铁电极上硫脲及衍生物的缓蚀作用研究

用极化曲线方法测定了硫酸溶液中硫脲及其衍生物的浓度变化对铁腐蚀电化学行为的影响，获得了腐蚀电位下缓蚀剂对阴极和阳极过程的作用系数，用ＥＨＭＯ方法对硫脲及其衍生物的结构参数进行了量化计算，分析表明，缓蚀剂对阴极和阳极过程作用系数的大小与这些参量有密切关系。     

Study of Factors Affecting the Performance of Voltammetric Copper Sensors Based on Gly‐Gly‐His Modified Glassy Carbon and Gold Electrodes

This paper reports a study of the factors affecting the analytical performance of gold and glassy carbon electrodes modified with the tripeptide Gly‐Gly‐His for the detection of copper ions. Gly‐Gly‐His is attached to a glassy carbon (GC) surface modified with 4‐carboxyphenyl moieties or a gold surface modified with 3‐mercaptopropionic acid by the reaction of the N‐terminal amine group of the peptide with the carboxylic acid groups of the monolayer via carbodiimide activation. X‐ray photoelectron spectroscopy was used to characterize the steps in the biosensor fabrication. It was found that the analytical performance of a sensor prepared with Gly‐Gly‐His on a GC electrode was similar to that on a gold electrode under the same conditions. The performance was greatly enhanced at higher temperature, no added salt during copper accumulation and longer accumulation time within a pH range of 7–9. Interference studies and investigations of stability of the Gly‐Gly‐His sensor are reported. Analysis of natural water samples show that the sensors measure only copper ions that can complex at the sensor surface. Strongly complexed copper in natural water is not measured. Despite greater stability of diazonium salt derived monolayers on carbon surfaces compared with alkanethiols self‐assembled monolayers on gold, the stability of the sensors was essentially the same regardless of the modification procedure.     

纳米CoHCF修饰电极的制备及其对血红蛋白的电化学测定研究

A cobalt hexacyanoferrate （CoHCF） nanoparticle （size ca. 60 nm） chemically modified electrode （CME） was fabricated and the electrochemical behavior of hemoglobin （Hb） at this nanosized CoHCF CME was studied. In comparison with a bare glassy carbon electrode （GCE） and a general CoHCF CME electrodeposited in a traditional manner, the present nanosized CoHCF CME performed efficiently electrocatalytic reduction for Hb with relatively high sensitivity, stability, and longlife, Combined with liquid chromatography （LC）, the nanosized CoHCF CME was used as the electrochemical detector of Hb in the established flow injection analysis-electrochemical determination （FIA-ECD） system. The peak current was a linear function of concentrations in the range from 2.5×10^-8 to 5.0×10^-6mol/L for Hb, with detection limit of 1.4×10^-8 mol/L. The FIA-ECD system has been successfully applied to assess the Hb content of clinic blood samples with advantages of sensitiveness, speediness, easy control and small sample-consumption.     

Determination of dopamine in synthetic cerebrospinal fluid by SWV with a graphite–polyurethane composite electrode

This work describes an electroanalytical investigation of dopamine using cyclic voltammetry (CV) and the graphite–polyurethane composite electrode (GPU). In CV studies, well-defined redox peaks characterize the oxidation process at the GPU electrode, which is indicative of electrocatalytic effects associated with active sites on the GPU electrode surface. A new analytical methodology was developed using the GPU electrode and square wave voltammetry (SWV) in BR buffer solution (0.1 mol L^–1; pH 7.4). Analytical curves were constructed under optimized conditions (f=60s^–1, E_a=50 mV, E_I=2 mV) and detection and quantification limits of 6.4×10^–8 mol L^–1 (12.1 g L^–1) and 5.2×10^–6 mol L^–1 (0.9 mg L^–1), respectively, were achieved. The precision of the method was checked by performing ten successive measurements for a 9.9×10^–6 mol L^–1 dopamine solution. For intra-assay and inter-assay precisions, the relative standard deviations were 1.9 and 2.3%, respectively. In order to evaluate the developed methodology, the determination of dopamine was performed with good sensitivity and selectivity, without the interference of ascorbic acid in synthetic cerebrospinal fluid, which indicates that the new methodology enables reliable analysis of dopamine.     

碱性溶液中金电极上氧还原中间物研究

应用改进了的旋转全电极上的电势阶跃计时库仑法,分别测定了不同电极电势下氧还原过程中电极吸附中间物和溶解中间物氧化所需的电量,实验证明,在此过程中电极上确有吸附中间物存在,而且是电极电势的函数,但其分子属性尚需进一步鉴别。     

包覆Y(OH)3的球形Ni(OH)2的电化学性能

利用软嵌式粉末电极技术研究了Y(OH)3包覆对球形Ni(OH)2电化学性能的影响. 循环伏安结果表明, 在球形Ni(OH)2的氧化过程中存在Ni(Ⅲ)和Ni(Ⅳ)的两步氧化反应, 产生的Ni(Ⅳ)不稳定, 能分解产生NiOOH和氧气, 所以可将Ni(Ⅲ)→Ni(Ⅳ)看作副反应. Y(OH)3包覆层对Ni(OH)2氧化过程后期的副反应, 特别是Ni(Ⅲ)→Ni(Ⅳ)具有较好的抑制作用. 由包覆后的Ni(OH)2制成的模拟电池表现出很好的高温性能, 在1C充放电条件下, 当Y的摩尔分数为1.61%时, 在60 ℃时所对应的容量保持率可达到25 ℃的92.7％; 当Y的摩尔分数仅为0.55 %时, 在60 ℃时所对应的质量比容量也可达到241.3 mA·h/g.     

Mass transfer to horizontal gas-generating electrodes

Mass transfer to a horizontal electrode during electrolytic evolution of oxygen and hydrogen at current densities of 100 to 10 000 A/m² is studied. The mass transfer intensity is evaluated from the diffusion layer thickness, which varies from 60 to 5 μm at such current densities. Calculations show that the decrease in the diffusion layer thickness is due to bubbles with a stationary interphase surface crossing the diffusion layer. During the hydrogen evolution, the diffusion layer thickness is nearly the same for vertical and horizontal electrodes. During the oxygen evolution, the diffusion layer is much thinner for a horizontal electrode. Additional decrease of the diffusion layer thickness during the evolution of oxygen is associated with the lesser solution density in the near-electrode layer and with its transport away by means of natural convection.     

Anodic stripping voltammetry of sulphide at a nickel film: towards the development of a reagentless sensor

The determination of sulphide at an electrochemically generated nickel oxide layer at glassy carbon and screen-printed electrodes in acidic media has been examined and appraised. The NiO layer was found to produce a stripping-like signal to sulphide and gave a linear peak current response from 20 to 90 μM. The response was further enhanced by repetitive cycling allowing accumulation of nickel sulphide at the electrode surface such that lower micromolar levels of sulphide (i.e. 5 μM) can be determined. The response at the NiO layer to sulphide is shown to be reproducible over a period of 24 h, thereby offering the development of a disposable amperometric sensor for sulphide.     

Adsorption of the fluoride ion on the surface of various faces of a single crystal of silver: a quantum-chemical study

The fluoride ion adsorption from a gas phase on various faces of a single crystal of silver is studied by a density functional method within a cluster model for metal. The adsorption bond energy is found to increase in the series Ag(100) < Ag(111) < Ag(311) < Ag(110). A substantial structural and energetic heterogeneity of various adsorption sites is revealed. The results are utilized to simulate the electrochemical interface between individual faces of a single crystal of silver and aqueous solutions containing the fluoride ion. It is assumed that the adsorption potential may be represented as the sum of two contributions, one of which describes the metal–ion interaction and the other, the ion solvation energy. The plotted adsorption terms take into account partial degradation of the fluoride ion when adsorbed from an aqueous solution. Estimates of discreteness of the electrical double layer are presented. A conclusion on the maximum manifestation of specific adsorption of the fluoride ion for the Ag(100) face is made.Translated from Elektrokhimiya, Vol. 41, No. 2, 2005, pp. 232–238.Original Russian Text Copyright © 2005 by Nazmutdinov, Zinkicheva.This revised version was published online in April 2005 with corrections to the article note and article title and cover date.     

Development and optimization of a solid composite tyrosinase biosensor for phenol detection in flow injection systems

Bulk-modified epoxy-graphite tyrosinase biosensors were fabricated by four different procedures. The influence of these fabrication procedures on the analytical performance of the enzyme electrode in an amperometric wall-jet flow cell has been studied. The bioprobe performance is assessed by cyclic voltammetry. Higher current densities and narrower peaks were obtained when the enzyme was introduced in the dry state into the epoxy-graphite material, instead of introducing it previously dissolved in the buffer. In the F1 system responses of 11.79 μA cm⁻² and 1.43 μA cm⁻² are then obtained for catechol and phenol respectively for 50 μL injections of 20 μM solutions. Moreover, if gold/palladium is introduced into the epoxy-graphite, a further increase in current is achieved resulting in 27.70μA cm⁻² and 4.90μA cm⁻²for catechol and phenol, respectively. This biosensor can operate in aqueous as well as in mixed aqueous-organic environments.