Electrochemical behaviour of EOP at the liquid/liquid interface and its determination

A new approach to the determination of emulsifier OP (EOP, a nonionic surfactant) is proposed, based on the voltammetry of the EOP facilitating Ca(2+) transfer across the water/nitrobenzene (w/nb) interface. The peaks obtained with cyclic voltammetry at the w/nb interface correspond to the transfer of the coordination complex ion [Ca(EOP)](2+) from the aqueous to the nonaqueous phase. The calibration graph is linear in the range of 1.5x10(-5)-5x10(-4) mol l(-1). The ionic surfactants have a very minor effect on detection.     

Amperometric proton selective sensors utilizing ion transfer reactions across a microhole liquid/gel interface

A new cost-effective amperometric proton selective sensor utilizing a single microhole interface between two immiscible electrolyte solutions (ITIES) is developed. The sensing methodology is based on measuring currents associated with proton transfer across the interface assisted by a proton selective ionophore. The ellipse shaped micro-interface was first fabricated by simple mechanical punching with a sharp needle on a thin PVC film (12 μm thick) commercially available as a food wrapping material. The microhole was then filled up with a gellified polyvinylchloride (PVC)-2-nitrophenyloctylether (NPOE) to create a single microhole liquid/liquid interface. Direct ion transfer reactions across the polarized interface serving as ion sensing platforms were studied using cyclic voltammetry. In order to enhance the selectivity of proton sensing, a proton selective ionophore, octadecyl isonicotinate (ETH1778), was incorporated into the organic gel layer and their electrochemical sensing characteristics were investigated using cyclic voltammetry and differential pulse stripping voltammetry. As an example, we employed the proton selective sensor for the determination of glucose concentrations. The detection scheme involves two steps: (i) protons are first generated by the oxidation of glucose with glucose oxidase in the aqueous phase; and (ii) the current associated with the proton transfer across the interface is then measured for correlating the concentration of glucose.     

薄层液/液界面电子转移动力学的研究进展

薄层循环伏安法是研究液/液界面电荷转移的一种新方法,具有简单、快速、易操作的优点。文章回顾了液/液界面电化学的发展历史,介绍了薄层法的实验原理,对其在电化学中的应用和研究进展进行了评述,总结了界面驱动力与电子转移速率的关系。     

Cyclic voltammetry of highly hydrophilic ions at a supported liquid membrane

Cyclic voltammetry has been used to study the coupling of ion transfer reactions at a liquid membrane. The liquids are either supported by a porous hydrophobic membrane (polyvinylidene difluoride, PVDF) when the organic solvent is non-volatile (o-nitrophenyloctylether) or are merely a free standing organic solvent layer such as 1,2-dichloroethane comprised between two hydrophilic dialysis membranes supporting the adjacent aqueous phases. The passage of current across the liquid membrane is associated with two ion transfer reactions across the two polarised liquid liquid interfaces in series. It is shown that it is possible to study the transfer of highly hydrophilic ions at one interface by limiting the mass transfer of the other ion transfer reaction at the other interface. Indeed, for systems comprising an ion M in one aqueous phase and a reference ion R partitioned between the membrane and the other aqueous phase, the observed and simulated cyclic voltammograms have a half-wave potential determined by the Gibbs energy of transfer of M transferring at one interface and by the limiting mass transfer of R at the other interface. This new methodology opens a way to measure the Gibbs energy of transfer of highly hydrophilic or hydrophobic ions, which usually limits the potential window at single liquid liquid interfaces (ITIES).     

Heterogeneous electron transfer kinetics at the ionic liquid/metal interface studied using cyclic voltammetry and scanning electrochemical microscopy

The electrochemical behavior of a redox-active, ferrocene-modified ionic liquid (1-ferrocenylmethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) in acetonitrile and in an ionic liquid electrolyte (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) is reported. Reversible electrochemical behavior was observed in each electrolyte with responses typical of those for unmodified ferrocene observed in each medium. In the ionic liquid electrolyte, the diffusion coefficient of the redox-active ionic liquid increased by a factor of 5 upon increasing the temperature from 27 to 90 degrees C. The kinetics of electron transfer across the ionic liquid/electrode interface were studied using cyclic voltammetry, and the standard heterogeneous electron transfer rate constant, k (0) was determined to be 4.25 x 10 (-3) cm s (-1). Scanning electrochemical microscopy was then also used to probe the heterogeneous kinetics at the interface between the ionic liquid and the solid electrode and conventional kinetic SECM theory was used to determine k (0). The k (0) value obtained using SECM was higher than that determined using cyclic voltammetry. These results indicate that SECM is a very useful technique for studying electron transfer dynamics in ionic liquids.     

Electron transfer kinetics at polarized nanoscopic liquid/liquid interfaces

Rapid kinetics of electron transfer (ET) reactions across the interface between water and 1,2-dichloroethane were measured by steady-state voltammetry at nanopipet electrodes (50- to 400-nm orifice radius). The origins of previously reported imperfect voltammetric responses of ET reactions at micropipets were investigated. Several new experimental systems were explored, and two of them yielded high-quality voltammograms suitable for kinetic experiments. The determined standard rate constants were compared to those measured previously at polarized and nonpolarized liquid/liquid interfaces. The effect of the interfacial dimensions on the magnitude of the apparent ET rate constant is discussed. A new approach to ET kinetic measurements based on the use of the scanning electrochemical microscope with a nanopipet tip and a metallic substrate has been developed and employed to check the validity of determined kinetic parameters.     

端烯基液晶冠醚推动钠离子在微液/液界面的转移

用循环伏安法研究新型载体端烯基液晶冠醚推动钠离子的转移,结果表明,钠离子的转移由扩散控制.探讨了影响钠离子转移的因素,如端烯基液晶冠醚和钠离子的浓度等.求算出端烯基液晶冠醚在1,2-二氯乙烷中的扩散系数为(2.61±0.12)×10^-6cm²/s,端烯基液晶冠醚和钠离子在1,2-二氯乙烷中所形成的配合物稳定常数lgβ_o=5.7.     

Study on the Voltammetric Behaviour of Emulsifier OP across the Water-nitrobenzene Interface and its Application

Surfactantsareproducedworldwideinlargeamountsandwidelyusedinhouseholdorindustrialcleaners,cosmetic,researchlaboratories,etc.Manyelectfoanalyticalmethodsdevotedtosurfactantanalysishavebeenproposed',suchaspotentiometry,amperometry,tensammetry,electrocaPillarymeasurements.InthispaPer,emulsifierOP,asanewionophore,hasbeenintroducedtofacilitatemetaliontransferacrossaliquid/liquidinterface.ThevoltammetricbehaviourofemulsifierOP(EOP)whichfacilitatesthetransferofNa acrossthewater/nitrobebzene(w/nb)…     

Selective silver ion transfer voltammetry at the polarised liquid/liquid interface

Transfer of silver ions across the water/1,2-dichloroethane interface was studied by cyclic voltammetry (CV). In the absence of added neutral ionophore, Ag+ transferred across the interface when the organic phase contained either tetraphenylborate or tetrakis(4-chloro)phenylborate anions, but this transfer was not possible in the presence of organic phase hexafluorophosphate or perchlorate anions. The ion transfer processes observed were independent of the nature of the organic phase cation. The CV in the presence of tetraphenylborate exhibited a shape consistent with an ion transfer followed by chemical reaction; the rate constant for the following chemical reaction was 0.016 s(-1). In the presence of tetrakis(4-chloro)phenylborate, a return peak equivalent in magnitude to the forward peak was observed, indicative of a simple ion transfer reaction uncomplicated by accompanying chemical reactions. The selectivity of the transfer was assessed with respect to other metal cations: no transfers for copper, cadmium, lead, bismuth, cobalt, nickel, palladium or zinc were observed. The selectivity of the transfer suggests this can form the basis of a selective voltammetric methodology for the determination of silver ions.     

Electron transfer across the polarized interface between water and a hydrophobic redox-active ionic liquid

Here we report the synthesis of a new redox-active ionic liquid (IL), (ferrocenylmethyl)dodecyldimethylammonium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate that can be used to form the polarizable water│IL interface at an elevated temperature (43 °C). Experimental approach is based on the cyclic voltammetry of the charge transfer processes occurring at the IL membrane supported on a thin microporous filter. Evidence is provided of the interfacial electron transfer between the ferrocenated cation of IL and an electron acceptor, IrCl₆^2?, in the adjacent aqueous phase.     

中性载体ETH157推动Cu^2＋离子在水／硝基苯界面上的转移

本文用循环伏安法研究了中性载体ETH157推动Cu~(2+)离子在水/硝基苯界面上的转移过程,结果发现在水/硝基苯界面上,Cu~(2+)离子与ETH157形成了逐级配合物,并伴有吸附现象产生,考察了有关过程的转移机制并讨论了相应的实验现象。     

Chemical capacitance of nanoporous-nanocrystalline TiO2 in a room temperature ionic liquid

The electrochemical behaviour of nanoporous TiO(2) in a room temperature ionic liquid (RTIL), 1-ethyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)amide (EMITFSI), was investigated by cyclic voltammetry (CV) and impedance spectroscopy. Exponentially rising currents in voltammetry were attributed to the charging/discharging of electrons in the TiO(2) film and a charge transfer mechanism. The main features of the voltammetry and impedance followed the same trends in the ionic liquid as in other organic solvents and also in aqueous electrolytes. In the presence of lithium ions, the onset potential of the charge accumulation increased due to the change of the initial position of the TiO(2) conduction band. The results show that substitution of organic solvents contained in solar cells, supercapacitors or other electrochemical devices is in general feasible, though requires some adjustment in the electrolyte composition for optimal performance.     

Hydrodynamic voltammetry at the liquid|liquid interface: facilitated ion transfer and the rotating diffusion cell

A new approach to the voltammetric investigation of facilitated ion transfer processes is reported. The technique uses a rotating diffusion cell approach to induce laminar flow in the organic phase of a liquid|liquid electrochemical cell. The interface between two immiscible electrolyte solutions (ITIES) was stabilised against rotation with either γ-alumina or a track-etched polyester membrane. The resultant voltammetry is shown to be consistent with the Koutecký–Levich equation enabling kinetic parameters associated with facilitated transfer of sodium by dibenzo-18-crown-6 across the water|1,2-dichloroethane interface to be evaluated. In particular, the use of the more hydrophilic alumina membrane permits the uncertainties regarding the use of the membrane-stabilised ITIES, namely the interfacial position, to be eliminated.     

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.     

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.     

Theory of a reversible redox reaction in an ionic liquid that is coupled to an ion transfer across the aqueous electrolyte/ionic liquid interface

A theory is provided for a reversible electro-oxidation of a neutral redox probe dissolved in room-temperature ionic liquid, which is sandwiched between an electrode surface and an aqueous solution as a thin film. If the peak potentials in cyclic voltammetry depend on the bulk concentration of electrolyte in water, the oxidation is most probably coupled to the transfer of anions from water into ionic liquid; but if the peak potentials are independent of the electrolyte concentration, the transfers of anions from water into ionic liquid and cations from ionic liquid into water are equally probable. Dedicated to Professor Dr. Yakov I. Tur’yan on the occasion of his 85th birthday.     

中性载体ETH129推动金属离子在水/硝基苯界面的转移

本文用循环伏安法发现了中性载体ETH129(N, N, N', N'-四环己基-3-氧杂-戊二酰胺)在水/硝基苯界面推动H^+, Li^+, Na^+, Zn^2^+, Mg^2^+, Cu^2^+的离子转移,对推动离子转移过程的机理进行了探讨, 测定了相应离子的扩散系数和其配合物的稳定常数。     

磷钼钒杂多阴离子的液/液界面电化学研究

用循环伏安法研究了V^vMo11-V5^vMo7杂多阴离子在水/硝基苯界面的转移行为, 观察了溶液酸度对转移行为的影响及杂多阴离子稳定存在的pH范围, 钒取代的杂多阴离子稳定性较12-磷钼杂多酸显著提高, 但随钒原子数增加离子稳定性降低, 在"电位窗"内转移的离子主要为-4价, 转移过程为扩散控制, 由循环伏安实验得到了杂多阴离子的表观转移电位△0^wψ^0和转移自由能△Gtr^0^w^-^0,对于不同钒数的杂多阴离子, 其半波电位E1/2与pH关系均可用E1/2=A-37pH(mV)描述。     

中性载体ETH1117推动H+通过水/硝基苯界面传递的电化学研究

用循环伏安法研究中性载体ETH1117推动H⁺通过水/硝基苯界面的转移。通过络合使H⁺穿过水/硝基苯界面转移,是受扩散控制的可逆过程,ETH1117与H⁺在硝基苯相的配合比为1:1,配合物的稳定常数β₀为2.9×10⁷,扩散系数D为4.2×10^-6cm²/s。     

两种喹啉类药物在水/硝基苯界面循环伏安研究

本文用循环伏安法研究了盐酸喹啉和8-羟基喹啉配合质子在水/硝基苯界面的转移过程, 讨论了水相pH值对其转移行为的影响, 探讨了有关转移过程的机理, 测定并计算了有关热力学参数。