Structure and internal rotation in 3-phenylthiophene using NMR spectra of liquid-crystalline solutions

The NMR spectra of 3-phenylthiophene as solute in liquid-crystal solvents were analyzed and the direct couplings constants, D_ij obtained were used to test different models of the potential energy function V(φ) for intramolecular rotation of the phenyl and thiophene units. The data are consistent with a V(φ) having a minimum at about 24°. The LCNMR technique is highly discriminant among different models of V(φ) provided that enough D_ij couplings are available. Ab initio calculations are also reported.     

单层2H-MoTe2光电效应的理论研究

材料的禁带宽度是影响光电探测器探测范围的重要因素.单层2H-MoTe2因具有合适的禁带宽度引起了科研人员广泛的研究兴趣.本文基于非平衡态格林函数-密度泛函理论,采用第一性原理方法,研究了单层2H-MoTe2的光电效应.结果表明:在线性偏振光照射下,MoTe2产生的光电流函数与唯象理论相吻合;在光子能量范围1.6～1.8...     

Effet Kerr magnetique microonde du type Faraday dans les semiconducteurs

The Faraday-type magneto-microwave Kerr effect in semiconductors at weak magnetic fields has been studied in the domain where the influence of the carrier inertia is low but not negligible. After stating the expressions connecting the rotation and the ellipticity of the reflected wave to the material parameters we have applied these results to the determination of Hall mobility and shown that a precise determination of this mobility must usually be realised from both rotation and ellipticity effects.The experimental study has been achieved with a recording interferential reflecto-polarimeter. This apparatus being particularly well suited to this study has not yet been used for this kind of measurements. We have thus determined precisely the Hall mobility of various semiconductor samples at 16 GHz and at room temperature.     

Carbazole and Diketopyrrolopyrrole-Based D-A π-Conjugated Oligomers Accessed via Direct C–H Arylation for Opto-Electronic Property and Performance Study

Five carbazole and diketopyrrolopyrrole-based donor-acceptor (D-A) new π-conjugated oligomers (π-COs) with gradually elongated lengths are facilely synthesized via a single pot of direct C–H arylation with merits of atom- and step-economy. The structure-property-performance correlations of these π-COs and their parent polymer are studied in detail by opto-electronic characterizations and bulk heterojunction (BHJ) organic photovoltaic (OPV) devices. It is found that the π-COs having longer lengths enable better performance in OPVs owing to the enhanced intermolecular interaction with the elongation of the conjugations. The above results not only highlight the powerful synthetic strategy here provided, but also reveal that π-COs with unique properties might find promising application in OPVs.     

Molecular dynamics simulation of liquid CH2Cl2 with 3×3 and 5×5 site-site interactions

A molecular dynamics simulation of liquid CH₂Cl₂ is compared with the far infrared spectrum at the same state point (293K, 1 bar). Two representations of the force field are used, a 3×3 and 5×5 site-site interaction consisting of Lennard-Jones and charge terms. The far infra-red spectrum shows unambiguously that the 5×5 representation is more realistic in the sense that it reproduces the observed spectrum more closely.     

Synthesis and Structural Characterization of a Di-nuclear Uranyl Complex with Quinoline-6-carboxylate

Crystallography Reports - A di-nuclear uranyl complex with the formula of [(UO2)2(L)4(H2O)2]?4H2O (1) (HL = quinoline-6-carboxylic acid) was synthesized hydrothermally and characterized by...     

Influence of Si/Al ratio on the catalytic properties of NiH mordenite in the disproportionation of toluene

The disproportionation of toluene on dealuminated NiH mordenites has been studied in order to understand the influence of the Si/Al ratio on the activity, selectivity and stability of these catalysts.Four dealuminated H mordenites were prepared by combined treatments of calcination under wet air and boiling HC1 solution; the atomic Si/Al ratio of the framework, determined by ²⁹Si NMR spectroscopy, varied from 5 to 29.3.A maximum of activity was obtained for a Si/Al ratio of ~12.6. This catalytic behaviour is explained by the influence of the Si/Al ratio on the acidity and also by strong diffusional limitations for the non-dealuminated catalyst.The most active catalyst is also the most selective in aromatic compounds. On the other hand, the non-dealuminated catalyst is the least selective, as explained by a strong hydrogenolysis activity.The decrease of selectivity in aromatics of the dealuminated NiH mordenites after ageing can be explained by the activation of some of the nickel which was not previously reduced, and also by the higher temperatures of the catalytic tests, which favour the hydrogenolysis and hydrocracking reactions.     

Magnetoelastic effects in La1−xCexB6

The elastic constants of La_1−xCe_xB₆ (x = 0.00, 0.01, 0.03) single crystals were determined by ultrasonic measurements. The temperature dependence of the elastic symmetry modes c₄₄ and (c₁₁ − c₁₂)/2 is explained on the basis of the crystalline-electric-field level scheme of CeB₆ by taking the magnetoelastic interaction into account. An influence of the Kondo effect on the elastic constants could not be detected.     

Vibrational modes induced by a pair of impurities

Presence of a polarizable impurity atom in an ionic crystal induces a localized vibrational mode of the lattice. The frequency of the mode is distinct from the propagating modes of the pure crystal. It is shown in this paper that the frequency of the mode depends on the polarizability of the impurity atom and on the distance of separation between two adjacent impurities.     

Effect of ultrasound on ammonium leaching of zinc from galmei ore

The effect of ultrasound on ammonium leaching of zinc from galmei has been investigated. The use of an ultrasonic field allows the leaching time to be decreased by a factor of ten on account of the decrease in the diffusion layer thickness on the surface of the galmei which has been leached.