Fabrication of Pt nanoparticles-decorated CVD diamond electrode for biosensor applications

An electrochemical biosensor was developed using boron-doped diamond (BDD) as an electrode material. To enhance the electrical performance of the electrode, the BDD electrode was decorated with Pt-nanoparticles (Pt-NPs) by electrochemical deposition. Their morphology according to the applied potentials for the synthesis of Pt-NPs was characterized by SEM. To identify the performance of the electrode modified with Pt-NPs, glucose detection was used as a sample sensing process, and the results were compared with those of a gold electrode and a bare BDD electrode. The electrochemical characteristics of the modified electrode were examined by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The BDD electrode with the Pt-NPs showed higher sensitivity and a lower detection limit than the Au electrode and BDD electrode. The proposed biosensor based on the Pt-NPs decorated BDD electrode showed high sensitivity, a low detection limit, fast direct electron transfer and good stability.     

A study of electrodes used in controlled-potential electrolysis of metal ions

Various electrodes used in controlled-potential electrolysis of metal ions are discussed: (1) a double-junction saturated calomel reference electrode with sodium formate as bridge electrolyte; (2) an auxiliary electrode made by winding platinum wire on a Teflon cylinder; (3) a working electrode made of tantalum gauze. The advantages of the tantalum electrode over a platinum electrode are that the hydrogen overpotential is higher, and the tantalum electrode need not be precoated with copper before deposition of metals such as Bi, Zn and Sn, which tend to form alloys with platinum. The electrode needs pretreatment before use, but this takes only 4 min or less.     

The mechanism of the electrogenerated chemiluminescence of luminol in aqueous alkaline solution

The mechanism of the electrogenerated chemiluminescence of luminol in aqueous alkaline solution based on the rotating ring—disc electrode system is discussed. The disc electrode is maintained at a negative potential and the ring electrode at a symmetrically changing double-step potential. Hydrogen peroxide generated at the disc electrode by the reduction of oxygen is immediately transported to the ring electrode because of electrode rotation. Hydrogen peroxide and luminol are oxidized at the ring electrode during the positive pulse of the double-step potential. These oxidation processes generate a superoxide radical and a luminol radical as intermediates. The luminol radical reacts with the superoxide radical (or oxygen) emitting light.     

Design of a Fluoride-Selective Electrode with Internal Contact Based on a Cu(II) Ion-Selective Electrode

The design of an electrode body that provides internal contact with a LaF₃ membrane based on a Cu(II) ion-selective electrode is described. The assembled fluoride electrode was examined in terms of potential-concentration curves and potential-time response. The behavior of the fluoride ion-selective electrode with the investigated internal contact was in good agreement with the commercial fluoride electrode.     

Fe修饰多壁碳纳米管电极高效产H2O2

为提高电芬顿(Electro-Fenton)体系H2O2的产率, 制备了多壁碳纳米管(MWNT)电极, 并与石墨/气体扩散(GDC)电极进行了比较. 结果表明, MWNT电极H2O2产率高于GDC电极. 采用电沉积方法, 制备了Fe修饰MWNT(Fe-MWNT)电极, 发现Fe对MWNT电极的修饰不仅可以提高体系的H2O2产率, 而且电流效率可以提高8%左右, 与GDC电极的电流效率接近. Fe-MWNT电极有望成为一种新型的阴极材料应用于Electro-Fenton体系中.     

Immobilization of glucose oxidase on carbon paper electrodes modified with conducting polymer and its application to a glucose fuel cell

A carbon paper electrode was modified with the conducting copolymer of 3-methylthiopene and thiophene-3-acetic acid prepared electrochemically on the electrode, and an enzyme electrode was fabricated by covalent immobilization of glucose oxidase on the modified electrode. The modification with the conducting copolymer increased the surface area of the electrode and the amount of the immobilized enzyme. As a result, the enzyme electrode showed a high catalytic activity. Moreover, it was found that the increased surface area led to a high rate of electron transfer reaction between the electrode and p-benzoquinone employed as an electron mediator. The enzyme electrode fabricated with the modified carbon paper gave a larger glucose oxidation current than that fabricated with the bare one. In addition, the glucose oxidation current was found to increase with increasing content of the conducting copolymer in the modified carbon paper. Corresponding to the large glucose oxidation current, high performance was confirmed for the glucose fuel cell constructed with the enzyme electrode based on the modified carbon paper.     

The determination of copper,lead and cadmium in sea water by differential pulse anodic stripping voltammetry

The effect of various instrumental parameters is investigated and optimized conditions established. The results are in accordance with the theory of differential pulse anodic stripping voltammetry. Both a hanging mercury drop electrode, and a rotating glassy carbon electrode mercury plated in situ were used. The best detection limit is obtained with the mercury film electrode, but the hanging mercury drop electrode is more reproducible. The differential pulse stripping technique is compared to linear sweep stripping, and increased sensitivity and better peak separation is demonstrated for the former technique, particularly when a hanging mercury drop electrode is used. However, the differential pulse technique will also improve the detection limit for a mercury film electrode, if the electrode has a non-ideal response with a corresponding high background current.     

Abrasive immobilization of carbon nanotubes on a basal plane pyrolytic graphite electrode: application to the detection of epinephrine

The performance of a basal plane pyrolytic graphite (bppg) electrode modified with carbon nanotubes is described. Abrasive immobilization of multiwall carbon nanotubes on a bppg electrode was achieved by gently rubbing the electrode surface on a filter paper supporting carbon nanotubes. The resulting electrode showed excellent mediation of epinephrine oxidation: a decrease in the overvoltage of the epinephrine electro-oxidation (200-500 mV) was observed as well as a dramatic increase in the peak current (4 times) compared to that seen at a bare bppg electrode. The oxidation peaks of epinephrine and ascorbic acid which overlap on bare bppg electrode were separated successfully (by ca. 220 mV) at the surface of the modified bppg electrode. The modified electrode showed good stability in comparison to most modified carbon nanotubes electrodes prepared by alternative methods.     

Imprinting of molecular recognition sites through electropolymerization of functionalized Au nanoparticles: development of an electrochemical TNT sensor based on pi-donor-acceptor interactions

Electrochemical sensors for the analysis of TNT with enhanced sensitivities are described. The enhanced sensitivities are achieved by tailoring pi-donor-acceptor interactions between TNT and pi-donor-modified electrodes or pi-donor-cross-linked Au nanoparticles linked to the electrode. In one configuration a p-aminothiophenolate monolayer-modified electrode leads to the analysis of TNT with a sensitivity corresponding to 17 ppb (74 nM). In the second configuration, the cross-linking of Au NPs by oligothioaniline bridges to the electrode yields a functionalized electrode that detects TNT with a sensitivity that corresponds to 460 ppt (2 nM). Most impressively, the imprinting of molecular TNT recognition sites into the pi-donor oligoaniline-cross-linked Au nanoparticles yields a functionalized electrode with a sensitivity that corresponds to 46 ppt (200 pM). The electrode reveals high selectivity, reusability, and stability.     

苯在铑电极上吸附的表面增强拉曼散射光谱研究

利用成熟的电极处理方法成功地获得了苯在粗糙铑电极上电化学吸附的拉曼谱图.详细探讨了电极电位、电解质等因素对苯的电化学吸附的影响.结果表明,苯分子吸附到粗糙铑电极上后,表面拉曼谱图与纯苯本体谱图的差别很大,说明吸附后的苯分子在几何及电子结构上发生了巨大变化.苯分子可能以1,3-环己二烯的结构吸附于铑电极表面.     

Study of an Au colloid self-assembled electrode and its application to the determination of carbon monoxide

A novel electrochemical sensor has been developed for the detection of carbon monoxide. The chemically modified electrode, prepared by reaction of cysteine and then an Au colloid of size approximately 15 nm with a platinum microelectrode, has excellent catalytic activity toward carbon monoxide, with an oxidation potential of +600 mV relative to the Ag/AgCl electrode. The CO gas sensor is based on an Au colloid self-assembled modified electrode as working electrode, an Ag/AgCl electrode as reference electrode, a Pt electrode as counter electrode, and a porous film which is in direct contact with the gas-containing atmosphere. The effects on the determination of CO of different internal electrolyte solutions of perchloric acid, hydrochloric acid, sulfuric acid, nitric acid, and phosphate buffer of different concentrations were also studied. The sensor is characterized by a short response time and highly reproducible detection of CO. This sensor can be used in the field of environmental monitoring and control.     

Study of an Au colloid self-assembled electrode and its application to the determination of carbon monoxide

A novel electrochemical sensor has been developed for the detection of carbon monoxide. The chemically modified electrode, prepared by reaction of cysteine and then an Au colloid of size approximately 15 nm with a platinum microelectrode, has excellent catalytic activity toward carbon monoxide, with an oxidation potential of +600 mV relative to the Ag/AgCl electrode. The CO gas sensor is based on an Au colloid self-assembled modified electrode as working electrode, an Ag/AgCl electrode as reference electrode, a Pt electrode as counter electrode, and a porous film which is in direct contact with the gas-containing atmosphere. The effects on the determination of CO of different internal electrolyte solutions of perchloric acid, hydrochloric acid, sulfuric acid, nitric acid, and phosphate buffer of different concentrations were also studied. The sensor is characterized by a short response time and highly reproducible detection of CO. This sensor can be used in the field of environmental monitoring and control.     

A simple approach for fabrication of dual-disk electrodes with a nanometer-radius electrode and a micrometer-radius electrode

We developed a new simple approach to fabricate dual-disk electrodes with a nanometer-radius electrode and a micrometer-radius electrode. First, nanometer-sized electrodes and micrometer-sized electrodes were constructed using 10-μm-radius metal wires, respectively. To fabricate the nanometer-sized electrode, after the apex of the 10-μm-radius metal wire was electrochemically etched to an ultrafine point with a nanometer-radius, the metal wire was electrochemically coated with a phenol-allyphenol copolymer film. The micrometer-sized electrode was fabricated by directly electrochemical coating the metal wire with an extremely thin phenol-allyphenol copolymer film. Then, the nanometer-radius electrode (the first electrode) and the 10-μm-radius electrode (the second electrode) were inserted into two sides of a thick-septum borosilicate theta (θ) tubing, respectively. The second electrode protruded from the top of the θ tubing. The top of the θ tubing was sealed with insulating ethyl α-cyanoacrylate. The top of the θ tubing with both electrodes was ground flat and polished successively with fine sandpaper and aluminum oxide powder until the tip of the first electrode was exposed. Since the second electrode protruded from the top of the θ tubing, its 10-μm-radius tip was naturally formed during polishing. The dual-disk electrodes were characterized by scanning electron microscopy and cyclic voltammetry. The success rate for fabrication of the dual-disk electrodes is ∼80% due to double insurance from two coating layers of different polymers.     

扫描电化学显微镜直接电沉积法构建葡萄糖氧化酶微米点

利用自制的凹形电极在铂基底电极上直接构建了葡萄糖氧化酶微米点. 首先, 将电聚合和电化学刻蚀法相结合制备了凹形铂微米电极. 然后将此种电极作为参比及辅助电极, 基底铂电极作为工作电极, 利用葡萄糖氧化酶在合适的条件下(浓度、一定量Triton X-100存在、电极电位等)由于电极表面pH的降低可以在铂电极上电沉积这一特性, 将酶固定在铂基底电极上, 微修饰得到了具有活性的葡萄糖氧化酶微米点. 最终用扫描电子显微镜和扫描电化学显微镜对所得微米点进行了表征. 所得微米点直径约20 μm, 且具有催化活性. 该方法简便, 干扰因素较少.     

Evaluation of the oxygen reduction activities of rare-earth oxide-supported silver catalysts using a channel flow double electrode.

The channel flow double electrode (CFDE) was used for the evaluation of the oxygen reduction activities in alkaline solution of rare-earth oxide-supported silver catalysts. The CFDE cell was modified for the experiment using the powder catalyst as a working electrode. In the present experiment, the silver electrode was supported with CeO2 in order to improve the performance of the oxygen reduction. The detecting electrode current for HO2- emitted from the working electrode was recorded simultaneously with the measurement of the i-E curve of each working electrode. Moreover, the average number of charge transfers n was calculated from the working and detecting electrode currents. The value of n for the oxygen reduction was approximately 4 for silver electrode supported with rare-earth oxide, compared with the n value of pure silver that was smaller than 4. On the basis of these results, the mechanisms of oxygen reduction on these electrodes and role of the rare-earth oxide in alkaline solution were discussed.     

Construction and Application of a PVC Membrane Enoxacin Ion－selective Electrode Based on a Needle－shaped Inner Reference Electrode

IntroductionPVC membrane- coated- wire electrodes areused in the analytical field widely. They are pre-pared usually with platinum wire,silver wire orgraphite rod coated with a PVC thin membranecontaining various active components and plasticiz-ers[1— 3 ] .The electrodes have no inner KCl solutionand they are notinfluenced by the sample pressure.Furthermore,they are free from directional selec-tivity when they are installed,and they can be mi-crominiaturized easily. The shortcomings of th…     

Redox kinetic measurements of glutathione at the mercury electrode by means of square-wave voltammetry. The role of copper, cadmium and zinc ions

The electrode reaction of glutathione (GSH) at the hanging mercury drop electrode is studied by means of square-wave voltammetry (SWV). At potentials more positive than -0.350 V (vs. Ag/AgCl (3 mol/l KCl)) the oxidation of the mercury electrode in the presence of GSH leads to creation of a sparingly soluble mercury-GSH complex that deposits onto the electrode surface. Under cathodic potential scan, the deposited complex acts as a reducible reactant, giving raise to a well-defined cathodic stripping reversible SW voltammetric response. The electrode reaction can be described by the scheme: Hg(SG)(2(s))+e(-)+2H((aq))(+) = Hg((l))+2GSH((aq)). Thus, the electrode reaction provides information on both thermodynamics and kinetics of the chemical interactions of GSH with mercury. An experimental methodology for measuring the kinetics of the electrode reactions, based on the property known as "quasireversible maximum", is developed. The standard redox rate constant is 5.09, 5.75 and 5.22 cm s(-1) in a phosphate buffer at pH 5.6, 7.0 and 8.5, respectively, with a precision of +/-10%. The high rate of the electrode reaction reflects the strong affinity of GSH towards chemical interaction with mercury. The electrode reaction is particularly sensitive to the presence of heavy metal ions such as Cu(2+), Cd(2+), and Zn(2+.) The rate of the electrode reaction decreases significantly in the presence of these ions due to simultaneous interactions of GSH with the respective ion and mercury.     

血红素LB膜的电化学行为

采用循环伏安法研究了血红素与脑磷脂混合Y型LB（Langmuir-Blodgett）膜在玻碳电极上的电化学行为，结果表明血红素LB膜有良好的电化学活性，在0．1mol/L KCl溶液中有一对氧化还原峰（－0．42V／－0．30V）；将血红素LB膜转移到玻碳电极表面得到的血红素LB膜修饰电极（heme LB-GC）对溶液中溶解氧的电化学还原有良好的催化作用，其催化还原过程具有不可逆电荷传递特性。     

Potentiometric detection of ascorbate using a graphite carbon electrode

A graphite carbon electrode was used for the potentiometric detection of ascorbate. The electrode exhibits a linear response with a slope of -42+/-1.0 mV decade(-1) in concentrations ranging from 5x10(-4) to 5.0x10(-2) M in 0.1 M NaOH solution with a detection limit of 5.0x10(-6) M. The response mechanism of this electrode was investigated by potentiometry, voltammetry, and scanning electron micoscropy (SEM), and it suggests that the electrode potential change resulted from the ion-exchange adsorption and subsequent oxidation of ascorbate on the electrode surface at pH 12-13. The electrode exhibits high sensitivity, selectivity and reproducibility.     

Pt微粒修饰纳米纤维聚苯胺电极对甲醇氧化电催化

以脉冲电流法制备的纳米纤维状聚苯胺(PANI)为Pt催化剂载体，用它制备了甲醇阳极氧化的催化电极Pt/（nano-fibular PANI）.研究结果表明, Pt/（nano-fibular PANI）电极对甲醇氧化具有很好的电催化活性,并有协同催化作用.在相同的Pt载量条件下， Pt/（nano-fibular PANI）电极比Pt微粒修饰的颗粒状聚苯胺电极Pt/(granular PANI)具有更好的电催化活性.此外， Pt的电沉积修饰方法同样影响Pt/（nano-fibular PANI）电极对甲醇氧化的催化活性.脉冲电流法沉积Pt形成的复合电极较循环伏安法电沉积得到的Pt复合电极具有更优异的催化活性.