Carbon Nanotube Paste Electrode Research Articles

Molecularly imprinted-multiwall carbon nanotube paste electrode as a biosensor for voltammetric detection of rutin

A new molecularly imprinted polymer–multiwall carbon nanotube paste electrode (MIP–MWNPE) was prepared as a voltammetric sensor for rutin. The electrochemical behavior of rutin at the surface of the modified electrode was studied using cyclic voltammetry (CV) and square wave voltammetry (SWV). Under the optimized conditions, the oxidation peak current of rutin showed two linear dynamic ranges (0.08–1.4 μM and 2.0–160.0 μM) with a detection limit of 0.05 μM, using square wave voltammetric method. The RSD% for 5.0 and 10.0 μM determination of rutin were 2.7% and 2.9%, respectively. The kinetic parameters such as electron transfer coefficient (α) and charge transfer rate constant (ks/s−1) were also determined using the electrochemical approach. The modified electrode showed good sensitivity, special selectivity, and stability for rutin analysis. It was successfully applied for the determination of rutin in real samples such as urine and pharmaceutical formulation with satisfactory results.

Simultaneous voltammetric determination of Brilliant Blue and Tartrazine in real samples at the surface of a multi-walled carbon nanotube paste electrode

A carbon paste electrode (CPE) chemically modified with multi walled carbon nanotubes (MWCNTs) was used for the sensitive and selective determination of Brilliant Blue (BB) and Tartrazine (Tz) by voltammetric methods such as cyclic, differential pulse and square wave voltammetry (CV, DPV, and SWV), and chronoamperometry (CHA). The peak current increased linearly with the BB concentration within the concentration range of 0.05 to 22.0 μmol l−1 for DPV and from 0.05 to 25.0 μmol l−1 for SWV. The detection limits (S/N > 3) for BB by DPV and SWV were found to be 9.0 and 5.0 nmol l−1, respectively. Results of CV showed two well-resolved anodic waves with the peak separation approximately 200 mV for the electrochemical oxidation of BB and Tz, which makes it possible for simultaneous determination of both compounds. The treatment of the CV data showed that the redox of BB and Tz was reversible diffusion-controlled and totally irreversible reactions, respectively. The diffusion coefficient (D/cm2 s−1 = 2.8 × 10−5) for BB was determined using chronoamperometry. DPV method was applied for the quantitative determination of BB and Tz. High sensitivity and selectivity, low detection limit (nanomolar), good reproducibility, easy preparation and regeneration of the electrode make it very suitable for the determination of BB and Tz in soft drinks.

Electrochemical and catalytic investigations of levodopa and folic acid by modified carbon nanotube paste electrode

A sensitive and selective electrochemical method for the determination of levodopa (LD) was developed using a ferrocenemonocarboxylic acid modified carbon nanotubes paste electrode (FMCNPE). The modified electrode exhibited good electrocatalytic activity for electrochemical oxidation of LD at pH 7.0 phosphate buffer solution. The diffusion coefficient (D = 1.44 × 10−6 cm2 s−1), and the kinetic parameters such as the electron transfer coefficient (α = 0.4) and catalytic rate constant (k = 1.8 × 10 3 M−1 s−1) of LD at the surface of FMCNPE were determined using electrochemical approaches. Differential pulse voltammetry (DPV) of LD at the modified electrode exhibited linear dynamic range with a detection limit (3σ) of 70 nM. DPV was used for simultaneous determination of LD and FA at the modified electrode. Finally, this modified electrode was also examined for the determination of LD and FA in urine samples.

Evaluation of Acetylcholinesterase Biosensor Based on Carbon Nanotube Paste in the Determination of Chlorphenvinphos

An amperometric biosensor for chlorphenvinphos (organophosphorus pesticide) based on carbon nanotube paste and acetylcholinesterase enzyme (CNTs-AChE biosensor) is described herein. This CNTs-AChE biosensor was characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The SEM result shows the presence of CNTs and small lumps, due to the enzyme AChE, which has a type of cauliflower formation. From EIS analysis is possible to observe increased R tc for CNTs-AChE biosensor when compared to the carbon nanotube paste electrode for the reaction [Fe(CN)6]4−/3−. Using a chronoamperometric procedure, a linear analytical curve was observed in the 4.90 × 10−7–7.46 × 10−6 M range with limit of detection of 1.15 × 10−7 M. The determination of chlorphenvinphos in the insecticide sample proved to be in agreement with the standard spectrophotometric method, with a 95% confidence level and with a relative error lower than 3%. In this way, the CNTs-AChE biosensor presented easy preparation, fast response, sensitivity, durability, good repeatability, and reproducibility.

Multivariate Optimization Strategies in the Development of an Electroanalytical Method for the Assay of Metoclopramide Using Mercury-Film-Modified Carbon Nanotube Paste Electrode

Abstract The present work describes an electroanalytical method based on adsorptive preconcentration of metoclopramide (MCP) onto mercury-film-modified carbon nanotube paste electrode followed by anodic stripping measures. The method presented a good linear range from 2.0 up 100 µmol L−1 (r = 0.998) and a limit of detection of 0.51 µmol L−1. The determination of MCP was successfully carried out in solid and liquid pharmaceutical formulations, as well as in urine samples without intense sample treatment.

Electrochemical fabrication of novel Pt/poly ( m-toluidine)/Triton X-100 composite catalyst at the surface of carbon nanotube paste electrode and its application for methanol oxidation

In this work, for the first time an aqueous solution of Triton X-100 (TX-100) non-ionic surfactant is used as an additive for electropolymerization of m-toluidine (MT) onto multi-walled carbon nanotube paste electrode (CNTPE), which is investigated as a novel matrix for dispersion of platinum particles. Electrochemical response of the poly ( m-toluidine) film prepared in the presence of TX-100 (PMT/TX-100) is, at least, 20 times higher than that obtained in the absence of the surfactant. The as-prepared substrate is used as porous matrix for dispersion of platinum particles by potentiodynamic method. As-formed novel support and composite catalyst are characterized by scanning electron microscopy (SEM), energy dispersive spectrum (EDS), and electrochemical methods. The SEM images reveal that the deposits are composed of spherical Pt particles. The EDS confirms the presence of Pt on the modified electrode. The electrochemical methanol oxidation reaction (MOR) is studied at the surface of this modified electrode. It has been shown that the PMT/TX-100 at the surface of CNTPE improves the catalytic efficiency of the deposited platinum particles toward MOR. Then, the influence of scan rates of potential and switching potential on the MOR as well as long-term stability of this modified electrode have been investigated by chronoamperometric and cyclic voltammetric methods.

A novel, effective and low cost catalyst for methanol oxidation based on nickel ions dispersed onto poly( o-toluidine)/Triton X-100 film at the surface of multi-walled carbon nanotube paste electrode

In this work, for the first time an aqueous solution of Triton X-100 (TX-100) [t-octyl phenoxy polyethoxy ethanol] non-ionic surfactant is used as an additive for electropolymerization of o-toluidine (OT) onto multi-walled carbon nanotube paste electrode (CNTPE), which is investigated as a novel matrix for dispersion of nickel ions. The growth of polymeric film in the absence of TX-100 is poor, while it considerably increases in the presence of the surfactant and its growth is continued up to 60th cycle. The as-prepared substrate is used as porous matrix for dispersion of transition metal ions of Ni(II) to POT/TX-100 film by immersing the modified electrode in a 0.1 M nickel sulfate solution. The electrochemical characterization of this modified electrode exhibits redox behavior of Ni(III)/Ni(II) couple. It has been shown that POT/TX-100 at the surface of CNTPE improves catalytic efficiency of the dispersed nickel ions toward methanol oxidation. Then, using a chronoamperometric method, the catalytic rate constant, k, for methanol oxidation is found to be 7.40 × 10 4 cm 3 mol −1 s −1. At the end of this work, long-term stability of this modified electrode has been investigated.

A Multiwall Carbon Nanotubes Paste Electrode as a Sensor and Ferrocenemonocarboxylic Acid as a Mediator for Electrocatalytic Determination of Isoproterenol

A Multiwall Carbon Nanotubes Paste Electrode as a Sensor and Ferrocenemonocarboxylic Acid as a Mediator for Electrocatalytic Determination of Isoproterenol

Electrocatalytic oxidation of hydroxylamine at Ni(II)-morin complex modified carbon nanotube paste electrode

A modified electrode, nickel(II)-morin complex modified multi-wall carbon nanotube paste electrode (Ni(II)-MR-MWCNT-PE), has been fabricated by electrodepositing Ni(II)-MR complex on the surface of MWCNT-PE in alkaline solution. The Ni(II)-MR-MWCNT-PE exhibits the characteristic of improved reversibility and enhanced current responses of the Ni(III)/Ni(II) couple compared with Ni(II)-MR complex modified carbon paste electrode (CPE). It also shows better electrocatalytic activity toward the oxidation of hydroxylamine than the Ni(II) modified MWCNT-PE (Ni(II)-MWCNT-PE) and Ni(II)-MR-CPE. Kinetic parameters such as the electron transfer coefficient α, rate constant k s of the electrode reaction and the catalytic rate constant k cat of the catalytic reaction are determined. Moreover, the catalytic currents present linear dependence on the concentration of hydroxylamine from 2.5 × 10−6 to 4.0 × 10−4 mol L−1 by amperometry. The detection limit and sensitivity are 8.0 × 10−7 mol L−1 and 56.2 mA L mol−1, respectively. The modified electrode for hydroxylamine determination is of the property of simple preparation, good stability, fast response and high sensitivity.

A highly sensitive nanostructure-based electrochemical sensor for electrocatalytic determination of norepinephrine in the presence of acetaminophen and tryptophan

A new electrochemical sensor for the determination of norepinephrine (NE), acetaminophen (AC) and tryptophan (Trp) is described. The sensor is based on carbon paste electrode (CPE) modified with 3,4-dihydroxybenzaldehyde-2,4-dinitrophenylhydrazone (DDP) and takes the advantages of carbon nanotubes (CNTs), which makes the modified electrode highly sensitive for the electrochemical detection of these compounds. Cyclic voltammetry (CV) at various scan rates was used to investigate the redox properties of the modified electrode. The apparent charge transfer rate constant, k s, and transfer coefficient, α, for electron transfer between DDP and CNT paste electrode were calculated. The mediated oxidation of NE at the modified electrode was investigated by CV and the values of k, α and diffusion coefficient ( D) were calculated. Under the optimum pH of 7.0, the oxidation of NE occurs at a potential about 215 mV less positive than that of the unmodified CPE. Differential pulse voltammetry (DPV) of NE at the modified electrode exhibited two linear dynamic ranges with a detection limit (3 σ) of 77 ± 2 nM. DPV was used for simultaneous determination of NE, AC and Trp at the modified electrode, and quantitation of NE in some real samples by the standard addition method.

Simultaneous Determination of Phenylhydrazine, Hydrazine and Sulfite Using a Modified Carbon Nanotube Paste Electrode

Simultaneous Determination of Phenylhydrazine, Hydrazine and Sulfite Using a Modified Carbon Nanotube Paste Electrode

Electrochemical Detection of Pesticide in Living Plant and Fish Brain Cell

The three electrode system was used to detect the pesticide fenitrothion (<TEX>$C_9H_{12}NO_5PS$</TEX>. MW=277.24) using cyclic voltammetry (CV) and square wave anodic stripping voltammetry (SWASV). The working electrode was mercury immobilized on a carbon nanotube paste electrode (Hg-CNTPE). At the optimized condition, the limit of detection (LoD) was 0.6 ppt (<TEX>$2.16{\times}10^{-12}\;M$</TEX>), and the relative standard deviation was 0.035% (n=15). And there is more sensitive in detecting fenitrothion than common type carbon nanotube paste electrode. When it was implanted into the brain of live fish (carp), the existence of fenitrothion was measured without any destruction or damage of tissue.

Simultaneous determination of levodopa, NADH, and tryptophan using carbon paste electrode modified with carbon nanotubes and ferrocenedicarboxylic acid

The redox response of a modified carbon nanotube paste electrode of ferrocenedicarboxylic acid was investigated. Cyclic voltammetry, differential pulse voltammetry, and chronoamperometry were used to investigate the electrochemical behavior of levodopa (LD) at modified electrode. Under the optimized conditions (pH 5.0), the modified electrode showed high electrocatalytic activity toward LD oxidation; the overpotential for the oxidation of LD was decreased by more than 190 mV, and the corresponding peak current increased significantly. Differential pulse voltammetric peak currents of LD increased linearly with its concentrations at the range of 0.04 to 1,100 μM, and the detection limit (3σ) was determined to be 12 nM. The diffusion coefficient \( \left( {D = {9}.{2} \times {1}{0^{ - {6}}}{\hbox{c}}{{\hbox{m}}^2}/{\hbox{s}}} \right) \) and transfer coefficient (α = 0.49) of LD were also determined. Mixture of LD, NADH, and tryptophan (TRP) can be separated from one another by differential pulse voltammetry. These conditions are sufficient to allow determination of LD, NADH, and TRP both individually and simultaneously. The modified electrode showed good reproducibility, remarkable long-term stability, and especially good surface renewability by simple mechanical polishing. The results showed that this electrode could be used as an electrochemical sensor for determination of LD, NADH, and TRP in real samples such as urine and water samples.

Simultaneous voltammetric determination of acetaminophen, aspirin and caffeine using an in situ surfactant-modified multiwalled carbon nanotube paste electrode

A carbon nanotube paste electrode modified in situ with Triton X 100 was developed for the individual and simultaneous determination of acetaminophen (ACOP), aspirin (ASA) and caffeine (CF). The electrochemical behavior of these three molecules was investigated employing cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), chronocoulometry (CC) and adsorptive stripping differential pulse voltammetry (AdSDPV). Kramers–Kronig transformation implied that the resulting impedance data were validated and were of very good quality. These studies revealed that the oxidation of ACOP, ASA and CF is facilitated at an in situ surfactant-modified multiwalled carbon nanotube paste electrode (ISSM-CNT-PE). After optimization of analytical conditions employing this electrode at pH 7.0 in phosphate buffer (0.1 M), the peak currents for the three molecules were found to vary linearly with their concentrations in the range of 2.91 × 10 −7–6.27 × 10 −5 M with detection limits of 2.58 × 10 −8, 8.47 × 10 −8 and 8.83 × 10 −8 M for ACOP, ASA and CF respectively using AdSDPV. The prepared modified electrode showed several advantages, such as a simple preparation method, high sensitivity, very low detection limits and excellent reproducibility. Furthermore, the proposed method was employed for the simultaneous determination of ACOP, ASA and CF in pharmaceutical formulations, urine and blood serum samples and the obtained results were found to be satisfactory.

Sensitive and selective determination of phenylhydrazine in the presence of hydrazine at a ferrocene-modified carbon nanotube paste electrode

The determination of hydrazine derivatives is of special interest because they are toxic and widely used in industry, agriculture and explosives. Electrochemical analysis has become of growing importance in industrial process control, environmental monitoring, and different applications in medicine and biotechnology. In the present work, we used a carbon paste electrode modified by ferrocene and carbon nanotubes for simultaneous determination of phenylhydrazine and hydrazine. The modified electrode showed an excellent character for electrocatalytic oxidization of phenylhydrazine and hydrazine with a 310 mV separation of both peaks. Differential pulse voltammetric peak currents of phenylhydrazine and hydrazine increased linearly with their concentrations at the range of 0.85–700 and 16–800 μM, and the detection limits (3σ) were determined to be 0.6 and 14 μM, respectively. Here, we show that this electrode could be used as an electrochemical sensor for determination of phenylhydrazine and hydrazine in real samples (water and urine) with advantages such as short time of analysis, lack of pretreatment procedures and more cheaper in comparison with some routine analysis methods such as chromatography or spectroscopy. The modified electrode showed good reproducibility, remarkable long-term stability, and especially good surface renewability by simple mechanical polishing.

Simultaneous Determination of Ascorbic Acid and Uric Acid by a New Modified Carbon Nanotube-Paste Electrode Using Chloromercuriferrocene

The electrochemical behavior of ascorbic acid (AA) and uric acid (UA) at the surface of a multiwall carbon nanotube-paste electrode (MCNTPE) modified with incorporate chloromercuriferrocene (CMF) was investigated. The voltammetric studies using the MCNTPE/CMF electrode show two well-resolved anodic peaks for AA and UA with a potential difference of 430 mV, revealing the possibility of the simultaneous electrochemical detection of these compounds. The optimum analytical conditions were sought. Linear calibration plots were obtained over the range of 8.0 x 10(-6)-6.9 x 10(-4) M and 2.4 x 10(-6)-6.9 x 10(-4) M with detection limits (3sigma) of 2.6 x 10(-6) and 7.9 x 10(-7) M for AA and UA, respectively. The electrode with the best conditions is applied for selective determination of AA and UA in complex biological and clinical matrices.

Amperometric immunosensor for ricin by using on graphite and carbon nanotube paste electrodes

Ricin is a scheduled chemical warfare agent and biological warfare agent. Attempts were made for the detection of ricin in water samples by utilizing amperometric immunosensors. These electrodes were made by mixing Paraffin oil with graphite powder and multiwalled carbon nanotubes. The graphite paste electrode (CPE) and multiwalled carbon nanotubes paste electrode (MWCNTPE) were tested for their ability to detect 1-naphthol. A sandwich enzyme linked immunosorbent assay system was used to detect ricin. The detection limit for both electrodes was compared. It was found that the response of amperometric sensor is proportional to the ricin concentration in both the cases and is linear in the range 0.625-25 ng/ml for MWCNTPE and 2.5-25 ng/ml for CPE. The SEM showed that the MWCNTPE has revealed crevices/voids in which the antibodies may get trapped. Spectroscopic experiments proved that MWCNTPE adsorbs antibodies better than CPE. The high sensitivity of MWCNTPE was attributed to its better electrochemical properties rather than to its efficiency to adsorb antibodies.

Sensitive and Selective Determination of Phenylhydrazine in the Presence of Hydrazine at a Ferrocene Monocarboxylic Acid Modified Carbon Nanotube Paste Electrode

In the present paper, the use of a carbon paste electrode modified by ferrocene monocarboxylic acid (FMC) and carbon nanotubes prepared by a simple and rapid method was described. The modified electrode showed an excellent character for electrocatalytic oxidization of phenylhydrazine (PHZ) and hydrazine (HZ) with a 300 mV separation of both peaks. Differential pulse voltammetric peak currents of PHZ and HZ increased linearly with their concentrations at the range of 0.8 µM to 700 µM and 16 µM to 800 µM and the detection limits (3σ) were determined to be 0.42 µM and 14 µM, respectively.

Amperometric Response of Hydrogen Peroxide at Carbon Nanotubes Paste Electrodes Modified with an Electrogenerated Poly(Fe(III)‐5‐amino‐phenantroline). Analytical Applications for Glucose Biosensing

AbstractThis work reports the catalytic activity of a polymer electrogenerated from Fe(III)‐5‐amino‐1,10‐phenantroline solution at a carbon nanotubes paste electrode (CNTPE) towards the oxidation and mainly the reduction of hydrogen peroxide. The important role of carbon nanotubes on the generation of poly(Fe(III)‐5‐amino‐1,10‐phenantroline) is demonstrated through the comparison with the behavior of graphite paste electrode (CPE). The polymer electrogenerated at CNTPE largely improves the amperometric detection of hydrogen peroxide at −0.100 V. The analytical application of the resulting electrode is demonstrated in connection with the design of a glucose biosensor based on the deposition of GOx and diluted Nafion on the top of the polymer‐modified CNTPE. The quantification of glucose in human serum samples showed a good correlation with the values obtained by the spectrophotometric technique.

Metallic impurity free carbon nanotube paste electrodes

Electrodes modified with carbon nanomaterials find wide ranging applications in electrochemistry such as in energy generation and storage through to applications in electroanalysis. A substantial limitation is the presence of metallic impurities which vary between batches and can produce erroneous results. Consequently we have explored the electrochemical properties of metallic impurity free carbon nanotube paste electrodes using potassium ferrocyanide and hydrogen peroxide as model compounds. In terms of the latter utilising cyclic voltammetry, a linear range from 0.75 to 3 mM with a limit of detection of 0.19 mM is possible using the electrochemical oxidation of hydrogen peroxide while using the electrochemical reduction of the target analyte, a linear range from 0.5 to 249 mM is possible with a detection limit of 0.43 mM. The ultra-small size of the carbon nanotubes and fabrication methodology result in a tightly bound carbon nanotube electrode surface which does not exhibit thin-layer behaviour resulting in highly reproducible electrodes with the %RSD found to be 5.5%. These analytical ranges, detection limits and reproducibility are technologically useful. The carbon nanotubes utilised are completely free from metallic impurities and do not require lengthy processing to remove impurities and consequently have no variation in the purity of the nanomaterial between batches as is commonly the case for other available carbon nanotube material. The impurity free nature of this nanomaterial allows for highly reproducible and intelligent sensors based on carbon nanotubes to be understood and realised for the first time.