Film-modified Glassy Carbon Electrode Research Articles

Electrochemical determination of 8-hydroxydeoxyguanosine using a carbon nanotube modified electrode

In this work, a multi-wall carbon nanotube (MWNT) film-modified glassy carbon electrode (GCE) was constructed for the determination of 8-hydroxydesoxyguanosine (8-OHdG). The electrochemical behaviors of 8-OHdG were examined using cyclic voltammetry (CV) and linear sweep voltammetry (LSV), suggesting that MWNT film facilitates the electron transfer of 8-OHdG and then significantly enhances the oxidation peak current of 8-OHdG. Finally, a sensitive and simple electrochemical method with a good linear relationship in the range of 8.0 × 10−8 ∼ 5.0 × 10−6 mol 1−1, was developed for the determination of 8-OHdG. The detection limit is 9.0 × 10−9 mol 1−1 for 6-min accumulation. This newly-proposed method was successfully used to detect 8-OHdG in urine samples.

Electrochemical deposition of platinum nanoparticles in multiwalled carbon nanotube–Nafion composite for methanol electrooxidation

Platinum nanoparticles were successfully deposited within a multiwalled carbon nanotube (MWCNT)–Nafion matrix by a cyclic voltammetry method. A Pt(IV) complex was reduced to platinum nanoparticles on the surface of MWCNTs. The resulting Pt nanoparticles were characterized by scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The Pt–MWCNT–Nafion nanocomposite film-modified glassy carbon electrode had a sharp hydrogen desorption peak at about −0.2 V vs. Ag/AgCl (3 M) in a solution of 0.5 M H2SO4, which is directly related to the electrochemical activity of the Pt nanoparticles presented on the surface of MWCNTs. The electrocatalytic properties of the Pt–MWCNT–Nafion nanocomposite-modified glassy carbon electrode for methanol electrooxidation were investigated by cyclic voltammetry in a 2 M CH3OH + 1 M H2SO4 solution. In comparison with the Pt-coated glassy carbon electrode and the Pt–Nafion modified glassy carbon electrode, the Pt–MWCNT–Nafion-modified electrode had excellent electrocatalytic activity toward methanol electrooxidation. The stability of the Pt–MWCNT–Nafion nanocomposite-modified electrode had also been evaluated.

Differential Pulse Anodic Stripping Voltammetric Determination of Cadmium(II) at a Glassy Carbon Electrode Modified with a Nano-TiO2/Chitosan Composite Film

A simple and effective chemically modified electrode for the determination of cadmium(ii) was developed. The chemically modified electrode was prepared by modifying nano-TiO2/chitosan (nano-TiO2/CS) composite film onto a glassy carbon (GC) electrode. Compared with a bare GC electrode and a CS film-modified GC electrode, the nano-TiO2/CS composite film-coated GC electrode significantly improved the sensitivity of determining CdII. The effects of experimental parameters such as modifier composition in the GC electrode, pH of supporting electrolyte, accumulation potential and time were studied for analytical application. Under the optimized working conditions, the peak currents were linear with concentration over the range from 1.0 × 10–9 to 1.0 × 10–6 mol L–1 for CdII. The limit of detection is 2.0 × 10–10 mol L–1 CdII for 180-s accumulation. The application for the assay of trace levels of CdII in real water samples indicates that it is an economical and potent method.

Direct electron transfer of cytochrome c and its biosensor based on gold nanoparticles/room temperature ionic liquid/carbon nanotubes composite film

A robust and effective composite film based on gold nanoparticles (GNPs)/room temperature ionic liquid (RTIL)/multi-wall carbon nanotubes (MWNTs) modified glassy carbon (GC) electrode was prepared by a layer-by-layer self-assembly technique. Cytochrome c (Cyt c) was successfully immobilized on the RTIL-nanohybrid film modified GC electrode by electrostatic adsorption. Direct electrochemistry and electrocatalysis of Cyt c were investigated. The results suggested that Cyt c could be tightly adsorbed on the modified electrode. A pair of well-defined quasi-reversible redox peaks of Cyt c was obtained in 0.10 M, pH 7.0 phosphate buffer solution (PBS). RTIL-nanohybrid film showed an obvious promotion for the direct electron transfer between Cyt c and the underlying electrode. The immobilized Cyt c exhibited an excellent electrocatalytic activity towards the reduction of H 2O 2. The catalysis currents increased linearly to the H 2O 2 concentration in a wide range of 5.0 × 10 −5– 1.15 × 10 −3 M. Based on the multilayer film, the third-generation biosensor could be constructed for the determination of H 2O 2.

Electrochemical methods for simultaneous determination of dopamine and ascorbic acid using cetylpyridine bromide/chitosan composite film-modified glassy carbon electrode

Abstract In this work, cetylpyridine bromide (CPB)/chitosan composite film-modified glassy carbon electrode (GCE) is developed for simultaneous determination of dopamine (DA) and ascorbic acid (AA) by differential pulse voltammetry (DPV). At CPB/chitosan composite film-modified GCE, the oxidation peak potential of AA shifts toward less positive potential and the peak current of AA increases greatly, while the oxidation peak potential of DA shifts toward more positive potential and peak current decreases greatly in comparison with that on bare electrode. Therefore, the common overlapped oxidation peaks of AA and DA can be separated completely by using CPB/chitosan composite film-modified electrode. For AA and DA in mixture, one can well separates from the other with potential difference of about 0.3 V, which is large enough to allow determination of one in the presence of the other. Under the optimum conditions, the anodic peak currents ( I pa ) of DPV are proportional to the concentration of AA in the range of 1.0 × 10 −5 to 2.0 × 10 −3 M, and to that of DA in the range of 4.0 × 10 −5 to 5.0 × 10 −3 M.

Kinetic Studies for the Electrocatalytic Reduction of Bis(2-mercapto-1,3,4-thiadiazoyl)-5,5‘-disulfide at a Poly(3,4-ethylenedioxythiophene) Film-Modified Electrode via Rotating-Disk Electrode Voltammetry

We have carried out a thorough study of the electron exchange reaction between 2,5-dimercapto-1,3,4-thiadiazole (DMcT) and the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT), which dramatically accelerates the redox reactions of DMcT at room temperature. A qualitative analysis of the electron exchange reaction was carried out via UV/vis spectroelectrochemistry, while a quantitative study focused on the charge transfer from the reduced form of PEDOT, (PEDOT)red, to the DMcT dimer (diDMcT) using rotating-disk electrode (RDE) voltammetry. The kinetic model employed to estimate the charge-transfer rate was based on the analysis previously proposed by Savéant and co-workers (J. Electroanal. Chem. 1982, 131, 1), which takes into account charge propagation in a polymer film on an electrode surface and diffusion of a substrate through the polymer film. Thus, such an analysis is appropriate for the system investigated in this study, in which charge propagation occurs in a PEDOT film via self-exchange and diDMcT is incorporated and partitioned into the PEDOT film. Specifically, we found that the so-called “SR” model, in which the overall process of a system is controlled by the catalytic reaction and the diffusion of a substrate through a film, is the most appropriate one to describe the diDMcT/PEDOT system. This was based on the fact that diDMcT is incorporated and partitioned into the PEDOT film and not directly reduced at the glassy carbon electrode (GCE) surface (at potentials where PEDOT catalyzes the reactions) and that charge propagation through the PEDOT film is sufficiently rapid that the slope of the concentration profile of PEDOT is essentially zero over the film’s thickness under the conditions employed in this study. On the basis of such an analysis, the second-order rate constant for the charge-transfer reaction from (PEDOT)red to diDMcT was estimated as 32 M-1 s-1. This value is significantly larger than that previously obtained for the charge-transfer reaction from the reduced form of polyaniline (PAn) to diDMcT (0.03 M-1 s-1), indicating the high electrocatalytic activity of PEDOT toward the redox reactions of DMcT. Moreover, a comparison of the standard rate constants, k0, for the DMcT/diDMcT redox couple obtained at bare and PEDOT film-modified GCEs indicates that the redox reaction is accelerated by a factor of approximately 12 000 at the PEDOT film-coated GCE. These results demonstrate that the use of conducting polymers, such as PEDOT, as efficient electrocatalysts for the redox reactions of DMcT, is a promising strategy to utilize organosulfur compounds as energy-storage materials in lithium-ion rechargeable batteries.

Direct electron transfer and bioelectrocatalysis of hemoglobin on nano-structural attapulgite clay-modified glassy carbon electrode

Direct electrochemistry of hemoglobin (Hb) on natural nano-structural attapulgite clay film-modified glassy carbon (GC) electrode was investigated. The interaction between Hb and attapulgite was examined using UV–vis, FTIR spectroscopy, and electrochemical methods. The immobilized Hb displayed a couple of well-defined and quasi-reversible redox peaks with the formal potential ( E 0 ′ ) of about − 0.366 V (versus SCE) in 0.1 M phosphate buffer solution of pH 7.0. The current was linearly dependent on the scan rate, indicating that the direct electrochemistry of Hb in that case was a surface-controlled electrode process. The formal potential changed linearly from pH 5.0 to 9.0 with a slope value of − 48.2 mV / pH , which suggested that a proton transfer was accompanied with each electron transfer in the electrochemical reaction. The immobilized Hb exhibited excellent electrocatalytic activity for the reduction of hydrogen peroxide without the aid of an electron mediator. The electrocatalytic response showed a linear dependence on the H 2O 2 concentration ranging from 5.4 × 10 −6 to 4.0 × 10 −4 M with the detection of 2.4 × 10 −6 M at a signal-to-noise ratio of 3. The apparent Michaelis–Menten constant K M app for the H 2O 2 sensor was estimated to be 490 μM, showing a high affinity.

Synthesis, characterization and electrocatalytic properties of FeCo alloy nanoparticles supported on carbon nanotubes

FeCo alloy nanoparticles with diameters about 18 nm were synthesized by wet chemical technique, which were characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectrometry (EDX). XRD analysis indicates that the FeCo alloy nanoparticles supported on the surface of carbon nanotubes (CNTs) have body-centered cubic (bcc) phase. TEM images show that the FeCo alloy nanoparticles are in the shape of spheroid on the outer surface of the carbon nanotubes. The electrochemical behavior of film of FeCo/CNT nanocomposites was studied on a glassy carbon (GC) electrode. The cyclic voltammetry results indicate that the FeCo/CNT nanocomposites film-modified GC electrode shows highly electrocatalytic activity toward hydrogen peroxide reduction in the potassium hydrogen phthalate buffer solution, and the electrocatalytic behavior is attributed to the expected catalytic activity of nanosized FeCo alloy nanoparticles supported on the external walls of carbon nanotubes.

Selective Determination of Epinephrine in the Presence of Ascorbic Acid and Uric Acid by Electrocatalytic Oxidation at Poly(eriochrome Black T) Film-modified Glassy Carbon Electrode

An electropolymerized film of eriochrome black T (EBT) has been prepared at a glassy carbon electrode (GCE) by cyclic voltammetry (CV). The poly(EBT) membrane at GCE exhibits an excellent electrocatalytic activity towards the oxidation of epinephrine (EP), ascorbic acid (AA) and uric acid (UA) in acidic solution and reduced the overpotential for the oxidation of EP. The poly(EBT)-coated electrode could separately detect EP, AA and UA in their mixture with the potential differences of 180 and 160 mV for EP-AA and UA-EP, respectively, which are large enough to allow for determination of EP in the presence of AA and UA. Using differential pulse voltammetry, the peak current of EP recorded in pH 3.5 solution was linearly dependent on EP's concentration in the range of 2.5 - 50 microM. Due to its good selectivity and stability, the polymer-coated GCE was successfully applied to the determination of EP in real samples.

DNA−Hemoglobin−Multiwalls Carbon Nanotube Hybrid Material with Sandwich Structure: Preparation, Characterization, and Application in Bioelectrochemistry

A novel multiwall carbon nanotubes (MWNTs)-based hybrid material with sandwich structure (DNA-Hb-MWNTs) was fabricated by alternative electrostatic assembly of hemoglobin (Hb) and DNA on MWNTs. TEM showed that such a nanocomposite behaved as an obvious core−shell structure. SEM proved the well-preserved 3-D structure of DNA-Hb-MWNTs assembled on an electrode. UV−vis and FTIR spectroscopy were used to monitor the assembly procession and also demonstrated that Hb had been sandwiched into DNA and MWNTs without denaturation. A pair of stable and well-defined redox peaks of Hb with a formal potential of about −0.298 V (vs Ag/AgCl) in a pH 6.0 phosphate buffer solution (PBS) were obtained at the DNA-Hb-MWNTs nanocomposite film-modified glassy carbon (GC) electrode (DNA-Hb-MWNT/GC electrode). Compared with the Hb-MWNTs/GC electrode, the DNA-Hb-MWNTs/GC electrode exhibited enhanced faradic current response, and the portion of the electroactive proteins had been greatly improved. Furthermore, the modified electrode also displayed good sensitivity, wide linear range, and long-term stability to the detection of hydrogen peroxide. Such an organized multicomponent biosensor platform may find wide potential applications in biosensors, biocatalysis, biomedical devices, and bioelectronics.

Electrochemical characterization of poly(eriochrome black T) modified glassy carbon electrode and its application to simultaneous determination of dopamine, ascorbic acid and uric acid

A polymerized film of eriochrome black T (EBT) was prepared on the surface of a glassy carbon (GC) electrode in alkaline solution by cyclic voltammetry (CV). The redox response of the poly(EBT) film at the GC electrode appeared in a couple of redox peak in 0.1 M hydrochloride and the pH dependent peak potential was −55.1 mV/pH which was close to the Nernst behavior. The poly(EBT) film-coated GC electrode exhibited excellent electrocatalytic activity towards the oxidations of dopamine (DA), ascorbic acid (AA) and uric acid (UA) in 0.05 mM phosphate buffer solution (pH 4.0) and lowered the overpotential for oxidation of DA. The polymer film modified GC electrode conspicuously enhanced the redox currents of DA, AA and UA, and could sensitively and separately determine DA at its low concentration (0.1 μM) in the presence of 4000 and 700 times higher concentrations of AA and UA, respectively. The separations of anodic peak potentials of DA–AA and UA–DA reached 210 mV and 170 mV, respectively, by cyclic voltammetry. Using differential pulse voltammetry, the calibration curves for DA, AA and UA were obtained over the range of 0.1–200 μM, 0.15–1 mM and 10–130 μM, respectively. With good selectivity and sensitivity, the present method provides a simple method for selective detection of DA, AA and UA in biological samples.

Enhancement of electrochemiluminesence of lucigenin by ascorbic acid at single-wall carbon nanotube film-modified glassy carbon electrode

The electrochemiluminescent behavior of lucigenin on a single-wall carbon nanotube/DMF film-modified glassy carbon electrode was studied in this paper. Comparing with the bare glassy carbon electrode, the electrochemiluminescent of lucigenin at modified electrode is more stable and without tedious procedure for clean-up the surface of modified electrode. It has been found that ascorbic acid could enhance the electrochemiluminescent intensity of lucigenin greatly at this modified electrode. Based on which, a new sensitive and simple electrochemiluminescent method for determination of ascorbic acid could be developed. The condition for the determination of ascorbic acid was optimized. Under the optimized condition, the enhanced electrochemiluminescent intensity versus ascorbic acid concentration was linear in the range of 1.0 × 10 −8 to 4.0 × 10 −6 mol/L with a detection limit of 2.0 × 10 −10 mol/L, and the relative standard derivation for 1.0 × 10 −7 mol/L ascorbic acid was 3.8% ( n = 8). The possible mechanism was also discussed.

Direct electrochemistry and electrocatalysis of horseradish peroxidase immobilized in Nafion-RTIL composite film

The composite film based on Nafion and hydrophobic room-temperature ionic liquid (RTIL) 1-butyl-3-methyl-imidazolium hexafluorophosphate ([bmim] PF 6) was explored. Here, Nafion was used as a binder to form Nafion-ionic liquids composite film and help [bmim] PF 6 effectively adhered on glassy carbon (GC) electrode. X-ray photoelectron spectroscopy (XPS), cyclic voltammtery (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize this composite film, showing that the composite film can effectively adhere on the GC electrode surface through Nafion interacting with [bmim] PF 6 and GC electrode. Meanwhile, doping [bmim] PF 6 in Nafion can also effectively reduce the electron transfer resistance of Nafion. The composite film can be readily used as an immobilization matrix to entrap horseradish peroxidase (HRP). A pair of well-defined redox peaks of HRP was obtained at the HRP/Nafion-[bmim] PF 6 composite film-modified GC electrode through direct electron transfer between the protein and the underlying electrode. HRP can still retain its biological activity and enhance electrochemical reduction towards O 2 and H 2O 2. It is expected that this composite film may find more potential applications in biosensors and biocatalysis.

Electrochemical determination of 2-chlorophenol using an acetylene black film modified glassy carbon electrode

Herein, an insoluble acetylene black (AB) was dispersed into water in the presence of a special kind of surfactant: dihexadecyl hydrogen phosphate (DHP), resulting in a homogeneous and stable AB-DHP suspension. Thus, a novel AB-DHP composite film coated glassy carbon electrode (GCE) was fabricated via coating technology. Additionally, the electrochemical behaviors of 2-chlorophenol at bare GCE, DHP-modifed GCE, and AB-DHP modified GCE were investigated, respectively. Compared with the unmodified and DHP-coated GCE, the AB-DHP film-modified GCE significantly enhances the oxidation peak current of 2-chlorophenol, and thus greatly improves its determining sensitivity, suggesting that this new modified electrode has great potential in the determination of trace level of 2-chlorophenol. All the experimental conditions, which affect the electrochemical response of 2-chlorophenol, were studied. Finally, a sensitive and simple voltammetric method with a good linear relationship in the range 2.0×10−7–4.0×10−5mol/L, was developed. The detection limit of 2-chlorophenol was 5.0×10−8mol/L for 2min accumulation (S/N=3). This electrode was successfully applied to detect 2-chlorophenol in water samples.

Study on the electrochemical behavior and differential pulse voltammetric determination of rhein using a nanoparticle composite film-modified electrode

A sensitive electrochemical method was developed for the differential pulse voltammetric determination of rhein at a glassy carbon electrode (GCE) modified with a nanoparticle composite film. In the present paper, multi-wall carbon nanotube (MWNT) was dispersed into dihexadecyl phosphate (DHP) to give a homogeneous suspension. After the solvent evaporation, a uniform film of MWNT-DHP composite film was obtained on the GCE surface. The MWNT-DHP composite film-modified GCE exhibited excellent electrocatalytic behavior toward the redox of rhein. Compared with an irreversible reduction of rhein at the bare GCE, a reversible redox behavior of rhein was observed at the MWNT-DHP composite film-modified GCE and the redox current was also enhanced greatly. Based on this, a cathodic differential pulse voltammetry (DPV) was applied for the determination of rhein. The experimental parameters, which influence the current of rhein, were optimized. Under optimal conditions, the cathodic DPV measurements were performed and a linear response of rhein was obtained in the range from 1.0 × 10 − 8 to 5.0 × 10 − 6 mol L − 1 and with a limit of detect (LOD) of 5.0 × 10 − 9 mol L − 1 . The proposed procedure was successfully applied to assay rhein in real samples with satisfactory results.

Electrochemical oxidation of morin and interaction with DNA

A poly (tetrafluroethylene)-deoxyribonucleate acid (PTFE-DNA) film-modified glassy carbon electrode (GCE) has been fabricated. The electrochemical oxidation behaviors of morin as well as its interaction with DNA have been studied at PTFE-DNA film-modified GCE and bare GCE by electrochemical methods. This modified electrode shows an enhanced effectiveness towards the oxidation of morin. Importantly, as to the interaction between morin and DNA in solution, characteristic parameters such as the binding stoichiometry and association equilibrium constant according to the Hill model for cooperative binding have been determined on the basis of linear sweep voltammetry and chronocoulometry.

Voltammetric sensor for tinidazole based on poly(carmine) film-modified electrode and its application

A poly(carmine) film-modified glassy carbon electrode (GCE) was fabricated and the electrochemical behavior of tinidazole at the modified electrode was investigated by electrochemical methods. A well-defined reduction peak was observed at 0.61 V and was applied for the determination of tinidazole. Compared with that at a bare GCE, the reduction peak potential of tinidazole shifted negatively and the reduction peak current increased significantly. The influences of some parameters on the reduction of tinidazole were also examined. Based on the experimental data, a possible mechanism was proposed for the electrochemical reaction of tinidazole at the modified electrode. It was found that the reduction peak current was proportional to the concentration of tinidazole in the range from 1.0 × 10 −7 to 5.0 × 10 −5 mol L −1. The detection limit was about 1.0 × 10 −8 mol L −1 after accumulation 90 s at a constant potential of 0.0 V. The proposed method was applied to determine tinidazole in drugs and the result was satisfied.

Studies on electrochemical behaviors of acyclovir and its voltammetric determination with nano-structured film electrode

A multi-wall carbon nanotubes (MWNTs)-dihexadecyl hydrogen phosphate (DHP) film-coated glassy carbon electrode (GCE) was fabricated, and the electrochemical behaviors of acyclovir on the MWNTs-DHP film-coated GCE were investigated by using cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and chronocoulometry (CC). The oxidation peak current of acyclovir increased significantly and the peak potential shifted negatively at the MWNTs-DHP film-modified GCE, compared with that at a bare GCE. The results showed that this nano-structured film electrode exhibited excellent enhancement effects on the electrochemical oxidation of acyclovir. Consequently, a simple and sensitive electroanalytical method was developed for the determination of acyclovir. The oxidation peak current was proportional to the concentration of acyclovir from 8.0 × 10 −8 to 1.0 × 10 −5 mol/L. The detection limit was about 3.0 × 10 −8 mol/L for 60 s accumulation at 0.00 V. The proposed method was demonstrated by using acyclovir tablets and the result was satisfying.

Voltammetric determination of 6-benzylaminopurine (6-BAP) using an acetylene black-dihexadecyl hydrogen phosphate composite film coated glassy carbon electrode

An acetylene black-dihexadecyl hydrogen phosphate (denoted as AB-DHP) composite film coated glassy carbon electrode (GCE) is described for the determination of 6-benzylaminopurine (6-BAP). The electrochemical behavior of 6-BAP was investigated using cyclic voltammetry (CV), linear sweep voltammetry (LSV) and differential pulse voltammetry (DPV). Compared with the unmodified GCE, the AB-DHP film-modified GCE remarkably enhances the oxidation peak current of 6-BAP, suggesting great potential in the determination of trace level of 6-BAP. All the experimental parameters such as supporting electrolyte, the volume of modifier (AB-DHP suspension), scan rate, and accumulation conditions, were optimized. Finally, a sensitive and simple voltammetric method with a good linear relationship in the range of 2.0 × 10 −8 to 5.0 × 10 −6 mol/L, was developed for the determination of 6-BAP. The detection limit was also examined and a low value of 5.0 × 10 −9 mol/L for 5 min accumulation was obtained. This newly proposed method was successfully applied to detect 6-BAP in practical samples.

Preparation and characterization of electrochemical and electrocatalytic behavior of a zinc pentacyanonitrosylferrate film-modified glassy carbon electrode

Modification of a glassy carbon (GC) electrode surface by means of a thin film of zinc pentacyanonitrosylferrate (ZnPCNF) using electrochemical procedures is described and the modifier formation pathway is explained. Cyclic voltammetry of the modified electrode shows one pair of peaks with a surface-confined characteristic in 0.5 M KNO 3 as supporting electrolyte. The effect of different alkali metal cations and some anions in the supporting electrolyte on the electrochemical behavior of the modified electrode was studied. The peak potential and peak current vary with different alkali metal cations, but anions such as NO 3 - , Cl - , CH 3 COO - , H 2 PO 4 - / HPO 4 2 - and SO 4 2 - in 0.5 M concentration have no effect on the peak potential and peak current. The response of the modified electrode is not affected by pH within a range 1–10. The transfer coefficient ( α), charge transfer rate constant ( k s) and diffusion coefficient of different alkali metal cations in the ZnPCNF film were determined. Catalytic ability of the modified electrode for the oxidation of hydrazine on the electrode was demonstrated by cyclic voltammetry, rotating disk electrode (RDE) voltammetry, chronoamperometry and chronocoulometry.