微波辅助-液液微提取环境水样中的三嗪类除草剂

采用微波辅助-液液微提取高效液相色谱法测定环境水样中的三嗪类除草剂.优化了提取溶剂的种类和体积、样品溶液的pH值、盐的浓度、提取时间、微波功率、振荡时间和离心速度等实验条件.在20 mL水样中,加入200 μL 1-己基-3-甲基咪唑六氟磷酸盐(提取剂),控制NaCl的含量为3%(m/V),在300 W时常压微波提取加热1 min,振荡15 min. 提取完成后,在冰水浴中冷却20 min后, 以8000 r/min离心5 min.在最佳实验条件下,5种除草剂在2.5～60 μg/L范围内线性良好,相关系数在0.9972～0.9991之间; 检出限为0.56～1.44 μg/L.     

一种两性三元共聚物的合成

选用聚乙二醇二丙烯酸酯(PEGDA)为扩链剂,以丙烯酰胺(AM)、2-甲基-2-丙烯酰胺基丙磺酸(AMPS)、甲基丙烯酰氧乙基三甲基氯化铵(DMC)为主单体,采用水溶液聚合方法合成了两性三元共聚物AM/AMPS/DMC;测定了共聚物的性能,并利用红外光谱研究了其分子结构.结果表明,所合成的共聚物具有良好的耐酸和高温稳定性,以及高抗剪切率.     

空壳纳米金修饰的新型DNA传感器

利用新型材料金纳米空球, 通过层层修饰的技术, 分别将壳聚糖、空壳纳米金、L-半胱氨酸、细胞色素c以及ssDNA探针修饰到玻碳电极表面, 制备了一种新型的DNA生物传感器. 以紫外及透射电子显微镜(TEM)表征了空壳纳米金, 以循环伏安法、阻抗谱图等电化学方法研究了传感器的特性, 通过原子力显微镜方法观察了该DNA生物传感器不同层之间的形态差异. 结果表明, 该修饰电极所吸附的ssDNA探针为1.672×10^―10 mol•cm^－2. 在指示剂柔红霉素的帮助下, DNA探针可与互补的DNA进行杂交, 借此以微分脉冲伏安法测定DNA.     

Theoretical study on the molecule C30H20: five carbon–carbon single bonds linking a dodecahedrane cage and a pentaprismane cage

Using geometry optimization and DFT method at the B3LYP/6-31G* level of theory for C₃₀H₂₀, an equilibrium geometry is identified that has the form of polyhedral hydrocarbon with five carbon–carbon single bonds linking a dodecahedrane cage and a pentaprismane cage. Thus, this molecule is a tri-cage molecule with two pentaprismane cages and one dodecahedrane cage. Vibrational frequencies and the infrared spectrum are computed at the same level of theory. The heat of formation for C₃₀H₂₀ has been estimated in this paper. The heat of formation of C₃₀H₂₀ as well as the vibrational analysis indicates that this molecule enjoys sufficient stability to allow for its experimental preparation.     

Crystal engineering of a versatile building block toward the design of novel inorganic-organic coordination architectures

Six novel inorganic-organic coordination supramolecular networks based on a versatile linking unit 4-pyridylthioacetate (pyta) and inorganic Co(II), Cu(II), Ag(I), Zn(II), Mn(II) and Pb(II) salts have been prepared in water medium and structurally characterized by single-crystal X-ray diffraction analysis. Reaction of CoCl(2).6H(2)O with Hpyta afforded a neutral mononuclear complex [Co(pyta)(2)(H(2)O)(4)](1), which exhibits a two-dimensional (2-D) layered architecture through intermolecular O-HO interactions. Reaction of CuCl(2.2H(2)O with Hpyta yielded a neutral one-dimensional (1-D) coordination polymer [[Cu(pyta)(2)(H(2)O].0.5H(2)O](n)(2) consisting of rectangle molecular square units, which show a three-dimensional (3-D) supramolecular network through S...S and O-H...O weak interactions. However, when AgNO(3), Zn(OAc)(2).2H(2)O or MnCl(2).4H(2)O salts were used in the above self-assembled processes, the neutral 2-D coordination polymers [Ag(pyta)](n)(3), [[Zn(pyta)(2)].4H(2)O](n)(4) or [[Mn(pyta)(2)(H(2)O)]](n)(5) with different topologies were obtained, respectively. While substituting the transition metal ions used in 1-5 with Pb(OAc)(2).3H(2)O, a one-dimensional coordination polymer [Pb(pyta)(2)](n)(6), which shows a novel 2-fold interpenetrating 2-D supramolecular architecture through weak SS interactions, was isolated. It is interesting to note that the building block pyta anion exhibits different configurations and coordination modes in the solid structures of complexes 1-6. These results indicate that the versatile nature of this flexible ligand, together with the coordination preferences of the metal centers, play a critical role in construction of these novel coordination polymers or supramolecules. The spectral and thermal properties of these new materials have also been investigated.     

Adsorption and diffusion on a stepped surface: atomic hydrogen on Pt(211)

We present density functional theory calculations for atomic hydrogen interacting with a stepped surface, the Pt(211) surface. The calculations have been performed at the generalized gradient approximation level, using a slab representation of the surface. This is the state-of-the-art method for calculating the interaction of atoms or molecules with metal surfaces, nevertheless only few studies have used it to study atoms or molecules interacting with stepped surfaces, and none, to the best of our knowledge, have considered hydrogen interacting with stepped platinum surfaces. Our goal has been to initiate a systematic study of this topic. We have calculated the full three-dimensional potential energy surface (PES) for the H/Pt(211) system together with the vibrational band structure and vibrational eigenfunctions of H. A deep global minimum of the PES is found for bridge-bonded hydrogen on the step edge, in agreement with experimental results for the similar H/Pt(533) system. All the local vibrational excitations at the global minimum have been identified, and this will serve as a helpful guide to the interpretation of future experiments on this (or similar) system(s). Furthermore, from the calculated PES and vibrational band structure, we identify a number of consequences for the interpretation or modelling of diffusion experiments studying the coverage and directional dependence of atomic hydrogen diffusion on stepped platinum surfaces.     

Rational Design of a Humanized Glucagon‐Like Peptide‐1 Receptor Agonist Antibody

Bovine antibody BLV1H12 possesses a unique “stalk–knob” architecture in its ultralong heavy chain CDR3, allowing substitutions of the “knob” domain with protein agonists to generate functional antibody chimeras. We have generated a humanized glucagon‐like peptide‐1 (GLP‐1) receptor agonist antibody by first introducing a coiled‐coil “stalk” into CDR3H of the antibody herceptin. Exendin‐4 (Ex‐4), a GLP‐1 receptor agonist, was then fused to the engineered stalk with flexible linkers, and a Factor Xa cleavage site was inserted immediately in front of Ex‐4 to allow release of the N‐terminus of the fused peptide. The resulting clipped herceptin–Ex‐4 fusion protein is more potent in vitro in activating GLP‐1 receptors than the Ex‐4 peptide. The clipped herceptin–Ex‐4 has an extended plasma half‐life of approximately four days and sustained control of blood glucose levels for more than a week in mice. This work provides a novel approach to the development of human or humanized agonist antibodies as therapeutics.     

A Facile and Universal Top‐Down Method for Preparation of Monodisperse Transition‐Metal Dichalcogenide Nanodots

Despite unique properties of layered transition‐metal dichalcogenide (TMD) nanosheets, there is still lack of a facile and general strategy for the preparation of TMD nanodots (NDs). Reported herein is the preparation of a series of TMD NDs, including TMD quantum dots (e.g. MoS₂, WS₂, ReS₂, TaS₂, MoSe₂ and WSe₂) and NbSe₂ NDs, from their bulk crystals by using a combination of grinding and sonication techniques. These NDs could be easily separated from the N‐methyl‐2‐pyrrolidone when post‐treated with n‐hexane and then chloroform. All the TMD NDs with sizes of less than 10 nm show a narrow size distribution with high dispersity in solution. As a proof‐of‐concept application, memory devices using TMD NDs, for example, MoSe₂, WS₂, or NbSe₂, mixed with polyvinylpyrrolidone as active layers, have been fabricated, which exhibit a nonvolatile write‐once‐read‐many behavior. These high‐quality TMD NDs should have various applications in optoelectronics, solar cells, catalysis, and biomedicine.     

The first montmorillonite‐supported surface single‐structure titanium complex: synthesis,characterization and catalytic activity in alkene epoxidation

A well‐defined single‐site titanium‐modified montmorillonite (MMT) with only one geometric construction ((?SiO)₃–Ti–NMe₂) was obtained in moderate conditions. Reaction of tetrakis(dimethylamido)titanium with hydroxylated MMT was conducted by surface organometallic chemistry technique, and the surface structure was characterized by in situ Fourier transform infrared spectroscopy, ¹³C cross polarization magic angle spinning nuclear magnetic resonance, X‐ray photoelectron spectroscopy, extended X‐ray absorption fine structure, and elemental analysis. The catalytic activity in alkene epoxidation was evaluated, and the results revealed that the steric hindrance of the substances is responsible for the catalytic activity of the MMT‐supported titanium complex but to the characteristic restricted layer‐like structure of the MMT. Copyright © 2014 John Wiley & Sons, Ltd.     

The Syntheses,Structures, and Magnetic Properties of Four 2D Lanthanide(III)‐naphthalenedicarboxylic Complexes

Four Ln‐NDC coordination polymers [Ln(NDC)(HNDC)(H₂O)] (Ln = La ( 1 ), Pr ( 2 ), Nd ( 3 ), Sm ( 4 ), H₂NDC = 1,4‐naphthalenedicarboxylic acid) were hydrothermally synthesized and structurally characterized by elemental analyses, IR spectroscopy, and single‐crystal X‐ray diffraction. Compounds 1 – 4 are isomorphous, and their structures display a layer constructed from a Ln‐organic chain and NDC^2– ligand, in which the H₂NDC ligands adopt two different acidity‐dependent types and coordination modes: HNDC^1– with μ‐η¹:η¹ and NDC^2– with μ‐η¹:η²:η¹:η². The 3D supramolecular networks of 1 – 4 are mainly controlled by hydrogen bonds interactions. The magnetic susceptibilities of complexes 2 – 4 reveal overall antiferromagnetic interactions between the Ln^III ions. In addition, thermogravimetric analysis of compound 2 is described.