Synthesis and Crystal Structure of a Novel Ion-pair Compound Consisting of 1-（4-Bromobenzyl）pyridinium Cation and 7,7,8,8-Tetracyanoquinodimethanide Anion

The title compound [BrBzPy][TCNQ] （BrBzPy^＋=1-（4-bromobenzyl）pyridinium cation, TCNQ = 7,7,8,8-tetracyanoquinodimethanide anion） was synthesized by the reaction of [BrBzPy]Br and LiTCNQ in ethanol solution and its structure was determined by single-crystal X-ray diffraction. The crystal belongs to monoclinic, space group P21/c with a = 14.067（3）, b = 7.3089（14）, c = 23.796（4）A, β = 122.011（9）°, V= 2074.6（7）A^3, Z = 4, C24H15BrN5, Mr = 453.32, Dc = 1.451 g/cm^3,μ = 2.002 mm^-1, S = 1.047, F（000） = 916, R = 0.0398 and wR = 0.0921. The most prominent structural features are the completely segregated stacking columns of the TCNQ- anions and [BrBzPy]^＋ cations. In a TCNQ column, the centroid-to-centroid distances of the neighboring anions of TCNQ are 3.2693 and 4.9464 A, respectively.     

Synthesis and Crystal Structure of a Lanthanum(III) Complex with Chelidamic Acid

A new lanthanum complex, (H3O)2[La(C7H3NO5)2(H2O)2]2·3(H2O) or (H3O)2[La(HChel)2(H2O)2]2·3(H2O) 1 (H3Chel = 4-hydroxypyridine-2,6-dicarboxylic(chelidamic) acid), has been prepared by the hydrothermal reaction, and its crystal structure was determined based on single-crystal diffraction data. Compound 1 crystallizes in triclinic, space group P with a = 9.6939(19), b = 10.176(2), c = 11.502(2) (A), α = 111.52(3), β = 93.74(3), γ = 103.33(3)°, V = 1013.0(3) (A)3, Dc = 1.912 g/cm3, Z = 1, Mr = 1166.40, μ = 2.188 mm-1, λ(MoKα) = 0.71073 (A) and F(000) = 574. The final R = 0.0342 and wR = 0.0737 for 4080 observed reflections with I > 2σ(I), and R = 0.0429 and wR = 0.0772 for all data. Compound 1 contains two lanthanum ions, four chelidamic acid ligands, four coordinated water molecules, two hydroniums, and three discrete water molecules. The LaIII atom is ten-coordinated by four oxygen and two nitrogen atoms from two tridentate chelating chelidamic acid ligands, two carboxylic oxygen atoms from an adjacent chelidamic acid ligand and two coordinated water molecules, leading to a distorted dodecahedral geometry. A three-dimensional network is formed by H-bonds.     

Mechanical deformation and multiple thermal restoration of organic crystals: reversible multi-stage shape-changing effect with luminescence-color changes

Shape-memory materials can be mechanically deformed and subsequently reverse the deformation upon changing the temperature. Shape-memory materials have attracted considerable attention for basic research and industrial applications, and polymer and alloy shape-memory materials have been well studied; however, it is formidably challenging to develop functional shape-memory materials, such as materials with multi-stage and anisotropic shape changes and shape changes accompanied by changes in color and light emission. Here, we found a reversible multi-stage shape-changing effect after mechanical deformation in a molecular crystal induced by multi-step thermal phase transitions with reversible shape changes and luminescence-color changes. Using single-crystal structure and thermal analyses as well as mechanical property measurements, we found that the reversible multi-stage shape-changing effect was achieved by a combination of a twinning deformation and multi-step thermal phase transitions. The changes in the crystal shape and luminescence suggest novel strategies for imparting known shape-memory materials with additional functionalities.

A reversible multi-stage shape-changing material based on an organic crystalline material is presented. Intriguingly, the interconversion among the three different shapes is accompanied by changes of the luminescence color.     

Surface-Enhanced Raman Scattering of Hydrogen Plasma-Treated Few-Layer MoTe_2

Two-dimensional surface-enhanced Raman scattering(SERS) substrates have drawn intense attention due to their excellent spectral reproducibility, high uniformity and perfect anti-interference ability. However, the inferior detection sensitivity and low enhancement have limited the practical application of two-dimensional SERS substrates. To address this issue, we propose that the interaction between the MoTe_2 substrate and the analyte rhodamine 6 G molecules could be remarkably enhanced by the introduced p-doping effect and lattice distortion of MoTe_2 via hydrogen plasma treatment. After the treatment, the SERS is greatly improved, the enhancement factor of probe molecules reaches 1.83 × 10~6 as well as the limit of detection concentration reaches 10-13 M.This method is anticipated to afford new enhancement probability for other 2D materials, even non-metal oxide semiconductor SERS substrates.     

超导磁体螺栓结合面低温振动特性研究

振动特性对于超导磁体的各类工程应用具有重要意义,螺栓法兰盘连接是超导磁体系统的一种常见的支撑结构类型,然而螺栓结合面在低温条件下振动特性的相关研究目前尚少见报道.本研究中设计加工了简化的连接结构,在室温和液氮温度对其螺栓结合面进行振动特性的测试分析.接下来,采用集中质量法进行建模,并利用振型、频率与质量矩阵、刚度矩阵的关系求解了不同螺栓预紧力情况下的刚度矩阵,得到了系统总刚度和结合面刚度.使用上述方法对振动测量数据计算发现,该结构的系统总刚度与结合面刚度都随着预紧力增大而增大,同时液氮低温条件可使系统总刚度和结合面刚度进一步增大.     

Editorial for special issue on lithium niobate based photonic devices

正Lithium niobate(Li Nb O_3), so-called "Silicon in Photonics," is a multifunctional crystal with a combination of a number of excellent physical properties. In optics and photonics, the Li Nb O_3-based devices, such as modulators, wavelength converters, waveguide amplifiers, and quantum photonic chips, have been realized and widely applied in various areas. In addition to the traditional waveguides,     

NiFe双金属催化剂用于月桂酸甲酯加氢的研究

负载型Ni Fe/γ-Al₂O₃双金属催化剂的物理化学性质明显受还原温度的影响,进而影响月桂酸甲酯的加氢活性和产物选择性。金属Ni活性中心主要促进脱羰/脱羧(DOC)反应,Fe的加入能促进月桂酸甲酯发生加氢脱氧反应,促进C₁₂烷烃化合物生成。H₂-TPR、XRD、H₂-TPD和BET结果表明,高的还原温度有利于金属或合金活性中心形成,NiFe双金属催化剂的加氢活性取决于金属Ni、Fe和NiFe合金的含量;NiFe双金属催化剂吸附与活化H₂分子的能力明显受还原温度的影响。在研究的温度范围内,Ni活性中心具有优异的加氢和裂解性能,Fe物种的引入能有效抑制裂解性能。双金属催化剂的加氢活性顺序:NF420>NF360>NF450>NF300,在420℃下经H₂还原制得的NF420催化剂具有最佳的月桂酸甲酯加氢性能,在反应温度为380℃时,月桂酸甲酯加氢转化率和烷烃化合物选择性分别高达93.3%和90.0%。     

聚吡咯纳米线凝胶的模板制备及储能与电化学传感性能

以配位聚合物凝胶为模板,构筑均一的聚吡咯纳米线网络,聚合后经简单处理除去模板,得到性能优异的聚吡咯凝胶.结果表明,模板法合成的聚吡咯凝胶为由均一纳米线组成的三维网络结构,具有良好的力学性能、较大的比表面积及优异的电化学特性,在0.28 A/g电流密度下,比电容可达450 F/g,在2.8 A/g电流密度下充放电1000次,比电容仍可保持88.6%.聚吡咯纳米线网络凝胶经葡萄糖氧化酶负载后得到柔性传感电极,对低浓度(0.2 mmol/L)的葡萄糖具有快速响应性能,有望用于超级电容器及生物电化学传感器等领域.     

可见光诱导的醇的选择性氧化

在蓝光照射的无金属、无添加剂的绿色温和条件下,以2-氯蒽醌为光催化剂,空气/氧气为氧化剂,高选择性地将芳族与杂芳族取代的伯醇和仲醇转化为相应的羰基化合物.实验结果表明,该催化剂具有较宽的底物适用范围,为苄基位含氧化合物的合成提供了一条经济、环保和可持续的新路径,具有潜在的应用前景.     

Au负载SBA-15分子筛上葡萄糖氧化反应

探讨了金与铝改性的SBA-15分子筛催化剂(Au-Al/SBA-15)上活性中心与葡萄糖氧化制葡萄酸反应性能的关系.通过固体核磁共振波谱(ss NMR)、X射线光电子能谱(XPS)、紫外-可见光谱(UV-Vis)和透射电子显微镜(TEM)等手段对不同Au及Al含量的Au-Al/SBA-15催化剂进行了结构表征.发现Al改性能够在SBA-15载体上产生四配位Al物种,Au主要以单质的形式存在; SBA-15上的四配位Al物种具有稳定Au颗粒大小的作用.通过对比发现,催化剂上的Au和骨架四配位Al物种间的相互协作促进了对葡萄糖氧化的活性,而非骨架Al物种会导致副反应的发生,降低葡萄糖酸产物的选择性.通过固体13C NMR揭示了反应体系中的NaOH能够将强吸附的产物葡萄糖酸分子从催化剂表面解离,保持活性位不被覆盖进而促进反应持续进行.