Carbon Nanotube-modified Electrode Research Articles

Application of Poly Dl‐Phenylalanine Modified Carbon Nanotube Electrode for Sensitive and Selective Detection of Tinidazole

AbstractThe present study aimed to design an electrochemical sensor for the detection of tinidazole (TN) by carbon nanotube electrode (CNTE) modified with dl‐phenylalanine (DL‐PA). The unmodified carbon nanotube electrode (UMCNTE) and poly (DL‐PA) modified carbon nanotube electrode (P(DL‐PA) MCNTE) were characterized by Scanning emission microscopy (SEM) images. Electrochemical techniques like cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV), were implemented to evaluate the efficiency of the developed electrode toward the detection of TN. The impact of pH on the modified electrode showed that the P(DL‐PA) MCNTE gave a good voltammetric response at pH 3.5. The effect of accumulation time, scan rate, and variation of concentration of TN at the surface of the developed sensor was analyzed. The scan rate study showed that the reduction reaction of TN involves a two‐electron transfer process and it is adsorption‐controlled. The detection limit studies for CV and DPV gave good linearity in the linear range 0.6 μM to 100.0 μM and 3.0 μM to 100.0 μM respectively. The limit of quantification (LOQ) and limit of detection (LOD) concerning CV were found to be 0.65 μM and 0.19 μM respectively. The LOQ and LOD for DPV were calculated to be 0.33 μM and 0.10 μM respectively. The P(DL‐PA) MCNTE showed good anti‐interferent properties. The developed sensor has good stability, repeatability, and reproducibility for the analysis of TN. The P(DL‐PA) MCNTE was successfully employed in the real sample analysis.

One-step growth of Cu-doped carbon dots in amino-modified carbon nanotube-modified electrodes for sensitive electrochemical detection of BPA.

Copper-doped carbon dots and aminated carbon nanotubes (Cu-CDs/NH2-CNTs) nanocomposites were synthesized by a one-step growth method, and the composites were characterized for their performance. An electrochemical sensor for sensitive detection of bisphenol A (BPA) was developed for using Cu-CDs/NH2-CNTs nanocomposites modified with glassy carbon electrodes (GCE). The sensor exhibited an excellent electrochemical response to BPA in 0.2M PBS (pH 7.0) under optimally selected conditions. The linear range of the sensor for BPA detection was 0.5-160μM, and the detection limit (S/N = 3) was 0.13μM. Moreover, the sensor has good interference immunity, stability and reproducibility. In addition, the feasibility of the practical application of the sensor was demonstrated by the detection of BPA in bottled drinking water and Liu Yang River water.

Effect of NH2-MWCNTs/CF anodes on the power generation performance of SMFCs

The carbon nanotube-modified anodes have been widely recognized as one of the most effective methods to improve the conductivity of the anode and enhance the performance of microbial fuel cells. And there are few studies on the effect of amino-functionalized carbon nanotube-modified anodes on the performance of sediment microbial fuel cells (SMFCs) systematically. In this paper, we prepared amino-functionalized carbon nanotube-modified electrodes and constructed SMFCs using them to study the effect of amino-functionalized carbon nanotubes on the power generation performance of SMFCs. The results showed that the highest output voltage of NH2-functionalized multi-walled carbon nanotube (NH2-MWCNT)-modified carbon felt (CF) SMFCs (529.15 mV) was significantly higher than that of CF (474.5 mV). And the power density of SMFCs with 10% NH2-MWCNTs/CF reached a maximum of 58.3 mW/m3. There are because NH2-MWCNTs surface has a larger specific surface area and a porous structure, enhancing electron conduction pathway helps to improve the conductivity of the anode. Therefore, the modification of CF surfaces with NH2-MWCNTs can be used to improve the interfacial properties and positively enhance the power generation performance of SMFCs. This study provides a novel and effective approach to enhance the performance of SMFCs and contributes to the international research on carbon nanotube-modified anodes for energy and environmental applications.

High electrolyte concentration effect on enzymatic oxygen reduction

The nature, the composition and the concentration of electrolytes is essential for electrocatalysis involving redox enzymes. Here, we discuss the effect of various electrolyte compositions with increasing ionic strengths on the stability and activity towards O2 reduction of the bilirubin oxidase from Myrothecium verrucaria (Mv BOD). Different salts, Na2SO4, (NH4)2SO4, NaCl, NaClO4, added to a phosphate buffer (PB) were evaluated with concentrations ranging from 100 mM up to 1.7 M. On functionalized carbon nanotube-modified electrodes, it was shown that the catalytic current progressively decreased with increasing salt concentrations. The process was reversible suggesting it was not related to enzyme leakage. The enzyme was then immobilized on gold electrodes modified by self-assembling of thiols. When the enzyme was simply adsorbed, the catalytic current decreased in a reversible way, thus behaving similarly as on carbon nanotubes. Enzyme mobility at the interface induced by a modification in the interactions between the protein and the electrode upon salt addition may account for this behavior. When the enzyme was covalently attached, the catalytic current increased. Enzyme compaction is proposed to be at the origin of such catalytic current increase because of shorter distances between the first copper site electron acceptor and the electrode.

Synergistic oxidation of simazine in electro-peroxone system with enhanced in-situ electrogenerated H2O2 activity electrode: Performance and mechanism

Conventional electrocatalytic technology is limited by the efficiency of in-situ electrogenerated H2O2 over the cathode, and the degradability for some pollutants with specific structures is poor. In this study, tert-butyl-anthraquinone modified carbon nanotube electrode (CNT/TBAQ) was used as a cathode to assess the degradation efficiency of pollutants in synergy with O3. The surface hydrophobicity of the modified electrode was improved, the proportion of oxygen-containing functional groups was increased by 4.3%, and the catalytically active sites of the material were increased. Compared with electrochemical and ozone technology, the electro-peroxone process could basically achieve complete removal of simazine within 6 min. The TOC removal rate also reached 62.3% after 120 min. Within 90 min, the H2O2 concentration of the CNT/TBAQ cathode reached 583.36 mg/L with current efficiency of 86%. During the electro-peroxone process, the H2O2 produced by electroreduction reacted with ozone to produce a large amount of •OH, which improved the mineralization of pollutants. Degradation intermediates of simazine was identified by LC-MS and detailed transformation pathways was proposed. After 10 cycles, the CNT/TBAQ cathode still maintained a strong ability to produce H2O2 and oxidize pollutants. These results indicate that CNT/TBAQ combined with O3 oxidation, can improve the pollutant degradation efficiency, providing a promising technology for trace organic pollutant abatement.

Electrochemical sensing of methotrexate in the presence of folic acid using PAMAM dendrimer-functionalized multiwalled carbon nanotube-modified electrode.

This works presents a novel electrochemical sensor based on the third-generation poly(amidoamine) dendrimer (G3 PAMAM)-functionalized multiwalled carbon nanotube (MWCNT)-modified screen-printed graphite electrode (SPGE) for the simple and sensitive detection of methotrexate (MTX). The carboxylated MWCNTs were covalently functionalized with amino groups of G3 PAMAM and characterized using different techniques. The sensing ability of the designed nanosensor (MWCNTs-PAMAM/SPGE) was tested using differential pulse voltammetry (DPV), chronoamperometry (CHA), linear sweep voltammetry (LSV), and cyclic voltammetry (CV). To investigate the electrocatalytic activity of PAMAM-functionalized MWCNTs, a comparative electrochemical analysis was carried out and it was determined that PAMAM-functionalized MWCNT-modified SPGE showed good electrocatalytic performance for MTX oxidation compared to the unmodified SPGE. The MWCNT-PAMAM/SPGE lead to a reduced overpotential of MTX oxidation of about 300 mV and enhanced current of about 9 μA of the unmodified SPGE. Experiments were performed for the quantitative determination of MTX using the DPV technique. The response peak current linearly related against MTX concentration in the ranges from 0.01 to 110.0 μM and a limit of detection (LOD) equal to 0.003 μM. Also, MWCNT-PAMAM/SPGE exhibits good catalytic ability toward MTX determination in the presence of folic acid (FA), and the separation of their oxidation peaks (peak potential difference = 320 mV) simultaneously detected the above compounds. To prove the applicability of the MWCNT-PAMAM/SPGE sensor, the concentrations of MTX and FA in pharmaceutical products and biological samples were determined. The calculated recoveries were close to 100%, which indicates that the method might be assumed to be accurate.

Determination of Curcumin on Functionalized Carbon Nano Tube Modified Electrode and Probing its Interaction with DNA and Copper Ion

Determination of Curcumin on Functionalized Carbon Nano Tube Modified Electrode and Probing its Interaction with DNA and Copper Ion

Electrochemical sensing of fentanyl as an anesthesia drug on NiO nanodisks combined with the carbon nanotube-modified electrode.

Fentanyl was successfully determined in the current effort based on hexagonal NiO nanodisks (HG-NiO-NDs) fabricated by the hydrothermal protocol. The synergism of HG-NiO-NDs with multiwall carbon nanotubes (MWCNTs), large specific surface area, and active material enabled the electrochemical sensor to show potent electrochemical behavior. Admirable performance was found for the fentanyl measurement by the MWCNT and HG-NiO-ND-modified pencil graphite electrode (MWCNT/HG-NiO-ND/PGE). The correlation of oxidation currents with the pH value, concentration, and sweep rate of supporting electrolytes was determined for the optimization of conditions to detect fentanyl. The surfaces of modified and unmodified electrodes were characterized as well. The diffusion-control processes were confirmed on the basis of anodic peak findings. The results also revealed a two-electron transfer process. The linear range was obtained to be 0.01-800.0μM for the fentanyl concentrations on the developed electrode, with the sensitivity of 0.1044μA/mM/cm2. The limit of detection (S/N = 3) was 6.7nM. The results indicated the ability of the modified electrode to fabricate non-enzymatic fentanyl sensor applications.

Polyaniline/carbon nanotube composites in sensor applications

Polyaniline (PA) has outstanding electronic, electrical and chemical properties. The incorporation of carbon nanotubes (CNT) into PA matrix could result in PA/CNT nanocomposites that possess enhanced properties. This review outlines the preparation methods of PA/CNT nanocomposites where they could be prepared by in situ polymerization and solution mixing. In addition, the fabrication methods of electrodes based on PA/CNT nanocomposites to be used in sensors will be investigated. In this regard, such electrodes can be fabricated through in situ synthesis of PA/CNT on electrode surface, electro-polymerization of Ani on carbon nanotube-modified electrode or casting of the prepared PA/CNT on the electrode surface. Also, the use of PA/CNT nanocomposites as sensing materials in biosensors, gas sensors, metal ion sensors, environmental pollutants sensors and pH sensors will be highlighted. The use of such nanocomposites in various types of sensors could be attributed to their remarkable chemical properties, large surface area and outstanding electrical performance.

Plasma Concentration Detection of Aminophylline with Multi-Walled Carbon Nanotube-Modified Electrodes in the Treatment of Ticagrelor-Related Dyspnea.

It was aimed at the plasma concentration detection of aminophylline under multi-walled carbon nanotube (MWNT) modified electrodes and the curative effect of aminophylline for ticagrelor-related dyspnea (TRD). 120 patients with TRD and coronary atherosclerotic heart disease (CAHD) in Wuhan Sixth Hospital Hospital were randomly divided into an intervention group and a control group, with 60 cases in each. The novel chitosan/gold nanoparticles-MWNTs (CTS/Au NPs-MWNTs) composite was prepared for studying the electrochemical behaviors of aminophylline on the electrodes. The clinical curative effect of aminophylline, as well as the levels of peripheral blood T lymphocyte subsets and inflammatory cytokines, was observed in the treatment of TRD. The actual plasma molar concentration of aminophylline was 23.6-47.8 μmol/L. After treatment, the total effective rate in the intervention group was higher than that in the control group significantly (95% VS 65%) (P<0.05). The forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) of the intervention group were better than those of the control group remarkably (P<0.05). The intervention group showed lower levels of tumor necrosis factor-α (TNF-α) and interleukin (IL)-6 as well as the higher IL-10 significantly in serum compared with the control group (P<0.05). After follow-up, there was no cardiovascular death in either group. The CTS/Au NPs-MWNTs could be used for detecting the plasma concentration of aminophylline in blood samples. Aminophylline could notably relieve the clinical symptoms, reduce the inflammatory response, and regulate the immunity of patients with good safety.

An insight into the thin-layer diffusion phenomena within a porous electrode: Gallic acid at a single-walled carbon nanotubes-modified electrode

• Glassy carbon electrode was modified with single-walled carbon nanotubes. • Electrochemical behaviour of gallic was studied. • Chronoamperometry was applied for clarifying diffusion processes in thin-layer. • Diffusion phenomena were linked to current signal. • A difference in electrochemical behaviour in various buffers was explained. The electrochemical behavior of gallic acid at a single-walled carbon nanotubes-modified glassy carbon electrode, in an acetate buffer, a model wine buffer and the Britton-Robinson buffer was studied. The elucidation of phenomena, related to the electrochemical behaviour, was performed using cyclic voltammetry and chronoamperometry. Analysis of chronoamperometric results revealed that overall processes, responsible for current signal are mostly related to diffusion phenomena. These phenomena can be divided into four processes that take place either in a thin-layer or/and in a solution depending on the buffer used. By comparative analysis of chronoamperometric and voltammetric results “in real time”, the effects of scan rate, concentrations of gallic acid and layer thickness have on voltammetric signal are discussed in the light of diffusion processes that take place in thin-layer. Finally, comparative analyses of cyclic voltammograms and chronoamperograms, recorded at different pH values, have revealed that low sensitivity at high pH values can be attributed to hampered diffusion. These findings can be useful in elucidating electrochemical behaviour of various species (not only of gallic acid) using an electrode containing carbon nanotubes.

Preparation of Pt/CNT Thin-Film Electrodes by Electrochemical Potential Pulse Deposition for Methanol Oxidation

High-quality performance of catalysts is increasingly required to meet industry exigencies. However, chemical synthesis is often insufficient to maximize the potential properties of the catalysts. On the other hand, electrochemical synthesis has arisen as a promising alternative to overcome these limitations and provide precise control in the preparation of catalysts. In this sense, this work involved the well-controlled electrochemical synthesis of a catalyst based on platinum nanoparticle deposition on carbon nanotubes using only electrochemical treatments. Thin films of functionalized carbon nanotubes were cast onto the surface of a glassy carbon electrode using potential pulsed electrodeposition, resulting in a better distribution of the carbon nanotubes on the electrode when comparing with traditional methods. Then, platinum nanoparticles were electrodeposited on the carbon nanotube-modified electrode. To check the performance of the catalyst and the relevance of the electrochemical synthesis treatments, the samples were analyzed as electrocatalysts towards methanol electrooxidation, showing an important improvement in the catalytic activity in comparison with electrodes that were prepared by traditional methodologies.

Application of Nano-Silver Modified Carbon Nanotube Electrode as Electrochemical Sensor for Detecting Cyanide in Food

Since the discovery of carbon nanotubes, carbon nanotubes have quickly become a research hotspot for scholars worldwide due to their unique special properties such as mechanical, electronic, and chemical properties. It can be considered that the graphite sheet is folded into a carbon cylinder for application, and the carbon nanotubes can be divided into multi-walled carbon nanotubes. This article aims to study the electrochemical sensor for the detection of cyanide in food by nano-silver modified carbon nanotube electrode. In this article, the single-variable method and mathematical statistics are used to compare the electrochemical behavior of carbon nanotube ceramic electrodes with traditional carbon ceramic composite electrodes (CCE). At the same time, the different electrochemical responses of some biologically active molecules on the two electrodes were detected. The data were studied by mathematical analysis and the data were fitted by big data. Experimental data shows that NCE has a greater current response to these biomolecules at the same geometric area, and also changes the redox potential. It shows the advantages of NCE electrodes as sensors. NCE has a catalytic effect on the oxidation and reduction of H202 and NADH. Under the same experimental conditions, the contents of two substances H1O2 and NADH were detected using NCE and CCE, respectively. The experimental data show that the detection limit, sensitivity, and linear range of the electrochemical sensor for the detection of cyanide in food by the nano-silver modified carbon nanotube electrode have significantly improved compared with CCE, and the economic benefit has increased by about 16%. The degree of savings is increased by about 50%, which further proves that NCE has better electrochemical activity than CCE and is more suitable for the application of electrical analysis.

Reversible Cyclic Voltammograms and Electrocatalytic Detection of Vitamin C by Carbon Nanotube Modified Electrode: A Comprehensive Electrochemical Experiment

Reversible Cyclic Voltammograms and Electrocatalytic Detection of Vitamin C by Carbon Nanotube Modified Electrode: A Comprehensive Electrochemical Experiment

Direct electron transfer-type bioelectrocatalysis by membrane-bound aldehyde dehydrogenase from Gluconobacter oxydans and cyanide effects on its bioelectrocatalytic properties

The bioelectrocatalytic properties of membrane-bound aldehyde dehydrogenase (AlDH) from Gluconobacter oxydans NBRC12528 were evaluated. AlDH exhibited direct electron transfer (DET)-type bioelectrocatalytic activity for acetaldehyde oxidation at several kinds of electrodes. The kinetic and thermodynamic parameters for bioelectrocatalytic acetaldehyde oxidation were estimated based on the partially random orientation model. Moreover, at the multi-walled carbon nanotube-modified electrode, the coordination of CN− to AlDH switched the direction of the DET-type bioelectrocatalysis to acetate reduction under acidic conditions. These phenomena were discussed from a thermodynamic viewpoint.

Zinc Oxide Nanoparticles Supported on Multi‐walled Carbon Nanotube Modified Electrode for Electrochemical Sensing of a Fluoroquinolone Drug

AbstractA facile, and novel construction strategy invented on electrochemical procedures for the assemblage of zinc oxide nanoparticles (ZnO NPs) with a multiwalled carbon nanotube modified carbon paste electrode (ZnO‐MWCNTMCPE) to ascertain the fluoroquinolone drug‐Moxifloxacin (MOX). The ZnO‐MWCNTMCPE can significantly improve the electron transfer process and lessen the impedance of the surface of the electrode. Besides, the oxidation of MOX has remarkably enhanced on the modified electrode. Under the optimal experimental conditions, the empirical results exhibited that the oxidation peak current was linearly proportional to the concentration of MOX in the range of 1.0×10−7 to 2.4×10−6 mol L−1 with a detection limit of 0.452×10−7 mol L−1. To analyze the practicality of the MOX determination technique in real samples, the intended sensor manipulated for the adjudication of MOX in human urine specimens, and the results authenticated the explore of MOX with the highest accuracy. Further, the proposed sensor system exercised for the simultaneous evaluation of paracetamol (ACOP) and MOX, the DPV technique unveiled the well‐separated peaks among ACOP (0.188 mV) and MOX (0.814 mV) with a peak separation (ΔE) of 626 mV in real samples. Therefore, the suggested system could sense and discover the MOX in the biological systems.

Dually enhanced homogenous synthesis of molybdophosphate by hybridization chain reaction and enzyme nanotags for the electrochemical bioassay of carcinoembryonic antigen

Amagnetic bead (MB)-based sandwich biorecognition reactions is combinedwith a gold nanoprobe-induced homogenous synthesis of molybdophosphate to develop a novel bioassay method for the electrochemical detection of the tumor biomarker of carcinoembryonic antigen (CEA). The nanoprobe is prepared through the specific loading of numerous alkaline phosphatase (ALP)-functionalized gold nanoparticles (Au NPs) on a double-stranded DNA (dsDNA) produced by the CEA aptamer-triggered hybridization chain reaction (HCR). Both the large amounts of PO43- produced by the ALP catalytic hydrolysis of pyrophosphate and the phosphate backbones of dsDNA can react with the added MoO42- to generate electroactive molybdophosphates. So, the gold nanoprobe was used for signal tracing of the sandwich bioassay of CEA at a constructed antibody-functionalized MB platform. The sensitive electrochemical measurement of molybdophosphate produced from the quantitatively captured nanoprobes at a carbon nanotube-modified electrode (measured at about 0.12V vs. Ag/AgCl, 3M KCl) enabled the convenient signal transduction of the method. Due to the dually enhanced synthesis of molybdophosphate by the HCR and multi-enzyme Au NP nanotags, this method shows a wide linear range from 0.05pgmL-1 to 10ngmL-1 along with a low detection limit of 0.027pgmL-1. In addition, the MB-based biorecognition reaction and the homogeneous synthesis of molybdophosphate are much convenient in manipulations. These excellent performances decide the extensive application potentials of the method. Graphical abstract A magnetic bead-based bioassay method was simply developed for the electrochemical detection of carcinoembryonic antigen. The dually enhanced homogenous synthesis of molybdophosphate by hybridization chain reaction (HCR) and enzyme nanotags and the sensitive electrochemical measurement of molybdophosphate at a carbon nanotube (CNT)-electrode enable ultrasensitive signal transduction of the method.

Determination of levofloxacin in pharmaceutical formulations and urine at reduced graphene oxide and carbon nanotube-modified electrodes

In this paper, we compare reduced graphene oxide (RGO) electrode with multi-walled carbon nanotubes (MWCNT) as modifiers for the sensitive detection of levofloxacin. The RGO-based sensor showed higher currents for levofloxacin compared with the MWCNT-modified (4-fold) and unmodified electrodes (20-fold). A thin-layer adsorptive process was verified for the oxidation of levofloxacin on the RGO-modified electrode which explains the higher currents. Differential pulse voltammetry (DPV), square wave voltammetry (SWV), and amperometric detection using flow-injection analysis (FIA-AMP) were evaluated for levofloxacin determination in urine and pharmaceutical samples. Detection limits of 1.45, 6.70, and 1.90 μmol L−1 and recovery levels of 91, 106, and 103%, respectively were obtained. A relative standard deviation lower than 7.7% indicated proper precision. The FIA-AMP using the RGO-modified electrode presented high analytical frequency (around 100 injections per hour) and thus was selected for the analysis of the samples. Statistically, similar results (95% confidence level) compared with ultra-fast liquid chromatography (UFLC) analysis and recovery level of 96% for the analysis of urine were obtained.

Highly Sensitive Detection of Dopamine, Ascorbic and Uric Acids using Dianix Yellow/Multi-walled Carbon Nanotubes Modified Electrode

A glassy carbon electrode has been modified by electrochemical polymerization of dianix yellow along with multi-walled carbon nanotubes (MWCNTs) and utilized for the selective determination of dopamine (DA), ascorbic acid (AA) and uric acid (UA). Atomic force microscopy and scanning electron microscopy images were obtained to compare the surface morphology and topography of the bare and modified electrodes. Also, the electrochemical activities of DA, AA, and UA on the bare and modified electrodes were evaluated with the use of cyclic, linear sweep and differential pulse voltammetry (DPV). Large peak separation, good sensitivity, and stability allow to apply the poly-dianix yellow/MWCNTs modified electrode for the determination of DA individually and in the presence of AA and UA. The DPV data showed the linearity of DA, AA, and UA peak currents in the concentrations ranges of 7–2500 nM, 5–110 µM, and 0.100–7.500 µM with the detection limits of 6.1, 99 and 8.9 nM, respectively. The proposed electrode was applied for the quantification of dopamine in human blood serum samples.

Functionals Aspects and Simultaneous Detection of Dopamine, Ascorbic Acid and Uric Acid Using Chitosan-Catechol Graphene and Carbon Nanotube Modified Electrodes

Dopamine functions as a neurotransmitter in the brain. The dysfunction of the dopaminergic system is the leading cause of numerous diseases such as Parkinson’s disease. Hence, it is important to find selective and sensitive detection methods for the early diagnosis of diseases related to the abnormal levels of dopamine. In this study, we show a new electrochemical sensing platform based on carbon nanotube (SWCNT) and a sheet of graphene (GRA). The novelty of our sensor is the coating of the substrates with chitosan-catechol (CC) by electrodeposition, enhancing the dopamine response by 70%. The dose-response for each set of electrodes (bare CNT, bare GRA, and coated CNT as well as coated GRA) was measured. Finally, the electrodes were tested in cerebrospinal fluid (artificial and human), for the detection of millimolar to nanomolar levels of dopamine. The electrodes exhibited high sensitivity (2.03mA mol·L-1, 1.45 mA mol·L-1, 0.0298 mA mol·L-1, and 0.0559 mA mol·L-1 for the modified CNT, bare CNT, modified GRA and bare GRA, respectively, for the oxidation of DA. The oxidation peak current was proportional to the concentration of DA in the range from 50×10-6 to 50x10-9 M (n= 6, r2 =0.98). The dopamine recovery in human CSF were, 49-78% and 65-65% with coated graphene and CNT electrodes, respectively. Our results indicate that the CC modified CNT electrodes achieved the best recovery, sensitivity, limit of detection, and selectivity compared to the uncoated CNT as well as the coated and uncoated graphene electrodes.