薄层法研究十二烷基苯磺酸钠对硝基苯/水界面电子转移的影响

用薄层法研究了阴离子表面活性剂十二烷基苯磺酸钠(SDBS)对硝基苯/水界面电子转移的影响. 实验结果表明, 随着水相中十二烷基苯磺酸钠浓度的增加, 有机相中十甲基二茂铁(DMFc)和水相中Fe(CN)₆^3-发生的界面双分子反应的阴极平台电流呈现递减趋势, 但是界面双分子反应速率常数却呈递增趋势. 这是由于阴离子表面活性剂十二烷基苯磺酸钠在硝基苯/水界面形成了修饰层, 影响了界面双电层结构. SDBS在液/液界面的吸附为Langmuir吸附.     

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.     

用三电极系统研究水/硝基苯界面上的电荷转移反应

将含有氧化还原电对的水溶液滴涂在铂电极上, 然后将该电极插入到硝基苯溶液中, 与参比电极和对电极构成常规的三电极系统. 利用该系统研究了水相与硝基苯相之间界面上的离子转移和电子转移反应. 以铁氰化钾/亚铁氰化钾为电对观察到钾离子在水/硝基苯界面上的转移反应以及铁氰化钾与二茂铁之间的电子转移反应；以硫酸铁/硫酸亚铁为电对观察到锂离子、钠离子、氢离子、铵离子和钾离子在水/硝基苯界面的转移. 利用该方法得到的离子的转移式电位和Gibbs转移能与用四电极系统和其他方法所测定的结果相接近.     

应用扫描电化学显微镜研究极化液/液界面上的电子转移反应

将含有氧化还原电对的水溶液滴涂在铂盘电极表面, 然后将该电极插入到1,2-二氯乙烷溶液中, 形成稳定的油/水界面. 液滴中的K3Fe(CN)6和K4Fe(CN)6氧化还原电对既可以作为水相中的参比电对参与控制液/液界面上的电势差, 同时又可以作为水相的电子授受体参与界面上的电子转移反应. 结合扫描电化学显微镜电化学系统的特点, 利用其双恒电位仪分别控制界面电势差和现场扫描的优点, 通过扫描电化学显微镜的渐进曲线得到了不同界面电势差控制的电子转移反应速率常数. 实验结果表明, 应用此方法获得的液/液界面可以被外加电位极化, 在一定的电势差范围内, 反应速率常数与界面电势差的关系遵守Butler-Volmer公式.     

三相电极法及其在液/液界面铬(Ⅵ)离子转移研究中的应用

将含有氧化还原探针的硝基苯溶液滴到边平面热解石墨(EPPG)电极上,然后将该电极插入到电解质水溶液中,从而使硝基苯、石墨表面以及水溶液形成一个三相接界线,即形成了EPPG三相电极。利用循环伏安法对EPPG三相电极法的原理进行了研究,得到了比文献报道更理想的液/液界面离子转移热力学数据。本研究还观察到铬(Ⅵ)离子在水相/硝基苯相界面上的转移反应,并测定了铬(Ⅵ)的离子转移热力学数据;同时还分别利用方波伏安法和傅里叶变换-方波伏安法结合"准可逆最大"现象对铬(Ⅵ)在水相/硝基苯相界面上的离子转移动力学进行了比较研究。     

γ-二氧化锰电极/溶液界面电子转移动力学

以 [Fe( CN) 6]3- 为受体 ,用大范围分析法 ( global analysis)研究了 γ-二氧化锰电极 /溶液界面的电子转移反应。结果表明 :二氧化锰电极的电子转移速率常数随过电位的变化关系较复杂 ,出现两个反转区 ,与经典的 Marcus电子转移理论不相符合。但 Yuri G.Boroda等人对半导体电极 /溶液界面提出的模型能够很好地解释本文的实验结果 ,表明其电子转移反应是分两步进行的。     

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.     

固载化冠醚二苯并-18-冠-6在苯甲酸丁酯合成反应中的相转移催化作用

在交联聚乙烯醇(CPVA)微球表面固载冠醚二苯并-18-冠-6 (DBC), 从而制得三相相转移催化剂DBC-CPVA; 在此基础上, 以苯甲酸钾与溴代正丁烷的酯化反应为模型反应体系, 重点研究固体催化剂DBC-CPVA的相转移催化性能, 考察主要因素对液-固-液三相相转移催化反应的影响. 结果表明, 在本研究体系中, 水相中的苯甲酸钾与有机相中的溴代正丁烷可顺利地发生酯化反应, 这一结果显示出固载于DBC-CPVA表面的DBC与K+离子形成的络合物阳离子, 能有效地将苯甲酸根负离子转移至有机相, 使酯化反应顺利地进行. 有机相的极性越强, 酯化反应的速率越快, 溴代正丁烷的转化率越高; 有机相与水相体积比为1:4时, 酯化反应具有最大的速率, 溴代正丁烷的转化率可达70%. 固体催化剂DBC-CPVA循环使用8次, 催化活性保持稳定.     

通过扫描离子电导显微镜探测水/硝基苯界面的结构

北京大学邵元华教授课题组最近报道了一种探测液/液界面(两互不相溶溶液界面)微观结构的新方法(Chem.Sci.,2011,2:1523~1529)。该方法利用扫描离子电导显微镜(SICM)与内半径小于5 nm的超微玻璃管探针相结合,获得了水/硝基苯(W/NB)界面的离子分布以及界面厚度等信息。该研究基本原理如图1所示,SICM的两根电极分别置于纳米管探针以及顶部有机相     

相转移催化法制备侧链带有醛基的聚苯乙烯交联微球

首先使氯甲基聚苯乙烯交联微球（CCMPSt）在有机相中充分溶服,然后通过相转移催化剂（季铵盐）的作用,将水相中对羟基苯甲醛所产生的负氧离子转移至有机相,使之与CCMPSt微球表面的苄氯基团发生亲核取代反应,从而将CCMPSt微球转变为侧链带有醛基的聚苯乙烯交联微球（Aldehyde—CPSt）．本研究重点考察了各种因素对液-液-固三相体系中相转移催化过程及取代反应的影响规律,较深入地探讨了反应机理．研究结果表明,通过相转移催化剂的作用,可将亲核取代试剂对羟基苯甲醛负氧离子不断地从水相转移至有机相,在有机相与交联微球CCMPSt的界面发生取代反应,从而将CCMPSt微球顺利地转变为功能微球Aldehyde—CPSt．有机溶剂的极性越强,对CCMPSt微球的溶服性能越好,取代反应速率越快;相转移催化剂季铵离子上的碳链对称性越好及碳链越长,相转移催化的效果越好;有机相与水相的比例对相转移催化效果也有较大的影响．     

Cyclic voltammetry of the electron transfer reaction between bis(cyclopentadienyl)iron in 1,2-dichloroethane and hexacyanoferrate in water.

The electron transfer (ET) reaction between bis(cyclopentadienyl)iron(II) ([Fe(II)(C(5)H(5))2]) in 1,2-dichloroethane (1,2-DCE) and hexacyanoferrate redox couple ([Fe(II/III)(CN)6](4-/3-)) in water (W) at the interface has been studied by using cyclic voltammetry. The voltammetric results can be explained well by a theoretical equation for the so-called IT-mechanism, in which a homogeneous ET reaction between [Fe(C(5)H(5))2] (partially distributed from 1,2-DCE) and [Fe(CN)6](3-) takes place in the W phase and the resultant [Fe(C(5)H(5))2]+ ion is responsible for current passage across the interface. The forward rate constant of the homogeneous ET reaction, [Fe(C(5)H(5))2] + [Fe(CN)6](3-) = [Fe(C(5)H(5))2]+ + [Fe(CN)6](4-) in W phase, k(f)(IT), was determined to be (2.9 +/- 2.2)x 10(10) M(-1) s(-1), which was in good agreement with k(f)(IT) = (3.2 +/- 2.0)x 10(10) M(-1) s(-1), which had been determined by using normal-pulse voltammetry.     

二茂铁衍生物L—B膜修饰SnO2电极的性能

用外层单电子快速转移的氧化还原剂二茂铁及其衍生物修饰电极,在电极/溶液界面作为电子传递的中介物,可使电极上进行的慢反应得到加速、起中介催化作用。目前研究较多的是共价键合和高分子膜的修饰,其他方式的修饰报道不多。用能实现分子有序化排列的L-B膜技术进行氧化还原电活性分子的修饰电极还未见报道。我们用L-B膜技术在SnO_2电极上修饰了二茂铁的衍生物-硬脂酸二茂铁酯(FcOCOC_(17)H_(35))双亲化合物,曾研究了修饰膜的电化学可逆行为和稳定性。本文研究硬脂酸二茂铁酯L-B膜修饰的SnO_2电极     

Probing TCNQ‐mediated Metal Reduction Reactions at Liquid‐liquid Interface with SECM

Metal reduction at the interface between two immiscible electrolyte solutions (ITIES) has been studied with scanning electrochemical microscopy (SECM). Metal cations in the aqueous phase are reduced by 7,7,8,8‐tetracyanoquinodimethane anion (TCNQ^?) residing in the oil phase, methyl isobutyl ketone (MIBK). TCNQ^? is formed at the SECM tip by reducing TCNQ, which results in a positive feedback loop between the tip and the ITIES when an electron is donated to a metal cation. The effect of the Galvani potential difference on the rate of the interfacial electron transfer was investigated, establishing the potential difference either by an additional substrate electrode in the aqueous phase or by an a common ion in both phases. It is shown that the Galvani potential difference as a driving force does enable TCNQ^? mediated Cu²⁺ reduction. Finite element method (FEM) simulations were run to provide information on the reaction kinetics and stoichiometry.     

1,4-二氧六环介质中辣根过氧化物酶电极的性能研究

用交联法制备辣根过氧化物酶(HRP)电极, 在1,4-二氧六环介质中研究其电化学行为。实验表明, 固定化的HRP在有机相中仍保持活性并可与电极进行直接电子传递, 因而能在没有其它电子传递体存在的条件下催化H~2O~2的电化学还原反应。当亚铁氰化物与酶共修饰至电极上之后, 它起着电子传递体的作用, 使HRP电极的性能大为改善。根据不同条件下得到的动力学参数, 讨论了影响酶电极性能的因素。     

Electroneutrality coupling of electron transfer at an electrode surface and ion transfer across the interface between thin-layer of 1-octyl-3-methylimidazolium bis(perfluoroalkylsulfonyl)imide covering the electrode surface and an outer electrolyte solution.

The electrode reaction of decamethylferrocene (DMFc) dissolved in a thin layer of a room-temperature molten salt (RTMS), 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C8mimC1C1N) or 1-octyl-3-methylimidazolium bis(pentafluoroethylsulfonyl)imide (C8mimC2C2N), on a self-assembled monolayer-modified gold electrode is coupled with the ion transfer across the interface between the RTMS and the outer aqueous solution (W) to give a voltammogram whose shape resembles a voltammogram of a simple one-electron transfer process. The electroneutrality of the RTMS layer during the oxidation of DMFc to decamethylferricenium ion is maintained by the concomitant dissolution of C8mim+ ion from the RTMS phase to the W phase, and the reduction of decamethylferricenium ion to DMFc is accompanied by the transfer of either C1C1N- or C2C2N- from RTMS to W. The midpoint potential of the voltammogram varies with the concentration of the salt in the aqueous phase, C8mimCl or LiCnCnN (n = 1 or 2), in a Nernstian manner, showing that the phase-boundary potential between the RTMS and the W is controlled by the partition of these ions. Although the phase-boundary potential across the RTMS / W interface is Nernstian with respect to the ions common to both phases at the equilibrium, the polarization at the RTMS / W interface under current flow distorts the shape of the voltammograms, resulting in a wider peak separation in the voltammogram.     

Gold nanoparticles attached NH2+ ion implantation-modified indium tin oxide electrode: Characterization and electrochemical studies

An NH2+ ion implantation-modified indium tin oxide film was prepared and the implantation of amino groups on the indium tin oxide substrate was verified by X-ray photoelectron spectroscopy analysis.The gold nanoparticles attached surface could be obtained by self-assembly of different sized colloidal gold nanoparticles onto the NH2+ ion implantation-modified indium tin oxide surface.By scanning electron microscopy and electrochemical techniques,the as-prepared AuNPs attached NH2+ ion implantation-modified indium tin oxide electrode was characterized and compared with bare indium tin oxide electrode.Using a [Fe(CN)6]3 /[Fe(CN)6]4 redox probe,the increasingly facile heterogeneous electron transfer kinetics resulting from the attached gold nanoparticle arrays was observed.The gold nanoparticle arrays exhibited high catalytic activity toward the electro-oxidation of nitric oxide,which could provide electroanalytical application for nitric oxide sensing.     

A comparative study of the anion transfer kinetics across a water/nitrobenzene interface by means of electrochemical impedance spectroscopy and square-wave voltammetry at thin organic film-modified electrodes

The kinetics of the transfer of a series of hydrophilic monovalent anions across the water/nitrobenzene (W/NB) interface has been studied by means of thin organic film-modified electrodes in combination with electrochemical impedance spectroscopy and square-wave voltammetry. The studied ions are Cl-, Br-, I-, ClO4-, NO3-, SCN-, and CH3COO-. The electrode assembly comprises a graphite electrode (GE) covered with a thin NB film containing a neutral strongly hydrophobic redox probe (decamethylferrocene or lutetium bis(tetra-tert-butylphthalocyaninato)) and an organic supporting electrolyte. The modified electrode is immersed in an aqueous solution containing a supporting electrolyte and transferring ions, and used in a conventional three-electrode configuration. Upon oxidation of the redox probe, the overall electrochemical process proceeds as an electron-ion charge-transfer reaction coupling the electron transfer at the GE/NB interface and compensates ion transfer across the W/NB interface. The rate of the ion transfer across the W/NB interface is the limiting step in the kinetics of the overall coupled electron-ion transfer reaction. Moreover, the transferring ion that is initially present in the aqueous phase only at a concentration lower than the redox probe, controls the mass transfer regime in the overall reaction. A rate equation describing the kinetics of the ion transfer that is valid for the conditions at thin organic film-modified electrodes is derived. Kinetic data measured with two electrochemical techniques are in very good agreement.     

Neurotransmitter Biomolecule Transfers Across Liquid/Liquid Interface Through A Thick Organic Membrane-Modified Electrode

Electrochemical studies at liquid/liquid interfaces (L/L, or soft interfaces) have disclosed a biomimetic model to mimic charge transfers at cytomembrane surface. Herein, we reported two neurotransmitter biomolecules of dopamine and adrenalone across the L/L interface by a thick organic membrane-modified electrode. This system comprised polarized electrode/oil and oil/water interfaces in series in which the electron transfer (ET) of redox 7,7,8,8-tetracyanoquinodimethane (TCNQ) at electrode/oil interface drove ion transfer (IT) of biomolecules at oil/water interface. This ET-IT coupled reaction overcame the limitation of polarized potential window at conventional single polarized L/L interface. The crucial design of a thick organic membrane could ensure the generated TCNQ anions maintained at electrode/oil interface during the voltammetry, which could not result in interruptions to biomolecule transfers. Through this system, their Gibbs transfer free energies were accurately determined (44.4 and 39.4 kJ mol^?1 for dopamine and adrealone, respectively). Moreover, facilitated biomolecule transfers were evaluated by crown ionophores where both facilitated numbers and constants were determined simultaneously. Owing to the simple electrochemical setup, this system would hold great potentials in future hydrophilic biomacromolecule transfers, such as DNA, peptides and proteins.