Dimolybdenum Complexes Containing Pairs of Bridging Diphosphine and Carboxylate Ligands. Synthesis and Structures of trans-Mo2(O2CCH3)2(μ-dppa)2(BF4)2 and trans-Mo2X2(O2C(CH2)nCH3)2(μ-dppa)2 (n = 2, 10 or 12; X = Cl or Br; dppa = N,N-Bis(diphenylphosphino)amine)

The red complex trans-Mo₂(O₂CCH₃)₂(μ-dppa)₂(BF₄)₂, 1 , was prepared by reaction of [Mo₂(O₂CCH₃)₂(CH₃CN)₆][BF₄]₂ with dppa (dppa = Ph₂PN(H)PPh₂) in THF. The reactions of Mo₂(O₂C(CH₂)_nCH₃)₄ with dppa and (CH₃)₃SiX (X = Cl or Br) afforded the complexes trans-Mo₂X₂(O₂C(CH₂)_nCH₃)₂(μ-dppa)₂ (X = Cl, n = 2, 2; X = Br, n = 2, 3; X = Cl, n = 10, 4 ; X = Cl, n = 12, 5 ). Their UV-vis, IR and ³¹P{¹H}-NMR spectra have been recorded and the structures of 1, 2 and 3 have been determined. Crystal data for 1 : space group P2₁/n, a = 12.243(1) Å, b = 17.222(1) Å, c = 13.266(1) Å, β = 95.529(1)°, V = 2784.1(6) ų, Z = 2, with final residuals R = 0.0509 and Rw = 0.0582. Crystal data for 24CH₃Cl₂: space group P2₁/n, a = 13.438(1) Å, b = 19.276(1) Å, c = 14.182(1) Å, β = 111.464(1)°, V = 3418.9(6) ų, Z = 2, with final residuals R = 0.0492 and Rw = 0.0695. Crystal data for 3·4CH₂Cl₂: space group P2₁/n, a= 13.579(1) Å, b = 19.425(1) Å, c = 14.199(1) Å, β = 111.881(2)°, V = 3475.6(7) ų, Z = 2, with final residuals R = 0.0703 and Rw = 0.0851. Comparison of the structural data shows that the effect of the axial ligand on weakening the Mo-Mo bond strength is X^? > CH₃CN > BF₄^?. The T_m values are 121.7 °C for 2 , 111.1 °C for 3 and 91.5 °C for 5 , respectively.     

An electrospun hygroscopic and electron-conductive core-shell silica@carbon nanofiber for microporous layer in proton-exchange membrane fuel cell

Journal of Solid State Electrochemistry - In this study, a novel core-shell silica@carbon nanofiber (SiO2@C) is successfully prepared via coaxial electrospinning technique with optimized parameters...     

温控/光控片上纳米裂结

由于分子尺寸小、可化学合成、与生物组织兼容等显著优点，以有机小分子为核心的单分子器件引起了人们的广泛关注，单分子器件有望成为硅基电子器件的一个重要的互补发展方向。已报道构筑单分子电子回路的大部分方法程序繁琐，且无法在平面基底上实时调控电极间的间距。这项工作采用机械切割结合电化学腐蚀的方法来制作纳米电极，通过控制施加在阴极和阳极之间的电压，并实时监测通过被腐蚀的金线的电流的大小，可以获得针尖状与分子大小匹配的纳米电极。进一步利用热胀冷缩的原理，采用比金的热膨胀系数小很多的材料作为基底，实现了环境温度对电极间距离的调控，即通过改变环境温度实现了可重复操作的电极间的连接及断开。在此温控基础之上，进一步实现了利用光强更为地精密调控电极间的距离，调控的精度可以达到原子级别。实验结果表明，我们制作的温控/光控片上纳米电极无需借助高精尖仪器，就可以实现对电极之间的距离的精密控制，其平面基底构型，为单分子电子器件的研究提供了有助于片上器件集成的新方法。     

Synthesis of novel hierarchical porous polymers with a nanowire-interconnected network structure from core-shell polymer nanoobjects

Design and fabrication of the micro/nanostructures of the network units is a critical issue for porous nanonetwork structured materials. Significant progress has been attained in construction of the network units with zero-dimensional spherical shapes. However, owing to the limitations of synthetic methods, construction of porous building blocks in one dimension featuring high aspect ratios for porous nanonetwork structured polymer (PNSP) remains largely unexplored. Here we present the successful design and preparation of PNSP with a novel type of one-dimensional network unit, i.e., microporous heterogeneous nanowire. Well-defined core-shell polymer nanoobjects prepared from a gelable block copolymer, poly(3-(triethoxysilyl)propyl methacrylate)-block-polystyrene are employed as building blocks, and facilely transformed into PNSP via hypercrosslinking of polystyrene shell. The as-prepared PNSP exhibits unique three-dimensional hierarchical nanonetwork morphologies with large surface area. These findings could provide a new avenue for fabrication of unique well-defined PNSP, and thus generate valuable breakthroughs in many applications.     

Indoor localization algorithm using clustering on signal and coordination pattern

In recent years, the demand for indoor location-based services has gradually received greater attention. The presence of multipath interference has a tendency to interfere with traditional algorithms calculated based on received signal strength (RSS). The application of virtual tags can greatly reduce deployment costs and enable greater environmental adaptability. However, an excess of ineffectively filtered virtual tags will only lead to greater error in calculation. Therefore, virtual tags are combined with a two-step clustering method to replace the concept of signal hotpoint intersections due to the mutual interdependence of data in space and the influence of neighboring objects. This study improved a two-step location algorithm that combines the advantages of virtual tags and two-step clustering analysis, called clustering-based localization algorithm, offering significant improvement over most traditional localization algorithms. RSS are no longer used as a basis for clustering, and are replaced by the combination of signal and coordination pattern. Two steps of cluster analysis are performed during the filtering process. The first step utilizes the tags’ signals to perform clustering. The second step incorporates tags’ coordinate for filtering. As the clustering-based localization process considers the interactive relationship between coordinate data, it achieves superior results compared to those produced via methods that only use signal strength to select neighboring solutions. This study then constructs a wireless sensor network and assesses the effectiveness of the algorithm.     

A New Zn(Ⅱ) Coordination Polymer Constructed by 1,4-Benzenedithiolate Dianion: [Zn(SC_6H_4S)(1,3-DPA)]_n

A new one-dimensional polymer, [Zn(SC6H4S)(1,3-DPA)]n(1, SC6H4 S = 1,4-benzenedithiolate and 1,3-DPA = 1,3-diaminepropane), has been synthesized and characterized by elemental analysis, PXRD, IR spectra, and single-crystal X-ray diffraction. The complex crystallizes in triclinic system, space group P1, with a = 6.7119(1), b = 9.0230(2), c = 10.4943(2) ?, α = 69.288(1), β = 75.848(1), γ = 81.513(1)o, V = 575.123(19) ?3, Dc = 1.615 g/cm3, Z = 2, F(000) = 288; the final S = 1.070, R = 0.0234, and w R = 0.0551. The compound consists of an infinite zigzag chain formed by [Zn(1,3-DPA)]2+ units joined by SC6H4 S ligands. Each chain interacts with neighboring chains via weak N–H···S hydrogen bonds to form an extended three-dimensional(3D) supramolecular network. The thermal and photoluminescent properties of 1 have also been investigated.     

Solvent Effects on the 1H-NMR Chemical Shifts of Imidazolium-Based Ionic Liquids

The ¹H nuclear magnetic resonance (¹H-NMR) spectrum is a useful tool for characterizing the hydrogen bonding (H-bonding) interactions in ionic liquids (ILs). As the main hydrogen bond (H-bond) donor of imidazolium-based ILs, the chemical shift (δ_H2) of the proton in the 2-position of the imidazolium ring (H2) exhibits significant and complex solvents, concentrations and anions dependence. In the present work, based on the dielectric constants (ϵ) and Kamlet-Taft (KT) parameters of solvents, we identified that the δ_H2 are dominated by the solvents polarity and the competitive H-bonding interactions between cations and anions or solvents. Besides, the solvents effects on δ_H2 are understood by the structure of ILs in solvents: 1) In diluted solutions of inoizable solvents, ILs exist as free ions and the cations will form H-bond with solvents, resulting in δ_H2 being independent with anions but positively correlated with β_S. 2) In diluted solutions of non-ionzable solvents, ILs exist as contact ion-pairs (CIPs) and H2 will form H-bond with anions. Since non-ionizable solvents hardly influence the H-bonding interactions between H2 and anions, the δ_H2 are not related to β_S but positively correlated with β_IL.     

一种镉基金属有机骨架材料对丙酮和Fe3+的荧光检测

以 1，3，5-三(4-羧基苯基)苯(H₃BTB)为配体，通过溶剂热法得到一种三维四重穿插结构的镉基金属有机骨架材料：(Me₂NH₂)[Cd(BTB)(DMF)]·DMF·H₂O(Cd-MOF)。通过单晶X射线衍射、粉末X射线衍射、红外分析、元素分析和热重分析表征了其组成和结构。荧光研究结果表明：Cd-MOF在含有丙酮或 Fe³⁺离子的溶液中均表现出荧光猝灭现象，其检测限(体积分数和浓度)分别为0.6%和0.89 μmol·L^-1，线性检测范围分别为2.0%~2.8%和0~0.05 mmol·L^-1。时间响应实验和可循环利用实验显示Cd-MOF可长时间、稳定且高效地检测丙酮和Fe³⁺离子。     

液相色谱串联质谱法同时测定饲料中8种苯并咪唑类药物

建立了同时测定饲料中8种苯并咪唑类药物(噻苯咪唑、丙硫咪唑、硫苯咪唑、苯硫氧咪唑、氟苯咪唑、甲苯咪唑、丙氧苯唑和三氯苯唑)的液相色谱串联质谱分析方法。饲料样品用酸化乙腈直接提取,提取液用甲酸溶液稀释后进行分析。分析时用XBridgeTMC18色谱柱,以甲酸溶液-乙腈体系进行梯度洗脱,MRM方式测定,基质外标法定量。8种苯并咪唑类药物均在0.02~10.0 mg.L-1范围内呈良好的线性关系,相关系数(r2)均不低于0.990,在饲料样品中的检出限为2.1~63.0μg.kg-1。饲料中苯并咪唑类药物在0.50、30、200 mg.kg-13种加标水平下的回收率为84%~104%,相对标准偏差均小于10.0%。方法分析单个样品约需30 min,该方法适合饲料中8种苯并咪唑类药物的同时分析。     

高效液相色谱法测定猪尿中克伦特罗对映异构体残留量

建立了测定猪尿中克伦特罗对映异构体残留量的高效液相色谱分析方法.在碱化的条件下,用乙酸乙酯提取10 mL猪尿样品,提取液经稀HCl反萃取,萃取液直接过SCX固相萃取小柱,再用5%氨化甲醇洗脱,洗脱液经氮气吹干后用200 μL甲醇定容.采用Astec CHIROBIOTICTM V手性色谱柱,以V(甲醇)∶ V(冰乙酸)∶ V(三乙胺)=99.94∶ 0.02∶ 0.04为流动相进行HPLC分析,检测波长301 nm,外标法定量.克伦特罗单-对映体的峰面积与其浓度在70～5000 μg/L范围内呈良好的线性; 线性相关系数均大于0.9996; 猪尿样品中检出限为0.30 μg/L.猪尿中克伦特罗对映体在1.0～20.0 μg/L范围内的添加回收率为76.3%～91.5%; 相对标准偏差RSD均小于7%(n=5).