The intermediate frequency modes of single- and double-walled carbon nanotubes: a Raman spectroscopic and in situ Raman spectroelectrochemical study

The intermediate frequency modes (IFM) of single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs) were analyzed by Raman spectroscopy and in situ Raman spectroelectrochemistry. The inner and outer tubes of DWCNTs manifested themselves as distinct bands in the IFM region. This confirmed the diameter dependence of IFM frequencies. Furthermore, the analysis of inner tubes of DWCNTs allowed a more-precise assignment of the bands in the IFM region to features intrinsic for carbon nanotubes. Although the inner tubes in DWCNTs are assumed to be structurally perfect, the role of defects on IFM was discussed. The dependence of IFM on electrochemical charging was also studied. In situ spectroelectrochemical data provide a means to distinguish the bands of the outer and inner tubes.     

碳纳米管的电化学贮氢性能研究

研究了碳纳米管电极的电化学性能 ,其电化学储氢量达到 2 0 0mAh·g 1且具有高的电化学活性和良好的循环寿命 .采用循环伏安法研究了氢在碳纳米管电极上吸附 /氧化机理 .     

Effects of Precursors and Carbon Nanotubes on Electrochemical Properties of Electrospun Nickel Oxide Nanofibers-Based Supercapacitors

Supercapacitors have been considered as one of the main energy storage devices. Recently, electrospun nanofibers have served as promising supercapacitor electrodes because of their high surface area, high porosity, flexibility, and resistance to aggregation. Here, we investigate the effects of electrospinning parameters and nickel precursors on the nanostructure of electrospun nickel oxide (NiO), as well as on their electrochemical performance as supercapacitor electrodes. In contrast to the case of using nickel nitrate, increasing the nickel acetate molar concentration maintains the flexible fibrous sheet morphology of the as-spun sample during the polycondensation and calcination of NiO. As a result, our flexible electrode of NiO nanofibers derived from nickel acetate (NiO-A) exhibits much better electrochemical performance values than that of nickel nitrate-derived NiO. To further improve the electrochemical storage performance, we combined NiO-A nanofibers with single-walled carbon nanotubes (CNTs) as a hybrid electrode. In both half-cell and full-cell configurations, the hybrid electrode displayed a higher and steadier areal capacitance than the NiO-A nanofibers because of the synergetic effect between the NiO-A nanofibers and CNTs. Altogether, this work demonstrates the potency of the hybrid electrodes combined with the electrospun NiO-A nanofibers and CNTs for supercapacitor applications.     

The characteristics of highly ordered mesoporous carbons as electrode material for electrochemical sensing as compared with carbon nanotubes

In this paper, the unique properties of highly ordered mesoporous carbons modified glassy carbon electrode (OMCs/GE) are illustrated from comparison with carbon nanotubes modified glassy carbon electrode (CNTs/GE) for the electrochemical sensing applications. Electrochemical behaviors of eight kinds of inorganic and organic electroactive compounds were studied at OMCs/GE, which shows more favorable electron transfer kinetics than that at CNTs/GE. Especially, OMCs/GE exhibits remarkably strong and stable electrocatalytic response toward NADH compared with CNTs/GE. The ability of OMCs to promote electron transfer not only provides a new platform for the development of dehydrogenase-based bioelectrochemical devices, but also indicates a potential of OMCs in a wide range of sensing applications. OMCs prepared are the novel carbon electrode materials, exhibiting more favorable electrochemical reactivity than CNTs for the wide electrochemical sensing applications without pretreatments, while purification or end-opening processing was usually required in case of CNTs.     

Hydrous manganese oxide/carbon nanotube composite electrodes for electrochemical capacitors

A novel type of composite electrode based on hydrous manganese oxide and a single-walled carbon nanotube has been prepared and used in electrochemical capacitors. Cyclic voltammetry, galvanostatic charging/discharging tests and electrochemical impedance measurements were applied to investigate the performance of the composite electrodes with different ratios of hydrous manganese oxide and single-walled carbon nanotube. For comparison, the performance of pure hydrous manganese oxide and pure carbon nanotubes was also studied. In this way, the composite electrode with a 6:4 ratio of hydrous manganese oxide to carbon nanotube was found to be the most promising active material for an electrochemical capacitor, which shows both good capacitance and power characteristics.     

碳纳米管修饰电极同时测定邻苯二酚和对苯二酚

用十二烷基磺酸钠(SDS)分散碳纳米管(CNTs),通过层层组装(LBL)聚二甲基二烯丙基氯化铵(PDDA)和CNTs构筑PDDA/CNTs多层膜电极.利用紫外-可见光谱法对PDDA/CNTs多层膜的组装过程进行监测,用循环伏安法(CV)和差分脉冲伏安法(DPV)研究了邻苯二酚和对苯二酚同时存在时PDDA/CNTs多层膜电极上的电化学行为.结果表明,碳纳米管修饰电极对邻苯二酚和对苯二酚有较好的电催化活性和电分离作用,邻苯二酚和对苯二酚无需经过分离即可同时被检出.在修饰电极上的线性范围如下:邻苯二酚为2.0×10-6~1.4×10-4mol/L,线性相关系数R=0.9991;对苯二酚为2.0×10-6~1.4×10-4mol/L,线性相关系数R=0.9987.     

Carbon nanotubes as a conductive additive in LiFePO<Subscript>4</Subscript> cathode material for lithium-ion batteries

The electrochemical properties and cyclic performances of commercial LiFePO₄ cathode material with different ratio of carbon black (CB) and carbon nanotubes (CNTs) as conductive material were tested in this study. Compared with other samples, the sample with 3 wt % CNTs exhibited the best electro-chemical and cyclic performances at various discharging rate at room temperature; and adhesion strength of electrode was improved by adding CNTs. The enhanced electrode performance may due to the unique natures of CNTs and the contact area of CNTs with active material or current collector.     

Nanographite impurities in carbon nanotubes: their influence on the oxidation of insulin, nitric oxide, and extracellular thiols

There has been growing interest in the use of modified-carbon-nanotube electrodes in applications such as the electrochemical detection of biologically significant compounds, owing to their apparent "electrocatalytic" properties and ability to enhance oxidative signals. In spite of their salient properties, little work has been done to further examine the reasons for these reported characteristics. In this report, we present clear evidence that the presence of nanographite impurities within carbon nanotubes (CNTs) is responsible for providing the previously reported enhanced electrochemical response. We have demonstrated this effect on homocysteine, N-acetyl-L-cysteine, nitric oxide, and insulin, which are important biological agents in the body. Moreover, we also showed that the influence of nanographite impurities on the electrochemistry of carbon nanotubes is prevalent among a variety of CNTs, such as single-walled CNTs, double-walled CNTs, and few-walled CNTs. Our findings will have a profound influence upon the biomedical applications of CNTs.     

Bulk synthesis of linear carbon chains confined inside single-wall carbon nanotubes by vacuum discharge

Carbyne, an infinite carbon chain, has attracted much interest and induced significant controversy for many decades. Recently, the presence of linear carbon chains (LCCs), which were confined stably inside double-wall carbon nanotubes (DWCNTs) and multiwall carbon nanotubes (MWCNTs), has been reported. In this study, we present a novel method to produce LCCs in a film of carbon nanotubes (CNTs). Our transmission electron microscopy and Raman spectroscopy revealed the formation of a bulk amount of LCCs after electric discharge of CNT films, which were used as field emission cathodes. The LCCs were confined inside single-wall CNTs as well as DWCNTs. Furthermore, two or three LCCs in parallel with each other are encapsulated when the inner diameter of CNT is larger than approximately 1.1 nm.     

Performance of dye-sensitized solar cells with various carbon nanotube counter electrodes

Double-wall carbon nanotubes (DWCNTs), single-wall carbon nanotubes (SWCNTs), and multi-wall carbon nanotubes (MWCNTs) were investigated as an alternative for platinum in counter-electrodes for dye-sensitized solar cells. The counter-electrodes were prepared on fluorine-doped tin oxide glass substrates by the screen printing technique from pastes of carbon nanotubes and organic binder. The solar cells were assembled from carbon nanotubes counter-electrodes and screen printed anodes made from titanium dioxide. The cells produced with DWCNTs, SWCNTs or MWCNTs have overall conversion efficiencies of 8.0%, 7.6% and 7.1%, respectively. Electrochemical impedance spectroscopy measurements revealed that DWCNTs displayed the highest catalytic activity for the reduction of tri-iodide ions. The large surface area and superior chemical stability of the DWCNTs facilitated the electron-transfer kinetics at the interface between counter-electrode and electrolyte and yielded the lowest transfer resistance, thereby improving the photovoltaic activity. A short-term stability test at moderate conditions confirmed the robustness of solar cells based on the use of DWCNTs, SWCNTs or MWCNTs.

曲克芦丁在羧基化单壁碳纳米管修饰电极上的电化学氧化

研制了羧基化单壁碳纳米管修饰玻碳电极( SWCNTs - COOH/GCE).用交流阻抗谱法(EIS)和扫描电镜( SEM)研究了电极膜性能,应用循环伏安法(CV)考察了曲克芦丁在修饰电极上的电化学行为.结果表明,SWCNTs - COOH修饰电极对曲克芦丁的氧化有良好的电催化活性,其氧化反应为单电子单质子过程,结合恒...     

The direct electrochemistry of glucose oxidase based on the synergic effect of amino acid ionic liquid and carbon nanotubes

Amino acid ionic liquids (AAILs) have attracted much attention due to their special chemical and physical properties, especially their outstanding biocompatibility and truly green aspect. In this work, a novel electrochemical biosensing platform based on AAILs/carbon nanotubes (CNTs) composite was fabricated. AAILs were used as a novel solvent for glucose oxidase (GOD) and the GOD-AAILs/CNTs/GC electrode was conveniently prepared by immersing the carbon nanotubes (CNTs) modified glassy carbon (GC) electrode into AAILs containing GOD. The direct electrochemistry of GOD on the GOD-AAILs/CNTs/GC electrode has been investigated and a pair of reversible peaks was obtained by cyclic voltammetry. The immobilized glucose oxidase could retain bioactivity and catalyze the reduction of dissolved oxygen. Due to the synergic effect of AAILs and CNTs, the GOD-AAILs/CNTs/GC electrode shows excellent electrocatalytic activity towards glucose with a linear range from 0.05 to 0.8 mM and a detection limit of 5.5 μM (S/N = 3). Furthermore, the biosensor exhibits good stability and ability to exclude the interference of commonly coexisting uric and ascorbic acid. Therefore, AAILs/CNTs composite can be a good candidate biocompatible material for the direct electrochemistry of the redox-active enzyme and the construction of third- generation enzyme sensors.     

碳纳米管/五氧化二钒空心球的制备及其电化学性能研究

采用溶剂热法制备了碳纳米管穿插的分级结构五氧化二钒空心球（VOC_x）. 使用XRD、SEM、循环伏安曲线和充放电曲线研究了不同碳纳米管量对产物结构、形貌和电化学性能的影响. 结果表明,碳纳米管的加入明显改善了VOC的倍率特性. 碳纳米管含量为7.1%时,0.5 A·g^-1电流密度下,其比电容达到346 F·g^-1,8 A·g^-1电流密度时,其电容保持率可达75%. 与活性炭组装成混合电容器,在功率密度为700 W·kg^-1时,能量密度达12.6 Wh·kg^-1.     

Effect of the Dispersing Agent on the Electrochemical Response of Glassy Carbon Electrodes Modified with Dispersions of Carbon Nanotubes

The electrochemical response of a glassy carbon electrode modified with carbon nanotubes (CNT) dispersed in two solvents, water and DMF, and two polymers, chitosan and Nafion is reported. The films were homogeneous when the dispersing agent was water or DMF. In the case of polymers, the surfaces present areas with different density of CNTs. A more sensitive electrochemical response was obtained when CNTs are dispersed in the solvents. In the case of CNT dispersed with polymers, the nature of the polymer demonstrated to be a critical parameter not only for dispersing the nanotubes but also for the electrochemical activity of the resulting electrodes.     

蒿甲醚在单壁碳纳米管修饰电极上的电催化还原

研制了单壁碳纳米管(SWCNTs)修饰玻碳电极。用交流阻抗谱法(EIS)和扫描电镜(SEM)研究了电极膜性能,应用循环伏安法(CV)、计时库仑法(CC)、计时电流法(CA)研究了蒿甲醚在修饰电极上的电化学行为。结果表明,SWCNTs修饰电极对蒿甲醚的还原有良好的电催化活性,其还原反应为双电子过程,电极反应的扩散系数及速率常数分别为6·67×10-4cm2·s-1及8·54×10-2mol·L-1·s-1。在优化实验条件下,还原峰的峰电位位于-0·85V,其峰电流与蒿甲醚浓度在6·71×10-7~2·45×10-4mol·L-1范围内呈良好线性,检出限达4·02×10-7mol·L-1,相对标准偏差(n=10)为4·2%,可用于蒿甲醚样品的含量测定。     

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.     

基于纳米金／壳聚糖掺杂碳纳米管修饰金电极非标记免疫传感器的研究

应用吸附法将羊抗人IgG抗体直接固定于纳米金(GNPs)/壳聚糖(Chit)掺杂碳纳米管(CNTs)修饰的金电极表面,制备了用于人IgG抗原检测的非标记电化学免疫传感器.利用循环伏安法和交流阻抗研究了修饰电极表面的电化学特性,用差分脉冲伏安法研究了测试底液的pH值对免疫传感器性能的影响.实验表明,在含不同浓度人IgG的...     

AAO-CNTs electrode on microfluidic flow injection system for rapid iodide sensing

In this work, carbon nanotubes (CNTs) nanoarrays in anodized aluminum oxide (AAO-CNTs) nanopore is integrated on a microfluidic flow injection system for in-channel electrochemical detection of iodide. The device was fabricated from PDMS (polydimethylsiloxane) microchannel bonded on glass substrates that contains three-electrode electrochemical system, including AAO-CNTs as a working electrode, silver as a reference electrode and platinum as an auxiliary electrode. Aluminum, stainless steel catalyst, silver and platinum layers were sputtered on the glass substrate through shadow masks. Aluminum layer was then anodized by two-step anodization process to form nanopore template. CNTs were then grown in AAO template by thermal chemical vapor deposition. The amperometric detection of iodide was performed in 500-μm-wide and 100-μm-deep microchannels on the microfluidic chip. The influences of flow rate, injection volume and detection potential on the current response were optimized. From experimental results, AAO-CNTs electrode on chip offers higher sensitivity and wider dynamic range than CNTs electrode with no AAO template.     

Electrochemistry and electroanalytical applications of carbon nanotubes: a review.

This review addresses recent developments in electrochemistry and electroanalytical chemistry of carbon nanotubes (CNTs). CNTs have been proved to possess unique electronic, chemical and structural features that make them very attractive for electrochemical studies and electrochemical applications. For example, the structural and electronic properties of the CNTs endow them with distinct electrocatalytic activities and capabilities for facilitating direct electrochemistry of proteins and enzymes from other kinds of carbon materials. These striking electrochemical properties of the CNTs pave the way to CNT-based bioelectrochemistry and to bioelectronic nanodevices, such as electrochemical sensors and biosensors. The electrochemistry and bioelectrochemistry of the CNTs are summarized and discussed, along with some common methods for CNT electrode preparation and some recent advances in the rational functionalization of the CNTs for electroanalytical applications.     

The advantage of using carbon nanotubes compared with edge plane pyrolytic graphite as an electrode material for oxidase-based biosensors

Carbon nanotubes (CNTs) are promising materials for use in amperometric biosensors. The defect sites at their ends, and on their sidewalls, are considered to be edge plane-like defects and show high electrocatalytic activity toward several biological molecules. However, electrocatalytic activity toward H(2)O(2) has not been compared among bamboo-structured CNTs (BCNTs), which have many defect sites; hollow-structured CNTs (HCNTs), which have few defect sites; edge plane pyrolytic graphite (EPG); and traditional glassy carbon (GC). The advantages of using CNTs in electrodes for biosensors are still equivocal. To confirm the utility of CNTs, we analyzed the electrochemical performance of these four carbon electrodes. The slope of the calibration curve for H(2)O(2) at potentials of both +0.6 V and -0.1 V obtained with a BCNT paste electrode (BCNTPE) was more than 10 times greater than the slopes obtained with an HCNT paste electrode and a GC electrode, reflecting the BCNT's larger number of defect sites. Although the slope with the EPG electrode (EPGE) was about 40 times greater than that with BCNTPE at +0.6 V, the slopes with these two carbon electrodes were nearly equivalent at -0.1 V. EPGE demonstrated excessive electrochemical activity, detecting currents on the basis of consumption of oxygen and oxidation of ascorbic acid, even at -0.1 V. In contrast, BCNTPE could dominantly detect a cathodic current for H(2)O(2) at -0.1 V, even when interfering molecules were added. BCNTPE possesses appropriate electrochemical activity and is an effective electrode materials for developing interference-free oxidase-based biosensors operated by the application of an appropriate potential.