Analytical chemistry of the persistent organic pollutants identified in the Stockholm Convention: A review

Persistent organic pollutants (POPs) are major environmental concern due to their persistence, long-range transportability, bio-accumulation and potentially adverse effects on living organisms. Analytical chemistry plays an essential role in the measurement of POPs and provides important information on their distribution and environmental transformations. Much effort has been devoted during the last two decades to the development of faster, safer, more reliable and more sensitive analytical techniques for these pollutants. Since the Stockholm Convention (SC) on POPs was adopted 12 years ago, analytical methods have been extensively developed. This review article introduces recent analytical techniques and applications for the determination of POPs in environmental and biota samples, and summarizes the extraction, separation and instrumental analyses of the halogenated POPs. Also, this review covers important aspects for the analyses of SC POPs (e.g. lipid determination and quality assurance/quality control (QA/QC)), and finally discusses future trends for improving the POPs analyses and for potential new POPs.     

Highly Selective and Sensitive Detection of Dopamine in the Presence of Excessive Ascorbic Acid Using Electrodes Modified with C60‐Functionalized Multiwalled Carbon Nanotube Films

Electrochemical detection of dopamine (DA) in the presence of a large excess of ascorbic acid (AA) was investigated with a novel all‐carbon nanocomposite film of C₆₀‐MWCNTs (C₆₀‐functionalized multi‐walled carbon nanotubes) using a bare MWCNTs film as control. Although both films can selectively detect DA from AA by separating their oxidation potentials, the C₆₀‐MWCNTs film shows special selectivity and good sensitivity for detecting DA. On one hand, the C₆₀‐MWCNTs composite film shows a higher activity for DA oxidation with enhanced peak current. On the other hand, the C₆₀‐MWCNTs composite film effectively suppresses the oxidation of AA. Remarkably, it is found that the oxidation current of DA is over 2 times higher than that of AA even when the concentration of AA is about 3 to 4 orders of magnitude higher than that of DA. This offers a tremendous advantage for the simple and clean detection of DA free of the interfering AA signal in a real assay. Cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectrometry are used to characterize the C₆₀‐MWCNTs composite film. These novel properties are interpreted to arise from the facile electron transfer between C₆₀ and MWCNTs in the C₆₀‐MWCNTs nanocomposite film.     

Density functional theory study of the free and tetraprotonated spheroidal macrotricyclic ligands and the complexes with halide anions: F−, Cl−, Br−

Theoretical studies of the macrotricyclic tetramine hexaether (SC), its tetraprotonated form SC‐4H⁺, and the corresponding complexes X^??SC‐4H⁺ (This expression represents the structural properties of the halide inclusion complex formed though the free ligand SC‐4H⁺ and the halide anion X^?: the spherical halide anion X^? is held by a tetrahedral array of ⁺N? H ··· X^? hydrogen bonds inside the intramolecular cavity of the tetraprotonated form SC‐4H⁺) of SC‐4H⁺ with the halide anions: F^?, Cl^?, and Br^? have been performed using density functional theory (DFT) with B3LYP/6‐31G method implemented in the Gaussian 03 program package. The optimized geometric structures obtained from DFT calculations are used to perform Natural Bond Orbital (NBO) analysis. The three main types of hydrogen bonds ⁺N? H ··· F^?, ⁺N? H ··· Cl^?, and ⁺N? H ··· Br^? are investigated. The results indicate that hydrogen bonding interactions are dominant and the halide anions: F^?, Cl^?, and Br^? offer lone pair electrons to the contacting σ* (N? H) antibond orbital of SC‐4H⁺. For all the structures, the most pronounced changes in geometric parameters upon interaction are observed in the proton‐donor molecule. The intermolecular interaction energies are predicted by using B3LYP/6‐31G methods with basis set superposition error (BSSE) and zero‐point energy (ZPE) correction. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

基于100 m色散位移光纤的超连续谱实验研究

利用被动锁模掺铒光纤激光器输出的重复频率13.9 MHz、中心波长1557.28 nm的光脉冲作泵浦源,在100 m的色散位移光纤中产生总宽度达488 nm的超连续谱,不平坦度小于±3.0 dB,利用法布里-珀罗滤波器获得163路多波长脉冲,利用可调谐滤波器得到C波段内脉宽为1.2～2.0 ps的近变换限超短光脉冲.分析了泵浦脉冲的功率、光纤长度等因素对SC光谱展宽的作用,并与色散平坦光纤和较长的色散位移光纤作了比较.     

EAST超导托克马克磁体的大型供电供冷外馈线

EAST全超导托克马克聚变实验装置由16个D形环向场线圈和12个圆形极向场线圈组成,大半径1.7m,当环形场线圈励磁14.3kA时,中心场3.5T;±14.5kA极向场线圈可提供10Vs磁通量变化.连接这些超导磁体与13台独立电源和一台制冷机之间的低温和超导部件组成大型供电供冷馈线,在EAST装置外部的外馈线包括:两组超导母线;13对电流引线及其杜瓦;一个大的低温分配恒温器,内装有40多个低温控制阀,4.4K液氦槽,3.8K过冷槽,78K液氮槽和4台超临界氦循环泵;五条低温传输线.本文介绍外馈线的设计、安装和运行情况.     

Surface chemistry and catalysis of oxide model catalysts from single crystals to nanocrystals

Fundamental understandings of surface chemistry and catalysis of solid catalysts are of great importance for the developments of efficient catalysts and corresponding catalytic processes, but have been remaining as a challenge due to the complex nature of heterogeneous catalysis. Model catalysts approach based on catalytic materials with uniform and well-defined surface structures is an effective strategy. Single crystals-based model catalysts have been successfully used for surface chemistry studies of solid catalysts, but encounter the so-called “materials gap” and “pressure gap” when applied for catalysis studies of solid catalysts. Recently catalytic nanocrystals with uniform and well-defined surface structures have emerged as a novel type of model catalysts whose surface chemistry and catalysis can be studied under the same operational reaction condition as working powder catalysts, and they are recognized as a novel type of model catalysts that can bridge the “materials gap” and “pressure gap” between single crystals-based model catalysts and powder catalysts. Herein we review recent progress of surface chemistry and catalysis of important oxide catalysts including CeO₂, TiO₂ and Cu₂O acquired by model catalysts from single crystals to nanocrystals with an aim at summarizing the commonalities and discussing the differences among model catalysts with complexities at different levels. Firstly, the complex nature of surface chemistry and catalysis of solid catalysts is briefly introduced. In the following sections, the model catalysts approach is described and surface chemistry and catalysis of CeO₂, TiO₂ and Cu₂O single crystal and nanocrystal model catalysts are reviewed. Finally, concluding remarks and future prospects are given on a comprehensive approach of model catalysts from single crystals to nanocrystals for the investigations of surface chemistry and catalysis of powder catalysts approaching the working conditions as closely as possible.     

线性变位极谱法研究 ⅩⅥ.铀(Ⅵ)—5—Br—PADAP—磺基水杨酸的配位吸附波

本文提出了铀(Ⅵ)-5-Br-PADAP-磺基水杨酸三元配合物的极谱配位吸附波。在pH为7.5-8.2的醋酸、三乙醇胺、乙醇底液中,该波的峰电位在-0.6855V(vs.SCE)。在1.00×10~(-7)-1.00×10~(-5)mol·dm~(-3)范围内,铀(Ⅵ)浓度与峰电流呈线性关系。对极谱波的电流、电位性质进行了研究,测定了配合物的组成、表观稳定常数和离解及生成速率常数。     

Structural and property correlations of ethylen-α-olefin copolymers

Ethylene-olefin copolymers differ from other polyethylenes in that:

A study of the ageing of the gel structure in a nonionic O/W cream by X-ray diffraction,differential scanning calorimetry and spin-lattice relaxation measurements

The time dependent changes of the lamellar gel structure in a nonionic O/W cream were studied. It appeared that the changes were connected with alterations in the hydrophilic layers of this lamellar gel structure. The structure of the hydrocarbon layers did not change. The alterations were induced by an increasing hydration of the surfactant molecules on cooling from the preparation temperature to room temperature. Ageing of the cream involves a decrease of the thickness of the hydrophilic layers and a change of the distribution of the surfactant molecules, resulting in, among other things, a decrease of the release rate of a hydrophilic drug. Ageing of the cream can be prevented by using the appropriate amount of starting materials or by the use of polymerizable surfactants. In the former case a cream, from which a drug is slowly released, is obtained. On the other hand, creams containing polymerized surfactants can release drugs at a relatively high rate.     

储氢合金电极中添加碳纳米管对SC型高功率电池性能的影响

在SC型高功率镍氢电池的负极中添加不同含量的碳纳米管制备SC型高功率镍氢电池, 并对其容量、大电流放电性能和循环寿命进行研究. 结果发现, 碳纳米管的加入有利于提高电池的综合性能, 尤其是大电流放电性能和循环寿命; 加入碳纳米管的含量为0.8%(w)时电池的综合性能最好, 其最高容量达到3369 mAh, 2C(6000 mA)循环600次后容量仍然保持在3280 mAh(97% DOD(放电深度))以上, 5C(15000 mA)循环180 次容量仍然有2850 mAh(89.1% DOD)以上.