电化学交流阻抗技术表征自组装多层膜

采用电化交流阻抗技术对一种新型电极表面修饰的自组装多层膜进行表征,通过阻抗谱分析,得出电荷传递电阻和双电层电容与膜层数的关系,证明该多层膜随数增加具有均匀增长,结构致密等特性.     

偶氮苯衍生物自组装膜的表征及组装动力学

报导了4-正辛基-4′-（3－巯基丙氧基）偶氮苯（简称C8AzoC3）自组装膜（Self-AssembledMonolnyersSAMs）的表征及其自组装成膜动力学，接触角滴定、原子力显微镜（AFM）及电化学的实验结果表明，C8AzoC3分子在金表面自组装形成致密有序的流水性单分子膜，并且在电极上没有明显的电化学响应．通过控制组装时间，考察了偶氮苯自组装形成单分子膜的动力学过程，从接触角和电化学数据得到组装过程的速率常数kad为（1.2±0.2）×103mol-1·dm3·s－1；依据不同组装时间形成的自组装膜的特征循环伏安行为，提出了C8AzoC3分子在金表面自组装过程的动态模型．     

Electrochemical Impedance Study of Schiff Base by Means of Self-assembled Monolayer

Schiff base and its metal complex have attracted much attention because of their wide applications in biomedicine and their specific character in photochromic field1. Up to now, reports about Schiff base mainly covered its synthesis and structure2,3. To the best of our knowledge, there is no paper dealing with Schiff base using electrochemical impedance spectroscopy technique by forming self-assembled monolayer. The complexation of Schiff base with the transition metal ions has been confir…     

Elucidating the Influence of Electrical Potentials on the Formation of Charged Oligopeptide Self-Assembled Monolayers on Gold

Self-assembled monolayers (SAMs) based on oligopeptides have garnered immense interest for a wide variety of innovative biomedical and electronic applications. However, to exploit their full potential, it is necessary to understand and control the surface chemistry of oligopeptides. Herein, we report on how different electrical potentials affect the adsorption kinetics, stability and surface coverage of charged oligopeptide SAMs on gold surfaces. Kinetic analysis using electrochemical surface plasmon resonance (e-SPR) reveals a slower oligopeptide adsorption rate at more positive or negative electrical potentials. Additional analysis of the potential-assisted formed SAMs by X-ray photoelectron spectroscopy demonstrates that an applied electrical potential has minimal effect on the packing density. These findings not only reveal that charged oligopeptides exhibit a distinct potential-assisted assembly behaviour but that an electrical potential offers another degree of freedom in controlling their adsorption rate.     

Studies of Adsorption Kinetics and Defects of Self‐Assembled Thiol Monolayers on Gold by Capacitance Plane Plot

The capacitive property of an electrode/electrolyte interface can be described by complex capacitance. The capacitance plane plots (CPPs) of ideal polarized and kinetic controlled electrodes are derived based on the concept of complex capacitance. By using CPPs, the capacitance of electrode/electrolyte interface can be conveniently determined. In this work, CPPs obtained in ac impedance experiments are employed for the first time in studying the kinetics of adsorption process of the thiol monolayer. The coverage of octadecanethiol (ODT) monolayer on gold is examined as a function of adsorption time. The adsorption process of ODT molecules on gold exhibits two distinct phases: an initial rapid step followed by a slow one. The simple Langmuir model best explains our experimental data in the initial adsorption stage. CPPs and cyclic voltammetry (CV) indicate that, in the initial adsorption step, the ODT monolayer contains defects whose number decreases with the increasing of adsorption time.     

不同亲水性探针分子在金电极上硫醇自组装跨膜动力学研究

采用扫描电化学显微镜测定了不同亲水性氧化还原电对在硫醇修饰的金电极表面上的异相电子转移速率常数. 分别选择铁氰化钾[K3Fe(CN)6]和N,N,N',N'-四甲基-1,4苯二胺(TMPD)作为氧化还原探针,根据得到的反馈曲线拟合出异相电子转移速率常数. 比较这些速率常数可以看出, 修饰层对疏水性的TMPD分子显示出更好的穿透性. 通过一个简单的模型可以解释TMPD的穿透过程, 在TMPD电子隧穿的前后存在着单层膜和水溶液间的快速平衡, 而隧穿作为决速步骤, 其表观速率常数也比K3Fe(CN)6的大. 通过计算得到TMPD的隧穿因子β为1.2/CH2.     

Assessment of Defects and Collapsed Sites in Self-Assembled Alkanethiol Monolayer on Gold by Cyclic Voltammetry and A.C.Impedance

Thespontaneousself-assemblytechniqueprovidesaconvenientandpowerfultooltopreparecompactmonolayerswithwell-definedcomposition,structureandthicknessl.However,theexistenceofstrUcturaldefectsanddisorderinself-assemblymayinfluenceitspropertiesinmanyfields.Soitisincreasinglyclearthatthecharacterizationofdefectsisanimportantissuewhichneedstobeaddressedinmanyapplications.Thepurposeofthisworkistostudythedefectsand"collapsed"sitesinAulthiolmonolayerbycyclicvoltanunetryandelectrochemicalimpedancespectros…     

Amplified DNA Detection Sensitivity Using Streptavidin－Biotinylated Protein Complex： Characterization by Electrochemical Impedance Spectroscopy

Thioi-terminated oligonucleotide was immobilized to gold sur-face by self-assembly method. A novel amplification strategy was introduced for improving the sensitivity of DNA hybridiza-tion using biotin labeled protein-streptavidin network complex. This complex can be formed in a cross-linking network of molecules so that the amplification of the response signal will be realized due to the big molecular size of the complex. It could be proved from the impedance technique that this amplification strategy caused dramatic improvement of the detection sensitivi-ty. These results give significant advances in the generality and sensitivity as it is applied to biosensing.     

Functionalized Self-Assembled Monolayers on Gold as Binding Matrices for the Screening of Antibody-Antigen Interactions

Two different types of -substituted alkanethiol/disulfide compounds have been used to prepare monolayer architectures on gold serving as platforms for the immobilization of receptor probe molecules – antibodies. These are: (i) carboxylic acid alkanethiols post-reacted with amino biotin to generate streptavidin surfaces, and (ii) N-hydroxysuccinimide-terminated disulfide surfaces. The properties of the monolayers, with and without attached receptor probe molecules, were analysed using infrared spectroscopy, ellipsometry, fluorescence scanning and atomic force microscopy. Several experimental parameters, such as condensation reagents, additives, probe and target concentrations and immobilization time, were systematically varied to determine the dynamic range and to optimize the sensitivity and signal-to-noise ratio of the biochip platforms. Fluorescence screening using Cy5-labelled antigens finally demonstrated that both surfaces could be successfully employed to immobilize the antibodies. The pros and cons of the two approaches are also discussed.Received November 15, 2002; accepted March 25, 2003 Published online July 28, 2003     

Electrochemical Impedance Spectroscopy of 3 MeV Nickel Implanted into Steel

ABSTRACT

Impedance spectroscopy was used to study the corrosion of a nickel implanted steel sample. The dosaye was 5 × 10¹⁵ ions/cm² and the energy of the nickel ions was 3 MeV. The data from a Simple Randies circuit (R_p and C_dl) were used to explain the corrosion changes observed in a NACE National Association of Corrosion Engineers) Brine solution (used to emulate geothermal brine conditions) at pH 2.0 and 25°C in an air saturated solution. Iron concentrations measured by Induction Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) were used to calculate corrosion rates at various time intervals. Impedance spectroscopy^1,2 is an electrochemical technique which can be used to monitor corrosion and to our knowledge it has not been applied to implanted materials.     

自组装单分子膜在电化学电子转移过程中的应用

综述了自组装单分子膜作为模型体系在电化学电极过程中长程电子转移方面应用的一些重要研究成果。重点介绍了电子转移距离、电活性中心的微环境、膜表面分子的设计和状态等因素对长程电子转移的影响情况。展望了该领域今后的发展方向。     

Electrochemical Impedance Spectroscopy of Oxide Layers on the Titanium Surface

The method of electrochemical impedance spectroscopy is used to study oxide layers formed at the titanium surface by a variety of methods. The sample’s polarization permitted the isolation, in an impedance spectrum, of the response caused by the capacitance of the space-charge region, which obeys the Mott-Schottky dependence. It is established that the high-frequency portion of an impedance spectrum is defined by morphological peculiarities of the porous portion of coatings. Assumptions, concerning the nature of a time constant, which reveals itself in the region of low frequencies at polarizing biases, are made. Equivalent circuits, intended for modeling impedance spectra, are proposed. The circuits take into consideration the effect of the space-charge region, as well as the peculiarities of the structure and morphology of the oxide film formed at the titanium surface.__________Translated from Elektrokhimiya, Vol. 41, No. 8, 2005, pp. 963–971.Original Russian Text Copyright © 2005 by Gnedenkov, Sinebryukhov.     

铁表面自组装缓蚀功能膜的电化学阻抗谱研究

在铁表面自组装十四烷基胺膜.研究该膜在0.5 mol/LH2SO4溶液中对铁的缓蚀性能.电化学阻抗谱测试表明,随着组装时间的延长,缓蚀性能也随之增强,最大缓蚀效率为68.7%.而以十二烷基硫醇和十四烷基胺修饰的混合膜则更为致密、稳定,对铁的缓蚀能力也明显优于仅以十二烷基硫醇或十四烷基胺修饰的单一膜,其缓蚀效率可提高至78.2%.     

自组装膜结构与电化学行为的关系

报导了组装时间对４－乙氧基－４＇－Ｎ（２″－巯基－乙基）羧基酰胺－偶氮苯（Ｃ２ＡｚｏＣ２）自组装膜电化学行为的影响。接触角与界面电容的数据表明，组装时间的增长使自组装膜表面覆盖度增加。从循环伏安图中可以观察到氧化峰与还原峰之间的距离增大，同时计算得到的表观电极反应速率常数显著减小。基于偶氮苯基团的自身结构及其在电化学反应过程中所经历的构型改变，认为有序体系中组装结构的致密性阻碍偶氮苯基团的构型变化     

电吸附除氯过程的电化学阻抗谱及动力学研究

借助三电极体系, 基于电化学交流阻抗谱图, 提出了一种对已吸附Cl^-的活性炭再次吸附一个Cl^-弛豫时间的测定方法, 根据弛豫时间确定速率控制步骤 . 研究了阳极电势、 预处理时间和预处理浓度对电化学过程的影响, 基于得到的电化学交流阻抗谱图上的参数, 求出不同条件下电吸附Cl^-的弛豫时间及覆盖度. 结果表明, 不同条件下得到的复数平面图均由一个容抗弧和一个感抗弧构成, 分别代表Cl^-在阳极上发生电荷转移的过程和 Cl^-在活性炭电极上的吸附过程 . 增加阳极极化可有效缩短弛豫时间, 阳极极化时, 弛豫时间为2.0×10^-5 s; 增加预处理时间, 弛豫时间逐渐增加, 预处理时间为180 min时, 弛豫时间增加到4.9×10^-5 s; 预处理浓度对弛豫时间的影响可忽略. 弛豫时间分析结果表明, Cl^-吸附速率比扩散速率小, 吸附是电吸附过程的速率控制步骤. 电极表面的覆盖度较低, 仅有10^-4...     

Gold Nanoelectrode Arrays and their Evaluation by Impedance Spectroscopy and Cyclic Voltammetry

A sol–gel strategy is developed to fabricate highly regular Au nanoelectrode arrays (NEAs) consisting of a nanoperforated ultrathin membrane of ZrO₂, which exhibits a well‐ordered array of pores (65±5) nm in diameter with a mean center‐to‐center distance of (110±10) nm, on a polycrystalline gold surface. The structural properties are investigated by field‐emission scanning electron microscopy (FE‐SEM), while grazing incidence small‐angle X‐ray scattering (GISAXS) is used to assess the thickness homogeneity and the period of the array of electrodes. In addition, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are carried out to describe quantitatively the accessibility, electrochemical behavior, and diffusion processes of the gold NEA. A model applying parameters obtained from FE‐SEM, CV, and EIS analyses is proposed to simulate the experimental results. A fairly good agreement between the experimental and the simulated data is obtained, thus allowing the deconvolution of the different diffusion regimes at the NEA.     

自组装膜技术在电分析化学中的应用

本文介绍了自组装膜的类型、结构并着重评述了有机硫化物自组装膜在电分析化学方面的应用进展。     

电化学阻抗法研究环氧膜的吸水性能

电化学阻抗法研究环氧膜的吸水性能罗小雯，陈月辉，李善君，周伟舫（复旦大学高分子科学系，化学系，上海，２００４３３）关键词电化学阻抗谱，环氧膜，交联密度，吸水性能水在环氧树脂膜中有较强的吸收和扩散能力，例如ＸＤ７３４２／ＴＭＡＢ于１９５℃固化２４ｈ，在...     

In-Situ Spectroelectrochemical Measurement of Azobenzene Containing Self-Assembled Monolayers

The electrochemical behavior of an azobenzene containing self-assembled monolayer (SAM) has been examined by means of in-situ Fourier transform infrared reflection absorption (FTIRRA) spectroscopy. The electrochemical reduction product of azobenzene has been confirmed to be hydrazobenzene. A stable and reversible process in both electrochemistry and architecture has been found in the monolayer film.