Fabrication of Prussian Blue modified ultramicroelectrode for GOD imaging using scanning electrochemical microscopy

A Prussian Blue (PB) film modified disk ultramicroelectrode (UME) was fabricated by electrochemical deposition technique on a Pt-disk UME. The electrocatalytical reductions of hydrogen peroxide derived from glucose oxidase (GOD) on this modified UME were investigated. The enzymatic biochemical reactivity was imaged by scanning electrochemical microscopy (SECM) utilizing the PB film modified UME. It is evident that sensitivity and spatial resolution for hydrogen peroxide measurement were improved obviously. SECM images obtained clearly revealed the concentration profile of the reaction products around the enzymes. The PB film modified microelectrode is in the nature of simple preparation, high catalytic activity on hydrogen peroxide and substrate selectivity for SECM etc.     

Study of the electrochemical behavior of mitoxantrone and its determination at a Co-C modified ultramicroelectrode

In 0.005 mol dm-3 Tris-0.05 mol dm-3 NaCl buffer solution (pH 7.10), the electrochemical behavior of mitoxantrone was studied by linear-sweep voltammetry and cyclic voltammetry at a Co-carbon fiber ion implantation modified ultramicroelectrode. A sensitive reduction peak was obtained. The peak potential was -0.798 V (vs. SCE), the peak current was proportional to the concentration of mitoxantrone over the range of 2.0 x 10(-7)-6.0 x 10(6) mol dm-3 and the detection limit was 4.2 x 10(-8) mol dm-3. This method was applied to the direct determination of mitoxantrone in urine. Recoveries were in the range 95.4-105.8%. The reduction process was quasi-reversible with absorptive characteristics at a Co-C ultramicroelectrode. According to Laviron's theory, the electrode reaction rate constant ks and the electron transfer alpha of mitoxantrone were 4.4 s-1 and 0.48, respectively. The composition and depth distribution of elements on the surface of the Co-C ultramicroelectrode were determined by Auger electron spectroscopy. The experiments showed that Co was implanted into the surface of the carbon fiber, and the Co-C ultramicroelectrode had good stability and reproducibility.     

Utilisation of polypyrrole modified electrode for the determination of pesticides

Cyclic voltammetric studies of isoproturon and carbendazim using polypyrrole modified glassy carbon electrode were carried out. The electrode and reaction conditions, which yielded maximum current signal, were selected for the development of stripping voltammetric procedure for the determination of the pesticides. The oxidation peak around 1.3?V obtained for isoproturon and carbendazim while employing polypyrrole modified electrode showed maximum current response. This peak was chosen for stripping analysis using square wave mode. The experimental parameters were optimized and the calibration plot was obtained. The LOD was 0.5?ng?mL^?1 for isoproturon and 5?ng?mL^?1 for carbendazim. The relative standard deviation for 5 identical measurements was 2.81% and 3.33% for isoproturon and carbendazim respectively. The applicability of the method was verified by determining the pesticides in spiked soil and water samples.     

电流型聚吡咯碘离子化学修饰电极的制备与性能研究

在玻碳电极(GCE)表面上修饰了一层导电聚合物 聚吡咯(Ppy)薄膜,用循环伏安法制备了新型的基于电流响应的掺杂碘离子的聚吡咯修饰电极;研究了电极的电化学特性。此修饰电极对碘离子的响应是基于碘离子在Ppy膜与电解质溶液中的掺杂平衡以及Ppy膜中的碘离子在修饰电极表面的氧化还原过程;制成的电流型电极对5 0×10-2mol/L～1 0×10-5mol/L的碘离子呈良好的线性响应关系,检出限为6 0×10-6mol/L。     

Functionalized polypyrrole nanotube arrays as electrochemical biosensor for the determination of copper ions

A novel electrochemical biosensor based on functionalized polypyrrole (PPy) nanotube arrays modified with a tripeptide (Gly-Gly-His) proved to be highly effective for electrochemical analysis of copper ions (Cu²⁺). The vertically oriented PPy nanotube arrays were electropolymerized by using modified zinc oxide (ZnO) nanowire arrays as templates which were electrodeposited on indium–tin oxide (ITO) coated glass substrates. The electrodes were functionalized by appending pyrrole-α-carboxylic acid onto the surface of polypyrrole nanotube arrays by electrochemical polymerization. The carboxylic groups of the polymer were covalently coupled with the amine groups of the tripeptide, and its structural features were confirmed by attenuated total reflection infrared (ATR-IR) spectroscopy. The tripeptide modified PPy nanotube arrays electrode was used for the electrochemical analysis of various trace copper ions by square wave voltammetry. The electrode was found to be highly sensitive and selective to Cu²⁺ in the range of 0.1–30 μM. Furthermore, the developed biosensor exhibited a high stability and reproducibility, despite the repeated use of the biosensor electrode.     

超微电极技术的发展现状

本文在阐述超微电极技术相关原理的基础上,总结了超微电极的特点、类型及研究方法,综述近十年来超微电极的制备与应用进展,并介绍了超微电极的发展现状。     

Preparation of uniform silica/polypyrrole core/shell microspheres and polypyrrole hollow microspheres by the template of modified silica particles using different modified agents

Silica/polypyrrole (PPY) core/shell microspheres and PPY hollow microspheres were prepared by the template of silica particles whose surface character was modified with different modified agents. The morphology and structure of the particles were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Elemental analysis and X-ray photoelectron spectroscopy (XPS) were carried out to characterize the structure of PPY hollow microspheres. We investigated the effect of different modified agents on the surface character of silica particles and the effect of surface character of silica particles on the morphology of PPY hollow microspheres. The effect of reaction conditions on the size of core/shell particles and hollow particles was also studied.     

Studies on polypyrrole modified nafion membrane for vanadium redox flow battery

In order to prevent the vanadium crossover and preferential water transfer in all-vanadium redox flow battery (VRFB), three methods – electrolyte soaking, oxidation polymerisation and Electrodeposition, were used to modify Nafion 117 membranes using pyrrole. The surface of the modified membranes was uniform and even, and the membranes were characterised in terms of morphology, membrane area resistance, vanadium permeability and water transfer property. The properties of all the modified membranes were improved greatly. The membranes modified by Electrodeposition showed a best combination of the membrane resistance, vanadium permeability and water transfer property, the experimental results showed that the V(IV) ion permeability of polypyrrole modified Nafion membranes by Electrodeposition at the conditions of 0.025 mA cm⁻² and 0 ^°C for 60 min reduced more than 5 times from 2.87 × 10⁻⁶ cm² min⁻¹ to 5.0 × 10⁻⁷cm² min⁻¹, and the water transfer property decreased more than 3 times from 0.72 ml/72 h cm² to 0.22 ml/72 h cm². All above properties made the modified Nafion membranes more applicative in the VRFB system. This paper also reported other methods for Nafion membrane modification and the influences of the deposition conditions on the properties of the membrane selectivity and water transfer.     

Biosensor for on-line fluorescent detection of trifluoroperazine based on genetically modified calmodulin

This paper describes the development of a novel on-line biosensor based on a fluorescently labeled human calmodulin (CaM), hCaM M124C-mBBr, immobilized on controlled-pore glass (CPG), for the analysis of trifluoroperazine (TFP); a phenothiazine drug in human urine samples. The device was automated by packing hCaM M124C-mBBr-CPG in a continuous-flow microcell connected to a monitoring system, composed of a bifurcated optical fiber coupled to a spectrofluorometer. Operating parameters of the on-line biosensor (flow rate, sample injection volume, and carrier solution and buffer pH) were studied and optimized. Under the optimal conditions, the biosensor provides a detection and a quantification limit of 0.24 and 0.52 μg mL⁻¹, respectively, and a dynamic range from 0.52 to 61.05 μg mL⁻¹ TFP (n = 5, correlation coefficient 0.998). The response time (t ₁₀₀) was shorter than 42 s (recovery time <4.5 min) and reproducibility and repeatability of the TFP measurements, within the linear response range, were lower than 1.4 and 2.7%, respectively. The device was successfully applied to the analysis of TFP in spiked human urine samples with recoveries ranging between 97 and 101% and with RSDs lower than 5.9%.     

Evaporation induced uniform polypyrrole coating on CuO arrays for free-standing high lithium storage anode

Journal of Solid State Electrochemistry - Polypyrrole (PPy) used as popular coatings can improve the electrochemical performance of electrodes greatly; however, uniform coatings of PPy on...     

Biosensor for atrazin based on aligned carbon nanotubes modified with glucose oxidase

A sensitive method was developed for the determination of the hebicide atrazine. It based on the use of glucose oxidase that is self-assembled on aligned carbon nanotubes on the surface of a copper electrode. The surface morphology and electrochemical properties of the electrode were characterized by field emission scanning electron microscopy and cyclic voltammetry. The effects of buffer solution and incubation time on the response of the electrode were investigated. Response to atrazine is linear in the range from 0.58 µM to 42 µM, and the detection limit is 39 nM. The performance of the biosensor was verified by determination of atrazine in environmental water samples.     

Electrocatalytic reduction of proton on polypyrrole coatings onto aluminium modified by the electrochemical cementation process

Strongly adherent and smooth polypyrrole coatings were formed at constant current density on aluminium sheet from aqueous solutions of pyrrole and oxalic acid. A new method (cementation) of formation of modified polypyrrole containing dispersed three-dimensional array of copper is presented. These films were investigated by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The electrocatalytic effect toward proton reduction was observed on the modified electrode.     

Ac-electrogravimetry study of ionic exchanges on a polypyrrole modified electrode in various electrolytes

For many years, polypyrrole films have appeared to be the most studied conducting polymer. Unfortunately, shadows still remain concerning the electrochemical mechanisms of these films and in particular, the aspect which concerns the limiting step which governs the electrochemical response. Different possibilities are available such as the transport of ionic species in the film, the electron transfer at the electrode/film or the electron motion in the film, the ionic exchanges at the film/interface electrolyte. Classical electrochemical methods do not permit to discriminate between these effects. Ac-electrogravimetry technique was used here to demonstrate that the electrochemical behaviour of thin pPy films is governed by the ionic insertion without any doubt. Particular parameters were modified as the ionic atomic weight or the electrolyte concentration to corroborate this idea.     

Synthesis and anion binding properties of 2,5-diamidothiophene polypyrrole Schiff base macrocycles

[reaction: see text] Two easy-to-synthesize polypyrrolic 2,5-diamidothiophene Schiff base macrocycles are reported, along with their anion binding properties as determined via UV-vis spectroscopic titrations carried out in dichloroethane. There is a striking difference between the interactions with anions of the two macrocycles, a finding ascribed to differences in their rigidity. For example, the more flexible dipyrromethane-derived macrocycle displays a 1.2:1 hydrogen sulfate versus nitrate selectivity, while its more rigid bipyrrole-derived congener shows a 7.4:1 selectivity in favor to hydrogen sulfate.     

Preparation and electrochemistry of modified polypyrrole films by anodic copolymerization techniques

The anodic copolymerization of pyrrole and N-(ω-ferrocenylalkyl)pyrroles, FcPy-n, at platinum electrodes in an electrolyte consisting of tributylammonium benzenesulfonate in moist acetonitrile is optimized with respect to the absolute and relative concentrations of the monomers and the spacer length of FcPy-n. The copolymer composition is estimated from cyclic voltammograms of the polymer films. Only films with less than 20% FcPy-n content show the typical polypyrrole voltammograms. Free standing copolymer films with a conductivity of ca. 10 S cm⁻¹ can be prepared.     

Electrochemical growth of two-dimensional gold nanostructures on a thin polypyrrole film modified ITO electrode

Two-dimensional gold nanostructures have been fabricated by electrochemical deposition of gold nanoparticles onto indium tin oxide (ITO) glass substrate modified with thin polypyrrole film. By controlling the electrodeposition conditions, gold nanoparticles with dendritic rod, sheet, flower-like (consisting of staggered nanosheets), and pinecone-like structures were generated. The flower-like gold nanoparticles showed high catalytic activity on electrochemical reduction of oxygen, and its activity was measured to be approximately 25 times that of gold pinecones and 10(4) times that of gold nanosheets in terms of gold weight. The pinecone-like nanoparticles can form a compact film with nano-/microscale binary structure like a lotus leaf surface. After modification with n-dodecanethiol, the surface showed superhydrophobic properties with a water contact angle of 153.4 degrees and a tilt angle of 4.4 degrees (5 microL droplet).     

聚吡咯／多壁碳纳米管修饰电极对多巴胺的测定

制备了聚吡咯/多壁碳纳米管(PPy/MWNT)复合膜修饰电极。研究了神经递质多巴胺(DA)在该修饰电极上的电化学行为。实验表明,PPy/MWNT复合膜修饰电极对DA的电催化作用优于PPy修饰电极。在pH=4.10的0.2mol/L醋酸-醋酸钠缓冲溶液中,DA在该修饰电极上的CV曲线于0.31V和0.28V处出现一对灵敏的氧化还原峰,峰电位差△Ep比裸玻碳电极降低58mV,比PPy修饰电极降低28mV,峰电流显著增加。氧化峰电流ipa与DA浓度在1.0×10-4~7.8×10-8mol/L范围内呈良好的线性关系,线性回归方程为ip(μA)=0.2512 1.2300C(×10-5mol/L),相关系数r=0.9992,检出限为3.9×10-8mol/L。常见物质对DA的检测无干扰,DA注射液样品检测回收率为94%~104%。