Multi-walled Carbon Nanotube Composite Films Research Articles

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.

Simultaneous determination of uric acid, xanthine and hypoxanthine at poly(pyrocatechol violet)/functionalized multi-walled carbon nanotubes composite film modified electrode

A sensitive and selective electrochemical method was developed for simultaneous determination of uric acid (UA), xanthine (XA) and hypoxanthine (HX) based on a poly (pyrocatechol violet)/carboxyl functionalized multi-walled carbon nanotubes composite film modified electrode. The preparation and basic electrochemical performance of the novel composite film modified glassy carbon electrode were investigated in details. The electrochemical behaviors of UA, XA and HX at the modified electrode were studied by cyclic voltammetry. The results showed that this new electrochemical sensor exhibited excellent electrocatalytic activity towards the oxidation of the three analytes. The mechanism of catalysis was discussed. The anodic peaks of the three species were well defined with lowered oxidation potential and enhanced oxidation peak currents, so the modified electrode was used for simultaneous voltammetric measurement of UA, XA and HX by differential pulse voltammetry. Under the optimum conditions, the detection limits were 0.16 μmol L −1 for UA, 0.05 μmol L −1 for XA and 0.20 μmol L −1 for HX, respectively (S/N of 3). The proposed method has been successfully applied to simultaneous determination of UA, XA and HX in human serum samples.

Temperature dependence of oxygen diffusion into polymer/carbon nanotube composite films

This study examines the transport properties of polystyrene (PS)/multiwalled carbon nanotube (MWNT) composite films taking into consideration both MWNT composition and temperature, via fluorescence technique. Three different (3, 15, and 40 wt%) MWNT content films were prepared from PS/MWNT mixtures by annealing them at 170°C, above the glass transition temperature of PS for 10 min. The diffusivity of the PS/MWNT composite was determined by performing oxygen (O2) diffusion measurements within a temperature range of 24 to 70°C for each film and pyrene (P) was used as the fluorescent probe. The diffusion coefficients (D) of oxygen were determined by the fluorescence quenching method assuming Fickian transport. Results indicated that D values are strongly dependent on both temperature and the MWNT content in the film and it was also observed that D coefficients obey Arrhenius behavior, from which diffusion energies were produced and increased along with increases of MWNT content. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers

Electrochemical immobilization of ascorbate oxidase in poly(3,4‐ethylenedioxythiophene)/multiwalled carbon nanotubes composite films

AbstractImmobilization of ascorbate oxidase (AO) in poly(3,4‐ethylenedioxythiophene) (PEDOT)/multiwalled carbon nanotubes (MWCNTs) composite films was achieved by one‐step electrochemical polymerization. The PEDOT/MWCNTs/AO modified electrode was fabricated by the entrapment of enzyme in conducting matrices during electrochemical polymerization. The PEDOT/MWCNTs modified electrodes were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The experimental results showed that the composite films exhibited better mechanical integrity, electrochemical activity, higher electronic and ionic conductivity, and larger redox capacitance compared with pure PEDOT films, which would be beneficial to the fabrication of PEDOT/MWCNTs/AO electrochemical biosensors. The scanning electron microscopy studies revealed that MWCNTs served as backbone for 3,4‐ethylenedioxythiophene (EDOT) electropolymerization. Furthermore, the resulting enzyme electrode could be used to determine L‐ascorbic acid successfully, which demonstrated the good bioelectrochemical catalytic activity of the immobilized AO. The results indicated that the PEDOT/MWCNTs composite are a good candidate material for the immobilization of AO in the fabrication of enzyme‐based biosensor. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

An Amperometric Biosensor Based on Ascorbate Oxidase Immobilized in Poly(3,4-ethylenedioxythiophene)/Multi-Walled Carbon Nanotubes Composite Films for the Determination of l-Ascorbic Acid

An amperometric L-ascorbic acid (AA) biosensor fabricated by immobilizing ascorbate oxidase (AO) in poly(3,4-ethylenedioxythiophene) (PEDOT) and multi-walled carbon nanotubes (MWCNTs) composite films was reported for the first time. The entrapment of AO in PEDOT/MWCNTs composite films was performed during an electrochemical polymerization process. The influence of various experimental conditions was examined for determining the optimum analytical performance. The response of the biosensor towards AA under the optimized conditions is linear from 0.05 to 20 mM with a detection limit of 15 µM (S/N = 3). The biosensor shows a response time of 20 s and a sensitivity of 23.95 mA M(-1) cm(-2). The apparent Michaelis-Menten constant (K(m)) and apparent activation energy (E(a)) are 19.5 mM and 21 kJ mol(-1), respectively. Moreover, the biosensor exhibits good anti-interferent ability, good reproducibility and remarkable storage stability.

Activation behavior and dielectric relaxation in polyvinyl alcohol and multiwall carbon nanotube composite films

The dc and ac electrical transport property of Polyvinyl Alcohol-Multiwall Carbon Nanotubes (PVA-MWNT) composites has been investigated within a temperature range 77 ≤ T ≤ 300 K and in the frequency range 20Hz–1MHz. The temperature variation of dc conductivity gives the presence of two different activation energies. The dielectric properties of the samples have been explained in terms of electric modulus vector.The dielectric relaxation has been explained in terms of interfacial polarization occurring in between the insulating PVA matrix and MWNT conductive filler. The variation of the relaxation time with temperature also indicates the presence of two different activation energies.

Characterization of Poly(brilliant cresyl blue)-Multiwall Carbon Nanotube Composite Film and Its Application in Electrocatalysis of Vitamin B9 Reduction

Electrochemically active composite film which contains multi-walled carbon nanotubes (MWCNTs) incorporated with poly(brilliant cresyl blue) (PBCB) has been prepared on glassy carbon electrode (GCE) and indium tin oxide (ITO) electrode by potentiodynamic method. The presence of MWCNTs in the composite film (MWCNTs-PBCB) enhances the surface coverage concentration (Γ) of PBCB by 0.25 nmol cm−2 μg−1. The surface morphology of various films deposited on ITO has been studied using scanning electron microscopy and atomic force microscopy, which reveals that MWCNTs incorporated with PBCB. The MWCNTs-PBCB composite film exhibits promising enhanced electrocatalytic activity towards the biochemical compound vitamin B9 (folic acid). The electrocatalytic response of folic acid at PBCB, MWCNTs and MWCNTs-PBCB composite films have been studied using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The sensitivity of MWCNTs-PBCB film towards folic acid (177 μA mM−1 cm−2) is higher than the values obtained for PBCB (0.75 μA mM−1 cm−2) and MWCNT films (148 μA mM−1 cm−2). Similarly, the limit of detection of folic acid at MWCNTs-PBCB film (76 μM) is lower than the other two films. Further, the DPV and selectivity studies reveal that the MWCNTs-PBCB film is efficient for folic acid determination in real sample.

Simultaneous Determination of 3,4-Dihydroxyphenylacetic Acid, Uric Acid and Ascorbic Acid by Poly(L-Arginine)/Multi-Walled Carbon Nanotubes Composite Film

The poly(L-Arginine)(PArg)-multiwalled carbon nanotubes (MWCNTs) composite film was used to modify glassy carbon electrode (GCE) to fabricate PArg/MWCNTs/GCE through electropolymerization of L-Arginine on MWCNTs/GCE. The PArg/MWCNTs/GCE exhibited high electro-catalytic activities towards the oxidation of 3,4-dihydroxyphenylacetic acid (DOPAC), uric acid (UA), and ascorbic acid (AA), and could be sensitively used for simultaneous determination of DOPAC, AA, and UA in pH 7.4 phosphate-buffered solution (PBS).The linear ranges were 7 microM to 2.7 mM for DOPAC, 3 microM to 1.2 mM for UA, and 70 microM to 1.4 mM for AA. The detection limits were 1.3 microM for DOPAC, 0.7 microM for UA and 20 microM for AA.

Electrochemical immunosensor for casein based on gold nanoparticles and poly( l-Arginine)/multi-walled carbon nanotubes composite film functionalized interface

In this paper, a novel electrochemical immunosensor for the determination of casein based on gold nanoparticles and poly( l-Arginine)/multi-walled carbon nanotubes (P- l-Arg/MWCNTs) composite film was proposed. The P- l-Arg/MWCNTs composite film was used to modify glassy carbon electrode (GCE) to fabricate P- l-Arg/MWCNTs/GCE through electropolymerization of l-Arginine on MWCNTs/GCE. Gold nanoparticles were adsorbed on the modified electrode to immobilize the casein antibody and to construct the immunosensor. The stepwise assembly process of the immunosensor was characterized by cyclic voltammetry and differential pulse voltammetry. Results demonstrated that the peak currents of [Fe(CN) 6] 3−/4− redox pair decreased due to the formation of antibody–antigen complex on the modified electrode. The optimization of the adsorption time of gold nanoparticles, the pH of supporting electrolyte and the incubation time were investigated in details. Under optimal conditions, the peak currents obtained by DPV decreased linearly with the increasing casein concentrations in the range from 1 × 10 −7 to 1 × 10 −5 g mL −1 with a linear coefficiency of 0.993. This electrochemical immunoassay has a low detection limit of 5 × 10 −8 g mL −1 and was successfully applied to the determination of casein in cheese samples.

Electromagnetic interference shielding of cellulose triacetate/multiwalled carbon nanotube composite films

AbstractCellulose triacetate (CTA) and multiwalled carbon nanotube (MWNT) composite films were prepared by dispersing different weight percentages of MWNTs into a CTA solution. These composite blends were characterized by UV–vis spectroscopy (UV), and their surface mophology, thermal stability, and amended crystallinity were determined by atomic force microscopy (AFM), thermogravimetric analysis (TGA), and X‐ray diffraction (XRD), respectively. Measurements of the complex impedance of the composite samples were made in the form of films. Sheets prepared from conventional techniques were used to study microwave absorption in the microwave range of 2–12 GHz, and the effects of sample thickness on microwave absorption were investigated. The experimental results show that the electrical conductivity of composites increases with the increase in MWNT loading without a percolation threshold. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

Voltammetric Determination of Vitamin B6 at Glassy Carbon Electrode Modified with Gold Nanoparticles and Multi-Walled Carbon Nanotubes

In this work, the gold nanoparticles (Au NPs)/multi-walled carbon nanotubes (MWCNTs) composite film modified glassy carbon electrode (GCE) was fabricated, and scanning electron microscopy (SEM) was used to investigate the assemble process of the composite film. In pH 7.0 PBS, a oxidation peak of the vitamin B6 (VB6) was only observed at composite film modified electrode. Under the optimized conditions, the current intensity was linear with the concentrations of VB6 in the range of 1.59 to 102.74 μg●mL–1 with a detection limit of 0.53 μg●mL–1 (S/N = 3). The modified electrode had been applied in medication analysis, and obtained good results.

발포용 PU/MWNT 복합필름의 제조와 특성분석

This paper surveys the physical properties of the multiwall carbon nanotube (MWNT) and polyurethane composite film for improvement of mechanical properties and electrical characteristics. The modification of MWNT was carried out by acid treatment with nitric and sulphuric acid mixed solution, and then followed by thermal treatment for enhancing MWNT dispersion with polyurethane. This modified MWNT was mixed with polyurethane by changing the loading content of MWNT and dispersion time under the dimethylformamide solution in the ultrasonic wave apparatus. Various physical characteristics of the modified PU/MWNT films were measured and analyzed in terms of the loading content and dispersion time. The maximum absorbance of the PU/MWNT films were observed with the 2wt% loading at dispersion times of 2 and 24 hour, respectively. The minimum electrical volume resistivity of PU/MWNT film was shown at the loading content of 0.5wt% or more irrespective of dispersion treating time. However the optimum condition was assumed to 2wt% loading at dispersion time of 2 hours by assessing the surface profile of the film using video microscope. The breaking stress and strain of the PU/MWNT film decreased with increasing loading content, but no change of physical properties was shown with increasing in dispersion time.

Photopatternable Poly(4-styrene sulfonic acid)-Wrapped MWNT Thin-Film Source/Drain Electrodes for Use in Organic Field-Effect Transistors

We describe the cross-linking of poly(4-styrene-sulfonic acid) (PSS) by exposure to ultraviolet (UV) light (λ = 255 nm) under a vacuum. Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) showed that the photo-crosslinking of PSS resulted from coupling between radicals that were generated in the polymer chains by UV excitation. The photo-cross-linkable characteristics of PSS were employed to fabricate solution-processable, photopatternable, and conductive PSS-wrapped multiwalled carbon nanotube (MWNT) composite thin films by wrapping MWNTs with PSS in water. During photo-cross-linking, the work function of the PSS-wrapped MWNTs decreased from 4.83 to 4.53 eV following cleavage of a significant number of sulfonic acid groups. Despite the decreased work function of the PSS-wrapped MWNTs, the photopatterned PSS-wrapped MWNTs produced good source/drain electrodes for OFETs, yielding a mobility (0.134 ± 0.056 cm²/(V s)) for the TIPS-PEN field-effect transistors fabricated using PSS-wrapped MWNTs as source/drain electrodes that was higher than the mobility of gold-based transistors (0.011 ± 0.004 cm²/(V s)).

Electrochemistry and voltammetric determination of furazolidone with a multi-walled nanotube composite film-glassy carbon electrode

This study describes the electrochemical properties of furazolidone (Fu) at a glassy carbon electrode (GCE) modified with a multi-walled carbon nanotube (MWCNT) composite film. Cyclic voltammetry and chronoamperometry techniques were used for diagnostic purposes. The electrode (MWCNT-film-modified GCE) exhibited excellent electrocatalytic behavior for the reduction of Fu as evidenced by the enhancement of the 4e-reduction peak current and the shift in the reduction potential to more positive potential (by 50 mV) in comparison with a bare GCE. The formal potential, E0′, of Fu is pH dependent with a slope of 54.4 mV per unit of pH, close to the anticipated Nernestian value of −59 mV for a four-electron and four-proton processes. The transfer coefficient (α), standard rate constant of the surface reaction (ks), diffusion coefficient (D), and surface concentration (Γ) for the MWCNT-film-modified GCE were calculated. On the other hand, Fu can be accumulated effectively on the MWCNT-film-modified GCE. Under the selected experimental conditions, i.e., solution pH 6, accumulation time 10 min, and accumulation potential −0.30 V, the peak current shows a dynamic linear range 3–800 μM with detection limit 2.30 μM. The method was successfully applied to analyze pharmaceutical formulations. The method used in this study was further applied for the determination of Fu.

Vitamin B 12 incorporated with multiwalled carbon nanotube composite film for the determination of hydrazine

Electrochemically active composite film containing multiwalled carbon nanotubes (MWCNTs) and vitamin B 12 was synthesized on glassy carbon, gold, and indium tin oxide electrodes by the potentiodynamic method. The presence of MWCNTs in the composite film (MWCNT–B 12) modified electrode mediates vitamin B 12’s redox reaction, whereas vitamin B 12’s redox reaction does not occur at bare electrode. The electrochemical impedance spectroscopy studies reveal that MWCNTs present in MWCNT–B 12 film enhance electron shuttling between the reactant and electrode surface. The surface morphology of bare electrode, MWCNT film. and MWCNT–B 12 composite film was studied using atomic force microscopy, which reveals vitamin B 12 incorporated with MWCNTs. The MWCNT–B 12 composite film exhibits promising enhanced electrocatalysis toward hydrazine. The electrocatalysis response of hydrazine at MWCNT film and MWCNT–B 12 composite film was measured using cyclic voltammetry and amperometric current–time ( i– t) curve techniques. The linear concentration range of hydrazine obtained at MWCNT–B 12 composite film using the i– t curve technique is 2.0 μM–1.95 mM. Similarly, the sensitivity of MWCNT–B 12 composite film for hydrazine determination using the i– t curve technique is 1.32 mA mM −1 cm −2, and the hydrazine’s limit of detection at MWCNT–B 12 composite film is 0.7 μM.

A Novel Electrochemical Sensor for Probing Doxepin Created on a Glassy Carbon Electrode Modified with Poly(4-Amino- benzoic Acid)/Multi-Walled Carbon Nanotubes Composite Film

A novel electrochemical sensor for sensitive detection of doxepin was prepared, which was based on a glassy carbon electrode modified with poly(4-aminobenzoic acid)/multi-walled carbon nanotubes composite film [poly(4-ABA)/MWNTs/GCE]. The sensor was characterized by scanning electron microscopy and electrochemical methods. It was observed that poly(4-ABA)/MWNTs/GCE showed excellent preconcentration function and electrocatalytic activities towards doxepin. Under the selected conditions, the anodic peak current was linear to the logarithm of doxepin concentration in the range from 1.0 × 10−9 to 1.0 × 10−6 M, and the detection limit obtained was 1.0 × 10−10 M. The poly(4-ABA)/MWNTs/GCE was successfully applied in the measurement of doxepin in commercial pharmaceutical formulations, and the analytical accuracy was confirmed by comparison with a conventional ultraviolet spectrophotometry assay.

Fabrication of poly(orthanilic acid)–multiwalled carbon nanotubes composite film-modified glassy carbon electrode and its use for the simultaneous determination of uric acid and dopamine in the presence of ascorbic acid

A multiwalled carbon nanotubes (MWNT) modified glassy carbon electrode (GCE) coated with poly(orthanilic acid) (PABS) film (PABS–MWNT/GCE) has been fabricated and used for simultaneous determination of dopamine (DA) and uric acid (UA) in the presence of ascorbic acid (AA) by differential pulse voltammetry (DPV). Scanning electron microscopy, Fourier transform infrared spectra, and electrochemical techniques have been used to characterize the surface morphology of the PABS–MWNT composite film and the polymerization of ABS on electrode surface. In comparison with the bare GCE and the MWNT-modified GCE, the PABS–MWNT composite film-modified GCE, which combines the advantages of MWNT and the self-doped PABS, exhibits good selectivity and sensitivity for the simultaneous and selective determination of UA and DA in the presence of AA. Due to the different electrochemical responses of AA, DA, and UA, PABS–MWNT/GCE can resolve the overlapped oxidation peak of DA and UA into two well-defined voltammetric peaks with enhanced current responses using both cyclic voltammetry (CV) and DPV. The peak potential separations between DA and UA are 170 mV using CV and 160 mV using DPV, respectively, which are large enough for the selective and simultaneous determination of these species. In the presence of 0.5 mM AA, the DPV peak currents are linearly dependent on the concentration of UA and DA in the range of 6–55 and 9–48 μM with correlation coefficients of 0.997 and 0.993, respectively. The detection limits (S/N = 3) for detecting UA and DA are 0.44 and 0.21 μM, respectively. The PABS–MWNT/GCE shows good reproducibility and stability and has been used for the simultaneous determination of DA and UA in the presence of AA in samples with satisfactory results.

Electrochemical behavior of rutin on a multi-walled carbon nanotube and ionic liquid composite film modified electrode

In this paper, the electrochemical behaviors of rutin at the MWNTs-IL-Gel/glassy carbon electrode (GCE) were investigated. Good electrocatalysis behavior towards the oxidation of rutin with enhancement of the redox peak current and decrease of the peak-to-peak separation was demonstrated. The electrochemical parameters of rutin were calculated giving values of the charge-transfer coefficient ( α) and the electrode reaction standard rate constant ( k s) as 0.47 and 0.2 s −1, respectively. In addition, the MWNTs-IL-Gel/GCE was characterized by different methods including electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), clay film thickness, and UV–vis spectra. The oxidation peak currents of rutin in such modified electrode increased linearly with the concentration of rutin in the range from 7.2 × 10 −8 to 6.0 × 10 −6 mol L −1 with a detection limit of 2.0 × 10 −8 mol L −1. These results suggest that the proposed electrode can be used for sensitive, simple and rapid determination of rutin.

Enhanced photoelectrochemistry and interactions in cadmium selenide–functionalized multiwalled carbon nanotube composite films

Cadmium selenide–functionalized multiwalled carbon nanotube (CdSe–f-MWCNT) composite films have been synthesized by the percolation of a f-MWCNT dispersion through the macropores of electrodeposited CdSe thin films during electrophoretic deposition. Evidence for efficient charge transfer from CdSe to f-MWCNTs was obtained by photoluminescence quenching and proof for strong interactions was provided by X-ray photoelectron spectroscopy analyses, which revealed a significant decrease in the reduced Se 2− content and evolution of new signals due to oxidized Se, and high resolution transmission electron microscopy and atomic force microscopy images of CdSe decorated f-MWCNTs in the composite film. Sputter depth profiling of the composite confirmed a homogeneous mixing of nanoparticulate CdSe and f-MWCNTs. A quasi solid-state photoelectrochemical cell fabricated by coupling the composite film with an ionic liquid based gel polymer electrolyte containing the I 3/I − redox pair not only showed larger photocurrents, photovoltage and incident photon to current conversion efficiency as compared to the analogous CdSe cell but also showed a remarkably enhanced stability to photoerosion. The ability of f-MWCNTs to mediate fast charge transfer and retard charge recombination rate in the composite was also evident from electrochemical impedance spectroscopy (EIS) results. Cell degradation upon exposure was also reflected in the altered EIS parameters such as increased charge transfer resistance and the reduced ease of charge transport through the composite.