Carbon Nanotube Composite Electrode Research Articles

Enhanced sensitivity for biosensors: Functionalized P1,5-diaminonaphthalene-multiwall carbon nanotube composite film-modified electrode

A homogeneous electroactive poly(1,5-diaminonaphthalene) (P1,5DAN) and multiwalled carbon nanotube (MWNT) composite film-modified electrode was fabricated by cyclic voltammetry and a casting method. The dispersion and morphology of the MWNTs/P1,5DAN composite film were investigated by scanning electron microscopy. The cyclic voltammograms of the electrode modified by the MWNTs/P15DAN composite film strongly depended on the film thickness and pH of the electrolyte solution. Two absolutely isolated oxidation potentials were found as the MWCNTs were immobilized onto the surface of P1,5DAN film in a pH 6.8 buffer solution containing ascorbic acid (AA) and uric acid (UA). Both peak currents linearly increased with increased concentrations. The electrochemical behavior of UA was not interrupted even in the presence of high-concentration AA given that AA had no observable electrochemical changes at the immobilized concentration. The electrocatalytic behavior of H2O2 was also investigated by steady-state amperometry for the immobilization of horseradish peroxidase on the P1,5DAN film. The plot of the response current vs. H2O2 concentration was linear over the wide concentration range of 0.015–5.37mM.

Lithium‐Ion Batteries: A Stretchable Polymer–Carbon Nanotube Composite Electrode for Flexible Lithium‐Ion Batteries: Porosity Engineering by Controlled Phase Separation (Adv. Energy Mater. 8/2012)

Lithium‐Ion Batteries: A Stretchable Polymer–Carbon Nanotube Composite Electrode for Flexible Lithium‐Ion Batteries: Porosity Engineering by Controlled Phase Separation (Adv. Energy Mater. 8/2012)

Factors affecting the performance of supercapacitors assembled with polypyrrole/multi-walled carbon nanotube composite electrodes

In this study, polypyrrole/multi-walled carbon nanotube (PPy/MWCNT) composites were synthesized in water, dichloromethane and n-hexane solvents and the conducting composite materials were tested as symmetric 2-electrode electrochemical capacitors. The synthesis method, electrolyte type, and binder compositions had profound effects on the overall performance of the cells. The microscopic structure of the composites and hydrophilicity of the electrode materials also influenced the capacitor behavior. The cells assembled with the PPy/MWCNT composites had a high specific capacitance (165Fg−1) and excellent cycleability for up to 1000 cycles in 1.0M KCl electrolyte. The composite electrodes showed no capacitance loss due to the increase of internal resistance of the materials and thus, they exhibited ideal supercapacitor characteristics.

Micro‐Supercapacitors Based on Interdigital Electrodes of Reduced Graphene Oxide and Carbon Nanotube Composites with Ultrahigh Power Handling Performance

AbstractA novel method for fabricating micro‐patterned interdigitated electrodes based on reduced graphene oxide (rGO) and carbon nanotube (CNT) composites for ultra‐high power handling micro‐supercapacitor application is reported. The binder‐free microelectrodes were developed by combining electrostatic spray deposition (ESD) and photolithography lift‐off methods. Without typically used thermal or chemical reduction, GO sheets are readily reduced to rGO during the ESD deposition. Electrochemical measurements show that the in‐plane interdigital design of the microelectrodes is effective in increasing accessibility of electrolyte ions in‐between stacked rGO sheets through an electro‐activation process. Addition of CNTs results in reduced restacking of rGO sheets and improved energy and power density. Cyclic voltammetry (CV) measurements show that the specific capacitance of the micro‐supercapacitor based on rGO–CNT composites is 6.1 mF cm−2 at 0.01 V s−1. At a very high scan rate of 50 V s−1, a specific capacitance of 2.8 mF cm−2 (stack capacitance of 3.1 F cm−3) is recorded, which is an unprecedented performance for supercapacitors. The addition of CNT, electrolyte‐accessible and binder‐free microelectrodes, as well as an interdigitated in‐plane design result in a high‐frequency response of the micro‐supercapacitors with resistive‐capacitive time constants as low as 4.8 ms. These characteristics suggest that interdigitated rGO–CNT composite electrodes are promising for on‐chip energy storage application with high power demands.

Silver-functionalized carbon nanofiber composite electrodes for ibuprofen detection

The aim of this study is to prepare and characterize two types of silver-functionalized carbon nanofiber (CNF) composite electrodes, i.e., silver-decorated CNF-epoxy and silver-modified natural zeolite-CNF-epoxy composite electrodes suitable for ibuprofen detection in aqueous solution. Ag carbon nanotube composite electrode exhibited the best electroanalytical parameters through applying preconcentration/differential-pulsed voltammetry scheme.

Reaction of Li and Na with Iron Oxide/ Carbon Nanotube Composite Electrode in Ionic Liquid Electrolyte

not Available.

Copper-decorated carbon nanotubes-based composite electrodes for nonenzymatic detection of glucose

The aim of this study was to prepare three types of multiwall carbon nanotubes (CNT)-based composite electrodes and to modify their surface by copper electrodeposition for nonenzymatic oxidation and determination of glucose from aqueous solution. Copper-decorated multiwall carbon nanotubes composite electrode (Cu/CNT-epoxy) exhibited the highest sensitivity to glucose determination.

Determination of ascorbic acid levels in food samples by using an ionic liquid–carbon nanotube composite electrode

A novel carbon composite electrode consisted of ionic liquid n-octylpyridinum hexafluorophosphate (OPFP) and single-walled carbon nanotube (SWCNT) was fabricated and investigated. This electrode combined the advantages of ionic liquid and SWCNT together with the “bulk” composite electrode. Compared with other composite electrodes using graphite or paraffin oil, the ionic liquid–SWCNT (IL–SWCNT) composite electrode exhibited remarkable increase in the electron transfer rate for electroactive compound and significant decrease in the overpotential for ascorbic acid oxidation reaction. Based on the greatly enhanced electrocatalytic activity for the oxidation of ascorbic acid, a wide linear detection range from 3.0μM to 4.2mM with a low detection limit of 1.0μM was obtained. Furthermore, the IL–SWCNT electrode was applied to determine ascorbic acid levels in real food samples. Experimental results showed that the proposed electrode could be used as an effective and sensitive sensor for direct detection of ascorbic acid.

A Stretchable Polymer–Carbon Nanotube Composite Electrode for Flexible Lithium‐Ion Batteries: Porosity Engineering by Controlled Phase Separation

AbstractFlexible energy‐storage devices have attracted growing attention with the fast development of bendable electronic systems. However, it still remains a challenge to find reliable electrode materials with both high mechanical flexibility/toughness and excellent electron and lithium‐ion conductivity. This paper reports the fabrication and characterization of highly porous, stretchable, and conductive polymer nanocomposites embedded with carbon nanotubes (CNTs) for application in flexible lithium‐ion batteries. The systematic optimization of the porous morphology is performed by controllably inducing the phase separation of polymethylmethacrylate (PMMA) in polydimethylsiloxane (PDMS) and removing PMMA, in order to generate well‐controlled pore networks. It is demonstrated that the porous CNT‐embedded PDMS nanocomposites are capable of good electrochemical performance with mechanical flexibility, suggesting these nanocomposites could be outstanding anode candidates for use in flexible lithium‐ion batteries. The optimization of the pore size and the volume fraction provides higher capacity by nearly seven‐fold compared to a nonporous nanocomposite.

Fabrication of Polyaniline/Carbon Nanotubes Composites Using Carbon Nanotubes Films Obtained by Electrophoretic Deposition

In this study, we report a facile electrochemical method to obtain polyaniline/single-wall carbon nanotubes (PANI/SWCNTs) composite electrodes by combining the electroreduction of diazonium salts and electropolymerization of conductive polymers. In a first step, the SWCNTs are covalently functionalized with diphenyl amine through the electrochemical reduction of the 4-aminodiphenylamine diazonium salt in order to provide anchors for the subsequent polymer electrodepostion. The aniline oxidation remains possible on this grafted layer and PANI can easily be deposited on the diphenyl amine-modified electrodes. The electrochemically deposited PANI/SWCNTs composites exhibit excellent electrochemical charge storage properties making them promising electrode materials for high power supercapacitors.

Polyaniline/polyacrylic acid/multi-walled carbon nanotube modified electrodes for sensing ascorbic acid

A multi-walled carbon nanotube composite electrode incorporating Polyaniline (PANI) and Polyacrylic acid (PAA) is presented by diffusing aniline and PAA into Nafion- MWCNTs membranes supported upon a platinum macrodisc electrode. Nafion is found to be an ideal medium for dispersion of MWCNTs and for the formation of a homogeneous composite. The composite has been characterized utilizing SEM, TEM, FT-IR and electrochemical techniques. Electrochemical characterization reveals that the redox activity of the composite is improved with the cumulative effect of MWCNTs and PAA as additives. The electroanalytical behavior of the composite is evaluated towards the sensing of ascorbic acid in the presence of dopamine and uric acid exhibiting a detection limit of 2.5 × 10−7 M.

A selective and sensitive d-xylose electrochemical biosensor based on xylose dehydrogenase displayed on the surface of bacteria and multi-walled carbon nanotubes modified electrode

A novel Nafion/bacteria-displaying xylose dehydrogenase (XDH)/multi-walled carbon nanotubes (MWNTs) composite film-modified electrode was fabricated and applied for the sensitive and selective determination of d-xylose (INS 967), where the XDH-displayed bacteria (XDH-bacteria) was prepared using a newly identified ice nucleation protein from Pseudomonas borealis DL7 as an anchoring motif. The XDH-displayed bacteria can be used directly, eliminating further enzyme-extraction and purification, thus greatly improved the stability of the enzyme. The optimal conditions for the construction of biosensor were established: homogeneous Nafion–MWNTs composite dispersion (10μL) was cast onto the inverted glassy carbon electrode, followed by casting 10-μL of XDH-bacteria aqueous solution to stand overnight to dry, then a 5-μL of Nafion solution (0.05wt%) is syringed to the electrode surface. The bacteria-displaying XDH could catalyze the oxidization of xylose to xylonolactone with coenzyme NAD+ in 0.1M PBS buffer (pH7.4), where NAD+ (nicotinamide adenine dinucleotide) is reduced to NADH (the reduced form of nicotinamide adenine dinucleotide). The resultant NADH is further electrocatalytically oxidized by MWNTs on the electrode, resulting in an obvious oxidation peak around 0.50V (vs. Ag/AgCl). In contrast, the bacteria-XDH-only modified electrode showed oxidation peak at higher potential of 0.7V and less sensitivity. Therefore, the electrode/MWNTs/bacteria-XDH/Nafion exhibited good analytical performance such as long-term stability, a wide dynamic range of 0.6–100μM and a low detection limit of 0.5μM d-xylose (S/N=3). No interference was observed in the presence of 300-fold excess of other saccharides including d-glucose, d-fructose, d-maltose, d-galactose, d-mannose, d-sucrose, and d-cellbiose as well as 60-fold excess of l-arabinose. The proposed microbial biosensor is stable, specific, sensitive, reproducible, simple, rapid and cost-effective, which holds great potential in real applications.

Vanadium Oxide Nanowire–Carbon Nanotube Binder‐Free Flexible Electrodes for Supercapacitors

AbstractVanadium pentoxide (V2O5) layered nanostructures are known to have very stable crystal structures and high faradaic activity. The low electronic conductivity of V2O5 greatly limits the application of vanadium oxide as electrode materials and requires combining with conducting materials using binders. It is well known that the organic binders can degrade the overall performance of electrode materials and need carefully controlled compositions. In this study, we develop a simple method for preparing freestanding carbon nanotube (CNT)‐V2O5 nanowire (VNW) composite paper electrodes without using binders. Coin cell type (CR2032) supercapacitors are assembled using the nanocomposite paper electrode as the anode and high surface area carbon fiber electrode (Spectracarb 2225) as the cathode. The supercapacitor with CNT‐VNW composite paper electrode exhibits a power density of 5.26 kW Kg−1 and an energy density of 46.3 Wh Kg−1. (Li)VNWs and CNT composite paper electrodes can be fabricated in similar manner and show improved overall performance with a power density of 8.32 kW Kg−1 and an energy density of 65.9 Wh Kg−1. The power and energy density values suggest that such flexible hybrid nanocomposite paper electrodes may be useful for high performance electrochemical supercapacitors.

Fabrication of polypyrrole (PPy)/carbon nanotube (CNT) composite electrode on ceramic fabric for supercapacitor applications

Polypyrrole (PPy)/carbon nanotube (CNT) composite electrodes are fabricated on ceramic fabrics for electrochemical capacitor applications. The CNTs are grown on the ceramic fabrics by the chemical vapor deposition (CVD) method and PPy is subsequently coated on them by chemical polymerization. The large surface area and high conductivity of the CNTs on the porous ceramic fabrics enhance their energy storage capacity. PPy provides not only additional capacitance as an active material, but also enhances the adhesion between the CNTs and ceramic fabrics. Furthermore, PPy acts as a conducting binder for connecting every individual CNT to increase the capacitance. The morphology of the PPy–CNTs on the ceramic fabrics is confirmed by SEM and TEM, and the electrochemical characteristics are investigated by cyclic voltammetry and galvanostatic charge–discharge tests.

Asparagine quantification in cellular culture media using copper modified carbon nanotubes composite electrodes

Direct quantification of Asparagine (Asp) in a Streptomyces sp. M7 ( SM7) culture medium was performed using multi-wall carbon nanotubes composite electrodes modified with copper microparticles (CNTPE-Cu). A sensitive and fast response is achieved at CNTPE-Cu after additions of SM7 cultures supernatant, without interference of the culture medium components. This response allows determining the Asp concentration as a function of the bacteria growth. The results reveal that the SM7 bacteria consume Asp as a carbon and nitrogen sources in the absence of another carbon source such as glucose.

Enhanced Stretchability of Gold and Carbon Nanotube Composite Electrodes

Gold have been used as an electrode materials having a good mechanical flexibility as well as electrical conductivity, however the stretchability of the gold on a flexible substrate is poor because of its small elastic modulus. To overcome this mechanical inferiority, the reinforcing gold is necessary for the stretchable electronics. Among the reinforcing materials having a large elastic modulus, carbon nanotube (CNT) is the best candidate due to its good electrical conductivity and nanoscale diameter. Therefore, similarly to ferroconcrete technology, here we demonstrated gold electrodes mechanically reinforced by inserting fabrics of CNTs into their bodies. Flexibility and stretchability of the electrodes were determined for various densities of CNT fabrics. The roles of CNTs in resisting electrical disconnection of gold electrodes from the mechanical stress were confirmed using field emission scanning electron microscope and optical microscope. The best mechanical stability was achieved at a density of CNT fabrics manufactured by 1.5 ml spraying. The concept of the mechanical reinforced metal electrode by CNT is the first trial for the high stretchable conductive materials, and can be applied as electrodes materials in various flexible and stretchable electronic devices such as transistor, diode, sensor and solar cell and so on.

Electrochemical micro-capacitors of patterned electrodes loaded with manganese oxide and carbon nanotubes

MnO 2 and carbon nanotubes (CNT) composite electrodes have been built on the interdigital stack layers of Fe–Al/SiO 2 and Fe–Al/Au/Ti/SiO 2 for the electrochemical micro-capacitors, using photolithography and thin-film technologies. The electrode properties and the performance of micro-cells are measured and analyzed with cyclic voltammetry (CV), impedance spectroscopy, and galvanostatic charge/discharge test in 0.1 M Na 2SO 4 electrolyte. The vertically aligned CNT, grown on Fe–Al/SiO 2, is more suitable for supporting the pseudocapacitive MnO 2 than the random CNT on Fe–Al/Au/Ti/SiO 2, but ohmic resistance of the former electrode is higher. We have prepared three cells on each stack layer with different electrode materials. The Ragone plot shows systematic variations in power and energy performance, reflecting their differences in electrode structure and polarization loss. The asymmetric cell of a pseudocapacitive positive electrode, loaded with MnO 2 and CNT, exhibits a small IR drop and a high specific energy during discharge. Built on Fe–Al/SiO 2, this asymmetric cell discharges at specific power 0.96 kW kg −1 with specific energy 10.3 Wh kg −1; while on Fe–Al/Au/Ti/SiO 2, the asymmetric cell discharges at power 1.16 kW kg −1 with energy 5.71 Wh kg −1.

Electrocatalytic detection of phenolic estrogenic compounds at NiTPPS|carbon nanotube composite electrodes

A Ni(II)tetrakis(4-sulfonatophenyl) porphyrin (NiTPPS)|carbon nanotube composite electrode that shows strong catalytic and antifouling capability was developed to detect a series of phenolic endocrine compounds including bisphenol A, nonylphenol and ethynylestradiol. This electrode was fabricated by electropolymerizing NiTPPS complexes on a carbon nanotube-modified glassy carbon electrode. Optimized experimental parameters including a hydrodynamic potential of 0.7 V for flow injection analysis (FIA) and a NiTPPS surface coverage of 2.2 nmol cm −2 (standard deviation 0.2 nmol cm −2; n = 6) were obtained for detection of the endocrine disrupting compounds. The sensor responded well to all the tested compounds with limits of detection ranging from 15 nmol L −1 to 260 nmol L −1 (based on three times S/N ratio) under FIA conditions. Both carbon nanotubes and NiTPPS account for the excellent performance of the composite modified electrode.

Transparent and flexible electrodes and supercapacitors using polyaniline/single-walled carbon nanotube composite thin films

Large-scale transparent and flexible electronic devices have been pursued for potential applications such as those in touch sensors and display technologies. These applications require that the power source of these devices must also comply with transparent and flexible features. Here we present transparent and flexible supercapacitors assembled from polyaniline (PANI)/single-walled carbon nanotube (SWNT) composite thin film electrodes. The ultrathin, optically homogeneous and transparent, electrically conducting films of the PANI/SWNT composite show a large specific capacitance due to combined double-layer capacitance and pseudo-capacitance mechanisms. A supercapacitor assembled using electrodes with a SWNT density of 10.0 µg cm(-2) and 59 wt% PANI gives a specific capacitance of 55.0 F g(-1) at a current density of 2.6 A g(-1), showing its possibility for transparent and flexible energy storage.

Graphene and carbon nanotube composite electrodes for supercapacitors with ultra-high energy density

We describe a graphene and single-walled carbon nanotube (SWCNT) composite film prepared by a blending process for use as electrodes in high energy density supercapacitors. Specific capacitances of 290.6 F g(-1) and 201.0 F g(-1) have been obtained for a single electrode in aqueous and organic electrolytes, respectively, using a more practical two-electrode testing system. In the organic electrolyte the energy density reached 62.8 Wh kg(-1) and the power density reached 58.5 kW kg(-1). The addition of single-walled carbon nanotubes raised the energy density by 23% and power density by 31% more than the graphene electrodes. The graphene/CNT electrodes exhibited an ultra-high energy density of 155.6 Wh kg(-1) in ionic liquid at room temperature. In addition, the specific capacitance increased by 29% after 1000 cycles in ionic liquid, indicating their excellent cyclicity. The SWCNTs acted as a conductive additive, spacer, and binder in the graphene/CNT supercapacitors. This work suggests that our graphene/CNT supercapacitors can be comparable to NiMH batteries in performance and are promising for applications in hybrid vehicles and electric vehicles.