have been measured as a function of temperature. Por-H - was generated by dissolving the labeled parent compound porphyrin together wi…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTHighly Enantioselective Epoxidation of trans-Stilbenes Catalyzed by Chiral KetonesDan Yang, Xue-Chao Wang, Man-Kin Wong, Yiu-Chung Yip, and Man-Wai TangView Author Information Department of Chemistry, The University of Hong Kong Pokfulam Road, Hong Kong Cite this: J. A…
A comprehensive electrochemical (cyclic and square-wave voltammetry, coulometry) and static spectroscopic (absorption, resonance Raman (RR), electron paramagnetic resonance (EPR)) study is reported for a series of dimeric and trimeric porphyrin-based arrays. All the arrays consist of tetraarylporphyrins linked via eth…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTn-Channel Organic Transistor Materials Based on Naphthalene FrameworksJoyce G. Laquindanum, Howard E. Katz, Ananth Dodabalapur, and Andrew J. LovingerView Author Information Bell Laboratories, Lucent Technologies 600 Mountain Ave., Murray Hill, New Jersey 07974 Cite th…
A set of porphyrin building blocks has been developed for the construction of light-harvesting model compounds and related molecular photonic devices. The porphyrins are facially encumbered to enhance solubility in organic solvents, are employed in a defined metalation state (free base (Fb) or zinc chelate), and bear…
We propose a minimal nonlinear model of brittle crack propagation by considering only the motion of the crack-tip atom. The model captures many essential features of steady-state crack velocity and is in excellent quantitative agreement with many-body dynamical simulations. The model exhibits lattice-trapping. For loa…
Soluble ethyne-linked tetraarylporphyrin arrays that mimic natural light-harvesting complexes by absorbing light and directing excited-state energy have been investigated by static and time-resolved absorption and fluorescence spectroscopies. Of particular interest is the role of the diarylethyne linkers in mediating…
A convenient procedure for the general preparation of bis(methylcyclopentadienyl)vanadium ( 1 ), bis(isopropylcyclopentadienyl)vanadium ( 2 ), and bis( tert -butylcyclopentadienyl)vanadium ( 3 ) and their blue monochloride ( 4 − 6 ) and green dichloride ( 7 − 9 ) derivatives is presented. The X-ray structures of compo…
Alcaligenes eutrophus genes encoding the enzymes, beta-ketothiolase (phaA), acetoacetyl-CoA reductase (phaB), and polyhydroxyalkanoate synthase (phaC) catalyze the production of aliphatic polyester poly-d-(-)-3-hydroxybutyrate (PHB) from acetyl-CoA. PHB is a thermoplastic polymer that may modify fiber properties when…
Luminescent films of porous silicon were obtained by laser ablation of crystalline silicon. The spectral and temporal characteristics of light emission from laser ablated porous silicon (LAPS) films critically depend on the chemical composition of the atmosphere in which they were fabricated. Luminescent characteristi…
We present for the first time a high-temperature x-ray absorption spectroscopy study of at the edge. The analysis both of the XANES and of the EXAFS regions shows that, in , a progressive localization of the 5d states following the temperature rise is accompanied at T > 350 K by a distortion of the octahedra, which in…
Thin films of colossal magnetoresistance (MR) material, La0.67Ca0.33MnO3, were implanted with different doses (1011–1015 ions/cm2) of 200 keV Ar+ ions. The implanted samples were examined by ion channeling and x-ray diffraction techniques. The channeling results clearly showed that the magnitude of the induced lattice…
It is demonstrated that a porous silicon (PS) optical cavity is available for the electroluminescence (EL) PS diode configuration. The PS diode is composed of a thin Au film, a light-emitting PS layer, a multilayered PS mirror, a p-type Si substrate, and an ohmic contact. When a sufficient bias voltage is applied to t…
The junction capacitance for a carbonaceous thin-film/n-type silicon layer photovoltaic cell made by chemical vapor deposition of 2,5-dimethyl-p-benzoquinone on a silicon substrate at 500 °C was measured, and an energy band diagram for this junction was sought out. The result confirms that the carbonaceous thin-film/n…
The theory of the nematic-smectic phase transition of uniform semiflexible chains with hard-core repulsion is presented. The flexibility of the chains is shown to result in a strong first-order transition. The calculated spinodal of the uniform nematic phase and the period of the modulation instability are consistent…
Lithium borate glasses containing were prepared and annealed. The results of deconvolution analysis of infrared spectra, molar volume and electrical conductivities (DC and AC) show that thallium ions are distributed as network formers in the glass matrix. The analysis of IR spectra shows that the formation of tetrahed…
The optical properties of chromium-doped sodium silicate glass synthesized under oxidizing conditions have been investigated. The method of preparation provides a large concentration of ions, but absorption and emission spectra showed that a small amount of (and ) ions are always present. The Dq-, B- and C-parameters…
Calorimetric measurements and undercooling investigations were performed on the high-melting, completely miscible binary systems (Co, Ni, Fe)-Pd. The alloys, characterized by phase diagrams with concavous liquidus and solidus lines, exhibit heat-of-fusion values considerably lower than calculated assuming ideal soluti…
The desorption of hydrogen from a novel material, a Ti45Zr38Ni17-H quasicrystal, was observed using high-temperature powder x-ray diffraction, demonstrating the potential utility of Ti-based quasicrystals in place of crystalline or amorphous hydrides for hydrogen storage applications. The maximum observed change in hy…