Multi-walled Carbon Nanotube-modified Electrode Research Articles

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.

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.

Functionalised multi-walled carbon nanotubes-modified electrode for sensitive determination of Diuron in seawater samples

ABSTRACTThis work was focused in to develop an electroanalytical method based on a direct modification of a glassy carbon electrode (GCE) by the deposition of successive aliquots of diluted dispersions of functionalised carbon nanotubes (MWCNT-COOH) in ethanol (0.1 mg.mL−1) aiming the determination of Diuron into seawater samples, a common antifouling substance, using differential pulse voltammetry as electroanalytical technique. The GCE/MWCNT-COOH showed a sensitivity of 2.20 μA/μmol L−1 about 10 times higher than the unmodified counterpart (GCE) which showed a sensitivity of 0.192 μA/μmol L−1. The limits of detection and quantificationwere 6.88 × 10−8 and 2.29 × 10−7 mol L−1 for GCE/MWCNT-COOH while for GCE were 7.87 × 10−7 and 2.62 × 10−6 mol L−1, respectively. The applicability was evaluated with spiked detectable amounts of Diuron into seawater samples. The recovery results were between 76% and 119%.

Preparation of Samarium Oxide Nanoparticles Decorated Functionalized Multiwall Carbon Nanotubes Modified Electrode for the Electrochemical Determination of Catechol

Preparation of Samarium Oxide Nanoparticles Decorated Functionalized Multiwall Carbon Nanotubes Modified Electrode for the Electrochemical Determination of Catechol

Electrochemical Determination of Nitrite Using a Reduced Graphene Oxide–Multiwalled Carbon Nanotube-Modified Glassy Carbon Electrode

ABSTRACTGraphene oxide nanosheets were encapsulated with multiwalled carbon nanotubes by direct reduction on glassy carbon to obtain a reduced graphene oxide/multiwalled carbon nanotube-modified electrode. The encapsulated multiwalled carbon nanotubes facilitated the reduction of graphene oxide with characterization by atomic force microscopy, scanning electron microscopy, and Raman spectroscopy. The reduced graphene oxide–multiwalled carbon nanotube-modified electrode exhibited high catalytic activity for the oxidation of nitrite. Under the optimized conditions, the modified electrode had a linear dynamic range from 0.2 to 640 µM with a detection limit of 0.07 µM. This device was used to determine nitrite in water samples and satisfactory results were obtained.

Multiwall carbon nanotube-modified electrode as a nanosensor for electrochemical studies and stripping voltammetric determination of an antimalarial drug

MWCNTs/CPE exhibited excellent effect towards the oxidation of hydroxychloroquine.

Preparation of Copper-iron Hexacyanoferrate Loaded Multi-walled Carbon Nanotubes Modified Electrode for the Determination of Nitrite

Preparation of Copper-iron Hexacyanoferrate Loaded Multi-walled Carbon Nanotubes Modified Electrode for the Determination of Nitrite

Differential pulse anodic stripping voltammetric determination of Hg2+ at poly(Eriochrome Black T)-modified carbon paste electrode

The electrochemical behavior of Hg2+ was investigated in poly(Eriochrome Black T)-modified carbon paste electrode (CPE) using cyclic voltammetry (CV). Poly(Eriochrome Black T) was prepared in an alkaline medium on the surface of the CPE using a solution of Eriochrome Black T with the CV technique. The electrochemical impedance study revealed a better charge transfer kinetics at the modified electrode. The effects of variation of the experimental conditions, such as the concentration of electrolytes, pH, deposition time, and the deposition potential, which maximize current efficiency were studied. The optimum response of Hg2+ was observed in 1.0 M KCl solution. The differential pulse anodic stripping voltammetric technique was employed successfully to detect Hg2+, which gave a good linear response at low concentration levels of Hg2+. The detection limit was found to be 2.2 × 10−10 M (S/N = 3), which is comparable with that achieved in multiwall carbon nanotube-modified electrode. The remarkable electroanalytical performance of the modified electrode makes it amenable to employ it successfully as an electrochemical sensor for the determination of hazardous pollutant Hg2+ in environmental samples.

Lactose Electrooxidation on the Nickel Oxide Nanoparticles Electrocatalyst Prepared on the Multi-walled Carbon Nanotubes Modified Electrode

The preparation of multi-walled carbon nanotubes–NiO nanoparticles composites (MWCNT–NiO) is presented and the composites were used for modification of glassy carbon electrode for lactose electrooxidation in NaOH. Nickel oxide (NiO) was accumulated on multi-walled carbon nanotubes (MWCNT) by pulsed potential electrodeposition. The structure and nature of the MWCNT–NiO were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results show that NiO nanoparticles were homogeneously electrodeposited on the surfaces of MWCNTs. Also, the electrochemical behaviour of MWCNT–NiO nanoparticles composite in an aqueous solution of alkaline of lactose was studied using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy (EIS). The peak on the voltammogram for MWCNT–NiO composite electrode in alkaline solutions of lactose was observed which was ascribed to the lactose oxidation in alkaline medium. The results obtained are discussed from the point of view of employment of the MWCNT–NiO composites for the catalytic electrodes of sugar-oxygen fuel cells.

Preparation, Characterization and Application of Research of Novel Poly N,N-Dimethylaniline/Multiwalled Carbon Nanotubes Modified Electrode

The method of preparing novel poly N,N-dimethyl aniline(PDMA)/multi-walled carbon nanotubes(MWNT) composite film modified glassy carbon(GC) electrode was investigated.SEM and electrochemical characterizations indicated that the morphology and electrochemical performance of the PDMA film were changed no matter the MWNT was doped or drop coated to DMA.The composite film modified electrode greatly increased the specific surface area and the electrical activation area compared with a single PDMA film modified electrode,indicating that the PDMA and MWNT play important roles in improving the electrochemical properties.The results showed that the electrochemical response of vanillin is much greater on the PDMA/MWNT/GC layers than on the bare GC electrode and other modified electrodes.The over potential was reduced by 148 mV,and the oxidation peak current was increased by about six times.The electrode reaction was an irreversible redox process and was likely an adsorptive process.The numbers of the electron and proton transferred in the electrode reaction were 2 and 1,respectively,the transfer coefficient was calculated to be 0.4062,and the amount of adsorption was 3.527×10-9 mol/cm2.The detection limit was 8.0×10-7 mol/L,and the average recovery was 99.87%.

Determination of Trace Amounts of Sulfamethizole Using a Multi-Walled Carbon Nanotube Modified Electrode: Application of Experimental Design in Voltammetric Studies

The present paper is the first report for the simultaneous investigation of various factors affecting the oxidation peak currents of sulfamethizole (SM) in a 0.20 M Britton-Robinson (B-R) buffer solution. Experimental factors (pH, multiwalled carbon nanotube amount, scan rate, step potential, and modulation amplitude) on voltammetric determination of SM were optimized simultaneously by a central composite rotatable design (CCRD). Then, in the optimized conditions, differential pulse voltammetry (DPV) was applied for selective determination of SM at the surface of a multi-walled carbon nanotube modified carbon paste electrode (MWCNT/CPE).The modified electrode showed enhanced effect on the oxidation peak current of SM. In these conditions the linear dynamic range for SM was from 0.10 up to 131.94 µM and the detection limit was found to be 14.31 nM. The characterization of MWCNT/CPE was carried out bycyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Also, linear sweep voltammetry (LSV) and chronocoulometry of SM were studied. Using these techniques, the diffusion coefficient (D = 4.91 × 10−5 cm2 s−1) and the kinetic parameters such as the electron transfer coefficient (α = 0.79) and exchange current density (j0 = 2.78 × 10−12 µA cm−2) for SM were calculated. The proposed method was then successfully applied to the determination of SM in plasma samples.

Electrochemistry of Metoclopramide at Multi-walled Carbon Nanotube Modified Electrode and Its Voltammetric Detection

A simple, sensitive and inexpensive electrochemical method was developed for the determination of metoclopramide (MCP) with a multi-wall carbon nanotube (MWNT) modified glassy carbon electrode (GCE). MWNT was dispersed into polyacrylic acid (PAA); the aqueous suspension was then cast on GCE electrodes, forming MWNT-PAA films after evaporation of the solvent. The electrochemical behavior of MCP at the MWNT-modified electrode was investigated in detail. Compared with the bare GCE, the MWNT-modified electrode exhibits electrocatalytic activity to the oxidation of MCP because of the significant oxidation peak-current enhancement. Furthermore, various experimental parameters, such as the solution pH value, the amount of MWNT-PAA suspension and accumulation conditions were optimized for the determination of MCP. Based on the electrocatalytic effect of the MWNT-modified electrode, linear sweep voltammetry (LSV) was developed for the determination of MCP with the linear response in the range from 1.0 × 10(-7) to 1.0 × 10(-5) mol L(-1) and a detection limit of 5.0 × 10(-8) mol L(-1). The method has been successfully applied to the determination of MCP in commercial MCP tablets.

Electro-Assisted Immobilization of Methylviologen Cation on Multiwalled Carbon Nanotube Modified Electrode and its Unusual pH Sensing Behavior: A Preliminary Study

Electro-Assisted Immobilization of Methylviologen Cation on Multiwalled Carbon Nanotube Modified Electrode and its Unusual pH Sensing Behavior: A Preliminary Study

Electro-oxidation and adsorptive stripping voltammetric determination of ephedrine and pseudoephedrine at carboxylated multi-walled carbon nanotube-modified electrode

Carboxylated multi-walled carbon nanotubes (MWCNTs) were directly cast onto a glassy carbon electrode to fabricate a MWCNT-modified electrode. The modified electrode exhibited good promotion towards the electrochemical oxidation of ephedrine and pseudoephedrine with greatly enhanced peak currents. Adsorptive stripping voltammetry (AdSV) with accumulation at open circuit potential has been used for quantification of these alkaloids. The method was validated and linear over the concentration range of 1–100 μM for both ephedrine and pseudoephedrine. Under optimal experimental conditions, the limits of detection (based on 3σ) for ephedrine and pseudoephedrine were determined as 0.75 μM and 0.82 μM respectively. The proposed method was successfully applied to pseudoephedrine determination in the presence of acetaminophen or cetirizine. This method has also been used for the determination of pseudoephedrine in some pharmaceutical preparations. In addition the proposed method has been successfully used for determination of ephedrine in diluted urine as a real sample.

The 2011 H. H. Uhlig Summer Research Fellowship -- Summary Report: Catechol-encapsulated Multi-walled Carbon Nanotube Modified Electrode as a New Generation Electrocatalyst for NADH Oxidation

The 2011 H. H. Uhlig Summer Research Fellowship -- Summary Report: Catechol-encapsulated Multi-walled Carbon Nanotube Modified Electrode as a New Generation Electrocatalyst for NADH Oxidation

A study of the electrochemical behavior of an oxadiazole derivative electrodeposited on multi-wall carbon nanotube-modified electrode and its application as a hydrazine sensor

In this study, an oxadiazole multi-wall carbon nanotube-modified glassy carbon electrode (OMWCNT−GCE) was used as a highly sensitive electrochemical sensor for hydrazine determination. The surface charge transfer rate constant, k s, and the charge transfer coefficient, α, for electron transfer between GCE and electrodeposited oxadiazole were calculated as 19.4 ± 0.5 s−1 and 0.51, respectively at pH = 7.0. The obtained results indicate that hydrazine peak potential at OMWCNT−GCE shifted for 14, 109, and 136 mV to negative values as compared with oxadiazole-modified GCE, MWCNT−GCE, and activated GCE surface, respectively. The electron transfer coefficient, α, and the heterogeneous rate constant, k′, for the oxidation of hydrazine at OMWCNT−GCE were also determined by cyclic voltammetry measurements. Two linear dynamic ranges of 0.6 to 10.0 μM and 10.0 to 400.0 μM and detection limit of 0.17 μM for hydrazine determination were evaluated using differential pulse voltammetry. In addition, OMWCNT−GCE was shown to be successfully applied to determine hydrazine in various water samples.

A sensitive and stable biosensor based on the direct electrochemistry of glucose oxidase assembled layer-by-layer at the multiwall carbon nanotube-modified electrode

A novel strategy for fabricating the sensitive and stable biosensor was present by layer-by-layer (LBL) self-assembling glucose oxidase (GOD) on multiwall carbon nanotube (CNT)-modified glassy carbon (GC) electrode. GOD was immobilized on the negatively charged CNT surface by alternatively assembling a cationic poly(ethylenimine) (PEI) layer and a GOD layer. And the direct electrochemistry of GOD in the self-assembled {GOD/PEI} n film was investigated. CNT as an excellent nanomaterial greatly improved the direct electron transfer between GOD in {GOD/PEI} n film and the electrode. And the ultrathin {GOD/PEI} n film on the CNT surface provided a favorable microenvironment to keep the bioactivity of GOD. Moreover, PEI used as an out-layer was adsorbed on the top of the {GOD/PEI} n film to form the sandwich-like structure (PEI/{GOD/PEI} n ), improving the stability of the enzyme electrode. On basis of these, the developed PEI/{GOD/PEI} n /CNT/GC biosensor has a high sensitivity of 106.57 μA mM −1 cm −2, and can measure as low as 0.05 mM glucose. In addition, the biosensor has excellent operational stability with no decrease in the activity of enzyme over a 1-week period. Therefore, the developed strategy making use of the advantages of CNT and LBL assembly is ideal for the direct electrochemistry of the redox enzymes and the construction of the sensitive and stable enzyme biosensor.

Application of graphene-modified electrode for selective detection of dopamine

Graphene was synthesized chemically by Hummers and Offeman method and the graphene-modified electrode was applied in selective determination of dopamine with a linear range from 5 μM to 200 μM in a large excess of ascorbic acid. Selective detection was realized in completely eliminating ascorbic acid, different from the methods based on the potential separations. π–π stacking interaction between dopamine and graphene surface may accelerate the electron transfer whereas weaken the ascorbic acid oxidation on this graphene-modified electrode. The resulted graphene-modified electrode also showed a better performance than multi-walled carbon nanotubes-modified electrode. The phenomena were considered from the elusive two-dimensional structure and unique electronic properties of graphene.

Determination of carbamates in nature water based on the enhancement of electrochemiluminescent of Ru(bpy) 32+ at the multi-wall carbon nanotube-modified electrode

A multi-wall carbon nanotube (MWNT)/Nafion composite film-modified electrode was developed in this paper, and its chemical and electrochemiluminescent (ECL) behavior of tris(2,2′-bipyridyl)ruthenium (Ru(bpy) 3 2+) on this electrode has been investigated in detail. It has been also found that some carbamates were able to enhance the ECL intensity of Ru(bpy) 3 2+ greatly at this modified electrode. Based on which, a sensitive and simple method for determination of pirimicarb, methomyl, aldicarb and carbofuran were developed, and the proposed method has been applied to determine the carbamates in the nature water.

Electrocatalysis of Tryptophan at Multi-Walled Carbon Nanotube Modified Electrode

Acid-treated multi-walled carbon nanotubes (MWNTs) were immobilized on the surface of a glassy carbon electrode to form an MWNT-modified electrode. The electrocatalytic response of the modified electrode towards tryptophan (Trp) was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results demonstrated that the modified electrode exhibited a high degree of catalytic activity towards the oxidation of Trp. An oxidation peak was obtained in Trp solution at the MWNT-modified electrode. Compared with a bare electrode, the peak current had obviously increased, and the peak potential had shifted in a negative direction. However, under the same conditions, no response was observed for other amino acids. The oxidation peak currents were proportional linearly to the concentration of Trp, a property which could be utilized to detect Trp. The determination conditions, such as the concentration, the composition and the pH values of the supporting electrolyte, accumulation time, as well as scan rate etc. were optimized. Under the chosen conditions, the DPV peak current is linear to the concentration of Trp in the range of 2.5 × 10−7 to 1.0 × 10−4 mol L−1, and the detection limit is 2.7 × 10−8 mol L−1. Moreover, the detection is free of interference from other amino acids. The modified electrode has been successfully applied to determine the concentration of Trp in composite amino acid injections, and it displays excellent repeatability and higher sensitivity.