硝基苯在碳化钨/碳纳米管粉末微电极上的电化学行为

采用表面修饰和原位还原碳化技术制备了碳化钨（WC）/碳纳米管（CNT）纳米复合材料,并以其为电催化剂制成了WC/CNT纳米复合材料粉末微电极（WC/CNT-PME）。采用计时电流法、循环伏安法和原位红外反射光谱技术研究了酸性溶液中硝基苯在WC/CNT-PME上的电化学行为,讨论了扫描速率和温度对其电化学行为的影响。结果表明,WC/CNT纳米复合材料对硝基苯的电催化活性明显高于碳纳米管和纳米碳化钨;硝基苯在WC/CNT-PME上的还原反应是一受吸附控制的不可逆过程,其还原产物为对氨基苯酚。     

Electrochemical characterizations of carbon nanomaterials by the cavity microelectrode technique

The cavity microelectrode (CME) technique was used to screen carbide-derived carbons (CDC) and carbon onions and investigate their electrochemical performance for electrical double-layer capacitors (EDLC) in an H₂SO₄ electrolyte. The results show that the CME is very effective in terms of screening large numbers of powder samples rapidly, reliably, and efficiently, compared with conventional based electrochemical techniques using large surface electrodes. The results obtained from CME for CDC agree well with the conventional technique. High rate response was obtained with carbon onions because of their high graphitization degree. Therefore, the CME technique could also differentiate microstructure variation in powder materials, especially under high scan rate (as high as 10 V/s). These results show that, though the CME cannot completely replace conventional methods for electrochemical characterization of EDLCs, it is a complementary tool that can be used to quickly evaluate the performance of materials (combinatorial electrochemistry study) and highlight possible trends to explore using conventional techniques.     

Electrochemical determination of phloroglucinol using a carbon nanotube modified electrode enhanced by surfactant

A novel technique is utilized to detect trace amounts of phloroglucinol. In pH 5.0, 0.1 mol L⁻¹ HAc–NaAc buffer solution, phloroglucinol exhibited a stable and sensitive oxidation signal at a glassy carbon electrode modified with multi-wall carbon nanotube. By using the surfactant cetyl pyridinium chloride, the electrochemical response was greatly enhanced. The mechanism was systematically explored. In the range 9.0 × 10⁻⁷–3.0 × 10⁻⁴ mol L⁻¹, the oxidation peak currents of phloroglucinol have a linear relationship with concentration: the limit of detection was estimated to be 2.5 × 10⁻⁷ mol L⁻¹ (S/N = 3). The method was adopted to detect the content of phloroglucinol injection, and the recovery was from 97.5% to 103.0%.     

Electrochemical synthesis and characterization of N-substituted polypyrrole derivatives on nickel

1-Dodecylpyrrole (PyCH₃) and 12-(pyrrol-1-yl)dodecane-1-thiol (PySH) films have been successfully electrochemically polymerised on a nickel electrode from acetonitrile solutions containing the monomer and the lithium perchlorate as supporting electrolyte. The electrochemical study of the polymer growth has been carried out by cyclic voltammetry (CV) detecting the nickel dissolution during electropolymerisation. Several surface spectroscopic and microscopic techniques have been used to characterize the surface in term of chemical composition and polymer topography. The presence of unbound and unoxidised thiol groups at the PPySH surface has been evidenced together with a very strong adhesion to the nickel substrate. Furthermore, N-substituted pyrrole derivatives exhibited some corrosion protection properties in neutral NaCl medium.     

Preparation and characterization of polypyrrole/modified multiwalled carbon nanotube nanocomposites polymerized in situ in the presence of barium titanate

Polypyrrole (PPy) composites were prepared with both unmodified and amine‐modified multiwalled carbon nanotubes (MWCNTs) in the presence and absence of barium titanate (BaTiO₃) by in situ oxidative polymerization. A uniform coating of PPy on the MWCNTs and BaTiO₃ surfaces was confirmed by field emission scanning electron microscopy and high‐resolution transmission electron microscopy images. The structure of the pure and amine‐modified MWCNTs were identified by Fourier transform infrared spectroscopy. The incorporation of BaTiO₃ enhanced the thermal stability and capacitance properties of the composites. The maximum specific capacitance and energy density values found for the PPy/amine‐modified MWCNT/BaTiO₃ composites were 155.5 F/g and 21.6 W h/kg, respectively, at a scan rate of 10 mV/s. The maximum power density was found to be 385.7 W/kg for the same composite at a scan rate of 200 mV/s. Furthermore, the impedance spectra of the composites showed moderate capacitive behavior. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Electrochemical determination of thiamazole at a multi-wall carbon nanotube modified glassy carbon electrode

A simple and convenient method is described for voltammetric determination of thiamazole, a commonly used anti-hyperthyroid drug, based on its electrochemical oxidation at a multi-wall carbon nanotube modified glassy carbon electrode. Under optimized conditions, the proposed method exhibited acceptable analytical performances in terms of linearity (over the concentration range from 1.0 × 10⁻⁷ to 5.0 × 10⁻⁴ mol L⁻¹, r = 0.9983), detection limit (3.0 × 10⁻⁸ mol L⁻¹) and reproducibility (RSD = 2.64%, n = 10, for 5.0 × 10⁻⁵ mol L⁻¹ thiamazole). To further validate its possible application, the method was used for the quantification of thiamazole in pharmaceutical formulations and biological fluids.     

Synthesis and characterization of water‐soluble polypyrrole/multi‐walled carbon nanotube composites

Water‐soluble polypyrrole (PPy)/multi‐walled carbon nanotube (MWCNT) composites were prepared by mixing chemically modified MWCNTs carrying carboxylic groups (c‐MWCNTs) and sulfonated PPy (SPPy) aqueous colloids in solution. Fourier transform infrared spectroscopy, Raman spectroscopy, X‐ray photoelectron spectroscopy, X‐ray diffraction, field‐emission scanning electron microscopy and high‐resolution transmission electron microscopy were used to characterize the structure and morphology of the resulting composites. Raman and X‐ray photoelectron spectra demonstrate the presence of electrostatic interactions between the radical species of the SPPy and the carboxylic acid species of the c‐MWCNTs. The addition of c‐MWCNTs into SPPy efficiently enhances its thermal stability and electrical conductivity. Owing to the doping effect and one‐dimensional linear structure of the c‐MWCNTs, the conductivity of SPPy/c‐MWCNT composites at room temperature is increased by two orders of magnitude by the introduction of 5 wt% c‐MWCNTs into the SPPy matrix. Copyright © 2010 Society of Chemical Industry     

Electrochemical characterisation of patterned carbon nanotube electrodes on silane modified silicon

Previously we have used atomic force anodisation lithography, with a self-assembled monolayer of hexadecyltrichlorosilane as a resist, to pattern silicon oxide nanostructures onto a p-type silicon (1 0 0) substrate. A condensation reaction was used to immobilise carbon nanotubes with high carboxylic acid functionality directly to the silicon oxide. A further condensation reaction using this surface attached the molecule ferrocenemethanol to the bound nanotubes. These new nanostructures were used as electrodes to observe the oxidation and reduction of ferrocene. However, because the small currents measured are near the detection limits of the electrochemical system used, important electrode kinetics could not to be obtained. A scribing approach made larger regions of oxidised silicon leading to the creation of larger scale patterned arrangements of carbon nanotubes allowing measurement of important electrochemical parameters such as electrode kinetics, electron transfer rates and surface concentration of redox molecules. Knowledge of these characteristics has provided insights into the behaviour of the microelectrodes created using atomic force microscopy.     

Electrochemical behavior of glassy carbon electrodes modified by multi-walled carbon nanotube/surfactant films in a buffer solution and an ionic liquid

The electrochemical behavior of glassy carbon (GC) electrodes coated with multi-walled carbon nanotube (MWCNT)/surfactant films was studied in an ionic liquid and a phosphate buffer solution (pH = 6.86), using cyclic voltammetry. The dispersion of MWCNTs in different media was investigated by scanning and transmission electron microscopy. Cast films of MWCNT/zwitterionic dodecyldimethylamine oxide on a GC electrode show a typical redox couple in phosphate buffer solution, which is better than that of MWCNT/anionic sodium dodecyl sulfate and cationic alkyltrimethylammonium bromide. However in the ionic liquid, 1-n-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF₆]), the GC electrode modified by MWCNT/cationic surfactant films shows a well-defined irreversible reduction of MWCNTs. The cyclic voltammograms clearly show that the surfactant hydrophilic group plays an important role in the electrochemical behavior of the MWCNTs. The electrolytes also have an important effect. In an ionic liquid, the strong binding of the ionic liquid cations with the MWCNTs may change the structure of the modified films and lead to changes of electrochemical behavior.     

Electrochemical characterization of multi-walled carbon nanotube coated electrodes for biological applications

Carbon nanotubes, if used as a coating film on a conductive substrate, can substantially raise the charge storage capacity and lower the impedance of electrodes without significant increases to the geometric area. This is especially interesting in the case of stimulation of nervous tissue. We design implantable electrodes targeted at wide frequency stimulation of deep brain structures. Here we report on results in vitro with multi-walled carbon nanotubes coatings applied onto stainless steel substrates using direct current electrophoresis. We experimentally demonstrate, through electrochemical techniques such as cyclic voltammetry and impedance spectroscopy, the enhanced performance of multi-walled carbon nanotube (MWCNT) coatings for implantable electrodes by contrasting our experimental results against the more traditional stainless steel substrate characteristics. We also investigate surface morphology of aged electrodes. The interest in aged electrodes is dual fold: implantable electrodes have to be mechanically stable and present high shelf life. On the other hand, chemical modifications of the surface should be characterized. The effect of superficial oxygen adsorption on the aged MWCNT electrodes is observed through a modified cyclic voltammetric spectrum, but not through any changes in impedance spectroscopy.     

Design of carbon nanotube fiber microelectrode for glucose biosensing

BACKGROUND: Carbon nanotube (CNT) fiber directly spun from an aerogel has a unique, well‐aligned nanostructure (nano‐pore and nano‐brush), and thus provides high electro‐catalytic activity and strong interaction with glucose oxidase enzyme. It shows great potential as a microelectrode for electrochemical biosensors. RESULTS: Cyclic voltammogram results indicate that post‐synthesis treatments have great influence on the electrocatalytic activity of CNT fibers. Raman spectroscopy and electrical conductivity tests suggest that fibers annealed at 250 °C remove most of the impurities without damaging the graphite‐like structure. This leads to a nano‐porous morphology on the surface and the highest conductivity value (1.1 × 10⁵ S m^?1). Two CNT fiber microelectrode designs were applied to enhance their electron transfer behaviour, and it was found that a design using a 30 nm gold coating is able to linearly cover human physiological glucose level between 2 and 30 mmol L^?1. The design also leads to a low detection limit of 25 µmol L^?1. CONCLUSIONS: The high performance of CNT fibers not only offers exceptional mechanical and electrical properties, but also provides a large surface area and electron transfer pathway. They consequently make excellent bioactive microelectrodes for glucose biosensing, especially for potential use in implantable devices. Copyright © 2011 Society of Chemical Industry     

Benign enzymatic synthesis of multiwalled carbon nanotube composites uniformly coated with polypyrrole for supercapacitors

BACKGROUND: Recently, various composites of carbon nanomaterials and conducting polymers have been actively investigated as potential electrode materials for supercapacitors which can store and deliver large amounts of electrical energy promptly. Harsh chemical or complex electrodeposition methods have been studied to prepare such composites. In this report, the mild and simple enzymatic catalysis of horseradish peroxidase (EC 1.11.1.7) in aqueous solutions (pH 4.0) was utilized for the first time to prepare composites of multiwalled carbon nanotubes and polypyrrole. RESULTS: Electron micrographs show that in situ enzymatic reaction by horseradish peroxidase enables the uniform coating of multiwalled carbon nanotubes with polypyrrole without containing the polymer aggregates. The specific capacitance of the composites (46.2 F g^?1) measured with a two‐electrode cell containing an electrolyte of 1 mol L^?1 NaNO₃ increased more than four‐fold compared with that obtained with bare multiwalled carbon nanotubes (10.8 F g^?1). CONCLUSIONS: Horseradish peroxidase‐catalyzed in situ synthesis of the composites of multiwalled carbon nanotubes and polypyrrole requires neither the derivatization of multiwalled carbon nanotubes and/or pyrrole monomers nor the post‐doping of the synthesized composites to enhance the capacitance of the composites. © 2012 Society of Chemical Industry     

One-step microwave synthesis of palladium–carbon nanotube hybrids with improved catalytic performance

A fast and easy one-step linker-free approach for the synthesis of palladium nanoparticle/multiwall carbon nanotube (Pd-NP/MWCNT) hybrid materials is described using microwave irradiation for the effective decomposition of Pd₂dba₃ complex in the presence of MWCNTs. High loadings of Pd nanoparticles (up to 40 wt.%) having sizes between 3 and 5 nm are deposited on the surface of MWCNTs within a time of only 2 min. The Pd-NP/MWCNT materials serve as efficient catalysts in C–C coupling as well as in hydrogenation reactions, all characterized by high conversion rates using a small amount of catalysts, high turnover frequency values and good recyclability.     

Electrochemical synthesis of polypyrrole in ionic liquids

Electrochemical synthesis of inherently conducting polymers such as polypyrrole is traditionally performed in a molecular solvent/electrolyte system such acetonitrile/lithium perchlorate. We report the use of ionic liquids 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) amide and N,N-butylmethylpyrrolidinium bis(trifluoromethanesulfonyl) amide, both as the growth medium and as an electrolyte for the electrochemical cycling of polypyrrole films. Use of the ionic liquid as the growth medium results in significantly altered film morphologies and improved electrochemical activities.     

Preparation and characterization of polystyrene modified single‐walled carbon nanotube

A halogen atom terminated Polystyrene (PSt) was prepared by means of atom transfer radical polymerization. Then, the halogen atom was converted into ‐N₃ group and a ‐N₃ terminated PSt was obtained. Finally PSt was grafted onto the surface of single walled carbon nanotube (SWNT) by the reaction of azide group with SWNT. Comparison of X‐ray photoelectron spectrometer of N1s electron belonging to ‐N₃ and the surface of SWNT demonstrated that three‐membered rings were formed by releasing N₂ from ‐N₃ during the reaction. The structure of PSt modified SWNT was characterized by FTIR, UV, Raman spectrum, and TEM. The experimental results showed that the PSt was connected assuredly to SWNT by the covalent bond. TGA data showed that the amount of PSt on the surface of SWNT firstly increased with growing of PSt and then decrease when continues to grow. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Electrochemical synthesis of functional polypyrrole nanotubes via a self-assembly process

We successfully electrochemically polymerized functional polypyrrole (PPy) nanotubes via a self-assembly process in the presence of methyl orange (MO). The influence of polymerization conditions, such as working electrodes and electrochemical polymerization time, on the tubular morphology was discussed. A fibrillar precipitate of MO formed via electric flocculation on the electrode in a neutral aqueous solution prior to the polymerization of pyrrole and acted as a template for the subsequent growth of PPy nanotube. The importance of the MO aggregation in the forming process of PPy nanotubes was revealed by the observation that no tubular structure of PPy formed in dilute MO aqueous solution. The PPy-MO nanotubes obtained showed a high conductivity and an ability to alter photochemically the electrical behavior. In addition, as-prepared PPy tubes could be converted to the corresponding carbonized tubes when they were subjected to thermal treatment under an inert atmosphere.     

Synthesis and characterization of polyaniline/carbon nanotube composites

The synthesis of polyaniline (PANI) containing different carbon nanotubes (CNTs) by in situ polymerization is reported in this study. The samples were characterized by X‐ray diffraction and scanning electron microscopy. Fourier transform infrared and ultraviolet–visible spectroscopy were used to determine the change in structure of the polymer/CNT composites. Thermogravimetric analysis showed that the composites had better thermal stability than the pure PANI. Photoluminescence spectra showed a blueshift in the PANI–single‐walled nanotube (SWNT) composite. Low‐temperature (77–300 K) electrical transport properties were measured in the absence and presence of a magnetic field up to 1 T. Direct‐current conductivity exhibited a nonohmic, three‐dimensional variable range hopping mechanism. The room‐temperature magnetoconductivity of all of the investigated samples except the PANI–SWNT composite were negative; however, it was positive for the PANI–SWNT composite, and its magnitude decreased with increasing temperature. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Development and characterization of PEEK/carbon nanotube composites

New poly(ether ether ketone) (PEEK) based composites have been fabricated by the incorporation of single-walled carbon nanotubes (SWCNTs) using melt processing. Their structure, morphology, thermal and mechanical properties have been investigated. Scanning electron microscopy observations demonstrated a more uniform distribution of the CNTs for samples prepared following a processing route based on polymer ball milling and CNT dispersion in ethanol media. Thermogravimetric analysis indicated a remarkable improvement in the thermal stability of the matrix by the incorporation of SWCNTs. Differential scanning calorimetry showed a decrease in the crystallization temperature with increasing SWCNT content, whilst no significant changes were observed in the melting of the composites. The crystallite size determined by X-ray diffraction decreased at high SWCNT loading, which is attributed to the spatial limitations on crystal growth by confinement within the CNT network. Dynamic mechanical analysis revealed an increase in the storage moduli, hence in the rigidity of the systems, with increasing SWCNT content. Their addition shifts the glass transition peak to higher temperatures due to the restriction in chain mobility imposed by the CNTs. Higher thermal stability and mechanical strength were found for composites with improved dispersion of the SWCNTs.     

功能化改性碳纳米管接枝聚氯乙烯复合材料的制备及性能研究(一)——功能化改性碳纳米管的制备与表征

采用搅拌相转移酯化接枝反应、超声波酯化接枝反应和机械力相转移酯化接枝反应等方法制备了7种功能化改性碳纳米管,采用TGA考察了产物的接枝率和CNTs含量,并采用XPS和拉曼光谱进行了表征.TGA结果表明,适宜的制备工艺为:以羧基化CNTs、CEB为原料,以TOAB为催化剂,通过搅拌相转移酯化接枝反应来制备.XPS和拉曼光谱分析结果表明:CNTs表面成功接枝了功能性甲基苯乙烯基,并且上述适宜的制备工艺对CNTs管壁的损伤很小.     

Nano-composite of polypyrrole/modified mesoporous carbon for electrochemical capacitor application

Nano-thin polypyrrole (PPy) layers were coated on chemically modified ordered mesoporous carbon (m-CMK-3) by an in situ chemical polymerization. Structural and morphological characterizations of m-CMK-3/PPy composites were carried out using field emission scanning electron microscopy. Pseudo-capacitive behavior of the deposited PPy layers on m-CMK-3 was investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. As results of this study, the thin layer of PPy in the composite electrode was effective to obtain fully reversible and very fast Faradaic reaction. A maximum discharge capacity of 427 F g⁻¹ or 487 F g⁻¹ after correcting for weight percent of PPy phase at the current density of 5 mA cm⁻², could be achieved in a half-cell setup configuration for the m-CMK-3/PPy composites electrode, suggesting its potential application in electrode material for electrochemical capacitors.