A Family of 12‐Azametallacrown‐4 Structural Motif with Heterometallic MnIII‐Ln‐MnIII‐Ln (Ln=Dy,Er, Yb,Tb, Y) Alternate Arrangement and Single‐Molecule Magnet Behavior

Mixed 3d–4f 12‐azametallacrown‐4 complexes, [Mn₂Ln₂(OH)₂(hppt)₄(OAc)₂(DMF)₂] ? 2 DMF ? H₂O [Ln=Dy ( 1 ), Er ( 2 ), Yb ( 3 ), Tb ( 4 ) and Y ( 5 ), H₂hppt=3‐(2‐hydroxyphenyl)‐5‐(pyrazin‐2‐yl)‐1,2,4‐triazole)], were synthesized by reactions of H₂hppt with Mn(OAc)₂ ? 4 H₂O and Ln(NO₃)₃ ? 6 H₂O. This is the first 3d–4f azametallacrown family to incorporate Ln ions into the ring sets. These isostructural complexes exhibit alternating arrangements of two Mn and two Ln ions in the rings with each pair of metal centers bound by an N?N group and μ₂‐O bridging. Magnetic measurements revealed dominant antiferromagnetic interactions between metal centers, and frequency‐dependent out‐of‐phase (${\chi {^\prime}{^\prime}_{\rm{M}} }$ ) signals below 4 K suggest slow relaxation of magnetization.     

Synthesis of Mesoporous TiO2/SiO2 Hybrid Films as an Efficient Photocatalyst by Polymeric Micelle Assembly

Thermally stable mesoporous TiO₂/SiO₂ hybrid films with pore size of 50 nm have been synthesized by adopting the polymeric micelle‐assembly method. A triblock copolymer, poly(styrene‐b‐2‐vinyl pyridine‐b‐ethylene oxide), which serves as a template for the mesopores, was utilized to form polymeric micelles. The effective interaction of titanium tetraisopropoxide (TTIP) and tetraethyl orthosilicate (TEOS) with the polymeric micelles enabled us to fabricate stable mesoporous films. By changing the molar ratio of TEOS and TTIP, several mesoporous TiO₂/SiO₂ hybrid films with different compositions can be synthesized. The presence of amorphous SiO₂ phase effectively retards the growth of anatase TiO₂ crystal in the pore walls and retains the original mesoporous structure, even at higher temperature (650 °C). These TiO₂/SiO₂ hybrid films are of very high quality, without any cracks or voids. The addition of SiO₂ phase to mesoporous TiO₂ films not only adsorbs more organic dyes, but also significantly enhances the photocatalytic activity compared to mesoporous pure TiO₂ film without SiO₂ phase.     

Structure of Reconstructed Cu(100) Surface Induced by Dissociative Adsorption of Gaseous Oxygen

The reconstructed structures of Cu(100) surface induced by O₂ dissociative adsorption wereinvestigated by low energy electron diffraction and scanning tunneling microscopy. At lower oxygen coverage, it was found that two reconstructed structures, i.e. c(2×2)-O and (√2×2√2)R45°-O are coexistent. The domain size of the c(2×2)-O structure decreased with the increasing of O₂ exposure. The reconstructed structure at very small coverage was also investigated and a “zigzag” structure was observed at this stage. The “zigzag” structure was identified as boundaries of local c(2×2) domains. It was found that the strip region shows much stronger molecule-substrate interaction than that of oxygen covered regions, making it a proper template for patterned organic films. The sequence of the thermal stability was found as zigzag structure>c(2×2)>(√2×2√2)R45°-O.     

3D Luminescent Copper(I) Iodide Coordination Polymer Based on Cu4I4 Clusters and an Ethyl‐bridging Bis(triazole) Ligand

The copper‐iodine based coordination polymer [Cu₄I₂(bmte)]_n ( 1 ) [H₂bmte = 1,2‐bis(5‐methyl‐1H‐1,2,4‐triazol‐3‐yl)ethane] was synthesized using cuprous iodide and a flexible 3‐substituted, ethyl‐bridging bis(triazole) ligand under solvothermal conditions. X‐ray diffraction analysis reveals that compound 1 shows a 3D framework containing Cu₄I₄ clusters and alternating left‐ and right‐handed [Cu(triazole)] helices, which result in a (4,8)‐connected fluorite (flu) topological network. Moreover, compound 1 exhibits orange phosphorescence with the emission maxima at 590 nm in the solid state at room temperature.     

Controlling structural topology of metal-organic frameworks with a desymmetric 4-connected ligand through the design of metal-containing nodes

Two new metal-organic frameworks(MOFs),[Cu2(H_2O)_2(BCPIA)](BUT-20)and(Me_2NH_2)[In(BCPIA)](BUT-21)were designed and synthesized through the solvothermal reaction between a newly created desymmetric 4-connected ligand,5-(2,6-bis(4-carboxyphenyl)pyridin-4-yl)isophthalic acid(H_4BCPIA)and Cu(NO_3)2 2.5H_2O or In(NO_3)_3·5H_2O,respectively,and characterized by single-crystal and powder Xray diffraction,thermogravimetric analysis,infrared spectroscopy,and elemental analysis.The two MOFs have three-dimensional structures,in which both the BCPIA 4 ligand and metal-containing entities,Cu_2(COO)_4(H_2O)_2 and In(COO)_4 act as 4-connected nodes.However,different linkage configurations of the two metal-containing nodes,quadrilateral Cu_2_TD_2(COO)_4(H_2O)_2and tetrahedral In(COO)_4,lead to distinct structural networks of BUT-20 and 21,with Nbo and Unc topologies,respectively.     

Generation of Bessel Beams at mm- and Sub mm-wavelengths by Binary Optical Elements

In this paper, binary optical elements (BOE’s) are designed for generating Bessel beams at mm- and sub mm- wavelengths. The design tool is to combine a genetic algorithm (GA) for global optimization with a two-dimension finite-difference time-domain (2-D FDTD) method for rigorous electromagnetic computation. The design process for converting a normally incident Gaussian beam into a Bessel beam is described in detail. Numerical results demonstrate that the designed BOE’s can not only successfully produce arbitrary order Bessel beams, but also have higher diffraction efficiencies when compared with amplitude holograms.     

白光荧光粉Ca9.95-xNa0.75K0.25(PO4)7:Eu2+0.05,Mn2x+的制备及其发光特性

高温固相法合成了Ca9.95-xNa0.75 K0.25 (PO4)7∶Eu0.052+,Mn2+x(x=0,0.1,0.2,0.3,0.4,0.5,0.6和0.7)荧光粉,研究了其相组成和荧光发射性能.结果表明,由于样品中存在着晶体结构相似的双相,使得Eu2+的5d-4f跃迁辐射出峰值分别位于491和540 nm宽谱...     

SnS2 Nanoplatelet@Graphene Nanocomposites as High‐Capacity Anode Materials for Sodium‐Ion Batteries

Na‐ion batteries have been attracting intensive investigations as a possible alternative to Li‐ion batteries. Herein, we report the synthesis of SnS₂ nanoplatelet@graphene nanocomposites by using a morphology‐controlled hydrothermal method. The as‐prepared SnS₂/graphene nanocomposites present a unique two‐dimensional platelet‐on‐sheet nanoarchitecture, which has been identified by scanning and transmission electron microscopy. When applied as the anode material for Na‐ion batteries, the SnS₂/graphene nanosheets achieved a high reversible specific sodium‐ion storage capacity of 725 mA h g^?1, stable cyclability, and an enhanced high‐rate capability. The improved electrochemical performance for reversible sodium‐ion storage could be ascribed to the synergistic effects of the SnS₂ nanoplatelet/graphene nanosheets as an integrated hybrid nanoarchitecture, in which the graphene nanosheets provide electronic conductivity and cushion for the active SnS₂ nanoplatelets during Na‐ion insertion and extraction processes.     

基于遗传算法的LNG气化混合工质配比研究

混合工质合适的配比可以使其放热曲线与LNG气化曲线更好的匹配,减少冷能损失,从而提高循环效率.初选R23和R170为第一级循环的混合工质,R290、R143a、R1270和R125为第二级循环的混合工质.利用Hysys建立了利用LNG冷能发电的两级低温朗肯循环系统.以系统净输出功为目标函数,利用Design Exper...     

基于高双折射光纤布拉格光栅的自动增益控制掺铒光纤放大器

掺铒光纤非均匀展宽引起的空间烧孔现象导致单波长激光并不能完全控制放大器增益,提出了一种新颖的自动增益控制掺铒光纤放大器的结构:即采用高双折射光纤布拉格光栅产生抽运光,其写制光栅的波峰对应的波长分别为1549.3 nm和1549.83 nm,波长间隔为0.53 nm。通过调整偏振控制器,就实现了单激光或双激光的增益控制。这种设计增益控制范围为40 nm(1530~1570 nm),当输入功率在-40~-15 dBm的动态范围内,双激光增益控制的掺铒光纤放大器的平均增益和噪声系数分别约为22.22 dB和8.69 dB,而它们的漂移分别被钳制在0.69 dB和1.51 dB。系统性能测试表明:双激光控制掺饵光纤放大器在稳定性方面比单激光有着明显的优势。