对苯二酚在碳纳米管修饰玻碳电极的电化学行为及电化学动力学研究

碳纳米管(Carbon Nanotubes,CNT)自1991年发现以来,因其结构所具有的高比表面,高电导率,稳定的化学性质与超常的机械强度已成为世界范围内的研究热点,并应用于催化、气体储藏和电极材料等领域。用CNT修饰的电极具有良好的电化学性能并且已经取得了很好的实验结果[1],因此研究碳     

羟胺在碳纳米管修饰玻碳电极上的电催化还原及电化学动力学性质研究

研究了羟胺在碳纳米管修饰玻碳电极(CNT/GC)上的电化学行为。研究结果表明,碳纳米管对羟胺的电化学行为有良好的电催化作用,在-0.62 V有一还原峰,是羟胺获得2个电子还原为铵所形成,同时测定了该电化学过程的动力学参数:电子转移数n为2,电子转移系数α为0.287,电极反应速率常数k为1.35×10-3cm/s。     

Novel estradiol sensors based on carbon nanotube multilayer modified gold hair microelectrodes

Multi-walled carbon nanotube multilayers were modified onto a newly proposed gold hair microelectrode via a simple layer-by-layer assembling method.The resulting electrode showed a sensitive oxidation response to estradiol with detection limit as low as 1.0×10~(-8) mol/L,foreseeing a promising approach to the fabrication of high-sensitive microsensors.     

The oxidation and reduction behavior of nitrite at carbon nanotube powder microelectrodes

Carbon nanotube electrodes were fabricated using powder microelectrode method, and the carbon nanotube powder microelectrodes (CNTPMEs) were characterized by the electro-oxidation and electro-reduction of nitrite. It was found that the kinetics of oxidation and reduction were greatly improved at CNTs compared with that at conventional graphite, indicating that CNTs could catalyze the electrochemical process of nitrite. The kinetic parameters of these process at CNTs were calculated, i.e. k was 0.593 cm s⁻¹, and (1-α)n_α was 0.501±0.018 for the nitrite oxidation. This CNTPME was also used as a nitrite carbon nanotube sensor, and the results showed that the detection limit was 8 μM.     

Direct electron transfer of PQQ-glucose dehydrogenase at modified carbon nanotubes electrodes

In order to establish efficient enzyme-electrode-contacts for the pyrroloquinoline quinone dependent glucose dehydrogenase (PQQ-GDH) different immobilisation strategies are investigated. Multi-walled carbon nanotubes (MWCNT) on gold electrodes are modified by chemical treatment and by (poly)-aniline derivatives. The electropolymerisation of methoxy-m-anilinesulfonic acid and m-aminobenzoic acid on the MWCNTs allows the covalent coupling of the PQQ-GDH. Such a poly-[ASA-ABA]/MWCNT/Au electrode can achieve current densities of up to 500 μA/cm² at a potential of 100 mV vs. Ag/AgCl. Furthermore investigations with small amounts of free PQQ indicate direct electron transfer between enzyme and electrode.     

Electrochemistry at carbon nanotube forests: sidewalls and closed ends allow fast electron transfer

The electrochemical properties of the closed ends and sidewalls of pristine carbon nanotube forests are investigated directly using a nanopipet electrochemical cell. Both are shown to promote fast electron transfer, without any activation or processing of the carbon nanotube material required, in contrast to the current model in the literature.     

Direct electron transfer and voltammetric determination of roxithromycin at a single-wall carbon nanotube coated glassy carbon electrode

The electrochemical behavior of roxithromycin (RM) at a single-wall carbon nanotube (SWNT) coated glassy carbon (GC) electrode was studied. It was found that RM could produce an irreversible anodic peak at the electrode. When the pH of supporting electrolyte (i.e. phosphate buffer solution) was 7 the peak potential was 0.86V (vs. SCE). The electrochemical reaction contained electron and proton transfer, and the electron-transfer coefficient (α) was ca. 0.87. The anodic peak depended on the adsorption of RM, the maximum adsorption amount was about 3.99×10(-10)molcm(-2). The adsorbed RM could be removed by cycling between 0.1 and 1.1V in a blank solution for about two minutes, and the electrode thus could be regenerated. Under the optional conditions, the anodic peak current was linear to RM concentration over the range of 5.0×10(-6) to 1.0×10(-4)M. The limit of detection was 5.0×10(-7)M (S/N=3) for 180s accumulation at -0.8V. The modified electrode had good stability and repeatability, and it was successfully applied to the determination of RM in medicine samples.     

Direct electron transfer of glucose oxidase on the carbon nanotube electrode

The direct electrochemistry of redox enzymes (or proteins) has received more and more attention[1—9]. These studies developed an electrochemical basis for the investigation of enzyme structure, mechanisms of redox transformations of enzyme molecules and metabolic processes involving redox transformations. From these studies, one can also find potential appli-cations of enzymes in biotechnology. For example, if an enzyme immobilized on electrode surface is ca-pable of the direct electron tra…     

二茂铁修饰碳黑微电极同时测定多巴胺和抗坏血酸

研究了神经递质多巴胺(DA)和抗坏血酸(AA)在二茂铁修饰碳黑微电极上的电化学行为。实验结果表明,在pH4.5的磷酸盐中,DA在该电极上的线性范围为2.0×10-6～4.0×10-3mol/L,检出限(3σ)为1.0×10-6mol/L;AA在该电极上的线性范围为6.0×10-6～1.0×10-3mol/L,检出限(3σ)为2.0×10-6mol/L;用这种电极可以同时测定多巴胺,抗坏血酸。     

Electrochemical detection of amino acids at carbon nanotube and nickel-carbon nanotube modified electrodes

The oxidation and enhanced detection of traditionally 'non-electroactive' amino acids at a single-wall carbon nanotube (SWNT) surface and at a nickel hydroxide film electrochemically deposited and generated upon the SWNT layer is reported. Different CNT are compared, with Nafion-dispersed SWNT offering the most favorable layer for constant-potential amperometric detection. Factors affecting the oxidation process, including the pH or applied potential, are assessed. The response of the SWNT-Nafion coated electrode compares favorably with that of copper and nickel disk electrodes under flow injection analysis (FIA) conditions. The electrodeposition of nickel onto the SWNT-Nafion layer (Ni-CNT) led to a dramatic enhancement of the analytical response (vs. that observed at the SWNT or nickel electrodes alone). The oxidative process at the Ni(OH)(2) layer has been studied and the increase in sensitivity rationalized. In the presence of amino acid the Ni-CNT layer undergoes an electrocatalytic process in which the amino acid reduces the newly formed NiO(OH) species. Furthermore, the attractive response of both the CNT and Ni-CNT layers has allowed these electrodes to be used for constant-potential FIA of various amino acids and indicates great promise for monitoring chromatographic effluents. Once again an improved signal was observed at the Ni-CNT electrode compared to nickel deposited upon a bare glassy carbon electrode (Ni-GC).     

Polypyrrole nanotube modified by gold nanoparticles for improving the neural microelectrodes

Journal of Solid State Electrochemistry - High selectivity and low impedance are preferred properties for neural microelectrodes. The localized and controlled release of drugs from the...     

Voltammetric determination of disinfectants at multiwalled carbon nanotube modified glassy carbon electrode

The voltammetric method for simultaneous determination of some disinfectants at glassy carbon electrode modified with multiwalled carbon nanotubes is presented. The examined compounds are: 2-phenylphenol, 4-chloro-3-methylphenol, triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol and 2-mercaptobenzothiazole. The measurements has been performed using cyclic voltammetry and differential pulse voltammetry in Britton-Robinson buffers as supporting electrolytes. The modification of electrode surface with multiwalled carbon nanotubes enhances the peak current. It is possible to measure mixtures of two compounds (2-phenylphenol and 2-mercaptobenzothiazole, 4-chloro-3-methylphenol and 2-mercaptobenzothiazole, triclosan and 2-mercaptobenzothiazole) in the solution of pH 9.9, which provides the best separation of oxidation peaks.     

Electrochemical parameters of ethamsylate at multi-walled carbon nanotube modified glassy carbon electrodes

In this paper, some electrochemical parameters of ethamsylate at a multi-walled carbon nanotube modified glassy carbon electrode, such as the charge number, exchange current density, standard heterogeneous rate constant and diffusion coefficient, were measured by cyclic voltammetry, chronoamperometry and chronocoulometry. The modified electrode exhibits good promotion of the electrochemical reaction of ethamsylate and increases the standard heterogeneous rate constant of ethamsylate greatly. The differential pulse voltammetry responses of ethamsylate were linearly dependent on its concentrations in a range from 2.0 x 10(-6) to 6.0 x 10(-5) mol L(-1), with a detection limit of 4.0 x 10(-7) mol L(-1).     

胡椒碱在碳纳米管修饰电极上的电化学行为研究

研究了胡椒碱在碳纳米管修饰电极上的电化学行为,在pH为6.4的磷酸盐缓冲溶液中,胡椒碱在-1.12V(vs.SCE)处有一灵敏的还原峰.与裸电极相比,还原峰电位明显正移,峰电流显著增加,表明该修饰电极对胡椒碱的还原反应具有明显的催化作用.峰电流与胡椒碱的浓度在10-6～10-5mol/L范围内呈良好的线性关系(r=0.995),检出限为2.0×10-7mol/L.同时,计算了电荷转移数和扩散系数,考查了修饰电极的重现性,7次平行测量的RSD为4.96%.     

Resolving electron transfer kinetics at the nanocrystal/solution interface

The kinetics of electron transfer between individual gold nanocrystals and a solution redox species is quantified. The observed rate is dependent on the extent of electronic coupling between nanocrystals in the monolayer indicating the effect of Coulomb blockade on electrochemical kinetics.     

Voltammetry and amperometric detection of tetracyclines at multi-wall carbon nanotube modified electrodes

The voltammetric behaviour and amperometric detection of tetracycline (TC) antibiotics at multi-wall carbon nanotube modified glassy carbon electrodes (MWCNT-GCE) are reported. Cyclic voltammograms of TCs showed enhanced oxidation responses at the MWCNT-GCE with respect to the bare GCE, attributable to the increased active electrode surface area. Hydrodynamic voltammograms obtained by flow-injection with amperometric detection at the MWCNT-GCE led us to select a potential value E _det = +1.20 V. The repeatability of the amperometric responses was much better than that achieved with bare GCE (RSD ranged from 7 to 12%), with RSD values for i _p of around 3%, thus demonstrating the antifouling capability of MWCNT modified electrodes. An HPLC method with amperometric electrochemical detection (ED) at the MWCNT-GCE was developed for tetracycline, oxytetracycline (OTC), chlortetracycline and doxycycline (DC). A mobile phase consisting of 18:82 acetonitrile/0.05 mol L⁻¹ phosphate buffer of pH 2.5 was selected. The limits of detection ranged from 0.09 μmol L⁻¹ for OTC to 0.44 μmol L⁻¹ for DC. The possibility to carry out multiresidue analysis is demonstrated. The HPLC-ED/MWCNT-GCE method was applied to the analysis of fish farm pool water and underground well water samples spiked with the four TCs at 2.0 × 10⁻⁷ mol L⁻¹. Solid-phase extraction was accomplished for the preconcentration of the analytes and clean-up of the samples. Recoveries ranged from 87 ± 6 to 99 ± 3%. Under preconcentration conditions, limits of detection in the water samples were between 0.50 and 3.10 ng mL⁻¹.     

阿奇霉素在多壁碳纳米管修饰电极上的电化学行为及其测定

运用循环伏安法与线性扫描伏安法研究了阿奇霉素在多壁碳纳米管修饰玻碳电极上的电化学行为,建立了一种直接测定阿奇霉素的电化学分析方法。结果表明,与裸玻碳电极相比,多壁碳纳米管修饰电极能显著提高阿奇霉素的氧化峰电流,阿奇霉素的电极过程完全不可逆,存在典型的吸附特性。在优化的实验条件下,氧化峰电流与阿奇霉素浓度在3.0×10-7～2.5×10-5 mol/L和2.5×10-5～5.0×10-4 mol/L范围内呈现良好的线性关系,检出限为1.0×10-7 mol/L。     

Local electron transfer rate measurements on modified and unmodified glassy carbon electrodes

A natural and artificial distribution of electron transfer activity on glassy carbon electrodes can be observed and quantified by the use of scanning electrochemical microscopy (SECM). A large (sevenfold) spread in rate constant is found for randomly sampled sites on polished, untreated glassy carbon surfaces. Direct-mode oxidation with the SECM tip was used to produce small regions of oxidized carbon on a polished surface. A large increase in electron transfer rate for the Fe(II/III) ion is observed on the locally oxidized carbon surface in comparison to the unoxidized region. Rate constant measurements made along a line profiles the transition from unoxidized to oxidized surfaces. SECM images of defect sites show reaction–rate variations. Rate constants measured at several locations of the defective surface allows discrimination between the kinetic and topographic components of the SECM image. Dedicated to the 80th birthday of Keith B. Oldham     

Monitoring carbon nanotube growth by formation of nanotube stacks and investigation of the diffusion-controlled kinetics

A novel method is presented to monitor carbon nanotube (CNT) growth by formation of CNT stacks. By this process, CNT growth kinetics are investigated for densely packed CNT films in the gas-diffusion-controlled regime. CNT stacks are fabricated by water-assisted selective etching and the cyclic introduction of ethylene into the chemical vapor deposition (CVD) reactor. Formation of the CNT stacks allows monitoring of the CNT growth evolution, thereby providing insight into the growth kinetics. A parabolic increase of CNT length versus time is observed, indicating a gas-diffusion-controlled growth mode. The densely packed, well-aligned CNT films act as porous barrier layers to the diffusion of ethylene precursor to the catalyst nanoparticles, since these films form via a base-growth mode under the conditions invoked in our system. By adjustment of CNT growth time and temperature, a quantitative time-evolution analysis is performed to investigate the CNT growth model and extract the gas precursor mass transfer coefficient in the CNT films. The self-diffusion of gases in the densely packed CNT films is found to be Knudsen diffusion with a diffusion coefficient on the order of 10(-4) cm(2)/s.