超微电极上恒电位法苯胺的电化学聚合研究

本文对超微盘电极上苯胺的恒电位电化学聚合进行了研究，对聚合电流随时间的关系进行了详细的讨论，提出了径向聚合计时电流方程式并进行了验证，实验结果与理论相符。     

Electrochemistry of monoazahemin reconstituted myoglobin at an indium oxide electrode

Monoazahemin reconstituted myoglobin was prepared and its electrochemical behavior was studied in comparison with native myoglobin. For both myoglobins well-defined voltammograms were clearly obtained at highly hydrophilic surfaces of indium oxide electrodes. Although monoazahemin showed a more positive redox potential than hemin (measured in methanol), monoazahemin reconstituted myoglobin showed a more negative redox potential than native myoglobin in a 50 mM bis-Tris buffer solution (pH 6.5), suggesting that for both native and reconstituted myoglobins the heme environment including proximal histidine as an axial ligand of the redox center plays an important role in determining the redox potential. Also, a unique electrochemical response of cyano-monoazahemin reconstituted myoglobin was demonstrated.     

Electrochemical behavior of mesoionic sydnone derivatives at wax-impregnated carbon paste electrode

The-N=N-moiety in the mesoionic 3-phenyl sydnone and its derivatives like tolyl sydnones and anisyl sydnones undergo two-electron irreversible electrochemical reduction in Britton-Robinson (BR) buffer at wax-impregnated carbon paste electrodes. Infrared, nuclear magnetic resonance, and mass-spectral data, used to characterize the reduced product, confirm the proposed mechanism. The pasting liquid at the surface of the electrode is found to decrease the electron-transfer rate and cause a higher overpotential compared to homogeneous electrodes. The influence of variation of pH on the peak current and peak potentials is studied in the acidic range. The cathodic peak shifts to more negative potentials with increase in pH, indicating the involvement of proton in the reduction process. This could be a new method of preparation of 2,4-dihydro-3-substituted 1,2,3-oxadiazole-5-one. The substituent effect and the effect of variation of scan rate, concentration, and temperature on peak currents and peak potentials is discussed. The cathodic shift in various organic co-solvents (methanol, acetonitrile, DMF, DMSO) using BRB as the supporting electrolyte is examined. Published in Russian in Elektrokhimiya, 2006, Vol. 42; No. 7, pp. 862–868. The text was submitted by the authors in English.     

铝在氢氧化钠溶液中的电化学行为研究

铝是地壳中含量丰富的元素 ,分布广泛 ,由于其具有价格低、能量密度高、导电性良好及无毒性等优点 ,因而是阳极材料的首选物质 ,铝电池的研究也已经成为近年来研究开发的热点课题之一[1～ 3] 。探讨铝在强碱性溶液中的溶解机理 ,对铝电池的研究和开发将具有一定的理论指导意义。1　实验部分1 1　仪器与试剂ＢＡＳ 1 0 0Ａ电化学系统 (美国ＢＡＳ仪器公司 ) ;ＣＳ5 0 1型恒温槽 ;工作电极为直径是 0 .3ｍｍ的铂圆盘电极 ,参比电极是标准甘汞电极 (ＳＣＥ)。铝( 99.99% ) (天津化学试剂厂 ) ,氢氧化钠为分析纯(上海化学试剂厂 ) ,水为二次蒸…     

Redox equilibria in the In(III)-In(I)-In system in aqueous KBr solutions II. A rotating ring-disc electrode study

Summary The open-circuit behaviour of thick indium films formed onto gold by the electroreduction of In(III) has been investigated in acidified aqueous KBr solutions using the rotating ring-disc electrode technique. The spontaneous dissolution of indium metal immersed in the solution containing its own ions of higher valency yields In(I) ions. Information about the equilibrium and mechanism of the process studied was drawn from measurements of the limiting ring current and disc potential as a function of the electrode rotation rate. It was proved that the overall reaction 2In+In(III)3In(I) occurs as a coupling of two electrochemical steps: InIn(I)+e^–, and In(III)+2e^–In(I). The cathodic half-reaction is the rate-determining step, whereas the anodic half-reaction is reversible.

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Das Redox-Gleichgewicht im In(III)-In(I)-In-System in wäßrigen KBr-Lösungen, 2. Mitt. Untersuchungen mit der rotierenden Ring-Scheiben-Elektrode

Zusammenfassung Die spontane Auflösung von Indium unter der Wirkung von eigenen lonen (In(III)) wurde in sauren bromidhaltigen Lösungen mit Hilfe der rotierenden Ring-Scheiben-Elektrode untersucht. Die Angaben über das Gleichgewicht und den Mechanismus des untersuchten Prozesses wurden auf Grund der Abhängigkeit der Grenzströme an der Ring-Elektrode und der Elektrodepotentiale der Scheiben-Elektrode von der Umdrehungsgeschwindigkeit erreicht. Aus den Messungen folgt, daß die Bruttoreaktion 2In+In(III)3In(I) aus zwei überlagerten Durchtrittsreaktionen, InIn(I)+e^– und In(III)+2e^–In(I), besteht. Die kathodische Reaktion ist geschwindigkeitsbestimmend, während die anodische Teilreaktion reversibel abläuft.

     

金-石墨烯修饰电极电化学检测塑料瓶中双酚A

在离子液体碳糊电极(CILE)表面上采用一步电还原法制备了纳米金(nAu)-石墨烯(GR)复合膜修饰电极(nAu-GR/CILE).研究了双酚A(BPA)在nAu-GR/CILE上的电化学行为,BPA的电极反应过程为受吸附控制的不可逆过程;采用示差脉冲伏安法研究了BPA氧化峰电流和浓度之间的关系,在0.08～400.0...     

Mechanism and kinetics of the reduction of In(III) ions at a polycrystalline gold electrode from highly concentrated ZnCl2 solutions

Summary The mechanism of the cathodic reduction of In(III) at gold has been studied by rotating disc and ring-disc voltammetry in highly concentrated aqueous ZnCl₂ solutions. At concentration of the base electrolyte higher than 7 mol dm^–3, the voltammetric curves recorded at the disc electrode split into two well-separated waves which correspond to the successive charge transfer reactions: In(III) + 2e^– In(I) and In(I) + e^– In. By the use of coulometric and potentiometric techniques, the formal potentials of the In(III)/In(I), In(III)/In and In(I)/In redox couples as well as the equilibrium constants of the reproportionation reaction In(III) + 2 In 3 In(I) has been determined and discussed. The kinetic parameters of the In(III)/In(I) electrode reaction have been also evaluated and discussed.

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Mechanismus und Kinetik der Reduktion von In(III)-Ionen an der Goldelektrode in hochkonzentrierten wäßrigen ZnCl₂-Lösungen

Zusammenfassung Es wird der Mechanismus der Reduktion von In(III)-Ionen in hochkonzentrierten ZnCl₂ Lösungen mittels der Scheiben- und Ring-Scheiben-Elektrode aus Gold untersucht. Wenn die Konzentration des Grundelektrolyten 7 mol dm^–3 übersteigt, verteilen sich die erhaltenen Stromspannungskurven auf zwei gut gestaltete Stufen, die den konsekutiven Durchtrittsreaktionen In(III) + 2e^– In(I) und In(I) + e^– In entsprechen. Aufgrund der coulometrischen und potentiometrischen Messungen werden die Formal-Standardpotentiale der In(III)/In(I)-, In(III)/In-und In(I)/In-Redoxpaare, die Gleichgewichtskonstanten der Reproportionierungsreaktion In(III) + 2 In 3 In ermittelt. Die kinetischen Parameter der Durchtrittsreaktion In(III)/In(I) werden bestimmt und diskutiert.

     

Heat capacities of concentrated multicomponent aqueous electrolyte solutions at various temperatures

The specific heat capacities of the aqueous multicomponent system NaCl +KCl+MgCl₂+CaCl₂ with ionic strength between 8.3 and 9.6 (resembling Dead Sea waters) were measured between 15°C and 45°C. The obtained data were fitted to an empirical equation as a function of concentration and temperature. The thermodynamic functions of the studied multicomponent system were found to be strongly influenced by changes in MgCl₂ concentrations. The application of Young's rule to such concentrated systems was checked at 25°C. The calculated (by Young's rule) specific heat capacitiesC _p and apparent molar heat capacities C_p, of these multicomponent electrolyte solutions were in reasonable agreement with the measured values (–0.008 J-g^–1-K^–1 and –2.6 J-mol^–1-K^–1, respectively).     

阿霉素在钴离子注入修饰电极上的电化学行为及其应用

阿霉素在０．１ｍｏｌ／Ｌ ＨＡｃ－ＮａＡｃ（ｐＨ４．６２）缓冲溶液中用注入钴的修饰玻碳电极为工作电极进行伏安测定,得到一良好的还原峰;Ｅｐ＝－０．５２２Ｖ（ｖｓ．ＳＣＥ）。峰电流与阿霉素浓度在１．４×１０＾－６－１．４×１０＾－６ｍｏｌ／Ｌ和１．４×１０＾－６－５．６×１０＾－５ｍｏｌ／Ｌ范围内呈线性关系,。     

Voltammetric study of the behaviour of N-acetyl-p-aminophenol in aqueous solutions at a platinum electrode

The electrochemical oxidation of N-acetyl-p-aminophenol (PAR) was investigated at a Pt electrode with the application of cyclic (CV) and differential pulse (DPV) voltammetry methods. An effect of scan rate, substrate concentration and pH on electrode reactions was determined. The parameters of substrate electro-oxidation, i.e. heterogeneous rate constant, charge transfer coefficient, and diffusion coefficient, were calculated. Our investigation's results prove the exchange of two electrons and one proton in the first step, followed by a chemical reaction. PAR electro-oxidation occurs according to an EC mechanism.     

Charge-discharge behavior of K2FeO4 electrodes in concentrated KOH solutions

The charge-discharge behavior of the K₂FeO₄ electrodes with different current collectors is investigated by various electrochemical techniques. Due to higher electrochemical stability of platinum, the K₂FeO₄ electrode using platinum lattice as current collector displays better primary discharge performance than those with silver lattice and nickel foam as current collectors. The galvanostatic charge-discharge experiments indicate that the K₂FeO₄ electrodes have low electrochemical reversibility, which may result from their relatively lower oxygen evolution potentials or the effects of the oxidation/reduction of current collectors. The experimental results of intermittent discharge, cycle voltammetry, and XRD show that the discharge reaction of the K₂FeO₄ electrode may consist of two steps. Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 4, pp. 355–360. The text was submitted by the authors in English.     

Electrochemical behavior of dopamine at a quercetin-SAM-modified gold electrode and analytical application

A stable quercetin–thioglycolic acid-modified gold electrode (Qu–TCA/Au) was prepared as a self-assembled monolayer (SAM) and its electrochemical behavior was investigated by electrochemical methods. In 0.05-M phosphate buffer solution (pH 7.0) quercetin exhibits quasi-reversible signals at the Qu–TCA/Au electrode. The stability of the quercetin-modified gold electrode is very good. The quercetin self-assembled monolayer is an effective mediator for the oxidation of dopamine, which was investigated by cyclic voltammetry and differential pulse voltammetry. Ascorbic acid does not interfere with determination of dopamine at an electrode modified with a mixture of quercetin–thioglycolic acid and quercetin–11-mercaptoundecanoic acid. This modification allows dopamine to be determined in the presence of ascorbic acid in the range from 3×10^–5 to 3×10^–4 M. The detection limit is 1×10^–6 M. Scanning electrochemical microscopy (SECM) was employed to study the electrochemical performances of the modified gold electrode indicating different feedback modes at differently modified surfaces.     

对硝基苯酚在多壁碳纳米管修饰玻碳电极上的电化学行为及分析测定

水中对硝基苯酚主要来源于化工、制药行业,它有致癌作用。人们已对它的测定方法进行了大量的研究,最早采用的测定方法是分光光度法,其检测限偏高;色谱法测定对硝基苯酚,操作繁琐,仪器昂贵,分析成本高。后来又发展了一种操作更方便的直接用于测定的电化学方法。本文旨在利用碳纳米管对对硝基苯酚的吸附性能,研究对硝基苯酚在多壁碳纳米管修饰电极上的电化学行为。     

Study on the electroreduction of In(III) ions at gold from acidic bromide solutions by the rotating ring-disc electrode technique

The mechanism of the indium electrodeposition on gold from acidic KBr solutions has been investigated by means of the rotating ring-disc electrode technique. The measurements showed that the overall electrode reaction In(III) + 3 e In consists of two successive charge transfer steps, i.e. In(III) + 2 e In(I) and In(I) + e In, with soluble monovalent indium as an intermediate. The current efficiency for In(I) generation under steady-state conditions is 100% in the case of low disc current densities. The disproportionation of In(I) in the bulk of solution occurs in slightly acidified solutions,pH=2, in addition to the In(I) electrochemical reduction. Based on the ring current transients, it was established that the two-electron transfer step is preceded by the formation of a thin passive film of indium metal.

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Untersuchung der elektrochemischen Reduktion von In(III)-Ionen an Gold in sauren Bromidlösungen mit der rotierenden Ring-Scheiben-Elektrode

Zusammenfassung Mit Hilfe der rotierenden Ring-Scheiben-Elektrode wurde der Mechanismus der kathodischen Abscheidung von Indium auf Gold in sauren KBr-Lösungen untersucht. Aus den Messungen folgt, daß die Bruttoreaktion In(III) + 3e In über zwei aufeinanderfolgende Durchtrittsreaktionen, In(III) + 2 e In(I) und In(I) + e In, mit löslichem einwertigem Indium als Zwischenprodukt abläuft. Bei kleinen Stromdichten werden die In(I)-Ionen mit 100%iger Stromausbeute erzeugt. In schwächer sauren Lösungen (pH=2) konnte außer der elektrochemischen Reduktion von In(I) zusätzlich dessen Disproportionierung innerhalb der Lösung ermittelt werden. Auf Grund der Ringstrom-Zeit-Kurven wurde auch festgestellt, daß die Bildung von einer dünnen In-Metallschicht, die ein passives Verhalten aufweist, dem Zweielektronenübergang vorangegangen ist.

     

Electrochemical sensor of nitrite based on an inorganic film modified glassy carbon electrode

The electrocatalysis of nitrite in solutions at an inorganic film modified glassy carbon electrode was studied. The modifier was an electrodeposited thin inorganic film of the copper-heptacyanonitrosylferrate (CuHNF). Cyclic voltammetry of the modified electrode in a nitrite solution revealed that both oxidation and reduction of nitrite were catalyzed and the electrocatalytic currents were controlled by the diffusion of nitrite. Voltammetric and amperometric responses were investigated. When applied as an amperometric sensor in a flow injection system, the modified electrode permitted detection at — 0.55 V, over 500 mV lower than at the naked electrode surface. A linear response range extending from 1 × 10^–6 to 1 × 10^–3 M nitrite was obtained, with a detection limit of 3 × 10^–7 M. The relative standard deviation for 50 repetitive injections with a 5 × 10^–5 M nitrite solution was less than 4%. The procedure was applied to the determination of nitrite in saliva and nitrate.     

盐酸左氧氟沙星在聚L-精氨酸/多壁碳纳米管修饰电极上的电化学行为

运用循环伏安法、线性扫描伏安法、计时电量法等研究了盐酸左氧氟沙星在聚L-精氨酸/多壁碳纳米管修饰电极上的电化学行为。实验表明:盐酸左氧氟沙星在聚L-精氨酸/多壁碳纳米管修饰电极上的电极反应过程为等电子等质子吸附控制的不可逆过程,在pH=6.0的Na2HPO4-NaH2PO4支持电解质中,其氧化峰电流与浓度在7.0×10-6~1.0×10-4mol·L-1范围内呈良好的线性关系,相关系数R为-0.9992,检出限为5.0×10-6mol·L-1,样品测定回收率为98.26%~101.70%。     

头孢哌酮在玻碳电极上的电化学行为及检测方法

应用循环伏安法、线性扫描伏安法和微分脉冲伏安法研究头孢哌酮在玻碳电极上的电化学行为,建立了应用伏安法定量检测头孢哌酮的新方法。头孢哌酮的电极过程为受吸附控制的不可逆过程,电极反应转移电子数和转移质子数均为2。头孢哌酮在pH1.0的1mol/LH3PO4-NaOH介质中,在+0.13V(vs.Ag/AgCl)电位处产生一灵敏的氧化峰,应用微分脉冲伏安法进行测定,该峰电流值Ip与头孢哌酮质量浓度在5.05×10-7～1.01×10-4g/mL范围内有良好的线性关系(R=0.9996),检出限为4.95×10-9g/mL,样品测定平均加标回收率达99.50%,相对标准偏差(RSD)为3.17%。     

Influence of the cathodic polarization on the stability of Ti surface in concentrated KOH solutions

The stability of spontaneous thin layers and thin layers formed upon cathodical polarization of Ti in KOH solutions have been studied by potentiostatic and ellipsometric methods. At open circuit potential (OCP) the strongly adherent films, whose thickness depends on the concentration of the KOH solution, were formed. During the cathodic polarization the transformation of these films to weakly adsorbed precipitated layers on the electrode surface was observed. Comparing the theoretically computed curves with the experimental Ψ vs Δ loci measured ellipsometrically, the complex indices of refraction and the thickness of the generated films, from 3.6 to 60 nm in 1 M KOH and from 36 to 105 nm in 5 M KOH (adherent to the electrode surface), were determined. At OCP the rate of film growth increases with increasing the concentration of KOH solution. Cathodic polarizations change the chemical composition and retard the rate of film growth. Based on the ellipsometric and electrochemical data the chemical compositions of the formed films consisted of TiO₂, Ti₂O₃, TiO₂·H₂O, Ti(OH)₃ and TiOOH·nH₂O.     

对苯二酚在碳纳米管修饰玻碳电极的电化学行为及电化学动力学研究

碳纳米管(Carbon Nanotubes,CNT)自1991年发现以来,因其结构所具有的高比表面,高电导率,稳定的化学性质与超常的机械强度已成为世界范围内的研究热点,并应用于催化、气体储藏和电极材料等领域。用CNT修饰的电极具有良好的电化学性能并且已经取得了很好的实验结果[1],因此研究碳     

尿酸在聚亚甲基蓝修饰金电极上的电化学及电化学动力学性质

尿酸(Uric acid,UA)是人体内嘌呤核苷酸分解代谢过程中的最终产物.体液中尿酸的含量变化可以充分反映出人体新陈代谢、免疫等机能状况,同时也可间接反映出与嘌呤代谢的有关疾病[1].