Electropolymerization of iron tetra(<Emphasis Type="Italic">o</Emphasis>-aminophenyl)porphyrin from aqueous solution and the electrocatalytic behavior of modified electrode

Stable electroactive iron tetra(o-aminophenyl)porphyrin (FeTAPP) films are prepared by electropolymerization from aqueous solution by cycling the electrode potential between −0.4 and 1.0 V vs Ag/AgCl at 0.1 V s⁻¹. The cyclic voltammetric response indicates that polymerization takes place after the oxidation of amino groups, and the films could be produced on glassy carbon (GC) and gold electrodes. The film growth of poly(FeTAPP) was monitored by using cyclic voltammetry and electrochemical quartz crystal microbalance. The cyclic voltammetric features of Fe(III)/Fe(II) redox couple in the film resembles that of surface confined redox species. The electrochemical response of the modified electrode was found to be dependent on the pH of the contacting solution with a negative shift of 57 mV/pH. The electrocatalytic behavior of poly(FeTAPP) film-modified electrode was investigated towards reduction of hydrogen peroxide, molecular oxygen, and chloroacetic acids (mono-, di-, and tri-). The reduction of hydrogen peroxide, molecular oxygen, and dichloroacetic acid occurred at less negative potential on poly(FeTAPP) film compared to bare GC electrode. Particularly, the overpotential of hydrogen peroxide was reduced substantially. The O₂ reduction proceeds through direct four-electron reduction mechanism.     

[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^-.     

Electrochemical behavior and assembly of tetranuclear Dawson-derived sandwich compound [Cd4(H2O)2(As2W15O56)2] on 4-aminobenzoic acid modified glassy carbon electrode

The transition metal-substituted heteropolyoxoanion, Cd₄(H₂O)₂(As₂W₁₅O₅₆)₂¹²⁻ (As₄W₃₀Cd₄), is one of the trivacant Dawson derivatives. Its redox electrochemistry has been studied in acid buffer solutions using cyclic voltammetry. It exhibited three steps of four-electron redox waves attributed to redox processes of the tungsten-oxo framework. Through layer-by-layer assembly, the compound was first successfully immobilized on a 4-aminobenzoic acid modified glassy carbon electrode surface by alternate deposition with a quaternized poly(4-vinylpyridine) partially complexed with [Os(bpy)₂Cl]^2+/+ (denoted as QPVP-Os). Thus, prepared multilayer films have been characterized by cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS) and UV-vis spectroscopy (UV-vis). The electrocatalytic activities of the multilayer films containing As₄W₃₀Cd₄ have been investigated on the reduction of three substrates of important analytical interests, NO₂⁻, BrO₃⁻ and IO₃⁻. And with the increase of the number of As₄W₃₀Cd₄ layers, the catalytic current towards the reduction of BrO₃⁻ was enhanced and the catalytic potential shifted positively.     

Synthesis, characterization and performance of vanadium hexacyanoferrate as electrocatalyst of H2O2

The present work reports for the first time on the synthesis, characterization and performance of vanadium hexacyanoferrate (VHCF) as electrocatalyst of hydrogen peroxide. VHCF was synthesized by mixing V₂O₅ · nH₂O xerogel with ascorbic acid and K₄[Fe(CN)₆] in double distilled water. X-ray powder diffraction, energy dispersive spectroscopy, scanning electron microscopy, and IR-spectroscopy data suggest the formation of nanocrystalline (mean crystal size 11 nm) compound with a tentative molecular formula K₂(VO)₃[Fe(CN)₆]₂. Composite films of VHCF with poly(vinyl alcohol) were developed over a glassy carbon electrode, and then covered with different (neutral, positively or negatively charged) membranes. The effect of each membrane on the working stability of the resultant sensors was evaluated. Cyclic voltammetry experiments showed that composite films exhibit a pair of reversible redox peaks, and a remarkable low potential electrocatalysis on both the reduction and oxidation of hydrogen peroxide. A linear calibration curve over the concentration range 0.01–3.0 mM H₂O₂ was constructed. Limit of detection (S/N = 3) of 4 μM H₂O₂ was calculated. The proposed transducer is quite selective to hydrogen peroxide. No response was observed in the presence of 10 mM ascorbic acid.     

Haemoglobin immobilized on nafion modified multi-walled carbon nanotubes for O2, H2O2 and CCl3COOH sensors

A conductive biocomposite film (MWCNTs-NF-Hb) containing multi-walled carbon nanotubes (MWCNTs) incorporated with entrapped haemoglobin (Hb) in nafion (NF) has been synthesized on glassy carbon electrode (GCE), gold (Au), indium tin oxide (ITO) and screen printed carbon electrode (SPCE) separately by potentiostatic methods. The presence of both MWCNTs and NF in the biocomposite film enhances the surface coverage concentration (Γ), and increases the electron transfer rate constant (K_s) to 132%. The biocomposite film exhibits a promising enhanced electrocatalytic activity towards the reduction of O₂, H₂O₂ and CCl₃COOH. The cyclic voltammetry has been used for the measurement of electrocatalysis results of analytes by means of biocomposite film-modified GCEs. The MWCNTs-NF-Hb-modified GCEs’ sensitivity values are higher than the values obtained for other film modified GCEs. The surface morphology of the biocomposite films which have been deposited on ITO has been studied using scanning electron microscopy and atomic force microscopy. The studies have revealed that there was an incorporation of NF and immobilization of Hb on MWCNTs. Finally, the flow injection analysis has been used for the amperometric studies of analytes at MWCNTs-Hb and MWCNTs-NF-Hb film modified SPCEs. The amperometric study results have shown higher slope values for MWCNTs-NF-Hb biocomposite film.     

Characterization and Electrocatalytic Properties of Composite Poly(new fuchsin) and Phosphomolybdate Films

Organic/inorganic hybrid films of poly(new fuchsin) and phosphomolybdate (PMo₁₂O ) have been prepared in acidic aqueous solutions. These new combination films are stable, electrochemically active, and can be produced on glassy carbon, platinum, gold, and transparent semiconductor tin oxide electrodes. An electrochemical quartz crystal microbalance along with cyclic voltammetry and UV‐visible absorption spectroscopy were used to study the in situ growth of the hybrid films. The hybrid poly(new fuchsin) and PMo₁₂O films showed four obvious redox couples, and when transferred to various acidic aqueous solutions, the formal potentials of the four redox couples were found to be pH dependent. The electrocatalytic reduction of ClO , BrO , IO , SO , S₂O , H₂O₂, and NO by the hybrid poly(new fuchsin) and PMo₁₂O films was achieved in acidic aqueous solutions. In an aqueous solution at pH 1.5, a hybrid poly(new fuchsin) and PMo₁₂O film showed a higher electrocatalytic reduction activity of IO than BrO or ClO , and the order of electrocatalytic activity was IO >BrO >ClO . The order of electrocatalytic reduction of SO , S₂O , H₂O₂, and NO by hybrid poly(new fuchsin) and PMo₁₂O films in an aqueous solution at pH 1.5 was NO >H₂O₂>S₂O and SO . The electrocatalytic reactions of the poly(new fuchsin) and PMo₁₂O films were investigated using the rotating ring‐disk electrode method.     

Fabrication of Covalently Attached Multilayer Film Electrode Containing Iron Porphyrin and Its Electrocatalysis Toward Sulfite

Construction of a highly stable covalently attached multilayer film electrode containing iron porphyrin was achieved by UV irradiation of ionic self‐assembled multilayer films of diazo‐resins (DAR) and anionic Fe(III)tetrakis(p‐sulfonatophenyl)porphyrin (FeTSPP). The multilayer films had been characterized by UV, IR spectra and cyclic valtammetry. The electrocatalytic transformation of sulfite to SO₄^2? by the multilayer film electrode containing FeTSPP was investigated. In 0.1 M NH₄OH? NH₄Cl buffer solution (pH 8.74) and 0.1 M borate buffer solution (pH 9.18) the electrocatalytic oxidation of sulfite through the multilayer film electrode can be performed. However, in acetate buffer solution (pH 4.0) the electrocatalytic reduction of sulfite by the multilayer film electrode had also good activity. The modified electrode also exhibited a fast response and good stability.     

金复合介孔SBA-15吸附血红蛋白在H2O2电催化反应中的应用

以P123嵌段共聚物表面活性剂为模板剂制备介孔氧化硅SBA-15,并用沉积-沉淀(DP)法在SBA-15介孔表面负载纳米Au颗粒制备得到金复合介孔SBA-15材料(Au-SBA-15).再以Au-SBA-15材料制备玻碳修饰电极,将血红蛋白固定于修饰电极上用循环伏安法考察其对不同浓度H2O2溶液的电催化反应.在固定了血红蛋白的Hb/Au-SBA-15/GC修饰电极上,H2O2在+0.95 V处出现了氧化峰,且随着H2O2浓度的增大峰电流不断增加,说明金复合介孔氧化硅材料具有良好的生物兼容性,有利于血红蛋白的固定,其修饰电极对H2O2溶液具有一定的电催化作用.     

Electrocatalytic Oxidation of Some Carbohydrates by Nickel/Poly(o‐Aminophenol) Modified Carbon Paste Electrode

This study investigates the electrocatalytic oxidation of glucose and some other carbohydrates on nickel/poly(o‐aminophenol) modified carbon paste electrode as an enzyme free electrode in alkaline solution. Poly(o‐aminophenol) was prepared by electropolymerization using a carbon paste electrode bulk modified with o‐aminophenol and continuous cyclic voltammetry in HClO₄ solution. Then Ni(II) ions were incorporated to electrode by immersion of the polymeric modified electrode having amine group in 1 M Ni(II) ion solution. Cyclic voltammetric and chronoamperometric experiments were used for the electrochemical study of this modified electrode; a good redox behavior of Ni(OH)₂/NiOOH couple at the surface of electrode can be observed, the capability of this modified electrode for catalytic oxidation of glucose and other carbohydrates was demonstrated. The amount of α and surface coverage (Γ*) of the redox species and catalytic chemical reaction rate constant (k) for each carbohydrate were calculated. Also, the electrocatalytic oxidation peak currents of all tested carbohydrates exhibit a good linear dependence on concentration and their quantification can be done easily.     

基于血红蛋白/硒化镉量子点多层膜的H2O2生物传感器

合成了水溶性硒化镉(CdSe)量子点,利用组装技术和静电吸附作用,将带正电荷的血红蛋白(Hb)和带负电荷的CdSe量子点层层组装到壳聚糖(chit)修饰的玻碳电极(GCE)表面,构建基于{Hb/CdSe}n多层膜的无电子媒介体的电流型生物传感器({Hb/CdSe}3/chit/GCE).运用紫外-可见吸收光谱、电致化学发光、交流阻抗和循环伏安技术来表征修饰膜,并研究传感器的作用机理、性能及分析应用.结果表明:与量子点薄膜法及量子点/血红蛋白复合物法等固载血红蛋白的其他方法相比,层层组装法能显著提高血红蛋白的固定量,保持血红蛋白的生物活性,增强传感器的灵敏度和稳定性.传感器检测H2O2的线性范围为4.0×10-8～4.8×10-6 mol·L-1(r=0.999 1),检测限为2.0×10-8mol·L-l.多层膜的电致化学发光研究,表明修饰电极有望用于电致化学发光传感器的制备.     

Indirect electrochemical oxidation of N -methyl- n -aminophenol by active oxygen species generated in situ from O2, H2O, and H2O2

Indirect electrochemical oxidation of N-methyl-n-aminophenol by active oxygen species was studied. The active species were in situ generated from O₂, H₂O₂, and H₂O in aqueous solutions with various pH values by using a gas-diffusion cathode in a diaphragmless electrolyzer with anodes made of platinum, lea dioxide, and ruthenium-titanium oxide (RTO). Original Russian Text ? G.V. Kornienko, N.V. Chaenko, V.L. Kornienko, 2008, published in Zhurnal Prikladnoi Khimii, 2008, Vol. 81, No. 8, pp. 1285–1289.     

Electrocatalytic Reduction of Oxygen at Glassy Carbon Electrodes Coated with Diazonium‐derived Porphyrin/Metalloporphyrin Films

In this study, the influence of the film structure was investigated on the electrocatalytic oxygen reduction at GC electrodes covered with porphyrin and metalloporphyrin rings via the diazonium modification method. For that purpose, primarily, tetraphenylporphyrin (TPP) films on GC electrode surfaces were prepared by electroreduction of in situ generated diazonium salts of 5‐(4‐aminophenyl)‐10,15,20‐triphenylporphyrin (APP) and 5,10,15,20‐tetrakis(4‐aminophenyl)porphyrin (TAPP) molecules. Next, the formation of metalloporphyrin films on the modified surfaces was accomplished through the complexation reactions of surface porphyrin rings with metal ions in the salt solutions containing Mn(II), Fe(III) and Co(II) ions. The resulting porphyrin and metalloporphyrin layers were identified with XPS and ICP‐MS. The electrochemical barrier properties of the films on GC surfaces were examined by cyclic voltammetry in K₃Fe(CN)₆ aqueous solution. The electrocatalytic abilities of the resulting films were also investigated for the oxygen electrochemical reduction by employing cyclic voltammetry in PBS solutions saturated with oxygen. The results showed that the oxygen reduction potentials on modified GC electrodes were shifted to less negative potentials compared to that of bare GC electrode. Also, it was obtained that the oxygen reduction reaction was more effective on the GC electrodes modified with TPP rings by using TAPP molecules than those prepared by using APP molecules.     

Preparation,Characterization, and Electrocatalytic Properties of Mixed‐Valent Nickel Hexacyanoferrate/Phosphomolybdate Hybrid Film Electrodes Towards Oxidation of Ascorbic Acid and Reduction of S2O$\rm{ {_{8}^{2-}}}$

Polynuclear mixed‐valent nickelhexacyanoferrate/phosphomolybdate (NiHCF/PMo), nickel/phosphomolybdate (Ni/PMo) hybrid films were prepared on glassy carbon electrode by multiple scan cyclic voltammetry. Combination of individual components gave the opportunity to fabricate hybrid film with tunable electrochemical and analytical properties compared to individual components. The film growth was monitored using electrochemical quartz crystal microbalance (EQCM). The cyclic voltammogram of the nickelhexacyanoferrate/phosphomolybdate film is characterized by four redox couple whereas nickel/phosphomolybdate hybrid film exhibits three redox couples. Cyclic voltammetric features suggest that the charge transfer process in both films resembles that of surface‐confined redox species. The voltammetric response of nickelhexacyanoferrate/phosphomolybdate film electrode was found to be depending on the pH of the contacting solution. Electrocatalytic behavior of nickel/phosphomolybdate hybrid film coated electrodes toward oxidation of ascorbic acid and reduction of sulfur oxoanion, S₂O , was investigated using cyclic voltammetry technique. Analytical application of nickel/phosphomolybdate hybrid film electrode was tested in amperometry and flow injection analysis.     

一个新的夹心型杂多钨酸盐Na6(C5N2H7){[Na(H2O)2]3Co(H2O)5-[Co(H2O)]3(AsW9O33)2}•27H2O的晶体结构及性质

在pH＝7.5的水溶液中, Na₂WO₄•2H₂O, NaAsO₂, CoCl₂•6H₂O与对氨基吡啶反应, 得到了一种新的夹心型杂多钨酸盐Na₆(C₅H₇N₂){[Na(H₂O)₂]₃Co(H₂O)₅[Co(H₂O)]₃(AsW₉O₃₃)₂}•27H₂O单晶, 用X射线单晶衍射法及元素分析确定了其结构, 晶体属三斜晶系, P 空间群, 其晶胞参数为: a＝1.3276(8) nm, b＝1.7581(10) nm, c＝2.4381(14) nm, α＝70.954(9)°, β＝86.663(9)°, γ＝72.885(9)°, V＝5.136(5) nm³, Z＝2, R₁＝0.0608, wR₂＝0.0848 [I＞2σ(I)]. 在{[Na(H₂O)₂]₃Co(H₂O)₅[Co(H₂O)]₃(AsW₉O₃₃)₂}^7－阴离子中, 一个Co^2＋与聚阴离子{[Na(H₂O)₂]₃[Co(H₂O)]₃(AsW₉O₃₃)₂}^9－的一个端基氧共价连接, Co^2＋呈现出5和6两种配位数, 质子化的氨基吡啶正离子作为抗衡离子存在于晶体之中. 对标题化合物进行了IR, UV-Vis, TG-DSC表征. 对该化合物、Na₂WO₄•2H₂O及CoCl₂•6H₂O催化H₂O₂氧化乙醛的活性进行了比较研究, 该化合物的催化活性远优于简单化合物Na₂WO₄•2H₂O和CoCl₂•6H₂O.     

Structural and spectral studies of di-2-pyridyl ketone N(4)-methyl- and N(4)-dimethylthiosemicarbazone and their metal complexes

Cobalt(II), nickel(II) and copper(II) complexes of di-2-pyridyl ketone N(4)-methyl- and N(4)-dimethylthiosemicarbazone have been prepared and characterized by physical and spectral methods. Use of different ligand-to-metal chloride molar ratios in the preparation of the complexes has produced both mononuclear and polynuclear species for the three metal ions. Crystal structures of the uncomplexed di-2-pyridyl ketone N(4)-methylthiosemicarbazone and a nickel(II) complex, di-2-pyridyl ketone N(4)-dimethylthiosemicarbazone, have been determined and aid the assignments of the i.r., n.m.r., u.v.–vis.–n.i.r. and e.s.r. spectra.     

Structure and photophysical and electrochemical properties of a copper porphyrin complex with a three‐dimensional framework

Porphyrins and metalloporphyrins can generally show attractive structural motifs and interesting properties. A new copper porphyrin, namely poly[[μ‐chlorido‐[μ₅‐5,10,15,20‐tetrakis(pyridin‐4‐yl)‐21H,23H‐porphine]tricopper(I)] [aquadichloridocopper(II)]], {[Cu₃(C₄₀H₂₄N₈)Cl][CuCl₂(H₂O)]}_n ( 1 ), was synthesized by the self‐assembly of copper chloride with 5,10,15,20‐tetrakis(pyridin‐4‐yl)‐21H,23H‐porphine under solvothermal conditions. The structure of this copper porphyrin was characterized by single‐crystal X‐ray crystallography and elemental analysis. The porphyrin macrocycle shows a distorted saddle geometry, with the four pyrrole rings slightly distorted in an alternating mode either upwards or downwards. The copper ions show three‐coordinated triangular and four‐coordinated square‐planar geometries. Every copper–porphyrin unit connects to 12 others via four μ₄‐bridging Cu₂Cl moieties to complete the three‐dimensional framework of compound 1 , with isolated CuCl₂(H₂O) units located in the voids. This copper porphyrin displays a red photoluminescence. Electrochemical measurements showed that compound 1 has two redox waves (E_1/2 = ?160 and 91 mV).     

Nickel(II) Complex of N4 Schiff Base Ligand as a Building Block for a Conducting Metallopolymer with Multiple Redox States

Metal–ligand interactions in monomeric and polymeric transition metal complexes of Schiff base ligands largely define their functional properties and perspective applications. In this study, redox behavior of a nickel(II) N₄-anilinosalen complex, [NiAmben] (where H₂Amben = N,N′-bis(o-aminobenzylidene)ethylenediamine) was studied by cyclic voltammetry in solvents of different Lewis basicity. A poly-[NiAmben] film electrochemically synthesized from a 1,2-dichloroethane-based electrolyte was investigated by a combination of cyclic voltammetry, electrochemical quartz crystal microbalance, in situ UV-Vis spectroelectrochemistry, and in situ conductance measurements between −0.9 and 1.3 V vs. Ag/Ag⁺. The polymer displayed multistep redox processes involving reversible transfer of the total of ca. 1.6 electrons per repeat unit, electrical conductivity over a wide potential range, and multiple color changes in correlation with electrochemical processes. Performance advantages of poly-[NiAmben] over its nickel(II) N₂O₂ Schiff base analogue were identified and related to the increased number of accessible redox states in the polymer due to the higher extent of electronic communication between metal ions and ligand segments in the nickel(II) N₄-anilinosalen system. The obtained results suggest that electrosynthesized poly-[NiAmben] films may be viable candidates for energy storage and saving applications.     

Electrochemical,microscopic, and EQCM studies of cathodic electrodeposition of ZnO/FAD and anodic polymerization of FAD films modified electrodes and their electrocatalytic properties

Two kinds of chemically modified electrodes were prepared. In the first type of electrodes, zinc oxide (ZnO) and flavin adenine dinucleotide (FAD) molecules were deposited onto the glassy carbon-, gold-, and SnO₂-coated glass electrodes by using cyclic voltammetry from the bath solution containing aqueous 0.1 M zinc nitrate, 0.1 M sodium nitrate, and 1 × 10⁻⁴ M FAD. It was called as ZnO/FAD modified electrodes. The second type of modified electrode was prepared by the electropolymerization method. Electrochemical polymerization of FAD was carried out from the acidic solution containing 1 × 10⁻⁴ M FAD monomers onto electrode surfaces. This poly(FAD)-modified electrode yields a new redox couple in addition to the monomers redox couple. The influence of the concentrations, pH, and electrocatalytic properties of the ZnO/FAD- and poly(FAD)-modified electrodes are investigated by means of the in situ technique electrochemical quartz–crystal microgravimetry (EQCM) combined with cyclic voltammetry and the ex situ technique scanning electron microscopy. From these studies, it appears that the cathodic deposition of ZnO/FAD-modified electrodes gives only one redox couple, and the anodically polymerized FAD film-modified electrodes gives two reversible redox couples. The pH dependence of the redox responses were investigated and the kinetics of electron transfer was evaluated. In addition, the EQCM technique was employed to follow the deposition process of both kinds of modified electrodes in real time as well as the characteristics of the charge transfer associated with the surface-confined redox-active couples. The electrocatalytic activity of the poly(FAD)-modified electrode towards the reduction of hydrogen peroxide and the oxidation of dopamine and ascorbic acid was explored. The important electrocatalytic properties of poly(FAD)-modified electrode were observed for simultaneous separation of dopamine and ascorbic acid in neutral solution. This poly(FAD)-modified electrode has several advantages than the previously reported FAD-modified electrodes.     

Controllable synthesis of NiC2O4·2H2O nanorods precursor and applications in the synthesis of nickel-based nanostructures

A controllable synthesis of NiC₂O₄·2H₂O nanorods precursor was obtained via the microemulsion-mediated solvothermal method and a further synthesis of β-Ni(OH)₂ nanorods, nickel oxide (NiO) sub-microtubes, Ni nanospheres and flower-like nickel complexes nanostructures by using the precursor. The morphologies and crystalline structures were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and the X-ray powder diffraction (XRD). The morphologies and sizes of the precursors can be readily tuned by adjusting experimental parameters of the reverse microemulsion system. The synthesized β-Ni(OH)₂ nanorods composed of fine nanosheets shown excellent electrochemical performance as an electrode material in rechargeable battery systems.     

Electrochemical investigation of a novel metalloporphyrin intercalated layered niobate modified electrode and its electrocatalysis on ascorbic acid

Cationic iron (III) tetrakis-5, 10, 15, 20-(N-methyl-4-pyridyl) porphyrin (Fe^IIITMPyP) was intercalated into layered semiconductor KNb₃O₈ by ion-exchange method. The target product was characterized by XRD, Fourier transform infrared, UV–vis, and TGA. Fe^IIITMPyP forms an inclined monolayer between Nb₃O₈ ^? nanosheets and endues the nanocomposite with excellent electrochemical catalytic activities. The target nanocomposite modified glass carbon electrode shows good electrocatalytic activities for the oxidation of ascorbic acid (AA); the catalytic mechanism was proposed. Differential pulse voltammetric technique was used for detection of AA in neutral aqueous solution; a detection limit of 4.2?×?10^?5 M was obtained, and the modified electrode showed good reproducibility in electrochemical detection.