以预锂化多壁碳纳米管为负极的锂离子电容器性能

采用内部短路方式对多壁碳纳米管负极进行不同程度的预嵌锂处理,预嵌锂时间为5,30,60min,以预嵌锂多壁碳纳米管极片作为负极,活性炭极片作为正极,组装成锂离子电容器。利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)对多壁碳纳米管及电极极片进行表征分析,采用恒流充放电(GCD)和交流阻抗谱(EIS)研究预嵌锂多壁碳纳米管负极和未预嵌锂处理多壁碳纳米管负极锂离子电容器的性能。电化学测试结果表明,多壁碳纳米管负极预嵌锂大幅提高了电容器充放电性能,对比未嵌锂多壁碳纳米管电容器,在相同的电流密度下(100mA/g),能量密度提高400%。预嵌锂60min,电流密度100mA/g时,其比容量达到57F/g。在电流密度为100～3200mA/g范围内,其最高能量密度与功率密度分别达到90Wh/kg,4130W/kg。1000次充放电循环后,容量保持率维持在85%以上,表现出良好的超级电容器性能。     

Multiwalled carbon-nanotube-functionalized microelectrode arrays fabricated by microcontact printing: platform for studying chemical and electrical neuronal signaling

A facile method is proposed for the deposition of multiwalled carbon nanotube (MWCNT) layers onto microelectrode arrays by means of a microcontact printing technique, leading to the fabrication of MEAs characterized by well defined electrical and morphological properties. Using polydimethyl siloxane stamps, produced from different mold designs, a flexibility of printing is achieved that provides access to microscale, nanostructured electrodes. The thickness of MWCNT layers can be exactly predetermined by evaluating the concentration of the MWCNT solution employed in the process. The electrode morphology is further characterized using laser scanning and scanning electron microscopy. Next, by means of impedance spectroscopy analysis, the MWCNT-electrode contact resistance and MWCNT film resistance is measured, while electrochemical impedance spectroscopy is used to estimate the obtained electrode-electrolyte interface. Structural and electrochemical properties make these electrodes suitable for electrical stimulation and recording of neurons and electrochemical detection of dopamine. MWCNT-functionalized electrodes show the ability to detect micromolar amounts of dopamine with a sensitivity of 19 nA μm(-1) . In combination with their biosensing properties, preliminary electrophysiological measurements show that MWCNT microelectrodes have recording properties superior to those of commercial TiN microelectrodes when detecting neuronal electrical activity under long-term cell-culture conditions. MWCNT-functionalized microelectrode arrays fabricated by microcontact printing represent a versatile and multipurpose platform for cell-culture monitoring.     

Multiwalled carbon nanotubes in alfalfa and wheat: toxicology and uptake

Data on the bioavailability and toxicity of carbon nanotubes (CNTs) in the environment, and, in particular, on their interactions with vascular plants, are limited. We investigated the effects of industrial-grade multiwalled CNTs (75 wt% CNTs) and their impurities on alfalfa and wheat. Phytotoxicity assays were performed during both seed germination and seedling growth. The germinations of both species were tolerant of up to 2560 mg l⁻¹ CNTs, and root elongation was enhanced in alfalfa and wheat seedlings exposed to CNTs. Remarkably, catalyst impurities also enhanced root elongation in alfalfa seedlings as well as wheat germination. Thus the impurities, not solely the CNTs, impacted the plants. CNT internalization by plants was investigated using electron microscopy and two-dimensional Raman mapping. The latter showed that CNTs were adsorbed onto the root surfaces of alfalfa and wheat without significant uptake or translocation. Electron microscopy investigations of internalization were inconclusive owing to poor contrast, so Fe₃O₄-functionalized CNTs were prepared and studied using energy-filter mapping of Fe₃O₄. CNTs bearing Fe₃O₄ nanoparticles were detected in the epidermis of one wheat root tip only, suggesting that internalization was possible but unusual. Thus, alfalfa and wheat tolerated high concentrations of industrial-grade multiwalled CNTs, which adsorbed onto their roots but were rarely taken up.     

基于溶胶-凝胶技术结合多壁纳米碳管化学修饰电极的方法制备高灵敏葡萄糖生物传感器的研究

基于多壁纳米碳管修饰铂电极与二氧化硅溶胶-凝胶(sol-gel)固定化酶相结合的技术制备了葡萄糖氧化酶传感器,充分利用了溶胶-凝胶固定化酶稳定的优点和纳米碳管的高灵敏电催化作用,优化了该酶传感器的制备过程,提高了传感器的电流响应和反应线性.结果表明,sol-gel构建的优化条件是:H2O:TEOS为2.5～3.5,TritonX-100浓度为5%,pH值为5.5.在本实验条件下,多壁纳米碳管的最适固定量为5μl(0.25g/L),溶胶-凝胶与酶的优化体积比为3:2.工作电位 0.55V、pH 6.5、25℃为制备传感器的最适工作条件.该传感器对葡萄糖在0.5～6 mmol/L呈线性响应,响应时间为20 s,检出限为0.05mmol/L,45天时的响应值仍保持90%.     

A novel hierarchically carbon foam templated carbon nanotubes/polyaniline electrode for efficient electrochemical supercapacitor

In this work, a high-performance electrode material has been fabricated by the incorporation of carbon nanotubes (CNTs) and polyaniline (PANI) on a carbon foams (CF) to improve its electrochemical performance. The microstructure and performance of as-prepared material was characterized in detail. Results showed that the resultant material exhibited a high gravimetric capacitance up to 467.1?F g^?1, higher energy density of 104. 2?Wh kg^?1 and power density of 3000?W kg^?1 at a current density 3?A g^?1 when the electrochemical doping time of PANI equals to 20?min. Furthermore, it appeared a good cycling stability with capacitance retention of 94.5% after 10000 cycles. The enhanced electrochemical performance can be attributed to the unique carbon nanostructure and synergistic effects of active materials CNTs and PANI. It indicates that this novel CF/CNTs/PANI-20 composite is a promising candidate for electrochemical capacitors.     

New route for bromination of multiwalled carbon nanotubes under mild and efficient conditions

A short study on bromination of multiwalled carbon nanotubes (MWCNTs) through new and convenient methods was reported. Bromine (Br) is chemically attached on MWCNTs surfaces through electrophilic addition and radical reactions using N-Bromosuccinimide (NBS), NH₄NO₃/NBS and Br₂ under thermal and UV conditions. Functionalized CNTs with Bromine groups, were characterized by Fourier transform infrared spectroscopy (FTIR), thermo gravimetric analysis (TGA), scanning electron microscopy and X-ray diffraction (XRD) methods.     

The role of functionalised multiwalled carbon nanotubes based supercapacitor for arsenic removal and desalination of sea water

In order to investigate the simultaneous adsorption property of functionalised multiwalled carbon nanotubes (MWNTs) for sodium and arsenic, a new type of carbon fabric supported functionalised MWNTs (f-MWNTs) based supercapacitor was developed. In addition, this setup was tested for desalination of sea water. MWNTs were synthesised by chemical vapour deposition technique and purified, followed by functionalisation. MWNTs were characterised by different techniques. Performance of supercapacitor-based water filter was analysed for the adsorption of high concentration of arsenic (trivalent and pentavalent) and sodium as well as for desalination of sea water by using cyclic voltametry and inductively coupled plasma-optical emission spectroscopy techniques. Adsorption isotherms and kinetic characteristics were studied for the simultaneous removal of sodium and arsenic. High desalination (removal of sodium and magnesium) efficiency of sea water and cyclic repeatability for simultaneous removal of arsenic (arsenate and arsenite) and sodium have been demonstrated in this study. Easy handling and flexibility of this new type of electrodes-based setup provides a platform for the development of portable water filter.     

Facile preparation of CuS-coated multiwalled carbon nanotubes for supercapacitor application: A study on the effect of electrolyte

CuS nanoparticles (CuS NPs) and CuS-coated multiwalled carbon nanotubes (CuS/MWCNT) are synthesized under ambient conditions. By comparing their supercapacitive performance in 6 M NaOH and 1 M Na₂SO₄, it is discovered that CuS NPs and CuS/MWCNT exhibit terrible cyclic stability in 6 M NaOH due to the conversion of CuS to Cu(OH)₂ during the GCD process. However, in 1 M Na₂SO₄, both CuS NPs and CuS/MWCNT show high specific capacitance and excellent cyclic stability.     

Single-walled carbon nanotubes modified carbon ionic liquid electrode for sensitive electrochemical detection of rutin

The single-walled carbon nanotubes (SWCNTs) modified carbon ionic liquid electrode (CILE) was designed and further used for the voltammetric detection of rutin in this paper. CILE was prepared by mixing graphite powder with ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate and liquid paraffin together. Based on the interaction of SWCNTs with IL present on the electrode surface, a stable SWCNTs film was formed on the CILE to get a modified electrode denoted as SWCNTs/CILE. The characteristics of SWCNTs/CILE were recorded by different methods including cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy. The electrochemical behaviors of rutin on the SWCNTs/CILE were investigated by cyclic voltammetry and differential pulse voltammetry. Due to the specific interface provided by the SWCNTs-IL film, the electrochemical response of rutin was greatly enhanced with a pair of well-defined redox peaks appeared in pH 2.5 phosphate buffer solution. The oxidation peak currents showed good linear relationship with the rutin concentration in the range from 1.0 × 10^− 7 to 8.0 × 10^− 4 mol/L with the detection limit as 7.0 × 10^− 8 mol/L (3σ). The SWCNTs/CILE showed the advantages such as excellent selectivity, improved performance, good stability and it was further applied to the rutin tablets sample detection with satisfactory results.     

Facile deposition of polyvinylpyrrolidone-grafted multi-walled carbon nanotube on glassy carbon electrode and its application in the sensing of biomolecules

Polyvinylpyrrolidone-grafted multi-walled carbon nanotube (PVP/MWCNT) was deposited on carboxylated glassy carbon electrode (GCE) from acidic water via the electrostatic force between the positively charged PVP/MWCNTs and negatively charged GCE. It was found out that PVP/MWCNT-modified GCE (PVP/MWCNT/GCE) exhibited great catalytic capability for the oxidation of dopamine (DA), uric acid (UA), tyrosine (Tyr) and nitrite) by enhancing their oxidation currents and lowering their overpotentials. For PVP/MWCNT/GCE, the linear calibration plots for DA, UA, Tyr and nitrite were obtained over the range of 0.1–50 μM, 1–500 μM, 1–200 μM and 1–500 μM with detection limits of 0.04 μM, 0.17 μM, 0.26 μM and 0.30 μM, respectively. In addition, satisfactory results were obtained by applying PVP/MWCNT/GCE in the determination of DA, UA, Tyr and nitrite in human serum samples with standard addition method.     

Direct evidence for lip-lip interactions in multi-walled carbon nanotubes

The stability of open edged multi-walled carbon nanotubes has been investigated by using in situ high resolution transmission electron microscopy at elevated temperatures. Formation of inter-shell structures was experimentally observed for the first time and attributed to a robust interaction between adjacent concentric shells (so-called lip-lip interaction). The fl uctuating behavior of the inter-shell structures suggests a mechanism by which the carbon atoms can pass in or out through the inter-shell edges during carbon nanotube growth or shrinkage processes. This article is published with open access at Springerlink.com     

Towards an ultrasensitive method for the determination of metal impurities in carbon nanotubes

Residual catalyst metal nanoparticles remain one of the major obstructions in the utilization of carbon nanotubes (CNTs) in many areas owing to their ability to participate in redox chemistry of biomarkers. Presented here is a comparative study of several techniques for quality control of carbon nanotubes in terms of metallic impurities, namely magnetic susceptibility, electron paramagnetic resonance, energy-dispersive X-ray spectrometry, X-ray photoelectron spectroscopy, and thermogravimetric analysis. It is found that the dc magnetic susceptibility is the most sensitive method such that the difference between two CNT samples that underwent slightly different treatments can be detected, whereas the two samples are indistinguishable by other techniques. Therefore, it is suggested that the most accurate statistical method for quality control of carbon nanotubes is dc magnetic susceptibility, which allows the detection of traces of magnetic metal impurities embedded in purified carbon nanotubes, whereas other methods may provide false "impurity-free" information.     

纳米碳管中离散分布的金属Ni纳米线气-液/固-固填充模型

以Ni∶Cr=3∶1的双金属层作为催化剂,用C2H2为碳源气体利用化学气相沉积(CVD)法,在不同的温度下制备纳米碳管.扫描电子显微镜(SEM)和透射电子显微镜(TEM)研究制备产物发现:当制备温度高于900℃时,没有纳米碳管生成,制备温度在700～800℃之间纳米碳管中填充有一些离散分布的金属Ni纳米线,制备温度在650℃有纳米碳管生成,但是纳米碳管中没有发现纳米线的填充.通过高分辨透射电子显微镜(HRTEM)分析发现,纳米线是以液态或是粘滞液态填充进纳米碳管.根据实验结果,提出了一个在本实验条件下纳米线填充进纳米碳管的气-液/固-固V- L/S -S(vapor- liquid/solid-solid)模型,这个模型能解释一些传统的V-L-S(vapor- liquid -solid)模型不能解释的实验现象.     

Novel ring structure for minimisation of screening effect in carbon nanotube based field emitters

Carbon Nanotubes (CNTs) are promising candidates for cold cathodes because of their high aspect ratio and robustness. However, the major hindrance in cold cathode based applications is the screening effect, which reduces the effective field at the tip and thereby the current density. The emission current can be improved by minimising the screening effect. The adverse effect of screening can be addressed by either controlling the growth density or by optimising the patterns of CNT cathodes. Here, novel patterns have been used to increase edge length per unit area in planar vertically aligned CNT bundles. Our motive was to increase the number of effective emitters, since the CNT at the edges are less screened by the proximal CNTs. By varying geometry and spacing of solid CNT dot patterns and by introducing the square ring structures; we could successfully enhance the effective emitters at the edges. It has been observed that an enhancement of edge length from 0.032 per micron to 0.2 per micron increases the current density from 0.71mA/cm² to 16.2 mA/cm² at a field of 4.5 V/μm. CNTs in dotted structure with high value of edge length per unit area emit very high current density as compared to other dotted structures with low value of edge length per unit area Simulation studies confirms our argument that CNTs at the corners are the least screened and have the maximum local electric field.     

载气在CVD法制备纳米碳管工艺中的作用

纳米碳管是性能优异的具有准一维特征的纳米材料,CVD法是制备纳米碳管的典型工艺之一。本文以乙炔气体为原料气体、循环失效后的贮氢电极舍金材料作为反应催化剂,研究了在相同反应条件下,CVD法制备纳米碳管过程中载气对纳米碳管形貌和产率的影响。通过对产物TEM观察和TG分析发现,虽然载气不直接参与合成反应但对产物产率和形貌有很大的影响,氢气作为载气可以获得形貌和热稳定性更好的纳米碳管。     

Voltammetric sensor based on carbon paste electrode modified with molecular imprinted polymer for determination of sulfadiazine in milk and human serum

A new sensitive voltammetric sensor for determination of sulfadiazine is described. The developed sensor is based on carbon paste electrode modified with sulfadiazine imprinted polymer (MIP) as a recognition element. For comparison, a non-imprinted polymer (NIP) modified carbon paste electrode was prepared. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods were performed to study the binding event and electrochemical behavior of sulfadiazine at the modified carbon paste electrodes. The determination of sulfadiazine after its extraction onto the electrode surface was carried out by DPV at 0.92 V vs. Ag/AgCl owing to oxidation of sulfadiazine. Under the optimized operational conditions, the peak current obtained at the MIP modified carbon paste electrode was proportional to the sulfadiazine concentration within the range of 2.0 × 10^? 7–1.0 × 10^? 4 mol L^? 1 with a detection limit and sensitivity of 1.4 × 10^? 7 mol L^? 1 and 4.2 × 10⁵ μA L mol^? 1, respectively. The reproducibility of the developed sensor in terms of relative standard deviation was 2.6%. The sensor was successfully applied for determination of sulfadiazine in spiked cow milk and human serum samples with recovery values in the range of 96.7–100.9%.