One-dimensional coordination polymers generated from an oxadiazole-containing N,N′-bipyridine-type ligand and inorganic salts

Three new one-dimensional coordination polymers have been prepared using Hg(II), Ag(I) and Zn(II) inorganic salts in combination with 2,5-bis(3-pyridyl)-1,3,4-oxadiazole (L6). The compounds were characterized by single crystal X-ray diffraction, IR spectroscopy, and elemental analysis. In the solid state, compounds 1 and 3 (1: monoclinic, P2₁/n, a=5.5373(3) Å, b=16.7839(9) Å, c=16.8120(9) Å, β=92.8610(10)°, V=1560.52(15) ų, Z=4; 3: monoclinic, P2₁/n, a=7.2958(4) Å, b=11.7214(6) Å, c=16.3979(9) Å, β=101.1150(10)°, V=1375.99(13) Å³, Z=4) feature novel one-dimensional helical chain motif. Compound 2, however, (2: monoclinic, P2₁/c, a=5.5506(4) Å, b=16.5895(12) Å, c=16.6871(11) Å, β=95.424(2)°, V=1529.70(19) ų, Z=4) exhibits one-dimensional zigzag chain motif, which result from the different conformations adopted by the L6 ligand and also the different metal coordination geometry. The luminescent properties of three new compounds were investigated in the solid state.     

部分和乘积的几乎处处中心极限定理

设X_n, n≥1是独立同分布正的随机变量序列, E(X₁)=u >0, Var(X₁)=σ², E|X₁|³<∞, 记S_n==∑^N_k=1X_k, 变异系数γ=σ/u.g是满足一定条件的无界可测函数, 证明了 lim_N→∞1/logN∑^N_n=11/n g((∏ⁿ_k=1S_k/n!uⁿ )^1/γ√n )=∫^∞₀g(x)dF(x),a.s., 其中 F(•) 是随机变量e^√2ξ 的分布函数, ξ 是服从标准正态分布的随机变量.     

Dielectrophoretic motions of a pair of particles in the vicinity of a planar wall under a direct-current electric field

This paper presents direct simulations on the two-dimensional dielectrophoretic (DEP) motion of a pair of particles in a viscous fluid, interacting with a nearby planar wall, to further understand the DEP interaction among multiple particles and a wall. Results show that, under an external direct-current electric field parallel to the wall-fluid interface, the nearby wall has significant effects on the DEP motion of both particles including their revolution, alignment and aligned movement. Regardless of their particle conductivity, the wall being less (more) conductive than the fluid pushes (draws) both particles to move away from (toward) it.     

Synthesis and characterization of nano-peanuts of lead(II) coordination polymer [Pb(qcnh)(NO3)2]n with ultrasonic assistance: A new precursor for the preparation of pure-phase nano-sized PbO

A sonochemical method was used to synthesize nano-peanuts of a new lead(II) coordination 1D polymer, [Pb(qcnh)(NO₃)₂]_n (1), where qcnh = 2-quinolincarbaldehyde nicotinohydrazide. The compound was characterized by scanning electron microscopy (SEM), elemental analysis, IR spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray powder diffraction (XRD), and single crystal X-ray analysis. The X-ray structure revealed that the Pb(II) atom is coordinated by one oxygen and three nitrogen atoms from two qcnh ligands and five oxygen atoms from three nitrate ligands in an 8 + 1 fashion with a PbN₃O₆ donor set. One of the PdN distances in the vicinity of the central atom is a bit longer (Pb1N1 = 2.939(4) Å), which shows the effect of the 6s² lone electron pair localized within the valence shell of the lead(II) atom. PbO nanoparticles were obtained by thermolysis of 1 at 180 °C with oleic acid as a surfactant. The average diameter of the nanoparticles was estimated by XRD to be 28 nm. The morphology and size of the prepared PbO nanoparticles were further studied using SEM.     

基于5-羟甲基-1.3-苯二酸的两个四连接锌配合物的合成、结构和性质

在辅助配体4,4′-二(1H-咪唑-1-基)-1,1′-双苯（4,4′-DIB）的帮助下,5-羟甲基-1.3-苯二甲酸(H₂HIA)与Zn(BF₄)₂通过溶剂热或者水热反应构建出了两个具有sql网络的三维超分子配合物,即{[Zn₂(HIA)₂(4,4′-DIB)₂]·xGuest}_n (1, CCDC: 1989855 )和[Zn₂(HIA)₂(4,4′-DIB)₂]_n(2, CCDC: 1989856)。并对配合物的PXRD, IR, TGA和荧光等特性进行了表征。     

Upper bounds for signless Laplacian Z-spectral radius of uniform hypergraphs

Let ■ be a k-uniform hypergraph on n vertices with degree sequence △= d1≥…≥ dn =δ. In this paper, in terms of degree di , we give some upper bounds for the Z-spectral radius of the signless Laplacian tensor (Q(■)) of ■. Some examples are given to show the efficiency of these bounds.     

Thickness-dependent of conduction mechanism and bias electric field modulation of transport properties for SrRuO3/PMN-PT heterostructures

Ultra-thin SrRuO₃ (SRO) films have been grown on ferroelectric and piezoelectric PMN-PT substrates. The structural properties of these films have been characterized by atomic force microscopy, x-ray diffraction and cross-sectional transmission electron microscopy. The nature of electric transport was analyzed in detail and the conduction mechanism of SRO films evolves through three regimes: from a three-dimensional (3D) metallic through a weakly localized to a strongly localized behavior as film thickness is reduced. The bias electric field modulations of transport properties and magnetic properties were explored for these films. We also demonstrate that ferroelectric (FE) domain switching induces a reversible tuning of the magnetic and electric properties in SRO/PMN-PT heterostructure. The FE domain switching in the substrate contributes to an in-plane strain that changes the spin exchange coupling in the SRO layer, and therefore results in a reversible resistance difference of up to 16%. This modulation effect on the electric properties by an electric field demonstrates great potential for the applications of all-oxides spintronics devices.     

Sc修饰Si@Al_(12)团簇吸附CO的第一性原理研究

本文采用密度泛函理论的广义梯度近似,研究了Sc原子修饰的Si@Al_(12)团簇与CO分子之间的相互作用.结果显示:Sc原子倾向于以穴位的形式吸附于Si@Al_(12)团簇表面;Sc周围最多可以吸附7个完整CO分子,CO的平均吸附能处于0.990~1.602 eV之间;Sc Si@Al_(12)·7CO团簇中CO质量分数可达33.07%,有望作为CO气体过滤材料.     

Synthesis,Crystal and Electronic Structure,and Optical Property of the Quaternary Selenide: La3Sb0.33SiSe7

The quaternary selenide, La₃Sb_0.33SiSe₇, was prepared from stoichiometric mixtures of elements by solid‐state reactions at 1223 K in an evacuated silica tube. La₃Sb_0.33SiSe₇ crystallizes in the chiral P6₃ space group and belongs to the Ce₃Al_1.67S₇ structure type. Its structure features one‐dimensional chains of face‐sharing SbSe₆ octahedra running parallel to the c direction surrounded by the discrete SiSe₄ tetrahedra and La cations. UV/Vis/NIR diffuse reflectance spectroscopy study shows its optical gap of around 1.75 eV. DFT study indicates an indirect bandgap with an electronic transfer excitation from Se 4p to La 5d orbital electrons.     

Synthesis,Crystal Structure,and Optical Property of the Quaternary Semiconductor La4Cd4In2S13

The sulfide La₄Cd₄In₂S₁₃ in the quaternary RE/M/N/Q (RE = rare‐earth metal; M = Zn, Cd; N = Ga, In; Q = chalcogenides) system was prepared from stoichiometric mixtures of the elements by solid‐state reactions at 1223 K in an evacuated silica tube. The La₄Cd₄In₂S₁₃, crystallizing in the Pbam space group, is isostructural with Pb₄Bi₄In₂S₁₃. The structure of La₄Cd₄In₂S₁₃ consists of double chains of CdS₆ octahedra extending along [001] direction that are interconnected by single chains of InS₆ octahedra by edge‐sharing into 1D ribbons. These ribbons are further fused by the infinite one‐dimensional chains of InS₄ tetrahedra by corner‐sharing into Z‐shaped [Cd₄In₂S₁₃]^12– layers perpendicular to the b direction separated by the La³⁺ ions. UV/Vis/NIR diffuse reflectance spectroscopy study shows its optical gap of around 2.27 eV.