Carbon Nanotube Composite Films Research Articles

Poly(Diphenylamine) with Multi-walled Carbon Nanotube Composite Film Modified Electrode for the Determination of Phenol

Poly(Diphenylamine) with Multi-walled Carbon Nanotube Composite Film Modified Electrode for the Determination of Phenol

Electron field emission from screen-printed graphene/DWCNT composite films

The electron field emission properties of graphene/double-walled carbon nanotube (DWCNT) composite films prepared by screen printing have been systematically studied. Comparing with the pure DWCNT films and pure graphene films, a significant enhancement of electron emission performance of the composite films are observed, such as lower turn-on field, higher emission current density, higher field enhancement factor, and long-term stability. The optimized composite films with 20% weight ratio of graphene show the best electron emission performance with a low turn-on field of 0.62Vμm−1 (at 1μAcm−2) and a high field enhancement factor β of 13,000. A model of the graphene/DWCNT composite films is proposed, which indicate that a certain amount of graphene will contribute the electron transmission in the silver substrate/composite films interface and in the interior of composite films, and finally improve the electron emission performance of the graphene/DWCNT composite films.

Simultaneous electrochemical determination of ascorbic acid, dopamine and uric acid using poly (tyrosine)/functionalized multi-walled carbon nanotubes composite film modified electrode

A novel poly (tyrosine)/carboxyl functionalized multi-walled carbon nanotubes composite film modified electrode has been fabricated and used as electrochemical sensor for simultaneous determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA). The prepared electrode not only separated the cyclic voltammetric signals of AA, DA and UA with oxidation potential difference of 160 and 150mV between AA–DA and DA–UA, respectively but also showed higher oxidation current for these molecules in pH 7.4 phosphate buffer solution. Because it exhibited excellent selectivity towards the oxidation of AA, DA and UA, the modified electrode was used for simultaneous voltammetric measurement of the three analytes by differential pulse voltammetry. Under the optimum conditions, the detection limits for AA, DA and UA were 2.0μmolL−1, 0.02μmolL−1 and 0.30μmolL−1, respectively (S/N of 3). The method has good selectivity and sensitivity and was successfully applied to the simultaneous determination of AA, DA and UA in spiked human serum.

Percolative BaTiO3/Carbon-Nanotube Composite Films Employing Aerosol Deposition

Percolative BaTiO3/multiwalled carbon nanotube (MWNT) composite thick films were developed using an aerosol deposition (AD) process at room temperature. Well-dispersed mixed powders with various volume ratios were utilized as the starting powders for AD, and dense BaTiO3/MWNT composite thick films were successfully fabricated with the starting mixed powders with 0.01 vol % MWNTs. The existence of MWNTs in the composite films was confirmed using Raman spectroscopy. The composite films show a high relative dielectric constant (657 at 1 kHz), which is approximately 7 times larger than that (91 at 1 kHz) of the BaTiO3 films. In addition, the strong frequency dispersion of the dielectric constant in the low-frequency range was confirmed for the composite films. The dielectric properties of the composite films were investigated using the dielectric mechanism used in percolative composites.

One-step fabrication of poly(o-aminophenol)/multi-walled carbon nanotubes composite film modified electrode and its application for levofloxacin determination in pharmaceuticals

In this study, one-step electrochemical polymerized method for the fabrication of poly(o-aminophenol)/multi-walled carbon nanotubes (PoAP/MWCNTs) composite film was developed for the quantitative determination of levofloxacin. Scanning electron microscopy and electrochemical methods were used to characterize the PoAP/MWCNTs nanocomposite film. The sensor fabricated from the nanocomposite film showed good stability and enhanced electrocatalytic ability for the detection of levofloxacin. The large current response of levofloxacin on PoAP/MWCNTs composite film-modified electrode could be ascribed to the synergistic effect of the electrocatalytic property of PoAP and MWCNTs. The oxidative peak current increased linearly with the concentration of levofloxacin in the range of 3.0–200 μM by differential pulse voltammetry, and the detection limit was 1.0 μM (S/N = 3). The proposed modified electrode also can be successfully applied to the determination of levofloxacin hydrochloride in pharmaceutical formulations.

Humidity sensing properties of different single-walled carbon nanotube composite films fabricated by layer-by-layer self-assembly technique

Poly(diallyldimethylammonium chloride)/single-walled carbon nanotube (PDDA/SWNT) multilayered thin films were prepared on quartz crystal microbalance by layer-by-layer self-assembly technique, and their sensing properties to humidity were studied. The SWNTs were characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The composite films were observed by field-emission scanning electron microscope. Two types of SWNT humidity sensors were fabricated using SWNTs and carboxyl (COOH) modified SWNTs as sensitive material, respectively. The results showed that the sensitivity of the PDDA/SWNT–COOH humidity sensor was 20.23 % higher than that of the PDDA/SWNT sensor. In contrast, the latter had a much superior hysteresis property, and the reason to cause this phenomenon was discussed.

Morphological and compositional engineering of Ni/carbon nanotube composite film via a novel cyclic voltammetric route

Ni/multi-walled carbon nanotubes (MWCNTs) composite films were deposited on the glassy carbon electrode (GCE) by a Ni plating bath containing homogeneously dispersed MWCNTs using polyvinylpyrrolidone (PVP) as dispersion additive. Incorporation of MWCNTs into Ni matrix was greatly enhanced by the application of cyclic voltammetric (CV) deposition technique. The structure and nature of the Ni/MWCNT were characterized by field emission scanning electron microscope (FE-SEM) and X-ray diffraction (XRD). The results show that the content of MWCNT and the morphology of the deposited Ni/MWCNT composite film can be controlled by selecting the appropriate electroplating conditions. Further study indicates that the obtained Ni/MWCNT showed excellent electro-catalytic activity for the oxidation of ethanol in alkaline solution.

Highly sensitive amperometric sensor for carbamazepine determination based on electrochemically reduced graphene oxide–single-walled carbon nanotube composite film

Abstract We report a highly sensitive amperometric sensor for the determination of carbamazepine (CBZ) at an electrochemically reduced graphene oxide (ERGO) and single walled carbon nanotube (SWCNT) composite film modified glassy carbon electrode (GCE). The π – π stacking interactions between ERGO and SWCNT add good stability to the composite film which was confirmed by UV–visible and FTIR spectroscopy. Compared with SWCNT modified electrode, ERGO–SWCNT composite film modified electrode exhibits a 3.2 fold enhancement in peak current for CBZ oxidation. The proposed sensor detects CBZ as low as 29 nM and has a sensitivity of 5.1076 μA μM −1 cm −2 in the linear range of 50 nM to 3 μM. The practicality of this sensor has been evaluated by the determination of CBZ from Tegratol tablets showing good sensitivity and linearity.

Rational Design of Amorphous Indium Zinc Oxide/Carbon Nanotube Hybrid Film for Unique Performance Transistors

Here we report unique performance transistors based on sol-gel processed indium zinc oxide/single-walled carbon nanotube (SWNT) composite thin films. In the composite, SWNTs provide fast tracks for carrier transport to significantly improve the apparent field effect mobility. Specifically, the composite thin film transistors with SWNT weight concentrations in the range of 0-2 wt % have been investigated with the field effect mobility reaching as high as 140 cm(2)/V·s at 1 wt % SWNTs while maintaining a high on/off ratio ∼10(7). Furthermore, the introduction SWNTs into the composite thin film render excellent mechanical flexibility for flexible electronics. The dynamic loading test presents evidently superior mechanical stability with only 17% variation at a bending radius as small as 700 μm, and the repeated bending test shows only 8% normalized resistance variation after 300 cycles of folding and unfolding, demonstrating enormous improvement over the basic amorphous indium zinc oxide thin film. The results provide an important advance toward high-performance flexible electronics applications.

Electrodeposited polyaniline/multi-walled carbon nanotube composites for solar cell applications

Polyaniline (PANI)/multi-walled carbon nanotube (MWNT) composite films were fabricated by an electrochemical polymerization of aniline with airbrushed MWNTs on ITO substrates. Structural, optical, and electrical properties of the films were studied by Raman, FTIR, optical absorption, and resistivity measurements. The incorporation of MWNTs in PANI was found to effectively increase the film conductivity with a percolation threshold of 5% of nanotubes in the composite. Organic–inorganic hybrid solar cells based on the composite films of different MWNT concentrations and TiO2 nanocrystals were investigated. It was found that the solar cell performance strongly depends on the conductivity of the composite films, which can be tuned by adjusting nanotube concentration. A higher conductivity resulted in a better cell performance, resulting from an efficient charge collection. This study indicates that PANI/MWNT composite films with optimized conductivity are potentially useful for low-cost hybrid solar cell applications.

Electrochemical oxidation behavior of methotrexate at DNA/SWCNT/Nafion composite film-modified glassy carbon electrode

Glassy carbon electrode modified with DNA-functionalized single-walled carbon nanotube (DNA/SWCNT) and Nafion composite film was developed for the detection of methotrexate. The characteristics of the modified electrode were examined by transmission electron microscopy and cyclic voltammetry. Compared with a bare glassy carbon electrode and Nafion- and SWCNT/Nafion-modified electrodes, the DNA/SWCNT/Nafion-modified one exhibited the more superior ability of detecting methotrexate, including the higher sensitivity and the lower overpotentials, due to the synergetic DNA-functionalized SWCNT and Nafion. Also, the dependence of the current on pH, nature of buffer, instrumental parameters, accumulation time, and potential was investigated to optimize the experimental conditions in the determination of methotrexate. Under the selected conditions, the modified electrode in pH = 2.78 Britton–Robinson buffer solutions showed a linear voltammetric response to methotrexate within the concentration range of 2.0 × 10−8–1.5 × 10−6 mol L−1, with the detection limit of 8.0 × 10−9 mol L−1. The method was also applied to detect methotrexate in medicinal tablets and spiked human blood serum samples.

Portable cholesterol detection with polyaniline-carbon nanotube film based interdigitated electrodes

Polyaniline-carboxylic multiwalled carbon nanotubes composite film (PANi-MWCNT) has been polymerized on the surface of interdigitated platinum electrode (fabricated by MEMS technology) which was compatibly connected to Autolab interface via universal serial bus (USB). An amperometric biosensor based on covalent immobilization of cholesterol oxidase (ChOx) on PANi–MWCNT film with potassium ferricyanide (FeCN) as the redox mediator was developed. The mediator helps to shuttle the electrons between the immobilized ChOx and the PANi-MWCNT electrode, therefore operating at a low potential of −0.3 V compared to the saturated calomel electrode (SCE). This potential precludes the interfering compounds from oxidization. The bio-electrode exhibits good linearity from 0.02 to 1.2 mM cholesterol concentration with a correlation coefficient of 0.9985.

Fabrication and characterisation of conducting composite films based on conducting polymers and functionalised carbon nanotubes

Electropolymerisation and characterisation of polyaniline film doped with functionalised single‐wall carbon nanotubes and different dopants were studied. These nanoporous composite films were grown electrochemically from aqueous solutions such that constituents were deposited simultaneously onto substrate electrode. The synthetic, morphological and electrical properties of obtained nanocomposite films were compared. SEM revealed that the composite films consisted of nanoporous networks of single‐wall carbon nanotubes coated with polymeric film. Cyclic voltammetry and electrochemical impedance spectroscopy demonstrated that these composite films had similar electrochemical response rates to pure polymeric films but a lower resistance and much improved mechanical integrity. The negatively charged functionalised carbon nanotubes served as anionic dopant during the electropolymerisation to synthesize polymer/functionalised carbon nanotube composite films. The specific electrochemical capacitance of the composite films is a significantly greater value than that for pure polymer films prepared similarly. Using these composite films, the modified electrodes with improved properties were obtained. Copyright © 2012 John Wiley & Sons, Ltd.

Effectively enhanced sensitivity of a polyaniline–carbon nanotube composite thin film bolometric near-infrared sensor

The polyaniline–carbon nanotube composite thin film bolometric near-infrared sensor exhibited more than a two orders of magnitude sensitivity enhancement over both the polyaniline thin film and carbon nanotube network NIR sensor. We also investigated the mechanism of the effectively enhanced sensitivity of the composite material and demonstrated that it is a synergistic effect due to the higher heat generation of carbon nanotubes and higher temperature coefficient of resistance of polyaniline.

A Review: Carbon Nanotube-Based Piezoresistive Strain Sensors

The use of carbon nanotubes for piezoresistive strain sensors has acquired significant attention due to its unique electromechanical properties. In this comprehensive review paper, we discussed some important aspects of carbon nanotubes for strain sensing at both the nanoscale and macroscale. Carbon nanotubes undergo changes in their band structures when subjected to mechanical deformations. This phenomenon makes them applicable for strain sensing applications. This paper signifies the type of carbon nanotubes best suitable for piezoresistive strain sensors. The electrical resistivities of carbon nanotube thin film increase linearly with strain, making it an ideal material for a piezoresistive strain sensor. Carbon nanotube composite films, which are usually fabricated by mixing small amounts of single-walled or multiwalled carbon nanotubes with selected polymers, have shown promising characteristics of piezoresistive strain sensors. Studies also show that carbon nanotubes display a stable and predictable voltage response as a function of temperature.

Increased response/recovery lifetimes and reinforcement of polyaniline nanofiber films using carbon nanotubes

We have prepared high surface area, conductive, mechanically robust, responsive polyaniline–carbon nanotube composite films. These were produced by filtration from dilute dispersions of polyaniline nanofibers and single-walled carbon nanotubes. Unlike polyaniline alone, these composites are mechanically stable, maintain large intractable surfaces and exhibit greatly enhanced response/recovery behavior to changes in their local environment. This is illustrated by exposing the films to ammonia.

On finding of high piezoresistive response of carbon nanotube films without surfactants for in-plane strain detection

The use of carbon nanotubes (CNTs) for construction of sensors is promising. This is due to some unique characteristics of CNTs. In recent years, strain sensors built from CNT composite films have been developed; however, their low piezoresistive sensitivity (gauge factor (GF)) in in-plane strain detection is a concern compared with other strain sensors. This article reports an experimental discovery of the superior piezoresistive response of a CNT film that is free of surfactants, known as the pure CNT film. The mechanism for the high GF with the pure CNT film strain sensors is also discussed.

Structure characterization and DC conductivity of honeycomb patterned poly(N‐vinylcarbazole)/multiwalled carbon nanotube composite film via pretreatment at high temperature

AbstractPoly(N‐vinylcarbazole) (PVK) composites containing different concentrations of multiwalled carbon nanotube (MWCNT) were synthesized through the oxidative polymerization of N‐vinylcarbazole with ferric chloride. The synthesized composites were characterized using Fourier transform infrared spectroscopy, ultraviolet‐visible spectra, and thermogravimetric analysis. A honeycomb‐patterned film was fabricated by casting the PVK–MWCNT composite solution under humid conditions. The morphology of the honeycomb‐patterned films in the PVK–MWCNT polymer composites and the dependence of its pore diameter and pore height on MWCNT concentration were analyzed using scanning electron microscopy. The honeycomb‐patterned films were treated at 150, 250, 400, and 490°C to study the arrangement of MWCNTs in the patterned films and to measure the DC conductivity depending on the calcination temperature. DC conductivity of the patterned films was increased by increasing the concentration of MWCNT in the composites and in the increased pretreatment temperature. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

Direct electrochemistry and electrocatalysis of horseradish peroxidase on a gold electrode modified with a polystyrene and multiwalled carbon nanotube composite film

We report on the direct electrochemistry and electrocatalysis of horseradish peroxidase immobilized on a composite matrix composed of polystyrene, multiwalled carbon nanotubes and Nafion on a gold electrode. The modified electrode was characterized by scanning electron microscopy, UV–vis and FT-IR spectroscopy. A pair of well-defined redox peak of HRP is obtained with the formal potential at −0.400 V at pH 7.0. The electron transfer rate constant is 1.15 s−1. The modified electrode exhibits excellent electrocatalytic activity to the reduction of H2O2, with a linear response in the 0.5 μM to 0.82 mM concentration range and a detection limit at 0.16 μM (S/N = 3). The apparent Michaelis-Menten constant is 0.66 mM. The modified electrode is biocompatible and conceived to serve as a versatile platform for the fabrication of electrochemical biosensors.

Fabrication of free-standing graphene composite films as electrochemical biosensors

We report a simple fabrication method for large-scale free-standing graphene–gold nanoparticle and graphene-single wall carbon nanotube composite films by using a centrifugal vacuum evaporation followed by a thermal reduction process. The homogeneous mixture of a graphene oxide (GO) suspension with gold nanoparticle (Au NP) or single wall carbon nanotube (SWCNT) is self-assembled at the air/liquid interface, resulting in the multilayered GO–Au NP and GO–SWCNT composite films. The cross-sectional image reveals that the graphene layers are orderly stacked in the reduced GO–Au NP film, while the reduced GO–SWCNT film shows a randomly packed morphology due to the dominant π–π interaction between the side wall of SWCNTs and the GO surfaces. In particular, the reduced GO–Au NP film shows an increased electrode kinetics and cyclic voltammetric response in proportion to the amount of Au NPs, and 3-fold enhancement of anodic peak current was observed compared with that of the reduced GO films. We employed the reduced GO–Au NP film as a matrix to immobilize tyrosinase enzyme for phenol detection, and the phenol-induced electrochemical catalytic reaction can be monitored with 3-fold higher sensitivity than the reduced GO film, demonstrating great potential of graphene composite as an electrochemical enzyme biosensor for environmental pollutant screening.