硝基苯在铜电极上的电还原特性研究

应用循环伏安法和线性扫描伏安法研究水溶液中硝基苯在铜电极上的电还原特性及其电还原为苯胺的中间步骤和反应机理.结果表明:铜电极上硝基苯的还原电位在-0.58V和-1.32V左右(vs.SCE),溶液的酸性和碱性均有益于该还原反应的发生;还原过程伴有反应物吸附现象,当硝基苯浓度较大时,还原过程受传质过程控制;随着厌氧程度的提高,还原速率加快.     

Electrochemical Detection of Three Monohydroxylated Polycyclic Aromatic Hydrocarbons Using Electroreduced Graphene Oxide Modified Screen‐printed Electrode

An electrochemical sensor for detection of three monohydroxylated polycyclic aromatic hydrocarbons (OH?PAHs) was fabricated by electrochemical reduction of graphene oxide (E‐rGO) on screen‐printed electrode (SPE). The E‐rGO film presents typical wrinkled structure with porous and cavity‐like nanostructure, providing large surface area, effective π‐electron system and high electrical conductivity. The developed E‐rGO/SPE sensor exhibits outstanding sensing performance for the target OH?PAHs, 2‐hydroxynaphthalene, 3‐hydroxyphenanthrene, and 1‐hydroxypyrene, within a linear range varying from 50–800 nM, 50–1150 nM, and 100–1000 nM, and with a limit of detection (LOD) of 10.1 nM, 15.3 nM, and 20.4 nM (S/N=3), respectively. The electrochemical sensor possesses excellent stability, acceptable reproducibility, and good anti‐interference ability. Additionally, the proposed sensor can be applied to the analysis of OH?PAHs in the urine samples with recoveries of 98.1–105.9 %.     

酸性溶液中硝基苯在WC电极上的电化学还原

以聚四氟乙烯为粘接剂制成碳化钨(WC)电极.采用循环伏安法、线性扫描法和恒电位阶跃法研究了硝基苯在酸性溶液中WC电极上的电化学行为.实验表明:WC电极对硝基苯的还原具有较好的活性,电极过程受扩散和电化学步骤混合控制;表观活化能为23.7kJ·mol 1,其中,电化学步骤的活化能10.91kJ·mol 1.     

Cathodic Electrochemical Detection of Nitrophenols at a Bismuth Film Electrode for Use in Flow Analysis

The bismuth film electrode (BiFE) is presented for use in both batch voltammetric and flow injection (FI) amperometric detection of some nitrophenols (2‐nitrophenol, 2‐NP; 4‐nitrophenol, 4‐NP; 2,4‐dinitrophenol, 2,4‐DNP). The bismuth film was deposited ex situ (batch measurements) and in‐line (FI) onto a glassy carbon substrate electrode. Batch analysis of the nitrophenols was carried out in 0.04 M Britton Robinson (BR) buffer pH 4, while for FI measurements, a carrier/electrolyte solution composed of 0.1 M BR buffer pH 4 mixed with methanol (20+80, v/v%) was employed to resemble media used in preconcentration/clean‐up and flow separation sample pretreatment procedures. Under batch conditions, the voltammetric behavior of the nitrophenols was examined for dependence on medium pH in the range of 2 to 10. Employing the square‐wave voltammetry mode, the limits of detection were 0.4 μg L^?1, 1.4 μg L^?1, and 3.3 μg L^?1 for 2‐NP, 4‐NP, and 2,4‐DNP, respectively. Under flow conditions, a simple in‐line electrochemical bismuth film renewal procedure was tested and shown to provide very good inter‐ and intra‐electrode reproducibility of the current signals at low μg L^?1 analyte concentrations. The limits of detection for 2‐NP, 4‐NP and 2,4‐DNP obtained using FI and amperometric detection at ?1.0 V (vs. Ag/AgCl) were 0.3 μg L^?1, 0.6 μg L^?1 and 0.7 μg L^?1, respectively, with linear ranges extending up to 20 μg L^?1. The attractive performance of the BiFE under flow analysis conditions offers great promise with respect to its detection capability and to its use for a prolonged period of time with no need for inconvenient removal of the electrode from the system for mechanical surface treatment.     

Cu/C-Nafion复合电极上硝基苯的电化学还原

制备性电解的结果表明，硝基苯在Cu／C－Nafion膜复合电极上的还原产物只有苯胺，可能与电极／Nafion界面的弱酸性环境和其还原中间产物本羟胺在界面的扩散较仅有关．生成苯胺的电流效率随电流密度的增大而减小，随反应液中硝基苯浓度的增大出现一个最大值．这可能是硝基苯的电化学还原过程受某种粒子的扩散控制、峰电流取决于硝基苯在Nafion膜中的溶解度所致．     

Sn/Cu电极电化学还原CO2的研究

采用电沉积法制备Sn/Cu电极,由SEM观察并研究了电沉积电流密度对电极形貌的影响.在碱性三电极体系中考察了Sn/Cu电极对析氢、CO2还原的影响.发现10 mA.cm-2和15 mA.cm-2电沉积电流密度下制得的电极活性较高,尤以15 mA.cm-2时电极性能更佳,并指出了电还原CO2关键材料的结构特性.     

Electrochemical Determination of the Anticancer Herbal Drug Shikonin at a Nanostructured Poly(hydroxymethylated‐3,4‐ethylenedioxythiophene) Modified Electrode

A simple and sensitive method is described for the electrochemical determination of shikonin, a widely used anti‐tumoral agent, based on its electrochemical oxidation at a nanostructured poly(hydroxymethylated‐3,4‐ethylenedioxy‐thiophene) (PEDOT‐MeOH) electrode, which was fabricated by a facile electropolymerization method. Compared with bare and poly(3,4‐ethylenedioxythiophene) (PEDOT) electrodes, the PEDOT‐MeOH film exhibited a distinctly higher activity for the electrooxidation of shikonin. The PEDOT‐MeOH electrode showed a wide linear response for shikonin in the concentration range from 1.0 nM to 10.0 µM with detection limit of 0.3 nM. Furthermore, the PEDOT‐MeOH electrode displayed high stability, good reproducibility and high sensitivity for the detection of shikonin.     

Electrochemical Reduction of Oxygen on Multi-walled Carbon Nanotubes Electrode in Alkaline Solution

The multi-walled carbon nanotubes (MWNTs) electrode was constructed using polytetrafluoroethylene as binder, and the electrochemical reductive behavior of oxygen in alkaline solution was first examined on this electrode. Compared with other carbon materials, MWNTs show higher electrocatalytic activity, and the reversibility of O2 reduction reaction is greatly improved. The experiments reveal that the electrochemical reduction of O2 to HO2 is controlled by adsorption. The preliminary results illustrate the potential application of MWNTs in fuel cells.     

贮氢合金电极在葡萄糖电化学还原中的应用(英文)

以贮氢合金电极作催化还原电极,恒电位电解葡萄糖,发现合金经表面处理及电极的活化后,即可提高电流效率,在最优条件下,电解葡萄糖制山梨醇电流效率高达90%,葡萄糖转化率达80%以上.测试了电极的使用寿命,同时对电极中毒及再生方法进行了探讨.     

Electrochemical Reduction and Voltammetric Determination of Metronidazole Benzoate at Modified Carbon Paste Electrode

Abstract

A metalloporphyrin incorporated carbon paste sensor has been developed for the determination of metronidazole benzoate (MTZB). Zn(II) complex of 5,10,15,20-tetrakis (3-methoxy-4-hydroxy phenyl) porphyrin (TMHPP) was used as the active material. The MTZB gave a well-defined reduction peak at?0.713 V in 0.1 mol l^?1 phosphate buffer solution of pH around 7. Compared with bare carbon paste electrode (CPE), the TMHPP Zn(II) modified electrode significantly enhanced the reduction peak current of MTZB as well as lowered its reduction potential. Under optimum conditions the reduction peak current was proportional to MTZB concentration over the range 1 × 10^?3 mol l^?1 to 1 × 10^?5 mol l^?1. The detection limit was found to be 4.36 × 10^?6 mol l^?1. This sensor has been successfully applied for the determination of MTZB in pharmaceutical formulations and urine samples.     

Electrochemical Detection of Steroid Hormones Using a Nickel‐Modified Glassy Carbon Electrode

This paper demonstrates the development of an analytical method for detecting steroid hormones by coupling HPLC to electrochemical detection, using a nickel‐modified glassy carbon electrode. The method was evaluated in terms of sensitivity, linear dynamic range, limit of detection, and response stability. The developed method exhibited good figures of merit for the steroid hormones studied with no evidence of electrode fouling. As an example, the limit of detection (S/N=3) for E3 was 0.10 µM and the response precision (n=5) was 0.6 %. The application of the method for the analysis of a real river water sample is demonstrated.     

镍离子注入修饰电极上米托蒽醌与DNA相互作用的电化学研究

研究了在镍离子注入修饰电极和0.05mol/LTris-0.5mol/LNaCl缓冲溶液(pH=7.1)中,米托蒽醌(MX)与DNA作用的电化学.在37℃恒温1.5h条件下,MX与DNA形成一种非电活性的结合物,使MX峰电流降低,其结合比n(MX):n(DNA)=2:1,结合常数为1.61×10¹²,电子转移系数为0.41,电极反应速率常数0.33s^-1.加入DNA后,MX峰电流降低,据此,可以测定DNA.     

桑色素在L-半胱氨酸自组装膜修饰金电极上的电化学行为研究

在0.1mol/L(pH=4.7)的HAc NaAc缓冲溶液中,用L 半胱氨酸自组装膜修饰金电极对桑色素的电化学行为进行了初步的研究,考察了修饰时间、富集时间、富集电位、扫描速度、表面活性剂、金属离子等因素对其电化学行为的影响。研究发现,桑色素在0.44V(vs.SCE)左右产生一不可逆的氧化峰。该氧化峰电流与桑色素浓度在5×10-6～2×10-4mol/L范围内呈线性关系(相关系数r=0.9989),检出限为2×10-6mol/L,这比用裸金电极测试降低一个数量级。同时发现,十六烷基三甲基溴化铵(CTAB)对氧化峰电流有一定的增敏作用。该峰且随Pb2+浓度增大而线性增高,因此可用于Pb2+的测定。     

A Simple Electrochemical Approach Based on Inexpensive Wall‐Jet Screen‐Printed Ring Disk Electrode to Evaluate Oxygen Reduction Catalysts

A simple electrochemical approach to evaluate oxygen reduction catalysts using an inexpensive screen‐printed ring disk carbon electrode system, consisting of a ring electrode deposited with MnO₂ and a disk electrode modified with the catalysts for study, is developed in this study. The as‐prepared MnO₂ is selective and sensitive for H₂O₂ oxidation in the presence of O₂ and is crucial to the proposed approach. By coupling with a wall‐jet electrochemical cell, the product generated from the reduction reaction at the disk electrode can effectively be monitored at the MnO₂‐deposited ring electrode. Model catalysts of nano‐Au and nano‐Pd representing 2e^? reduction of O₂ to H₂O₂ and 4e^? reduction to H₂O, respectively, were evaluated as electrode materials in oxygen reduction reaction to demonstrate the applicability of the proposed method.     

Sensitive Electrochemical Detection of Horseradish Peroxidase at Disposable Screen‐Printed Carbon Electrode

A rapid, simple and sensitive electrochemical assay of horseradish peroxidase (HRP) performed on disposable screen‐printed carbon electrode was developed. HRP activities were monitored by square‐wave voltammetric (SWV) measuring the electroactive enzymatic product in the presence of o‐aminophenol and hydrogen peroxide substrate solution. SWV analysis demonstrated a greater sensitivity and shorter analysis time than the widely used amperometric and differential‐pulsed voltammetric methods. The voltammetric characteristics of substrate and enzymatic product as well as the parameters of SWV analysis were optimized. Under optimized conditions, a linear response for HRP from 0.003 to 0.1 U/mL and a detection limit of 0.002 U/mL (1.25×10^?15 mol in 25 μL) were obtained with a good precision (RSD=8%; n=6). This rapid and sensitive HRP assay with microliter‐assay volume could be readily integrated to portable devices and point‐of‐care (POC) diagnosis applications.     

TiO_2纳米管电极上电化学还原CO_2生成CH_3OH

采用原位阳极氧化-煅烧法制备TiO_2纳米管(TiO_2NTs)电极,运用X射线衍射(XRD)、电场发射扫描电子显微镜(FESEM)、X射线光电子能谱(XPS)、双电位阶跃测试等对制备电极进行表征,考察了其在0.1mol?L~(-1) KHCO_3水溶液中电化学还原CO_2的催化活性。结果表明TiO_2NTs电极上电化学还原CO_2的主产物为CH_3OH,CH_3OH由HCOOH和HCHO进一步还原而来。电极制备的最佳煅烧温度为450℃(TiO_2NTs-450),电解电位-0.56 V(vs RHE(可逆氢电极))时反应120 min后,生成CH_3OH的法拉第效率和分电流密度分别为85.8%和0.2 m A?cm~(-2)。与550和650℃煅烧的电极相比,TiO_2NTs-450电极具有更高的催化活性,归因于电极表面更多的三价钛活性位,有利于CO_2吸附,从而对·CO_2-起到稳定的作用,速率控制步骤转变为·CO_2-的质子化反应。     

四磺酸酞菁铜—DDAB表面活性剂薄膜电极对卤代乙酸的电化学催化

四磺酸酞菁铜阴离子（ＣｕＰｃＴｓ＾４－）在水溶液中可借助离子交换进入阳离子表面活性剂双十二烷基二甲基溴化铵（ＤＤＡＢ）薄膜电极，从而形成ＣｕＰｃＴＳ＾４－－ＤＤＡＢ薄膜电极，循环伏安实验表明，在ＫＢｒ溶液中，该薄膜电极有一对良好的还原氧化峰，阴阳极峤电位分别为－０．７８Ｖ和－０．６５Ｖ（ｖｓ．ＳＣＥ）．探讨了该薄膜电极的电化学行为，特别是对其各种卤代乙酸的电化学催化，对其机理进行了推测。     

Electrochemical Detection of Methimazole by Capillary Electrophoresis at a Carbon Fiber Microdisk Electrode

We developed a sensitive, simple and low cost method to determine methimazole based on capillary electrophoresis with electrochemical detection (CE‐EC) at a carbon fiber microdisk electrode (CFE). We investigated the effects of detection potential, the concentration and pH value of the phosphate buffer, and injection time as well as separation voltage on the detection of methimazole. Under the optimized conditions: the detection potential at 1.30 V, 10 mmol/L phosphate buffer (pH 7.0), injection time 30 s at a height of 20 centimeter and separation voltage at 15 kV, the linear range was obtained from 1.0×10^?7 to 2.0×10^?4 mol/L, covering 3 orders of magnitude with a correlation coefficient of 0.9995. The LOD (S/N=3) obtained was 5.0×10^?8 mol/L. The RSD of migration time and peak current for 2.0×10^?4 mol/L methimazole was 1.04% and 1.54% (n=10), respectively. The method was also used to analyze methimazole tablets and human urine sample.     

Electrocatalytic Reduction and Determination of Dissolved Oxygen at a Preanodized Screen‐Printed Carbon Electrode Modified with Palladium Nanoparticles

Efficient and stable electrocatalytic activity for the reduction of O₂ at activated screen‐printed carbon electrodes modified with palladium nanoparticles (SPE*‐Pd) was demonstrated in this study. X‐ray photoelectron spectroscopy confirmed the formation of >C?O functional group on electrode surface during the preanodization procedure at 2.0 V (vs. Ag/AgCl). The existence of chloride moieties was also identified possibly from the organic binder of carbon ink used in SPE fabrication. Both >C?O and chloride functional groups were essential for the excellent stability of the SPE*‐Pd. Electrochemical impedance spectroscopy verified the enhanced kinetic rate of oxygen reduction reaction at the as‐prepared Pd nanoparticles. The SPE*‐Pd showed ca. 250 mV positive shift in peak potential together with twice increase in peak current compared to those observed at a SPE‐Pt. The calibration plot was linear up to 8 ppm of DO with sensitivity and regression coefficient of 4.49 μA/ppm and 0.9936, respectively. The variation coefficient of i_pc for 7 DO determinations with O₂‐saturated pH 7.4 PBS was 2.1%. Real sample assays for ground and tap waters gave consistent values to those measured by a commercial dissolved oxygen meter.     

Electrochemical reduction of nitrate using various anodes and a Cu/Zn cathode

Electrochemical reduction of nitrate was studied using a Cu/Zn cathode and Ti/Pt, Ti/IrO₂–Pt and Ti/RuO₂–Pt anodes in an undivided and unbuffered cell. A novel condition for performing both cathodic reduction of nitrate and anodic oxidation of the ammonia and nitrite by-products was achieved using Ti/Pt and Ti/IrO₂–Pt anodes in the presence of NaCl, especially with Ti/IrO₂–Pt anode. Nitrate could be completely removed using the Ti/IrO₂–Pt and Ti/Pt anode, with neither ammonia nor nitrite detected in the treated solution. A low nitrate reduction rate was observed when using a Ti/RuO₂–Pt anode in the presence of NaCl. However, in the absence of NaCl, all anodes showed good performance for nitrate reduction, with the Ti/Pt anode having the highest selectivity for reducing nitrate to nitrogen.