掺锡三氧化二铟导电玻璃双工作电极薄层光透电化学池的设计

本文报道了ITO导电玻璃双工作电极薄层光透电化学池的设计。这种薄层池具有操作简便,成本低廉的特点,其突出优点在于工作电极的边际效应因采用辅助工作电极而得以明显消除。以Fe(CN)_6~(3-)/(4-)~考察了该池的电化学和光谱吸收响应特性。     

A study of the electron transfer and oxygen binding reactions of myoglobin

Quasi-reversible electron transfer kinetics are reported for sperm whale myoglobin reacting at tin-doped indium oxide electrodes. This reaction was studied by three different electrochemical methods; cyclic voltammetry (CV), single potential step chronoabsorptometry (SPS/CA) and derivative cyclic voltabsorptometry (DCVA). Kinetic parameters were determined from experiments which followed the purification of the protein, the pretreatment of the electrode surface and the removal of dioxygen from the sample solution. A formal heterogeneous electron transfer rate constant, k^0'. of 2.6 (±0.5) × 10⁻⁵ cm s⁻¹ and a transfer coefficient, α, of 0.48 (±0.05) were obtained using SPS/CA. These results are shown to correlate well with those obtained using a second spectroelectrochemical method, DCVA. Anodic and cathodic responses for the heterogeneous electron transfer of myoglobin can be observed using cyclic voltammetry, but these responses are not as reproducible as those that are obtained using the optical methods described here. The advantages of these optical methods over those of cyclic voltammetry are clear from this study.     

Time-derivative cyclic voltabsorptometry for voltammetric characterization of catechin film on a carbon-paste electrode: one voltammogram becomes four

Using (+)-catechin electrodeposited on a carbon-paste electrode as a model system, we have demonstrated the usefulness of the time-derivative cyclic voltabsorptometry for voltammetric characterization of the deposited films, in the case when not only the deposited species but also the same ones in free solution participated in redox processes. A long-optical-path thin-layer cell was used for the voltabsorptometric measurements. The potential-dependent absorption signals were monitored for catechin at 252 and 279 nm in B-R buffer electrolytes with pH = 1.8. The combination of voltabsorptometry with voltammetry enabled one measured cyclic voltammogram to become four, which were attributed to catechin and its oxidized state, in free solution or in deposited state, respectively. The surface coverage of the electrode was evaluated from the cyclic voltammograms obtained for the deposited catechin, which decreased with the increasing scan rate. Also, the deposited species was found to make a major contribution to the total voltammetric current, especially at higher scan rates.     

Study of the adsorption and oxidation of antioxidant rutin by cyclic voltammetry-voltabsorptometry

The adsorption and oxidation behavior of rutin was studied by in-situ UV spectroelectrochemistry in a long optical-path thin-layer electrochemical cell with a graphite-wax electrode. The dynamic UV spectra of rutin under potentiostatic oxidation were recorded, which indicated the formation of o-quinonic structure. During the repetitive cyclic potential scans, cyclic voltabsorptomogram was recorded at the three characteristic wavelengths 346, 254 and 296 nm, respectively. The profiles obtained showed two types of concentration fluctuation of species in solution, resulting from adsorption/desorption and redox reaction, respectively. Using derivative cyclic voltabsorptometry the contribution of the species in solution to the total current was estimated, and then the current of every step involved in the proposed redox mechanism was obtained for the first time. The result shows that rutin underwent a nearly reversible redox reaction in which the total current is mostly due to the contribution of adsorbed species. The present work developed cyclic voltabsorptometry into a useful tool for investigating redox process involving coupled adsorption/desorption steps.     

A thin-layer spectroelectrochemical study of 3,3'''',5,5''''-tetramethylbenzidine at SnO_2:F film optically transparent electrode

3,3',5,5'-tetramethylbenzidine (TMB) is a sensi-tive commonly-used substrate of the spectrophotomet-ric enzyme-linked immunosorbent assay (ELISA) as well as the electrochemical enzyme-linked immuno-assay[1,2]. It is more stable and of lower reagent blank than another sensitive commonly-used substrate, o-phenylenediamine. TMB is also the substrate of the most ELISA kits for clinical examination. The TMB- H2O2-horseradish peroxidase (HRP) voltammetric en-zyme immunoassay system has very…     

2-羟基-1,4-萘醌的电化学氧化还原机理研究

利用现场红外光谱电化学方法、 红外光谱循环伏吸法(CVA)和导数循环伏吸法(DCVA)研究了2-羟基-1,4-萘醌(2-HNQ)在乙腈溶剂中的电子转移机理. 在扫描范围为0.2~-1.8 V时, 2-HNQ的循环伏安(CV)图中有2对氧化还原峰. 在扫描范围为1.0~-2.0 V时, CV图在更正的电位下会出现1个氧化峰. 通过分析循环伏安扫描过程中1656, 1495, 1549和1325 cm^-1等峰的变化, 观察到整个电化学过程中存在2种中间状态, 去质子化醌(Q-O^-)还原生成的自由基二价阴离子会继续发生电化学反应, 即Q-O^-的还原遵循电化学-电化学反应机理(EE机理). 红外分析结果表明, 2-HNQ的电化学过程中存在较强的氢键作用.     

A thin-layer spectroelectrochemical study of 3,3′,5,5′-tetramethylbenzidine at SnO2:F film optically transparent electrode

The electrooxidation of 3,3′, 5,5′-tetramethylbenzidine (TMB) is dependent on the pH value of Britton-Robinson (B-R) buffer solution. In this work, the electrooxidation behavior of TMB was investigated with a SnO2:F film optically transparent thin-layer spectroelectrochemical cell. TMB underwent one two-electron electrooxidation process in the pH range from 2.0 to < 4.0, and two successive one-electron electrooxidation processes in the pH range from 4.0 to < 7.0 in the B-R buffer solution. At pH 6.5, the electrooxidative product of TMB generated a subsequent chemical reaction to yield an azo compound. Several spectroelectrochemical techniques, such as thin-layer cyclic voltammetry, thin-layer cyclic voltabsorptometry, thin-layer potential-controlled electrolysis absorptometry, thin-layer single-potential-step chronoabsorptometry, thin-layer double-potential-step chronoabsorptometry, thin-layer single-potential-step open-circuit relaxation chronoabsorptometry, were applied to this investigation. The formal potential E^0′ and the electron transfer number corresponding to the electrooxidation of TMB in B-R buffer solution, and the reaction rate constant of the subsequent chemical reaction were determined.     

对硝基苯酚在质子惰性溶剂中的氧化还原机理

利用现场红外光谱电化学法、红外光谱循环伏吸法(CVA)和导数循环伏吸法(DCVA)研究了对硝基苯酚(PNP)在乙腈中的氧化还原机理,并结合B3LYP方法在6-311++G*水平上计算得出反应中自由基阴离子和二聚体可能的结构.通过循环伏安曲线(CV)和快速扫描红外光谱验证了在电化学还原过程中PNP在乙腈溶剂中发生较复杂的自质子化反应,并且PNP的电化学行为受其浓度的影响.当PNP浓度较高时,PNP在还原成自由基阴离子后发生自质子化作用,然后自由基阴离子与质子化产物得到电子发生二聚反应,随后PNP阴离子还原成二价阴离子;当PNP浓度较低时,电化学还原机理会发生改变,二聚现象消失,阴离子自由基继续还原.     

LIGA-electrodes in voltammetric and spectroelectrochemical studies

The advantages of lithographic-galvanic (LIGA) fabricated microstructured honeycomb electrodes are demonstrated for spectroelectrochemical cells with respect to the response time (the time necessary to generate the product in a sufficient layer thickness close to the electrode to be detectable by UV-Vis-NIR spectroscopy) and to the conversion of the redox system in solution under thin-layer conditions. Transmission UV-Vis-NIR spectroscopy for several electrochemical applications can be performed in a special spectroelectrochemical cell based on the LIGA electrode and the two quartz rods, forming the walls of the cell and conducting the light beam through the cell. They are limiting the diffusion layer at the structured part of the working LIGA electrode. These microstructured LIGA-electrodes can be used as well defined models of porous electrodes at which redox processes occur under finite diffusion conditions. Such electrodes have been successfully used in the voltammetric and spectroelectrochemical study of various redox systems in both aqueous and non-aqueous solvents. The possibility to fabricate the well defined microstructures from various organic conducting polymers is demonstrated by the electrochemical deposition of polypyrrole in moulded LIGA-forms at high current densities in aqueous solutions.     

Spectroelectrochemical identity of Prussian blue films in various electrolytes: comparison of time-derivative voltabsorptometric responses with conventional cyclic voltammetry

Using Prussian blue (PB) electrodeposited on gold-covered foil as a model system, we have demonstrated the usefulness of the time-derivative measurements of absorbance versus potential (linear potential-scan voltabsorptometry) for spectroelectrochemical characterization of thin electrochromic films. The time-derivative signals were monitored for PB at 680 and 420 nm in potassium, sodium and lithium electrolytes. Information obtained from cyclic voltabsorptometry is equivalent or complementary to that from conventional cyclic voltammetry. In the case of PB films investigated in lithium electrolyte, the voltabsorptometric time-derivative peaks are better defined than the respective voltammetric peaks. The combination of voltabsorptometry with voltammetry enables molar absorptivity and/or film loading to be determined. Also, concentration changes of differently colored mixed-valence redox centers can be monitored as a function of applied potential. Received: 16 January 1997 / Accepted: 11 March 1997     

In-situ spectroelectrochemical evidences for the copolymerization of o-toluidine with diphenylamine-4-sulphonic acid by UV-visible spectroscopy.

In-situ spectroelectrochemical studies on the copolymerization of o-toluidine (OT) with diphenylamine-4-sulfonic acid (DPASA) were carried out on ITO electrode in 0.5 M H2SO4 for different feed ratios of OT and DPASA. The early stages of copolymerization of OT with DPASA have been identified through spectroelectrochemical techniques. The results revealed the formation of a head-to-tail dimer type of intermediate at the initial stages of copolymerization. This N-phenyl-paraphenylene diamine (PPD) type of intermediate was assigned to have a peak at 550 nm in UV-visible spectra and confirmed via derivative cyclic voltabsorptogram (DCVA). Constant potential electropolymerization results also supported the formation of intermediate with an absorption maximum at 550 nm.     

Fabrication and electrochemical characterization of interdigitated nanoelectrode arrays

Interdigitated nanoelectrode arrays with controlled electrode bandwidth and gap geometries ranging from 30 nm to 1 μm were fabricated on glass substrates by a planar process involving high resolution electron beam lithography and lift-off, and their characteristic electrochemical responses to an aqueous ferrocene derivative solution were examined using fundamental electrochemical techniques. Despite the comparatively large electrode area of electrode arrays containing 10 bands to a single band electrode, quasi-steady-state currents with high current density were obtained at a slow potential sweep rate in cyclic voltammograms of ferrocene derivative since the lateral dimension of the nanoelectrode arrays was considerably less than the scale of the diffusion layer of redox species. Additionally, it was demonstrated that the electrode thickness influenced limiting currents of voltammograms in the case of nanoelectrode arrays. In generation-collection mode experiments, furthermore, a collection efficiency as high as ∼99% was attained by 100 nm wide electrode arrays with a gap dimension of 30 nm.     

大黄素的电化学氧化还原机理研究

本文利用循环伏安法(CV)、红外光谱循环伏吸法(CVA)和导数循环伏吸法(DCVA)研究大黄素(Q)在乙腈溶剂中的电子转移机理.Q的还原过程中阴离子自由基Q^?-会结合中性分子Q生成二聚物Q₂^?-.Q₂^?-在更负的电位下进一步还原为Q₂^2-.当扫描范围为-0.2 ~ -2.0 V时,经过一个循环伏安过程,在扫描结束物质并没有回到反应物Q,而是Q₂^2-. Q₂^2-会继续发生电化学反应,经历两步一电子过程,分别生成Q₂^3-. 和Q₂^4-.,对应CV图中峰C₃和C₄.当扫描范围扩大至1.0~-2.0 V时,在更正的电位下,观察到两个新的氧化峰A₁和A₂,该范围内的三圈扫描结果表明,在扫描结束物质重新氧化回到Q.当扫描范围缩小至0.3 ~ -1.4 V,A2峰随着扫描圈数的增加而增大,与A2峰对应的氧化产物Q₂^?-在溶液中不断积累.A1峰对应于Q₂^?-氧化回到Q.     

Solution infrared spectroelectrochemistry: A review

Infrared (IR) spectroelectrochemical techniques have seen extensive use in studies of electrode surface processes. They have also been employed, albeit less frequently, to investigations of redox species dissolved in solution. The application of IR spectroscopy to electrochemical solution processes represents a special challenge, for absorption of IR radiation by the solvent is a significant interference to detection of vibrational modes of dissolved analytes. It is also difficult to maintain potentiostatic control of the system in specially designed thin-layer spectroelectrochemical cells. Solution IR spectroelectrochemical experiments are important for investigations of redox systems in which it is desired to spectroscopically monitor the structures of dissolved products, intermediates and reactants involved in electrode reactions. Such experiments have been conducted on biochemical, inorganic, organic, and other systems. In this paper some examples of applications of IR spectroelectrochemical studies of solution species in the above areas are presented, and experimental aspects are discussed.     

Electrochemical Impedance Spectroscopic Analysis on the Electrochemical Deposition of Lead Dioxide in Acidic Medium

Electrochemical deposition of pure lead dioxides and modified lead dioxides incorporated with As(V) on a gold electrode was investigated by cyclic voltammetric, in-situ electrochemical impedance spectroscopic, and reflective UV-vis spectroelectrochemical techniques. The focus was given to analyze electrochemical impedance spectroscopic data obtained under various deposition conditions, i.e.,different deposition potentials.     

In situ UV-visible spectroelectrochemical evidences for conducting copolymer formation between diphenylamine and m-methoxyaniline

Electrochemical copolymerization of diphenylamine (DPA) with m-methoxy aniline (MA) was carried out in 4 M H(2)SO(4) by cyclic voltammetry (CV). Cyclic voltammograms (CVs) of the copolymer films were recorded in monomer-free background electrolyte. In situ sepectroelectrochemical studies were carried out on an optically transparent electrode (Indium tin oxide (ITO) coated glass) in 4 M H(2)SO(4) for different feed ratios of the comonomers. Constant potential and potential sweep methods were employed for performing polymerization. UV-visible absorption spectra were collected continuously and concurrently during the copolymerization in both the cases. The results from constant potential electropolymerisation indicated the formation of an intermediate with an absorption peak at 576 nm. Derivative cyclic voltabsorptogram (DCVA) was deduced from the results of cyclic spectrovoltammetry. The DCVA derived at 576 nm confirms the intermediates formed during the electrochemical copolymerization. The compositional changes of the two monomers in the copolymers with changes in feed composition of two monomers as predicted from in situ spectro electrochemical studies are evident from elemental analysis. A plausible copolymerization mechanism is suggested.     

The electrochemical and spectroelectrochemical behaviors of SOD at cysteine modified gold electrode.

Different promoters were used to enhance the rate of the electron transfer process of superoxide dismutase (SOD). A quasi-reversible cyclic voltammogram (CV) of SOD was observed on the cysteine-modified gold wire electrode. The coupled adsorption/desorption processes and the characteristic Raman spectra of different states of SOD molecules on the electrode surface were studied with electrochemical quartz crystal microbalance (EQCM) and in-situ Raman spectroelectrochemical techniques. The possible promotion mechanism was discussed.     

阳离子艳蓝的薄层光谱电化学研究

用薄层光谱电化学技术研究了阳离子艳蓝的电还原过程。薄层循环伏安图表明阳离子艳蓝有一对接近可逆的氧化还原峰。从光谱发现它有顺反异构体互变现象与变色效应。在氧存在时，循环伏安图和光谱图上均出现新峰，推测阳离艳蓝分子与氧分子能形成电荷转移络合物。测得阳离艳蓝电还原的式电极电势，电子转移数以及扩散系数等参数。并讨论了可能的电极过程。     

新式夹心型光透薄层光谱电化学电解池

本文设计了一种新式夹心型光透薄层紫外-可见光谱电化学池。该池采用铂网工作电极,两侧平行放置铂片为对极置于同一石英窗口夹层中,同时以聚四氟乙烯隔离膜作为边际限制器,结合池内小孔道设置内参比点进行精确的电位控制,具有理想的光谱电化学响应。利用循环伏安、循环电位-吸收、恒电位现场光谱、双电位跃-计时电量、双电位跃-计时吸收等技术,对铁氰化钾在氯化钾溶液中的行为进行了表征。     

Modular solid-state unit for electrochemical studies

A relatively inexpensive unit based upon solid-state operational amplifiers is described; its modular design makes it an extremely versatile instrument for many electrochemical techniques, e.g., normal direct current polarography and linear sweep voltammetry, cyclic voltammetry, alternating current polarography, and coulometry and electrolysis at controlled electrode potential. It can be readily adapted to many other functions.