二茂铁及其与DNA复合物的电化学行为

在Tris-NaCl(pH=7.2)缓冲溶液中, 应用循环伏安法、微分脉冲伏安法、旋转圆盘电极实验、电化学阻抗谱等技术研究了二茂铁在旋转碳纳米管(CNT)修饰电极上的电化学行为及其与小牛胸腺DNA的相互作用. 结果表明, 二茂铁及其与双链DNA的电活性产物在静止的CNT修饰电极上均呈现一对基本可逆的氧化还原峰；在旋转电极上呈现出明显的极限扩散电流, 电化学阻抗谱呈现一个压扁的半圆. 二茂铁与DNA的作用在扩散控制过程中表现为峰电流和极限扩散电流随DNA浓度增大而减小；电化学控制过程则表现为电化学反应电阻随DNA浓度增大而增大, 条件电位下的速度常数也有一定程度的减小.     

纳米氧化亚铜固载亚甲兰复合膜修饰玻碳电极的电化学性质及其对多巴胺的电催化

用十六烷基三甲基溴化铵为软模板制备了纳米氧化亚铜晶须,利用XRD和TEM进行表征。研究了纳米Cu2O-Nafion膜修饰玻碳电极的电化学性质,结果表明,纳米氧化亚铜在电极上表现出一对较为可逆的氧化还原峰,对应于Cu(Ⅱ)/Cu(Ⅰ)的氧化还原,峰电流与扫速成正比,表明纳米氧化亚铜在电极表面的电化学受表面控制。研究发现在亚甲基兰为媒介的情况下电极对多巴胺的催化能力进一步提高。在此电极上多巴胺呈现一对响应良好的准可逆氧化还原峰,峰电位差106 mV,峰电流大大提高,氧化峰电位大大降低,表现出良好的电催化作用。该电极可以在抗坏血酸存在下测定多巴胺。     

二茂铁/L-半胱氨酸修饰电极的电化学行为及电催化性能

利用配对试剂将二茂铁酰胺键合在L-半胱氨酸自组装单层膜(SAM)表面, 制成稳定的二茂铁/L-半胱氨酸修饰电极, 该电极在pH 7.0的磷酸盐缓冲液中有一对很好的氧化还原峰. 运用循环伏安法和交流阻抗谱详细研究了修饰电极的电化学行为, 测得电子转移系数为0.66, 表观电极反应速率常数为6.86 s-1. 该修饰电极对肾上腺素有很好的催化作用, 峰电流与肾上腺素浓度在2.0×10-7～1.0×10-5 mol·dm-3范围内呈现良好的线性关系.     

槲皮素在多壁碳纳米管修饰碳糊电极上的电化学行为及其与脱氧核糖核酸的相互作用

采用循环伏安法和差分脉冲伏安法研究了槲皮素在多壁碳纳米管修饰碳糊电极上的电化学行为。结果表明:槲皮素多壁碳纳米管修饰碳糊电极上均能产生一对氧化还原峰,氧化峰电位和还原峰电位分别为0.488,0.348V,氧化峰电流是裸多壁碳纳米管修饰碳糊电极氧化峰电流的5.3倍,多壁碳纳米管对槲皮素有良好的催化作用。槲皮素在修饰电极上的电化学反是2质子,2电子反应过程。采用中性红为探针研究了槲皮素与脱氧核糖核酸之间的相互作用,结果表明两者可通过嵌插方式相结合。     

比例型电化学生物传感器检测恙虫病DNA的研究

本研究以二茂铁修饰的发卡型探针DNA(HP)作为内参比探针分子,恒电位法在玻碳电极上沉积金颗粒作为工作电极,含有亚甲基蓝修饰的辅助团(AS)用于信号放大,据此建立了一种比例型检测恙虫病DNA的电化学方法。测试结果表明,该方法具有较好的选择性和检出限,线性范围达到0.1 fM～1.0μM,AS氧化峰电流I_(MB)与HP的峰电流I_(Fc)的比值与恙虫病DNA浓度呈较好的线性关系。     

电化学还原的氧化石墨烯修饰电极检测L-色氨酸

制备了氧化石墨烯修饰玻碳电极,并运用循环伏安法对氧化石墨烯进行了直接的电化学还原,研究了L-色氨酸在该电化学还原的氧化石墨烯修饰玻碳电极上的电化学行为。结果表明,L-色氨酸在该修饰电极上其氧化峰电流与裸玻碳电极相比增大了7.1倍,且峰电位负移80mV。利用差分脉冲伏安法,在pH=6.5的磷酸盐缓冲溶液中测定L-色氨酸,氧化峰电流与其浓度在0.4～65.0μmol/L范围内呈良好的线性关系,相关系数为0.998,方法检出限为0.2μmol/L。     

纳米银自组装电极的制备及对高氯酸二茂铁的电化学响应

采用自组装的方法制备了纳米银粒子修饰金电极,并运用循环伏安法、交流阻抗谱探讨了该电极的电化学特性.研究了高氯酸二茂铁在该修饰电极上的直接电化学行为.实验结果表明,高氯酸二茂铁在该修饰电极上具有良好的电流响应.用示差脉冲法测定高氯酸二茂铁,其氧化峰电流与浓度在4.0×10-6～5.0×10-4 mol/L范围呈良好线性关系,线性方程为:Ip(μA)=0.0236c(μmol/L)-0.0975,线性相关系数为0.9982,检出限为2.3×10-7 mol/L(信噪比为3).     

检测痕量Hg~(2+)的DNA电化学生物传感器

通过自组装方法将修饰有二茂铁基团的富T序列DNA分子(DNA-Fc)固定在金电极表面,得到了一种基于DNA修饰电极的电化学汞离子(Hg2+)传感器.当溶液中有Hg2+存在时,Hg2+可与修饰电极上DNA的T碱基发生较强的特异结合,形成T-Hg2+-T发卡结构,使DNA分子构象发生改变,其末端具有电化学活性的二茂铁基团远离电极表面,电化学响应随之发生变化.示差脉冲伏安法(DPV)结果显示:DNA末端二茂铁基团的还原峰在0.26V(vs饱和甘汞电极(SCE))附近,峰电流随溶液中Hg2+浓度的增加而降低;Hg2+浓度范围在0.1nmol·L-1-1μmol·L-1时,电流相对变化率与Hg2+浓度的对数呈现良好的线性关系.该修饰电极对Hg2+的检测限为0.1nmol·L-1,可作为痕量Hg2+检测的电化学生物传感器.干扰实验也表明,该传感器对Hg2+具有良好的特异性与灵敏度.     

毛蕊异黄酮在金电极上的电化学行为及其与DNA相互作用的光谱与电化学研究

采用光谱法和电化学方法研究了毛蕊异黄酮(CYS)与DNA的作用。CYS与DNA作用后的紫外-可见吸收光谱,表现出一定的减色效应,其荧光光谱则表现出增色效应,表明两者能够发生相互作用。电化学研究表明在p H 4.4的HAc-Na Ac缓冲溶液中,CYS在金电极上有一对氧化还原峰,在0.35~7.04μmol/L和7.04~70.36μmol/L的浓度范围内,CYS的氧化峰电流与其浓度呈良好的线性关系。CYS与DNA作用后,CYS的氧化峰电流显著减小,峰电位发生正移。根据DNA加入前后,峰电流及峰电位的变化,计算了CYS与DNA相互作用前后的动力学参数。     

二硫键桥联双二茂铁芳胺修饰纳米金电极

对或间二茂铁苯胺与对-乙酰硫基苯甲醛反应得到两个席夫碱,硼氢化钠还原席夫碱碳氮双键的同时对乙酰硫基脱保护,合成了两个二硫键桥联双二茂铁芳胺类化合物,p-(Fc-Ph-NH-CH2-Ph-S)2和m-(Fc-Ph-NHCH2-Ph-S)2。将化合物自组装到电沉积纳米金的玻碳电极上,制得稳定的修饰电极,此电极在LiClO4的乙腈溶液中有一对氧化还原峰,用循环伏安法和交流阻抗谱法研究了修饰电极的电化学性质,化合物m-(Fc-PhNH-CH2-Ph-S)2修饰纳米金/玻碳电极对芦丁有催化氧化作用。     

Role of palladium in the redox electrochemistry of ferrocene monocarboxylic acid encapsulated within ORMOSIL networks

We report herein the effect of palladium on the redox electrochemistry of ferrocene monocarboxylic acid encapsulated within an organically modified sol-gel glass network (ORMOSIL). It has been found that amount of palladium and its geometrical distribution significantly alter the redox electrochemistry of FcMCA. The geometrical distribution of palladium has been controlled by two methods: (i) palladium is allowed to link within nanostructured network of the ORMOSIL which was subsequently availed from the reactivity of palladium chloride and trimethoxysilane; (ii) palladium powder is encapsulated together FcMCA thus allowing the presence of palladium within the nanoporous domain. The content of palladium is varied by controlling the reaction dynamics of palladium chloride and trimethoxysilane interaction. For this we initially allowed to trigger hydrolysis, condensation and poly-condensation of trimethoxysilane and dimethyldiethoxysilane in acidic medium and subsequently partially dried ORMOSIL film was allowed to interact with palladium chloride. Even with partially dried ORMOSIL derived from trimethoxysilane and dimethyldiethoxysilane undergoes rapid interaction with palladium chloride and the transparent color of ORMOSIL changed to a black colour due to the formation of palladium silicon linkage. The palladium-silicon linkage has been identified by NMR, UV-VIS and transmission electron spectroscopy. The electrochemistry of FcMCA encapsulated within such an ORMOSIL matrix has been studied. Excellent redox electrochemistry of ferrocene monocarboxylic acid having peak potential separation tending to 0 for a multilayered electrode was investigated. The palladium content has been found to affect the redox electrochemistry of ferrocene as well as electrocatalytic efficiency of new ORMOSIL material. The electroanalysis of NADH is reported. The modified electrode is very sensitive to NADH with lowest detection limit of < 1 microM.     

Triple Component Carbon Epoxy pH Probe

A pH probe based on a carbon‐epoxy electrode design is discussed. The electrode consists of three redox active components within a carbon epoxy matrix. These are the pH sensitive species anthraquinone and phenanthrenequinone, along with the pH insensitive ferrocene reference compound. The values of the peak potentials when combined are shown to shift by 120 mV/pH unit at 25 °C with respect to the ferrocene reference potential.     

An electrochemical immunosensor using ferrocenyl-tethered dendrimer

We report here an enzyme-amplified, sandwich-type immunosensor for detecting the biospecific interaction between an antibody and antigen using redox mediation. We employed biotin/anti-biotin IgG as a model immunosensing pair. Partially ferrocenyl-tethered dendrimer (Fc-D), whose ferrocene moiety acts as a redox mediator, was immobilized to the electrode surface by covalent binding between the dendrimer amines and the carboxylic acids of a self-assembled monolayer. The unreacted amines of the immobilized Fc-D were modified with biotin groups to allow the specific binding of goat anti-biotin IgG. Rabbit anti-goat IgG-conjugated alkaline phosphatase was bound to goat anti-biotin IgG to catalyze conversion of p-aminophenyl phosphate monohydrate to p-aminophenol. This product is oxidized to quinoimide by the reduction of ferrocenium back to ferrocene, producing an electrocatalytic anodic current. Cyclic voltammograms and surface plasmon resonance experiments showed that the binding of nonspecific proteins is not significant on the biotinylated Fc-D surface. We also examined the change in peak current according to the concentration of anti-biotin IgG and found that the detection range of this immunosensing scheme is between 0.1 and 30 microg mL(-1).     

Remarkable Electrochemical Responses of Ferrocene/NaY Zeolite Composite modified Electrode Based on Hydrophobic Ionic Liquid

The ferrocene/NaY zeolite composites (Fc/NaY) are introduced on the surface of a glassy carbon electrode together with the hydrophobic ionic liquid 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIMPF₆). The modified electrode thus constructed exhibits a pair of reversible redox peaks corresponding to ferrocene. Additionally the peak separation remains almost constant (58–75 mV) and the value of the ratio i_pa/i_pc is close to 1 for scan rates in the range from 10 to 1000 mV s^?1. The effects of the scan rate, aqueous supporting electrolytes, hydrophobic ionic liquid and the contents of ferrocene encapsulated by electrochemistry are investigated. The extrazeolite electron transfer process is discussed. Furthermore, the Fc/NaY/IL‐modified electrode shows good mediation towards oxidation of ascorbic acid, dopamine, hydroquinone, and catechol.     

Voltammetric Behavior of the Alizarin Red S Interaction with DNA and Damage to DNA

The electrochemical behavior and the interaction of alizarin red S (ARS) with calf thymus DNA was investigated on a bare glassy carbon electrode (GCE) and DNA modified GCE (DNA/GCE), respectively. ARS showed a pair of redox peaks at ?0.445 V and ?0.414 V on a bare GCE. On addition of DNA into the ARS solution, the peak current of ARS decreased and the peak potential positively shifted, but without new redox peaks appeared. The ARS reduction peak current increased with immersion time on a DNA/GCE. The results showed that ARS could interact with DNA molecules by intercalative binding mode. The equilibrium constant, binding number and the ratio of binding constant for oxidized and reduced ARS forms were obtained. The DNA damage was directly detected by appearance of guanosine and adenosine bases oxidation signal. The influence of experimental conditions on DNA damage extent was discussed in detail.     

Polymer-based bilayer interfaces for electrochemical rectification

In this paper, the electrochemical current rectification phenomenon exhibited at an electrochemical interface constituted by a glassy carbon electrode covered with a bilayer of polymer films is discussed. The authors have shown that Methylene Blue (MB) redox species can be confined to a very thin insulating polymer film formed from orthophenylene diamine. The poly(opd) film exhibited excellent blocking properties to redox molecules in solution. On the other hand, the insulating poly(opd) film trapped with MB could mediate electron transfer between the redox molecules in solution and the electrode. Further, a second polymeric layer (Nafion film) trapped with ferrocene redox species was formed as the outer layer over the inner poly (opd) film containing MB. This bilayer-modified electrode, due to the significant difference in the redox potentials of the MB and ferrocene species immobilized in the inner and outer layers, respectively, exhibits unidirectional current flow and the results of the voltammetric investigations on the modified electrodes are described in this communication.     

二茂铁基超支化聚氨酯的电化学性能

通过循环伏安法(CV)测定了二茂铁基超支化聚氨酯(HAPE-Fc)的电化学性能.结果表明:HPAE-Fc表现为单对氧化还原峰,在二茂铁接枝到超支化聚氨酯上以后,二茂铁基团依然保持着自身的氧化还原独立性,具有较强的电子转移速率,这是其具有电化学特性和催化作用的前提条件.通过分析扫描速率与HPAE-Fc电化学行为之间的关系,发现HPAE-Fc的电极过程既受扩散控制,同时也受电极反应的控制.     

隐丹参酮的电化学性质及其与DNA相互作用的研究

利用循环伏安法(CV)、线性扫描伏安法(LSV)、方波伏安法(OSWV)等电化学技术研究了隐丹参酮在玻碳电极(GCE)上的电化学氧化过程,并用计时电量法和恒电位库仑电解法等对其在电极表面的吸附行为及氧化还原机理进行了探讨.此外利用自组装DNA修饰玻碳电极研究了隐丹参酮与DNA之间的相互作用.     

Cyclic Voltammograms of Ferrocene on Multi‐Walled Carbon Nanotubes (MWCNTs)‐Modified Edge Plane Pyrolytic Graphite (EPPG) Electrode in Room Temperature Ionic Liquids (RTILs) of 1‐Ethyl‐3‐Methylimidazolium Tetrafluoroborate (EMIBF4)

In this work, the electrochemical behavior of ferrocene (Fc) was investigated by cyclic voltammetry (CV) in room temperature ionic liquids (RTILs) of 1‐ethyl‐3‐methylimidazolium tetrafluoroborate (EMIBF₄) on glass carbon (GC), edge plane pyrolytic graphite (EPPG) and multi‐walled carbon nanotube (MWCNTs)‐modified EPPG electrodes, respectively. The results demonstrated that on GC electrode, pairs of well‐defined reversible peaks were observed, while for the electrode of EPPG, the peak potential separation (ΔE_p) is obviously larger than the theoretical value of 59 mV, hinting that the electrode of EPPG is distinguished from the commonly used electrode, consistent with the previous proposition that EPPG has many “defects”. To obtain an improved electrochemical response, multi‐walled carbon nanotubes (MWCNTs) were modified on the electrode of EPPG; the increased peak current and promoted peak potential separation not only proved the existence of “defects” in MWCNTs, but also supported that “creating active points” on an electrode is the main contribution of MWCNTs. Initiating the electrochemical research of Fc on the MWCNTs‐modified EPPG electrode in RTILs and verifying the presence of “defects” on both EPPG and MWCNTs using cyclic voltammograms (CVs) of Fc obtained in RTILs of EMIBF₄, is the main contribution of this preliminary work.