L-半胱氨酸自组装膜对间苯二酚氧化的电催化作用

研究了pH对L-半胱氨酸自组装膜修饰电极的影响,发现该膜对间苯二酚的电化学氧化具有明显的催化作用.在pH =6.86的L-半胱氨酸溶液中制得的膜最致密.在pH =5的醋酸钠-醋酸缓冲溶液中,间苯二酚在L-半胱氨酸自组装膜修饰电极上产生一灵敏的氧化峰,且峰电流与间苯二酚浓度在0.1-0.6mmol/L范围内呈良好的线性关...     

自组装普鲁士蓝膜修饰电极的制备及表征

通过静电自组装技术在Pt电极表面组装了不同层数的普鲁士蓝（PB）膜,得到了PB修饰的Pt电极。分别利用扫描电镜（SEM）和紫外-可见分光光度计（UV-Vis）表征膜的形貌及光学特性,并且采用循环伏安法（CV）测量膜修饰的Pt电极的循环伏安特性。结果表明：通过自组装技术可以制备出可控厚度的纳米尺度的PB膜修饰电极,膜的紫外吸收峰强度与组装层数符合线性关系,膜的组成同时含有可溶和不溶性PB,且循环伏安法所得到的峰电流正比于扫描速度的平方根以及PB的本体浓度,修饰电极具有好的电化学性能,可用于生物传感器。     

甲醇在Pt电极上电催化氧化的CV研究

运用电化学循环伏安法研究0．5mol·L-1H2SO4溶液中甲醇在Pt电极上吸附和氧化的情况,利用扫描速度与峰电流的关系,研究甲醇电氧化的动力学过程。     

金微粒修饰的电极对细胞色素C的直接电化学响应

采用循环伏安法制备了金微粒修饰的金刚石膜电极。用循环伏安法、电化学交流阻抗法对得到的修饰电极进行了表征。同时考查了细胞色素C在修饰电极上的电化学行为,发现细胞色素C在修饰电极上有显著的直接电化学响应,其氧化还原峰电流与扫描速度呈良好的线性关系,表明细胞色素C在修饰电极上呈现吸附控制的电极反应过程。     

多巴胺在自组装传感器上的电化学行为及检测

利用滴涂法和电化学聚合法层层组装了聚L-半胱氨酸/乙炔黑修饰玻碳电极,用电化学阻抗对电极进行了电化学表征。用该电极作为多巴胺的电化学传感器,循环伏安法表征显示,多巴胺的电化学信号显著增强。在优化条件下,用差分脉冲伏安法对多巴胺进行了定量分析。结果表明,多巴胺在1.67~167μmol/L内与氧化峰电流有着良好的线性关系,线性方程为:I=-0.273c-7.13μA、相关系数为0.998;检出限为0.8μmol/L。用于盐酸多巴胺注射液试样中多巴胺的分析,回收率为96.7%~103%。     

L-半胱氨酸在金电极上的自组装及其电化学性能研究

将L-半胱氨酸(L-Cys)自组装到金电极表面制成L-Cys/Au修饰电极,并用电化学方法研究了它的电化学性质。研究了葡萄糖在自组装膜修饰电极上的电化学氧化行为,实验表明,该膜对葡萄糖的氧化有催化作用。     

基于L-半胱氨酸/壳聚糖修饰的L-抗坏血酸电化学传感器的研究

通过将壳聚糖和L-半胱氨酸修饰到玻碳电极基底表面,制备了一种新型的电化学传感器,并将此传感器应用于对L-抗坏血酸的测定。通过循环伏安法和交流阻抗法对该传感器的电化学特性作了表征。通过线性伏安实验发现:L-抗坏血酸的氧化峰电流与其浓度在1.0×10-5~2.0×10-3mol/L范围内成良好的线性关系,检出限为4.3×10-6mol/L,且该传感器具有良好的重现性和稳定性,并将此传感器成功应用于对维生素C药片中L-抗坏血酸含量的检测。     

基于铁氰化铈纳米膜修饰玻碳电极多巴胺的测定

采用电聚合法制备了铁氰化铈[CeFe(CN)6]纳米膜修饰玻碳电极。用循环伏安法研究了多巴胺(DA)在修饰电极上的电化学行为。实验结果表明,该修饰电极对于DA的氧化还原具有良好的电催化性能。相对于裸电极,DA在铁氰化铈纳米膜修饰玻碳电极上的氧化峰电流显著提高。利用差分脉冲伏安法测定DA,在0.0~1000.0 mol·L-1浓度范围内与氧化峰电流呈良好的线性关系,相关系数为0.994。信噪比为3时,DA检出限为6.0×10-8 mol·L-1。将该方法用于盐酸多巴胺针剂分析,回收率为95.8%~101.9%。     

甲醇在铂微粒修饰碳纳米管/纳米TiO2-聚苯胺膜电极上的电催化氧化

在0.5mol·L-1硫酸介质中,采用循环伏安的电化学聚合方法,以50mv·s-1的扫描速度,在-0.1～0.9V范围内以碳纳米管/纳米TiO2(CNT/nanoTiO2)电极为基体聚合得到了聚苯胺(PAn)复合膜电极,用循环伏安法研究了CNT/nanoTiO2-PAn-Pt电极在0.5mol·L-1H2SO4溶液中的电化学行为以及对甲醇氧化的电催化行为。结果表明,CNT/nanoTiO2-PAn-Pt电极对甲醇的氧化具有很高的电催化活性,并同时存在PAn的协同催化作用。在Pt载量为0.56mg/cm2时,甲醇氧化峰电流达到152mA/cm2,随着Pt载量的增加,甲醇的氧化峰电流最高可达410mA/cm2。     

1-(2-吡啶偶氮)-2-萘酚修饰玻碳电极的制备及其电化学行为

研究了将1-(2-吡啶偶氮)-2-萘酚(PAN)固定于玻碳电极上的方法。将玻碳电极进行抛光处理并经超声波清洗后,于磷酸盐缓冲溶液中用循环伏安法扫描,可将PAN固定于玻碳电极上,制得具有良好电化学活性且较为稳定的修饰电极。制备好的电极在磷酸盐缓冲溶液中的循环伏安曲线有一对氧化还原峰。峰电流随扫描速度的增大而增大,峰电位随pH的升高而减小,在pH 1.0~8.0间有良好的线性关系。     

Layer‐by‐layer self‐assembled multilayer films of single‐walled carbon nanotubes and tin disulfide nanoparticles with chitosan for the fabrication of biosensors

In this study, multilayer films containing chitosan, tin disulfide (SnS₂) nanoparticles, and single‐walled carbon nanotubes were prepared on glassy carbon electrodes with the use of a layer‐by‐layer assembly technique. The resulting films were characterized with cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy, and ultraviolet–visible absorption spectroscopy. The results of CV and EIS indicates that the peak currents and charge‐transfer resistance all had linear responses to the number of assembled layers. The multilayer‐film‐modified electrode showed excellent electrocatalytic properties for some species, such as dopamine hydrochloride (DA), ascorbic acid (AA), and uric acid (UA). The well‐separated voltammetric signals of DA, UA, and AA could be obtained on the assembled multilayer‐film‐modified electrode, and the peak‐to‐peak potential separations were 171, 136, and 307 mV for DA–UA, DA–AA, and UA–AA on CV, respectively. These facts showed that the multilayer‐film‐modified electrode could be used as a new sensor for the simultaneous detection of DA and UA in the presence of AA in a real sample. In addition, the multilayer films were stable, selective, and reproducible. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

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

Single-walled carbon nanotube (SWNT)/polyaniline (PANI) composite films with good uniformity and dispersion were prepared by electrochemical polymerization of aniline containing well-dissolved SWNTs. The results of atomic force microscopy (AFM) and UV-Vis adsorption spectroscopy show that aniline can be used to solubilize SWNTs via formation of donor-acceptor complexes. The electrochemical deposition of SWNT-aniline solutions have been investigated by cyclic voltammetry. The results show that SWNT-based aniline solutions exhibit a drastic increase in peak current within the potential scanning region. The doping effect of SWNTs on PANI films was investigated by electrochemistry and FTIR spectroscopy. The results indicate that the enhanced electroactivity and conductivity of the SWNT/PANI composite films may be due to the strong interaction between SWNTs and PANI, which facilitates the effective degree of electron delocalization.     

Mechanistic insights into homogeneous electrocatalytic reaction for energy storage using finite element simulation

The application of homogeneous electrocatalytic reactions in energy storage and conversion has driven surging interests of researchers in exploring the reaction mechanisms of molecular catalysts. In this paper, homogeneous electrocatalytic reaction between hydroxymethylferrocene (HMF) and L-cysteine is intensively investigated by cyclic voltammetry and square wave voltammetry for which, the second-order rate constant (k_ec) of the chemical reaction between HMF⁺ and L-cysteine is determined via a 1D homogeneous electrocatalytic reaction model based on finite element simulation. The corresponding k_ec (1.1 (mol·m^-3)^-1·s^-1) is further verified by linear sweep voltammograms under the same model. Square wave voltammetry parameters including potential frequency (f), increment (E_step) and amplitude (E_SW) have been comprehensively investigated in terms of the voltammetric waveform transition of homogeneous electrocatalytic reaction. Specifically, the effect of potential frequency and increment is in accordance with the potential scan rate in cyclic voltammetry and the increase of pulsed potential amplitude results in a conspicuous split oxidative peaks phenomenon. Moreover, the proposed methodology of k_ec prediction is examined by hydroxyethylferrocene (HEF) and L-cysteine. The present work facilitates the understanding of homogeneous electrocatalytic reaction for energy storage purpose, especially in terms of electrochemical kinetics extraction and flow battery design.     

三维膜电极电控离子分离过程离子扩散特性研究

通过阴极电沉积法在石墨芯基体上制备铁氰化镍(NiHCF)薄膜,然后组装为多排石墨芯(MRGC)膜电极系统于1mol/LKNO3溶液中测定其循环伏安(CV)曲线。重点考察了不同电极厚度与间距的MRGC基体NiHCF膜电极CV图的阴阳极峰电位分离情况,以及不同扫描速度下膜电极系统的CV图变化情况。研究结果表明,由于三维MRGC膜电极系统内部离子扩散影响,CV图的峰电位将发生偏移。随着石墨芯间距的增加电极内离子扩散阻力降低,导致CV图阴阳极峰电位差ΔEp将减小;固定石墨芯间距而增加电极厚度时电极内离子扩散阻力增加使ΔEp也随之增加;随着扫描速度的增加内扩散的影响加剧导致ΔEp增加。因此循环伏安图阴阳极峰电位的分离程度可用于三维膜电极内离子扩散的分析。     

Application of graphene oxide sheets incorporated in the porous calcium alginate films on the glassy carbon electrode for biosensor construction based on myoglobin

In this work, graphene oxide (GO) sheets were assembled within the porous calcium alginate (CA) films, and applied to fabricate electroactive biosensor by incorporating with myoglobin (Mb). The porous Mb–GO–CA films were fabricated and characterized by scanning electron microscopy (SEM), UV–Vis adsorption, and electrochemistry techniques. UV–Vis spectrum demonstrated that Mb retained its secondary structure in the porous Mb–GO–CA films at medium pH. Cyclic voltammetry of the porous Mb–GO–CA films showed a pair of well-defined and nearly reversible peaks for MbFe(III)/Fe(II) redox couple at ?0.350 V versus saturated calomel electrode in pH 7.0 buffers. The electrochemical parameters such as apparent heterogeneous electron transfer rate constant (k _s) and formal potential (E ^ο′) were estimated by fitting the data of square-wave voltammetry with nonlinear regression analysis. The porous Mb–GO–CA films exhibited excellent electrocatalytic reduction to sodium nitrite, oxygen, and hydrogen peroxide, and showed good reproducibility and stability, which may provide a promising platform for the fabrication of the third-generation biosensor.     

Loading of myoglobin into layer-by-layer films assembled by concanavalin A and dextran based on their biospecific recognition: An electrochemical study

Lectin protein concanavalin A (Con A) and polysaccharide dextran (Dex) were assembled into {Con A/Dex}_n layer-by-layer (LBL) films by biospecific affinity between them. The films were then immersed in myoglobin (Mb) solution to load Mb into the films, designated as {Con A/Dex}_n-Mb. Quartz crystal microbalance (QCM), cyclic voltammetry (CV), square wave voltammetry (SWV), and electrochemical impedance spectroscopy (EIS) were used to monitor the growth of {Con A/Dex}_n films and characterize the {Con A/Dex}_n-Mb films. The Mb in {Con A/Dex}_n-Mb films showed a quasi-reversible CV peak pair for its heme Fe(III)/Fe(II) redox couple, and the Mb-loaded films could be used to electrocatalyze the reduction of oxygen and hydrogen peroxide. The formal potential of Mb (E°′) and the surface concentration of electroactive Mb (Γ*) in the films were affected significantly by the environmental pH. The driving forces of {Con A/Dex}_n film assembly and Mb loading into the films were investigated. This model protein-loaded LBL films may guide us to develop novel electrochemical biosensors based on the direct electrochemistry of enzymes.     

Direct electrochemistry of hemoglobin in biomembrane-like DHP-PDDA polyion-surfactant composite films

Hb-DHP-PDDA films were assembled by incorporating hemoglobin (Hb) into polyion-surfactant DHP-PDDA composite films on pyrolytic graphite (PG) electrodes, where DHP is an anionic surfactant dihexa decylphosphate, and PDDA is a polycation poly(diallyldimethylammonium). Cyclic voltammetry of Hb-DHP-PDDA films showed a pair of stable and reversible peaks for Hb Fe(III)/Fe(II) redox couple at about −0.34 V versus saturated calomel electrode (SCE) in pH 7.0 buffers. The electron transfer rate between Hb and PG electrodes was greatly facilitated in microenvironment of the films. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) suggest that in both DHP-PDDA and Hb-DHP-PDDA films, DHP is self-assembled into an ordered bilayer structure which is sandwiched by PDDA backbone layers. Positions of Soret absorption band indicate that Hb keeps its secondary structure similar to its native state in the films in the medium pH range. Hb could act as an enzymatic catalyst in DHP-PDDA films to catalyze reduction of oxygen, trichloroacetic acid, and nitrite with significant decrease of overpotential.     

Layer-by-layer assembly of myoglobin and nonionic poly(ethylene glycol) through ion-dipole interaction: An electrochemical study

Nonionic poly(ethylene glycol) (PEG) and myoglobin (Mb) were successfully assembled into {PEG/Mb}_n layer-by-layer films on various solid surfaces. Quartz crystal microbalance (QCM), UV-vis spectroscopy and cyclic voltammetry (CV) were used to monitor and confirm the film growth and characterize the films. The Mb in stable {PEG/Mb}_n films showed a quasi-reversible CV response for its heme Fe(III)/Fe(II) redox couple, and was used to electrocatalyze the reduction of various substrates. The interaction between PEG and Mb in the assembly was investigated in detail. A series of comparative experiments showed that the ion-dipole interaction between positively charged groups on the Mb surface and electronegative ether oxygen groups of PEG would be the main driving force for the assembly of {PEG/Mb}_n films, while other interactions such as hydrogen bonding and/or hydrophobic interaction may also play an important role in stabilizing the films in blank buffers.     

Electrochemistry in confined microsystems: Part 1. CV-SECM of reversible system at a confined disk ultramicroelectrode

This work is the first part of a series of papers concerning the study of electrochemical method in case of ultramicroelectrode (UME) confinement in integrated chemical microsystems. This paper is devoted to the discussion of numerical simulation obtained in the case of a transient electrochemical method - i.e. cyclic voltammetry (CV) - applied to a finite disk ultramicroelectrode confined in front of an insulating surface. This configuration corresponds to scanning electrochemical microscopy (SECM) in negative feedback configuration. We describe a new electrochemical method, with acronym CV-SECM, based on the coupling of cyclic voltammetry with scanning electrochemical microscopy. The main advantage of this method is the obtention of a time resolved measurement simultaneously with a high local resolution. The results of the simulation show that adjusting the scan speed of the potential sweep allows the exploration of a controlled range of distance between the UME and the insulating surface. The reverse peak current obtained in cyclic voltammetry exhibits unexpected variations with the approach distance of the UME: (i) a regime of depletion of the electroactive reactant during the forward scan at short distance, associated to a decrease of the peak current and (ii) a regime of accumulation of the electroactive product at larger distance, associated to an increase of the reverse peak current identified in comparison with the free diffusion regime.     

Capacitive and textural characteristics of polyaniline-platinum composite films

The capacitive behavior of various composite thin films composed of polyaniline (PANI) polymerized by cyclic voltammetry and platinum microparticles deposited by potentiostatic or pulse-rest techniques was systematically compared using cyclic voltammetry and chronopotentiometry. These composite films, exhibiting the highly electrochemical reversibility of redox reactions, high power property and good stability between −200 and 600 mV, were demonstrated to be potential candidates for the electrode materials of electrochemical supercapacitors. The effect of the dispersion degree of Pt particles within the composite films on the electrochemical characteristics and stability of the PANI-Pt composite films was discussed. The crystalline information, surface morphologies and platinum distribution profiles of these organic-inorganic composite films were, respectively, characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and Auger electron spectroscopy (AES).