Multi-walled Carbon Nanotube Composite Films Research Articles

Synthesis of cadmium oxide and carbon nanotube based nanocomposites and their use as a sensing interface for xanthine detection

Xanthine oxidase (XOD) was immobilized covalentlyviacarbodiimide chemistry onto cadmium oxide nanoparticles (CdO)/carboxylated multiwalled carbon nanotube (c-MWCNT) composite film electrodeposited onto Au electrode.

Carbon Nanotube Composite Mesh Film with Tunable Optoelectronic Performance

In this study we fabricated novel transparent composite electrodes based on multi-walled carbon nanotubes (MWCNTs) and sodium dodecyl sulfate (SDS). The target optoelectronic properties of the flexible composite films are ± 100 Ω/sq at 77% transmission of 550 nm light based on the properties of indium tin oxide (ITO) films on poly-ethylene terephthalate (PET). The optical properties of the MWCNTs composite thin films were measured in the UV-Vis and IR regions. The corresponding band-gap of composite films was 3.82 eV and complementary to the band-gaps’ of dye-sensitized and organic solar cell components. The band-gaps of films deposited between 30 minutes and 60 minutes were tunable. Composite films over PET had tunable transparency of 550 nm light from 85% to 83% to 80%. The respective resistivities were 1141 Ω/sq, 378 Ω/sq and 110 Ω/sq with an inverse exponential relationship between transparency and resistivity. Preferential deposition of MWCNT composites was demonstrated by low coverage on glass substrates and dense coverage on PET substrates. The roughness (Ra) of the MWCNT composites over PET was 20.40 nm as compared to 0.70 nm for indium tin oxide (ITO) depositions over glass.

The structure and optical properties of regio-regular poly(3-hexylthiophene) and carboxylic multi-walled carbon nanotubes composite films

The introduction of small amounts of carboxylic multi-walled carbon nanotubes into regio-regular poly(3-hexylthiophene) (P3HT) can vary the structure and optical properties of the polymer. The microstructure of the composite film was analysed by various techniques including x-ray diffraction, ultraviolet–visible optical absorption, Raman spectroscopy, and Fourier-transform infrared spectroscopy. It is shown that the presence of carbon nanotubes can improve the crystallinity and increase the conjugation length of P3HT in the films. Furthermore, an obvious photoluminescence quenching is observed in the P3HT/CNTs composite films, suggesting the possibility of photoinduced electron transfer between P3HT and carbon nanotubes due to the π–π interaction of these two components. These results are important for applications in bulk heterojunction solar cells and organic photo-detectors.

Research on highly sensitive humidity sensor based on Tr-MWCNT/HEC composite films

Abstract

Tunable Optical Properties of Carbon Nanotube Composite Thin Films

Novel transparent composite thin film electrodes with embedded multi-walled carbon nanotubes (MWCNTs) were fabricated in this study. Their optical properties were explored for applications as cathodes in optoelectronic devices, such as solar cells. The optical properties of the MWCNTs composite thin film were measured in the UV-Vis and IR regions. The films fabricated had tunable transparency from 85% to 80% at 550nm. In the IR region the absorption maxima were at 1151nm, 1203nm, 1223nm, and 1630nm. The band-gap of the films was 3.82 and complementary to the band-gaps of common conjugated polymers for organic solar cells.

The Investigation of Quartz Crystal Microbalance (QCM) Formaldehyde Sensors Based on PEI-MWCNTs Composites

The detection of formaldehyde is very necessary and important in both industrial and residential environments. In this paper, a novel quartz crystal microbalances (QCM) formaldehyde gas sensor has been successful fabricated based on Polyethylenimine (PEI)-multi-walled carbon nanotubes (MWCNTs) composite films by the spraying process. The morphology of films was analyzed by scanning electron microscope (SEM), and formaldehyde-sensing properties of sensors were investigated. The results showed that the prepared QCM gas sensor exhibited good response and recovery behaviors towards formaldehyde gas in the concentration range of 0-10 ppm at room temperature, which also has the superior repeatability and selectivity. Moreover, the gas-sensing mechanism of sensors was studied.

Photovoltaic performance of multi-wall carbon nanotube/PEDOT:PSS composite on the counter electrode of a dye-sensitized solar cell

A composite of poly(3,4-ethylendioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and multi-walled carbon nanotubes (MWCNTs) was cyclovoltametrically electropolymerized on a fluorine-doped tin oxide (FTO) substrate and used as a counter electrode for a dye-sensitized solar cell. The PEDOT:PSS–MWCNT composite film was investigated using scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The CV diagrams showed that the PEDOT:PSS–MWCNT composite film has better electro-catalytic activity for the I−/I3− redox reaction than the conventional platinized FTO. The best energy conversion efficiency was observed in EIS data with an MWCNT content of 0.002 wt %.

Structure, electrical and mechanical properties of polyamide 66/acid-treated MWCNT composite films prepared by solution mixing in the presence of nonionic surfactant

Two different sets of polyamide 66(PA66)-based composite films containing 2.0-10.0 wt% acid-treated multiwalled carbon nanotubes (MWCNT) were manufactured by solution mixing and casting method in the presence or absence of a nonionic surfactant. For the improved dispersion and interfacial interaction of MWCNTs in the PA66 matrix, carboxylic acid-functionalized MWCNTs were prepared by the acid-treatment of pristine MWCNTs. The uniform dispersion of the acidtreated MWCNTs in the PA66 matrix was confirmed from FE-SEM images of the fractured composite film surfaces. DSC thermograms supported that the acid-treated MWCNTs served as nucleating agents for the melt-crystallization of PA66 in both composite films prepared with/without the addition of the surfactant. The electrical and tensile mechanical properties of the composite films prepared with the surfactant were ~20 % higher than those of the composite films manufactured without the surfactant. For both composite films, sheet resistivity and tensile mechanical properties were found to be highly decreased and increased, respectively, with the increment of the acid-treated MWCNT content.

Tunable Carbon Nanotube Mesh Fabricated Via Surfactant Assisted Direct Deposition for High Performance Transparent Electrodes

This study involved the deposition of multi-walled carbon nanotubes (MWCNTs) onto plastic, polyethylene terephalate (PET), substrates. The MWCNTs were suspended in an aqueous solution via the assistance of an ionic surfactant, sodium dodecyl sulfate (SDS). The SDS/MWCNT complexes in solution were attracted to the PET substrate because of electrostatic forces that were demonstrated by contrasting poor coverage on glass substrates. The solutions were deposited onto the PET films and allowed to interact for different amounts of time resulting in films that had decreasing resistivity and transparency because of increasing thicknesses.The ratio of SDS to MWCNT to solvent, water in this case, was from an optimized MWCNT colloid study.1 The ratio used was 10:1:1000 respectively by weight. The excess surfactant was removed at different times using the spin coating technique. Films were then rinsed in water to remove excess surfactant caught in-between the nanotubes in the mesh and then dried in an oven.The best thin film had an average resistivity of 110 Ω/sq at 81% transmittance at 550 nm and a thickness of ± 2 um. Their performance is similar to indium tin oxide thin films as cathodes. The MWCNT and SDS composite thin films will be tested in optoelectronic applications such as solar cells and liquid crystal displays.References 1 Rastogi, R.; Kaushal, R.; Tripathi, S.; Sharma, A.; Kaur, I.; Bharadwaj, L. Comparative study of carbon nanotube dispersion using surfactants. 2008, J. Colloid Interface Sci. 328, 421-428. 2 Jo, J.; Jung, J.; Lee, J.; Jo, W. Fabrication of Highly Conductive and Transparent Thin Films from Single Walled Carbon Nanotubes Using a New Non-ionic Surfactant via Spin. 2010, ACS Nano. 4 (9), 5382-5388.

Enhanced field emission from cerium hexaboride coated multiwalled carbon nanotube composite films: A potential material for next generation electron sources

Intensified field emission (FE) current from temporally stable cerium hexaboride (CeB6) coated carbon nanotubes (CNTs) on Si substrate is reported aiming to propose the new composite material as a potential candidate for future generation electron sources. The film was synthesized by a combination of chemical and physical deposition processes. A remarkable increase in maximum current density, field enhancement factor, and a reduction in turn-on field and threshold field with comparable temporal current stability are observed in CeB6-coated CNT film when compared to pristine CeB6 film. The elemental composition and surface morphology of the films, as examined by scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray measurements, show decoration of CeB6 nanoparticles on top and walls of CNTs. Chemical functionalization of CNTs by the incorporation of CeB6 nanoparticles is evident by a remarkable increase in intensity of the 2D band in Raman spectrum of coated films as compared to pristine CeB6 films. The enhanced FE properties of the CeB6 coated CNT films are correlated to the microstructure of the films.

Electropolymerized Diphenylamine on Functionalized Multiwalled Carbon Nanotube Composite Film and Its Application to Develop a Multifunctional Biosensor

AbstractDiphenylamine (DPA) monomers have been electropolymerized on the amino‐functionalized multiwalled carbon nanotube (AFCNT) composite film modified glassy carbon electrode (GCE) by cyclic voltammetry (CV). The surface morphology of PDPA‐AFCNT was studied using field‐emission scanning electron microscopy (FE‐SEM). The interfacial electron transfer phenomenon at the modified electrode was studied using electrochemical impedance spectroscopy (EIS). The PDPA‐AFCNT/GCE represented a multifunctional sensor and showed good electrocatalytic behavior towards the oxidation of catechol and the reduction of hydrogen peroxide. Rotating‐disk electrode technique was applied to detect catechol with a sensitivity of 1360 µA mM−1 cm−2 and a detection limit of 0.01 mM. Amperometric determination of hydrogen peroxide at the PDPA‐AFCNT film modified electrode results in a linear range from 10 to 800 µM, a sensitivity of 487.1 µA mM−1 cm−2 and detection limit of 1 µM. These results show that the nano‐composite film modified electrode can be utilized to develop a multifunctional sensor.

Dielectric relaxation in polyvinyl alcohol–polypyrrole–multiwall carbon nanotube composites below room temperature

Polyvinyl alcohol–polypyrrole–multiwall carbon nanotube composite polymer films have been synthesized by a chemical oxidative polymerization technique. Dielectric properties have been measured in the frequency range from 20 Hz to 1 MHz and in the temperature range 77 ⩽ T ⩽ 300 K. Electric modulus vector analysis gives the presence of dielectric relaxation peaks for different composites from which the activation energies have been calculated.

Poly(pyrocatechol-3,5-disodiumsulfonate)/Multi-Walled Carbon Nanotubes Composite for Simultaneous Determination of Dopamine, Ascorbic Acid and Uric Acid

A novel poly(pyrocatechol-3,5-disodiumsulfonate)/multi-walled carbon nanotubes (PPD/MWCNT) composite film modified glassy carbon electrode (GCE) was fabricated and successfully used to simultaneously determine ascorbic acid (AA), dopamine (DA) and uric acid (UA). Owing to the synergistic effects of PPD and MWCNTs, the electrochemical responses of AA, DA and UA at PPD/MWCNTs/GCE were clearly superior to those at bare GCE. Additionally, the PPD/MWCNTs composite film could reduce the potential overlap of AA, DA and UA so as to favor simultaneous determination of the three substances. Under the optimum conditions, the linear calibration curves of AA, DA and UA were obtained by differential pulse voltammetry in the range of 10-1000, 1-100 and 4-1200 microM, and the detection limits were 5, 0.5 and 0.5 microM (S/N = 3) respectively. The results showed PPD/MWCNTs/GCE possessed good reproducibility and stability, and it could be applied to determine UA in human urine with satisfying recovery by standard addition method.

Detection of hidden drugs with a molecularly imprinted electrochemiluminescence sensor

A new strategy for the fabrication of an electroluminescence sensor was proposed based on the incorporation of electroluminescence (ECL) detection and the molecular imprinting technology (MIT). The sensor fabrication consisted of two steps, the first one was the immobilization of the light emitting material Ru(bpy)32+ on a GC electrode with the well-established Nafion/the multi-wall carbon nanotube (MWCNT) composite film method and the second step involves re-modification of the Ru(bpy)32+/Nafion/MWCNT electrode with a thin film of molecularly imprinted sol–gel polymers with methamphetamine (MA) as the template molecules. The as-prepared sensor exhibited a very high sensitivity and excellent selectivity toward the target molecule MA. A detection limit as low as 4.0 × 10−15 M was achieved for MA with a wide calibration range from 1.0 × 10−10 to 1.0 × 10−14 M. The high sensitivity of the sensor allowed the drugs in a closed container to be detected by their odors.

Electrical, optical and fluorescence percolations in P(VAc-co-BuA)/MWCNT composite films

Effects of multiwall carbon nanotube (MWCNT) addition on the electrical conductivities, optical transparencies and fluorescence emissions of poly(vinyl acetate-co-butyl acrylate) (P(VAc-co-BuA))/MWCNT composite films were studied. Optical transmission, fluorescence emission and two point probe resistivity techniques were used to determine the variations of the optical, fluorescence and electrical properties of the composites, respectively. Transmitted photon intensity (I tr), fluorescence emission intensity (I fl) and surface resistivity (ρ s) of the composite films were monitored as a function of MWCNT mass fraction (M) at room temperature. All these measured quantities of the composites were decreased by increasing the content of MWCNT in the composite. The conductivity and the optical results were attributed to the classical and site percolation theories, respectively. The fluorescence results, however, possessed both the site and classical percolation theories at low and high MWCNT content regions, respectively.

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

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.

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.

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.

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.