Crystal and Molecular Structure of Copper (Ⅱ) Dimeric Complex of S-Methyl-β-N-(Pyridine N-Oxide-2-ylmethylidene) Dithiocarbazate with Acetonitrile

The crystal and molecular structure of copper(Ⅱ) dimeric complex of S-methyl-B-N-(pyridine N-oxide-2-ylmethylidene) dithiocarbazate with acetonitrile, [CuL (CH3CN)]2 (ClO4)2, was determined by X-ray diffraction. The complex crystalizes in monoclinic system with space group P21/n, a= 7. 685(2), 6=20.160(6), c= 10. 847(5) A ,B = 107.89(3), Z=2,Dc=1.788 g/cm3, F(000) = 835. 8, u= 18. 17 cm-1(Moka,R= 0. 057.Each Cu(Ⅱ) ion in the complex is surrounded by a distorted square pyramidal. The basal plane is comprised of S, N and O atoms of one ligand together with a N atom of the solvent--acetonitrile, while the axial position is occupied by the S atom of the other ligand. The bond length of Cu-S(bridging) is 3. 038A . and Cu-Cu distance is 3. 700A.     

Synthesis of novel diastereomeric diphosphine ligands and their applications in asymmetric hydrogenation reactions

[structure: see text] Diastereomeric biaryl diphosphine ligands 10 and 11 with added chiral centers on the backbone were synthesized. Substrate-directed asymmetric synthesis occurred in the coupling step of the preparation of the diastereomeric diphosphine oxides. The diastereomeric diphosphine oxides were easily separated by column chromatography with silica gel. Ruthenium catalysts containing these ligands were highly effective in the hydrogenation of 2-(6'-methoxy-2'-naphthyl)propenoic acid and beta-ketoesters. The additional chiral centers had a significant influence on the enantioselectivity and activity of the catalysts.     

Chirp elimination using a linearly chirped fiber grating

Gain-switched distributed feedback laser diodes (GS-DFB-LD) with high repetition bit rate have large frequency chirp. Conventionally, the F–P spectrum filter and normal dispersion fiber were used to eliminate chirp in GS-DFB-LD pulse sources. In this paper, a new method for eliminating chirp of high repetition pulses generated from DFB laser diodes is proposed. The use of a linearly chirped fiber grating for chirp elimination is discussed theoretically and numerically. A new apodized coupling profile function for the grating, which we call it the inverse Gaussian, is given. Its characteristics are analyzed and compared with other profiles. The numerical results are in agreement with the theoretical analysis.     

Tris(2,2′-bipyridyl)ruthenium(II) electrochemiluminescent determination of ethyl formate

Analytical and Bioanalytical Chemistry - Ethyl formate is extensively used as food flavor, fungicide, and larvicide. It naturally exists in coffee, fruits, honey, brandy, and rum as well as dust...     

Plastic relaxation of mixed dislocation in axial nanowire heterostructures using Peach–Koehler approach

In this Letter, the plastic relaxation introduced by typical 60° mixed dislocation in zinc‐blende axial nanowire (NW) heterostructures is evaluated by numerical Peach–Koehler approach which reflects the interaction between coherent strain field and misfit dislocation. Cylindrical NW epilayers grown on NW and bulk substrate are separately modeled. We reveal that straight 60° dislocation with Burgers vector (a /2) 〈101〉 would always generate at NW center orienting [111], while aspect ratio dependent off‐center equilibrium position should be expected for NW epilayer along [001]. Moreover, the critical diameters, below which coherency is maintained, are predicted based on energy balance criterion for axial NW heterostructures along predominating growth direction [111]. The results are compared with existing theory and experimental observations. Our work provides a necessary quantitative complement to the understanding of plastic relaxation and coherency limit in axial NW heteroepitaxy. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Slight disorder effects in two dimensional photonic crystal structures

In the actual manufacturing process of photonic crystal structure, unavoidable error can generate slight disorder which may influence the performance of photonic crystal based device. In this work, randomly distributional disorders are applied to the air holes in the photonic crystal structure. Based on this, we investigate the influence of the slight disorder on the photonic crystal band structure and the performance of photonic crystal based devices (waveguide and slab cavity). The studies indicate that the slight disorder provides small influence on the band structure of the photonic crystal. But, the random disorder in photonic crystal waveguide may increase transmission loss obviously when the wavelength of the light and the distribution of disorder break the balance of multiple interferences. Also, the slight disorder can reduce the Q factor of the photonic crystal cavity at a certain degree. The studies may provide some useful guides for further photonic crystal device research.     

Novel superhard carbon: C-centered orthorhombic C8

A novel carbon allotrope of C-centered orthorhombic C(8) (Cco-C(8)) is predicted by using a recently developed particle-swarm optimization method on structural search. Cco-C(8) adopts a sp(3) three-dimensional bonding network that can be viewed as interconnected (2,2) carbon nanotubes through 4- and 6-member rings and is energetically more favorable than earlier proposed carbon polymorphs (e.g., M carbon, bct-C(4), W carbon, and chiral C(6)) over a wide range of pressures studied (0-100 GPa). The simulated x-ray diffraction pattern, density, and bulk modulus of Cco-C(8) are in good accordance with the experimental data on structurally undetermined superhard carbon recovered from cold compression of carbon nanotube bundles. The simulated hardness of Cco-C(8) can reach a remarkably high value of 95.1 GPa, such that it is capable of cracking diamond.     

Colloidal Self‐Assembly of Catalytic Copper Nanoclusters into Ultrathin Ribbons

Metal nanoclusters (NCs) with diameter below 2 nm are promising catalysts in oxygen reduction reactions (ORR). However, the high surface energy of ultra‐small clusters leads to structural instability, shedding doubt on practical applications. Herein, we demonstrate a self‐assembly method to improve the durability of catalytic metal NCs, employing copper NCs capped by 1‐dodecanethiol (DT) to form free‐standing ribbons in colloidal solution. By tuning the cooperation between the dipolar attraction between Cu NCs and the van der Waals attraction between DT, the thickness of ribbons is adjusted to a single NC scale. Such free‐standing ribbons exhibit excellent catalytic activity and durability in ORR.     

Electrochemiluminescence Detection of TNT by Resonance Energy Transfer through the Formation of a TNT–Amine Complex

2,4,6‐Trinitrotoluene (TNT) is a widely used nitroaromatic explosive with significant detrimental effects on the environment and human health. Its detection is of great importance. In this study, both electrochemiluminescence (ECL)‐based detection of TNT through the formation of a TNT–amine complex and the detection of TNT through electrochemiluminescence resonance energy transfer (ECRET) are developed for the first time. 3‐Aminopropyltriethoxysilane (APTES)‐modified [Ru(phen)₃]²⁺ (phen=1,10‐phenanthroline)‐doped silica nanoparticles (RuSiNPs) with uniform sizes of (73±3) nm were synthesized. TNT can interact with APTES‐modified RuSiNPs through charge transfer from electron‐rich amines in the RuSiNPs to the electron‐deficient aromatic ring of TNT to form a red TNT–amine complex. The absorption spectrum of this complex overlaps with the ECL spectrum of the APTES‐modified RuSiNPs/triethylamine system. As a result, ECL signals of the APTES‐modified RuSiNPs/triethylamine system are turned off in the presence of TNT owing to resonance energy transfer from electrochemically excited RuSiNPs to the TNT–amine complex. This ECRET method has been successfully applied for the sensitive determination of TNT with a linear range from 1×10^?9 to 1×10^?6 M with a fast response time within 1 min. The limit of detection is 0.3 nM . The method exhibits good selectivity towards 2,4‐dinitrotoluene, p‐nitrotoluene, nitrobenzene, phenol, p‐quinone, 8‐hydroxyquinoline, p‐phenylenediamine, K₃[Fe(CN)₆], Fe³⁺, NO₃^?, NO₂^?, Cr³⁺, Fe²⁺, Pb²⁺, SO₃^2?, formaldehyde, oxalate, proline, and glycine.