The Electrochemical Behavior and the Quantitative Determination of Nitrogen Dioxide at a Solid Polymer Electrolyte Supported Pt‐Au Electrode

The electrochemical behavior of NO₂ at Au/Nafion, Pt/Nafion and Pt‐Au/Nafion electrodes was investigated by using electrochemical and SEM methods, respectively. It was found that the Pt‐Au/Nafion electrode showed higher electrocatalytic activity than Pt/Nafion and Au/Nafion electrodes. The net current density of Au/Nafion electrode decayed significantly during the reaction, though it showed high initial value. Pt/Nafion and Pt‐Au/Nafion electrodes, on the contrary, showed good stability. A quantitative determination of NO₂ concentration was carried out at Pt‐Au/Nafion electrode and a satisfactory linear relationship was found for the NO₂ concentration in the range of 0–100 ppm.     

Electrochemical Detection of Catechol on Boron‐doped Diamond Electrode Modified with Au/TiO2 Nanorod Composite

Au/TiO₂ nanorod composites with different ratios of [TiO₂]:[Au] have been prepared by chemically reducing AuCl₄^‐ on the positively charged TiO₂ nanorods surface and used to modify boron‐doped diamond (BDD) electrodes. The electrochemical behaviors of catechol on the bare and different Au/TiO₂ nanorod composites‐modified BDD electrodes are studied. The cyclic voltammetric results indicate that these different Au/TiO₂ nanorod composites‐modified BDD electrodes can enhance the electrocatalytic activity toward catechol detection, as compared with the bare BDD electrode. Among these different conditions, the Au/TiO₂‐BDD3 electrode (the ratio of [TiO₂]:[Au] is 27:1) is the most choice for catechol detection. The electrochemical response dependences of the Au/TiO₂‐BDD3 electrode on pH of solution and the applied potential are studied. The detection limit of catechol is found to be about 1.4 × 10^‐6 M in a linear range from 5 × 10^‐6 M to 200 × 10^‐6 M on the Au/TiO₂‐BDD3 electrode.     

A Voltammetric Sensor Based on Spinel-Structured Copper Ferrite Nanoparticles Multiwalled Carbon Nanotubes Modified Carbon Paste Electrode for Determination of Dacarbazine

A simple and sensitive method was used to develop a novel sensor for determination of dacarbazine on the surface of multi-walled carbon nanotubes/CuFe₂O₄ nanoparticles modified carbon paste electrode (MWCNTs/CuFe₂O₄/CPE). Cyclic voltammetry, differential pulse voltammetry, chronoamperometry, and electrochemical impedance spectroscopy were used to investigate the electrochemical behavior of dacarbazine at the chemically modified electrode. According to the results, MWCNTs/CuFe₂O₄/CPE showed high electrocatalytic activity for dacarbazine oxidation, producing a sharp oxidation peak current at about +0.80 vs. Ag/AgCl reference electrode at pH 5.0. The peak current was linearly dependent on dacarbazine concentration over the range of 0.10–76.0 μmol L^–1 with the detection limit (3σ) of 0.08 μmol L^?1. In addition, chronoamperometry was also used to determine diffusion coefficient of dacarbazine at MWCNTs/CuFe₂O₄/CPE.     

Characterization of stainless steel electrode modified by a thin film of polyaniline containing pt particles and its electrocatalytic activity for methanol oxidation

The catalytic behavior of stainless steel (SS) electrode modified by a thin film of polyaniline (PANI) containing platinum particles was studied for electrooxidation of methanol and compared with a platinated Pt/PANI electrode in acidic aqueous solution. Cyclic voltammetry (CV), chronoamperometry, CO stripping techniques were used to investigate electrochemical properties and electrocatalytic activity of SS/PANI/Pt and Pt/PANI/Pt electrodes. The morphology and particle size of Pt catalysts were characterized by Transmission Electron Microscopy (TEM) measurement. The effects of various parameters such as thickness of polymer film, medium temperature and stability of the modified electrodes on methanol oxidation were also investigated. The results indicated that the modified SS electrode exhibited a considerably high electrocatalytic activity on the methanol oxidation as well as the modified Pt electrode.     

Enhanced Electrocatalytic Oxidation of Paracetamol at DNA Modified Gold Electrode

Cysteine monolayer has been assembled onto bare gold electrode (SAM/Au), and subsequently deoxyribonucleic acid (DNA) has been successfully immobilized at the SAM/Au electrode. The thus modified electrode is assigned DNA/SAM/Au. Modification steps of the electrode were followed electrochemically using K₄[Fe(CN₆)] electrochemical marker. Also, the build‐up of the modified electrode composition is followed using EDX and the crystallographic orientation is inspected using XRD. The electrochemical behavior of paracetamol (PC) at DNA/SAM/Au electrode is investigated. Interestingly, the sluggish irreversible behavior of PC at the bare gold electrode is converted to a quasi‐reversible one at DNA/SAM/Au electrode pointing to some interaction between the immobilized DNA and PC. The enhanced electrochemical behavior of PC at modified DNA/SAM/Au electrode is successfully used for a sensitive electrochemical determination of PC. Square wave voltammetry (SWV) was used for this purpose. The concentration of PC was in linear relation with the peak current at the optimum conditions within the range 10.0–110.0 μg mL^?1 with correlation coefficient (R²) of 0.998. Also, the standard deviation (SD) and relative standard deviation (RSD) were calculated and found to be 0.817 and 1.52, respectively, indicating the significance of the present method.     

A Comparison of a Nanostructured Enzymeless Au/Fe2O3/MWCNTs/GCE Electrode and a GOx Modified One in Electrocatalytic Detection of Glucose

Acid functionalized multi‐walled carbon nanotubes (f‐MWCNTs) were decorated with Au and Fe₂O₃ nanoparticles (FeONPs) and deposited on glassy carbon electrode (GCE). The resulting hybrid Au/Fe₂O₃/f‐MWCNTs/GCE electrode and the one further modified by glucose oxidase were compared for detection of glucose. FeONPs and Au were deposited on the f‐MWCNTs by sonication‐assisted precipitation and deposition‐precipitation methods, respectively. The morphology and structure of the samples were characterized by transmission electron microscopy, scanning electron microscopy, X‐ray diffraction and Raman spectroscopy. A uniform distribution of FeONPs with an average size of 5 nm increased the surface area of functionalized nanotubes from 39 to 50 m²/g. The electrocatalytic glucose detection on the modified electrodes was evaluated using cyclic voltammetry and chronoamperometry in 0.1 M phosphate buffer solution at pH 7.0. The non‐enzymatic and enzymatic electrodes show sensitivity of 512.4 and 921.4 mA/mM.cm² and detection limit of 1.7 and 0.9 mM, respectively. The enzymatic and enzymeless electrodes retained more than 70 % and 80 % of their cathodic faradic current after 70 days, respectively. The sensing mechanism of the non‐enzymatic biosensor is described through the reaction of glucose with iron (III) ions, while in the case of enzymatic electrode, glucose is oxidized by glucose oxidase.     

Oxygen reduction at the surface of glassy carbon electrodes modified with anthraquinone derivatives and dyes

The preparation, electrochemical and catalytic behaviour of glassy carbon electrodes modified by anthra-9,10-quinone, its amino derivatives and dyes were investigated. The stability of the modified electrodes was studied by cyclic voltammetry in acidic and neutral media. The electrocatalytic ability of the modified electrodes for the reduction of dioxygen to hydrogen peroxide was examined by cyclic voltammetry, chronoamperometry and chronocoulometry techniques. The influence of pH on the electrochemical and catalytic behaviour was studied and pH 5.0–8.0 was chosen as the optimum working pH by comparing the shift in oxygen reduction potential. The anthraquinone-adsorbed glassy carbon electrodes possess excellent electrocatalytic abilities for dioxygen reduction with overpotential ranging from 280 to 560 mV lower than that at a plain glassy carbon electrode. Hydrodynamic voltammetric studies were performed to determine the heterogeneous rate constants for the reduction of O₂ at the surface of the modified electrodes, mass specific activity of the anthraquinones used and the apparent diffusion coefficient of O₂ in buffered aqueous O₂-saturated solutions. Studies showed the involvement of two electrons in dioxygen reduction.     

Composite electrodes consisting Pt nano-particles and poly (aminophenols) film on pre-treated aluminum substrate as electrocatalysts for methanol oxidation

Electrochemically platinum plated aluminum (Al/Pt) was used as an electrode substrate for the electropolymerization of aminophenols and fabrication of composite electrodes based on platinum nano-particles. The poly(o-aminophenol) (PoAP), poly(m-aminophenol) (PmAP), and poly(p-aminophenol) (PpAP) were synthesized on the Al/Pt electrode, and further modification was performed by deposition of platinum nano-particles onto polymer matrixes. The electrochemical and morphological characteristic of the composed electrodes were carried out by cyclic voltammetry and scanning electron microscopy, respectively. The electrocatalytic oxidation of methanol on the composite electrodes was studied by cyclic voltammetry in 0.1 M sulfuric acid as supporting electrolyte. It was found that the Al/Pt/PoAP electrode incorporated Pt nano-particles (Al/Pt/PoAP/Pt) exhibits a higher electrocatalytic activity for the oxidation of methanol than the Al/Pt/PmAP/Pt and Al/Pt/PpAP/Pt electrodes. On the other hand, a higher catalytic current for methanol oxidation was found on the Al/Pt/PoAP/Pt electrode in comparison to bulk Pt and Al–Pt (Al with 0.2 mg cm⁻² of Pt particles) electrodes. The effects of various parameters such as thickness of the polymer film, concentration of the monomer, Pt loading method and the Pt amounts, concentration of the methanol, and the medium temperature were studied on the electrooxidation of methanol. The long-term stability of the modified electrode has also been investigated.     

电镀铂/金的金电极上As(Ⅲ)电化学行为的电化学石英晶体微天平研究

采用电化学石英晶体微天平(EQCM)技术研究了Britton-Robinson(B-R,pH=1.8～11.2)缓冲溶液和H2SO4介质中电镀铂淦的金电极上As(Ⅲ)的循环伏安行为.通过实时监测EQCM频率等参数的变化过程并利用预电沉积As(O)放大电极响应信号,考察了两电极上As.(O)的电沉积、AsⅢ皿和AsⅤ助组...     

Au/L-Met/GC电极的H2O2电催化氧化

在无额外的添加剂和保护剂的情况下,以柠檬酸钠还原氯金酸制得链状金纳米粒子,使用扫描电子显微镜（SEM）和透射电子显微镜（TEM）观察样品. 层层自组装技术可将金纳米粒子自组装,并分别以L-甲硫氨酸（L-Methionine,L-Met）、硫脲（Thiourea,TU）、丙烯基硫脲（Allyl thiourea,ATU）和聚乙烯吡咯烷酮（Polyvinylpyrrolidone,PVP）交联剂自组装于玻碳基底,即得金纳米粒子修饰电极. 以[Fe(CN)₆]^3-/4-氧化还原电对为探针,考察该修饰电极的电化学性质. Au/L-Met/GC电极有最佳电化学性能,循环伏安曲线和计时电流曲线测试表明,Au/L-Met/GC电极的H₂O₂电催化氧化有较高的灵敏度,线性范围2×10^-7 ~ 3×10^-3 mol·L^-1,检出限6.67×10^-8 mol·L^-1.     

[SiCu(H2O)W11O39]6-在玻碳电极上的多层组装及电催化性能

The electrochemical behavior of SiCu W11 heteropolyacide in acidic aqueous solution was studied. The effect of solution pH on the electrochemical behavior of SiCu W11 was discussed and the mechanism was suggested. New electrode was modified by muhilayer films composed of heteropolyanion (SiCu W11 and cationic polymer poly (diallyldimethylammonium chloride). Cyclic vohammetry showed the uniform growth of the film. The modified electrodes exhibited some special electrochemical properties in the films, different from those in homogeneous aqueous solutions. The effect of pH on the redox behavior of SiCu W11 in the films was discussed in details. The muhilayer film electrodes have an excellent electrocatalytic response to the reduction of BrO3^- and NO2^-.     

抗坏血酸在PPy-HEImTfa/Pt电极上的电催化氧化及其机理

以铂为基底电极,在1-乙基咪唑三氟乙酸盐(HEImTfa)离子液体中电化学合成导电聚吡咯(PPy),制得PPy-HEImTfa/Pt电极;采用循环伏安法研究了PPy-HEImTfa/Pt电极对抗坏血酸的电催化氧化性能.结果表明:PPy-HEImTfa/Pt电极对0.1mo·lL-1抗坏血酸具有较高的电催化氧化活性,与相同条件下硫酸溶液中在铂表面修饰的聚吡咯(PPy-H2SO4/Pt)电极和裸铂电极相比,其氧化峰电位分别降低了0.10和0.19V,氧化峰电流分别增加了3.0和3.6mA.同时采用原位傅里叶变换红外(insitu FTIR)光谱技术对抗坏血酸在PPy-HEImTfa/Pt电极上的电氧化机理进行了研究,结果表明:抗坏血酸在PPy-HEImTfa/Pt电极上首先被氧化为脱氢抗坏血酸,在水溶液中脱氢抗坏血酸迅速发生水合作用形成水合脱氢抗坏血酸,它进一步水解并发生内酯开环反应生成2,3-二酮古洛糖酸;在较高电位下,部分抗坏血酸最终被氧化成CO2.     

Amperometric Sensors Based on Synthetic Hydrotalcites and Their Application for Ethanol Detection in Beer

The electrochemical and electrocatalytic behavior of electrodes modified with a Co/Al‐NO₃ hydrotalcite (HT) has been investigated and compared with that displayed by Ni/Al‐NO₃ HT modified electrodes. Mono and polyhydric compounds have been tested to study electrocatalysis. At Co/Al‐NO₃ HT modified electrodes only polyhydric compounds give e current signal, whereas at Ni/Al‐NO₃ HT modified electrodes, both alcohols and polyhydric compounds can be detected. The different electrocatalytic behavior of Ni and Co based electrodes has been exploited to develop an analytic method for the selective determination of alcohols in the presence of polyhydric compounds. Samples of beer found on the Italian market have been analyzed to verify the validity of the proposed method in the detection of the ethanol content. The procedure does require neither a preliminar treatment nor a separation of the sample, but only the recording of two cyclic voltammogramms, one with the Co/Al‐NO₃ and one with the Ni/Al‐NO₃ HT modified electrode. The results obtained have been promising.     

Electrochemical-reduced graphene oxide-modified carbon fiber as Pt–Au nanoparticle support and its high efficient electrocatalytic activity for formic acid oxidation

A simple electrochemical approach is developed to prepare reduced graphene oxide (RGO)-wrapped carbon fiber (CF) as a novel support for Pt–Au nanocatalysts. The obtained composite electrodes have been characterized by scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDX), thermal gravimetric analysis (TGA), and electrochemical methods. SEM images reveal that the Pt–Au nanoparticles deposited on RGO-wrapped CF (RGO/CF) electrode display smaller particle size and more uniform dispersion than those on the bare CF electrode. Cyclic voltammetry, linear sweep voltammetry, chronoamperometry, chronopotentiometry, Tafel plots, and electrochemical impedance spectroscopy (EIS) analyses demonstrate that the introduced RGO on CF electrode surface is beneficial to the dispersion of Pt–Au nanoparticles, as a consequence, to the enhancement of the electrocatalytic activity and the antipoisoning ability of Pt–Au towards formic acid electrooxidation.     

Electroreduction of Oxygen and Electrooxidation of Methanol at Carbon and Single Wall Carbon Nanotube Supported Platinum Electrodes

The present research aimed at investigating the electrocatalytic properties and the electrochemical deposition of Pt nanoparticles on carbon powder, carbon nanotube and preparation of carbon and single wall carbon nanotube supported platinum electrodes. The Pt nanoparticles were synthesized by electroreduction of hexachloroplatinic acid in aqueous solution at ?200 mV. Electrocatalytic properties of the modified electrodes for oxygen reduction were investigated by cyclic voltammetry in O₂ saturated solution containing 0.1 M HClO₄. Methanol electrooxidation at the modified surfaces in 0.5 M HCLO₄ was studied by cyclic voltammetry. The corresponding results showed that the Pt/SWCNT/GC electrode exhibits more improved catalytical activity than the Pt/C/GC electrode.     

Electrochemical Properties of a Boron‐Doped Diamond Electrode Modified with Gold/Polyelectrolyte Hollow Spheres

Oppositely charged polyelectrolyte (poly(allyamine hydrochloride) (PAH) and poly(sodium 4‐styrene‐sulfonate) (PSS)), and negatively charged gold nanoparticles (Au) were assembled alternately on polystyrene (PS) spheres via layer‐by‐layer technique, and the different PAH/(PSS/PAH)_n/(Au/PAH)_m/Au composite hollow spheres were derived by dissolving PS core. These hollow spheres were used to modify boron‐doped diamond (BDD) electrodes for electrochemical sensors. The cyclic voltammetric results for dopamine (DA) detection demonstrated that hollow‐sphere‐modified BDD exhibited better electrocatalytic activity than did bare BDD. Influence of the wall thickness and composition of hollow spheres on electrochemical properties were investigated. The results showed that the oxidative peak potential of DA and the peak current varied with different PSS/PAH and Au/PAH layers. The optimized wall structure of hollows spheres was PAH/(PSS/PAH)₇/(Au/PAH)₅/Au.     

基于Pt/Au双金属修饰针灸针的非酶葡萄糖传感器

通过在不锈钢针灸针（AN）表面依次电沉积金（Au）纳米颗粒和铂（Pt）纳米颗粒,基于它们在AN表面的协同作用,实现了一种用于非酶葡萄糖检测的电化学生物传感器。首先,通过扫描电子显微镜对其功能界面（Pt/Au/AN）进行表征,结果显示类似卷心菜的纳米材料均匀致密地分布在AN表面。然后,通过循环伏安法和电化学阻抗法对Pt/Au/AN电极的电化学特性进行了研究。结果表明,与Au/AN或Pt/AN电极相比,Pt/Au/AN电极对葡萄糖氧化表现出优越的电催化活性。这表明双金属Pt/Au的接触界面是葡萄糖氧化的重要电催化位点。在pH7.4的模拟生理介质中,制得传感器的线性范围为0.1~35 mmol·L^-1,检测限为0.0763 mmol·L^-1,对葡萄糖的检测表现出较高的灵敏度和良好的抗干扰性能、稳定性。此外,该传感器已成功用于人体血清葡萄糖的检测。     

乙二醛在Ti/纳米TiO2-Pt修饰电极上的电催化氧化

采用溶胶-凝胶和电沉积法制备Ti基纳米TiO2-Pt(Ti/纳米TiO2-Pt)修饰电极. X射线衍射(XRD)表明纳米TiO2为锐钛矿型, 扫描电镜(SEM)显示Pt纳米粒子在纳米TiO2多孔膜的表面呈现簇分散状态, 平均粒径约25 nm. 通过循环伏安(CV)和计时电流法研究了Ti/纳米TiO2-Pt修饰电极对乙二醛直接电氧化的电催化活性, 结果表明, 修饰电极对乙二醛的直接电氧化呈现良好的催化活性, 在0.60和1.23 V(vs SCE)出现两个氧化峰, 二者电流密度分别为16 和42 mA·cm-2, 约为纯Pt电极的2倍和1.5倍, 反应过程受浓差扩散控制.     

Electorchemical Studies of Cytochrome c on Electodes Modified by Single—Wall Carbon Naotubes

Single-wall carbon nanotubes(SWNTs) modified gold electrodes were prepared by using two different methods.The electrochemical behavior of cytochrome c on the modified gold electrodes was investigated.The first kind of SWNT-modified electrode (noted as SWNT/Au electrode)was prepared by the adsorption of carboxylterminated SWNTs from DMF dispersion on the gold electrode.The oxidatively processed SWNT tips were covalently modified by coupling with amines (AET) to form amide linkage.Via Au-S chemical bonding,the self-assembled monolayer of thiol-unctionalized nanotubes on gold surface was fabricated so as to prepare the others SWNT-modified electrode (noted as SWNT/AET/Au electrode).It was shown from cyclic voltammetry cxperiments that cytochrome c exhibited direct electrochemical responses on the both electrodes, but only the current of controlled diffusion existed on the SWNT/Au electrode while both the currents of controlled diffusion and adsorption of cytochrome c occurred on the SWNT/AET/Au electrode.Photoelastic Modulation Infared Reflection Absorpthion Spectroscopy (PEM-IRRAS) and Quartz Crystal Microbalance (QCM) were employed to verify the adsorption of SWNTs on the gold electrodes.The results proved that SWNTs could enhance the direct electron transfer proecss between the electrodes and redox proteins.     

Kinetics of ethylene glycol electrooxidation on the noble metal-based nano-catalysts

A comparative electrooxidation of Eg in the alkaline solution was investigated over Pt, Pd and Au nanoparticle-modified carbon-ceramic electrode. The kinetic parameters of Eg oxidation, i.e., Tafel slope and activation energy (E _a), were determined on the modified electrodes. The lowest E _a value of 8.9 kJ mol^?1 was calculated on Pt|CCE. In continuation, the reaction orders with respect to the Eg and NaOH concentrations on Pd|CCE were found to be 0.4–0.2 and 0.6, respectively. An adsorption equilibrium constant (b) of 22.36 M^?1 and the adsorption Gibbs energy change (ΔG°) of ?7.7 kJ mol^?1 were obtained on Pd|CCE. The chronopotentiometry (CP) and chronoamperometry (CA) results showed that Pd|CCE and then Au|CCE have better performance stability than Pt|CCE for Eg electrooxidation. Additionally, the electrochemical impedance spectroscopy (EIS) suggested faster electron-transfer kinetics on Pt than that on the Pd and Au electrocatalysts.