Multi-walled Carbon Nanotube Composite Films Research Articles

Carbon electrode modified with ionic liquid and multi-walled carbon nanotubes for voltammetric sensing of adenine

A voltammetric sensor was fabricated by applying a Nafion and multi-walled carbon nanotubes (MWCNTs) composite film on the surface of a carbon ionic liquid electrode (CILE), which was prepared by mixing 1-butyl-3-methylimidazolium hexafluorophosphate with graphite powder. The electrochemical behavior of adenine on the Nafion-MWCNTs/CILE was investigated in pH 5.5 buffer solution. Adenine showed an irreversible adsorption-controlled oxidation reaction with enhanced electrochemical response, which was due to the presence of high conductive MWCNTs on the CILE surface. The electrochemical parameters of adenine electro-oxidation were determined, and the experimental conditions were optimized. Under the optimal conditions, the oxidation peak current was linear to the adenine concentration over the range of 1.0 × 10−7 to 7.0 × 10−5 mol L−1 with a detection limit of 3.3 × 10−8 mol L−1 (signal/noise = 3). The electrode showed good stability and selectivity, and was further applied to milk powder samples with satisfactory results.

Effects of thermal imidization on mechanical properties of poly(amide‐co‐imide)/multiwalled carbon nanotube composite films

AbstractIn this study, experimental and numerical studies were performed to investigate the relationship among the functionalization method, weight fraction of MWCNTs, thermal imidization cycle, and mechanical properties of various PAI/MWCNT composite films. Poly(amide‐co‐imide)/multiwalled carbon nanotube composite films were prepared by solution mixing and film casting. The effects of chemical functionalization and weight fraction of multiwalled carbon nanotubes on thermal imidization and mechanical properties were investigated through experimental and numerical studies. The time needed to achieve sufficient thermal imidization was reduced with increasing multiwalled carbon nanotube content when compared with that of a pure poly(amide‐co‐imide) film because multiwalled carbon nanotubes have a higher thermal conductivity than pure poly(amide‐co‐imide) resin. Mechanical properties of pure poly(amide‐co‐imide) and poly(amide‐co‐imide)/multiwalled carbon nanotube composite films were increased with increasing imidization time and were improved significantly in the case of the composite film filled with hydrogen peroxide treated multiwalled carbon nanotubes. Both the tensile strength and strain to failure of the multiwalled carbon nanotube filled poly(amide‐co‐imide) film were increased substantially because multiwalled carbon nanotube dispersion was improved and covalent bonding was formed between multiwalled carbon nanotubes and poly(amide‐co‐imide) molecules. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Surface Modification of Carbon Nanotube by Poly(ethylene glycol) for the Preparation of Poly(vinyl alcohol) Nanocomposite

Herein, PEGylated multi-walled carbon nanotube (MWNT) was prepared for the successive fabrication of poly(vinyl alcohol) PVA/MWNT nanocomposite film by solution casting. The surface modified MWNT showed a good colloidal stability in a polar solvent, i.e., water. Also, the PEGylated MWNT had an improved dispersion stability in aqueous PVA solution. The mixture of PEGylated MWNT and PVA dissolved in water was film casted and the dispersion uniformity and corresponding improvement of electrical conductivity were investigated. The electrical conductivity of PVA/modified MWNT composite film was three-fold higher than that of PVA/pristine MWNT composite film due to the much improved distribution uniformity of modified MWNT in PVA matrix.

Acid yellow 9 as a dispersing agent for carbon nanotubes: Preparation of redox polymer–carbon nanotube composite film and its sensing application towards ascorbic acid and dopamine

In this study, we show that acid yellow 9 (4-amino-1-1′-azobenzene-3,4′-disulfonicacid, AY) is a good stabilizing agent for multi-walled carbon nanotubes (MWCNTs). MWCNTs dispersed in AY solution was remained stable about three months and even remained stable after centrifugation at 10,000 rpm for 30 min. Using MWCNTs/AY dispersion, thin-films were prepared on indium tin oxide coated glass electrode and glassy carbon electrodes. Further, dried films of MWCNTs/AY were subjected to electropolymerization in 0.1 M H 2SO 4 solution. Adsorbed AY molecules on MWCNTs get polymerized and they yield a polymer–MWCNTs nanocomposite film on electrode surface which is found to be electrochemically active in wide pH range (1–11). Characterization studies were performed using cyclic voltammetry and SEM. These studies are supported that hybrid material PAY/MWCNTs was obtained. Moreover, newly synthesized PAY–MWCNTs composite film showed excellent electrocatalytic activity towards oxidation of dopamine (DA) and ascorbic acid (AA) with high sensitivity in physiological pH. Linear sweep voltammetry was employed to the determination of DA in the presence of AA in the range of 2 × 10 −7 to 1.4 × 10 −6 M. Amperometry was employed to determination of AA at 0.0 V in the range from 1 × 10 −6 to 5.6 × 10 −5 M, and DA, uric acid are not interfered on the steady-state current of AA. In addition, real samples such as dopamine injection and AA spiked into human urine were analyzed using PAY/MWCNTs composite modified electrode and satisfactory results were obtained.

Cu–MWCNT Composite Films Fabricated by Electrodeposition

Copper–multiwalled carbon nanotube (MWCNT) composite plating using a sulfuric base bath was studied. A dispersing agent was used to disperse the MWCNTs into the plating bath. The effects of electrodeposition conditions on the surface morphology, microstructure, and MWCNT content in the composite films were examined. The internal stress, hardness, electrical conductivity, and thermal conductivity of the composite films were also investigated. The current density remarkably affected the surface morphologies of the films, and a relatively smooth surface was obtained at lower current densities. The bath temperature affected the microstructure of the composite films; a compact microstructure was formed at a lower temperature. The MWCNT content in the composite film increased with increasing MWCNT concentration in the plating bath, reaching a maximum value of 0.55 mass %. However, MWCNTs in the composite films tended to agglomerate for high MWCNT concentrations in the plating bath. An internal tensile stress was induced in the films. The hardness of the films was around 150 HV, and the electrical resistivity was approximately . The thermal conductivity of the Cu–0.42 mass % MWCNT composite film was .

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.

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.

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.

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.

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.

A novel hydrogen peroxide sensor based on multiwalled carbon nanotubes/poly(pyrocatechol violet)‐modified glassy carbon electrode

AbstractIn this work, a new hydrogen peroxide (H2O2) sensor was reported based on electropolymerizing pyrocatechol violet (PCV) on a glassy carbon electrode modified with multiwalled carbon nanotubes (MWCNTs). The modified electrode was characterized by cyclic voltammetry (CV) and scanning electron micrography. The result of electrochemical experiments showed a favorable catalytic activity toward the reduction of H2O2 at −0.4 V with a linear response range from 2.0 μM to 2.4 mM and a detection limit of 0.7 μM (at a S/N = 3). The well catalytic activity of proposed sensor could be attributed to the poly‐PCV/MWCNTs composite film on the electrocatalytic reduction of H2O2. In addition, the sensor also exhibited a high sensitivity, good stability, and reproducibility. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Investigation of liquid sensing mechanism of poly(lactic acid)/multi-walled carbonnanotube composite films

The liquid sensing mechanism of melt-processed poly(lactic acid) (PLA)/multi-walledcarbon nanotube (MWNT) composite films was investigated for the influence of MWNTloading, solubility parameters of solvents used, solvent transport behaviours, resultantelectrical resistance changes, as well as crystallization of the PLA matrix. Thediffusion, sorption and permeation coefficients of neat PLA and the composites wereestimated, indicating that MWNT network structures block solvent moleculesfrom penetrating into the polymer matrix. Solvent-induced crystallization of thepolymer matrix was observed. Isothermally crystallized composites showed reducedresistances, a significant decrease of sorbed solvent content and a reduction of theresulting resistance changes on the solvent contact. In the context with sensingresults on MWNT mats, it was proposed that the liquid sensing mechanism ofPLA/MWNT composites consists of the overall electrical resistance changes causedby the structural variation of the conductive MWNT network in the polymermatrix and additional interactions between the MWNT and solvent molecules.

High-Sensitive Glutamate Biosensor Based on NADH at Lauth’s Violet/Multiwalled Carbon Nanotubes Composite Film on Gold Substrates

A highly sensitive amperometric L-glutamate biosensor based on the electrocatalytic oxidation of reduced nicotinamide adenine dinucleotide has been developed on Lauth's Violet (known as thionine)/multiwalled carbon nanotubes (Th-MWCNTs) composite film, which is used as a mediator and an enzyme immobilization matrix. The glutamate biosensor, which is fabricated by immobilizing glutamate dehydrogenase (GLDH) on the surface of Th-MWCNTs, displayed a precipitous response (ca. 3 s), a low detection limit (15.9 nM), a wide linear dynamic range (0.1 to 500 microM), and high sensitivity of 281.6 microAmM(-1) cm(-2), higher biological affinity, as well as good stability and repeatability. Interferences from other biological compounds were also studied for the fabricated sensor. The Th-MWCNTs system exemplifies a simple and efficient approach to the assimilation of GLDH and electrodes, which can provide analytical access to a large group of enzymes for wide range of bioelectrochemical applications in health care fields.

Spray deposited fluoropolymer/multi-walled carbon nanotube composite films with high dielectric permittivity at low percolation threshold

High performance perfluoro alkoxy (PFA) and chemical vapor deposition-grown multi-walled carbon nanotube (MWCNT) composite films with thicknesses of 30 μm were prepared using a scalable spray deposition technique. A homogeneous distribution of MWCNTs within the PFA matrix was confirmed by electron and optical microscopy. Dielectric and AC conductivity measurements showed a significant enhancement of dielectric permittivity for PFA/MWCNT films at low frequencies, and a very weak dependence of dielectric permittivity on temperature in the range 25–230 °C. Very low percolation threshold volume fractions of ca. 0.0043 and 0.0017 were attained for MWCNTs with two different aspect ratios, which have been explained by an inherent feature of spray route, a microcapacitor model and percolation theory. The combination of PFA/MWCNT composites and the spray deposition route provides a promising approach for the fabrication of industrial scale composite films with well-controlled dielectric properties for micro-electronic and high temperature applications.

Carbonization of oriented polyacrylonitrile and multiwalled carbon nanotube composite films

AbstractComposite films of polyacrylonitrile (PAN)/multiwalled carbon nanotubes (MWNTs) were fabricated by gelation/crystallization from solution. The composite films were elongated twofold and heat‐treated at 2800 °C to produce oriented carbon films. The orientation and morphology of the resultant carbon films were investigated by scanning electron microscopy, wide‐angle X‐ray diffraction and Raman spectrometers. The results indicate that the degree of graphitization of PAN was enhanced by the addition of MWNTs, at the same time, the elongation induced the orientation of MWNTs along elongation direction and the co‐orientation of MWNTs and the molecular chains of the matrix PAN greatly promoted the carbonization of composite precursor. It is suggested that carbon nanotubes acted as nucleation side of graphitic crystal during the carbonization of PAN‐MWNTs composites. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd.

Physical Properties of Thin PVDF/MWNT (Multi-Walled Carbon Nanotube) Composite Films by Melt Blending

Poly(vinylidene fluoride)(PVDF)/Multi-walled carbon nanotube (MWNT) composites were melt blended using internal mixer. The relationships between structures and physical properties of thin PVDF/MWNT composite films were studied. With increasing the content of MWNT, the size of spherulites in PVDF decreased. MWNT was used as a nucleating agent. The incorporation of MWNT produced a polar beta-form crystal structure of PVDF. The permittivities of thin PVDF/MWNT composite films were increased with increasing the MWNT content. The percolation level in electrical conductivity occurred between 2 and 2.5 wt%. The critical conductivity saturation point for the electrical conductivity in PVDF was confirmed. Similar tendency was also observed in thermal conductivity.

Liquid sensing of melt-processed poly(lactic acid)/multi-walled carbon nanotube composite films

Liquid sensing properties of poly(lactic acid) (PLA)/multi-walled carbon nanotube (MWNT) composites were studied on the basis of the change of electrical properties on solvent contact. The composites were prepared by melt processing using a twin screw extruder. The MWNT loading differed between 0.5 and 2.0 wt%, and an electrical percolation threshold below 0.5 wt% MWNT content was obtained. TEM observations revealed that the nanotubes form a conductive network structure in the PLA matrix, which is the key for liquid sensing. Electrical resistance of the composites was monitored in solvent immersion/drying cycles on samples prepared from thin pressed composite sheets. The resistance reversibly changed upon the cycles with good reproducibility. Lower MWNT loadings resulted in larger resistance changes, indicating that the conductive MWNT network tends to readily disconnect due to the less dense structures as compared to higher loadings. Various solvents (n-hexane, toluene, chloroform, tetrahydrofuran, dichloromethane, ethanol, and water) were successfully detected, showing different degrees of the resistance changes (ca. 4–1.0 × 103 Ω) and the relative resistance changes (ca. 0.003–3.0 × 103). The solubility parameters of the solvents were found to be good indicators to estimate liquid sensing properties of these PLA/MWNT composites for the poor and good solvents.

Preparation and mechanical properties of waterborne polyurethane/carbon nanotube composites

AbstractWaterborne polyurethane (WBPU) and multiwalled carbon nanotubes (CNTs) composite films with 0–4.0 wt% CNTs were prepared by ultrasonic dispersion of carboxylic acid‐functionalized CNTs in WBPU followed by emulsion casting process. The elongations at break of the WBPU/CNTs composites increase with the incorporation of CNTs. The tensile strength and crystallinity of the nanocomposite films with lower CNTs contents (<2 wt%) increase obviously; while the tensile strengths of the composites with more CNTs (≥2 wt%) decrease, in contrast to the pure PU film. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations indicated that the CNTs are uniformly dispersed in the composites incorporated with lower CNTs contents (≤1.5 wt%). However, aggregation of CNTs increased with increasing CNTs content in the WBPU/CNTs composites, causing the macrophase separation. The dispersion state of the CNTs affects the crystallinity of the PU matrix and the phase separation of the composites, which are two key factors to influence the mechanical properties of the WBPU/CNTs composites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers

Functionalized Multiwalled Carbon Nanotubes Through In Situ Electropolymerization of Brilliant Cresyl Blue for Determination of Epinephrine

AbstractIn this work, a polymeric brilliant cresyl blue (BCB) and dihexadecyl phosphate (DHP) dispersed Multi‐walled carbon nanotubes (MWNTs) composite film modified glass carbon electrode (PBCB‐MWNTs‐DHP/GCE) denoted as epinephrine (EP) sensor was prepared by an in‐situ electropolymerization method. The electrochemical response of EP at the sensor is much better. Voltammetric investigations indicated that the improved response of EP at the sensor mainly arose from the enhanced adsorption of EP at PBCB‐MWNTs‐DHP film, perhaps through the hydrogen bonding and π–π interactions between EP and PBCB. The sensor was applied to the determination of EP in injection by a standard addition method and the results were satisfied.