Carbon Nanotube Composite Films Research Articles

Regeneration of carbon nanotube and nanofibre composite film electrode for electrical removal of cupric ions

Low cost and large scale carbon nanotube and nanofibre (CNT-CNF) composite films have been fabricated and employed as electrodes for electrosorption of cupric ions. The regeneration of the saturated CNT-CNF film electrode has been investigated. Three methods (short-circuiting, short-circuiting and then reversing voltage, reversing voltage and then short-circuiting) are used for regeneration. The results show that low regeneration efficiency of CNT-CNF film electrode due to electrodeposition of Cu on the electrode surface can be highly improved by regeneration applying reverse voltage combined with short circuit. 93% regeneration efficiency can be achieved when 0.8 V reverse voltage is applied before short-circuiting during regeneration of CNT-CNF film electrode.

Electrical and optical percolations of polystyrene latex–multiwalled carbon nanotube composites

Electrical conductivity and optical transmittance properties of polystyrene (PS)–multiwalled carbon nanotube (MWCNT) composite films were investigated. Composite films were prepared by mixing of various mass fractions of MWCNT in PS–water dispersions. After water evaporates, powder composite films were annealed at 175 °C above the glass transition of PS for 20 min. Photon transmission and two point probe resistivity techniques were employed to determine the variations of the optical and the electrical properties of composites. Transmitted light intensity, I tr and surface resistivity, R s were monitored as a function of MWCNT mass fraction ( M). It was observed that, both the surface resistivity and the optical transparency were decreased by increasing the amount of MWCNT added to the polymeric system. Conductivity and optical results were interpreted according to the classical and site percolation theory, respectively. The electrical ( σ) and the optical ( op) percolation threshold values and critical exponents were calculated as M σ = 1.8 wt.%, M op = 0–0.13 wt.% and β σ = 2.25, β op = 0.32, respectively.

Recyclable and electrically conducting carbon nanotube composite films

Carbon nanotube (CNT) composite films possess unique electrical, mechanical and thermal properties. In particular, some research has shown that CNT-polymer composite films greatly enhance the performance of organic light-emitting diodes. Therefore, CNT composite films have been intensively fabricated and applied. However, recent research has shown that CNTs carry carcinogenic risks in vivo. Therefore, how to collect and treat damaged or trashed CNT composite films are considerable tasks for scientists working in this area. From the viewpoint of environmental protection and saving resources, recycling the CNT composite films is the most efficient way to solve these problems. Here, we employ a benign water-soluble polymer, polyethyleneimine (PEI), to disperse CNTs and a general spin-coating process to prepare the homogeneous CNT composite films. The prepared CNT composite films exhibit good water-soluble properties and recyclability, i.e. they can be formed and dissolved in water. In addition, the long CNTs and high loading in the PEI matrix facilitates good electric conductivity in these CNT composite films. A significant improvement in the conductivity of the composite films is observed as the concentration of CNTs in the PEI increases, reaching as high as 43.73 S cm(-1) when the CNT concentration is equal to 3%.

Direct electrochemistry and electrocatalysis of horseradish peroxidase immobilized in hyaluronic acid and single walled carbon nanotubes composite film

AbstractDirect electrochemistry and electrocatalysis of horseradish peroxidase (HRP) immobilized on a hyaluronic acid (HA)-single walled carbon nanotubes (SCNs) composite film coated glassy carbon electrode (GCE) was studied for the first time. HRP entrapped in the SCNs-HA composite film exhibited a pair of well-defined, quasi-reversible cyclic voltammetric peaks in a 0.1 M phosphate buffer solution (pH 7.0). Formal potential vs. standard calomel electrode (E°′) was −0.232 V, and E°′ was linearly dependent on the solution pH indicating that the electron transfer was proton-coupled. The current is linearly dependent on the scan rate, indicating that the direct electrochemistry of HRP in that case is a surface-controlled electrode process. UV-VIS spectrum suggested HRP retained its original conformation in the SCNs-HA film. Immobilized HRP showed excellent electrocatalysis in the reduction of hydrogen peroxide (H2O2).

A High-Luminescence Fringelike Field Emission from Screen-Printed Carbon Nanotube and Zinc Oxide Composite Film

A fringelike field emission with high-luminescence and stable emission current from screen-printed carbon nanotube mixed zinc oxide (CNT-ZnO) composite cathode was investigated. The luminescent patterns are significantly different from those observed in the field emission measure of pure CNT cathode. SEM images reveal that the CNTs are perfectly matched with ZnO powders by filling the interspaces in CNT film. XRD analysis demonstrates that the CNTs and ZnO have a high degree of crystalline perfection. Field emission measurement exhibits that the turn-on field of CNT-ZnO cathode is 2.08 V/µm, lower than 2.46 V/µm for pure CNT cathode. The large fringelike emission current at the brims of CNT-ZnO cathode is attributed to a combination of the increased effective contact area of CNTs, which decrease the sheet resistance of cathode film, and the dangled CNT bundles at the brims of CNT-ZnO film cathode.

Pore size control and electrochemical capacitor behavior of chemically activated polyacrylonitrile – Carbon nanotube composite films

Activated polyacrylonitrile (PAN)/carbon nanotube (CNT) composite film based electrodes have been prepared by chemical activation with potassium hydroxide for electrochemical capacitors. This paper analyses the following aspects of specific capacitance, pore size distribution and surface area: influence of activation temperature, molarity of activating agent, composition of PAN/carbon nanotube precursor films and electrolytes. A maximum value of specific capacitance of ∼302 Fg −1 was achieved for the samples activated at 800 °C. Energy density for PAN/CNT 80/20 sample when tested with ionic liquid/organic electrolyte system was as high as ∼22 W h kg −1. Pore size control predominantly below 5 nm was observed in these activated PAN samples. Data analysis showed that micropores make a significant contribution to the capacitance performance of these materials in both 6 M KOH as well as in BMIMBF 4/acetonitrile electrolytes.

Nafion/multi-wall carbon nanotubes composite film coated glassy carbon electrode for sensitive determination of caffeine

A Nafion/multi-wall carbon nanotubes (MWNTs) composite film-modified electrode was fabricated and applied for the sensitive and selective determination of caffeine. Multi-wall carbon nanotubes (MWNTs) were easily dispersed homogeneously into methanol by ultrasonication in the presence of 0.1% Nafion. After evaporating the methanol, a Nafion/MWNTs composite film-modified electrode was achieved. Caffeine can be effectively accumulated at Nafion/MWNTs composite film-modified electrode and produce a sensitive anodic peak at around 1330 mV (vs. SCE) in a 0.01 mol L 1 H2SO4 medium (pH 2.0). Compared to the bare electrode and Nafion film-modified electrode, the Nafion/MWNTs film-modified electrode can remarkably increase the anodic peak current of caffeine. Under the suitable conditions, the anodic peak current was linear to caffeine concentration in the range of 6.0 10 7 4.0 10

Sensitive voltammetric determination of Sudan I in food samples by using gemini surfactant–ionic liquid–multiwalled carbon nanotube composite film modified glassy carbon electrodes

A novel modified electrode was fabricated, which comprised of hydrophobic ionic liquid (i.e. trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide, [P 6,6,6,14][NTf 2]), multiwalled carbon nanotubes (MWNTs) and cationic genimi surfactant (i.e. C 12H 25N(CH 3) 2–C 4H 8–N(CH 3) 2C 12H 25Br 2, C 12–C 4–C 12). Cyclic voltammetry and linear sweep voltammetry were used to investigate the electrochemical behaviour of Sudan І. The components showed good synergic interaction in sensing Sudan І, thus the modified electrode presented higher sensitivity. After optimising the experimental conditions, the anodic peak current of Sudan I was linear to its concentration in the range of 0.05–2 μmol l −1, and the detection limit was 0.03 μmol l −1 in pH 4.5 potassium biphthalate buffer with acetonitrile. The modified electrode had good stability and repeatability. It was applied to the detection of Sudan І in hot chilli powder and ketchup samples, and the recovery was acceptable.

Simultaneous Voltammetric Detection of Salsolinol and Uric Acid in the Presence of High Concentration of Ascorbic Acid with Gold Nanoparticles/Functionalized Multiwalled Carbon Nanotubes Composite Film Modified Electrode

AbstractThis work demonstrates gold nanoparticles (AuNPs)/functionalized multiwalled carbon nanotubes (f‐MWCNT) composite film modified gold electrode via covalent‐bonding interaction self‐assembly technique for simultaneous determination of salsolinol (Sal) and uric Acid (UA) in the presence of high concentration of ascorbic acid (AA). In pH 7.0 PBS, the composite film modified electrode exhibits excellent voltammetric response for Sal and UA, while AA shows no voltammetric response. The oxidation peak current is linearly increased with concentrations of Sal from 0.24–11.76 μmol L−1 and of UA from 3.36–96.36 μmol L−1, respectively. The detection limits of Sal and UA is 3.2×10−8 mol L−1 and 1.7×10−7 mol L−1 , respectively.

The effect of length of single‐walled carbon nanotubes (SWNTs) on electrical properties of conducting polymer–SWNT composites

AbstractDC conductivity of conjugated polymer‐single‐walled carbon nanotube (SWNT) composite films has been measured for different SWNT concentrations. The composite was prepared by dispersing SWNTs in the poly (3‐octylthiophene), P3OT matrix already dissolved in xylene. The conductivity of the composite films showed a rapid increase as the SWNT concentration increases beyond a certain value. This behavior is explained in terms of percolating paths provided by the SWNTs in the volume of polymer matrix. To investigate the effect of length of nanotubes on the percolation conductivity, different SWNT samples were employed with similar diameter but varying tube lengths. It was found that the conductivity of the composite films is strongly dominated by the length of the nanotubes. Lower percolation limit and high conductivity value of composite films is observed for longer nanotubes. Furthermore, the conductivity is observed to be dependent on the size of the host polymer molecule also. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 89–95, 2010

Electrodeposition of Ni–P Alloy–Multiwalled Carbon Nanotube Composite Films

Ni–P alloy–multiwalled carbon nanotube (MWCNT) composite films were fabricated by an electrodeposition technique, and their microstructure, hardness, and frictional properties were analyzed. Ni–P alloy–MWCNT composite films containing 20–22 atom % P and 0.7–1.2 mass % MWCNTs were electrodeposited from a composite plating bath. MWCNTs were embedded relatively uniformly in the Ni–P alloy matrix. The hardness of the composite films was higher than that of the Ni–P alloy films, both before and after heat-treatment, and the friction coefficient of the composite films was lower than that of the Ni–P alloy films.

Al 3+-directed self-assembly and their electrochemistry properties of three-dimensional dendriform horseradish peroxidase/polyacrylamide/platinum/single-walled carbon nanotube composite film

A novel general methodology for protein immobilization and third-generation biosensor construction is demonstrated, which involves Al 3+-directed polyacrylamide (PAM) self-assembly into an ordered dendriform structure, easily immobilizing enzymes and nanoparticles. Platinum/single-walled carbon nanotube (Pt/SWCNT) heterojunction nanomaterials were for the first time fabricated via an EDTA-directed synthesis strategy. The Pt/SWCNTs were employed as a supporting matrix to explore a novel immobilization and biosensing platform of redox proteins through cooperating Al 3+-directed PAM self-assembly. Compared with the almost single-layer horseradish peroxidase (HRP)/PAM film electrode, multilayer HRP/PAM/Pt/SWCNT film electrode exhibited a pair of much stronger redox peaks at −0.22 V (vs. Ag/AgCl). Moreover, with advantages of the ordered multilayer HRP/PAM/Pt/SWCNT film, facilitated direct electron transfer of the metalloenzymes with an apparent heterogeneous electron transfer rate constant ( k s) of 14.94 ± 1.36 s −1 and smaller peak-to-peak separation (Δ E p) of about 37 mV was acquired on the PAM/Pt/SWCNT-based enzyme electrode. The PAM/Pt/SWCNT-based biosensor demonstrated significant electrocatalytic activity for the reduction of hydrogen peroxide with a small apparent Michaelis–Menten constant (87 μM), wide linear range (1–270 μM), very low detection limit (0.08 μM, S/ N = 3), and high sensitivity (372 mA cm −2 M −1). Together, these indicated that the Al 3+-directed HRP/PAM/Pt/SWCNT film was one of ideal candidate materials for direct electrochemistry of redox proteins and the construction of the related enzyme biosensors, and may find potential applications in biomedical, food, and environmental analysis and detection.

Humidity Sensitivity of Carbon Nanotube and Poly (Dimethyldiallylammonium Chloride) Composite Films

This paper demonstrates a highly sensitive humidity sensor based on carbon nanotube and poly(dimethyldiallylammonium chloride) composite films. The composite film is deposited between interdigitated electrodes on a Si/SiO2 substrate through layer-by-layer self-assembly technique. The resistance stability of the composite film is effectively improved through thermal annealing, and I-V characteristic of the film exhibits a very good linear behavior. The resistance increases exponentially with relative humidity from 20% to 98%, and a much higher sensitivity in comparison with pure carbon nanotube networks is achieved. With temperature increased, the water vapor density versus RH shifts upwards, while the resistance is reduced downwards. The resistance is dependent on temperatures with a negative coefficient. The composite films with multiwalled carbon nanotubes show an adjacent sensitivity, compared with the single-walled carbon nanotube composite films. The experimental results show that the humidity sensors have a fast response and a short recovery time, and their response is reversible. A simple model is proposed to explain the change of composite film resistance with humidity. The carbon nanotubes junctions may play a more important role in the overall resistance change for water molecule absorption.

Poly(malachite green) at nafion doped multi-walled carbon nanotube composite film for simple aliphatic alcohols sensor

Conductive composite film which contains nafion (NF) doped multi-walled carbon nanotubes (MWCNTs) along with the incorporation of poly(malachite green) (PMG) has been synthesized on glassy carbon electrode (GCE), gold and indium tin oxide (ITO) electrodes by potentiostatic methods. The presence of MWCNTs in the composite film (MWCNTs–NF–PMG) enhances surface coverage concentration ( Γ) of PMG to ≈396%, and increases the electron transfer rate constant ( k s) to ≈305%. Similarly, electrochemical quartz crystal microbalance study reveals the enhancement in the deposition of PMG at MWCNTs-NF film. The surface morphology of the composite film deposited on ITO electrode has been studied using scanning electron microscopy (SEM) and scanning tunneling microscopy (STM). These two techniques reveal that the PMG incorporated on MWCNTs–NF film. The MWCNTs–NF–PMG composite film also exhibits promising enhanced electrocatalytic activity towards the simple aliphatic alcohols such as methanol, ethanol and propanol. The electroanalytical responses of analytes at NF–PMG and MWCNTs–NF–PMG films were measured using both cyclic voltammetry (CV) and differential pulse voltammetry (DPV). From electroanalytical studies, well defined voltammetric peaks have been obtained at MWCNTs–NF–PMG composite film for methanol, ethanol and propanol at Epa = 609, 614 and 602 mV respectively. The sensitivity of MWCNTs–NF–PMG composite film towards methanol, ethanol and propanol in CV technique are 0.59, 0.36 and 0.92 μA mM −1 cm −2 respectively, which are higher than NF–PMG film. Further, the sensitivity values obtained using DPV are higher than the values obtained using CV technique.

The production of a flexible electroluminescent device on polyethylene terephthalate films using transparent conducting carbon nanotube electrode

An inorganic electroluminescent (EL) device on a flexible polyethylene terephthalate (PET) substrate and its properties were investigated. The transparent conducting film (TCF) made from carbon nanotubes (CNTs) (CNT-TCF) was employed in the flexible EL device. CNT-TCF was formed by filtration of CNT solution and was transferred to the PET film. It was found that the brightness of the inorganic EL device was strongly dependent on the quality of the CNT composite films. After a 3-aminopropyltriethoxysilane treatment of the PET substrate, CNTs uniformly were dispersed and showed a good adhesion to the substrate, and the resulting EL device showed better performance. The flexible EL device showed the brightness of 96.8 cd/m 2 at 28 kHz and 50 V.

Investigation on the thermal conductivity of HDPE/MWCNT composites by laser pulse method

Thermal conductivity (TC) of high density polyethylene/multiwall carbon nanotube (HDPE/MWCNT) composite films was measured by laser pulse method. It is found that the TC increased quickly with the increase of MWCNT fraction when the volume fraction of MWCNT was below 3.35%. However, as the volume fraction of MWCNT was over 3.35%, the increasing rate became slow. A new percolation model was proposed based on the effect of MWCNT network to simulate the TC of HDPE/MWCNT composite films. The simulation result was in good agreement the experimental data well. In addition, the relationship of TC with the increase of temperature was also discussed.

Gold–Carbon Nanotube Composite Plating Film Deposited Using Non-Cyanide Bath

We developed a gold–carbon nanotube (Au–CNT) composite plating film by electrodeposition. An effective additive was added into a non-cyanide CNT plating solution, affording an environmentally friendly method for fabricating an Au–CNT composite plating film using a basic solvent. The fabricated Au–CNT composite film was harder than the Au film by 1.4 times and showed a low friction coefficient. Thus, the Au–CNT composite film could be considered as a promising material for next-generation electrical contact applications.

Poly(3,4-ethylenedioxythiophene)−Multiwalled Carbon Nanotube Composite Films: Structure-Directed Amplified Electrochromic Response and Improved Redox Activity

Composite thin films of poly(3,4-ethylenedioxythiophene) (PEDOT)-enwrapped functionalized multiwalled carbon nanotubes (MWCNTs) have been synthesized over multiple length scales by electropolymerization of the monomer without the use of any other supporting electrolyte. The functionalized MWCNTs are incorporated into the positively charged polymer deposit as counterions during oxidative electropolymerization. The morphology, electrochemistry, and electrochromism of the PEDOT-MWCNT films have been compared with those of control PEDOT films doped by triflate ions. Such a comparison enabled us to demonstrate the profound effect of MWCNTs as counterions, realized in terms of better electropolymerization rate, higher conductivity, faster color-bleach kinetics, higher charge storage capacity, and substantially amplified coloration efficiency (eta = 414 cm(2) C(-1), lambda(max) = 575 nm, E = -1.5 V) in comparison to the values of eta reported to date for PEDOT. The strong interaction between the polymer and MWCNTs, the interconnected nanotubular structures, and the porous framework of the film allow facile charge transport and larger ion uptake during redox switching. Electrochemical investigations on devices based on PEDOT-MWCNT and control PEDOT films established the practical utility of PEDOT-MWCNT films as they show lower charge-transfer resistance, higher diffusional capacitance, and a much smaller amplitude of impedance as compared to control PEDOT films.

Electrosorption of anions with carbon nanotube and nanofibre composite film electrodes

The electrosorption of different salt solutions with carbon nanotube and nanofibre (CNT–CNF) composite film electrodes was studied. The electrochemical properties of CNT–CNF film were systematically investigated using ac impedance spectroscopy and cyclic voltammetry, and it was found that capacitive deionization (CDI) of CNT–CNF composite film electrodes is mainly due to Coulombic interaction on the electrical double-layer. Several experiments were conducted to determine the ion removal capacity and selectivity of CNT–CNF composite film electrodes, showing that smaller hydrated anions exhibit better CDI capacities.

Enhanced electrochemiluminescence of CdSe quantum dots composited with CNTs and PDDA for sensitive immunoassay

Electrochemiluminescence (ECL) of CdSe quantum dots (QDs) was greatly enhanced by the combination of carbon nanotubes (CNTs) and poly (diallyldimethylammonium chloride) (PDDA) in the CdSe QDs film, and could successfully be used to develop a sensitive ECL immunosensor for the detection of human IgG (Ag). The novel CdSe QDs–CNTs composites exhibited high ECL intensity, good biocompatibility, and high stability, which held great promise for the fabrication of the ECL biosensors with improved sensitivity. After PDDA as a binding linker was conjugated to the CdSe QDs–CNTs composite film on the electrode, the ECL signal was significantly enhanced. Subsequently, gold nanoparticles (GNPs) assembled onto the CdSe QDs–CNTs/PDDA modified electrode could amplify the ECL signal once again. After antibody (Ab) was immobilized onto the electrode through GNPs, the ECL immunosensor was successfully fabricated. It is for the first time that the unique function of PDDA for enhancing QDs ECL was explored and used to develop an ECL biosensor. The principle of ECL detection for target Ag is based on the increment of steric hindrance after immunoreaction, which resulted in the decrease of ECL intensity. The Ag concentration was determined in the linear range of 0.002–500 ng L −1 with a detection limit of 0.6 pg mL −1. The sensor showed good fabrication and detection reproducibility, and the assay results were in acceptable agreement with the clinical sera tests, showing a promising clinical application. This work opened the new avenues for applying QDs ECL in highly sensitive bioassays.