Nucleophilic aromatic substitution for heteroatoms: an oxidative electrochemical approach

The nucleophilic aromatic substitution for heteroatom through electrochemical oxidation of the intermediate sigma-complexes (Meisenheimer complexes) in simple nitroaromatic compounds is reported for the first time (NASX process). The studies have been carried out with hydride, cyanide, fluoride, methoxy, and ethanethiolate anions and n-butylamine as a nucleophile, at the cyclic voltammetry (CV) and preparative electrolysis level. The cyclic voltammetry experiments allow for detection and characterization of the sigma-complexes and they have led us to a proposal for the mechanism of the oxidation step. Furthermore, the power of the CV technique in the analysis of the reaction mixture throughout the whole chemical and electrochemical process is described.     

Electrochemical Studies of Eight New Divalent Transition Metal Benzenesulphonate Ternary Complexes with 1,10-Phenanthroline

The electrochemical properties of eight new divalent transition metal benzenesulphonate complexes with 1, 10-phenanthroline in different solvents and supporting electrolytes were investigated by means of cyclic voltammetry(CV). Based on the CV data the influences of various coordination modes on the electrochemical behavior of the complexes were discussed. The diffusion coefficient Dc and rate constant k, of those complexes in DMF systems were estimated according to CV and the results show that these processes were all quasi-reversible.     

Polystyrene sulphonate wrapped multiwalled carbon nanotubes modified graphite electrode for simultaneous determination of ascorbic acid, dopamine and uric acid

Graphite electrode is modified by casting multi-walled carbon nanotubes (MWCNTs) wrapped with polystyrene sulphonate (PSS) onto the surface of the bare graphite electrode. The modified electrode was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The behavior of the modified electrode towards the oxidation of ascorbic acid (AA), dopamine (DA) and uric acid (UA) has been determined by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CA). The modified electrode showed better electrocatalytic activity towards AA, DA and UA compared to bare graphite electrode. The electrochemical oxidation signals of AA, DA and UA are well separated into three distinct peaks with peak potential difference of 222, 128 and 350 mV between AA-DA, DA-UA and AA-UA respectively in CV studies and corresponding peak potential separation in DPV are 228, 120 and 348 mV. This modified electrode was successfully used for simultaneous determination of AA, DA and UA in ternary mixture.     

α-氨基肟配合物[M(Ⅱ)(PnAO)-H]的循环伏安研究

利用循环伏安法研究了脂族配合物〔Ｍ（Ⅱ）（ＰｎＡＯ）－Ｈ〕＾＋（Ｍ＝Ｃｏ，Ｎｉ，Ｃｕ，Ｐｄ）的氧化还原行为，得到了相应的电化学参数，提出了电化学－化学偶联过程的反应机理。讨论了不同金属离子及溶液的ｐＨ值对类芳香金属配合物生成的影响，阐明了这类化合物形成的动力学因素。     

Electrochemical investigations of oligomers and polymers containing ruthenium- and iron-arene complexes

Cyclic voltammetry was employed to investigate the electrochemical behavior of numerous cyclopentadienyliron (CpFe⁺) and pentamethyl-cyclopentadienylruthenium (Cp*Ru⁺) coordinated oligomers and polymers. The electrochemical behavior of the iron systems indicated the cyclopentadienyliron complexes had isolated redox centers and that changes in the reversibility of the redox couple occurred with changes in solvent and temperature. In contrast, the monometallic ruthenium systems showed large peak separations that suggested slow kinetics on the CV timescale. The cyclic voltammograms of the larger ruthenium-containing oligomers and polymers showed multiple redox steps indicating complex electrochemical behavior.     

A novel lable-free electrochemical immunosensor for carcinoembryonic antigen based on gold nanoparticles-thionine-reduced graphene oxide nanocomposite film modified glassy carbon electrode

In this paper, gold nanoparticle-thionine-reduced graphene oxide (GNP-THi-GR) nanocomposites were prepared to design a label-free immunosensor for the sensitive detection of carcinoembryonic antigen (CEA). The nanocomposites with good biocompatibility, excellent redox electrochemical activity and large surface area were coated onto the glassy carbon electrode (GCE) surface and then CEA antibody (anti-CEA) was immobilized on the electrode to construct the immunosensor. The morphologies and electrochemistry of the formed nanocomposites were investigated by using scanning electron microscopy (SEM), ultraviolet-visible (UV-vis) spectrometry, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). CV and differential pulse voltammetry (DPV) studies demonstrated that the formation of antibody-antigen complexes decreased the peak current of THi in the GNP-THi-GR nanocomposites. The decreased currents were proportional to the CEA concentration in the range of 10-500 pg/mL with a detection limit of 4 pg/mL. The proposed method was simple, fast and inexpensive for the determination of CEA at very low levels.     

Well-dispersed multi-walled carbon nanotube/polyaniline composite films

Multi-walled carbon nanotube (MWNT)/polyaniline (PANI) composite films with good uniformity and dispersion were prepared by electrochemical polymerization of aniline containing well-dispersed MWNTs. The results of transmission electron microscopy (TEM) show that aniline can be used to solve MWNTs via formation of donor–acceptor complexes. Scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) revealed that the well arrangement of PANI-coated MWNTs in these films facilitated improved electron and ion transfer relative to pure PANI films and this may be due to the strong interaction between MWNTs and PANI.     

脱氧核糖核酸在汞膜电极上的电化学行为

首次在汞膜电极上利用循环安，微分脉冲和交流伏安法研究脱氧核糖核酸（ＤＮＡ）的电化学行为，结果表明汞膜电极作为一类固体电极可应用于负电位区ＤＮＡ电化学行为的研究。同时结合凝胶电泳和ＵＶ光谱法，研究了用纯高氯酸处理的ＤＮＡ的氧化还原特性，结果表明纯高氯酸可经起ＤＮＡ的变性和降解，纯高氯酸不适宜ＤＮＡ的变性处理。     

甲氧苄啶在多壁碳纳米管-Nafion修饰电极上的电催化氧化及电分析方法

用循环伏安法(CV),计时库仑法(CC),计时电流法(CA),线性扫描伏安法(LSV)及电流-时间曲线研究了甲氧苄啶(trimethoprim, TMP)在碳纳米管-Nafion修饰电极(MWCNTs-Nafion/GCE)上的电化学行为,电化学动力学性质以及电分析方法.结果表明,TMP在GCE上有一个极弱的氧化峰,而在MWCNTs-Nafion/GCE上出现一个敏锐的氧化峰,表明MWCNTs-Nafion/GCE对TMP电化学氧化具有良好的催化作用.在扫描速度为10～800 mV/s时其氧化峰电流与扫描速度平方根(v1/2)呈良好线性关系,表明TMP在MWCNTs-Nafion/GCE上的伏安行为是受扩散控制的电化学过程.TMP在MWCNTs-Nafion/GCE上氧化峰电流与浓度在5.0×10-6～1.0×10-3 mol/L范围内呈良好线性关系;检出限为6.6×10-7 mol/L;RSD在0.75%～1 69%之间;加标回收率在98.1%～101.1%之间.本方法简便快捷,测定结果令人满意,可用于TMP的电化学定量测定.     

Electrochemical Aptasensor Based on ZnO Modified Gold Electrode

We developed an electrochemical thrombin aptasensor based on ZnO nanorods functionalized by electrostatically adsorption of 30‐mer DNA aptamers. The sensor surface was characterized by AFM and SEM. The surface layer assembling was optimized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) with ferricyanide ions as redox markers. The peak current of the ferricyanide and the charge transfer resistance gradually decreased with increasing concentration of thrombin in the range from 3 pM to 100 nM due to formation of aptamer‐thrombin complexes and slower diffusion of the marker ions through the surface layer. At optimal conditions, a limit of detection (LOD) of 3 pM for EIS measurements and 10 pM for CV response was calculated from the S/N=3.     

聚吡咯/碳纳米管分子印迹修饰电极对槲皮素的选择性测定

制备了一种新颖的可对槲皮素分子进行选择性测定的分子印迹聚合物膜修饰电极.在碳纳米管(CNT)独特的结构和力学性能作用下,以吡咯(Py)为功能单体,槲皮素为模板分子,电聚合方法制备了槲皮素的分子印迹聚合物膜修饰电极(PPy/CNT/GCEMIP).用电化学交流阻抗法研究了该修饰电极的界面性质,用循环伏安法和差分脉冲伏安法...     

Functionalized-graphene modified graphite electrode for the selective determination of dopamine in presence of uric acid and ascorbic acid

Graphene is chemically synthesized by solvothermal reduction of colloidal dispersions of graphite oxide. Graphite electrode is modified with functionalized-graphene for electrochemical applications. Electrochemical characterization of functionalized-graphene modified graphite electrode (FGGE) is carried out by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The behavior of FGGE towards ascorbic acid (AA), dopamine (DA) and uric acid (UA) has been investigated by CV, differential pulse voltammetry (DPV) and chronoamperommetry (CA). The FGGE showed excellent catalytic activity towards electrochemical oxidation of AA, DA and UA compared to that of the bare graphite electrode. The electrochemical oxidation signals of AA, DA and UA are well separated into three distinct peaks with peak potential separation of 193mv, 172mv and 264mV between AA-DA, DA-UA and AA-UA respectively in CV studies and the corresponding peak potential separations in DPV mode are 204mv, 141mv and 345mv. The FGGE is successfully used for the simultaneous detection of AA, DA and UA in their ternary mixture and DA in serum and pharmaceutical samples. The excellent electrocatalytic behavior of FGGE may lead to new applications in electrochemical analysis.     

Electrooxdation of Tricarbonyl(N,N-Diphenylcyclohexadienecarboxamide)Iron Complexes. Reversibility of Electron Transfer and Free Energy Change

Qualitative and quantitative criteria of irreversibility of electron transfer in cyclic voltammetry (CV) of tricarbonyl(N,N-diphenylcyclohexadienecarboxamide)iron complexes were investigated. The measurement of the heterogeneous rate constants for electron transfer according to CV data over an extended range of free energy change ( ΔG) for these complexes are described. Kinetic analyses of the electrochemical technique demonstrates that when the applied potential exceeds the standard potential E°, the experimental rate constant k_e represents an accurate measurement of the intrinsic rate constant k₁ for electron transfer. However, as the applied potential is less than E°, the reversibility of the electron-transfer process becomes increasingly more important, and the rate constants for reverse electron transfer k_-t and decomposition k₂ of the electrogenerated intermediate have to be taken into account.     

丹皮酚在聚苏丹红Ⅲ/GC电极上的电化学行为及测定

应用交流阻抗法和循环伏安法表征聚苏丹红Ⅲ/GC电极,并研究丹皮酚在该聚合物电极上的电化学行为. 实验表明,聚苏丹红Ⅲ/GC电极对丹皮酚具有良好的电催化作用,在3.0*10^-7 ~ 2.2*10^-5 mol·L^-1浓度范围内,其差示脉冲伏安峰电流随浓度变化呈良好的线性关系,检测限为5.0*10^-8 mol·L^-1. 该法可用于实际样品中丹皮酚的测定,结果令人满意.     

Electrochemical formation of multilayered NiO film/Ni foam as a high-efficient anode for methanol electrolysis

Journal of Solid State Electrochemistry - A multilayered NiO film is fabricated on 3D Ni foam (NF) substrate via electrochemical cyclic voltammetry (CV) as a high-efficient methanol oxidation...     

Effects of Sodium Sulfate as Electrolyte Additive on Electrochemical Performance of Lead Electrode

Sodium sulfate as an electrolyte additive was studied via electrochemical methods including linear sweep voltammetry(LSV), cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS) to deeply understand its effect on the hydrogen evolution current and overpotential as well as the formation and structure of anodic passivation films on lead surface during the redox processes. The results achieved will be valuable to improve the cycle life and maintenance-free properties of lead-acid batteries.     

Li_2CO_3添加剂对石墨电极性能的影响

运用电化学阻抗谱(EIS)和循环伏安法(CV)研究了在1mol/LLiPF6-EC(碳酸乙烯酯):DMC(碳酸二甲酯)电解液中添加Li2CO3对石墨电极性能的影响及机制.CV研究结果表明,在1mol/LLiPF6-EC:DMC电解液中添加Li2CO3能够有效抑制石墨电极首次充放电过程中碳酸乙烯酯(EC)的单电子还原过程,即还原分解产生乙烯和碳酸锂的过程,进而改善石墨电极的电化学循环性能.EIS研究结果表明,在添加Li2CO3的1mol/LLiPF6-EC:DMC电解液中,石墨电极表面的固体电解质相界面膜(SEI膜)具有较强的黏弹性,可以更好地适应锂离子嵌入过程中石墨颗粒体积的微小变化,从而使锂离子的嵌入过程更容易进行.     

基于纳米金／壳聚糖掺杂碳纳米管修饰金电极非标记免疫传感器的研究

应用吸附法将羊抗人IgG抗体直接固定于纳米金(GNPs)/壳聚糖(Chit)掺杂碳纳米管(CNTs)修饰的金电极表面,制备了用于人IgG抗原检测的非标记电化学免疫传感器.利用循环伏安法和交流阻抗研究了修饰电极表面的电化学特性,用差分脉冲伏安法研究了测试底液的pH值对免疫传感器性能的影响.实验表明,在含不同浓度人IgG的...     

恒电位氧化改性石墨毡及其氧还原电极的电化学性能

分别采用循环伏安改性法和恒电位氧化法对石墨毡进行改性处理,并采用循环伏安法对其电化学性能进行研究,实验结果表明,恒电位氧化改性较循环伏安改性的石墨毡有较好的氧还原活性。通过XRD、FTIR、接触角和CV针对恒电位氧化处理石墨毡进行了进一步的测试。测试结果显示,随恒电位氧化时间的增加,石墨毡表面亲水性含氧官能团增加,润湿性增强。恒电位氧化改性处理25 min的石墨毡氧还原峰电位及电流密度分别为~-0.43 V和~0.003 4 mA·cm^-2,显示出很好的电化学催化性能。基于以上结果,恒电位氧化法改性处理能够极大提高石墨毡的氧阴极活性。     

基于羧基化碳纳米管修饰电极伏安法同时测定痕量锢和铝

基于羧基化多壁碳纳米管(c-MWCNT),制备了可同时测定In3+和Al3+的新型碳材料修饰电极.利用循环伏安法(CV)和交流阻抗法(EIS)对此修饰电极进行了表征,用线性扫描伏安法(LSV)研究了In3+与Al3+共存于修饰电极上的电化学行为.与裸玻碳电极相比,新型碳材料修饰电极的电化学活性得到很大提高;In3+与A...