Carbon Nanotube-modified Electrode Research Articles

Low-Potential Detection of Endogenous and Physiological Uric Acid at Uricase−Thionine−Single-Walled Carbon Nanotube Modified Electrodes

This work develops and validates an electrochemical approach for uric acid (UA) determinations in both endogenous (cell lysate) and physiological (serum) samples. This approach is based on the electrocatalytic reduction of enzymatically generated H(2)O(2) at the biosensor of uricase-thionine-single-walled carbon nanotube/glassy carbon (UOx-Th-SWNTs/GC) with the use of Th-SWNTs nanostructure as a mediator and an enzyme immobilization matrix. The biosensor, which was fabricated by immobilizing UOx on the surface of Th-SWNTs, exhibited a rapid response (ca. 2 s), a low detection limit (0.5 +/- 0.05 microM), a wide linear range (2 microM to 2 mM), high sensitivity (approximately 90 microA mM(-1) cm(-2)), as well as good stability and repeatability. In addition, the common interfering species, such as ascorbic acid, 3,4-dihydroxyphenylacetic acid, 4-acetamidophenol, etc., did not cause any interference due to the use of a low operating potential (-400 mV vs saturated calomel electrode). Therefore, this work has demonstrated a simple and effective sensing platform for selective detection of UA in the physiological levels. In particular, the developed approach could be very important and useful to determine the relative role of endogenous and physiological UA in various conditions such as hypertension and cardiovascular disease.

A metallacarborane redox mediator for an enzyme-immobilized chitosan-modified bioanode

We describe here the first report of a metallacarborane complex as a redox mediator in a functioning biofuel cell. Specifically, we have prepared a water-soluble salt of the complex anion [ commo-3,3′-Fe-( closo-2,1-C 2B 9H 11) 2] − and employed it as a redox mediator for glucose oxidation using chitosan/multiwalled carbon nanotube-modified electrodes comprising immobilized glucose oxidase. Experiments have indicated an increased amperometric response to glucose feeding, providing the complex mediator was initially supplied in the phosphate buffer electrolyte solution. Cathodic peak currents increased to a maximum of 1.24 mA/cm 2 up to the saturating threshold concentration of glucose, indicating a significant degree of metallacarborane-enzyme communication and supporting the notion of a proposed metallacarborane redox mediator in biofuel cells. Upon incorporation of the mediator by anion exchange in the chitosan with the enzyme prior to measurement, however, an attenuated response to glucose feeding was detected, despite efforts to use different tactics to cast such films on the electrode such as a bilayer scheme. It is believed that the uptake of significant quantities of the metallacarborane into the chitosan is sponsoring a gross change in the microstructure of the biopolymer. This is supported by SEM imaging of the metallacarborane-modified chitosan, which revealed a remarkable transformation of the biopolymer scaffold.

Fabrication of a Highly Sensitive Glucose Biosensor Based on Immobilization of Osmium Complex and Glucose Oxidase onto Carbon Nanotubes Modified Electrode

AbstractIn this research a novel osmium complex was used as electrocatalyst for electroreduction of oxygen and H2O2 in physiological pH solutions. Electroless deposition at a short period of time (60 s), was used for strong and irreversible adsorption of 1,4,8,12‐tetraazacyclotetradecane osmium(III) chloride (Os(III)LCl2) ClO4 onto single‐walled carbon nanotubes (SWCNTs) modified GC electrode. The modified electrode shows a pair of well defined and reversible redox couple, Os(IV)/Os(III) at wide pH range (1–8). The glucose biosensor was fabricated by covering a thin film of glucose oxidase onto CNTs/Os‐complex modified electrode. The biosensor can be used successfully for selective detection of glucose based on the decreasing of cathodic peak current of oxygen. The fabricated biosensor shows high sensitivity, 826.3 nA μM−1cm−2, low detection limit, 56 nM, fast response time <3 s and wide calibration range 1.0 μM–1.0 mM. The biosensor has been successfully applied to determination of glucose in human plasma. Because of relative low applied potential, the interference from electroactive existing species was minimized, which improved the selectivity of the biosensor. The apparent Michaelis‐Menten constant of GOx on the nanocomposite, 0.91 mM, exhibits excellent bioelectrocatalytic activity of immobilized enzyme toward glucose oxidation. Excellent electrochemical reversibility, high stability, technically simple and possibility of preparation at short period of time are of great advantages of this glucose biosensor.

Catalytic Current Based on Direct Electron Transfer Reactions of Enzymes Immobilized onto Carbon Nanotubes

Multi-walled and single-walled carbon nanotubes were synthesized on platinum plate (MWCNTs/pt) and gold wire (SWCNTs/Au) electrodes, respectively, using a chemical vapor deposition (CVD) method. These carbon nanotube-modified electrodes were immersed into solutions of glucose oxidase (GOX) and D-fructose dehydrogenase (FDH) to immobilize these enzymes onto the electrode surfaces. After GOX was immobilized onto the MWCNT/Pt electrode, the well-defined catalytic oxidation current was increased from ca. -0.45 V (vs. Ag/AgCl/saturated KCl), which was close to the redox potential of flavin adenine dinucleotide as a prosthetic group of GOX under physiological pH values. Furthermore, catalytic oxidation currents of fructose based on direct heterogeneous electron transfer reactions between FDH and the SWCNT/Pt electrode were observed.

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 oxalic acid in spinach with carbon nanotubes-modified electrode

This work investigated the electrocatalytic oxidation of oxalic acid on multiwall carbon nanotubes (MWNTs) modified glassy carbon (GC) electrode. The result indicated that the oxidation of oxalic acid was greatly improved at the MWNTs-modified GC (MWNTs/GC) electrode as compared with the bare GC electrode. The effects of the MWNTs suspension amount, pH and scan rate on the electrooxidation response of oxalic acid were studied by voltammetry. The surface concentration and diffusion coefficient ( D R ) of oxalic acid at the MWNTs/GC electrode were determined by chronocoulometry. This MWNTs/GC electrode presented a wide linear response ranging from 5.0 × 10 −5 to 1.5 × 10 −2 M for oxalic acid. The detection limit (S/N = 3) was estimated to be 1.20 × 10 −5 M. Based on this MWNTs/GC electrode, the content of oxalic acid in spinach was successfully determined.

Determination of zearalenone and its metabolites in urine samples by liquid chromatography with electrochemical detection using a carbon nanotube-modified electrode

A simple and sensitive method for the separation and determination of zearalenone (ZON) and its secondary metabolites, namely β-zearalenol (β-ZAL), β-zearalanol (β-ZOL), α-zearalenol (α-ZAL), α-zearalanol (α-ZOL) and zearalanone (ZAN) in urine (human, bovine and swine) samples is proposed. The method comprises previous clean-up and pre-concentration on C 18 adsorption cartridges of the analytes followed by liquid chromatographic separation and direct electrochemical detection at +0.85 mV using a carbon nanotube-modified glassy carbon electrode (CNT-GCE). This method allows the determination of β-ZAL, β-ZOL, α-ZAL, α-ZOL, ZAN and ZON in a linear range between 5 and 50 ng mL −1, with relative standard deviation values lower than 6.9% (intra-day) and 7.1% (inter-day), in all cases. Detection limits ranging between 1.3 ng mL −1 (β-ZOL, α-ZAL, α-ZOL) and 1.4 ng mL −1 (β-ZAL, ZAN, ZON) were achieved. The usefulness of the proposed method was demonstrated by the analysis of spiked and natural samples of human, bovine and swine urine samples.

A Mediator‐Free Bienzyme Amperometric Biosensor Based on Horseradish Peroxidase and Glucose Oxidase Immobilized on Carbon Nanotube Modified Electrode

AbstractMultiwalled carbon nanotube (CNT) modified glassy carbon electrode immobilized with horseradish peroxidase (HRP) in Nafion coating showed direct electron transfer between HRP enzyme and the CNT‐modified electrode. A mediator‐free bienzyme glucose biosensor based on horseradish peroxidase and glucose oxidase was constructed. The bienzyme biosensor exhibited a high sensitivity for glucose detection at zero applied potential.

Electrochemical properties of colchicine on the PoPD/SWNTs composite-modified glassy carbon electrode

Abstract A poly(o-phenylenediamine)/single-wall carbon nanotubes-modified electrode was prepared by electropolymerization on glassy carbon electrode. The morphology of the resulting PoPD/SWNTs composite was characterized by transmission electron microscopy (TEM) and the electrochemical properties of the modified electrode were characterized by cyclic voltammetry and ac impedance. The nanoporous composite film-modified glassy carbon electrode exhibits enhanced electrocatalytic behavior and good stability for the detection of colchicine. The large current response of colchicine on PoPD/SWNTs composite-modified electrode is probably caused by the synergistic effect of the electrocatalytic property of PoPD and SWNTs. The oxidative peak current increased linearly with the concentration of colchicine in the range of 1.0 × 10−7 to 1.0 × 10−5 mol l−1 by differential pulse voltammetry. The detection limit was 3.5 × 10−8 mol l−1. The proposed modified electrode provides a new promising and alternative way to detect colchicine.

Electrocatalytic Behavior of Glassy Carbon Electrodes Modified with Multiwalled Carbon Nanotubes and Cobalt Phthalocyanine for Selective Analysis of Dopamine in Presence of Ascorbic Acid

AbstractThis work describes the development, electrochemical characterization and utilization of a cobalt phthalocyanine modified carbon nanotube electrode for the quantitative determination of dopamine in 0.2 mol L−1 phosphate buffer contaminated with high concentration of ascorbic acid. The electrode surface was analyzed by cyclic voltammetry and electrochemical impedance spectroscopy which showed a modified surface presenting a charge transfer resistance of 500 Ω, against the 16.46 kΩ value found for the bare glassy carbon surface. A pseudo rate constant value of 5.4×10−4 cm s−1 for dopamine oxidation was calculated. Voltammetric experiments showed a shift of the peak potential of DA oxidation to less positive value at 390 mV as compared with that of a bare GC electrode at 570 mV. The electrochemical determination of dopamine, in presence of ascorbic acid in concentrations up to 0.1 mol L−1 by differential pulse voltammetry, yielded a detection limit as low as 2.56×10−7 mol L−1.

Electrochemical Determination of Trace Sudan I Contamination in Chili Powder at Carbon Nanotube Modified Electrodes.

We have developed a simple, convenient and inexpensive voltammetric method for determining trace Sudan I contamination in chili powder, based on the catalyzed electrochemical reduction of Sudan I at the carbon nanotube modified electrode. Under optimized conditions, the method exhibited acceptable analytical performance in terms of linearity (over the concentration range 6.0×10-7 to 7.5×10-5 M, r = 0.9967), detection limit (2.0×10-7 M) and reproducibility (RSD = 4.6%, n=10, for 2.0×10-5 M Sudan I).

Carbon nanotube-modified electrodes for solar energy conversion

Download options Please wait... Article information DOI https://doi.org/10.1039/B805419N Article type Perspective Submitted 31 Mar 2008 Accepted 19 May 2008 First published 17 Jun 2008 Download Citation Energy Environ. Sci., 2008,1, 120-133 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Carbon nanotube-modified electrodes for solar energy conversion T. Umeyama and H. Imahori, Energy Environ. Sci., 2008, 1, 120 DOI: 10.1039/B805419N To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Tomokazu Umeyama Hiroshi Imahori

The Electrochemical Behavior of Acetaminophen on Multi‐Walled Carbon Nanotubes Modified Electrode and Its Analytical Application

A multi‐walled carbon nanotubes modified glassy carbon electrode (MWNTs/GCE) was fabricated, and the electrochemical behaviors of acetaminophen (ACOP) were investigated on the MWNTs/GCE. The results showed that MWNTs exhibited excellent electrocatalytic effects on the reaction of ACOP by accelerating the electron transfer rate. Cyclic voltammetry (CV) was used to explore the electrochemical redox mechanism of ACOP on the MWNTs/GCE and differential pulse voltammetry (DPV) was taken to determine ACOP in samples, respectively. The results showed that the oxidative peak currents were linear with the concentration of ACOP in the range of 4.0×10−7–1.5×10−4 mol l−1 with the detection limit 1.2×10−7 mol l−1. The MWNTs/GCE showed satisfactory stability, selectivity, and it can be used to quantify ACOP in effervescent dosage real samples.

A Novel Functionalized Single‐Wall Carbon Nanotube Modified Electrode and Its Application in Determination of Dopamine and Uric Acid in the Presence of High Concentrations of Ascorbic Acid

AbstractMultilayer films of negatively charged single‐wall carbon nanotubes (SWCNTs) and positively charged cetylpyridinium bromide (CPB) have been deposited on a glassy carbon electrode (GCE) using layer‐by‐layer (LBL) technique. The assembled multilayer films have been investigated by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and quartz crystal microbalance (QCM) measurements. The voltammetric signal of dopamine (DA), uric acid (UA), and ascorbic acid (AA) could be observed well‐separated with the assembled SWCNTs/CPB multilayer films in pH 7.0 PBS. The oxidation peak potentials of DA, UA, and AA are centered at about 169 mV, 292 mV and −10 mV on differential pulse voltammograms (DPVs), respectively. The peak‐to‐peak potential separation was 123 mV, 179 mV, and 302 mV for DA‐UA, DA‐AA, and UA‐AA in DPVs, respectively. This permits the simultaneous detection of DA and UA in the presence of AA.

Direct electrochemistry and electrocatalysis of cytochrome c immobilized on gold nanoparticles–chitosan–carbon nanotubes-modified electrode

A robust and effective nanohybrid film based on gold nanoparticles (GNPs)/chitosan (Chit)/multi-walled carbon nanotubes (MWNTs) was prepared by a layer-by-layer self-assembly technique. Cytochrome c (Cyt c) was successfully immobilized on the nanohybrid film modified glassy carbon (GC) electrode by cyclic voltammetry. The direct electron transfer between Cyt c and the modified electrode was investigated in detail. Cyt c shows a couple of quasi-reversible and well-defined cyclic voltammetry peaks with a formal potential ( E 0′) of −0.16 V (versus Ag/AgCl) in pH 7.0 phosphate buffer solution (PBS). The Cyt c/GNPs/Chit/MWNTs modified GC electrode gives an improved electrocatalytic activity towards the reduction of hydrogen peroxide (H 2O 2). The sensitivity is 92.21 μA mM −1 cm −2 and the calculated apparent Michaelis–Menten constant ( K m app ) is 0.791 mM, indicating a high-catalytic activity of Cyt c. The catalysis currents increase linearly to the H 2O 2 concentration in a wide range of 1.5 × 10 −6 to 5.1 × 10 −4 M with a correlation coefficient 0.999. The detection limit is 9.0 × 10 −7 M (at the ratio of signal to noise, S/N = 3). Moreover, the modified electrode displays rapid response (5 s) to H 2O 2, and possesses good stability and reproducibility.

Highly sensitive choline biosensor based on carbon nanotube-modified Pt electrode combined with sol-gel immobilization

A novel amperometric choline biosensor has been fabricated with choline oxidase (ChOx) immobilized by the sol-gel method on the surface of multi-walled carbon nanotubes (MWCNT) modified platinum electrode to improve the sensitivity and the anti-interferential property of the sensor. By analyzing the electrocatalytic activity of the modified electrode by MWCNT, it was found that MWCNT could not only improve the current response to H2O2 but also decrease the electrocatalytic potential. The effects of experimental variables such as the buffer solutions, pH and the amount of loading enzyme were investigated for the optimum analytical performance. This sensor shows sensitive determination of choline with a linear range from 5.0 × 10−6 to 1.0 × 10−4 mol/L when the operating pH and potential are 7.2 and 0.15 V, respectively. The detection limit of choline was 5.0 × 10−7 mol/L. Selectivity for choline was 9.48 μA·(mmol/L)−1. The biosensor exhibits excellent anti-interferential property and good stability, retaining 85% of its original current value even after a month. It has been applied to the determination of choline in human serum.

Electrochemical Characteristics of Glucose Oxidase Adsorbed at Carbon Nanotubes Modified Electrode with Ionic Liquid as Binder

AbstractMultiwall carbon nanotubes (CNTs)‐modified electrode has been prepared by using ionic liquid (IL) as the binder. The as‐prepared CNTs‐IL composite modified electrode has good biocompatibility and is a suitable matrix to immobilize biomolecules. Glucose oxidase (GOx), containing flavin adenine dinucleotide as active site, stably adsorbed on modified electrode surface has resulted in the direct electron transfer. The electron transfer rate of 9.08 s−1 obtained is much higher than that of GOx adsorbed on the CNTs papers (1.7 s−1), and the process is more reversible with small redox peak separation of 23 mV. This may be due to the synergetic promotion of CNTs and IL to electron transfer of the protein, especially the IL as the binder, showing better electrochemical properties than that of chitosan and Nafion. Furthermore, GOx adsorbed at the modified electrode exhibits good stability and keeps good electrocatalytic activity to glucose with broad linear range up to 20 mM. Besides, the simple preparation procedure and easy renewability make the system a basis to investigate the electron transfer kinetics and biocatalytic performance of GOx and provide a promising platform for the development of biosensors.

Iron Oxide Particles Are the Active Sites for Hydrogen Peroxide Sensing at Multiwalled Carbon Nanotube Modified Electrodes

We demonstrate that the "electrocatalytic" hydrogen peroxide detection reported at multiwalled carbon nanotube modified electrodes is due to iron oxide particles arising from the chemical vapor deposition nanotube fabrication process rather than due to intrinsic catalysis attributable to the carbon nanotubes arising, for example, from edge plane-like sites/defects.

Electrochemical detection of phenolic estrogenic compounds at carbon nanotube-modified electrodes

The use of a carbon nanotube-modified glassy carbon electrode (CNT-GCE) for the LC–EC detection of phenolic compounds with estrogenic activity is reported. Cyclic voltammograms for phenolic endocrine disruptors and estrogenic hormones showed, in general, an enhancement of their electrochemical oxidation responses at CNT-GCE attributable to the electrocatalytic effect caused by CNTs. Hydrodynamic voltammograms obtained under flow injection conditions lead to the selection of +700 mV as the potential value to be applied for the amperometric detection of the phenolic estrogenic compounds, this value being remarkably less positive than those reported in the literature using other electrode materials. Successive injections of these compounds demonstrated that no electrode surface fouling occurred. A mobile phase consisting of a 50:50 (v/v) acetonitrile:0.05 mol l −1 phosphate buffer of pH 7.0 was selected for the chromatographic separation of mixtures of these compounds, with detection limits ranging between 98 and 340 nmol l −1. Good recoveries were obtained in the analysis of underground well water and tap water samples spiked with some phenolic estrogenic compounds at a 14 nmol l −1 concentration level.

Electrochemical Behavior of MCF‐7 Cells on Carbon Nanotube Modified Electrode and Application in Evaluating the Effect of 5‐Fluorouracil

AbstractThe electrochemical behavior of human breast cancer cells (MCF‐7) suspension on multiwalled carbon nanotube (MWCNT) modified graphite electrode was studied by using cyclic voltammetry (CV) and potentiometric stripping analysis (PSA). Compared with bare graphite electrode, the MWCNTs‐modified electrode showed electrocatalytic property to the oxidation of electroactive species in the cell suspension. One oxidative peak at about +0.74 V was observed in the cyclic voltammogram. PSA was proved to be more sensitive than CV for investigation of the electrochemical behavior of cells. And it was found that ultrasonication treatment of the cell suspension can significantly enhance the PSA signal. Factors influencing the PSA signal of cells, including deposition time, deposition potential and stripping current, were investigated in detail and the optimum conditions were obtained. The baseline corrected PSA signal was found to be related to the viability of cells and the technique was used for monitoring the growth of MCF‐7 cells. The effect of anticancer drug 5‐fluorouracil (5‐FU) on the growth of MCF‐7 cells was also investigated by PSA.