Direct electrochemistry and electrochemical catalysis of myoglobin-TiO2 coated multiwalled carbon nanotubes modified electrode

TiO(2) nanoparticles were homogeneously coated on multiwalled carbon nanotubes (MWCNTs) by hydrothermal deposition, and this nanocomposite might be a promising material for myoglobin (Mb) immobilization in view of its high biocompatibility and large surface. The glassy carbon (GC) electrode modified with Mb-TiO(2)/MWCNTs films exhibited a pair of well-defined, stable and nearly reversible cycle voltammetric peaks. The formal potential of Mb in TiO(2)/MWCNTs film was linearly varied in the range of pH 3-10 with a slope of 48.65 mV/pH, indicating that the electron transfer was accompanied by single proton transportation. The electron transfer between Mb and electrode surface, k(s) of 3.08 s(-1), was greatly facilitated in the TiO(2)/MWCNTs film. The electrocatalytic reductions of hydrogen peroxide were also studied, and the apparent Michaelis-Menten constant is calculated to be 83.10 microM, which shows a large catalytic activity of Mb in the TiO(2)/MWCNTs film to H(2)O(2). The modified GC electrode shows good analytical performance for amperometric determination of hydrogen peroxide. The resultant Mb-TiO(2)/MWCNTs modified glassy carbon electrode exhibited fast amperometric response to hydrogen peroxide reduction, long term life and excellent stability. Finally the activity of the sensor for nitric oxide reduction was also investigated.     

复合方式对MWCNTs/TiO2纳米复合薄膜光电化学性能的影响

采用溶胶-凝胶法制备了不同复合方式的系列多壁碳纳米管(multi-walled carbon nanotubes, MWCNTs)/TiO2纳米复合薄膜电极. 通过SEM表征了薄膜的表面形貌, 并测定了MWCNTs引入前后对TiO2晶型结构和光吸收性能的影响以及不同复合方式的纳米复合薄膜的光电化学特性. 结果表明, MWCNTs/TiO2纳米复合薄膜表面形成无序多孔的形貌, 其光谱吸收边可拓展到可见光区; MWCNTs底层分布的纳米复合薄膜比纯TiO2表现出更好的光电活性, 而MWCNTs在表层分布及均匀分布的纳米复合薄膜的光电活性相对较差. 依据载流子分离原理探讨了不同复合方式对纳米复合薄膜光电性能的影响, 底层分布MWCNTs的纳米复合薄膜由于MWCNTs有效地收集传递电子并阻止载流子的复合从而提高了光电化学活性.     

Mb/AuNPs/MWCNTs/GC电极对H2O2电催化性能的研究

采用还原法制备了AuNPs/MWCNTs复合材料,并构建了氧化还原蛋白质的固定化和生物传感界面AuNPs/MWCNTs/GC电极.以肌红蛋白(Myoglobin,Mb)为例,研究了固定化蛋白质在AuNPs/MWCNTs/GC电极上的直接电化学.结果表明,AuNPs/MWCNTs复合材料不仅能有效地促进Mb与电极表面的直接电子转移,而且能很好地保持固定化Mb的生物催化活性.Mb/AuNPs/MWCNTs/GC电极对H2O2具有良好的电催化还原性能,其线性响应范围为1～138μmol·L-1,检测限为0.32μmol·L-1(S/N=3),并具有较低的米氏常数(0.143 mmol·L-1).该电极操作简单,响应迅速,稳定性和重现性好,有望用于蛋白质的固定化及第三代生物传感器的制备.     

基于金纳米粒子/聚阿魏酸/多壁碳纳米管修饰电极的DNA计时库仑法生物传感器的制备

构建了基于金纳米粒子/聚阿魏酸/多壁碳纳米管(AuNPs/PFA/MWCNTs)修饰电极的DNA计时库仑法生物传感器.利用循环伏安技术在多壁碳管修饰的玻碳电极表面上聚合一层阿魏酸,在恒电位条件下,在阿魏酸表面沉积金纳米粒子,巯基DNA作为探针通过金硫键固定在金纳米粒子表面.电化学交流阻抗技术(EIS)与扫描电镜(SEM...     

复合修饰电极测定p-硝基苯酚新方法的研究与探讨

将多壁碳纳米管分散在孔雀绿溶液中并滴涂在玻碳电极表面,再电聚合一层孔雀绿膜,制备了一种新型的聚孔雀绿/多壁碳纳米管复合膜修饰玻碳电极.用电化学方法对所制得的复合修饰电极进行了表征,并研究了p-硝基苯酚在该电极上的电化学行为.结果表明,所制备的复合修饰电极对P-硝基苯酚有良好的电催化作用,从而建立了一种直接测定P-硝基苯...     

镧掺杂的二氧化锰/碳纳米管电化学超级电容器复合电极

尽管在二氧化锰/多壁碳纳米管（MnO₂/MWCNTs）上获得了较高的比电容,低电导率仍是制约MnO₂担载量或膜厚度提高的主要障碍.另一个问题是MnO₂/MWCNTs的循环稳定性远低于活性炭.所以截止到目前这一新型材料的应用仍然受到很大的限制.本文采用原位还原的方法制备镧掺杂二氧化锰/多壁碳纳米管电化学超级电容器复合电极材料.分别通过透射电镜（TEM）、扫描电镜（SEM）、X射线衍射（XRD）和傅里叶变换红外（FTIR）光谱等技术对这些复合材料的形貌与结构进行了分析.采用循环伏安法、恒电流充放电法和交流阻抗法对其进行了电化学性能的研究.研究结果表明,通过还原MnO₄^-可以在MWCNTs上形成La掺杂MnO₂复合材料.La掺杂降低了复合电极的电阻,这是因为La的引入可以增大MnO₂的晶格缺陷,从而提高材料的电导率以及电极的电化学性能.因此La掺杂是克服MnO₂本征导电性差的有效途径之一.掺杂La可以在不增大电极电阻的情况下提高MnO₂的担载量或膜厚度.La掺杂的更重要的作用是使以MnO₂/MWCNTs作电极的对称电化学超级电容器的循环性能得到显著改善.此外,La掺杂也使复合电极的比电容得到一定程度的提高.     

TiO2/Fe3O4/Multiwalled Carbon Nanotubes Nanocomposite as Sensing Platform for Simultaneous Determination of Morphine and Diclofenac at a Carbon Paste Electrode

Russian Journal of Electrochemistry - A nanocomposite of TiO2/Fe3O4/MWCNTs (TFMWCNT) and ionic liquid was used to fabrication of a novel modified carbon paste electrode. The modified electrode was...     

Direct electron transfer of cytochrome C and its electrocatalytic properties on multiwalled carbon nanotubes/ciprofloxacin films

In this study, stable and homogenous thin films of multiwalled carbon nanotubes (MWCNTs) were obtained on conducting surface using ciprofloxacin (CF, fluoroquinolone antibiotic) as an effective-dispersing agent. Further, MWCNTs/CF film modified electrodes (glassy carbon and indium tin oxide-coated glass electrode) are used successfully to study the direct electrochemistry of proteins. Here, cytochrome C (Cyt-C) was used as a model protein for investigation. A MWCNTs/CF film modified electrode was used as a biocompatible material for immobilization of Cyt-C from a neutral buffer solution (pH 7.2) using cyclic voltammetry (CV). Interestingly, Cyt-C retained its native state on the MWCNTs/CF film. The Cyt-C adsorbed MWCNTs/CF film was characterized by scanning electron microscopy (SEM), UV–visible spectrophotometry (UV-vis) and CV. SEM images showed the evidence for the adsorption of Cyt-C on the MWCNTs/CF film, and UV–vis spectrum confirmed that Cyt-C was in its native state on MWCNTs/CF film. Using CV, it was found that the electrochemical signal of Cyt-C was highly stable in the neutral buffer solution and its redox peak potential was pH dependent. The formal potential (−0.27 V) and electron transfer rate constant (13 ± 1 s⁻¹) were calculated for Cyt-C on MWCNTs/CF film modified electrode. A potential application of the Cyt-C/MWCNTs/CF electrode as a biosensor to monitor H₂O₂ has been investigated. The steady-state current response increases linearly with H₂O₂ concentration from 2 × 10⁻⁶ to 7.8 × 10⁻⁵ M. The detection limit for determination of H₂O₂ has been found to be 1.0 × 10⁻⁶ M (S/N = 3). Thus, Cyt-C/MWCNTs/CF film modified electrode can be used as a biosensing material for sensor applications.     

琼脂糖膜固载肌红蛋白催化还原过氧化物的研究

用琼脂糖(agarose)将肌红蛋白(Mb)固定在玻碳电极(GCE)表面,制备了Mb-Agarose膜修饰电极。在水-乙醇混合溶液中,包埋在Agarose中的Mb与电极发生直接电子传递,并且能催化还原H2O2、过氧化丁酮、氢过氧化叔丁基、氢过氧化异丙基苯等过氧化物和NO。Mb-Agarose膜修饰电极具有较好的稳定性和重现性,可用于上述过氧化物和亚硝酸盐的定量检测。     

Simultaneous Determination of Trace Zinc(II) and Cadmium(II) by Differential Pulse Anodic Stripping Voltammetry Using a MWCNTs–NaDBS Modified Stannum Film Electrode

A multiwalled carbon nanotubes–sodium dodecyl benzene sulfonate (MWCNTs–NaDBS) modified stannum film electrode was employed for the determination of cadmium(II) and zinc(II). The Sn/MWCNTs‐NaDBS film electrode was prepared by applying MWCNTs–NaDBS suspension to the surface of the GCE, while the Sn film was plated in situ simultaneously with the target metal ions. Under optimal conditions, linear calibration curves were obtained in a range of 5.0 ?100.0 μg L^?1 with detection limits of 0.9 μg L^?1 for zinc(II) and 0.8 μg L^?1 for cadmium(II), respectively. This film electrode was successfully applied to the determination of Zn(II) and Cd(II) in tap water sample.     

A promising electrochemical sensing platform based on copper nanoparticles-decorated polymer in carbon nanotube electrode for monitoring methimazole

In this paper, a novel and convenient electrochemical sensor for detection of methimazole (MMI) by differential pulse voltammetry is presented. This sensor was fabricated by dripping well-dispersed MWCNTs onto glassy carbon electrode (GCE) surface, and then poly-l-Arg (P-L-Arg) film was deposited on the electrode. Finally, Cu nanoparticles (CuNPs) were electrochemically deposited on the resulting film by using cyclic voltammetry to prepare CuNPs-P-L-Arg/MWCNTs/GCE. The surface morphology of the electrodes has been studied by scanning electron microscopy. Studies reveal that the irreversible oxidation of MMI was highly facile on CuNPs-P-L-Arg/MWCNTs/GCE. The dynamic detection range of this sensor to MMI was 5.2–50 µM, with the detection limit of 2 µM. A new voltammetric method for determination of MMI was erected and shows good sensitivity and selectivity, very easy surface update and good stability. The analytical application of the modified electrode is demonstrated by determining MMI in biological fluids (serum).     

Electrocatalytic Reduction of H2O2 and Oxygen on the Surface of Thionin Incorporated onto MWCNTs Modified Glassy Carbon Electrode: Application to Glucose Detection

A new H₂O₂ enzymeless sensor has been fabricated by incorporation of thionin onto multiwall carbon nanotubes (MWCNTs) modified glassy carbon electrode. First 50 μL of acetone solution containing dispersed MWCNTs was pipetted onto the surface of GC electrode, then, after solvent evaporations, the MWCNTs modified GC electrode was immersed into an aqueous solution of thionin (electroless deposition) for a short period of time <5–50 s. The adsorbed thin film of thionin was found to facilitate the reduction of hydrogen peroxide in the absence of peroxidase enzyme. Also the modified electrode shows excellent catalytic activity for oxygen reduction at reduced overpotential. The rotating modified electrode shows excellent analytical performance for amperometric determination of hydrogen peroxide, at reduced overpotentials. Typical calibration at ?0.3 V vs. reference electrode, Ag/AgCl/3 M KCl, shows a detection limit of 0.38 μM, a sensitivity of 11.5 nA/μM and a liner range from 20 μM to 3.0 mM of hydrogen peroxide. The glucose biosensor was fabricated by covering a thin film of sol–gel composite containing glucose oxides on the surface of thionin/MWCNTs modified GC electrode. The biosensor can be used successfully for selective detection of glucose based on the decreasing of cathodic peak current of oxygen. The detection limit, sensitivity and liner calibration rang were 1 μM, 18.3 μA/mM and 10 μM–6.0 mM, respectively. In addition biosensor can reach 90% of steady currents in about 3.0 s and interference effect of the electroactive existing species (ascorbic acid–uric acid and acetaminophen) is eliminated. The usefulness of biosensor for direct glucose quantification in human blood serum matrix is also discussed. This sensor can be used as an amperometric detector for monitoring oxidase based biosensors.     

Dispersing and functionalizing multiwalled carbon nanotubes in TiO2 sol

We report that oxidized multiwalled carbon nanotubes (MWCNTs) can be synchronously dispersed and functionalized in TiO2 sol via an in situ sol-gel process. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and atomic force microscopy (AFM) were used to characterize the functionalized MWCNTs. The results revealed that the hydrolysis and condensation originated from Ti(OC4H9)4 molecules favor the dispersion of MWCNTs in as-prepared TiO2 sol. Based on the strong interaction between the oxidized MWCNTs and TiO2 sol during the in situ sol-gel process, MWCNT (core)-TiOx (shell) tubular composites and TiO2 nanotubes can be obtained through filtrating, washing, and annealing of this kind of TiO2 sol containing functionalized MWCNTs, as revealed by TEM, XPS, Raman spectroscopy, and redispersion experiment. By casting the dilute dispersion of functionalized MWCNTs onto a hydrophilic Si surface, discrete and individual nanotubes can be observed by AFM.     

Direct Electrochemistry of Hemoglobin in Chitosan/Multiwalled Carbon Nanotubes/Ionic Liquid–Modified Carbon-Paste Electrode

Abstract

The direct electrochemistry of hemoglobin (Hb) was realized on chitosan and multiwalled carbon nanotubes (MWCNTs)–modified carbon ionic liquid electrode (CILE). The CILE was fabricated first and further modified by MWCNTs to get an electrode as MWCNTs/CILE. The Hb was immobilized on the surface of MWCNTs/CILE with the help of chitosan film. Ultraviolet–visible (UV-vis) and Fourier transform–infrared (FT-IR) spectra indicated that Hb kept its native structure in the modified film. A pair of well-defined quasi-reversible redox peaks of heme Fe(III)/Fe(II) couple appeared with the formal potential (E^0′) as ?0.314 V (vs. SCE) in pH 7.0 phosphate buffer solution (PBS). The modified electrode showed good electrocatalytic ability for the reduction of trichloroacetic acid.     

肌红蛋白-纳米氧化铝模板-金胶复合组装体的直接电化学与电催化

将肌红蛋白(Mb)固定在纳米氧化铝(AAO)模板-金胶复合组装体修饰玻碳电极表面,制得Mb/AAO/Au colloid/GC薄膜电极.在pH=5.4的HAc-NaAc缓冲溶液中,该薄膜电极于-0.21 V(vs.Ag/AgC l)处有一对准可逆的氧化还原峰,为Mb血红素辅基Fe(Ⅲ)/Fe(Ⅱ)电对的特征峰.在AAO/Au colloid薄膜的微环境中,Mb与玻碳电极间的电子传递明显加快,该Mb/AAO/Au colloid/GC薄膜电极还可用于过氧化氢和溶解氧的催化还原.     

血红蛋白在壳聚糖修饰碳纳米管上的电化学特性及对过氧化氢的电催化分析

用壳聚糖对多壁碳纳米管进行修饰,构建了一种用于固定血红蛋白的新型复合材料,并研究了血红蛋白在该碳纳米管上的电化学性质及其对过氧化氢的电催化活性.扫描电镜结果表明,壳聚糖修饰的多壁碳纳米管呈单一的纳米管状,并能均匀分散在玻碳电极表面.紫外光谱分析表明血红蛋白在该复合膜内能很好地保持其原有的二级结构.将该材料固定在玻碳电极上后,血红蛋白能成功地实现其直接电化学.根据峰电位差随着扫描的变化,计算得到血红蛋白在壳聚糖修饰的碳纳米管膜上的电荷转移系数为0.57,表观电子转移速率常数为7.02 s-1.同时,该电极对过氧化氢显示出良好的催化性能,电流响应信号与H2O2浓度在1.0×10-6 ～1.5×10-3 mol/L间呈线性关系,检出限为5.0×10-7 mol/L.修饰电极显示了良好的稳定性.     

多壁碳纳米管负载TiO_2复合器件可见光光催化降解RhB

采用溶胶-凝胶法制备了多壁碳纳米管(MWCNTs)负载的ITO/MWCNTs-TiO2/ITO复合器件,利用SEM、XPS、UV-Vis光谱等技术对复合样品进行形貌和结构表征,以液相罗丹明B(RhB)的可见光光催化降解为探针反应,评价MWCNTs-TiO2复合薄膜的催化活性.XPS结果表明MWCNTs与TiO2之间没有形成Ti-C键.I-V特性表明负载了MWCNTs的ITO/MWCNTs-TiO2/ITO复合器件的光电流增强.与空白TiO2薄膜相比,MWCNTs-TiO2复合薄膜的可见光光催化降解RhB的速率提高了3.2倍.MWCNTs并没有掺杂到TiO2晶格中,而是起到了类似光敏剂的作用,可在可见光激发下将导带电子转移到TiO导带上,经一系列反应降解RhB有机物.     

Electroless Deposition of Thionin onto Glassy Carbon Electrode Modified with Single Wall and Multiwall Carbon Nanotubes: Improvement of the Electrochemical Reversibility and Stability

A simple procedure was developed to prepare a glassy carbon electrode modified with carbon nanotubes (CNTs) and thionin. Abrasive immobilization of CNTs on a GC electrode was achieved by gently rubbing the electrode surface on a filter paper supporting carbon nanotubes, then immersing the GC/CNTs‐modified electrode into a thionin solution (electroless deposition) for a short period of time (5–50 s for MWCNTs and 5–120 s for SWCNTs ). Cyclic voltammograms of the resulting modified electrode show stable and a well defined redox couple with surface confined characteristic at wide pH range 2–12. The electrochemical reversibility and stability of modified electrode prepared with incorporation of thionin into CNTs film was compared with usual methods for attachment of thionin to electrode surfaces such as electropolymerization and adsorption on the surface of preanodized electrodes. The formal potential of redox couple (E°′) shifts linearly toward the negative direction with increasing solution pH. The surface coverage of thionin immobilized on CNTs glassy carbon electrode was approximately 1.95×10^?10 mol cm^?2 and 3.2×10^?10 mol cm^?2 for MWCNTs and SWCNTs, respectively. The transfer coefficient (α) was calculated to be 0.3 and 0.35 and heterogeneous electron transfer rate constants (K_s) were 65 s^?1 and 55 s^?1 for MWCNTs/thionin and SWCNTs/thionin‐modified GC electrodes, respectively. The results clearly show a great facilitation of the electron transfer between thionin and CNTs adsorbed on the electrode surface. Excellent electrochemical reversibility of redox couple, high stability, technically simple and possibility of preparation at short period of time are of great advantages of this procedure for modification of electrodes.     

Dye-sensitized solar cells based on multiwalled carbon nanotube-titania/titania bilayer structure photoelectrode

Dye-sensitized solar cells (DSSCs) were fabricated using multiwalled carbon nanotube (MWCNT)-TiO(2) nanocomposite as a light scattering layer. Morphology of the MWCNT-TiO(2) film was investigated by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). FESEM and TEM images demonstrate that MWCNTs and TiO(2) nanoparticles can be dispersed with chitosan. Internal resistance in the DSSC was characterized by electrochemical impedance spectroscopy (EIS). EIS results reveal a decrease in the charge resistance of electrolyte/dye/MWCNT-TiO(2)/TiO(2) interface with increasing MWCNT content up to 3 wt% which leads to an improvement in the photovoltaic performance. Compare with a nanocrystalline TiO(2) single-layer cell, the DSSC based on the MWCNT (3 wt%)-TiO(2)/TiO(2) bilayer structure photoelectrode shows ~100% increase in solar-to-electric energy conversion efficiency, which is attributed to the inclusion of MWCNTs in TiO(2) matrix.     

Electrodeposited nanogold decorated graphene modified carbon ionic liquid electrode for the electrochemical myoglobin biosensor

In this paper, a carbon ionic liquid electrode (CILE) was fabricated using ionic liquid 1-hexylpyridinium hexafluorophosphate as modifier, which was further in situ electrodeposited with graphene (GR) and gold nanoparticles step by step to get an Au/GR nanocomposite modified CILE. Myoglobin (Mb) was further immobilized on the Au/GR/CILE surface with Nafion film to get the modified electrode denoted as Nafion/Mb/Au/GR/CILE. Cyclic voltammetric experiments indicated that a pair of well-defined quasi-reversible redox peaks appeared in pH 3.0 phosphate buffer solution with the formal potential (E ^0′) located at ?0.197 V (vs. saturated calomel electrode), which was the typical characteristics of Mb heme Fe(III)/Fe(II) redox couples. Thus, the direct electron transfer rate between Mb and the modified electrode was promoted due to the high conductivity and increased surface area of Au/GR nanocomposite present on electrode surface. Based on the cyclic voltammetric data, the electrochemical parameters of Mb on the modified electrode were calculated. The Mb-modified electrode showed excellent electrocatalytic activities towards the reduction of trichloroacetic acid and H₂O₂ with wider linear range and lower detection limit. Using GR and Au nanoparticles modified CILE, a new third-generation electrochemical Mb biosensor was constructed with good stability and reproducibility.