延胡索乙素在碳纳米管修饰玻碳电极上的电化学检测

本文建立了延胡索乙素在碳纳米管修饰玻碳(CNT/GC)电极上的电化学检测方法。在pH6.20的Michaelis.缓冲液中,用方波伏安法研究了延胡索乙素在CNT/GC电极上的电化学行为。延胡索乙素在+0.90v(vs.Ag/AgCl)左右产生一个灵敏的阳极氧化峰,峰电流与延胡索乙素的浓度在8.0×10-7～5.0×10-5mol/L范围内呈良好线性关系,最低检测限达3.0×10-7mol/L。该法简单、快速、灵敏,可应用于生药材和中成药中延胡索乙素的测定。     

Electrochemical sensor for selective determination of N-acetylcysteine in the presence of folic acid using a modified carbon nanotube paste electrode

In the present paper, a novel benzoylferrocene (BF) modified carbon nanotube paste electrode (BFCNPE) was prepared. The modified electrode was further used for the successful determination of N-acetylcysteine (NAC), and it showed an excellent electrocatalytic oxidation activity toward NAC with a lower overvoltage, pronounced current response, and good sensitivity. Under the optimized experimental conditions, the proposed electrochemical NAC sensor exhibited a linear calibration plot that ranged from 3.0 × 10^? 7 to 7.0 × 10^? 4 M with a detection limit of 9.0 × 10^? 8 M. Also, Square wave voltammetry (SWV) was used for simultaneous determination of NAC and folic acid (FA) at the modified electrode. Finally, the proposed method was applied to the determination of NAC in NAC tablets.     

Electrochemical detection of nitrite based on the polythionine/carbon nanotube modified electrode

In this paper, thionine was electro-polymerized onto the surface of carbon nanotube (CNT)-modified glassy carbon (GC) to fabricate the polythionine (PTH)/CNT/GC electrode. It was found that the electro-reduction current of nitrite was enhanced greatly at the PTH/CNT/GC electrode. It may be demonstrated that PTH was used as a mediator for electrocatalytic reduction of nitrite, and CNTs as an excellent nanomaterial can improve the electron transfer between the electrode and nitrite. Therefore, based on the synergic effect of PTH and CNTs, the PTH/CNT/GC electrode was employed to detect nitrite, and the high sensitivity of 5.81 μA mM^− 1, and the detection limit of 1.4 × 10^− 6 M were obtained. Besides, the modified electrode showed an inherent stability, fast response time, and good anti-interference ability. These suggested that the PTH/CNT/GC electrode was favorable and reliable for the detection of nitrite.     

Electrochemical behaviour and voltammetric determination of sulphadiazine using a multi-walled carbon nanotube composite film-glassy carbon electrode

The anodic oxidation of sulphadiazine (SD) was investigated at a glassy carbon electrode modified by multi-walled carbon nanotube (MWCNT–GCE), using cyclic voltammetry and chronoamperometry. The results indicate that MWCNT-modified GCEs show an efficient and selective electrocatalytic activity towards the anodic oxidation of SD among biologically important compounds in buffered solutions at pH?=?7. It was found that oxidation of SD at the surface of MWCNT–GCE occurs at a potential less positive than that of unmodified GCE (about 100?mV). The diffusion coefficient of SD was also estimated using chronoamperometry. The kinetic parameters such as the electron transfer coefficient between SD and modified electrode, α, and the charge transfer rate constant, k_s , for oxidation of SD at the MWCNT–GCE surface were determined according to the Laviron procedure. The dissociation constants of oxidised and reduced acid–base species of SD can be obtained from the E _1/2 versus pH curves. The linear dependence of the peak current on the concentration was observed in the range 10–2000?µmol?L^?1 with a detection limit of 7.1?µmol?L^?1. The method was also applied to determinate the SD in human blood plasma and urine samples.     

Enhanced electrochemical detection of DNA hybridization with carbon nanotube modified paste electrode

A novel electrochemical genesensor using twice hybridization enhancement of gold nanoparticles based on carbon paste modified electrode is described. The carbon nanotube modified carbon paste electrode (CNTPE) and mesoporous molecular sieve SBA-15 modified carbon paste electrode (MSCPE) were investigated. The assay relies on the immobilization of streptavidin-biotin labeled target oligonucleotides onto the electrode surface and its hybridization to the gold nanoparticle-labeled DNA probe. After twice hybridization enhanced connection of gold nanoparticles to the hybridized system, the differential pulse voltammetry (DPV) signal of total gold nanoparticles was monitored. It was found that the adsorption of oligonucleotide and hybridized DPV signal on CNTPE were both enhanced in comparison with that of pure carbon paste electrode (CPE). But this trend was reverse on MSCPE. The DPV detection of twice hybridized gold nanoparticles indicated that the sensitivity of the genesensor enhanced about one order of magnitude compared with one-layer hybridization. One-base mismatched DNA and complementary DNA could be distinguished clearly. However, no distinct advantage of MSCPE over CPE was found.     

Electrochemical reduction of nitrobenzene at carbon nanotube electrode

The electrochemical behaviors of nitrobenzene at a pyrolytic graphite electrode modified with carbon nanotubes (CNTs) were studied using cyclic voltammetry and constant-potential electrolysis technique, and the CNT-modified electrode was characterized with Fourier transform infrared spectroscopy (FTIR), high resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM) measurements. A CNT-modified packed-bed flow reactor was also constructed for electrocatalytic reduction of nitrobenzene. The results showed that CNTs exhibited high activity for nitrobenzene reduction to aniline and the electrochemical reduction of nitrobenzene at CNT-modified electrode followed the pathway of nitrobenzene-->phenylhydroxylamine-->aniline. CNTs had been functionalized with profuse carboxylic group and other oxygen-containing groups, became open with some lacuna on the wall, and were distributed symmetrically on the electrode with forming a three-dimensional layer, resulting in the high catalytic-activity for nitrobenzene reduction to aniline. The removal of nitrobenzene was over 95% with electrolysis for 50 min at -1.20 V in pH 5 solution using the CNT-modified packed-bed flow reactor, and no other product was obtained except aniline. The removal of nitrobenzene was over 95% with electrolysis for 80 min at -1.20 V in pH 7 solution and was 87% with electrolysis for 120 min in pH 9 solution. A little phenylhydroxylamine besides aniline was obtained during the initial electrolysis stage, and then all reduced to aniline. The average current efficiency at pH 5, 7 and 9 was 46, 51 and 63%, respectively. The electrolysis products were mineralized easily through aerobiotic biodegradation.     

Flexible single walled nanotube based chemical sensor for 2,4-dinitrotoluene sensing

In this work, we have attempted to fabricate flexible single walled carbon nanotube based sensor for detection of 2,4-dinitrotoluene (DNT) an explosive chemical. For analyte sensing study, the flexible sensor is fabricated by vacuum filtration method. These fabricated gas sensors are characterised by SEM and Raman spectroscopy. The sensor response is investigated toward the explosive chemicals which have NO₂ group in their molecular structure. The fabricated sensor is able to detect the traces of DNT at room temperature. The sensor gives 0.28–0.32% repeatable response to 0.22 ppm of DNT. The response of sensor increases with increase in the vapour concentration of the DNT vapours.     

Synthesis and characterization of nano-scale alumina on single walled carbon nanotube

In this study, nano-scale crystalline alumina was synthesized on single walled carbon nanotube by sol-gel method for using as a sorbent for solid phase extraction of trace metals. The characterization of the synthesized nanocomposite material was performed by scanning electron microscope, transmission electron microscope and X-ray diffractometer methods. It was proved that the obtained composite material was mainly nano-scale Al₂O₃, and partly Mg₂Al₂O₄ and Zn₂Al₂O₄ on single walled carbon nanotube. In addition, the specific surface area of the material was determined and found as 165 m²/g. The adsorption capacity of the nanomaterial was also determined for cadmium(II) ions and found as 2.18 mg/g at pH 8.     

Properties of surface treated transparent conducting single walled carbon nanotube films

Transparent conducting single-walled carbon nanotube (SWCNT) films were fabricated using the spin coating technique. UV-ozone treated and poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) coated glass substrates together with SWCNT dispersed in 1,2-dichlorobenzene were used to promote the adhesion of SWCNT at room temperature. The produced film had a sheet resistance of 430 Ω/□ for 80% optical transparency at 550 nm. The spin coated SWCNT film after a post fabricated treatment in a mixer of isopropyl alcohol and nitric acid solution had a sheet resistance as low as 120 Ω/□ for 80% optical transparency at 500 nm. Besides reduction in sheet resistance, we obtained stable and strongly adherent SWCNT films on substrate that could serve as an alternative to transparent conducting oxides in display and optoelectronic applications.     

Buckling analysis of single walled carbon nanotube on Winkler foundation using nonlocal elasticity theory and DTM

In the present work differential transformation method (DTM) is used to predict the buckling behaviour of single walled carbon nanotube (SWCNT) on Winkler foundation under various boundary conditions. Four different boundary conditions namely clamped–clamped, simply supported, clamped hinged and clamped free are used to study the critical buckling loads. Effects of (i) size of SWCNT (ii) nonlocal parameter and (iii) Winkler elastic modulus on nonlocal critical buckling loads are being investigated and discussed. The DTM is implemented for the nonlocal SWCNT analyses and this yields results with high degree of accuracy. Further, present method can be applied to linear and nonlinear problems.     

聚苯胺修饰活性炭电极电化学性能

采用循环伏安法在活性炭电极（AC）表面合成导电聚苯胺，得到聚苯胺修饰活性炭复合电极（PAn／AC），通过循环伏安（CV）、恒流充放电技术研究了电极的电容特性，并计算了其等效串联电阻。结果表明，在硫酸溶液中，复合电极呈现较好的电容特性，复合电极的比电容能达到545F／g，比纯活性炭电极的306F／g提高了78％，不同放电电流密度下求出的比电容比纯活性炭电极平均提高了89％，且复合电极的ESR比AC电极稍小。     

Enhanced cellular activation with single walled carbon nanotube bundles presenting antibody stimuli

Efficient immunotherapy can be accomplished by expanding T cells outside the body using single walled carbon nanotube (SWNT) bundles presenting antibody stimuli. Owing to the large surface area of these bundles, which can reach 1560 m (2)/g, T cell stimulating antibodies such as anti-CD3, can be presented at high local concentrations inducing potent activation of T cells. We show that anti-CD3 adsorbed onto SWNT bundles stimulate cells more effectively than equivalent concentrations of soluble anti-CD3. Stimulation by antibody adsorbed onto SWNT is significantly higher than other high surface area materials (activated carbon, polystyrene, and C60 nanoparticles), suggesting unique properties of SWNT bundles for stimuli presentation. We demonstrate the surface area tunability of these bundles by chemical treatment and its effect on antibody adsorption and subsequent T cell activation. In addition, the T cell response varied with the concentration of SWNT in a concentration dependent manner. Antibody stimuli adsorbed onto SWNT bundles represent a novel paradigm for efficient activation of lymphocytes, useful for basic science applications and clinical immunotherapy.     

DNA-linker-induced surface assembly of ultra dense parallel single walled carbon nanotube arrays

Ultrathin film preparations of single-walled carbon nanotube (SWNT) allow economical utilization of nanotube properties in electronics applications. Recent advances have enabled production of micrometer scale SWNT transistors and sensors but scaling these devices down to the nanoscale, and improving the coupling of SWNTs to other nanoscale components, may require techniques that can generate a greater degree of nanoscale geometric order than has thus far been achieved. Here, we introduce linker-induced surface assembly, a new technique that uses small structured DNA linkers to assemble solution dispersed nanotubes into parallel arrays on charged surfaces. Parts of our linkers act as spacers to precisely control the internanotube separation distance down to <3 nm and can serve as scaffolds to position components such as proteins between adjacent parallel nanotubes. The resulting arrays can then be stamped onto other substrates. Our results demonstrate a new paradigm for the self-assembly of anisotropic colloidal nanomaterials into ordered structures and provide a potentially simple, low cost, and scalable route for preparation of exquisitely structured parallel SWNT films with applications in high-performance nanoscale switches, sensors, and meta-materials.     

Electrochemical determination of arsenite using a gold nanoparticle modified glassy carbon electrode and flow analysis

A flow analysis electrochemical system has been developed, characterized, and optimized for the determination of arsenite (As(III)). Sensitivity was significantly improved by the electrochemical deposition of gold nanoparticles on a dual glassy carbon electrode, which was inserted into a cross-flow thin-layer electrochemical cell. The electrochemical system was linear up to 15 ppb with a detection limit of 0.25 ppb. Gold deposition was evident from cyclic voltammetry measurements, whereas atomic force microscopy and scanning electron microscopy revealed the size and distribution of deposited gold nanoparticles. The size and density of the nanoparticles were related to the gold salt concentration, deposition time, and potential as well as the electrode position. The response to arsenite was directly related to the frequency, increment, and amplitude of the square wave voltammetry as well as the deposition time and potential. Estimated reproducibility was +/-1.1% at 95% confidence interval for 40 repeated analyses of 8 ppb arsenite during continuous analysis. The reproducibility was far superior if the electrochemical reduction of arsenite was performed in nitric acid instead of hydrochloric or sulfuric acid. The electrochemical system was applicable for analysis of spiked arsenic in mineral water containing a significant amount of various ion elements.     

Determination of serotonin on a glassy carbon electrode modified by electropolymerization of meso-tetrakis(2-aminophenyl)porphyrin and single walled carbon nanotubes

A chemically modified electrode [poly(TAPP)-SWNT/GCE] was prepared by electropolymerization of meso-tetrakis(2-aminophenyl)porphyrin (TAPP)-single walled carbon nanotubes (SWNT) on the surface of a glassy carbon electrode (GCE). This modified electrode was employed as an electrochemical biosensor for the determination of serotonin concentration and exhibited a typical enhance effect on the current response of serotonin and lower oxidation overpotential. The biosensor was very effective to determined 5-HT in a mixture. The linear response was in the range 2.0 x 10(-7) to 1.0 x 10(-5) M, with a correlation coefficient of 0.999 [i(p)(microA) = 3.406 C (microM)+0.132] on the anodic current, with a detection limit of 1 x 10(-9) M. Due to the relatively low currents and different potentials in the electrochemical responses to ascorbic acid and dopamine, the modified electrode is a useful and effective sensing device for the selective and sensitive serotonin determination in the presence of ascorbic acid and dopamine.     

Efficient charge carrier control on single walled carbon nanotube thin film transistors using water soluble polymer coatings

SWCNT-based thin-film transistors (TFTs) typically display unipolar p-type electrical characteristics in ambient condition due to the O₂/H₂O redox couple. However, complementary circuits that combine both p and n channels are preferred due to lower power requirements. Typical approaches with small molecule or polymeric dopants often yield ambipolar devices, or unstable n-type devices while concomitantly suppressing the on-current and mobility. Herein, we demonstrate a charge carrier control strategy using aqueous-based polymeric coatings that enable n-type devices with comparable performance to p-type devices. Specifically, we used a polyvinyl alcohol (PVA) coating layer containing a minority fraction of polyethyleneimine (PEI) (0.06–1.1?% w/w) to effectively switch the transfer characteristics from p-type to n-type, while maintaining decent electrical characteristics. Moreover, we demonstrate the ability to fine-tune the n branch threshold voltage via the annealing temperature. A similar strategy provides a balanced p branch on-current by incorporating PVA as a minor component (0.1-6?% w/w) into a polyacrylic acid (PAA) matrix. Through effective n-type conversion and p-type balancing, we demonstrate a simple SWCNT-based inverter. Considering the low-cost, environmentally friendly compositions and aqueous processability, this approach is attractive for large scale complementary printable circuits.

     

Conductivity of a single DNA duplex bridging a carbon nanotube gap

We describe a general method to integrate DNA strands between single-walled carbon nanotube electrodes and to measure their electrical properties. We modified DNA sequences with amines on either the 5' terminus or both the 3' and 5' termini and coupled these to the single-walled carbon nanotube electrodes through amide linkages, enabling the electrical properties of complementary and mismatched strands to be measured. Well-matched duplex DNA in the gap between the electrodes exhibits a resistance on the order of 1 M(Omega). A single GT or CA mismatch in a DNA 15-mer increases the resistance of the duplex approximately 300-fold relative to a well-matched one. Certain DNA sequences oriented within this gap are substrates for Alu I, a blunt end restriction enzyme. This enzyme cuts the DNA and eliminates the conductive path, supporting the supposition that the DNA is in its native conformation when bridging the ends of the single-walled carbon nanotubes.     

Chemical vapour deposition of single walled carbon nanotubes freely suspended over nanotube supports

Single walled carbon nanotubes (SWNTs) suspended above the substrate can be fabricated simply and rapidly by chemical vapour deposition growth over pre-grown multi-walled carbon nanotubes (MWNTs). SWNTs are suspended either on a randomly organized carbon nanotube network on an unpatterned substrate, or between organized pillars made from vertically aligned nanotube forests on a patterned substrate. All nanotubes are produced during a single growth run using a two step growth technique. This approach enables the fabrication of laterally suspended SWNT networks which are well suited for optical applications.     

多壁碳纳米管填充丁苯橡胶复合材料的研究

采用浓硝酸(HNO3)氧化处理后的多壁碳纳米管(MWNTs)与丁苯橡胶(SBR)及其他配合剂在开炼机上进行混炼加工制备MWNTs／橡胶复合材料，并与炭黑补强橡胶体系进行对比，进而研究了MWNTs／橡胶复合材料的物理性能，并初步探讨了该材料微观结构与性能之间的关系。结果表明：随着MWNTs质量百分含量的增加，橡胶复合材料的力学性能也随之增高；MWNTs／橡胶复合材料的抗撕裂强度(25．9kN／m)、硬度(58)、磨耗(0．22mL/1．61km)性能较炭黑／橡胶体系要好。由MWNTs补强的橡胶对开发具有低滚动滞后性和抗疲劳损失的轮胎胎面胶将有很大的实用潜力。     

Determination of cyanide in wastewaters using modified glassy carbon electrode with immobilized silver hexacyanoferrate nanoparticles on multiwall carbon nanotube

The sensitive determination of cyanide in wastewaters using modified GC electrode with silver hexacyanoferrate nanoparticles (SHFNPs) immobilized on multiwall carbon nanotube (MWCNT) was reported. The immobilization of SHFNPs on MWCNT was confirmed by transmission electron microscopy (TEM). The TEM image showed that the SHFNPs retained the spherical morphology after immobilized on MWCNT. The size of SHFNPs was examined around 27 nm. The GC/MWCNT-SHFNPs was used for the determination of cyanide in borax buffer (BB) solution (pH 8.0). Using square wave voltammetry, the current response of cyanide increases linearly while increasing its concentration from 40.0 nM to 150.0 μM and a detection limit was found to be 8.3 nM (S/N=3). The present modified electrode was also successfully used for the determination of 5.0 μM cyanide in the presence of common contaminants at levels presenting in industrial wastewaters. The practical application of the present modified electrode was demonstrated by measuring the concentration of cyanide in industrial wastewater samples. Moreover, the studied sensor exhibited high sensitivity, good reproducibility and long-term stability.