应用玻璃微米/纳米管和循环伏安法研究邻菲咯啉加速质子在水/1,2-二氯乙烷界面的转移过程

利用循环伏安法研究了玻璃微米/纳米管支持的水/1,2-二氯乙烷(DCE)界面上邻菲咯啉加速质子的转移过程.将装有水溶液的微米/纳米管插入到DCE溶液中,可以形成微米/纳米级-液/液界面,在选定的实验条件下,其作用类似于微米/纳米电极.用微米管考察了此加速转移过程的半波电位与pH值(1.1～7.5)的关系,利用Matsuda等提出的理论公式计算了邻菲咯啉与质子在有机相和水相中的络合常数比.并用纳米管计算得到邻菲咯啉加速质子在水/DCE界面转移过程中的标准速率常数(k₀)和转移系数(α)分别为(0.183±0.054)cm/s和0.70±0.0.     

双通道微米管支撑的微-液/液界面上电荷转移反应的研究

将有机相和水相分别灌入双通道玻璃微米管θ管中的一个管中,利用θ管表面的亲水特征,在灌有有机相的微米管口附近形成微-液/液界面.利用循环伏安法研究了电荷在这种微-液/液界面上的转移反应,包括简单离子(四甲基铵离子TMA⁺)转移、加速离子转移(DB18C6加速K⁺离子)和电子转移(二茂铁/铁氰化钾+亚铁氰化钾体系)反应过程.结果表明,这种双通道微米管所得到的微-液/液界面具有不对称扩散场的特性.此装置是目前最简单的可用于研究液/液界面上的电荷转移反应的装置之一,即所谓的可进行"无溶液"液/液界面电化学及电分析化学研究的装置.     

质子化非那吡啶在功能化复合介孔膜修饰的液/液界面上的转移反应

采用循环伏安法和差分脉冲伏安法考察了临床药物盐酸非那吡啶在功能化复合介孔膜修饰的水/1,6-二氯己烷(W/DCH)界面上的转移行为. 研究结果表明, 盐酸非那吡啶中的非那吡啶(PAP) 可在酸性条件下发生质子化形成非那吡啶阳离子(HPAP⁺)并在该界面上发生转移. 根据循环伏安曲线峰电流与扫描速率的关系以及Randles-Sev$\check{c}$ik 方程, 计算得到HPAP⁺在复合介孔膜内水相中的扩散系数为5.14×10^-8 cm²/s. 研究发现, 相对于空白膜修饰的W/DCH界面, 该复合介孔膜修饰的W/DCH界面可增强非那吡啶阳离子转移时的电流响应, 并提升非那吡啶阳离子的检测性能. 另外, 利用液/液界面电化学方法绘制了非那吡啶在功能化复合介孔膜修饰的W/DCH界面上的离子分布图, 从而得到非那吡啶在该界面上不同条件下的分布情况及其分配系数和吉布斯转移自由能.     

氨基酸在亚微米级液/液界面上的转移反应

应用循环伏安法和微、纳米管系统地研究了二苯并18冠6(DB18C6)加速20种氨基酸在水/1, 2-二氯乙烷(W/DCE)界面上的转移反应. 实验结果表明电位窗内只有10种氨基酸, 即苯丙氨酸(Phe)、亮氨酸(Leu)、异亮氨酸(Ile)、缬氨酸(Val)、色氨酸(Trp)、甲硫氨酸(Met)、丙氨酸(Ala)、甘氨酸(Gly)、半胱氨酸(Cys)和谷氨酰胺(Gln), 其质子化后的一价阳离子能给出很好的加速离子转移伏安图, 并且转移反应机理符合界面配合/界面离解反应. 由稳态伏安图可求出DB18C6与不同氨基酸在1,2-二氯乙烷中的配合常数和界面配合反应的动力学常数. 实验结果表明, 与碱金属离子和DB18C6配合相比, 这10种氨基酸与DB18C6的配合选择性较低, 主要原因是由于氨基酸支链所引起的位阻效应以及本体有机溶剂的亲脂化稳定效应的协同作用. 除了甘氨酸和甲硫氨酸以外, 不同氨基酸与DB18C6配合反应的配合常数以及反应速率常数与其亲脂性量度(π)有良好的对应关系, 这表明质子化的氨基酸与DB18C6的异相配合反应不仅决定于离子与冠醚环的键合强度, 而且与氨基酸在转移过程中的吉布斯转移能有关, 而吉布斯转移能又与氨基酸自身的结构密切相关. 这一研究将对人们理解在生命体中氨基酸在载体蛋白的推动作用下越过生物膜的主动运送过程有较重要意义.     

Sr(NO_3)_2·DCH18C6配合物晶体结构与辐射稳定性

二环己基-18-冠-6(DCH18C6)可以有效地从高放废液中分离90Sr,对于减小放射性废物的危害和实现高放废物的减容有重要意义.由于在实际应用中DCH18C6处于射线照射下,其结构可能会被破坏并引起络合能力的变化,因此有必要对该配合物的辐射稳定性进行研究.本文合成了Sr(NO3)2?DCH18C6配合物晶体,并通过单晶X射线衍射(XRD)与扩展X射线吸收精细结构谱(EXAFS)等方法进行了表征,确定Sr2+与周围氧原子的配位数为10,Sr―O平均键长约为0.268 nm/0.266 nm(XRD/EXAFS).配位原子来自DCH18C6的六个氧原子以及两个作为双齿配体的硝酸根的四个氧原子.对该配合物晶体在空气中进行γ辐照,EXAFS结果表明吸收剂量为400 kGy时,Sr―O键长及配位数没有发生变化,配位结构没有被破坏,具有很好的耐辐照稳定性.显微红外光谱(Micro-FTIR)结果进一步证明辐照后冠醚环的部分C―H键氧化为羟基或羰基,但并不影响DCH18C6与Sr2+的配位结构.     

膜修饰液/液界面上亚叶酸离子的转移

采用复合介孔膜修饰水/1,6-二氯己烷(W/DCH)界面得到阵列介观W/DCH界面,利用循环伏安法、差分脉冲伏安法以及计时电量法考察了亚叶酸离子在该阵列介观W/DCH界面上的转移过程.结果表明,亚叶酸离子在膜修饰W/DCH界面上转移的电化学响应与复合介孔膜内表面活性剂十六烷基三甲基溴化铵密切相关.循环伏安结果表明,亚叶酸离子由膜内水相向油相转移的峰电流与扫描速率的平方根呈线性关系,根据Randles-Sevik方程,计算得到亚叶酸离子在复合介孔膜内水相中的扩散系数为2.036×10~(-8)cm~2/s.利用计时电量法测得亚叶酸离子在该界面上转移反应的标准速率常数为2.72×10~(-3)cm/s.     

阴离子交换膜修饰的水/1,2-二氯乙烷界面上SO42-离子的转移反应

将一种均相季铵型阴离子交换膜用于修饰水/1,2-二氯乙烷(W/DCE)界面,并利用循环伏安法、差分脉冲伏安法和计时电量法考察了该界面上强亲水性阴离子SO₄^2-的转移反应过程.研究结果表明,该阴离子交换膜所修饰的W/DCE界面比修饰前具有更宽的电化学窗口,而且在界面上可获得完整的SO₄^2-转移的循环伏安曲线和差分脉冲伏安曲线.其中,循环伏安曲线的峰电流与扫速平方根呈线性关系,SO₄^2-在膜内水相中的扩散系数为7.6×10^-8 cm²/s;差分脉冲伏安曲线的峰电流与SO₄^2-的浓度在5~25 mmol/L范围内呈线性关系.另外,利用计时电量法测得SO₄^2-在该界面上转移反应的标准速率常数为1.49×10^-3 cm/s.     

Sr(NO3)2·DCH18C6配合物晶体结构与辐射稳定性

二环己基-18-冠-6（DCH18C6）可以有效地从高放废液中分离⁹⁰Sr,对于减小放射性废物的危害和实现高放废物的减容有重要意义. 由于在实际应用中DCH18C6处于射线照射下,其结构可能会被破坏并引起络合能力的变化,因此有必要对该配合物的辐射稳定性进行研究. 本文合成了Sr（NO₃）₂·DCH18C6 配合物晶体,并通过单晶X射线衍射（XRD）与扩展X射线吸收精细结构谱（EXAFS）等方法进行了表征,确定Sr²⁺与周围氧原子的配位数为10,Sr―O平均键长约为0.268 nm/0.266 nm（XRD/EXAFS）. 配位原子来自DCH18C6 的六个氧原子以及两个作为双齿配体的硝酸根的四个氧原子. 对该配合物晶体在空气中进行γ辐照,EXAFS结果表明吸收剂量为400 kGy时,Sr―O键长及配位数没有发生变化,配位结构没有被破坏,具有很好的耐辐照稳定性. 显微红外光谱（Micro-FTIR）结果进一步证明辐照后冠醚环的部分C―H 键氧化为羟基或羰基,但并不影响DCH18C6与Sr²⁺的配位结构.     

应用扫描电化学显微镜研究水/1,2-二氯乙烷界面上离子诱导的电子转移反应

应用扫描电化学显微镜和微电极技术研究了水/1,2二氯乙烷界面上的反向电子转移反应.分别以K₄Fe(CN)₆和7,7,8,8四氰代二甲基苯醌(TCNQ)作为水相和有机相的电活性物质,通过选择合理的共同离子(TPAs⁺与TBA⁺)来控制界面电位差,实现了这一在热力学上通常不可能实现的反向电子转移反应.利用扫描电化学显微镜给出的正负反馈信息,研究了界面电位差驱动的液/液界面上的电子转移反应,并进一步得到了在不同的共同离子浓度比时,此异相界面反应速率常数k_f为1.3×10^-31.8×10^-2cm/s(共同离子为TBA⁺)和2.5×10^-32.8×10^-2cm/s(共同离子为TPAs⁺).验证了此反应速率常数k_f是由界面电位差所决定的.在此实验条件下,此反应速率常数kf与界面电位差的关系遵守Butler-Volmer公式.     

冠醚配合物热力学性质的研究(Ⅴ)——碱金属及碱土金属离子与2,3-苯并-11-甲基-18-冠-6的配位反应的量热滴定研究

用自制滴定量热计研究了70%(W/W)甲醇中2,3-苯并-11-甲基-18-冠-6(BC1-18C6)与Na、K、Rb、Cs、Ca、Mg、Sr、Ba8种碱金属与碱土金属氯化物的配位作用,直接计算了配合物稳定常数及配位反应热函,获得了碱金属与碱土金属稳定性及热函大小的相对顺序.     

Ionic liquid/ionic liquid dispersive liquid-liquid microextraction

In this article, a novel and simple microextraction method, termed ionic liquid/ionic liquid dispersive liquid–liquid microextraction (IL/IL‐DLLME), has been designed and developed for the rapid enrichment and analysis of environmental pollutants. Instead of using hazardous organic solvents, two kinds of ILs, hydrophobic IL and hydrophilic IL, were used as extraction solvent and disperser solvent in IL/IL‐DLLME step, respectively. Permethrin and biphenthrin, two of the often‐used pyrethroid pesticides, were used as model compounds. Factors that may affect the enrichment efficiencies were investigated and optimized in detail. Under optimum conditions, permethrin and biphenthrin exhibited a wide linear relationship over the range 1–100 μg/L. For permethrin and biphenthrin, the precisions were 4.65–7.78%, and limits of detection were found to be 0.28 and 0.83 μg/L, respectively. Satisfactory results were achieved when the present method was applied to analyze the target compounds in real‐world water samples with spiked recoveries over the range 84.1–113.5%. All these facts indicated that IL/IL‐DLLME is a simple and rapid alternative for the enrichment and analysis of environmental pollutants and will have a wide application perspective in the future.     

Trace analysis of rimantadine in human urine after dispersive liquid liquid microextraction followed by liquid chromatography–post column derivatization

The first dispersive liquid liquid microextraction scheme followed by liquid chromatography‐post column derivatization for the determination of the antiviral drug rimantadine in urine samples is demonstrated. The effect of the type and volume of organic extraction solvent, type and volume of disperser solvent, sample pH, ionic strength, extraction time, and centrifugation speed on the extraction efficiency were studied. Rimantadine and the internal standard (amantadine) were chromatographed using a reversed phase monolithic stationary phase with a mixture of equal volumes of methanol and phosphate buffer (pH = 3) as mobile phase. On‐line post‐column derivatization of the analyte was performed using a “two‐stream” manifold with o‐phthalaldehyde and N‐acetyl‐cysteine at alkaline medium. Under the optimized extraction conditions, the enrichment factor of rimantadine was 58. The linear range was 5–100 µg/L with correlation coefficient r of 0.9984 while the limit of detection achieved was 0.5 µg/L. The within‐day and between‐day precision for the tested concentration levels were less than 14.3% and the mean recoveries obtained from the spiked samples were ranged between 87.5 and 113.9%. The main advantages of the proposed method are the simplicity of operation, rapidity, low cost, and low limit of detection of the analyte.     

Switchable anti-peeping film for liquid crystal displays from polymer dispersed liquid crystals

Liquid crystals displays (LCDs) currently dominate the display market, wherein a wide viewing angle is considered as one of the most important characteristics. However, for LCDs with wide viewing angles, some private information inevitably becomes more visible; thus, an LCD with a switchable viewing angle has attracted greater interest. Here, we report a novel switchable viewing angle film that can make the viewing angle of an LCD electrically switchable between ±30° and ±60°, i.e. between an anti-peeping mode and a share mode, by 5.0 V is turned on and off, respectively. The response time necessary to change between the modes is in milliseconds. It is believed that it has potential applications in LCDs with high quality.     

Ionic liquid foam floatation coupled with ionic liquid dispersive liquid–liquid microextraction for the separation and determination of estrogens in water samples by high‐performance liquid chromatography with fluorescence detection

An ionic liquid foam floatation coupled with ionic liquid dispersive liquid–liquid microextraction method was proposed for the extraction and concentration of 17‐α‐estradiol, 17‐β‐estradiol‐benzoate, and quinestrol in environmental water samples by high‐performance liquid chromatography with fluorescence detection. 1‐Hexyl‐3‐methylimidazolium tetrafluoroborate was applied as foaming agent in the foam flotation process and dispersive solvent in microextraction. The introduction of the ion‐pairing and salting‐out agent NH₄PF₆ was beneficial to the improvement of recoveries for the hydrophobic ionic liquid phase and analytes. Parameters of the proposed method including concentration of 1‐hexyl‐3‐methylimidazolium tetrafluoroborate, flow rate of carrier gas, floatation time, types and concentration of ionic liquids, salt concentration in samples, extraction time, and centrifugation time were evaluated. The recoveries were between 98 and 105% with relative standard deviations lower than 7% for lake water and well water samples. The isolation of the target compounds from the water was found to be efficient, and the enrichment factors ranged from 4445 to 4632. This developing method is free of volatile organic solvents compared with regular extraction. Based on the unique properties of ionic liquids, the application of foam floatation, and dispersive liquid–liquid microextraction was widened.     

Integrated and topological liquid crystal photonics

This contribution is a personal view of the rapidly developing subfield of nematic colloids, with an emphasis on possible applications of these materials in future photonic microdevices. A brief overview of the most important phenomena, observed in the past decade in nematic colloids is given. It is explained why integrated photonics based on microstructured liquid crystals is feasible and future challenges towards the realisation of integrated liquid crystal microphotonics are discussed.     

A greener electrochromic liquid crystal based on ionic liquid electrolytes

An electrochromic liquid crystal (ECLC) material composed of only liquid crystal (LC) and ionic liquid (IL) was developed. The LC containing the substituted diphenylacetylene serves as electrochromic (EC) material to realise transmittance and colour change under the direct current (DC) field, while the IL with the designable cation and anion served as electrolyte. Herein, a series of IL electrolytes was screened to investigate how IL tunes the electro-optic performance of the ECLC cell. By testing the electrochemistry window of ILs in EC cells, IL with the [NTf₂]^? anion shows adequate electrochemical stability when the EC material undergoes oxidation and reduction. The electro-optic performance of ECLC containing 1-ethoxy-4-[2-(4-pentylphenyl) ethynyl]-benzene (PEB) and IL was then evaluated by UV-vis spectrometry under the control of an electrochemical work station. Compared with other PEB-IL, PEB-[Bmim][NTf₂] with [Bmim][NTf₂] electrolyte shows a satisfactory transmittance at low operating voltage. Furthermore, Pd NPs in situ formed in [Bmim][NTf₂] reduced the EC potential and improved the light scattering of the ECLC cell. In this work, we also designed a bifunctional device based on polymer dispersed liquid crystal (PDLC) that hosts electrochromic guest molecules, and analysed the electro-optical and electrochromic properties of LC electrolyte mixtures, in order to gain control of the incident daylight and glare in building and automotive applications.     

Dispersive liquid–liquid microextraction combined with high performance liquid chromatography-DAD detection for the determination of sulfonylurea herbicides in water samples

A new method for the determination of four sulfonylurea herbicides (metsulfuron-methyl, chlorsulfuron, bensulfuron-methyl and chlorimuron-ethyl) in water samples was developed by dispersive liquid–liquid microextraction coupled with high performance liquid chromatography-diode array detector. Parameters that affect the extraction efficiency, such as the kind and volume of the extraction and disperser solvent, extraction time and salt addition, were investigated and optimised. Under the optimum conditions, the enrichment factors were in the range between 102 and 216. The linearity of the method was obtained in the range of 1.0–100 ng mL^?1 with the correlation coefficients (r) ranging from 0.9982 to 0.9995. The method detection limits were 0.2–0.3 ng mL^?1. The proposed method has been successfully applied to the analysis of target sulfonylurea herbicides in river, stream and well water samples with satisfactory results.     

Synthesis and properties of reactive liquid crystal monomers and side-chain liquid crystalline polymers

Two nematic liquid crystal (LC) monomers containing double bonds in the side chain were designed and synthesised. Length of the side groups varied from 1 to 2 methylene units. The side-chain polymers were synthesised by hydrosilylation reaction. The molecular structures of the intermediates and the LC monomers were characterised by Fourier transform infrared, elemental analysis and nuclear magnetic resonance spectroscopy. The thermal phase behaviour of the monomers and polymers were investigated by differential scanning calorimetry and polar optical microscopy coupled with hot stage. The LC monomers showed only one nematic mesophase in the cooling process. And, the two polymers exhibit an enantiotroppic nematic mesophase either in the heating or in the cooling process.     

Computer simulation of liquid crystals

Summary We review recent progress in the computer simulation of liquid crystals, with special emphasis on hard particle models. Surprisingly, the simplest molecular models, taking account only of molecular size and shape, are sufficient to generate a wide variety of liquid crystalline phases, closely analogous to those observed in real life. Thermodynamic stability of different phases is very sensitive to shape, and presumably will also be sensitive to further details of intermolecular interactions as they are incorporated into the model. Realistic atom-atom potential models of liquid crystals are available, but the associated simulations are quite expensive. Thus, while idealized models may be used to study quite general, fundamental properties of mesophases, the modelling of specific liquid crystal systems in a realistic way remains a great challenge. Progress continues to be made on both these fronts.     

Homogeneous liquid–liquid extraction combined with high performance liquid chromatography–fluorescence detection for determination of polycyclic aromatic hydrocarbons in vegetables

In this article, homogeneous liquid–liquid extraction (HOLLE), combined with HPLC-fluorescence detector (HPLC-FLD), has been developed for the extraction and determination of polycyclic aromatic hydrocarbons (PAHs) in vegetables. ACN was used as extraction solvent for the extraction of target analytes from vegetables. When the previous extraction process was over, the ACN extract was transferred to the water-immiscible organic phase, tetrachloroethane, used as extraction solvent in HOLLE procedures. Under the optimum conditions, repeatability was carried out by spiking PAHs at concentration level of 12.5 μg/kg, the RSDs varied between 1.1 and 8.5% (n = 3). The LODs, based on S/N of 3, ranged from 0.025 to 0.25 μg/kg. Relative recoveries of PAHs from cucumber and long crooked squash samples were in the range of 72.4–104.9% and 65.5–119.3%, respectively. Compared with the conventional extraction method, the proposed method has the advantage of being quick, easy to operate, and having low consumption of organic solvent.