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Sample records for nanotubes modified glassy

  1. Electrical properties of carbon nanotubes modified GaSe glassy system

    Science.gov (United States)

    Khan, Hana; Khan, Zubair M. S. H.; Islam, Shama; Rahman, Raja Saifu; Husain, M.; Zulfequar, M.

    2018-05-01

    In this paper we report the investigation of the effect of Carbon Nanotubes (CNT) addition on the electrical properties of GaSe Glassy system. Dielectric constant and dielectric loss of GaSe glassy system are found to increase on CNT addition. The conductivity of GaSe glasy systems is also found to increase on CNT addition. This behavior is attributed to the excellent conduction properties of Carbon Nanotube.

  2. Electrochemical parameters of ethamsylate at multi-walled carbon nanotube modified glassy carbon electrodes.

    Science.gov (United States)

    Wang, Sheng-Fu; Xu, Qiao

    2007-05-01

    In this paper, some electrochemical parameters of ethamsylate at a multi-walled carbon nanotube modified glassy carbon electrode, such as the charge number, exchange current density, standard heterogeneous rate constant and diffusion coefficient, were measured by cyclic voltammetry, chronoamperometry and chronocoulometry. The modified electrode exhibits good promotion of the electrochemical reaction of ethamsylate and increases the standard heterogeneous rate constant of ethamsylate greatly. The differential pulse voltammetry responses of ethamsylate were linearly dependent on its concentrations in a range from 2.0 x 10(-6) to 6.0 x 10(-5) mol L(-1), with a detection limit of 4.0 x 10(-7) mol L(-1).

  3. Electrochemical Determination of Glycoalkaloids Using a Carbon Nanotubes-Phenylboronic Acid Modified Glassy Carbon Electrode

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    Huiying Wang

    2013-11-01

    Full Text Available A versatile strategy for electrochemical determination of glycoalkaloids (GAs was developed by using a carbon nanotubes-phenylboronic acid (CNTs-PBA modified glassy carbon electrode. PBA reacts with α-solanine and α-chaconine to form a cyclic ester, which could be utilized to detect GAs. This method allowed GA detection from 1 μM to 28 μM and the detection limit was 0.3 μM. Affinity interaction of GAs and immobilized PBA caused an essential change of the peak current. The CNT-PBA modified electrodes were sensitive for detection of GAs, and the peak current values were in quite good agreement with those measured by the sensors.

  4. Biosensor based on a glassy carbon electrode modified with tyrosinase immobilized on multiwalled carbon nanotubes

    International Nuclear Information System (INIS)

    Ren, J.; Kang, T.F.; Xue, R.; Ge, C.N.; Cheng, S.Y.

    2011-01-01

    We describe a biosensor for phenolic compounds that is based on a glassy carbon electrode modified with tyrosinase immobilized on multiwalled carbon nanotubes (MWNTs). The MWNTs possess excellent inherent electrical conductivity which enhances the electron transfer rate and results in good electrochemical catalytic activity towards the reduction of benzoquinone produced by enzymatic reaction. The biosensor was characterized by cyclic voltammetry, and the experimental conditions were optimized. The cathodic current is linearly related to the concentration of the phenols between 0.4 μM and 10 μM, and the detection limit is 0.2 μM. The method was applied to the determination of phenol in water samples (author)

  5. Hematoxylin multi-wall carbon nanotubes modified glassy carbon electrode for electrocatalytic oxidation of hydrazine

    International Nuclear Information System (INIS)

    Zare, Hamid R.; Nasirizadeh, Navid

    2007-01-01

    A new hydrazine sensor has been fabricated by immobilizing hematoxylin at the surface of a glassy carbon electrode (GCE) modified with multi-wall carbon nanotube (MWCNT). The adsorbed thin films of hematoxylin on the MWCNT modified GCE show one pair of peaks with surface confined characteristics. The hematoxylin MWCNT (HMWCNT) modified GCE shows highly catalytic activity toward hydrazine electro-oxidation. The results show that the peak potential of hydrazine at HMWCNT modified GCE surface shifted by about 167 and 255 mV toward negative values compared with that at an MWCNT and activated modified GCE surface, respectively. In addition, at HMWCNT modified electrode surface remarkably improvement the sensitivity of determination of hydrazine. The kinetic parameters, such as the electron transfer coefficient, α, and the standard heterogeneous rate constant, k 0 , for oxidation of hydrazine at the HMWCNT modified GCE were determined and also is shown that the heterogeneous rate constant, k', is strongly potential dependent. The overall number of electron involved in the catalytic oxidation of hydrazine and the number of electrons involved in the rate-determining steps are 2 and 1, respectively. The amperometric detection of hydrazine is carried out at 220 mV in 0.1 M phosphate buffer solution (pH 7) with linear response range 2.0-122.8 μM hydrazine, detection limit of 0.68 μM and sensitivity of 0.0208 μA μM -1 . Finally the amperometric response for hydrazine determination is reproducible, fast and extremely stable, with no loss in sensitivity over a continual 400 s operation

  6. Electrocatalytic oxidation of deferiprone and its determination on a carbon nanotube-modified glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Yadegari, H. [Department of Chemistry, Faculty of Science, K.N. Toosi University of Technology, P.O. Box 16315-1618, Tehran (Iran, Islamic Republic of); Jabbari, A. [Department of Chemistry, Faculty of Science, K.N. Toosi University of Technology, P.O. Box 16315-1618, Tehran (Iran, Islamic Republic of)], E-mail: jabbari@kntu.ac.ir; Heli, H.; Moosavi-Movahedi, A.A. [Institute of Biochemistry and Biophysics, University of Tehran, Tehran (Iran, Islamic Republic of); Karimian, K. [Arasto Pharmaceutical Chemicals Inc., Tehran (Iran, Islamic Republic of); Khodadadi, A. [Department of Chemical Engineering, Faculty of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of)

    2008-02-15

    The electrochemical behavior of the anti-thalassemia and anti-HIV replication drug, deferiprone, was investigated on a carbon nanotube-modified glassy carbon (GC-CNT) electrode in phosphate buffer solution, pH 7.40 (PBS). During oxidation of deferiprone, two irreversible anodic peaks, with E{sub 1}{sup 0}=452 and E{sub 2}{sup 0}=906mV, appeared, using GC-CNT. Cyclic voltammetric study indicated that the oxidation process is irreversible and diffusion controlled. The number of exchanged electrons in the electro-oxidation process was obtained, and the data indicated that deferiprone is oxidized via two two-electron steps. The results revealed that carbon nanotube (CNT) promotes the rate of oxidation by increasing the peak current, so that deferiprone is oxidized at lower potentials, which thermodynamically is more favorable. This result was confirmed by impedance measurements. The diffusion coefficient, electron-transfer coefficient and heterogeneous electron-transfer rate constant of deferiprone were found to be 1.49 x 10{sup -6} cm{sup 2} s{sup -1}, 0.44, and 3.83 x 10{sup -3} cm s{sup -1}, respectively. A sensitive, simple and time-saving differential-pulse voltammetric procedure was developed for the analysis of deferiprone. Using the proposed method, deferiprone can be determined with a detection limit of 5.25 x 10{sup -7} M. The applicability of the method to direct assays of spiked human serum and urine fluids is described.

  7. Electrocatalysis of oxygen reduction on nitrogen-containing multi-walled carbon nanotube modified glassy carbon electrodes

    International Nuclear Information System (INIS)

    Vikkisk, Merilin; Kruusenberg, Ivar; Joost, Urmas; Shulga, Eugene; Tammeveski, Kaido

    2013-01-01

    Highlights: ► Pyrolysis in the presence of urea was used for nitrogen doping of carbon nanotubes. ► N-doped carbon nanotubes were used as catalysts for the oxygen reduction reaction. ► N-doped carbon material showed a high catalytic activity for ORR in alkaline media. ► N-containing CNT material is an attractive cathode catalyst for alkaline membrane fuel cells. - Abstract: The electrochemical reduction of oxygen was studied on nitrogen-doped multi-walled carbon nanotube (NCNT) modified glassy carbon (GC) electrodes employing the rotating disk electrode (RDE) method. Nitrogen doping was achieved by simple pyrolysis of the carbon nanotube material in the presence of urea. The surface morphology and composition of the NCNT samples were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The SEM images revealed a rather uniform distribution of NCNTs on the GC electrode substrate. The XPS analysis showed a successful doping of carbon nanotubes with nitrogen species. The RDE results revealed that in alkaline solution the N-doped nanotube materials showed a remarkable electrocatalytic activity towards oxygen reduction. At low overpotentials the reduction of oxygen followed a two-electron pathway on undoped carbon nanotube modified GC electrodes, whereas on NCNT/GC electrodes a four-electron pathway of O 2 reduction predominated. The results obtained are significant for the development of nitrogen-doped carbon-based cathodes for alkaline membrane fuel cells.

  8. Electrochemical Reduction of Oxygen on Anthraquinone/Carbon Nanotubes Nanohybrid Modified Glassy Carbon Electrode in Neutral Medium

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    Zheng Gong

    2013-01-01

    Full Text Available The electrochemical behaviors of monohydroxy-anthraquinone/multiwall carbon nanotubes (MHAQ/MWCNTs nanohybrid modified glassy carbon (MHAQ/MWCNTs/GC electrodes in neutral medium were investigated; also reported was their application in the electrocatalysis of oxygen reduction reaction (ORR. The resulting MHAQ/MWCNTs nanohybrid was characterized by scanning electron microscope (SEM and transmission electron microscope (TEM. It was found that the ORR at the MHAQ/MWCNTs/GC electrode occurs irreversibly at a potential about 214 mV less negative than at a bare GC electrode in pH 7.0 buffer solution. Cyclic voltammetric and rotating disk electrode (RDE techniques indicated that the MHAQ/MWCNTs nanohybrid has high electrocatalytic activity for the two-electron reduction of oxygen in the studied potential range. The kinetic parameters of ORR at the MHAQ/MWCNTs nanohybrid modified GC electrode were also determined by RDE and EIS techniques.

  9. Glassy carbon electrodes modified with multiwalled carbon nanotubes for the determination of ascorbic acid by square-wave voltammetry

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    Sushil Kumar

    2012-05-01

    Full Text Available Multiwalled carbon nanotubes were used to modify the surface of a glassy carbon electrode to enhance its electroactivity. Nafion served to immobilise the carbon nanotubes on the electrode surface. The modified electrode was used to develop an analytical method for the analysis of ascorbic acid (AA by square-wave voltammetry (SWV. The oxidation of ascorbic acid at the modified glassy carbon electrode showed a peak potential at 315 mV, about 80 mV lower than that observed at the bare (unmodified electrode. The peak current was about threefold higher than the response at the bare electrode. Replicate measurements of peak currents showed good precision (3% rsd. Peak currents increased with increasing ascorbic acid concentration (dynamic range = 0.0047–5.0 mmol/L and displayed good linearity (R2 = 0.994. The limit of detection was 1.4 μmol/L AA, while the limit of quantitation was 4.7 μmol/L AA. The modified electrode was applied to the determination of the amount of ascorbic acid in four brands of commercial orange-juice products. The measured content agreed well (96–104% with the product label claim for all brands tested. Recovery tests on spiked samples of orange juice showed good recovery (99–104%. The reliability of the SWV method was validated by conducting parallel experiments based on high-performance liquid chromatography (HPLC with absorbance detection. The observed mean AA contents of the commercial orange juice samples obtained by the two methods were compared statistically and were found to have no significant difference (P = 0.05.

  10. Ubiquinol-cytochrome c reductase (Complex III) electrochemistry at multi-walled carbon nanotubes/Nafion modified glassy carbon electrodes

    International Nuclear Information System (INIS)

    Pelster, Lindsey N.; Minteer, Shelley D.

    2012-01-01

    Highlights: ► The electron transport chain is important to the understanding of metabolism in the living cell. ► Ubiquinol-cytochrome c reductase is a membrane bound complex of the electron transport chain (Complex III). ► The paper details the first bioelectrochemical characterization of ubiquinol-cytochrome c reductase at an electrode. - Abstract: Electron transport chain complexes are critical to metabolism in living cells. Ubiquinol-cytochrome c reductase (Complex III) is responsible for carrying electrons from ubiquinol to cytochrome c, but the complex has not been evaluated electrochemically. This work details the bioelectrochemistry of ubiquinol-cytochrome c reductase of the electron transport chain of tuber mitochondria. The characterization of the electrochemistry of this enzyme is investigated in carboxylated multi-walled carbon nanotube/tetrabutyl ammonium bromide-modified Nafion ® modified glassy carbon electrodes by cyclic voltammetry. Increasing concentrations of cytochrome c result in a catalytic response from the active enzyme in the nanotube sandwich. The experiments show that the enzyme followed Michaelis–Menten kinetics with a K m for the immobilized enzyme of 2.97 (±0.11) × 10 −6 M and a V max of 6.31 (±0.82) × 10 −3 μmol min −1 at the electrode, but the K m and V max values decreased compared to the free enzyme in solution, which is expected for immobilized redox proteins. This is the first evidence of ubiquinol-cytochrome c reductase bioelectrocatalysis.

  11. Gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode as a sensitive voltammetric sensor for the determination of diclofenac sodium.

    Science.gov (United States)

    Afkhami, Abbas; Bahiraei, Atousa; Madrakian, Tayyebeh

    2016-02-01

    A simple and highly sensitive sensor for the determination of diclofenac sodium based on gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode is reported. Scanning electron microscopy along with energy dispersive X-ray spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry and square wave voltammetry was used to characterize the nanostructure and performance of the sensor and the results were compared with those obtained at the multi-walled carbon nanotube modified glassy carbon electrode and bare glassy carbon electrode. Under the optimized experimental conditions diclofenac sodium gave linear response over the range of 0.03-200μmolL(-1). The lower detection limits were found to be 0.02μmolL(-1). The effect of common interferences on the current response of DS was investigated. The practical application of the modified electrode was demonstrated by measuring the concentration of diclofenac sodium in urine and pharmaceutical samples. This revealed that the gold nanoparticle/multiwalled carbon nanotube modified glassy carbon electrode shows excellent analytical performance for the determination of diclofenac sodium in terms of a very low detection limit, high sensitivity, very good accuracy, repeatability and reproducibility. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. Electrocatalytic Study of Paracetamol at a Single-Walled Carbon Nanotube/Nickel Nanocomposite Modified Glassy Carbon Electrode

    Directory of Open Access Journals (Sweden)

    Koh Sing Ngai

    2015-01-01

    Full Text Available A rapid, simple, and sensitive method for the electrochemical determination of paracetamol was developed. A single-walled carbon nanotube/nickel (SWCNT/Ni nanocomposite was prepared and immobilized on a glassy carbon electrode (GCE surface via mechanical attachment. This paper reports the voltammetry study on the effect of paracetamol concentration, scan rate, pH, and temperature at a SWCNT/Ni-modified electrode in the determination of paracetamol. The characterization of the SWCNT/Ni/GCE was performed by cyclic voltammetry. Variable pressure scanning electron microscopy (VPSEM and energy dispersive X-ray (EDX spectrometer were used to examine the surface morphology and elemental profile of the modified electrode, respectively. Cyclic voltammetry showed significant enhancement in peak current for the determination of paracetamol at the SWCNT/Ni-modified electrode. A linear calibration curve was obtained for the paracetamol concentration between 0.05 and 0.50 mM. The SWCNT/Ni/GCE displayed a sensitivity of 64 mA M−1 and a detection limit of 1.17 × 10−7 M in paracetamol detection. The proposed electrode can be applied for the determination of paracetamol in real pharmaceutical samples with satisfactory performance. Results indicate that electrodes modified with SWCNT and nickel nanoparticles exhibit better electrocatalytic activity towards paracetamol.

  13. mwnts composite film modified glassy carbon electrode

    African Journals Online (AJOL)

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    ABSTRACT: A poly p-aminosalicylic acid (Poly(p-ASA)) and multiwall carbon nanotubes. (MWCNTs) composite modified glassy carbon (GC) electrode was constructed by casting the MWNTs on the GC electrode surface followed by electropolymerization of the p-ASA on the MWCNTs/GCE. The electrochemical behaviours ...

  14. Glassy carbon electrode modified with multi-walled carbon nanotubes sensor for the quantification of antihistamine drug pheniramine in solubilized systems

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    Rajeev Jain

    2012-02-01

    Full Text Available A sensitive electroanalytical method for quantification of pheniramine in pharmaceutical formulation has been investigated on the basis of the enhanced electrochemical response at glassy carbon electrode modified with multi-walled carbon nanotubes in the presence of sodium lauryl sulfate. The experimental results suggest that the pheniramine in anionic surfactant solution exhibits electrocatalytic effect resulting in a marked enhancement of the peak current response. Peak current response is linearly dependent on the concentration of pheniramine in the range 200–1500 μg/mL with correlation coefficient 0.9987. The limit of detection is 58.31 μg/mL. The modified electrode shows good sensitivity and repeatability. Keywords: Pheniramine, Sodium lauryl sulfate (SLS, Glassy carbon electrode modified with multi-walled carbon nanotubes (GCE-MWCNTs, Solubilized systems, Voltammetric quantification

  15. Gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode as a sensitive voltammetric sensor for the determination of diclofenac sodium

    International Nuclear Information System (INIS)

    Afkhami, Abbas; Bahiraei, Atousa; Madrakian, Tayyebeh

    2016-01-01

    A simple and highly sensitive sensor for the determination of diclofenac sodium based on gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode is reported. Scanning electron microscopy along with energy dispersive X-ray spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry and square wave voltammetry was used to characterize the nanostructure and performance of the sensor and the results were compared with those obtained at the multi-walled carbon nanotube modified glassy carbon electrode and bare glassy carbon electrode. Under the optimized experimental conditions diclofenac sodium gave linear response over the range of 0.03–200 μmol L −1 . The lower detection limits were found to be 0.02 μmol L −1 . The effect of common interferences on the current response of DS was investigated. The practical application of the modified electrode was demonstrated by measuring the concentration of diclofenac sodium in urine and pharmaceutical samples. This revealed that the gold nanoparticle/multiwalled carbon nanotube modified glassy carbon electrode shows excellent analytical performance for the determination of diclofenac sodium in terms of a very low detection limit, high sensitivity, very good accuracy, repeatability and reproducibility. - Highlights: • GCE was modified with multiwalled carbon nanotube and gold nanoparticles. • AuNP/MWCNT/GCE was used for the determination of diclofenac sodium. • Modified electrode was characterized by SEM, EDS and EIS. • The proposed method showed excellent analytical figures of merit. • This sensor was used for the determination of diclofenac sodium in real samples.

  16. Gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode as a sensitive voltammetric sensor for the determination of diclofenac sodium

    Energy Technology Data Exchange (ETDEWEB)

    Afkhami, Abbas, E-mail: afkhami@basu.ac.ir; Bahiraei, Atousa; Madrakian, Tayyebeh

    2016-02-01

    A simple and highly sensitive sensor for the determination of diclofenac sodium based on gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode is reported. Scanning electron microscopy along with energy dispersive X-ray spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry and square wave voltammetry was used to characterize the nanostructure and performance of the sensor and the results were compared with those obtained at the multi-walled carbon nanotube modified glassy carbon electrode and bare glassy carbon electrode. Under the optimized experimental conditions diclofenac sodium gave linear response over the range of 0.03–200 μmol L{sup −1}. The lower detection limits were found to be 0.02 μmol L{sup −1}. The effect of common interferences on the current response of DS was investigated. The practical application of the modified electrode was demonstrated by measuring the concentration of diclofenac sodium in urine and pharmaceutical samples. This revealed that the gold nanoparticle/multiwalled carbon nanotube modified glassy carbon electrode shows excellent analytical performance for the determination of diclofenac sodium in terms of a very low detection limit, high sensitivity, very good accuracy, repeatability and reproducibility. - Highlights: • GCE was modified with multiwalled carbon nanotube and gold nanoparticles. • AuNP/MWCNT/GCE was used for the determination of diclofenac sodium. • Modified electrode was characterized by SEM, EDS and EIS. • The proposed method showed excellent analytical figures of merit. • This sensor was used for the determination of diclofenac sodium in real samples.

  17. Amperometric sensing of anti-HIV drug zidovudine on Ag nanofilm-multiwalled carbon nanotubes modified glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Rafati, Amir Abbas, E-mail: aa_rafati@basu.ac.ir; Afraz, Ahmadreza

    2014-06-01

    The zidovudine (ZDV) is the first drug approved for the treatment of HIV virus infection. The detection and determination of this drug are very importance in human serum because of its undesirable effects. A new ZDV sensor was fabricated on the basis of nanocomposite of silver nanofilm (Ag-NF) and multiwalled carbon nanotubes (MWCNTs) immobilized on glassy carbon electrode (GCE). The modified electrodes were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), cyclic voltammetry (CV), and linear sweep voltammetry (LSV) techniques. Results showed that the electrodeposited silver has a nanofilm structure and further electrochemical studies showed that the prepared nanocomposite has high electrocatalytic activity and is appropriate for using in sensors. The amperometric technique under optimal conditions is used for the determination of ZDV ranging from 0.1 to 400 ppm (0.37 μM–1.5 mM) with a low detection limit of 0.04 ppm (0.15 μM) (S/N = 3) and good sensitivity. The prepared sensor possessed accurate and rapid response to ZDV and shows an average recovery of 98.6% in real samples. - Highlights: • New anti-HIV drug sensor was fabricated on the basis of nanomaterials composite. • The GCE modified by prepared hydrophilic MWCNT silver nanoparticles. • Silver nanofilm electrodeposited on MWCNT/GCE and characterized by SEM, EDX, CV and LSV • Response of electrode to ZDV was thoroughly investigated by electrochemical techniques.

  18. A glassy carbon electrode modified with cerium phosphate nanotubes for the simultaneous determination of hydroquinone, catechol and resorcinol.

    Science.gov (United States)

    Li, Zhen; Yue, Yuhua; Hao, Yanjun; Feng, Shun; Zhou, Xianli

    2018-03-12

    A nafion film containing cerium phosphate nanotubes was pasted onto a glassy carbon electrode (GCE) to obtain a sensor for hydroquinone (HQ). The morphologies and components of the coating were characterized by transmission electron microscopy, scanning electron microscopy and energy-dispersive spectroscopy. Cyclic voltammetry and differential pulse voltammetry (DPV) showed the specific surface of the electrode to be significantly increased and the electron transfer rate to be accelerated. The modified GCE was applied to the determination of hydroquinone (HQ) via DPV. The oxidation current increases linearly in the 0.23 μM to 16 mM HQ concentration range which is as wide as five orders of magnitude. The limit of detection is 0.12 μM (based on a signal-to-noise ratio of 3), and the sensitivity is 1.41 μA·μM -1  cm -2 . The method was further applied to the simultaneous determination of HQ, catechol and resorcinol. The potentials for the three species are well separated (20, 134, and 572 mV vs SCE). Average recoveries from (spiked) real water samples are between 95.2 and 107.0%, with relative standard deviations of 0.9~2.7% (for n = 3) at three spiking levels. The method was validated by independent assays using HPLC. Graphical abstract ᅟ.

  19. An amperometric hydrogen peroxide biosensor based on Co3O4 nanoparticles and multiwalled carbon nanotube modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Kaçar, Ceren; Dalkiran, Berna; Erden, Pınar Esra; Kiliç, Esma

    2014-01-01

    Highlights: • Hydrogen peroxide biosensor was constructed by combining the advantageous properties of MWCNTs and Co 3 O 4 . • Incorporating Co 3 O 4 nanoparticles into MWCNTs/gelatin film increased the electron transfer. • Co 3 O 4 /MWCNTs/gelatin/HRP/Nafion/GCE showed strong anti-interference ability. • Hydrogen peroxide was successfully determined in disinfector with an average recovery of 100.78 ± 0.89. - Abstract: In this work a new type of hydrogen peroxide biosensor was fabricated based on the immobilization of horseradish peroxidase (HRP) by cross-linking on a glassy carbon electrode (GCE) modified with Co 3 O 4 nanoparticles, multiwall carbon nanotubes (MWCNTs) and gelatin. The introduction of MWCNTs and Co 3 O 4 nanoparticles not only enhanced the surface area of the modified electrode for enzyme immobilization but also facilitated the electron transfer rate, resulting in a high sensitivity of the biosensor. The fabrication process of the sensing surface was characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Amperometric detection of hydrogen peroxide was investigated by holding the modified electrode at −0.30 V (vs. Ag/AgCl). The biosensor showed optimum response within 5 s at pH 7.0. The optimized biosensor showed linear response range of 7.4 × 10 −7 –1.9 × 10 −5 M with a detection limit of 7.4 × 10 −7 . The applicability of the purposed biosensor was tested by detecting hydrogen peroxide in disinfector samples. The average recovery was calculated as 100.78 ± 0.89

  20. Glucose biosensor based on a glassy carbon electrode modified with polythionine and multiwalled carbon nanotubes.

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    Wenwei Tang

    Full Text Available A novel glucose biosensor was fabricated. The first layer of the biosensor was polythionine, which was formed by the electrochemical polymerisation of the thionine monomer on a glassy carbon electrode. The remaining layers were coated with chitosan-MWCNTs, GOx, and the chitosan-PTFE film in sequence. The MWCNTs embedded in FAD were like "conductive wires" connecting FAD with electrode, reduced the distance between them and were propitious to fast direct electron transfer. Combining with good electrical conductivity of PTH and MWCNTs, the current response was enlarged. The sensor was a parallel multi-component reaction system (PMRS and excellent electrocatalytic performance for glucose could be obtained without a mediator. The glucose sensor had a working voltage of -0.42 V, an optimum working temperature of 25°C, an optimum working pH of 7.0, and the best percentage of polytetrafluoroethylene emulsion (PTFE in the outer composite film was 2%. Under the optimised conditions, the biosensor displayed a high sensitivity of 2.80 µA mM(-1 cm(-2 and a low detection limit of 5 µM (S/N = 3, with a response time of less than 15 s and a linear range of 0.04 mM to 2.5 mM. Furthermore, the fabricated biosensor had a good selectivity, reproducibility, and long-term stability, indicating that the novel CTS+PTFE/GOx/MWCNTs/PTH composite is a promising material for immobilization of biomolecules and fabrication of third generation biosensors.

  1. Electrocatalytic reduction of dioxygen by cobalt porphyrin-modified glassy carbon electrode with single-walled carbon nanotubes and nafion in aqueous solutions

    International Nuclear Information System (INIS)

    Choi, Ayoung; Jeong, Haesang; Kim, Songmi; Jo, Suhee; Jeon, Seungwon

    2008-01-01

    Cobalt porphyrin (CoP)-modified glassy carbon electrode (GCE) with single-walled carbon nanotubes (SWNTs) and Nafion demonstrated a higher electrocatalytic activity for the reduction of dioxygen in 0.1 M H 2 SO 4 solution. Cyclic and hydrodynamic voltammetry at the CoP-SWNTs/GCE-modified electrodes in O 2 -saturated aqueous solutions was used to study the electrocatalytic pathway. Compared with the CoP/GCE-modified electrodes, the reduction potential of dioxygen at the CoP-SWNTs/GCE-modified electrodes was shifted to the positive direction and the limiting current was greatly increased. Especially, the Co(TMPP)-SWNTs/GCE-modified electrode was catalyzed effectively by the 4e - reduction of dioxygen to water, because hydrodynamic voltammetry revealed the transference of approximately four electrons for dioxygen reduction and the minimal generation of hydrogen peroxide in the process of dioxygen reduction

  2. Electrochemical Detection of Mn(II and Cd(II Mediated by Carbon Nanotubes and Carbon Nanotubes/Li+ Modified Glassy Carbon Electrode

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    Muhammed M. Radhi

    2010-11-01

    Full Text Available Glassy carbon electrode (GCE was modified with carbon nanotubes (CNT with and without a Li+ dopant by using a mechanical attachment method; CNT/Li+/GCE was used as two working electrodes, by doping CNT/GCE with Li+. The nano-structure of the electrodes showed individual voltammetrics of Mn2+ with two reduction peaks at +800 and +100 mV. Two reduction peaks for Cd2+ appeared at +600 V and -800 mV with one oxidation peak at -600 mV. The reduction current of Mn2+ and the redox current of Cd2+ on the CNT/Li+/GCE were largely influenced by a low concentration comparison with GCE and CNT/GCE. It showed that the detection of Mn2+ and Cd2+ by CNT/Li+/GCE in an aqueous solution of 0.1M KCL, with a relative standard deviation (RSD of the electrode being very good CNT/Li+/GCE. The determination of efficiency for the best modified electrode was detected for Mn2+ and Cd2+ on CNT/Li+/GCE; it was also found to have a wide linear range and good repeatability with a relative standard deviation (RSD of ±1.9 % when this electrode was used and the limit of detection was found to be 10-4 to 10-3 mM of Mn2+ and 10-4 to 10-2 mM of Cd2+, while the range of detection was found to be 3x10-4 to 10-3 mM and 10-3 to 10 -2 mM when using the CNT/GCE for Mn2+and Cd2+, respectively, with an RSD of ±3.3 % for Mn2+ and Cd2+.

  3. Amperometric nitrite sensor based on a glassy carbon electrode modified with multi-walled carbon nanotubes and poly(toluidine blue)

    International Nuclear Information System (INIS)

    Dai, Juan; Deng, Fei; He, Shuang; Deng, Dongli; Yuan, Yali; Zhang, Jinzhong

    2016-01-01

    An amperometric nitrite sensor modified with multi-walled carbon nanotubes (MWCNTs) and poly(toluidine blue) (PTB) on glassy carbon electrode was constructed. The surface morphology of the composite- modified electrode was characterized by scanning electron microscopy, and the electrochemical response behavior and electrocatalytic oxidation mechanism of nitrite were investigated by cyclic voltammetry. The high surface-to-volume ratio of MWCNTs and PTB brings the electrochemical sensing unit and nitrite in full contact. This renders the electrochemical response extremely sensitive to nitrite. Under the optimal measurement conditions and a working voltage of 0.73 V (vs. SCE), a linear relationship is obtained between the oxidation peak current and nitrite concentration in the range of 39 nM–1.1 mM, and the limit of detection is lowered to 19 nM (at an S/N ratio of 3). The sensor was successfully applied to the determination of nitrite in greenhouse soils. (author)

  4. Glassy carbon electrode modified with multi-walled carbon nanotubes sensor for the quantification of antihistamine drug pheniramine in solubilized systems.

    Science.gov (United States)

    Jain, Rajeev; Sharma, Sanjay

    2012-02-01

    A sensitive electroanalytical method for quantification of pheniramine in pharmaceutical formulation has been investigated on the basis of the enhanced electrochemical response at glassy carbon electrode modified with multi-walled carbon nanotubes in the presence of sodium lauryl sulfate. The experimental results suggest that the pheniramine in anionic surfactant solution exhibits electrocatalytic effect resulting in a marked enhancement of the peak current response. Peak current response is linearly dependent on the concentration of pheniramine in the range 200-1500 μg/mL with correlation coefficient 0.9987. The limit of detection is 58.31 μg/mL. The modified electrode shows good sensitivity and repeatability.

  5. Highly selective determination of dopamine in the presence of ascorbic acid and serotonin at glassy carbon electrodes modified with carbon nanotubes dispersed in polyethylenimine.

    Science.gov (United States)

    Rodríguez, Marcela C; Rubianes, María D; Rivas, Gustavo A

    2008-11-01

    We report the highly selective and sensitive voltammetric dopamine quantification in the presence of ascorbic acid and serotonin by using glassy carbon electrodes modified with a dispersion of multi-wall carbon nanotubes (MWCNT) in polyethylenimine, PEI (GCE/MWCNT-PEI). The electrocatalytic activity of the MWCNT deposited on the glassy carbon electrode has allowed an important decrease in the overvoltages for the oxidation of ascorbic acid and dopamine, making possible a clear definition of dopamine, serotonin and ascorbic acid oxidation processes. The sensitivities for dopamine in the presence and absence of 1.0 mM ascorbic acid and serotonin were (2.18 +/- 0.03) x 10(5) microAM(-1) (r = 0.9998); and (2.10 +/- 0.07) x 10(5) miroAM(-1) (r=0.9985), respectively, demonstrating the excellent performance of the GCE/MWCNT-PEI. The detection limit for dopamine in the mixture was 9.2 x 10(-7) M. The R. S. D. for the determination of 50 microM dopamine using four different electrodes was 3.9% when modified with the same MWCNT/PEI dispersion, and 4.6% when using four different dispersions. The modified electrode has been successfully applied for recovery assays of dopamine in human blood serum. Therefore, the new sensor represents an interesting and promising alternative for the electrochemical quantification of neurotransmitters and other analytes of clinical interest.

  6. Layer-by-layer self-assembling copper tetrasulfonated phthalocyanine on carbon nanotube modified glassy carbon electrode for electro-oxidation of 2-mercaptoethanol

    International Nuclear Information System (INIS)

    Shaik, Mahabul; Rao, V.K.; Gupta, Manish; Pandey, P.

    2012-01-01

    This paper describes the electrocatalytic activity of layer-by-layer self-assembled copper tetrasulfonated phthalocyanine (CuPcTS) on carbon nanotube (CNT)-modified glassy carbon (GC) electrode. CuPcTS is immobilized on the negatively charged CNT surface by alternatively assembling a cationic poly(diallyldimethylammonium chloride) (PDDA) layer and a CuPcTS layer. UV–vis absorption spectra and electrochemical measurements suggested the successive linear depositions of the bilayers of CuPcTs and PDDA on CNT. The surface morphology was observed using scanning electron microscopy. The viability of this CuPcTS/PDDA/CNT modified GC electrode as a redox mediator for the anodic oxidation and sensitive amperometric determination of 2-mercaptoethanol (2-ME) in alkaline conditions is described. The effect of number of bilayers of CuPcTS/PDDA and pH on electrochemical oxidation of 2-ME was studied. The proposed electrochemical sensor displayed excellent characteristics towards the determination of 2-ME in 0.1 M NaOH; such as low overpotentials (− 0.15 V vs Ag/AgCl), linear concentration range of 3 × 10 −5 M to 6 × 10 −3 M, and with a detection limit of 2.5 × 10 −5 M using simple amperometry. - Highlights: ► Carbon nanotubes (CNT) were drop-dried on glassy carbon electrode (GCE). ► Copper tetrasulfonated phthalocyanine (CuPcTS) was deposited on CNT/GCE. ► Layer-by-layer self-assembling method is used for depositing CuPcTS. ► Electrocatalytic oxidation of 2-mercaptoethanol (ME) was studied at this electrode ► The detection limit of ME at modified electrode was 25 μM by amperometry.

  7. Multi-walled Carbon Nanotubes/Graphite Nanosheets Modified Glassy Carbon Electrode for the Simultaneous Determination of Acetaminophen and Dopamine.

    Science.gov (United States)

    Zhang, Susu; He, Ping; Zhang, Guangli; Lei, Wen; He, Huichao

    2015-01-01

    Graphite nanosheets prepared by thermal expansion and successive sonication were utilized for the construction of a multi-walled carbon nanotubes/graphite nanosheets based amperometric sensing platform to simultaneously determine acetaminophen and dopamine in the presence of ascorbic acid in physiological conditions. The synergistic effect of multi-walled carbon nanotubes and graphite nanosheets catalyzed the electrooxidation of acetaminophen and dopamine, leading to a remarkable potential difference up to 200 mV. The as-prepared modified electrode exhibited linear responses to acetaminophen and dopamine in the concentration ranges of 2.0 × 10(-6) - 2.4 × 10(-4) M (R = 0.999) and 2.0 × 10(-6) - 2.0 × 10(-4) M (R = 0.998), respectively. The detection limits were down to 2.3 × 10(-7) M for acetaminophen and 3.5 × 10(-7) M for dopamine (S/N = 3). Based on the simple preparation and prominent electrochemical properties, the obtained multi-walled carbon nanotubes/graphite nanosheets modified electrode would be a good candidate for the determination of acetaminophen and dopamine without the interference of ascorbic acid.

  8. Voltammetric determination of bisphenol A in food package by a glassy carbon electrode modified with carboxylated multi-walled carbon nanotubes

    International Nuclear Information System (INIS)

    Li, J.; Kuang, D.; Feng, Y.; Zhang, F.; Liu, M.

    2011-01-01

    A highly sensitive and mercury-free method for determination of bisphenol A (BPA) was established using a glassy carbon electrode that was modified with carboxylated multi-walled carbon nanotubes. A sensitive oxidation peak is found at 550 mV in linear sweep voltammograms at pH 7. Based on this finding, trace levels of bisphenol A can be determined over a concentration range that is linear from 10 nM to 104 nM, the correlation coefficient being 0.9983, and the detection limit (S/N = 3) being 5.0 nM. The method was successfully applied to the determination of BPA in food package. (author)

  9. A glassy carbon electrode modified with a nickel(II) norcorrole complex and carbon nanotubes for simultaneous or individual determination of ascorbic acid, dopamine, and uric acid

    International Nuclear Information System (INIS)

    Deng, Keqin; Li, Xiaofang; Huang, Haowen

    2016-01-01

    The authors report on the synthesis of a hybrid material consisting of the porphyrinoid metal complex nickel(II) norcorrole that was noncovalently bound to carbon nanotubes (CNT-NiNC). The hybrid was characterized by UV–vis, FTIR spectroscopy, and thermogravimetric analysis. The CNT-NiNC hybrid possesses high catalytic activity and selectivity toward the oxidation of ascorbic acid, dopamine, and uric acid. It was used to modify a glassy carbon electrode which then is shown to enable simultaneous or individual determination of ascorbic acid (AA), dopamine (DA), and uric acid (UA) at pH 6.5 and typical working potentials of −70, 200 and 380 mV (vs. SCE). The detection limits (at an SNR of 3) are 2.0 μM for AA, 0.1 μM for DA, and 0.4 μM for UA. (author)

  10. A glassy carbon electrode modified with a multiwalled carbon nanotube-reduced graphene oxide nanoribbon core-shell structure for electrochemical sensing of p-dihydroxybenzene

    International Nuclear Information System (INIS)

    Zhu, Gangbing; Yi, Yinhui; Liu, Zhenjiang; Sun, Jianfan; Wu, Xiangyang; Zou, Bin

    2015-01-01

    Multiwalled carbon nanotubes (MWCNT) were covered with reduced graphene oxide nanoribbons (rGONR) to give a material with a core-shell heterostructure of the type MWCNT-rGONR. It was obtained by (a) longitudinal partial unzipping of MWCNT to form MWCNT-GONR, and (b) subsequent chemical reduction with hydrazine to give MWCNT-rGONR. The MWCNT-rGONR heterostructure was used to modify a glassy carbon electrode (GCE) to obtain an electrochemical sensor for p-dihydroxybenzene (DHB). The synergistic effects of the MWCNT and the rGONR results in a distinctly improved redox current towards DHB compared to a bare GCE, an MWCNT/GCE, and an MWCNT-GONR/GCE. At the working voltage range from −1 00 to 400 mV, it displays a linear response to DHB in the 80 to 3000 nM concentration range with a 20 nM detection limit. (author)

  11. Glassy carbon electrode modified with horse radish peroxidase/organic nucleophilic-functionalized carbon nanotube composite for enhanced electrocatalytic oxidation and efficient voltammetric sensing of levodopa

    Energy Technology Data Exchange (ETDEWEB)

    Shoja, Yalda; Rafati, Amir Abbas, E-mail: aa_rafati@basu.ac.ir; Ghodsi, Javad

    2016-01-01

    A novel and selective enzymatic biosensor was designed and constructed for voltammetric determination of levodopa (L-Dopa) in aqueous media (phosphate buffer solution, pH = 7). Biosensor development was on the basis of to physically immobilizing of horse radish peroxidase (HRP) as electrochemical catalyst by sol–gel on glassy carbon electrode modified with organic nucleophilic carbon nanotube composite which in this composite p-phenylenediamine (pPDA) as organic nucleophile chemically bonded with functionalized MWCNT (MWCNT-COOH). The results of this study suggest that prepared bioorganic nucleophilic carbon nanotube composite (HRP/MWCNT-pPDA) shows fast electron transfer rate for electro oxidation of L-Dopa because of its high electrochemical catalytic activity toward the oxidation of L-Dopa, more −NH{sub 2} reactive sites and large effective surface area. Also in this work we measured L-Dopa in the presence of folic acid and uric acid as interferences. The proposed biosensor was characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), FT-IR spectroscopy and cyclic voltammetry (CV). The differential pulse voltammetry (DPV) was used for determination of L-Dopa from 0.1 μM to 1.9 μM with a low detection limit of 40 nM (for S/N = 3) and sensitivity was about 35.5 μA/μM. Also this biosensor has several advantages such as rapid response, high stability and reproducibility. - Highlights: • Glassy carbon electrode modified by a novel composite in which pPDA as nucleophile is chemically attached to MWCNTs. • The developed biosensor exhibited excellent electrocatalytic activity in electrochemically determination of L-Dopa. • The biosensor showed acceptable sensitivity, reproducibility, detection limit, selectivity and stability. • MWCNT-pPDA provides a good electrical conductivity and large effective surface area for enzyme immobilization.

  12. A novel non-enzymatic hydrogen peroxide sensor based on single walled carbon nanotubes-manganese complex modified glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Salimi, Abdollah, E-mail: absalimi@uok.ac.i [Department of Chemistry, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Research Center for Nanotechnology, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Mahdioun, Monierosadat; Noorbakhsh, Abdollah [Department of Chemistry, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Abdolmaleki, Amir [Department of Chemistry, Isfahan University of Technology, Isfahan, 84156/83111 (Iran, Islamic Republic of); Ghavami, Raoof [Department of Chemistry, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of)

    2011-03-30

    A simple procedure was developed to prepare a glassy carbon (GC) electrode modified with single wall carbon nanotubes (SWCNTs) and phenazine derivative of Mn-complex. With immersing the GC/CNTs modified electrode into Mn-complex solution for a short period of time 20-100 s, a stable thin layer of the complex was immobilized onto electrode surface. Modified electrode showed a well defined redox couples at wide pH range (1-12). The surface coverages and heterogeneous electron transfer rate constants (k{sub s}) of immobilized Mn-complex were approximately 1.58 x 10{sup -10} mole cm{sup -2} and 48.84 s{sup -1}. The modified electrode showed excellent electrocatalytic activity toward H{sub 2}O{sub 2} reduction. Detection limit, sensitivity, linear concentration range and k{sub cat} for H{sub 2}O{sub 2} were, 0.2 {mu}M and 692 nA {mu}M{sup -1} cm{sup -2}, 1 {mu}M to 1.5 mM and 7.96({+-}0.2) x 10{sup 3} M{sup -1} s{sup -1}, respectively. Compared to other modified electrodes, this electrode has many advantageous such as remarkable catalytic activity, good reproducibility, simple preparation procedure and long term stability.

  13. A novel non-enzymatic hydrogen peroxide sensor based on single walled carbon nanotubes-manganese complex modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Salimi, Abdollah; Mahdioun, Monierosadat; Noorbakhsh, Abdollah; Abdolmaleki, Amir; Ghavami, Raoof

    2011-01-01

    A simple procedure was developed to prepare a glassy carbon (GC) electrode modified with single wall carbon nanotubes (SWCNTs) and phenazine derivative of Mn-complex. With immersing the GC/CNTs modified electrode into Mn-complex solution for a short period of time 20-100 s, a stable thin layer of the complex was immobilized onto electrode surface. Modified electrode showed a well defined redox couples at wide pH range (1-12). The surface coverages and heterogeneous electron transfer rate constants (k s ) of immobilized Mn-complex were approximately 1.58 x 10 -10 mole cm -2 and 48.84 s -1 . The modified electrode showed excellent electrocatalytic activity toward H 2 O 2 reduction. Detection limit, sensitivity, linear concentration range and k cat for H 2 O 2 were, 0.2 μM and 692 nA μM -1 cm -2 , 1 μM to 1.5 mM and 7.96(±0.2) x 10 3 M -1 s -1 , respectively. Compared to other modified electrodes, this electrode has many advantageous such as remarkable catalytic activity, good reproducibility, simple preparation procedure and long term stability.

  14. Determination of cyanide in wastewaters using modified glassy carbon electrode with immobilized silver hexacyanoferrate nanoparticles on multiwall carbon nanotube

    International Nuclear Information System (INIS)

    Noroozifar, Meissam; Khorasani-Motlagh, Mozhgan; Taheri, Aboozar

    2011-01-01

    Research highlights: → GC electrode modified with silver hexacyanoferrate nanoparticles (SHFNPs) immobilized on MWCNT. → Modified electrode use for determination of Cyanide in waste water. → The detection limit of the sensor is 8.3 nM. → The linear range is from 40.0 nM to 150.0 μM. - Abstract: The sensitive determination of cyanide in wastewaters using modified GC electrode with silver hexacyanoferrate nanoparticles (SHFNPs) immobilized on multiwall carbon nanotube (MWCNT) was reported. The immobilization of SHFNPs on MWCNT was confirmed by transmission electron microscopy (TEM). The TEM image showed that the SHFNPs retained the spherical morphology after immobilized on MWCNT. The size of SHFNPs was examined around 27 nm. The GC/MWCNT-SHFNPs was used for the determination of cyanide in borax buffer (BB) solution (pH 8.0). Using square wave voltammetry, the current response of cyanide increases linearly while increasing its concentration from 40.0 nM to 150.0 μM and a detection limit was found to be 8.3 nM (S/N = 3). The present modified electrode was also successfully used for the determination of 5.0 μM cyanide in the presence of common contaminants at levels presenting in industrial wastewaters. The practical application of the present modified electrode was demonstrated by measuring the concentration of cyanide in industrial wastewater samples. Moreover, the studied sensor exhibited high sensitivity, good reproducibility and long-term stability.

  15. Simultaneous determination of mycophenolate mofetil and its active metabolite, mycophenolic acid, by differential pulse voltammetry using multi-walled carbon nanotubes modified glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Madrakian, Tayyebeh, E-mail: madrakian@basu.ac.ir; Soleimani, Mohammad; Afkhami, Abbas

    2014-09-01

    A highly sensitive electrochemical sensor for the simultaneous determination of mycophenolate mofetil (MPM) and mycophenolic acid (MPA) was fabricated by multi-walled carbon nanotubes modified glassy carbon electrode (MWCNTs/GCE). The electrochemical behavior of these two drugs was studied at the modified electrode using cyclic voltammetry and adsorptive differential pulse voltammetry. MPM and MPA were oxidized at the GCE during an irreversible process. DPV analysis showed two oxidation peaks at 0.87 V and 1.1 V vs. Ag/AgCl for MPM and an oxidation peak at 0.87 V vs. Ag/AgCl for MPA in phosphate buffer solution of pH 5.0. The MWCNTs/GCE displayed excellent electrochemical activities toward oxidation of MPM and MPA relative to the bare GCE. The experimental design algorithm was used for optimization of DPV parameters. The electrode represents linear responses in the range 5.0 × 10{sup −6} to 1.6 × 10{sup −4} mol L{sup −1} and 2.5 × 10{sup −6} mol L{sup −1} to 6.0 × 10{sup −5} mol L{sup −1} for MPM and MPA, respectively. The detection limit was found to be 9.0 × 10{sup −7} mol L{sup −1} and 4.0 × 10{sup −7} mol L{sup −1} for MPM and MPA, respectively. The modified electrode showed a good sensitivity and stability. It was successfully applied to the simultaneous determination of MPM and MPA in plasma and urine samples. - Highlights: • A new modified electrochemical sensor was constructed and used. • Multiwalled carbon nanotubes were used as the modifiers. • MPM and MPA were measured simultaneously at the low levels. • The sensor was used to the determination of MPA and MPM in real samples.

  16. A sensitive electrochemical sensor for paracetamole based on a glassy carbon electrode modified with multiwalled carbon nanotubes and dopamine nanospheres functionalized with gold nanoparticles

    International Nuclear Information System (INIS)

    Liu, Xue; Wang, Ling-Ling; Wang, Ya-Ya; Zhang, Xiao-Yan

    2014-01-01

    We describe an electrochemical sensor for paracetamole that is based on a glassy carbon electrode modified with multiwalled carbon nanotubes and dopamine nanospheres functionalized with gold nanoparticles. The functionalized nanospheres were prepared by a chemical route and characterized by scanning electron microscopy. The well-dispersed gold nanoparticles were anchored on the dopamine nanosphere via a chemical reduction of the gold precursor. The stepwise fabrication of the modified electrode and its electrochemical response to paracetamole were evaluated using electrochemical impedance spectroscopy and cyclic voltammetry. The modified electrode displayed improved electrocatalytic activity towards paracetamole, a lower oxidation potential (371 mV), and a larger peak current when compared to a bare electrode or other modified electrodes. The kinetic parameters governing the electro-oxidation of paracetamole were studied, and the analytical conditions were optimized. The peak current was linearly related to the concentration of paracetamole in 0.8–400 μM range, and the detection limit was 50 nM (at an SNR of 3). The method was successfully applied to the determination of paracetamole in spiked human urine samples and gave recoveries between 95.3 and 105.2 %. (author)

  17. Selective Determination of Serotonin on Poly(3,4-ethylenedioxy pyrrole)-single-walled Carbon Nanotube-Modified Glassy Carbon Electrodes

    International Nuclear Information System (INIS)

    Kim, Seul Ki; Bae, Si Ra; Ahmed, Mohammad Shamsuddin; You, Jung Min; Jeon, Seung Won

    2011-01-01

    An electrochemically-modified electrode [P(EDOP-SWNTs)/GCE] was prepared by electropolymerization of 3,4-ethylenedioxy pyrrole (EDOP) single-walled carbon nanotubes (SWNTs) on the surface of a glassy carbon electrode (GCE) and characterized by SEM, CV, and DPV. This modified electrode was employed as an electrochemical biosensor for the selective determination of serotonin concentrations at pH 7.4 and exhibited a typical enhanced effect on the current response of serotonin with a lower oxidation overpotential. The linear response was in the range of 1.0 x 10"-"7 to 1.0 x 10"-"5 M, with a correlation coefficient of 0.998 on the anodic current. The lower detection limit was calculated as 5.0 nM. Due to the relatively low currents and difference of potentials in the electrochemical responses of uric acid (UA), ascorbic acid (AA), and dopamine (DA), the modified electrode was a useful and effective sensing device for the selective and sensitive serotonin determination in the presence of UA, AA, and DA

  18. Selective Determination of Serotonin on Poly(3,4-ethylenedioxy pyrrole)-single-walled Carbon Nanotube-Modified Glassy Carbon Electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seul Ki; Bae, Si Ra; Ahmed, Mohammad Shamsuddin; You, Jung Min; Jeon, Seung Won [Chonnam National University, Gwangju (Korea, Republic of)

    2011-04-15

    An electrochemically-modified electrode [P(EDOP-SWNTs)/GCE] was prepared by electropolymerization of 3,4-ethylenedioxy pyrrole (EDOP) single-walled carbon nanotubes (SWNTs) on the surface of a glassy carbon electrode (GCE) and characterized by SEM, CV, and DPV. This modified electrode was employed as an electrochemical biosensor for the selective determination of serotonin concentrations at pH 7.4 and exhibited a typical enhanced effect on the current response of serotonin with a lower oxidation overpotential. The linear response was in the range of 1.0 x 10{sup -7} to 1.0 x 10{sup -5} M, with a correlation coefficient of 0.998 on the anodic current. The lower detection limit was calculated as 5.0 nM. Due to the relatively low currents and difference of potentials in the electrochemical responses of uric acid (UA), ascorbic acid (AA), and dopamine (DA), the modified electrode was a useful and effective sensing device for the selective and sensitive serotonin determination in the presence of UA, AA, and DA.

  19. Sensitive warfarin sensor based on cobalt oxide nanoparticles electrodeposited at multi-walled carbon nanotubes modified glassy carbon electrode (CoxOyNPs/MWCNTs/GCE)

    International Nuclear Information System (INIS)

    Gholivand, Mohammad Bagher; Solgi, Mohammad

    2017-01-01

    In this work, cobalt oxide nanoparticles were electrodeposited on multi-walled carbon nanotubes modified glassy carbon electrode (MWCNTs/GCE) to develop a new sensor for warfarin determination. The modified electrodes were characterized by cyclic voltammetry, scanning electron microscopy (SEM) along with energy dispersive x-ray spectroscopy (EDS), and electrochemical impedance spectroscopy (EIS). The presence of cobalt oxide nanoparticles on the electrode surface enhanced the warfarin accumulation and its result was the improvement in the electrochemical response. The effect of various parameters such as pH, scan rate, accumulation potential, accumulation time and pulse amplitude on the sensor response were investigated. Under optimal conditions, the differential pulse adsorptive anodic stripping voltammetric (DPASV) response of the modified electrode was linear in the ranges of 8 nM to 50 μM and 50 μM to 800 μM with correlation coefficients greater than 0.998. The limit of detection of the proposed method was 3.3 nM. The proposed sensor was applied to determine warfarin in urine and plasma samples.

  20. Impedimetric Salmonella aptasensor using a glassy carbon electrode modified with an electrodeposited composite consisting of reduced graphene oxide and carbon nanotubes

    International Nuclear Information System (INIS)

    Jia, Fei; Dai, Ruitong; Duan, Nuo; Wu, Shijia; Wang, Zhouping; Li, Xingmin

    2016-01-01

    We describe a Salmonella biosensor that was obtained by electrochemical immobilization of a nanocomposite consisting of reduced graphene oxide (rGO) and carboxy-modified multi-walled carbon nanotubes (MWCNTs) directly on the surface of a glassy carbon electrode (GCE). An amino-modified aptamer specific for Salmonella was covalently bound to the rGO-MWCNT composite via amide bonds. The morphology of the rGO-MWCNT nanocomposite was characterized by transmission electron microscopy and scanning electron microscopy. Cyclic voltammetry and electrochemical impedance spectroscopy were used to monitor all steps during assembly. When exposed to samples containing Salmonella, the anti-Salmonella aptamer on the electrode captures its target. Hence, electron transfer is blocked, and this results in a large increase in impedance. Salmonella can be quantified by this aptasensor, typically operated at a working voltage of 0.2 V (vs. Ag/AgCl), in the range from 75 to 7.5 × 10 5 cfu⋅mL −1 and detection limit of 25 cfu⋅mL −1 (at an S/N of 3). The method is perceived to have a wide scope in that other bacteria may be detected by analogy to this approach and with very low limits of detection by applying respective analyte-specific aptamers. (author)

  1. An electrochemical sensor for rizatriptan benzoate determination using Fe3O4 nanoparticle/multiwall carbon nanotube-modified glassy carbon electrode in real samples.

    Science.gov (United States)

    Madrakian, Tayyebeh; Maleki, Somayeh; Heidari, Mozhgan; Afkhami, Abbas

    2016-06-01

    In this paper a sensitive and selective electrochemical sensor for determination of rizatriptan benzoate (RZB) was proposed. A glassy carbon electrode was modified with nanocomposite of multiwalled carbon nanotubes (MWCNTs) and Fe3O4 nanoparticles (Fe3O4/MWCNTs/GCE). The results obtained clearly show that the combination of MWCNTs and Fe3O4 nanoparticles definitely improves the sensitivity of modified electrode to RZB determination. The morphology and electroanalytical performance of the fabricated sensor were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), square wave voltammetry (SWV) and cyclic voltammetry (CV). Also, the effect of experimental and instrumental parameters on the sensor response was evaluated. The square wave voltammetric response of the electrode to RZB was linear in the range 0.5-100.0 μmol L(-1) with a detection limit of 0.09 μmol L(-1) under the optimum conditions. The investigated method showed good stability, reproducibility and repeatability. The proposed sensor was successfully applied for real life samples of blood serum and RZB determination in pharmaceutical. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Simultaneous electrochemical determination of dopamine and paracetamol on multiwalled carbon nanotubes/graphene oxide nanocomposite-modified glassy carbon electrode.

    Science.gov (United States)

    Cheemalapati, Srikanth; Palanisamy, Selvakumar; Mani, Veerappan; Chen, Shen-Ming

    2013-12-15

    In the present study, multiwalled carbon nanotubes (MWCNT)/graphene oxide (GO) nanocomposite was prepared by homogenous dispersion of MWCNT and GO and used for the simultaneous voltammetric determination of dopamine (DA) and paracetamol (PA). The TEM results confirmed that MWCNT walls were wrapped well with GO sheets. The MWCNT/GO nanocomposite showed superior electrocatalytic activity towards the oxidation of DA and PA, when compared with either pristine MWCNT or GO. The major reason for the efficient simultaneous detection of DA and PA at nanocomposite was the synergistic effect between MWCNT and GO. The electrochemical oxidation of DA and PA was investigated by cyclic voltammetry, differential pulse voltammetry and amperometry. The nanocomposite modified electrode showed electrocatalytic oxidation of DA and PA in the linear response range from 0.2 to 400 µmol L(-1) and 0.5 to 400 µmol L(-1) with the detection limit of 22 nmol L(-1) and 47 nmol L(-1) respectively. The proposed sensor displayed good selectivity, sensitivity, stability with appreciable consistency and precision. © 2013 Elsevier B.V. All rights reserved.

  3. Highly sensitive amperometric sensor for micromolar detection of trichloroacetic acid based on multiwalled carbon nanotubes and Fe(II)–phtalocyanine modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Kurd, Masoumeh; Salimi, Abdollah; Hallaj, Rahman

    2013-01-01

    A highly sensitive electrochemical sensor for the detection of trichloroacetic acid (TCA) is developed by subsequent immobilization of phthalocyanine (Pc) and Fe(II) onto multiwalled carbon nanotubes (MWCNTs) modified glassy carbon (GC) electrode. The GC/MWCNTs/Pc/Fe(II) electrode showed a pair of well-defined and nearly reversible redox couple correspondent to (Fe(III)Pc/Fe(II)Pc) with surface-confined characteristics. The surface coverage (Γ) and heterogeneous electron transfer rate constant (k s ) of immobilized Fe(II)–Pc were calculated as 1.26 × 10 −10 mol cm −2 and 28.13 s −1 , respectively. Excellent electrocatalytic activity of the proposed GC/MWCNTs/Pc/Fe(II) system toward TCA reduction has been indicated and the three consequent irreversible peaks for electroreduction of CCl 3 COOH to CH 3 COOH have been clearly seen. The observed chronoamperometric currents are linearly increased with the concentration of TCA at concentration range up to 20 mM. Detection limit and sensitivity of the modified electrode were 2.0 μM and 0.10 μA μM −1 cm −2 , respectively. The applicability of the sensor for TCA detection in real samples was tested. The obtained results suggest that the proposed system can serve as a promising electrochemical platform for TCA detection. Highlights: ► Phthalocyanine (PC) and Fe(II) immobilized onto MWCNTs modified GC electrode. ► A pair of well-defined redox couple correspondent to (Fe(III)Pc/Fe(II)Pc) observed. ► Modified electrode shows excellent catalytic activity to electroreduction of CCl 3 COOH. ► Amperometry and cyclic voltammetry techniques were used for detection of CCl 3 COOH. ► Detection limit and sensitivity were 2.0 μM and 0.10 μA μM −1 cm −2 , respectively

  4. Electrocatalytic Oxidation of Venlafaxine at a Multiwall Carbon Nanotubes-Ionic Liquid Gel Modified Glassy Carbon Electrode and Its Electrochemical Determination

    Directory of Open Access Journals (Sweden)

    Ling Ding

    2015-03-01

    Full Text Available The electrocatalytic oxidation of venlafaxine (VEN was investigated at a glassy carbon electrode (GCE, the modified electrode by a gel containing multiwall carbon nanotubes (MWCNTs and a room-temperature ionic liquid (RTIL, 1-butyl-3-methylimidazolium hexafluorophate (BMIMPF6 in 0.10 mol L−1 phosphate buffer solution (PBS, pH 6.8. It was found that an irreversible anodic oxidation peak of VEN with the peak potential (Epa as 0.780 V appeared at MWCNTs-RTIL/GCE. The electrode reaction process was a diffusion-controlled one and the electrochemical oxidation involved two electrons transferring and two protons participation. Furthermore, the charge-transfer coefficient (α, and the electrode reaction rate constant (kf of VEN were found to be 0.91 and 3.04×10−2 s−1, respectively. Under the optimized conditions, the electrocatalytic oxidation peak currents were linearly dependent on the concentration of VEN in the concentration range from 2.0×10−6 mol L−1 ~ 2.0×10−3 mol L−1 with the limit of detection (S / N = 3 as 1.69×10−6 mol L−1. The proposed method has been successfully applied in the electrochemical quantitative determination of VEN content in commercial venlafaxine hydrochloride capsules and the determination results could meet the requirement of the quantitative determination.

  5. Highly improved sensing of dopamine by using glassy carbon electrode modified with MnO2, graphene oxide, carbon nanotubes and gold nanoparticles

    International Nuclear Information System (INIS)

    Rao, Dejiang; Zhang, Xinjin; Sheng, Qinglin; Zheng, Jianbin

    2016-01-01

    A composite material obtained by ultrasonication of graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) was loaded with manganese dioxide (MnO 2 ), poly(diallyldimethylammonium chloride) and gold nanoparticles (AuNPs), and the resulting multilayer hybrid films were deposited on a glassy carbon electrode (GCE). The microstructure, composition and electrochemical behavior of the composite and the modified GCE were characterized by transmission electron microscopy, Raman spectra, energy-dispersive X-ray spectroscopy, electrochemical impedance spectroscopy and cyclic voltammetry. The electrode induces efficient electrocatalytic oxidation of dopamine at a rather low working voltage of 0.22 V (vs. SCE) at neutral pH values. The response is linear in the 0.5 μM to 2.5 mM concentration range, the sensitivity is 233.4 μA·mM -1 ·cm -2 , and the detection limit is 0.17 μM at an SNR of 3. The sensor is well reproducible and stable. It displays high selectivity over ascorbic acid, uric acid and glucose even if these are present in comparable concentrations. (author)

  6. Electrochemical tyrosine sensor based on a glassy carbon electrode modified with a nanohybrid made from graphene oxide and multiwalled carbon nanotubes

    International Nuclear Information System (INIS)

    Li, J.; Kuang, D.; Feng, Y.; Zhang, F.; Xu, Z.; Liu, M.; Wang, D.

    2013-01-01

    We report on a glassy carbon electrode that was modified with a composite made from graphene oxide (GO) and multiwalled carbon nanotubes (MWCNT) that enables highly sensitive determination of L-tyrosine. The sensor was characterized by transmission electron microscopy and electrochemical impedance spectroscopy, and its electrochemical properties by cyclic voltammetry, chronocoulometry and differential pulse voltammetry. The GO/MWCNT hybrid exhibits strong catalytic activity toward the oxidation of L-tyrosine, with a well defined oxidation peak at 761 mV. The respective current serves as the analytical information and is proportional to the L-tyrosine concentration in two ranges of different slope (0.05 to 1.0 μM and 1.0 to 650.0 μM), with limits of detection and quantification as low as 4.4 nM and 14.7 nM, respectively. The method was successfully applied to the analysis of L-tyrosine in human body fluids. The excellent reproducibility, stability, sensitivity and selectivity are believed to be due to the combination of the electrocatalytic properties of both GO and MWCNT. They are making this hybrid electrode a potentially useful electrochemical sensing platform for bioanalysis. (author)

  7. Electrochemical tyrosine sensor based on a glassy carbon electrode modified with a nanohybrid made from graphene oxide and multiwalled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Li, J.; Kuang, D.; Feng, Y.; Zhang, F.; Xu, Z.; Liu, M.; Wang, D., E-mail: junhua325@yahoo.com.cn [Key Laboratory of Functional Organometallic Materials of Hunan Province College, Department of Chemistry and Material Science, Hengyang Normal University, Hunan, Hengyang, 421008 (China)

    2013-01-15

    We report on a glassy carbon electrode that was modified with a composite made from graphene oxide (GO) and multiwalled carbon nanotubes (MWCNT) that enables highly sensitive determination of L-tyrosine. The sensor was characterized by transmission electron microscopy and electrochemical impedance spectroscopy, and its electrochemical properties by cyclic voltammetry, chronocoulometry and differential pulse voltammetry. The GO/MWCNT hybrid exhibits strong catalytic activity toward the oxidation of L-tyrosine, with a well defined oxidation peak at 761 mV. The respective current serves as the analytical information and is proportional to the L-tyrosine concentration in two ranges of different slope (0.05 to 1.0 {mu}M and 1.0 to 650.0 {mu}M), with limits of detection and quantification as low as 4.4 nM and 14.7 nM, respectively. The method was successfully applied to the analysis of L-tyrosine in human body fluids. The excellent reproducibility, stability, sensitivity and selectivity are believed to be due to the combination of the electrocatalytic properties of both GO and MWCNT. They are making this hybrid electrode a potentially useful electrochemical sensing platform for bioanalysis. (author)

  8. A very low potential electrochemical detection of L-cysteine based on a glassy carbon electrode modified with multi-walled carbon nanotubes/gold nanorods.

    Science.gov (United States)

    Silva, Francisco de Assis dos Santos; da Silva, Monique Gabriella Angelo; Lima, Phabyanno Rodrigues; Meneghetti, Mario Roberto; Kubota, Lauro Tatsuo; Goulart, Marilia Oliveira Fonseca

    2013-12-15

    A nanohybrid platform built with multi-walled carbon nanotubes and gold nanorods, prepared via a cationic surfactant-containing seed-mediated sequential growth process, in aqueous solution, on a glassy carbon substrate has been successfully developed to be used in the electrocatalytic oxidation of L-cysteine (Cys). The nanohybrid was characterized by transmission electron microscopy, Raman spectroscopy and electrochemical measurements. Cyclic voltammetry results had shown that the modified electrode allows the oxidation of Cys at a very low anodic potential (0.00 V vs. Ag/AgCl). The kinetic constant kcat for the catalytic oxidation of Cys was evaluated by chronoamperometry and provided a value of 5.6×10(4) L mol(-1) s(-1). The sensor presents a linear response range from 5.0 up to 200.0 µmol L(-1), detection limit of 8.25 nmol L(-1) and a sensitivity of 120 nA L µmol(-1). Copyright © 2013 Elsevier B.V. All rights reserved.

  9. Immunoassay for serum amyloid A using a glassy carbon electrode modified with carboxy-polypyrrole, multiwalled carbon nanotubes, ionic liquid and chitosan

    International Nuclear Information System (INIS)

    Xia, Chunyong; Li, Yuan; Yuan, Guolin; Guo, Yanlei; Yu, Chao

    2015-01-01

    We report on a highly sensitive electrochemical immunoassay for the serum inflammation marker amyloid A (SAA). It is making use of a glassy carbon electrode that was modified with carboxy-endcapped polypyrrole (PPy-α-COOH), multiwalled carbon nanotubes (MWCNTs), ionic liquid and chitosan acting as the support platform. The nanocomposite increases the sensitivity and stability of the assay. Antibody against SAA was immobilized on a monolayer surface consisting of PPy-α-COOH. The electrode material was characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectra, cyclic voltammetry, electrochemical impedance spectroscopy and differential pulse voltammetry. The calibration plot for this assay, when operated at 0.16 V (vs. SCE) and applied to spiked serum samples, is linear in the 0.001 to 900 ng mL −1 SAA concentration range, and the detection limit is as low as 0.3 pg mL −1 (at an S/N ratio of 3). The electrode is stable and highly sensitive. The detection scheme is likely to be applicable to numerous other kinds of immunoassays. (author)

  10. Simple flow injection for determination of sulfite by amperometric detection using glassy carbon electrode modified with carbon nanotubes-PDDA-gold nanoparticles.

    Science.gov (United States)

    Amatatongchai, Maliwan; Sroysee, Wongduan; Chairam, Sanoe; Nacapricha, Duangjai

    2015-02-01

    A new approach is presented for sensitive and selective measurement of sulfite (SO3(2-)) in beverages based on a simple flow injection system with amperometric detection. In this work, the sulfite sensor was a glassy carbon electrode modified with multiwall carbon nanotubes-poly(diallyldimethylammonium chloride)-gold nanoparticles composites (CNTs-PDDA-AuNPs/GC). Electrochemical oxidation of sulfite with this electrode was first studied in 0.1M phosphate buffer (pH 7.0) using cyclic voltammetry. The results indicated that the CNTs-PDDA-AuNPs/GC electrode possesses electrocatalytic activity for the oxidation of sulfite with high sensitivity and selectivity. Sulfite was quantified using amperometric measurement with the new sensor at +0.4V vs Ag/AgCl in conjunction with flow injection. The linear working range for the quantitation of sulfite was 2-200 mg L(-1) (r(2)=0.998) with a detection limit of 0.03 mg L(-1) (3σ of blank) and an estimated precision of 1.5%.The proposed method was successfully applied to the determination of sulfite in fruit juices and wines with a sample throughput of 23 samples per hour. Copyright © 2014 Elsevier B.V. All rights reserved.

  11. Anodic Stripping Voltammetric Detection of Arsenic(III) at Platinum-Iron(III) Nanoparticle Modified Carbon Nanotube on Glassy Carbon Electrode

    International Nuclear Information System (INIS)

    Shin, Seung Hyun; Hong, Hun Gi

    2010-01-01

    The electrochemical detection of As(III) was investigated on a platinum-iron(III) nanoparticles modified multiwalled carbon nanotube on glassy carbon electrode(nanoPt-Fe(III)/MWCNT/GCE) in 0.1 M H 2 SO 4 . The nanoPt-Fe(III)/ MWCNT/GCE was prepared via continuous potential cycling in the range from .0.8 to 0.7 V (vs. Ag/AgCl), in 0.1 M KCl solution containing 0.9 mM K 2 PtCl 6 and 0.6 mM FeCl 3 . The Pt nanoparticles and iron oxide were co-electrodeposited into the MWCNT-Nafion composite film on GCE. The resulting electrode was examined by cyclic voltammetry (CV), scanning electron microscopy (SEM), and anodic stripping voltammetry (ASV). For the detection of As(III), the nanoPt-Fe(III)/MWCNT/GCE showed low detection limit of 10 nM (0.75 ppb) and high sensitivity of 4.76 μAμM -1 , while the World Health Organization's guideline value of arsenic for drinking water is 10 ppb. It is worth to note that the electrode presents no interference from copper ion, which is the most serious interfering species in arsenic detection

  12. Mercury-free simultaneous determination of cadmium and lead at a glassy carbon electrode modified with multi-wall carbon nanotubes

    International Nuclear Information System (INIS)

    Wu Kangbing; Hu Shengshui; Fei Junjie; Bai Wen

    2003-01-01

    A multi-wall carbon nanotube (MWNT) modified glassy carbon electrode (GCE) was described for the simultaneous determination of trace levels of cadmium and lead by anodic stripping voltammetry (ASV). In pH 4.5 NaAc-HAc buffer containing 0.02 mol/l KI, Cd 2+ and Pb 2+ first adsorb onto the surface of a MWNT film coated GCE and then reduce at -1.20 V. During the positive potential sweep, reduced cadmium and lead were oxidized, and two well-defined stripping peaks appeared at -0.88 and -0.62 V. Compared with a bare GCE, a MWNT film coated GCE greatly improves the sensitivity of determining cadmium and lead. Low concentration of I - significantly enhances the stripping peak currents since it induces Cd 2+ and Pb 2+ to adsorb at the electrode surface. The striping peak currents change linearly with the concentration of Cd 2+ from 2.5x10 -8 to 1x10 -5 mol/l and with that of Pb 2+ from 2x10 -8 to 1x10 -5 mol/l. The lowest detectable concentrations of Cd 2+ and Pb 2+ are estimated to be 6x10 -9 and 4x10 -9 mol/l, respectively. The high sensitivity, selectivity, and stability of this MWNT film coated electrode demonstrated its practical application for a simple, rapid and economical determination of trace levels of Cd 2+ and Pb 2+ in water samples

  13. A glassy carbon electrode modified with an amphiphilic, electroactive and photosensitive polymer and with multi-walled carbon nanotubes for simultaneous determination of dopamine and paracetamole

    International Nuclear Information System (INIS)

    Liu, Ren; Zeng, Xuebiao; Liu, Jingcheng; Luo, Jing; Zheng, Yuanyi; Liu, Xiaoya

    2016-01-01

    The article describes an electrochemical sensor for simultaneous determination of dopamine (DA) and paracetamole (PAT). It is based on the use of an electroactive polymer (referred to as BPVCM) to functionalize multi-walled carbon nanotubes. BPVCM is a branched amphiphilic photo-sensitive and electroactive polymer that was obtained by copolymerization of a vinyl benzyl carbazole, maleic acid anhydride, 4-vinyl benzylthiol and a vinylbenzyl oxycoumarin. BPVCM efficiently disperses MWCNT in aqueous solution. The electropolymerization of the carbazole moieties of the BPVCM enhances the current response. It also facilitates electron transfer in the MWCNT-BPVCM hybrid as evidenced by cyclic voltammetry and electrochemical impedance spectroscopy. A glassy carbon electrode modified with the nanocomposite displays outstanding electrocatalytic activity towards DA and PAT. DA can be determined, best at a working voltage of 0.2 V (vs. SCE), in the 5 to 1000 μM concentration range with a 2.3 μM detection limit. PAT can be determined in parallel, at a working voltage of 0.39 V (vs. SCE), in the same concentration range with a 3.5 μM detection limit. This analytical range of this method is wider than that of most alternative methods. (author)

  14. Determination of dopamine using a glassy carbon electrode modified with a graphene and carbon nanotube hybrid decorated with molybdenum disulfide flowers

    International Nuclear Information System (INIS)

    Mani, Veerappan; Govindasamy, Mani; Chen, Shen-Ming; Karthik, Raj; Huang, Sheng-Tung

    2016-01-01

    We describe a hybrid material that consists of molybdenum sulfide flowers placed on graphene nanosheets and multiwalled carbon nanotubes (GNS-CNTs/MoS_2). It was deposited on a glassy carbon electrode (GCE) which then is well suited for sensitive and selective determination of dopamine. The GNS-CNTs/MoS_2 nanocomposite was prepared by a hydrothermal method and characterized by scanning electron and transmission emission microscopies, energy-dispersive X-ray spectroscopy, cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy. Electrochemical studies show the composite to possess excellent electrochemical properties such as a large electrochemically active surface, high capacitance current, a wide potential window, high conductivity and large porosity. The electrode displays excellent electrocatalytic ability to oxidize dopamine. The modified GCE, best operated at a working potential as low as 0.15 V (vs. Ag/AgCl), responds linearly to dopamine in the 100 nM to 100 μM concentration range. The detection limit is 50 nM, and the sensitivity is 10.81 (± 0.26) μA⋅μM"−"1⋅cm"−"2. The sensor has good selectivity, appreciable stability, repeatability and reproducibility. It was applied to the determination of dopamine in (spiked) biological and pharmaceutical samples. (author)

  15. Voltammetric determination of the endocrine disruptor diethylstilbestrol by using a glassy carbon electrode modified with a composite consisting of platinum nanoparticles and multiwalled carbon nanotubes

    International Nuclear Information System (INIS)

    Hu, Xiaobin; Zhang, Rongfei

    2016-01-01

    A nanocomposite consisting of multi-walled carbon nanotubes (MWCNTs) decorated with Pt nanoparticles (Pt-NPs) was synthesized via an ionic liquid-assisted method. The composite was characterized by transmission electron microscopy, X-ray diffraction patterns, and X-ray photo-electron spectroscopy. The results showed the Pt-NPs to be evenly deposited on the surface of the MWCNTs, with diameters ranging from about 2 nm to 3 nm. The nanocomposite was used to modify a glassy carbon electrode which then revealed a substantial catalytic activity for the oxidation of diethylstilbestrol (DES), best at a working potential of 0.73 V (vs. Ag/AgCl) at pH 7. The electrochemical oxidation mechanism is discussed. The peak current in square wave voltammetry is linearly related to the concentration of DES in the 0.1 to 25 μM range. The limit of detection (at an SNR of 3) is 12 nM. (author)

  16. A glassy carbon electrode modified with β-cyclodextin, multiwalled carbon nanotubes and graphene oxide for sensitive determination of 1,3-dinitrobenzene

    International Nuclear Information System (INIS)

    Li, Junhua; Feng, Haibo; Liu, Jinlong; Liu, Youcai; Jiang, Jianbo; Feng, Yonglan; Qian, Dong

    2014-01-01

    We are presenting a host-guest electrochemical platform for sensing the pollutant 1,3-dinitrobenzene. The method is based on the use of a glassy carbon electrode (GCE) covered with a composite made from multiwalled carbon nanotubes and graphene oxide, and functionalized with β-cyclodextrin (β-CD). The resultant composite was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis and electrochemical techniques. The modified GCE was used for the sensitive detection of 1,3-dinitrobenzene (DNB) at working voltages of −355 mV and −483 mV. Due to the specific recognition property of β-CD and the excellent electronic properties of the carbon nanomaterials, the electrode exhibits outstanding supramolecular recognition and enhanced electrochemical response to DNB compared to more conventional electrodes. Under optimum conditions, the peak currents vary linearly with the DNB concentrations in the range from 0.02 to 30.0 μM, and the detection limit is 5.0 nM (at an S/N of 3). The electrode exhibits long-term stability and has been successfully applied to the determination of DNB in spiked soil and water samples. (author)

  17. Manganese oxide nanoflakes/multi-walled carbon nanotubes/chitosan nanocomposite modified glassy carbon electrode as a novel electrochemical sensor for chromium (III) detection

    International Nuclear Information System (INIS)

    Salimi, Abdollah; Pourbahram, Bahareh; Mansouri-Majd, Samira; Hallaj, Rahman

    2015-01-01

    Highlights: • CNTs/chitosan/GC electrode used as platform for electrodeposition of MnO x -nanoflakes. • Modified electrode has excellent catalytic activity for oxidation of Cr 3+ at pH 3–7. • Detection limit and sensitivity of sensor for Cr 3+ detection were 0.3 μM and 18.7 nA/μM. • Sensor has good stability and high selectivity in the presence of common interferences. • Sensor applied for the detection of Cr 3+ in real samples with satisfactory results. - Abstract: In this research a nanocomposite containing chitosan (Chit) and maltiwalled carbon nanotubes (MWCNTs) was applied as platform for immobilization of electrodeposited manganese oxide (MnOx) nanostructures. First, glassy carbon (GC) electrode modified with thin film of Chitosan/MWCNTs nanocomposite. Then MnO x nanostructures was electrodeposited onto Chitosan/MWCNTs modified GC electrode using combination of constant potential step (0.6 V) and cyclic voltammetry(0.3–0.6 V) techniques. The XRD patterns and scanning electron microscope images indicated immobilization of uniformly MnOx nanoflakes with high crystallite onto MWCNTs/Chit film. The modified electrode shows a well-defined redox couple for Mn 2+ /MnO 2 system. Charge transfer coefficient (α), electron transfer rate constant (k s ) and surface concentration (Γ) were 0.394, 3.44 s −1 and 3.3 × 10 −11 mol cm −2 , respectively. The modified electrode showed excellent electrocatalytic activity toward oxidation of chromium (III) at natural pH solutions. Cyclic voltammetry and hydrodynamic amperometery were applied as measuring techniques for chromium detection. Detection limit, sensitivity and linear concentration range of the sensor were, 0.3 (μM), 18.7 nAμ M −1 and 3 μM to 200 μM, respectively. Moreover, the sensor retained about 90% of its original response toward Cr(III) after storage three months in ambient condition. Furthermore, the sensor response toward different common interferences was negligible. Finally, the

  18. Mercury-free simultaneous determination of cadmium and lead at a glassy carbon electrode modified with multi-wall carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Wu Kangbing; Hu Shengshui; Fei Junjie; Bai Wen

    2003-08-18

    A multi-wall carbon nanotube (MWNT) modified glassy carbon electrode (GCE) was described for the simultaneous determination of trace levels of cadmium and lead by anodic stripping voltammetry (ASV). In pH 4.5 NaAc-HAc buffer containing 0.02 mol/l KI, Cd{sup 2+} and Pb{sup 2+} first adsorb onto the surface of a MWNT film coated GCE and then reduce at -1.20 V. During the positive potential sweep, reduced cadmium and lead were oxidized, and two well-defined stripping peaks appeared at -0.88 and -0.62 V. Compared with a bare GCE, a MWNT film coated GCE greatly improves the sensitivity of determining cadmium and lead. Low concentration of I{sup -} significantly enhances the stripping peak currents since it induces Cd{sup 2+} and Pb{sup 2+} to adsorb at the electrode surface. The striping peak currents change linearly with the concentration of Cd{sup 2+} from 2.5x10{sup -8} to 1x10{sup -5} mol/l and with that of Pb{sup 2+} from 2x10{sup -8} to 1x10{sup -5} mol/l. The lowest detectable concentrations of Cd{sup 2+} and Pb{sup 2+} are estimated to be 6x10{sup -9} and 4x10{sup -9} mol/l, respectively. The high sensitivity, selectivity, and stability of this MWNT film coated electrode demonstrated its practical application for a simple, rapid and economical determination of trace levels of Cd{sup 2+} and Pb{sup 2+} in water samples.

  19. Highly sensitive amperometric sensor for micromolar detection of trichloroacetic acid based on multiwalled carbon nanotubes and Fe(II)–phtalocyanine modified glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Kurd, Masoumeh [Department of Chemistry, University of Kurdistan, P. O. Box 416, Sanandaj (Iran, Islamic Republic of); Salimi, Abdollah, E-mail: absalimi@uok.ac.ir [Department of Chemistry, University of Kurdistan, P. O. Box 416, Sanandaj (Iran, Islamic Republic of); Research Center for Nanotechnology, University of Kurdistan, P. O. Box 416, Sanandaj (Iran, Islamic Republic of); Hallaj, Rahman [Department of Chemistry, University of Kurdistan, P. O. Box 416, Sanandaj (Iran, Islamic Republic of)

    2013-04-01

    A highly sensitive electrochemical sensor for the detection of trichloroacetic acid (TCA) is developed by subsequent immobilization of phthalocyanine (Pc) and Fe(II) onto multiwalled carbon nanotubes (MWCNTs) modified glassy carbon (GC) electrode. The GC/MWCNTs/Pc/Fe(II) electrode showed a pair of well-defined and nearly reversible redox couple correspondent to (Fe(III)Pc/Fe(II)Pc) with surface-confined characteristics. The surface coverage (Γ) and heterogeneous electron transfer rate constant (k{sub s}) of immobilized Fe(II)–Pc were calculated as 1.26 × 10{sup −10} mol cm{sup −2} and 28.13 s{sup −1}, respectively. Excellent electrocatalytic activity of the proposed GC/MWCNTs/Pc/Fe(II) system toward TCA reduction has been indicated and the three consequent irreversible peaks for electroreduction of CCl{sub 3}COOH to CH{sub 3}COOH have been clearly seen. The observed chronoamperometric currents are linearly increased with the concentration of TCA at concentration range up to 20 mM. Detection limit and sensitivity of the modified electrode were 2.0 μM and 0.10 μA μM{sup −1} cm{sup −2}, respectively. The applicability of the sensor for TCA detection in real samples was tested. The obtained results suggest that the proposed system can serve as a promising electrochemical platform for TCA detection. Highlights: ► Phthalocyanine (PC) and Fe(II) immobilized onto MWCNTs modified GC electrode. ► A pair of well-defined redox couple correspondent to (Fe(III)Pc/Fe(II)Pc) observed. ► Modified electrode shows excellent catalytic activity to electroreduction of CCl{sub 3}COOH. ► Amperometry and cyclic voltammetry techniques were used for detection of CCl{sub 3}COOH. ► Detection limit and sensitivity were 2.0 μM and 0.10 μA μM{sup −1} cm{sup −2}, respectively.

  20. Amperometric sensor for ascorbic acid based on a glassy carbon electrode modified with gold-silver bimetallic nanotubes in a chitosan matrix

    International Nuclear Information System (INIS)

    Yang, Penghao; Gao, Xia; Wang, Lisha; Wu, Qi; Chen, Zhichun; Lin, Xianfu

    2014-01-01

    We report on an amperometric sensor for ascorbic acid (AA) that is based on highly dense gold-silver nanotubes in a chitosan film on a glassy carbon electrode. The nanotubes were synthesized by a poly(vinyl pyrrolidone)-mediated polyol method employing a replacement reaction with silver nanowires as templates, and were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. Under the optimal conditions, the sensor exhibits good electrocatalytic activity towards the oxidation of AA, and this enables the determination of AA in the 5 μM to 2 mM concentration range, with a detection limit at 2 μM (at an S/N of 3). The response time is 2 s. The sensor displays good reproducibility, selectivity, sensitivity, and long-term stability. (author)

  1. A glassy carbon electrode modified with a polyaniline doped with silicotungstic acid and carbon nanotubes for the sensitive amperometric determination of ascorbic acid

    International Nuclear Information System (INIS)

    Zhang, X.; Lai, G.; Zhang, H.; Yu, A.

    2013-01-01

    We report on an electrochemical sensor for the sensitive amperometric determination of ascorbic acid (AA). Aniline containing suspended silicotungstic acid and carbon nanotubes was electropolymerized on the surface of a glassy carbon electrode in a single step which provides a simple and controllable method and greatly improves the electrocatalytic oxidation of AA. The effects of scan rate, solution pH and working potential were studied. A linear relationship exists between the current measured and the concentration of AA in the range from 1 μM to 10 μM and 0.01 mM to 9 mM, with a limit of detection as low as 0.51 μM (S/N = 3). The sensor is selective, stable and satisfyingly reliable in real sample experiments. In our eyes, it has a large potential for practical applications. (author)

  2. Immobilization of [Cu(bpy)2]Br2 complex onto a glassy carbon electrode modified with alpha-SiMo12O40(4-) and single walled carbon nanotubes: application to nanomolar detection of hydrogen peroxide and bromate.

    Science.gov (United States)

    Salimi, Abdollah; Korani, Aazam; Hallaj, Rahman; Khoshnavazi, Roshan; Hadadzadeh, Hasan

    2009-03-02

    A simple procedure has been used for preparation of modified glassy carbon electrode with carbon nanotubes and copper complex. Copper complex [Cu(bpy)(2)]Br(2) was immobilized onto glassy carbon (GC) electrode modified with silicomolybdate, alpha-SiMo(12)O(40)(4-) and single walled carbon nanotubes (SWCNTs). Copper complex and silicomolybdate irreversibly and strongly adsorbed onto GC electrode modified with CNTs. Electrostatic interactions between polyoxometalates (POMs) anions and Cu-complex, cations mentioned as an effective method for fabrication of three-dimensional structures. The modified electrode shows three reversible redox couples for polyoxometalate and one redox couple for Cu-complex at wide range of pH values. The electrochemical behavior, stability and electron transfer kinetics of the adsorbed redox couples were investigated using cyclic voltammetry. Due to electrostatic interaction, copper complex immobilized onto GC/CNTs/alpha-SiMo(12)O(40)(4-) electrode shows more stable voltammetric response compared to GC/CNTs/Cu-complex modified electrode. In comparison to GC/CNTs/Cu-complex the GC/CNTs/alpha-SiMo(12)O(40)(4-) modified electrodes shows excellent electrocatalytic activity toward reduction H(2)O(2) and BrO(3)(-) at more reduced overpotential. The catalytic rate constants for catalytic reduction hydrogen peroxide and bromate were 4.5(+/-0.2)x10(3) M(-1) s(-1) and 3.0(+/-0.10)x10(3) M(-1) s(-1), respectively. The hydrodynamic amperommetry technique at 0.08 V was used for detection of nanomolar concentration of hydrogen peroxide and bromate. Detection limit, sensitivity and linear concentration range proposed sensor for bromate and hydrogen peroxide detection were 1.1 nM and 6.7 nA nM(-1), 10 nM-20 microM, 1 nM, 5.5 nA nM(-1) and 10 nM-18 microM, respectively.

  3. Amperometric biosensor for bisphenol A based on a glassy carbon electrode modified with a nanocomposite made from polylysine, single walled carbon nanotubes and tyrosinase

    International Nuclear Information System (INIS)

    Han, Miao; Qu, Ying; Chen, Shiqin; Wang, Yali; Zhang, Zhi; Zhan, Guoqing; Li, Chunya; Ma, Ming; Wang, Zhengguo

    2013-01-01

    We have prepared a nanocomposite consisting of single-walled carbon nanotubes and polylysine. It was characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, and by UV/vis and FTIR spectroscopy. Tyrosinase was covalently immobilized on the nanocomposite, and the resulting bioconjugate deposited on a glassy carbon electrode to form a biosensor for bisphenol A. The biosensor was characterized by scanning electron microscopy and electrochemical impedance spectroscopy. Under optimized experimental conditions, the biosensor gives a linear response to bisphenol A in the 4.00 nM to 11.5 μM concentration range. Its sensitivity is 788 mA M −1 cm −2 , and the lower detection limit is 0.97 nM (at an S/N of 3). The biosensor shows good repeatability, reproducibility and long-term stability. In a preliminary practical application, it was successfully applied to the determination of bisphenol A in leachates of plastic spoons. (author)

  4. Simultaneous determination of acetaminophen, theophylline and caffeine using a glassy carbon disk electrode modified with a composite consisting of poly(Alizarin Violet 3B), multiwalled carbon nanotubes and graphene

    International Nuclear Information System (INIS)

    Wang, Yan; Wu, Ting; Bi, Chun-yan

    2016-01-01

    The authors describe a glassy carbon disk electrode which after modification with poly(Alizarin Violet 3B), multiwalled carbon nanotubes and graphene enables simultaneous determination of the drugs acetaminophen (AP), theophylline (TP) and caffeine (CF). The electrochemical response to AP, TP and CF at the modified electrode was studied by cyclic voltammetry, and the results revealed an excellent electrocatalytic activity towards the oxidation of the three analytes at potentials of typically 0.5, 1.15 and 1.4 V (vs. SCE) respectively. The anodic peaks are well defined and occur at lower oxidation potential and enhanced oxidation peak currents (compared to an unmodified electrode). Simultaneous differential pulse voltammetric measurements resulted in calibration plot for AP, TP and CF were obtained that cover range from 0.2 to 100 μM for AP, from 0.5 to 120 μM for TP, and from 1.0 to 120 μM for CF. The respective detection limits are 0.01, 0.02 and 0.10 μM. The method was applied to simultaneous determination of AP, TP and CF in spiked human serum and gave satisfactory results. (author)

  5. A novel sensor made of Antimony Doped Tin Oxide-silica composite sol on a glassy carbon electrode modified by single-walled carbon nanotubes for detection of norepinephrine.

    Science.gov (United States)

    Wang, Zhao; Wang, Kai; Zhao, Lu; Chai, Shigan; Zhang, Jinzhi; Zhang, Xiuhua; Zou, Qichao

    2017-11-01

    In this study, we designed a novel molecularly imprinted polymer (MIP), Antimony Doped Tin Oxide (ATO)-silica composite sol, which was made using a sol-gel method. Then a sensitive and selective imprinted electrochemical sensor was constructed with the ATO-silica composite sol on a glassy carbon electrode modified by single-walled carbon nanotubes (SWNTs). The introduction of SWNTs increased the sensitivity of the MIP sensor. The surface morphology of the MIP and MIP/SWNTs were characterized by scanning electron microscopy (SEM), and the optimal conditions for detection were determined. The oxidative peak current increased linearly with the concentration of norepinephrine in the range of 9.99×10 -8 M to 1.50×10 -5 M, as detected by cyclic voltammetry (CV), the detection limit was 3.33×10 -8 M (S/N=3). In addition, the proposed electrochemical sensors were successfully applied to detect the norepinephrine concentration in human blood serum samples. The recoveries of the sensors varied from 99.67% to 104.17%, indicating that the sensor has potential for the determination of norepinephrine in clinical tests. Moreover, the imprinted electrochemical sensor was used to selectively detect norepinephrine. The analytical application was conducted successfully and yielded accurate and precise results. Copyright © 2017. Published by Elsevier B.V.

  6. Label-free electrochemical immunosensor for the carcinoembryonic antigen using a glassy carbon electrode modified with electrodeposited Prussian Blue, a graphene and carbon nanotube assembly and an antibody immobilized on gold nanoparticles

    International Nuclear Information System (INIS)

    Feng, Dexiang; Lu, Xiaocui; Dong, Xiao; Zhang, Yuzhong; Ling, Yunyun

    2013-01-01

    We described a sensitive, label-free electrochemical immunosensor for the detection of carcinoembryonic antigen. It is based on the use of a glassy carbon electrode (GCE) modified with a multi-layer films made from Prussian Blue (PB), graphene and carbon nanotubes by electrodeposition and assembling techniques. Gold nanoparticles were electrostatically absorbed on the surface of the film and used for the immobilization of antibody, while PB acts as signaling molecule. The stepwise assembly process was investigated by differential pulse voltammetry and scanning electron microscopy. It is found that the formation of antibody-antigen complexes partially inhibits the electron transfer of PB and decreased its peak current. Under the optimal conditions, the decrease of intensity of the peak current of PB is linearly related to the concentration of carcinoembryonic antigen in two ranges (0.2–1.0, and 1.0–40.0 ng·mL −1 ), with a detection limit of 60 pg·mL −1 (S/N = 3). The immunosensor was applied to analyze five clinical samples, and the results obtained were in agreement with clinical data. In addition, the immunosensor exhibited good precision, acceptable stability and reproducibility. (author)

  7. Square-wave adsorptive stripping voltammetric determination of nanomolar levels of bezafibrate using a glassy carbon electrode modified with multi-walled carbon nanotubes within a dihexadecyl hydrogen phosphate film.

    Science.gov (United States)

    Ardila, Jorge Armando; Oliveira, Geiser Gabriel; Medeiros, Roberta Antigo; Fatibello-Filho, Orlando

    2014-04-07

    A highly sensitive method for bezafibrate determination using a glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes within a dihexadecyl hydrogen phosphate film based on square-wave adsorptive stripping voltammetry (SWAdSV) is proposed. The electrochemical behaviour of bezafibrate has been studied by cyclic voltammetry, showing an irreversible anodic peak at a potential of 1.09 V in 0.1 mol L(-1) phosphate buffer solution (pH 2.0). A study of the scan rate showed that the oxidation of bezafibrate is an adsorptive-controlled process, involving the transfer of two electrons and two protons per molecule. The analytical curve was linear over a bezafibrate concentration range from 50 to 910 nmol L(-1), with a detection limit of 16 nmol L(-1). This analytical method was successfully applied for benzafibrate determination in pharmaceutical formulations, with results showing good agreement with those obtained using a comparative spectrophotometric method, and has the potential for field application.

  8. Formation of a robust and stable film comprising ionic liquid and polyoxometalate on glassy carbon electrode modified with multiwalled carbon nanotubes: Toward sensitive and fast detection of hydrogen peroxide and iodate

    Energy Technology Data Exchange (ETDEWEB)

    Haghighi, Behzad, E-mail: haghighi@iasbs.ac.i [Department of Chemistry, Institute for Advanced Studies in Basic Sciences, P.O. Box 45195 - 1159, Gava Zang, Zanjan (Iran, Islamic Republic of); Hamidi, Hassan [Department of Chemistry, Institute for Advanced Studies in Basic Sciences, P.O. Box 45195 - 1159, Gava Zang, Zanjan (Iran, Islamic Republic of); Gorton, Lo [Institute of Chemistry, Lund University, P.O. Box 124, S-221 00 Lund (Sweden)

    2010-06-30

    A robust and stable film comprising n-octylpyridinum hexafluorophosphate ([C{sub 8}Py][PF{sub 6}]) and 1:12 phosphomolybdic acid (PMo{sub 12}) was prepared on glassy carbon electrodes modified with multiwall carbon nanotubes (GCE/MWCNTs) by dip-coating. The cyclic voltammograms of the GCE/MWCNTs/[C{sub 8}Py][PF{sub 6}]-PMo{sub 12} showed three well-defined pairs of redox peaks due to the PMo{sub 12} system. The surface coverage for the immobilized PMo{sub 12} and the average values of the electron transfer rate constant for three pairs of redox peaks were evaluated. The GCE/MWCNTs/[C{sub 8}Py][PF{sub 6}]-PMo{sub 12} showed great electrocatalytic activity towards the reduction of H{sub 2}O{sub 2} and iodate. The kinetic parameters of the catalytic reduction of hydrogen peroxide and iodate at the electrode surface and analytical features of the sensor for amperometric determination of hydrogen peroxide and iodate were evaluated.

  9. EDTA modified glassy carbon electrode: Preparation and characterization

    International Nuclear Information System (INIS)

    Ustuendag, Zafer; Solak, Ali Osman

    2009-01-01

    EDTA-phenoxyamide modified glassy carbon electrode (EDTA-GC) was prepared at a glassy carbon electrode by surface synthesis. In the first step, nitrophenyl was grafted to the glassy carbon (GC) surface via the electrochemical reduction of its tetraflouroborate diazonium salt. In the second step, nitrophenyl-modified electrode (NP-GC) was subjected to the cathodic potential scan to reduce the nitro to amine group. p-Aminophenyl modified glassy carbon electrode (AP-GC) was dipped into a EDTA solution containing 1-ethyl-3(3-(dimethlyamino)propyl)-carbodiimide (EDC) as an activating agent. Thus formed ((2-anilino-2-oxoethyl){2-[bis(carboxymethyl)amino]-ethyl}amino)acetic acid modified GC electrode was denoted as EDTA-GC and characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), ellipsometry and X-ray photoelectron spectroscopy (XPS). Complexation of the EDTA-GC surface with Pb 2+ ions was investigated if this electrode could be used as a metal sensor.

  10. An electrochemical sensor for rizatriptan benzoate determination using Fe{sub 3}O{sub 4} nanoparticle/multiwall carbon nanotube-modified glassy carbon electrode in real samples

    Energy Technology Data Exchange (ETDEWEB)

    Madrakian, Tayyebeh, E-mail: madrakian@basu.ac.ir; Maleki, Somayeh; Heidari, Mozhgan; Afkhami, Abbas

    2016-06-01

    In this paper a sensitive and selective electrochemical sensor for determination of rizatriptan benzoate (RZB) was proposed. A glassy carbon electrode was modified with nanocomposite of multiwalled carbon nanotubes (MWCNTs) and Fe{sub 3}O{sub 4} nanoparticles (Fe{sub 3}O{sub 4}/MWCNTs/GCE). The results obtained clearly show that the combination of MWCNTs and Fe{sub 3}O{sub 4} nanoparticles definitely improves the sensitivity of modified electrode to RZB determination. The morphology and electroanalytical performance of the fabricated sensor were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), square wave voltammetry (SWV) and cyclic voltammetry (CV). Also, the effect of experimental and instrumental parameters on the sensor response was evaluated. The square wave voltammetric response of the electrode to RZB was linear in the range 0.5–100.0 μmol L{sup −1} with a detection limit of 0.09 μmol L{sup −1} under the optimum conditions. The investigated method showed good stability, reproducibility and repeatability. The proposed sensor was successfully applied for real life samples of blood serum and RZB determination in pharmaceutical. - Highlights: • Simple and sensitive Fe{sub 3}O{sub 4}/MWCNTs/GCE for rizatriptan benzoate determination • The surface morphology of nanocomposite was characterized by SEM and EDS. • Rizatriptan benzoate was measured at 0.09 μmol L{sup −1} with good sensitivity and selectivity. • The electrode has been successfully applied in serum and pharmaceutical samples. • The nanocomposite had excellent electrocatalytic activity and biocompatibility.

  11. Electrochemical investigations of Pu(IV)/Pu(III) redox reaction using graphene modified glassy carbon electrodes and a comparison to the performance of SWCNTs modified glassy carbon electrodes

    International Nuclear Information System (INIS)

    Gupta, Ruma; Gamare, Jayashree; Sharma, Manoj K.; Kamat, J.V.

    2016-01-01

    Highlights: • First report of aqueous electrochemistry of Plutonium on graphene modified electrode. • Graphene is best electrocatalytic material for Pu(IV)/Pu(III) redox couple among the reported modifiers viz. reduced graphene oxide (rGO) and SWCNT’s. • The electrochemical reversibility of Pu(IV)/Pu(III) redox couple improves significantly on graphene modified electrode compared to previously reported rGO & SWCNTs modified electrodes • Donnan interaction between plutonium species and graphene surface offers a possibility for designing a highly sensitive sensor for plutonium • Graphene modified electrode shows higher sensitivity for the determination of plutonium compared to glassy carbon and single walled carbon nanotube modified electrode - Abstract: The work reported in this paper demonstrates for the first time that graphene modified glassy carbon electrode (Gr/GC) show remarkable electrocatalysis towards Pu(IV)/Pu(III) redox reaction and the results were compared with that of single-walled carbon nanotubes modified GC (SWCNTs/GC) and glassy carbon (GC) electrodes. Graphene catalyzes the exchange of current of the Pu(IV)/Pu(III) couple by reducing both the anodic and cathodic overpotentials. The Gr/GC electrode shows higher peak currents (i p ) and smaller peak potential separation (ΔE p ) values than the SWCNTs/GC and GC electrodes. The heterogeneous electron transfer rate constants (k s ), charge transfer coefficients (α) and the diffusion coefficients (D) involved in the electrocatalytic redox reaction were determined. Our observations show that graphene is best electrocatalytic material among both the SWCNTs and GC to study Pu(IV)/Pu(III) redox reaction.

  12. ELECTROCHEMICAL DETERMINATION OF HYDROGEN SULFIDE AT CARBON NANOTUBE MODIFIED ELECTRODES. (R830900)

    Science.gov (United States)

    Carbon nanotube (CNT) modified glassy carbon electrodes exhibiting a strong and stable electrocatalytic response towards sulfide are described. A substantial (400 mV) decrease in the overvoltage of the sulfide oxidation reaction (compared to ordinary carbon electrodes) is...

  13. Poly-Alizarin red S/multiwalled carbon nanotube modified glassy carbon electrode for the boost up of electrocatalytic activity towards the investigation of dopamine and simultaneous resolution in the presence of 5-HT: A voltammetric study

    International Nuclear Information System (INIS)

    Reddaiah, K.; Madhusudana Reddy, T.; Venkata Ramana, D.K.; Subba Rao, Y.

    2016-01-01

    Poly-Alizarin red S/multiwalled carbon nanotube film on the surface of glassy carbon electrode (poly-AzrS/MWCNT/GCE) was synthesized by electrochemical process and was used for the sensitive and selective determination of dopamine (DA) by employing voltammetric techniques. The electrocatalytic response of the modified electrode was found to exhibit admirable activity. The simultaneous determination of dopamine in the presence of serotonin (5-HT) was found to exhibit very good response at poly-AzrS/MWCNTs/GCE. The effect of pH, scan rate, accumulation time and concentration of dopamine was studied at the developed poly-AzrS/MWCNTs/GCE. The poly-AzrS/MWCNTs/GCE exhibited an efficient electron mediating behavior together with well resolved peaks for dopamine, in 0.1 mol/dm"3 phosphate buffer (PBS) solution of pH 7.0. The limit of detection (LOD) and limit of quantification (LOQ) were found to be as 1.89 × 10"−"7 mol/dm"3 and 6.312 × 10"−"7 mol/dm"3 respectively with a dynamic range from 1 × 10"−"6 to 1.8 × 10"−"5 mol/dm"3. The interfacial electron transfer behavior of DA was studied by electrochemical impedance spectroscopy (EIS); the studies showed that the charge transfer rate was enhanced at poly-AzrS/MWCNTs/GCE when compared with bare GCE and poly-AzrS/GCE. - Highlights: • The poly-AzrS/MWCNTs/GCE showed good sensitivity towards DA sensing. • The sensor reduced the overoxidation potentials for DA. • This electrode was successfully used for simultaneous sensing of DA and 5-HT. • The electrode was effectively used for the determination of DA in pharmaceutical formulations.

  14. Poly-Alizarin red S/multiwalled carbon nanotube modified glassy carbon electrode for the boost up of electrocatalytic activity towards the investigation of dopamine and simultaneous resolution in the presence of 5-HT: A voltammetric study

    Energy Technology Data Exchange (ETDEWEB)

    Reddaiah, K. [Electrochemical Research Laboratory, Department of Chemistry, S.V.U. College of Sciences, Sri Venkateswara University, Tirupati 517 502, Andhra Pradesh (India); Madhusudana Reddy, T., E-mail: tmsreddysvu@gmail.com [Electrochemical Research Laboratory, Department of Chemistry, S.V.U. College of Sciences, Sri Venkateswara University, Tirupati 517 502, Andhra Pradesh (India); Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455 (United States); Venkata Ramana, D.K. [Department of Safety Engineering, Dongguk University, 123 Dongdae-ro, Gyeongju, Gyeongbuk 780 714 (Korea, Republic of); Subba Rao, Y. [DST-PURSE Centre, Sri Venkateswara University, Tirupati 517502, Andhra Pradesh (India)

    2016-05-01

    Poly-Alizarin red S/multiwalled carbon nanotube film on the surface of glassy carbon electrode (poly-AzrS/MWCNT/GCE) was synthesized by electrochemical process and was used for the sensitive and selective determination of dopamine (DA) by employing voltammetric techniques. The electrocatalytic response of the modified electrode was found to exhibit admirable activity. The simultaneous determination of dopamine in the presence of serotonin (5-HT) was found to exhibit very good response at poly-AzrS/MWCNTs/GCE. The effect of pH, scan rate, accumulation time and concentration of dopamine was studied at the developed poly-AzrS/MWCNTs/GCE. The poly-AzrS/MWCNTs/GCE exhibited an efficient electron mediating behavior together with well resolved peaks for dopamine, in 0.1 mol/dm{sup 3} phosphate buffer (PBS) solution of pH 7.0. The limit of detection (LOD) and limit of quantification (LOQ) were found to be as 1.89 × 10{sup −7} mol/dm{sup 3} and 6.312 × 10{sup −7} mol/dm{sup 3} respectively with a dynamic range from 1 × 10{sup −6} to 1.8 × 10{sup −5} mol/dm{sup 3}. The interfacial electron transfer behavior of DA was studied by electrochemical impedance spectroscopy (EIS); the studies showed that the charge transfer rate was enhanced at poly-AzrS/MWCNTs/GCE when compared with bare GCE and poly-AzrS/GCE. - Highlights: • The poly-AzrS/MWCNTs/GCE showed good sensitivity towards DA sensing. • The sensor reduced the overoxidation potentials for DA. • This electrode was successfully used for simultaneous sensing of DA and 5-HT. • The electrode was effectively used for the determination of DA in pharmaceutical formulations.

  15. Enzyme-less and low-potential sensing of glucose using a glassy carbon electrode modified with palladium nanoparticles deposited on graphene-wrapped carbon nanotubes

    International Nuclear Information System (INIS)

    Nayak, Pranati; Nair, Santhosh P.; Ramaprabhu, Sundara

    2016-01-01

    The article describes an amperometric sensor for enzyme-less detection of glucose based on homogeneously anchored Pd nanoparticles (Pd-NPs) on graphene - wrapped carbon nanotubes (Pd-GWCNTs) as sensing matrix. The unique features of GWCNTs (such as the highly protruded outer graphene layer and an inner tubular morphology) result in enhanced electrochemical performance compared to the use of conventional multi walled carbon nanotubes (MWCNTs). Glucose electro-oxidation occurs at a rather low working potential (+50 mV vs Ag/AgCl), and glucose can be continuously sensed in 0.1 M NaOH solution in concentrations of up to 19.5 mM. The sensor possesses good reproducibility, a fast response time, stable amperometric response and a lower detection limit. Due to its low working potential, it is not interfered by dopamine, uric acid, ascorbic acid, sucrose, fructose and lactose. We presume that these beneficial properties are a result of the synergetic advantages of using catalytic Pd NPs and graphene wrapped CNTs, both of which facilitate low-potential electrooxidation of glucose. (author)

  16. Sensitive stripping voltammetric determination of Cd(II) and Pb(II) by a Bi/multi-walled carbon nanotube-emeraldine base polyaniline-Nafion composite modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Zhao, Guo; Yin, Yuan; Wang, Hui; Liu, Gang; Wang, Zhiqiang

    2016-01-01

    Highlights: • A MWCNT-EBP-NA composite film modified GCE was fabricated and characterized. • The GCE modified with the MWCNT-EBP-NA composite film exhibited excellent performance in the analysis of Cd(II) and Pb(II) by SWASV. • The Cd(II) and Pb(II) detection limits of the developed electrode were approximately 0.06 μg/L and 0.08 μg/L, respectively. • Bi/MWCNT-EBP-NA/GCE was successfully used to determine metal ions in soil samples. - Abstract: In this study, a multi-walled carbon nanotube (MWCNT)-emeraldine base polyaniline (EBP)-Nafion (NA) composite modified glassy carbon electrode (MWCNT-EBP-NA/GCE) was prepared and used for the sensitive detection of trace Pb(II) and Cd(II), with a detection limit of 0.06 μg/L for Cd(II) and 0.08 μg/L for Pb(II) (S/N = 3), by square wave anodic stripping voltammetry (SWASV). A bismuth film was prepared through the in situ plating of bismuth on the MWCNT-EBP-NA/GCE. The morphologies and electrochemical properties of the modified electrode were characterized by SWASV, scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The parameters affecting the stripping current response were investigated and optimized. The formed MWCNTs in the composite film enlarged the specific surface area of the electrode and significantly promoted electron transferring, and the formed polyaniline (PANI) enhanced the ion-exchange capacity and prevented the macromolecules in real samples from absorbing onto the surface of the electrode. The presence of NA effectively increased the stability and adhesion of the composite film, enhanced the cation-exchange capacity and improved the ability to preconcentrate metal ions. Under the optimized conditions, a linear range of 1.0 to 50.0 μg/L was achieved for both metal ions, with a detection limit of 0.06 μg/L for Cd(II) and 0.08 μg/L for Pb(II) (S/N = 3), offering good repeatability. Finally, the Bi/MWCNT-EBP-NA/GCE was used for the

  17. EDTA modified glassy carbon electrode: Preparation and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Ustuendag, Zafer [Dumlupinar University, Faculty of Arts and Sciences, Department of Chemistry, Kuetahya (Turkey); Solak, Ali Osman [Ankara University, Faculty of Science, Department of Chemistry, Degol Street, Tandogan, 06100 Ankara (Turkey)], E-mail: osolak@science.ankara.edu.tr

    2009-11-01

    EDTA-phenoxyamide modified glassy carbon electrode (EDTA-GC) was prepared at a glassy carbon electrode by surface synthesis. In the first step, nitrophenyl was grafted to the glassy carbon (GC) surface via the electrochemical reduction of its tetraflouroborate diazonium salt. In the second step, nitrophenyl-modified electrode (NP-GC) was subjected to the cathodic potential scan to reduce the nitro to amine group. p-Aminophenyl modified glassy carbon electrode (AP-GC) was dipped into a EDTA solution containing 1-ethyl-3(3-(dimethlyamino)propyl)-carbodiimide (EDC) as an activating agent. Thus formed ((2-anilino-2-oxoethyl){l_brace}2-[bis(carboxymethyl)amino]-ethyl{r_brace}amino)acetic acid modified GC electrode was denoted as EDTA-GC and characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), ellipsometry and X-ray photoelectron spectroscopy (XPS). Complexation of the EDTA-GC surface with Pb{sup 2+} ions was investigated if this electrode could be used as a metal sensor.

  18. A study of nanostructured gold modified glassy carbon electrode for ...

    Indian Academy of Sciences (India)

    A nanostructured gold modified glassy carbon electrode (Aunano/GCE) was employed for the determination of trace chromium(VI). To prepare Aunano/GCE, the GCE was immersed into KAuCl4 solution and electrodeposition was conducted at the potential of -0.4 V (vs Ag/AgCl) for 600 s. Scanning electron microscopy ...

  19. NITROANILINE FILM-HOLE MODIFIED GLASSY CARBON ...

    African Journals Online (AJOL)

    substances (such as ascorbic acid, uric acid and so on) that exist together .... stirring the electrolytes in the cell, a small magnetic bar was used in BASi C3 ..... Stephen, A.; Narayanan, V. New electrochemical sensor based on Ni-doped .... Wang, Y.; Li, Y.; Tang, L.; Lu, J.; Li, J. Application of graphene-modified electrode for.

  20. Electrochemical Oxidation of Sulfamethazine on Multi-Walled Nanotube Film Coated Glassy Carbon Electrode

    Directory of Open Access Journals (Sweden)

    L. Fotouhi

    2014-04-01

    Full Text Available The electrochemical oxidation of sulfamethazine (SMZ has been studied at a multi-walled carbon nanotubes modified glassy carbon electrode (MWCNT-GCE by cyclic voltammetry. This modified electrode (MWCNT-GCE exhibited excellent electrocatalytic behavior toward the oxidation of SMZ as evidenced by the enhancement of the oxidation peak current and the shift in the anodic potential to less positive values (170 mV in comparison with the bare GCE. The formal potential, E0', of SMZ is pH dependent with a slope of 54 mV per unit of pH, close to the anticipated Nerstian value of 59 mV for a 2-electron and 2-proton oxidation process. A detailed analysis of cyclic voltammograms gave fundamental electrochemical parameters including the electroactive surface coverage (Г, the transfer coefficient (a, the heterogeneous rate constant (ks. Under the selected conditions, the peak current shows two dynamic linear ranges of 10-200 mM and 300-3000 mM with the detection limit of 6.1 mM. The method was successfully applied to analyze SMZ in serum sample

  1. Electrooxidation of Indomethacin at Multiwalled Carbon Nanotubes-Modified GCE and Its Determination in Pharmaceutical Dosage Form and Human Biological Fluids

    OpenAIRE

    Sataraddi, Sanjeevaraddi R.; Patil, Shreekant M.; Bagoji, Atmanand M.; Pattar, Vijay P.; Nandibewoor, Sharanappa T.

    2014-01-01

    A simple, rapid, selective, and sensitive electrochemical method for the direct determination of indomethacin was developed. The electrochemical behavior of indomethacin was carried at multiwalled carbon nanotube- (MWCNTs-) modified glassy carbon electrode (GCE). The cyclic voltammetric results indicated that MWCNT-modified glassy carbon electrode remarkably enhanced electrocatalytic activity towards the oxidation of indomethacin in slightly acidic solutions. It led to a considerable improvem...

  2. Electrochemical deposition of gold nanoparticles on carbon nanotube coated glassy carbon electrode for the improved sensing of tinidazole

    International Nuclear Information System (INIS)

    Shahrokhian, Saeed; Rastgar, Shokoufeh

    2012-01-01

    The electrochemical reduction of tinidazole (TNZ) is studied on gold-nanoparticle/carbon-nanotubes (AuNP/CNT) modified glassy carbon electrodes using the linear sweep voltammetry. An electrochemical procedure was used for the deposition of gold nanoparticles onto the carbon nanotube film pre-cast on a glassy carbon electrode surface. The resulting nanoparticles were characterized by scanning electron microscopy and cyclic voltammetry. The effect of the electrodeposition conditions, e.g., salt concentration and deposition time on the response of the electrode was studied. Also, the effect of experimental parameters, e.g., potential and time of accumulation, pH of the buffered solutions and the potential sweep rate on the response is examined. Under the optimal conditions, the modified electrode showed a wide linear response toward the concentration of TNZ in the range of 0.1–50 μM with a detection limit of 10 nM. The prepared electrode was successfully applied for the determination of TNZ in pharmaceutical and clinical samples.

  3. Modified glassy carbon electrodes based on carbon nanostructures for ultrasensitive electrochemical determination of furazolidone

    Energy Technology Data Exchange (ETDEWEB)

    Shahrokhian, Saeed, E-mail: shahrokhian@sharif.edu [Department of Chemistry, Sharif University of Technology, Tehran 11155-9516 (Iran, Islamic Republic of); Institute for Nanoscience and Nanotechnology, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Naderi, Leila [Department of Chemistry, Sharif University of Technology, Tehran 11155-9516 (Iran, Islamic Republic of); Ghalkhani, Masoumeh [Department of Chemistry, Faculty of Science, Shahid Rajaee Teacher Training University, Lavizan, Tehran (Iran, Islamic Republic of); Institute for advanced technology, Shahid Rajaee Teacher Training University, Lavizan, Tehran, 16788 (Iran, Islamic Republic of)

    2016-04-01

    The electrochemical behavior of Furazolidone (Fu) was investigated on the surface of the glassy carbon electrode modified with different carbon nanomaterials, including carbon nanotubes (CNTs), carbon nanoparticles (CNPs), nanodiamond-graphite (NDG), graphene oxide (GO), reduced graphene oxide (RGO) and RGO-CNT hybrids (various ratios) using linear sweep voltammetry (LSV). The results of voltammetric studies exhibited a considerable increase in the cathodic peak current of Fu at the RGO modified GCE, compared to other modified electrodes and also bare GCE. The surface morphology and nature of the RGO film was thoroughly characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. The modified electrode showed two linear dynamic ranges of 0.001–2.0 μM and 2.0–10.0 μM with a detection limit of 0.3 nM for the voltammetric determination of Fu. This sensor was used successfully for Fu determination in pharmaceutical and clinical preparations. - Highlights: • The electrochemical behavior of Furazolidone (Fu) was investigated on the surface of the modified electrode with different carbon nanomaterials by Linear sweep voltammetry. • Two linear dynamic ranges and a low detection limit were obtained. • The modified electrode was applied for the detection of Fu in pharmaceutical and clinical preparations.

  4. Study on electroactive and electrocatalytic surfaces of single walled carbon nanotube-modified electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Salinas-Torres, David [Departamento de Quimica Fisica and Instituto Universitario de Materiales de Alicante, Universidad de Alicante, Apdo. de Correos 99, E-03080 Alicante (Spain); Huerta, Francisco [Departamento de Ingenieria Textil y Papelera, Universidad Politecnica de Valencia, Plaza Ferrandiz y Carbonell, 1. E-03801 Alcoy (Spain); Montilla, Francisco, E-mail: francisco.montilla@ua.e [Departamento de Quimica Fisica and Instituto Universitario de Materiales de Alicante, Universidad de Alicante, Apdo. de Correos 99, E-03080 Alicante (Spain); Morallon, Emilia [Departamento de Quimica Fisica and Instituto Universitario de Materiales de Alicante, Universidad de Alicante, Apdo. de Correos 99, E-03080 Alicante (Spain)

    2011-02-01

    An investigation of the electrocatalysis of single-walled carbon nanotubes modified electrodes has been performed in this work. Nanotube-modified electrodes present a surface area much higher than the bare glassy carbon surfaces as determined by capacitance measurements. Several redox probes were selected for checking the reactivity of specific sites at the carbon nanotube surface. The presence of carbon nanotubes on the electrode improves the kinetics for all the reactions studied compared with the bare glassy carbon electrode with variations of the heterogeneous electron transfer rate constant up to 5 orders of magnitude. The most important effects are observed for the benzoquinone/hydroquinone and ferrocene/ferricinium redox couples, which show a remarkable improvement of their electron transfer kinetics on SWCNT-modified electrodes, probably due to strong {pi}-{pi} interaction between the organic molecules and the walls of the carbon nanotubes. For many of the reactions studied, less than 1% of the nanotube-modified electrode surface is transferring charge to species in solution. This result suggests that only nanotube tips are active sites for the electron transfer in such cases. On the contrary, the electroactive surface for the reactions of ferrocene and quinone is higher indicating that the electron transfer is produced also from the nanotube walls.

  5. Study on electroactive and electrocatalytic surfaces of single walled carbon nanotube-modified electrodes

    International Nuclear Information System (INIS)

    Salinas-Torres, David; Huerta, Francisco; Montilla, Francisco; Morallon, Emilia

    2011-01-01

    An investigation of the electrocatalysis of single-walled carbon nanotubes modified electrodes has been performed in this work. Nanotube-modified electrodes present a surface area much higher than the bare glassy carbon surfaces as determined by capacitance measurements. Several redox probes were selected for checking the reactivity of specific sites at the carbon nanotube surface. The presence of carbon nanotubes on the electrode improves the kinetics for all the reactions studied compared with the bare glassy carbon electrode with variations of the heterogeneous electron transfer rate constant up to 5 orders of magnitude. The most important effects are observed for the benzoquinone/hydroquinone and ferrocene/ferricinium redox couples, which show a remarkable improvement of their electron transfer kinetics on SWCNT-modified electrodes, probably due to strong π-π interaction between the organic molecules and the walls of the carbon nanotubes. For many of the reactions studied, less than 1% of the nanotube-modified electrode surface is transferring charge to species in solution. This result suggests that only nanotube tips are active sites for the electron transfer in such cases. On the contrary, the electroactive surface for the reactions of ferrocene and quinone is higher indicating that the electron transfer is produced also from the nanotube walls.

  6. Electrochemical determination of mesotrione at organoclay modified glassy carbon electrodes.

    Science.gov (United States)

    Kamga Wagheu, Josephine; Forano, Claude; Besse-Hoggan, Pascale; Tonle, Ignas K; Ngameni, Emmanuel; Mousty, Christine

    2013-01-15

    A natural Cameroonian smectite-type clay (SaNa) was exchanged with cationic surfactants, namely cetyltrimethylammonium (CTA) and didodecyldimethyl ammonium (DDA) modifying its physico-chemical properties. The resulting organoclays that have higher adsorption capacity for mesotrione than the pristine SaNa clay, have been used as modifiers of glassy carbon electrode for the electrochemical detection of this herbicide by square wave voltammetry. The stripping performances of SaNa, SaCTA and SaDDA modified electrodes were therefore evaluated and the experimental parameters were optimized. SaDDA gives the best results in deoxygenated acetate buffer solution (pH 6.0) after 2 min accumulation under open circuit conditions. Under optimal conditions, the reduction current is proportional to mesotrione concentration in the range from 0.25 to 2.5 μM with a detection limit of 0.26 μM. The fabricated electrode was also applied for the commercial formulation CALLISTO, used in European maize market. Copyright © 2012 Elsevier B.V. All rights reserved.

  7. Chemical attachment of functionalized multiwalled carbon nanotubes on glassy carbon electrode for electrocatalytic application

    International Nuclear Information System (INIS)

    Rajalakshmi, K.; Abraham John, S.

    2015-01-01

    Highlights: • FMWCNTs were covalently attached on GC surface with the aid of alkyldiamine. • The attached FMWCNTs were stable for a wide potential window due to the robust C−N bond. • The composite electrode was prepared by electropolymerizing thiadiazole on FMWCNTs. • The detection limit of 0.27 μM (S/N = 3) of GMP was achieved using composite modified electrode. - Abstract: The covalent attachment of acid functionalized multiwalled carbon nanotubes (FMWCNTs) on glassy carbon (GC) electrode using 1,8-octanediamine (OD) as a linker via carbodiimide chemistry was described. The attachment of FMWCNTs on GC electrode were confirmed by attenuated total reflectance Fourier transform infra-red (ATR-FT-IR) spectroscopy, Raman, scanning electron microscopy (SEM) and electrochemical impedance studies. Raman spectrum of FMWCNTs modified surface shows the characteristic G and D bands at 1563 cm −1 and 1340 cm −1 , respectively. This confirmed the successful attachment of FMWCNTs on the OD modified GC surface. Further, the attachment of FMWCNTs on OD modified surface via amide linkage was confirmed from the observed characteristic peak at 1681 cm −1 in the ATR-FT-IR spectrum. The SEM images showed that the covalently attached FMWCNTs retained their morphology similar to powder and the average diameter of them was found to be 58 nm. Unlike modification of FMWCNTs on gold substrates with the aid of conventional thiol linkers (Au−S bond), modification of them by the present method was stable for a wide positive potential window due to the robust C−N bond. To demonstrate the electrochemical stability of the MWCNTs modified electrode at more positive potential, guanosine 5′-monophosphate (GMP) was selected as a representative probe because its oxidation occurs at more than 1 V. It was found that the FMWCNTs modified electrode not only showed a stable signal for GMP but also enhanced its oxidation current when compared to bare GC electrode. Further, the

  8. Modified glassy carbon electrodes based on carbon nanostructures for ultrasensitive electrochemical determination of furazolidone.

    Science.gov (United States)

    Shahrokhian, Saeed; Naderi, Leila; Ghalkhani, Masoumeh

    2016-04-01

    The electrochemical behavior of Furazolidone (Fu) was investigated on the surface of the glassy carbon electrode modified with different carbon nanomaterials, including carbon nanotubes (CNTs), carbon nanoparticles (CNPs), nanodiamond-graphite (NDG), graphene oxide (GO), reduced graphene oxide (RGO) and RGO-CNT hybrids (various ratios) using linear sweep voltammetry (LSV). The results of voltammetric studies exhibited a considerable increase in the cathodic peak current of Fu at the RGO modified GCE, compared to other modified electrodes and also bare GCE. The surface morphology and nature of the RGO film was thoroughly characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. The modified electrode showed two linear dynamic ranges of 0.001-2.0 μM and 2.0-10.0 μM with a detection limit of 0.3 nM for the voltammetric determination of Fu. This sensor was used successfully for Fu determination in pharmaceutical and clinical preparations. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Electrocatalytic Determination of Isoniazid by a Glassy Carbon Electrode Modified with Poly (Eriochrome Black T)

    OpenAIRE

    Karim Asadpour-Zeynali; Venus Baghalabadi

    2017-01-01

    In this work poly eriochrome black T (EBT) was electrochemically synthesized on the glassy carbon electrode as electrode modifier. On the modified electrode, voltammetric behavior of isoniazid (INH) was investigated. The poly (EBT)-modified glassy carbon electrode has excellent electrocatalytic ability for the electrooxidation of isoniazid. This fact was appeared as a reduced overpotential of INH oxidation in a wide operational pH range from 2 to 13. It has been found that the catalytic peak ...

  10. Electrochemical determination of serotonin in urine samples based on metal oxide nanoparticles/MWCNT on modified glassy carbon electrode

    Directory of Open Access Journals (Sweden)

    Omolola E. Fayemi

    2017-04-01

    Full Text Available The electrochemical response of serotonin on the modified electrode based on multiwalled-carbon-nanotube (MWCNT doped respectively with nickel, zinc and iron oxide nanoparticles coating on glassy carbon electrode (GCE at physiological pH 7 was determined using cyclic voltammetry (CV and square wave voltammetry (SWV. The modified GCE/MWCNT-metal oxide electrodes exhibited excellent electrocatalytic activity towards the detection of serotonin at large peak current and lower oxidation potentials compared to other electrodes investigated. The dynamic range for the serotonin determination was between 5.98 × 10−3 μM to 62.8 μM with detection limits 118, 129 and 166 nM for GCE/MWCNT-NiO, GCE/MWCNT-ZnO and GCE/MWCNT-Fe3O4 sensors respectively. GCE-MWCNT-NiO was the best electrode in terms of serotonin current response, electrode stability, resistance to fouling and limit of detection towards the analyte. The developed sensors were found to be electrochemically stable, reusable, economically effective due to their extremely low operational cost, and have demonstrated good limit of detection, sensitivity and selectivity towards serotonin determination in urine samples. Keywords: Metal oxides nanoparticles, Multiwalled carbon nanotubes, Glassy carbon electrode, Serotonin, Cyclic voltammetry, Square wave voltammetry

  11. ELECTROCATALYTIC ACTIVITY FOR O2 REDUCTION OF UNSUBSTITUTED AND PERCHLORINATED IRON PHTHALOCYANINES ADSORBED ON AMINO-TERMINATED MULTIWALLED CARBON NANOTUBES DEPOSITED ON GLASSY CARBON ELECTRODES

    OpenAIRE

    CAÑETE, PAULINA; SILVA, J. FRANCISCO; ZAGAL, JOSÉ H

    2014-01-01

    Amino-functionalized multiwalled carbon nanotubes (MWCNT-NH2) were modified with Fe phthalocyanine (FePc) and perchlorinated Fe phthalocyanine (16(Cl)FePc) and deposited on glassy carbon electrodes (GCE). The electrocatalytic activity of these hybrid electrodes was examined for the reduction of molecular oxygen in alkaline media (0.2 M NaOH) using stationary and rotating disk electrodes. Electrodes containing 16(Cl)FePc are more active than those containing FePc. Electrodes containing CNTs ar...

  12. Electrochemical Determination of Caffeine Content in Ethiopian Coffee Samples Using Lignin Modified Glassy Carbon Electrode

    OpenAIRE

    Amare, Meareg; Aklog, Senait

    2017-01-01

    Lignin film was deposited at the surface of glassy carbon electrode potentiostatically. In contrast to the unmodified glassy carbon electrode, an oxidative peak with an improved current and overpotential for caffeine at modified electrode showed catalytic activity of the modifier towards oxidation of caffeine. Linear dependence of peak current on caffeine concentration in the range 6 ? 10?6 to 100 ? 10?6?mol?L?1 with determination coefficient and method detection limit (LoD = 3?s/slope) of 0....

  13. Carbon nanofiber vs. carbon microparticles as modifiers of glassy carbon and gold electrodes applied in electrochemical sensing of NADH.

    Science.gov (United States)

    Pérez, Briza; Del Valle, Manel; Alegret, Salvador; Merkoçi, Arben

    2007-12-15

    Carbon materials (CMs), such as carbon nanotubes (CNTs), carbon nanofibers (CNFs), and carbon microparticles (CMPs) are used as doping materials for electrochemical sensors. The efficiency of these materials (either before or after acidic treatments) while being used as electrocatalysts in electrochemical sensors is discussed for beta-nicotinamide adenine dinucleotide (NADH) detection using cyclic voltammetry (CV). The sensitivity of the electrodes (glassy carbon (GC) and gold (Au)) modified with both treated and untreated materials have been deeply studied. The response efficiencies of the GC and Au electrodes modified with CNF and CMP, using dimethylformamide (DMF) as dispersing agent are significantly different due to the peculiar physical and chemical characteristics of each doping material. Several differences between the electrocatalytic activities of CMs modified electrodes upon NADH oxidation have been observed. The CNF film promotes better the electron transfer of NADH minimizing the oxidation potential at +0.352 V. Moreover higher currents for the NADH oxidation peak have been observed for these electrodes. The shown differences in the electrochemical reactivities of CNF and CMP modified electrodes should be with interest for future applications in biosensors.

  14. Electrochemical Effect of Different Modified Glassy Carbon Electrodes on the Values of Diffusion Coefficient for Some Heavy Metal Ions

    International Nuclear Information System (INIS)

    Radhi, M M; Alwan, S H; Amir, Y K A; Tee, T W

    2013-01-01

    Glassy carbon electrode (GCE) was modified with carbon nanotubes (CNT), C 60 and activated carbon (AC) by mechanical attachment method and solution evaporation technique to preparation CNT/GCE, C 60 /GCE and AC/GCE, these electrodes were modified in Li + solution via cyclic voltammetry (CV) potential cycling to preparing CNT/Li + /GCE, C 60 /Li + /GCE and AC/Li + /GCE. The sensing characteristics of the modified film electrodes, demonstrated in the application study for different heavy metal ions such as Hg 2+ , Cd 2+ , and Mn 2+ . Cyclic voltammetric effect by chronoamperometry (CA) technique was investigated to determination the diffusion coefficient (D f ) values from Cottrell equation at these ions. Based on Cottrell equation (diffusion coefficient) of the redox current peaks of different heavy metal ions at different modified electrodes were studied to evaluate the sensing of these electrodes by the diffusion coefficient values. The modification of GCE with nano materials and Li + act an enhancement for the redox current peaks to observe that the diffusion process are high at CNT/Li + /GCE, C 60 /Li + /GCE and AC/Li+/GCE, but it has low values at unmodified GCE.

  15. Electrocatalytic oxidation of hydrazine at overoxidized polypyrrole film modified glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Majidi, Mir Reza [Department of Analytical Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz 51664 (Iran, Islamic Republic of); Jouyban, Abolghasem [Faculty of Pharmacy and Drug Applied Research Center, Tabriz University of Medical Sciences, Tabriz 51664 (Iran, Islamic Republic of); Asadpour-Zeynali, Karim [Department of Analytical Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz 51664 (Iran, Islamic Republic of)]. E-mail: asadpour@tabrizu.ac.ir

    2007-06-20

    Electrocatalytic oxidation of hydrazine (HZ) was studied on an overoxidized polypyrrole (OPPy) modified glassy carbon electrode using cyclic voltammetry and chronoamperometry techniques. The OPPy-modified glassy carbon electrode has very high catalytic ability for electrooxidation of HZ, which appeared as a reduced overpotential in a wide operational pH range of 5-10. The overall numbers of electrons involved in the catalytic oxidation of HZ, the number of electrons involved in the rate-determining and diffusion coefficient of HZ were estimated using cyclic voltammetry and chronoamperometry. It has been shown that using the OPPy-modified electrode, HZ can be determined by cyclic voltammetry and amperometry with limit of detection 36 and 3.7 {mu}M, respectively. The results of the analysis suggest that the proposed method promises accurate results and could be employed for the routine determination of HZ.

  16. Modification of glassy carbon electrode with a bilayer of multiwalled carbon nanotube/tiron-doped polypyrrole: Application to sensitive voltammetric determination of acyclovir

    Energy Technology Data Exchange (ETDEWEB)

    Shahrokhian, Saeed, E-mail: shahrokhian@sharif.edu [Department of Chemistry, Sharif University of Technology, Tehran 11155-3516 (Iran, Islamic Republic of); Institute for Nanoscience and Technology, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Azimzadeh, Mahnaz [Department of Chemistry, Sharif University of Technology, Tehran 11155-3516 (Iran, Islamic Republic of); Amini, Mohammad K. [Department of Chemistry, Isfahan University, Isfahan (Iran, Islamic Republic of)

    2015-08-01

    A novel voltammetric sensor based on glassy carbon electrode (GCE) modified with a thin film of multi-walled carbon nanotubes (MWCNTs) coated with an electropolymerized layer of tiron-doped polypyrrole was developed and the resulting electrode was applied for the determination of acyclovir (ACV). The surface morphology and property of the modified electrode were characterized by field emission scanning electron microscopy and electrochemical impedance spectroscopy techniques. The electrochemical performance of the modified electrode was investigated by means of linear sweep voltammetry (LSV). The effect of several experimental variables, such as pH of the supporting electrolyte, drop size of the cast MWCNTssuspension, number of electropolymerization cycles and accumulation time was optimized by monitoring the LSV response of the modified electrode toward ACV. The best response was observed at pH 7.0 after accumulation at open circuit for 160 s. Under the optimized conditions, a significant electrochemical improvement was observed toward the electrooxidation of ACV on the modified electrode surface relative to the bare GCE, resulting in a wide linear dynamic range (0.03–10.0 μM) and a low detection limit (10.0 nM) for ACV. Besides high sensitivity, the sensor represented high stability and good reproducibility for ACV analysis, and provided satisfactory results for the determination of this compound in pharmaceutical and clinical preparations. - Highlights: • A simple method was employed to construct a thin film modified electrode. • Tiron-doped polypyrrole was electropolymerized on MWCNT precast glassy carbon electrode. • Electrode surface characterization was performed by microscopic and spectroscopic techniques. • The modified electrode showed nano-molar detection limit for acyclovir. • The modified electrode was applied for the detection of ACV in pharmaceutical and clinical preparations.

  17. Adsorptive stripping differential pulse voltammetric determination of venlafaxine and desvenlafaxine employing Nafion-carbon nanotube composite glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Sanghavi, Bankim J. [Department of Chemistry, University of Mumbai, Vidyanagari, Santacruz (East), Mumbai 400 098, Maharashtra (India); Srivastava, Ashwini K., E-mail: aksrivastava@chem.mu.ac.i [Department of Chemistry, University of Mumbai, Vidyanagari, Santacruz (East), Mumbai 400 098, Maharashtra (India)

    2011-04-15

    A Nafion-carbon nanotube-modified glassy carbon electrode (NAF-CNT-GCE) was developed for the determination of venlafaxine (VF) and desvenlafaxine (DVF). The electrochemical behavior of both these molecules was investigated employing cyclic voltammetry (CV), chronocoulometry (CC), electrochemical impedance spectroscopy (EIS) and adsorptive stripping differential pulse voltammetry (AdSDPV). The surface morphology of the electrodes has been studied by means of scanning electron microscopy (SEM). These studies revealed that the oxidation of VF and DVF is facilitated at NAF-CNT-GCE. After optimization of analytical conditions employing this electrode at pH 7.0 in Britton-Robinson buffer (0.05 M) for VF and pH 5.0 in acetate buffer (0.1 M) for DVF, the peak currents for both the molecules were found to vary linearly with their concentrations in the range of 3.81 x 10{sup -8}-6.22 x 10{sup -5} M for VF and 5.33 x 10{sup -8}-3.58 x 10{sup -5} M for DVF. The detection limits (S/N = 3) of 1.24 x 10{sup -8} and 2.11 x 10{sup -8} M were obtained for VF and DVF, respectively, using AdSDPV. The prepared modified electrode showed several advantages, such as simple preparation method, high sensitivity, very low detection limits and excellent reproducibility. The proposed method was employed for the determination of VF and DVF in pharmaceutical formulations, urine and blood serum samples.

  18. Electrochemically modified sulfisoxazole nanofilm on glassy carbon for determination of cadmium(II) in water samples

    International Nuclear Information System (INIS)

    Gupta, Vinod Kumar; Yola, Mehmet Lütfi; Atar, Necip; Solak, Ali Osman; Uzun, Lokman; Üstündağ, Zafer

    2013-01-01

    Highlights: • Sulfisoxazole was grafted onto glassy carbon electrode. • The electrode was characterized by spectroscopic and electrochemical methods. • It has been used for the determination of Cd(II) ions in real samples in very low concentrations. -- Abstract: Sulfisoxazole (SO) was grafted to glassy carbon electrode (GCE) via the electrochemical oxidation of SO in acetonitrile solution containing 0.1 M tetrabutylammoniumtetra-fluoroborate (TBATFB). The prepared electrode was characterized by using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), reflection–absorption infrared spectroscopy (RAIRS) and X-ray photoelectron spectroscopy (XPS). The ellipsometric thickness of SO nanofilm at the glassy carbon surface was obtained as 14.48 ± 0.11 nm. The stability of the SO modified GCE was studied. The SO modified GCE was also utilized for the determination of Cd(II) ions in water samples in the presence of Pb(II) and Fe(II) by adsorptive stripping voltammetry. The linearity range and the detection limit of Cd(II) ions were 1.0 × 10 −10 to 5.0 × 10 −8 M and 3.3 × 10 −11 M (S/N = 3), respectively

  19. Gold nanoparticles directly modified glassy carbon electrode for non-enzymatic detection of glucose

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Gang; Shu, Honghui; Ji, Kai [Ministry-of-Education Key Laboratory for the Green Preparation and Application of Functional Materials, Faculty of Materials Science and Engineering, Hubei University, No. 368 Youyi Avenue, Wuchang, Wuhan 430062 (China); Oyama, Munetaka [Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8520 (Japan); Liu, Xiong [Ministry-of-Education Key Laboratory for the Green Preparation and Application of Functional Materials, Faculty of Materials Science and Engineering, Hubei University, No. 368 Youyi Avenue, Wuchang, Wuhan 430062 (China); He, Yunbin, E-mail: ybhe@hubu.edu.cn [Ministry-of-Education Key Laboratory for the Green Preparation and Application of Functional Materials, Faculty of Materials Science and Engineering, Hubei University, No. 368 Youyi Avenue, Wuchang, Wuhan 430062 (China)

    2014-01-01

    This work describes controllable preparation of gold nanoparticles on glassy carbon electrodes by using the seed mediated growth method, which contains two steps, namely, nanoseeds attachment and nanocrystals growth. The size and the dispersion of gold nanoparticles grown on glassy carbon electrodes could be easily tuned through the growth time based on results of field-emission scanning electron microscopy. Excellent electrochemical catalytic characteristics for glucose oxidation were observed for the gold nanoparticles modified glassy carbon electrodes (AuNPs/GC), resulting from the extended active surface area provided by the dense gold nanoparticles attached. It exhibited a wide linear range from 0.1 mM to 25 mM with the sensitivity of 87.5 μA cm{sup −2} mM{sup −1} and low detection limit down to 0.05 mM for the sensing of glucose. The common interfering species such as chloride ion, ascorbic acid, uric acid and 4-acetamidophenol were verified having no interference effect on the detection of glucose. It is demonstrated that the seed mediated method is one of the facile approaches for fabricating Au nanoparticles modified substrates, which could work as one kind of promising electrode materials for the glucose nonenzymatic sensing.

  20. Electrocatalytic performance of Pu(IV)/Pu(III) redox reaction at graphene modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Gupta, Ruma; Gamare, J.S.; Kamat, J.V.; Aggarwal, S.K.

    2014-01-01

    In this paper we explore the analytical perspectives of graphene modified electrode utilising commercially available graphene, which is well characterised, completely free from surfactants and has not been purposely oxidised or treated. We compare and critically contrast the electro-analytical performance of graphene modified glassy carbon electrodes (Gr/GC) with that of unmodified GC electrode towards Pu(IV)/Pu(III) redox reaction, monitoring of which has considerable importance in a plethora of areas where electrochemistry is conveniently and beneficially utilised for determination of nuclear fuels

  1. Electrochemical behavior of cysteine at a CuGeO3 nanowires modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Dong Yongping; Pei Lizhai; Chu Xiangfeng; Zhang Wangbing; Zhang Qianfeng

    2010-01-01

    A CuGeO 3 nanowire modified glassy carbon electrode was fabricated and characterized by scanning electron microscopy. The results of electrochemical impedance spectroscopy reveal that electron transfer through nanowire film is facile compared with that of bare glassy carbon electrode. The modified electrode exhibited a novel electrocatalytic behavior to the electrochemical reactions of L-cysteine in neutral solution, which was not reported previously. Two pairs of semi-reversible electrochemical peaks were observed and assigned to the processes of oxidation/reduction and adsorption/desorption of cysteine at the modified electrode, respectively. The electrochemical response of cysteine is poor in alkaline condition and is enhanced greatly in acidic solution, suggesting that hydrogen ions participate in the electrochemical oxidation process of cysteine. The intensities of two anodic peaks varied linearly with the concentration of cysteine in the range of 1 x 10 -6 to 1 x 10 -3 mol L -1 , which make it possible to sensitive detection of cysteine with the CuGeO 3 nanowire modified electrode. Furthermore, the modified electrode exhibited good reproducibility and stability.

  2. Comparison of impedimetric detection of DNA hybridization on the various biosensors based on modified glassy carbon electrodes with PANHS and nanomaterials of RGO and MWCNTs.

    Science.gov (United States)

    Benvidi, Ali; Tezerjani, Marzieh Dehghan; Jahanbani, Shahriar; Mazloum Ardakani, Mohammad; Moshtaghioun, Seyed Mohammad

    2016-01-15

    In this research, we have developed lable free DNA biosensors based on modified glassy carbon electrodes (GCE) with reduced graphene oxide (RGO) and carbon nanotubes (MWCNTs) for detection of DNA sequences. This paper compares the detection of BRCA1 5382insC mutation using independent glassy carbon electrodes (GCE) modified with RGO and MWCNTs. A probe (BRCA1 5382insC mutation detection (ssDNA)) was then immobilized on the modified electrodes for a specific time. The immobilization of the probe and its hybridization with the target DNA (Complementary DNA) were performed under optimum conditions using different electrochemical techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The proposed biosensors were used for determination of complementary DNA sequences. The non-modified DNA biosensor (1-pyrenebutyric acid-N- hydroxysuccinimide ester (PANHS)/GCE), revealed a linear relationship between ∆Rct and logarithm of the complementary target DNA concentration ranging from 1.0×10(-16)molL(-1) to 1.0×10(-10)mol L(-1) with a correlation coefficient of 0.992, for DNA biosensors modified with multi-wall carbon nanotubes (MWCNTs) and reduced graphene oxide (RGO) wider linear range and lower detection limit were obtained. For ssDNA/PANHS/MWCNTs/GCE a linear range 1.0×10(-17)mol L(-1)-1.0×10(-10)mol L(-1) with a correlation coefficient of 0.993 and for ssDNA/PANHS/RGO/GCE a linear range from 1.0×10(-18)mol L(-1) to 1.0×10(-10)mol L(-1) with a correlation coefficient of 0.985 were obtained. In addition, the mentioned biosensors were satisfactorily applied for discriminating of complementary sequences from noncomplementary sequences, so the mentioned biosensors can be used for the detection of BRCA1-associated breast cancer. Copyright © 2015. Published by Elsevier B.V.

  3. Norepinephrine-modified glassy carbon electrode for the simultaneous determination of ascorbic acid and uric acid

    International Nuclear Information System (INIS)

    Zare, H.R.; Memarzadeh, F.; Ardakani, M. Mazloum; Namazian, M.; Golabi, S.M.

    2005-01-01

    The oxidation of norepinephrine (NE) on a preactivated glassy carbon electrode leads to the formation of a deposited layer of about 4.2 x 10 -10 mol cm -2 at the surface of the electrode. The electron transfer rate constant, k s , and charge transfer coefficient, α, for electron transfer between the electrode and immobilized NE film were calculated as 44 s -1 and 0.46, respectively. The NE-modified glassy carbon electrode exhibited good electrocatalytic properties towards ascorbic acid (AA) oxidation in phosphate buffer (pH 7.0) with an overpotential of about 475 mV lower than that of the bare electrode. The electrocatalytic response was evaluated by cyclic voltammetry, chronoamperometry, amperometry and rotating disk voltammetry. The overall number of electrons involved in the catalytic oxidation of AA and the number of electrons involved in the rate-determining step are 2 and 1, respectively. The rate constant for the catalytic oxidation of AA was evaluated by RDE voltammetry and an average value of k h was found to be 8.42 x 10 3 M -1 s -1 . Amperometric determination of AA in stirred solution exhibits a linear range of 2.0-1300.0 μM (correlation coefficient 0.9999) and a detection limit of 0.076 μM. The precision of amperometry was found to be 1.9% for replicate determination of a 49.0 μM solution of AA (n = 6). In differential pulse voltammetric measurements, the NE-modified glassy carbon electrode can separate the AA and uric acid (UA) signals. Ascorbic acid oxidizes at more negative potential than UA. Also, the simultaneous determination of UA and AA is achieved at the NE-modified electrode

  4. Electrocatalytic Determination of Isoniazid by a Glassy Carbon Electrode Modified with Poly (Eriochrome Black T

    Directory of Open Access Journals (Sweden)

    Karim Asadpour-Zeynali

    2017-06-01

    Full Text Available In this work poly eriochrome black T (EBT was electrochemically synthesized on the glassy carbon electrode as electrode modifier. On the modified electrode, voltammetric behavior of isoniazid (INH was investigated. The poly (EBT-modified glassy carbon electrode has excellent electrocatalytic ability for the electrooxidation of isoniazid. This fact was appeared as a reduced overpotential of INH oxidation in a wide operational pH range from 2 to 13. It has been found that the catalytic peak current depends on the concentration of INH and solution pH. The number of electrons involved in the rate determining step was found 1. The diffusion coefficient of isoniazid was also estimated using chronoamperometry technique. The experimental results showed that the mediated oxidation peak current of isoniazid is linearly dependent on the concentration of isoniazid in the ranges of 8.0 × 10-6 – 1.18 × 10-3 M and 2.90 × 10-5 M – 1.67× 10-3 M with differential pulse voltammetry (DPV and amperometry methods, respectively. The detection limits (S/N = 3 were found to be 6.0 μM and 16.4 μM by DPV and amperometry methods, respectively. This developed method was applied to the determination of isoniazid in tablet samples with satisfactory results.

  5. Annealing effect on thermal conductivity and microhardness of carbon nanotube containing Se80Te16Cu4 glassy composites

    Science.gov (United States)

    Upadhyay, A. N.; Tiwari, R. S.; Singh, Kedar

    2018-02-01

    This study deals with the effect of thermal annealing on structural/microstructural, thermal and mechanical behavior of pristine Se80Te16Cu4 and carbon nanotubes (CNTs) containing Se80Te16Cu4 glassy composites. Pristine Se80Te16Cu4, 3 and 5 wt%CNTs-Se80Te16Cu4 glassy composites are annealed in the vicinity of glass transition temperature to onset crystallization temperature (340-380 K). X-ray diffraction (XRD) pattern revealed formation of polycrystalline phases of hexagonal CuSe and trigonal selenium. The indexed d-values in XRD patterns are in well conformity with the d-values obtained after the indexing of the ring pattern of selected area electron diffraction pattern of TEM images. The SEM investigation exhibited that the grain size of the CNTs containing Se80Te16Cu4 glassy composites increased with increasing annealing temperature and decreased at further higher annealing temperature. Thermal conductivity, microhardness exhibited a substantial increase with increasing annealing temperature of 340-360 K and slightly decreases for 380 K. The variation of thermal conductivity and microhardness can be explained by cross-linking formation and voids reduction.

  6. Electrochemical determination of ascorbic acid at p-phenylenediamine film-holes modified glassy carbon electrode

    Directory of Open Access Journals (Sweden)

    Olana Bikila Nagasa

    2015-01-01

    Full Text Available In this work the determination of ascorbic acid (AA at glassy carbon electrode (GCE modified with a perforated film produced by reduction of diazonium generated in situ from p-phenylenediamine (PD is reported. Holes were intentionally created in the modifier film by stripping a pre-deposited gold nanoparticles. The modified electrodes were electrochemically characterized by common redox probes: hydroquinone, ferrocyanide and hexamineruthenium(III. The cyclic voltammetric and amperometric response of AA using the modified electrodes was compared with that of bare GCE. The bare GCE showed a linear response to AA in the concentration range of 5 mM to 45 mM with detection limit of 1.656 mM and the modified GCE showed a linear response to AA in the concentration range of 5 μM to 45 μM with detection limit of 0.123 μM. The effect of potential intereferents on amperometric signal of AA at the modified GCE was examined and found to be minimal. The inter-electrode reproducibility, stability, and accuracy were determined. The modified electrode showed excellent inter-electrode reproducibility, accuracy and stability. The modified electrode reported is a promising candidate for use in electroanalysis of AA.

  7. Electrochemical impedance-based DNA sensor using a modified single walled carbon nanotube electrode

    Energy Technology Data Exchange (ETDEWEB)

    Weber, Jessica E. [Department of Mechanical Engineering, University of South Florida, Tampa, FL (United States); Nanomaterials and Nanomanufacturing Research Center, University of South Florida, Tampa, FL (United States); Pillai, Shreekumar [Center for NanoBiotechnology Research, Alabama State University, Montgomery, AL (United States); Ram, Manoj Kumar, E-mail: mkram@usf.edu [Department of Mechanical Engineering, University of South Florida, Tampa, FL (United States); Nanomaterials and Nanomanufacturing Research Center, University of South Florida, Tampa, FL (United States); Kumar, Ashok [Department of Mechanical Engineering, University of South Florida, Tampa, FL (United States); Nanomaterials and Nanomanufacturing Research Center, University of South Florida, Tampa, FL (United States); Singh, Shree R. [Center for NanoBiotechnology Research, Alabama State University, Montgomery, AL (United States)

    2011-07-20

    Carbon nanotubes have become promising functional materials for the development of advanced electrochemical biosensors with novel features which could promote electron-transfer with various redox active biomolecules. This paper presents the detection of Salmonella enterica serovar Typhimurium using chemically modified single walled carbon nanotubes (SWNTs) with single stranded DNA (ssDNA) on a polished glassy carbon electrode. Hybridization with the corresponding complementary ssDNA has shown a shift in the impedance studies due to a higher charge transfer in ssDNA. The developed biosensor has revealed an excellent specificity for the appropriate targeted DNA strand. The methodologies to prepare and functionalize the electrode could be adopted in the development of DNA hybridization biosensor.

  8. Electrochemical Determination of Caffeine Content in Ethiopian Coffee Samples Using Lignin Modified Glassy Carbon Electrode

    Directory of Open Access Journals (Sweden)

    Meareg Amare

    2017-01-01

    Full Text Available Lignin film was deposited at the surface of glassy carbon electrode potentiostatically. In contrast to the unmodified glassy carbon electrode, an oxidative peak with an improved current and overpotential for caffeine at modified electrode showed catalytic activity of the modifier towards oxidation of caffeine. Linear dependence of peak current on caffeine concentration in the range 6×10-6 to 100×10-6 mol L−1 with determination coefficient and method detection limit (LoD = 3 s/slope of 0.99925 and 8.37×10-7 mol L−1, respectively, supplemented by recovery results of 93.79–102.17% validated the developed method. An attempt was made to determine the caffeine content of aqueous coffee extracts of Ethiopian coffees grown in four coffee cultivating localities (Wonbera, Wolega, Finoteselam, and Zegie and hence to evaluate the correlation between users preference and caffeine content. In agreement with reported works, caffeine contents (w/w% of 0.164 in Wonbera coffee; 0.134 in Wolega coffee; 0.097 in Finoteselam coffee; and 0.089 in Zegie coffee were detected confirming the applicability of the developed method for determination of caffeine in a complex matrix environment. The result indicated that users’ highest preference for Wonbera and least preference for Zegie cultivated coffees are in agreement with the caffeine content.

  9. Electrochemical Determination of Caffeine Content in Ethiopian Coffee Samples Using Lignin Modified Glassy Carbon Electrode.

    Science.gov (United States)

    Amare, Meareg; Aklog, Senait

    2017-01-01

    Lignin film was deposited at the surface of glassy carbon electrode potentiostatically. In contrast to the unmodified glassy carbon electrode, an oxidative peak with an improved current and overpotential for caffeine at modified electrode showed catalytic activity of the modifier towards oxidation of caffeine. Linear dependence of peak current on caffeine concentration in the range 6 × 10 -6 to 100 × 10 -6  mol L -1 with determination coefficient and method detection limit (LoD = 3 s/slope) of 0.99925 and 8.37 × 10 -7  mol L -1 , respectively, supplemented by recovery results of 93.79-102.17% validated the developed method. An attempt was made to determine the caffeine content of aqueous coffee extracts of Ethiopian coffees grown in four coffee cultivating localities (Wonbera, Wolega, Finoteselam, and Zegie) and hence to evaluate the correlation between users preference and caffeine content. In agreement with reported works, caffeine contents (w/w%) of 0.164 in Wonbera coffee; 0.134 in Wolega coffee; 0.097 in Finoteselam coffee; and 0.089 in Zegie coffee were detected confirming the applicability of the developed method for determination of caffeine in a complex matrix environment. The result indicated that users' highest preference for Wonbera and least preference for Zegie cultivated coffees are in agreement with the caffeine content.

  10. Electrocatalytic reduction of nitrite on tetraruthenated metalloporphyrins/Nafion glassy carbon modified electrode

    Energy Technology Data Exchange (ETDEWEB)

    Calfuman, Karla [Facultad de Ciencias, Departamento de Quimica, Universidad de Chile, Las Palmeras 3425, Casilla 653, Nunoa, Santiago (Chile); Aguirre, Maria Jesus [Facultad de Quimica y Biologia, Departamento de Quimica de los Materiales, Universidad de Santiago de Chile, Santiago (Chile); Canete-Rosales, Paulina; Bollo, Soledad [Facultad de Ciencias Quimicas y Farmaceuticas, Departamento de Quimica Farmacologica y Toxicologica, Universidad de Chile, Santiago (Chile); Llusar, Rosa [Departamento de Quimica Fisica y Analitica, Universidad de Jaume I, Castellon (Spain); Isaacs, Mauricio, E-mail: misaacs@uchile.cl [Facultad de Ciencias, Departamento de Quimica, Universidad de Chile, Las Palmeras 3425, Casilla 653, Nunoa, Santiago (Chile)

    2011-10-01

    Highlights: > Preparation and characterization of modified electrodes with M(II) Tetraruthenated porphyrins onto a Nafion film. > The electrodes were characterized by SEM, TEM, AFM and SECM techniques. > The modified electrodes are active in the electrochemical reduction of nitrite at -660 mV vs Ag/AgCl. > GC/Nf/CoTRP modified electrode is more electrochemically active than their Ni and Zn analogues. - Abstract: This paper describes the electrochemical reduction of nitrite ion in neutral aqueous solution mediated by tetraruthenated metalloporphyrins (Co(II), Ni(II) and Zn(II)) electrostatically assembled onto a Nafion film previously adsorbed on glassy carbon or ITO electrodes. Scanning electron microscope (SEM-EDX) and transmission electron microscopy (TEM) results have shown that on ITO electrodes the macrocycles forms multiple layers with a disordered stacking orientation over the Nafion film occupying hydrophobic and hydrophilic sites in the polyelectrolyte. Atomic force microscopy (AFM) results demonstrated that the Nafion film is 35 nm thick and tetraruthenated metalloporphyrins layers 190 nm thick presenting a thin but compacted morphology. Scanning electrochemical microscopy (SECM) images shows that the Co(II) tetraruthenated porphyrins/Nf/GC modified electrode is more electrochemically active than their Ni and Zn analogues. These modified electrodes are able to reduce nitrite at -660 mV showing enhanced reduction current and a decrease in the required overpotential compared to bare glassy carbon electrode. Controlled potential electrolysis experiments verify the production of ammonia, hydrazine and hydroxylamine at potentials where reduction of solvent is plausible demonstrating some selectivity toward the nitrite ion. Rotating disc electrode voltammetry shows that the factor that governs the kinetics of nitrite reduction is the charge propagation in the film.

  11. Electrochemical detection of nitrite based on the polythionine/carbon nanotube modified electrode

    International Nuclear Information System (INIS)

    Deng, Chunyan; Chen, Jinzhuo; Nie, Zhou; Yang, Minghui; Si, Shihui

    2012-01-01

    In this paper, thionine was electro-polymerized onto the surface of carbon nanotube (CNT)-modified glassy carbon (GC) to fabricate the polythionine (PTH)/CNT/GC electrode. It was found that the electro-reduction current of nitrite was enhanced greatly at the PTH/CNT/GC electrode. It may be demonstrated that PTH was used as a mediator for electrocatalytic reduction of nitrite, and CNTs as an excellent nanomaterial can improve the electron transfer between the electrode and nitrite. Therefore, based on the synergic effect of PTH and CNTs, the PTH/CNT/GC electrode was employed to detect nitrite, and the high sensitivity of 5.81 μA mM −1 , and the detection limit of 1.4 × 10 −6 M were obtained. Besides, the modified electrode showed an inherent stability, fast response time, and good anti-interference ability. These suggested that the PTH/CNT/GC electrode was favorable and reliable for the detection of nitrite. - Highlights: ► Polythionine (PTH) was used as a mediator for electrocatalytic reduction of nitrite. ► Carbon nanotubes (CNTs) improve electron transfer between the electrode and nitrite. ► The PTH/CNT/glassy carbon electrode showed excellent nitrite detection performance.

  12. Redox Response of Reduced Graphene Oxide-Modified Glassy Carbon Electrodes to Hydrogen Peroxide and Hydrazine

    Directory of Open Access Journals (Sweden)

    Jun-ichi Anzai

    2013-05-01

    Full Text Available The surface of a glassy carbon (GC electrode was modified with reduced graphene oxide (rGO to evaluate the electrochemical response of the modified GC electrodes to hydrogen peroxide (H2O2 and hydrazine. The electrode potential of the GC electrode was repeatedly scanned from −1.5 to 0.6 V in an aqueous dispersion of graphene oxide (GO to deposit rGO on the surface of the GC electrode. The surface morphology of the modified GC electrode was characterized by scanning electron microscopy (SEM and atomic force microscopy (AFM. SEM and AFM observations revealed that aggregated rGO was deposited on the GC electrode, forming a rather rough surface. The rGO-modified electrodes exhibited significantly higher responses in redox reactions of H2O2 as compared with the response of an unmodified GC electrode. In addition, the electrocatalytic activity of the rGO-modified electrode to hydrazine oxidation was also higher than that of the unmodified GC electrode. The response of the rGO-modified electrode was rationalized based on the higher catalytic activity of rGO to the redox reactions of H2O2 and hydrazine. The results suggest that rGO-modified electrodes are useful for constructing electrochemical sensors.

  13. Electrosorption of Os(III)-complex at single-wall carbon nanotubes immobilized on a glassy carbon electrode: Application to nanomolar detection of bromate, periodate and iodate

    International Nuclear Information System (INIS)

    Salimi, Abdollah; Kavosi, Begard; Babaei, Ali; Hallaj, Rahman

    2008-01-01

    A simple procedure was developed to prepare a glassy carbon electrode modified with single-wall carbon nanotubes (SWCNTs) and Os(III)-complex. The glassy carbon (GC) electrode modified with CNTs was immersed into Os(III)-complex solution (direct deposition) for a short period of time (60 s). 1,4,8,12-Tetraazacyclotetradecane osmium(III) chloride, (Os(III)LCl 2 ).ClO 4 , irreversibly and strongly adsorbed on SWCNTs immobilized on the surface of GC electrode. Cyclic voltammograms of the Os(III)-complex-incorporated-SWCNTs indicate a pair of well defined and nearly reversible redox couple with surface confined characteristic at wide pH range (1-8). The surface coverage (Γ) and charge transfer rate constant (k s ) of the immobilized Os-complex on SWCNTs were 3.07 x 10 -9 mol cm -2 , 5.5 (±0.2) s -1 , 2.94 x 10 -9 mol cm -2 , 7.3 (±0.3) s -1 at buffer solution with pH 2 and 7, respectively, indicate high loading ability of SWCNTs for Os(III) complex and great facilitation of the electron transfer between electroactive redox center and carbon nanotubes immobilized on the electrode surface. Modified electrodes showed higher electrocatalytic activity toward reduction of BrO 3 - , IO 3 - and IO 4 - in acidic solutions. The catalytic rate constants for catalytic reduction bromate, periodate and iodate were 3.79 (±0.2) x 10 3 , 7.32 (±0.2) x 10 3 and 1.75 (±0.2) x 10 3 M -1 s -1 , respectively. The hydrodynamic amperometry of rotating modified electrode at constant potential (0.3 V) was used for nanomolar detection of selected analytes. Excellent electrochemical reversibility of the redox couple, good reproducibility, high stability, low detection limit, long life time, fast amperometric response time, wide linear concentration range, technical simplicity and possibility of rapid preparation are great advantage of this sensor

  14. Poly(amidosulfonic acid) modified glassy carbon electrode for determination of isoniazid in pharmaceuticals.

    Science.gov (United States)

    Yang, Gongjun; Wang, Cunxiao; Zhang, Rui; Wang, Chenying; Qu, Qishu; Hu, Xiaoya

    2008-06-01

    Amidosulfonic acid was electropolymerized by cyclic voltammetry onto the surface of glassy carbon electrode (GCE) to fabricate the chemically modified electrode, which showed high stability, good selectivity and reproducibility for determination of isoniazid. The modified electrode showed an excellent electrocatalytical effect on the oxidation of isoniazid. Under the optimum conditions, there was a good linear relationship between anodic peak current and isoniazid concentration in the range of 5.0 x 10(-8)- 1.0 x 10(-5) M, and a detection limit of 1.0 x 10(-8) M (S/N = 3) was obtained after 120 s at the accumulation potential of - 0.2 V (vs. SCE). This developed method had been applied to the direct determination of isoniazid in injection and tablet samples with satisfactory results.

  15. Electrochemical Determination of Uric Acid at CdTe Quantum Dot Modified Glassy Carbon Electrodes.

    Science.gov (United States)

    Pan, Deng; Rong, Shengzhong; Zhang, Guangteng; Zhang, Yannan; Zhou, Qiang; Liu, Fenghai; Li, Miaojing; Chang, Dong; Pan, Hongzhi

    2015-01-01

    Cyclic voltammetry and differential pulse voltammetry were used to investigate the electrochemical behavior of uric acid (UA) at a CdTe quantum dot (QD) modified the glassy carbon electrode (GCE). CdTe QDs, as new semiconductor nanocrystals, can greatly improve the peak current of UA. The anodic peak current of UA was linear with its concentration between 1.0×10(-6) and 4.0×10(-4) M in 0.1 M pH 5.0 phosphate buffer solution. The LOD for UA at the CdTe electrode (1.0×10(-7) M) was superior to that of the GCE. In addition, we also determined the effects of scan rate, pH, and interferences of UA for the voltammetric behavior and detection. The results indicated that modified electrode possessed excellent reproducibility and stability. Finally, a new and efficient electrochemical sensor for detecting UA was developed.

  16. Sensitive determination of buformin using poly-aminobenzoic acid modified glassy carbon electrode

    Directory of Open Access Journals (Sweden)

    Gui-Ying Jin

    2012-12-01

    Full Text Available Glassy carbon electrode, which is used to electrochemically determine the content of buformin, is modified with an electropolymerized film of p-aminobenzoic acid in pH 7.0 acetate buffer solution (ABS. The polymer showed an excellent electrocatalytic activity for the reduction of buformin. In pH 7.0 ABS, the cathodic peak current increased linearly over three concentration intervals of buformin, and the detection limit (S/N=3 was 2.0×10−9 g/mL. The method was successfully applied to directly determine buformin in tablets with standard addition recoveries of 95.8–102.5%. The proposed method is simple, cheap and highly efficient. Keywords: Chemically modified electrode, Aminobenzoic acid, Buformin

  17. Determination of nitrite ion at schiff's base derivative of chitosan modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Xu Zhongliang; Zhang Jianmei; Liu Shujuan; Peng Daofeng

    2007-01-01

    Chitosan react with salicyclaldehyde by schiff's base reaction in water, a polymer product S-CTS can be prepared. Glassy carbon electrode was modified with S-CTS by drop-coating method. Then, its electrocatalysis effect on the reduction of nitrite by the films of S-CTS was investigated. Experimental results showed that S-CTS modified electrode could reduce the oxidation overpotential of nitrite in pH4.5 B-R buffer solution, the peak current of reduction was proportional to the concentration of nitrite and a good linear relation from 0.20 to 81 mg/kg (r=0.9899) with a detection limit of 2.8 x 10 -7 mol/L was obtained. The methods have been applied to determining nitrite in some samples, satisfactory results were obtained. (authors)

  18. Using Poly-L-Histidine Modified Glassy Carbon Electrode to Trace Hydroquinone in the Sewage Water

    Directory of Open Access Journals (Sweden)

    Bin Wang

    2014-01-01

    Full Text Available A sensitive voltammetric method for trace measurements of hydroquinone in the sewage water is described. The poly-L-histidine is prepared to modify the glassy carbon electrode in order to improve the electrochemical catalysis of interesting substances such as hydroquinone. The influence of the base solution, pH value, and scanning speed on the tracing of hydroquinone is discussed, and the experimental procedures and conditions are optimized. The laboratory results show that it is possible to construct a linear calibration curve between the peak current of hydroquinone on modified electrode and its concentration at the level of 0.00001 mol/L. The potential limitation of the method is suggested by a linear peaking shift model as well. The method was successfully applied to the determination of hydroquinone in the actual sample of industrial waste water.

  19. A highly efficient nano-cluster artificial peroxidase and its direct electrochemistry on a nano complex modified glassy carbon electrode.

    Science.gov (United States)

    Hong, Jun; Wang, Wei; Huang, Kun; Yang, Wei-Yun; Zhao, Ying-Xue; Xiao, Bao-Lin; Gao, Yun-Fei; Moosavi-Movahedi, Zainab; Ghourchian, Hedayatollah; Moosavi-Movahedi, Ali Akbar

    2012-01-01

    A nano-cluster with highly efficient peroxide activity was constructed based on nafion (NF) and cytochrome c (Cyt c). UV-Vis spectrometry and transmission electron microscopy (TEM) methods were utilized for characterization of the nano-structured enzyme or artificial peroxidase (AP). The nano-cluster was composed of a Chain-Ball structure, with an average ball size of about 40 nm. The Michaelis-Menten (K(m)) and catalytic rate (k(cat)) constants of the AP were determined to be 2.5 ± 0.4 µM and 0.069 ± 0.001 s(-1), respectively, in 50 mM PBS at pH 7.0. The catalytic efficiency of the AP was evaluated to be 0.028 ± 0.005 µM(-1) s(-1), which was 39 ± 5% as efficient as the native horseradish peroxidase (HRP). The AP was also immobilized on a functional multi-wall carbon nanotube (MWNCTs)-gold colloid nanoparticles (AuNPs) nano-complex modified glassy carbon (GC) electrode. The cyclic voltammetry of AP on the nano complex modified GC electrode showed a pair of well-defined redox peaks with a formal potential (E°') of -45 ± 2 mV (vs. Ag/AgCl) at a scan rate of 0.05 V/s. The heterogeneous electron transfer rate constant (k(s)) was evaluated to be 0.65 s(-1). The surface concentration of electroactive AP on GC electrode (Γ) was 7 × 10(-10) mol cm(-2). The apparent Michaelis-Menten constant (K(m)(app)) was 0.23 nM.

  20. The electrocatalytical reduction of m-nitrophenol on palladium nanoparticles modified glassy carbon electrodes

    International Nuclear Information System (INIS)

    Shi Qiaofang; Diao Guowang

    2011-01-01

    Highlights: ► The deposition of palladium on a GC electrode was performed by cyclic voltammetry. ► SEM images showed palladium nanoparticles deposited on a glassy carbon (GC) electrode. ► The Pd/GC electrode can effectively catalyze m-nitrophenol in aqueous media. ► The reduction of m-nitrophenol on the Pd/GC electrode depended on potential and pH. ► XPS spectra of the Pd/GC electrodes demonstrated the presence of palladium. - Abstract: Palladium nanoparticles modified glassy carbon electrodes (Pd/GC) were prepared via the electrodeposition of palladium on a glassy carbon (GC) electrode using cyclic voltammetry in different sweeping potential ranges. The scanning electron microscope images of palladium particles on the GC electrodes indicate that palladium particles with diameters of 20–50 nm were homogeneously dispersed on the GC electrode at the optimal deposition conditions, which can effectively catalyze the reduction of m-nitrophenol in aqueous solutions, but their catalytic activities are strongly related to the deposition conditions of Pd. The X-ray photoelectron spectroscopy spectra of the Pd/GC electrode confirmed that 37.1% Pd was contained in the surface composition of the Pd/GC electrode. The cyclic voltammograms of the Pd/GC electrode in the solution of m-nitrophenol show that the reduction peak of m-nitrophenol shifts towards the more positive potentials, accompanied with an increase in the peak current compared to the bare GC electrode. The electrocatalytic activity of the Pd/GC electrode is affected by pH values of the solution. In addition, the electrolysis of m-nitrophenol under a constant potential indicates that the reduction current of m-nitrophenol on the Pd/GC electrode is approximately 20 times larger than that on the bare GC electrode.

  1. Sensitive detection of hydroxylamine at a simple baicalin carbon nanotubes modified electrode.

    Science.gov (United States)

    Zhang, Hongfang; Zheng, Jianbin

    2012-05-15

    A baicalin multi-wall carbon nanotubes (BaMWCNT) modified glassy carbon electrode (GCE) for the sensitive determination of hydroxylamine was described. The BaMWCNT/GCE with dramatic stability was firstly fabricated with a simple adsorption method. And it showed excellent catalytic activity toward the electrooxidation of hydroxylamine. The amperometric response at the BaMWCNT/GCE modified electrode increased linearly to hydroxylamine concentrations in the range of 0.5 μM to 0.4mM with a detection limit of 0.1 μM. The modified electrode was applied to detection hydroxylamine in the tap water, and the average recovery for the standards added was 96.0%. Copyright © 2012 Elsevier B.V. All rights reserved.

  2. Electrochemical selective detection of dopamine on microbial carbohydrate-doped multiwall carbon nanotube-modified electrodes.

    Science.gov (United States)

    Jin, Joon-Hyung; Cho, Eunae; Jung, Seunho

    2010-03-01

    Microbial carbohydrate-doped multiwall carbon nanotube (MWNT)-modified electrodes were prepared for the purpose of determining if 4-(2-aminoethyl)benzene-1,2-diol (3,4-dihydroxyphenylalanine; dopamine) exists in the presence of 0.5 mM ascorbic acid, a representative interfering agent in neurotransmitter detection. The microbial carbohydrate dopants were alpha-cyclosophorohexadecaose (alpha-C16) from Xanthomonas oryzae and cyclic-(1 --> 2)-beta-d-glucan (Cys) from Rhizobium meliloti. The cyclic voltammetric responses showed that the highest sensitivity (5.8 x 10(-3) mA cm(-2) microM(-1)) is attained with the Cys-doped MWNT-modified ultra-trace carbon electrode, and that the alpha-C16-doped MWNT-modified glassy carbon electrode displays the best selectivity to dopamine (the approximate peak potential separation is 310 mV).

  3. Electrochemical behaviour of dopamine at covalent modified glassy carbon electrode with l-cysteine: preliminary results

    Directory of Open Access Journals (Sweden)

    Carlos Alberto Martínez-Huitle

    2009-01-01

    Full Text Available The surface of glassy carbon (GC electrode has been modified by oxidation of L-cysteine. The covalent modified GC electrode with L-Cysteine has been studied, according the supporting electrolyte used. Favourable interactions between the L-cysteine film and DA enhance the current response compared to that at the Nafion GC and bare GC electrodes, achieving better performances than those other electrodes. This behaviour was as result of the adsorption of the cysteine layer film, compact and uniform formation; depending on L-cysteine solution (phosphate buffer or chloridric acid supporting electrolyte used for modifying GC surface. In cyclic voltammetric measurements, modified electrodes can successfully separate the oxidation/reduction DA peaks in different buffer solutions, but an evident dependence in the response was obtained as function of pH and modified electrode. The modified electrode prepared with L-cysteine/HCl solution was used to obtain the calibration curve and it exhibited a stable and sensitive response to DA. The results are described and discussed in the light of the existing literature.

  4. Preparation and characterization of diethylene glycol bis(2-aminophenyl) ether-modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Isbir, Aybueke A.; Solak, Ali Osman; Ustuendag, Zafer; Bilge, Selen; Kilic, Zeynel

    2006-01-01

    Diethylene glycol bis(2-aminophenyl) ether (DGAE) diazonium salt was covalently electrografted on a glassy carbon (GC) surface and behavior of this novel surface was investigated. Synthesis of DGAE diazonium salt (DGAE-DAS) and in situ modification of GC electrode were performed in aqueous media containing NaNO 2 , keeping the temperature below +4 deg. C. For the characterization of the modified electrode surface by cyclic voltammetry, dopamine (DA) was used to prove the attachment of the DGAE-DAS on the GC surface. Raman spectroscopy and electrochemical impedance spectroscopy (EIS) were used to observe the molecular bound properties of the adsorbates at the DGAE-modified GC surface (GC-DGAE). The EIS results were analyzed using the Randles equivalent circuit. The charge transfer resistance on bare GC and the modified surface were calculated using the model equivalent circuit for the ferrocene redox system. Surface coverage was found as 0.4 showing the presence of high pinhole and defects in the modified electrode. The rate constant of electron transfer through the monolayer was calculated for ferrocene. Working potential range and the stability of the DGAE-modified GC electrode was also determined

  5. Preparation and characterization of diethylene glycol bis(2-aminophenyl) ether-modified glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Isbir, Aybueke A. [Ankara University, Faculty of Science, Department of Chemistry, 06100 Tandogan, Ankara (Turkey); Solak, Ali Osman [Ankara University, Faculty of Science, Department of Chemistry, 06100 Tandogan, Ankara (Turkey)]. E-mail: osolak@science.ankara.edu.tr; Ustuendag, Zafer [Ankara University, Faculty of Science, Department of Chemistry, 06100 Tandogan, Ankara (Turkey); Bilge, Selen [Ankara University, Faculty of Science, Department of Chemistry, 06100 Tandogan, Ankara (Turkey); Kilic, Zeynel [Ankara University, Faculty of Science, Department of Chemistry, 06100 Tandogan, Ankara (Turkey)

    2006-07-28

    Diethylene glycol bis(2-aminophenyl) ether (DGAE) diazonium salt was covalently electrografted on a glassy carbon (GC) surface and behavior of this novel surface was investigated. Synthesis of DGAE diazonium salt (DGAE-DAS) and in situ modification of GC electrode were performed in aqueous media containing NaNO{sub 2}, keeping the temperature below +4 deg. C. For the characterization of the modified electrode surface by cyclic voltammetry, dopamine (DA) was used to prove the attachment of the DGAE-DAS on the GC surface. Raman spectroscopy and electrochemical impedance spectroscopy (EIS) were used to observe the molecular bound properties of the adsorbates at the DGAE-modified GC surface (GC-DGAE). The EIS results were analyzed using the Randles equivalent circuit. The charge transfer resistance on bare GC and the modified surface were calculated using the model equivalent circuit for the ferrocene redox system. Surface coverage was found as 0.4 showing the presence of high pinhole and defects in the modified electrode. The rate constant of electron transfer through the monolayer was calculated for ferrocene. Working potential range and the stability of the DGAE-modified GC electrode was also determined.

  6. Electrochemical sensing of etoposide using carbon quantum dot modified glassy carbon electrode.

    Science.gov (United States)

    Nguyen, Hoai Viet; Richtera, Lukas; Moulick, Amitava; Xhaxhiu, Kledi; Kudr, Jiri; Cernei, Natalia; Polanska, Hana; Heger, Zbynek; Masarik, Michal; Kopel, Pavel; Stiborova, Marie; Eckschlager, Tomas; Adam, Vojtech; Kizek, Rene

    2016-04-25

    In this study, enhancement of the electrochemical signals of etoposide (ETO) measured by differential pulse voltammetry (DPV) by modifying a glassy carbon electrode (GCE) with carbon quantum dots (CQDs) is demonstrated. In comparison with a bare GCE, the modified GCE exhibited a higher sensitivity towards electrochemical detection of ETO. The lowest limit of detection was observed to be 5 nM ETO. Furthermore, scanning electron microscopy (SEM), fluorescence microscopy (FM), and electrochemical impedance spectroscopy (EIS) were employed for the further study of the working electrode surface after the modification with CQDs. Finally, the GCE modified with CQDs under optimized conditions was used to analyse real samples of ETO in the prostate cancer cell line PC3. After different incubation times (1, 3, 6, 9, 12, 18 and 24 h), these samples were then prepared prior to electrochemical detection by the GCE modified with CQDs. High performance liquid chromatography with an electrochemical detection method was employed to verify the results from the GCE modified with CQDs.

  7. Adsorptive stripping voltammetric determination of nitroimidazole derivative on multiwalled carbon nanotube modified electrodes: influence of size and functionalization of nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Jara-Ulloa, Paola; Canete-Rosales, Paulina; Nunez-Vergara, Luis J; Squella, Juan A., E-mail: asquella@ciq.uchile.c [University of Chile, Santiago (Chile). Chemical and Pharmaceutical Sciences Faculty. Bioelectrochemistry Lab.

    2011-07-01

    1-Methyl-4-nitro-2-bromine methylimidazole (4-NimMeBr), was electrochemically reduced on mercury, glassy carbon and multiwalled carbon nanotubes (MWCNT) modified electrodes. 4-NimMeBr was adsorbed on the MWCNT modified electrode thus permitting the implementation of an adsorptive stripping voltammetric (ASV) method. We have used 4-NimMeBr as a prototype electroactive nitro compound to study the effect of both the size of the nanotubes and its functionalization by oxidation. The oxidized MWCNT forms better dispersions than the non-oxidized, producing electrode surface with higher density of MWCNT as was determined by electrochemical mapping using scanning electrochemical microscopy (SECM). Under the optimized conditions, the peak current was proportional to the concentration of 4-NimMeBr in the range of 10{sup -6} mol L{sup -1} to 10{sup -4} mol L{sup -1} with detection and quantification limits of 4.41 x 10{sup -6} mol L{sup -1} and 6.21 x 10{sup -6} mol L{sup -1}, respectively. The sensibility of bare electrode was 0.01 {mu}A per mmol L{sup -1}, which was lower than the value of 5.34 and 6.97 mA per mmol L{sup -1} obtained using short and large oxidized MWCNT, respectively. (author)

  8. The electrochemical behavior of some podands at a benzo[c]cinnoline modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Isbir, Aybueke A.; Solak, Ali Osman; Uestuendag, Zafer; Bilge, Selen; Natsagdorj, Amgalan; Kilic, Emine; Kilic, Zeynel

    2005-01-01

    This paper describes the grafting of benzo[c]cinnoline (BCC) molecules on glassy carbon (GC) electrode surface. The attachment of BCC molecules to carbon substrate is induced by the electrochemical reduction of the corresponding diazonium salt. The modification of GC with BCC diazonium salt was done in aprotic solution and proved by blocking of dopamine electron transfer. The presence of BCC at the GC surface was characterized by cyclic voltammetry and X-ray photoelectron spectroscopy (XPS). On modified surface, the electrochemical behavior of two different types of podands and the catalytic effects of the GC-BCC surface were studied. The XPS was used to monitor element characteristics of the adsorbates on the GC surface and confirm the attachment of BCC molecules to the GC surface

  9. Voltammetric sensor for caffeine based on a glassy carbon electrode modified with Nafion and graphene oxide

    International Nuclear Information System (INIS)

    Zhao, F.; Wang, F.; Zhao, W.; Zhou, J.; Liu, Y.; Zou, L.; Ye, B.

    2011-01-01

    We report on a voltammetric sensor for caffeine that is based on a glassy carbon electrode modified with Nafion and graphene oxide (GO). It exhibits a good affinity for caffeine (resulting from the presence of Nafion), and excellent electrochemical response (resulting from the pressence of GO) for the oxidation of caffeine. The electrode enables the determination of caffeine in the range from 4.0 x 10 -7 to 8.0 x 10 -5 mol L -1 , with a detection limit of 2.0 x 10 -7 mol L -1 . The sensor displays good stability, reproducibility, and high sensitivity. It was successfully applied to the quantitative determination of caffeine in beverages. (author)

  10. Electrocatalytic behaviour and application of manganese porphyrin/gold nanoparticle- surface modified glassy carbon electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Sebarchievici, I., E-mail: incemc@incemc.ro [National Institute of Research for Electrochemistry and Condensed Matter, Aurel Paunescu Podeanu Street 144, 300569 Timisoara (Romania); Tăranu, B.O. [National Institute of Research for Electrochemistry and Condensed Matter, Aurel Paunescu Podeanu Street 144, 300569 Timisoara (Romania); Birdeanu, M. [National Institute of Research for Electrochemistry and Condensed Matter, Aurel Paunescu Podeanu Street 144, 300569 Timisoara (Romania); Institute of Chemistry Timisoara of Romanian Academy, M. Viteazul Ave. 24, 300223 Timisoara (Romania); Rus, S.F. [National Institute of Research for Electrochemistry and Condensed Matter, Aurel Paunescu Podeanu Street 144, 300569 Timisoara (Romania); Fagadar-Cosma, E., E-mail: efagadar@yahoo.com [Institute of Chemistry Timisoara of Romanian Academy, M. Viteazul Ave. 24, 300223 Timisoara (Romania)

    2016-12-30

    Highlights: • Mn-porphyrin/gold nanoparticle-modified glassy carbon electrodes were obtained. • AFM investigations of thin films display multilayer of triangular type architecture. • Oxidation and reduction processes of H{sub 2}O{sub 2} are diffusion controled. • There is a linear dependence between H{sub 2}O{sub 2} concentration and the currents intensity. • The modified electrodes show better electrochemical detection ability to H{sub 2}O{sub 2}. - Abstract: The main purpose of this research was to obtain manganese porphyrin/gold nanoparticle-modified glassy carbon electrodes and to use them for the detection of H{sub 2}O{sub 2}. Two sets of modified electrodes were prepared by drop-cast deposition of 5,10,15,20-tetra(4-methyl-phenyl)porphyrinato manganese(III) chloride alone and of the same Mn-porphyrin and gold-colloid solution and comparatively characterized by Raman, UV–vis, ellipsometry, AFM and TEM microscopy, XPS and cyclic voltammetry. XPS spectrum recorded for GC-MnP-nAu modified electrode displayed the characteristic signals of gold nanoparticles. The optical parameters have greater values for GC-MnP-nAu in comparison with GC-MnP, due to increasing charge transfer efficiency. The MnP-nAu film mediates the electron transfer between H{sub 2}O{sub 2} and GC, evidenced by an increase in the current intensity of the anodic peak, and facilitates the electrochemical regeneration of oxidized H{sub 2}O{sub 2} at cathodic potentials. From the cyclic voltammetry experiments a linear relationship between H{sub 2}O{sub 2} concentration vs oxidation and reduction currents was observed. The linear dependence between density of current and the square root of the scan rate indicates that the oxidation and reduction processes of H{sub 2}O{sub 2} are diffusion controlled. The GC-MnP-nAu modified electrode shows great potential as electrochemical sensor for determination of hydrogen peroxide.

  11. High Electrocatalytic Performance of CuCoNi@CNTs Modified Glassy Carbon Electrode towards Methanol Oxidation in Alkaline Medium

    Directory of Open Access Journals (Sweden)

    Amina A. Hamza

    2017-01-01

    Full Text Available A novel non-precious multiwalled carbon nanotubes (CNTs—supported metal oxide electrocatalyst was developed for methanol electrooxidation in alkaline medium. The catalyst was fabricated by simultaneous electrodeposition of copper-cobalt-nickel ternary nanostructures (CuCoNi on a glassy carbon electrode (GCE modified with CNTs. The proposed electrode was characterized using X-ray diffraction (XRD, energy dispersive X-ray (EDX, and scanning electron microscopy (SEM. The electrochemical behavior and the electrocatalytic performance of the suggested electrode towards the oxidation of methanol were evaluated by cyclic voltammetry (CV, linear sweep voltammetry (LSV, and chronoamperometry (CA in alkaline medium. Several parameters were investigated, e.g., deposition time, potential scan rate, etc. Compared to Cu, Co, or Ni mono electrocatalysts, the electrode based on ternary-metals exhibited superior electrocatalytic activity and stability towards methanol electrooxidation. For instance, CuCoNi@CNTs/GCE has shown at least 2.5 times electrocatalytic activity and stability compared to the mono eletrocatalysts. Moreover, the present study found that the optimized loading level is 1500 s of simultaneous electrodeposition. At this loading level, it was found that the relation between the Ip/ν1/2 function and scan rate gives the characteristic features of a catalytic process. The enhanced activity and stability of CuCoNi@CNTs/GCE was attributed to (i a synergism between three metal oxides coexisting in the same structure; (ii the presence of CNTs as a support for the metal oxides, that offers high surface area for the deposited tertiary alloy and suppresses the aggregation and sintering of the metals oxide with time; as well as (iii the increase of the conductivity of the deposited semiconducting metal oxides.

  12. Selective oxidation of serotonin and norepinephrine over eriochrome cyanine R film modified glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Yao Hong; Li Shaoguang [Department of Pharmaceutical Analysis, Faculty of Pharmacy, Fujian Medical University, Fuzhou 350004 (China); Tang Yuhai [Institute of Analytical Sciences, Xi' an Jiaotong University, Xi' an 710061 (China); Chen Yan [Department of Pharmaceutical Analysis, Faculty of Pharmacy, Fujian Medical University, Fuzhou 350004 (China); Chen Yuanzhong [Fujian Institute of Hematology, The Affiliated Union Hospital of Fujian Medical University, Fuzhou 350001 (China)], E-Mail: chenyz@pub3.fz.fj.cn; Lin Xinhua [Department of Pharmaceutical Analysis, Faculty of Pharmacy, Fujian Medical University, Fuzhou 350004 (China)], E-mail: xhlin1963@sin.com

    2009-08-01

    A novel ECR-modified electrode is fabricated by electrodeposition of Eriochrome Cyanine R (ECR) at a glassy carbon (GC) electrode by cyclic voltammetry (CV) in double-distilled water. The characterization of the ECR film modified electrode is carried out by atomic force microscopy (AFM), infrared spectra (IR), spectroelectrochemistry and cyclic voltammetry. The results show that a slightly heterogeneous film formed on the surface of the modified electrode, and the calculated surface concentration of ECR is 2 x 10{sup -10} mol/cm{sup -2}. The ECR film modified GC electrode shows excellent electrocatalytic activities toward the oxidation of serotonin (5-HT) and norepinephrine (NE). Furthermore, the modified electrode can separately detect 5-HT and NE, even in the presence of 200-fold concentration of ascorbic acid (AA) and 25-fold concentration of uric acid (UA). Using differential pulse voltammetry (DPV), the peak currents of 5-HT and NE recorded in pH 7 solution are linearly dependent on their concentrations in the range of 0.05-5 {mu}M and 2-50 {mu}M, respectively. The limits of detection are 0.05 and 1.5 {mu}M for 5-HT and NE, respectively. The ECR film modified electrode can be stored stable for at least 1 week in 0.05 M PBS (pH 7) at 4 {sup o}C in a refrigerator. Owing to its excellent selectivity and sensitivity, the modified electrode could provide a promising tool for the simultaneous determination of 5-HT and NE in complex biosamples.

  13. Electrocatalytic Oxidation of Hydroxylamine at a Quinizarine Modified Glassy Carbon Electrode: Application to Differential Pulse Voltammetry Detection of Hydroxylamine

    OpenAIRE

    MAZLOUMARDAKANI, Mohammad; KARAMI, Payam EBRAHIMI

    2014-01-01

    The electrocatalytic behavior of hydroxylamine was studied on a glassy carbon electrode modified by electrodeposition of quinizarine, using cyclic voltammetry, chronoamperometry, and rotating disk voltammetry as diagnostic techniques. Cyclic voltammetry showed that the catalytic current of the system depends on the concentration of hydroxylamine. The magnitude of the peak current for quinizarine increased sharply in the presence of hydroxylamine and proportional to hydroxylamine conc...

  14. Direct electrochemistry of glucose oxidase and glucose biosensing on a hydroxyl fullerenes modified glassy carbon electrode.

    Science.gov (United States)

    Gao, Yun-Fei; Yang, Tian; Yang, Xiao-Lu; Zhang, Yu-Shuai; Xiao, Bao-Lin; Hong, Jun; Sheibani, Nader; Ghourchian, Hedayatollah; Hong, Tao; Moosavi-Movahedi, Ali Akbar

    2014-10-15

    Direct electrochemistry of glucose oxidase (GOD) was achieved when GOD-hydroxyl fullerenes (HFs) nano-complex was immobilized on a glassy carbon (GC) electrode and protected with a chitosan (Chit) membrane. The ultraviolet-visible absorption spectrometry (UV-vis), transmission electron microscopy (TEM), and circular dichroism spectropolarimeter (CD) methods were utilized for additional characterization of the GOD, GOD-HFs and Chit/GOD-HFs. Chit/HFs may preserve the secondary structure and catalytic properties of GOD. The cyclic voltammograms (CVs) of the modified GC electrode showed a pair of well-defined quasi-reversible redox peaks with the formal potential (E°') of 353 ± 2 mV versus Ag/AgCl at a scan rate of 0.05 V/s. The heterogeneous electron transfer constant (ks) was calculated to be 2.7 ± 0.2s(-1). The modified electrode response to glucose was linear in the concentrations ranging from 0.05 to 1.0mM, with a detection limit of 5 ± 1 μM. The apparent Michaelis-Menten constant (Km(app)) was 694 ± 8 μM. Thus, the modified electrode could be applied as a third generation biosensor for glucose with high sensitivity, selectivity and low detection limit. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. Determination of Mercury (II Ion on Aryl Amide-Type Podand-Modified Glassy Carbon Electrode

    Directory of Open Access Journals (Sweden)

    Sevgi Güney

    2011-01-01

    Full Text Available A new voltammetric sensor based on an aryl amide type podand, 1,8-bis(o-amidophenoxy-3,6-dioxaoctane, (AAP modified glassy carbon electrode, was described for the determination of trace level of mercury (II ion by cyclic voltammetry (CV and differential pulse voltammetry (DPV. A well-defined anodic peak corresponding to the oxidation of mercury on proposed electrode was obtained at 0.2 V versus Ag/AgCl reference electrode. The effect of experimental parameters on differential voltammetric peak currents was investigated in acetate buffer solution of pH 7.0 containing 1 × 10−1 mol L−1 NaCl. Mercury (II ion was preconcentrated at the modified electrode by forming complex with AAP under proper conditions and then reduced on the surface of the electrode. Interferences of Cu2+, Pb2+, Fe3+, Cd2+, and Zn2+ ions were also studied at two different concentration ratios with respect to mercury (II ions. The modified electrode was applied to the determination of mercury (II ions in seawater sample.

  16. ELECTROCHEMICAL DETERMINATION OF ETHANOL, 2- PROPANOL AND 1-BUTANOL ON GLASSY CARBON ELECTRODE MODIFIED WITH NICKEL OXIDE FILM

    Directory of Open Access Journals (Sweden)

    A. Benchettara

    2014-12-01

    Full Text Available In this work, we present the modification of a glassy carbon electrode with nickel oxide film which is performed in two successive steps. In the first one, the electrochemical deposition of metallic nickel on the glassy carbon electrode (GCE is achieved in 0.1M boric acid; in the second step, the metallic deposit is anodically oxidized in 0.1M NaOH. These two operations were carried out in a three electrode cell with a filiform platinum auxiliary electrode, a SCE as potential reference and a working microelectrode of modified glassy carbon with nickel oxides. This electrode is characterized by several electrochemical techniques and is used for the catalytic determination of ethanol, 2-propanol and 1-butanol in 0.1 M NaOH. The proposed chemical mechanism shows that NiO2 acts as a mediator.

  17. ELECTROCHEMICAL DETERMINATION OF ETHANOL, 2- PROPANOL AND 1-BUTANOL ON GLASSY CARBON ELECTRODE MODIFIED WITH NICKEL OXIDE FILM

    Directory of Open Access Journals (Sweden)

    A. Benchettara

    2015-07-01

    Full Text Available In this work, we present the modification of a glassy carbon electrode with nickel oxide film which is performed in two successive steps. In the first one, the electrochemical deposition of metallic nickel on the glassy carbon electrode (GCE is achieved in 0.1M boric acid; in the second step, the metallic deposit is anodically oxidized in 0.1M NaOH. These two operations were carried out in a three electrode cell with a filiform platinum auxiliary electrode, a SCE as potential reference and a working microelectrode of modified glassy carbon with nickel oxides. This electrode is characterized by several electrochemical techniques and is used for the catalytic determination of ethanol, 2-propanol and 1-butanol in 0.1 M NaOH. The proposed chemical mechanism shows that NiO2 acts as a mediator.

  18. Molecular imprinted polypyrrole modified glassy carbon electrode for the determination of tobramycin

    International Nuclear Information System (INIS)

    Gupta, Vinod Kumar; Yola, Mehmet Lütfi; Özaltın, Nuran; Atar, Necip; Üstündağ, Zafer; Uzun, Lokman

    2013-01-01

    Graphical abstract: Atomic force microscopic images of (A) bare GCE and (B) TOB imprinted PPy/GCE surface. - Highlights: • Glassy carbon electrode based on molecularly imprinted polypyrrole was prepared. • The developed surfaces were characterized by AFM, FTIR, EIS and CV. • The developed nanosensor was applied to egg and milk samples. - Abstract: Over the past two decades, molecular imprinted polymers have attracted a broad interest from scientists in sensor development. In the preparation of molecular imprinted polymers the desired molecule (template) induces the creation of specific recognition sites in the polymer. In this study, the glassy carbon electrode (GCE) based on molecularly imprinted polypyrrole (PPy) was fabricated for the determination of tobramycin (TOB). The developed electrode was prepared by incorporation of a template molecule (TOB) during the electropolymerization of pyrrole on GCE in aqueous solution using cyclic voltammetry (CV) method. The performance of the imprinted and non-imprinted electrodes was evaluated by square wave voltammetry (SWV). The effect of pH, monomer and template concentrations, electropolymerization cycles on the performance of the imprinted and non-imprinted electrodes was investigated and optimized. The non-modified and TOB-imprinted surfaces were characterized by using atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), electrochemical impedance spectroscopy (EIS) and CV. The linearity range of TOB was 5.0 × 10 −10 –1.0 × 10 −8 M with the detection limit of 1.4 × 10 −10 M. The developed nanosensor was applied successfully for the determination of TOB in egg and milk

  19. A new sensor based on glassy carbon electrode modified with nanocomposite for simultaneous determination of acetaminophen, ascorbic acid and uric acid

    Directory of Open Access Journals (Sweden)

    Mohammad Afrasiabi

    2016-09-01

    Full Text Available A chemically-modified electrode has been constructed based on a single walled carbon nanotube/chitosan/room temperature ionic liquid nanocomposite modified glassy carbon electrode (SWCNTs–CHIT–RTIL/GCE. It was demonstrated that this sensor could be used for simultaneous determination of acetaminophen (ACT, uric acid (URI and ascorbic acid (ASC. The measurements were carried out by application of differential pulse voltammetry (DPV, cyclic voltammetry (CV and chronoamperometry (CA methods. Electrochemical studies suggested that the RTIL and SWCNTs provided a synergistic augmentation that can increase current responses by improvement of electron transfers of these compounds on the electrode surface. The presence of the CHIT in the modified electrode can enhance the repeatability of the sensor by its antifouling effect. The modified electrode showed electrochemical responses with high sensitivity for ACT, URI and ASC determination, which makes it a suitable sensor for simultaneous sub-μmol L−1 detection of ACT, URI and ASC in aqueous solutions. The analytical performance of this sensor has been evaluated for detection of ACT, URI and ASC in human serum and urine with satisfactory results.

  20. Study and Electrochemical Determination of Tyrosine at Graphene Nanosheets Composite Film Modified Glassy Carbon Electrode

    Directory of Open Access Journals (Sweden)

    M. Behpour

    2013-06-01

    Full Text Available A graphene nanosheets (GNS film coated glassy carbon electrode (GCE was fabricated for sensitive determination of tyrosine (Tyr. The GNS-based sensor was characterized by scanning electron microscope and electrochemical impedance spectroscopy. The voltammetric techniques were employed to study electro-oxidation of Tyr. The results revealed that the modified electrode showed an electrocatalytic activity toward the anodic oxidation of Tyr by a marked enhancement in the current intensity and the shift in the oxidation potential to lower values (50 mV in comparison with the bare GCE. Some kinetic parameters such as the electron transfer coefficient (α were also determined for the Tyr oxidation. The detection limit  for Tyr was found to be 2.0×10-8 M (n=9, and the peak current increases linearly with the Tyr concentration within the molar concentration ranges of 5.0 ×10-6 to 1.2 ×10-4 M. The modified electrode shows good sensitivity, selectivity and stability. The prepared electrode was applied for the determination of Tyr in real sample.

  1. Methionine – Au Nanoparticle Modified Glassy Carbon Electrode: a Novel Platform for Electrochemical Detection of Hydroquinone

    Directory of Open Access Journals (Sweden)

    Jiahong HE

    2014-12-01

    Full Text Available A high sensitive electrochemical sensor based on methionine/gold nanoparticles (MET/AuNPs modified glassy carbon electrode (GCE was fabricated for the quantitative detection of hydroquinone (HQ. The as-modified electrode was characterized by scanning electron microscopy (SEM and X-ray diffraction (XRD techniques. The electrochemical performance of the sensor to HQ was investigated by using cyclic and differential pulse voltammetry, which revealed its excellent electrocatalytic activity and reversibility towards HQ. The separation of anodic and cathodic peak (∆Ep was decreased from 471 mV to 75 mV. The anodic peak current achieved under the optimum conditions was linear with the HQ concentration ranging from 8 μM to 400 μM with the detection limit 0.12 μM (3σ. The as-fabricated sensor also showed a good selectivity towards HQ without demonstrating interference from other coexisting species. Furthermore, the sensor showed a good performance for HQ detection in environmental water, which suggests its potential practical application. DOI: http://dx.doi.org/10.5755/j01.ms.20.4.6477

  2. Sensitive Electrochemical Detection of Dopamine With a Nitrogen-doped Graphene Modified Glassy Carbon Electrode

    Directory of Open Access Journals (Sweden)

    Wencheng Wang

    2016-09-01

    Full Text Available In this paper nitrogen-doped graphene (NG nanosheets were used as the modifier on the surface of glassy carbon electrode (GCE. The modified electrode (NG/GCE was further applied to the sensitive detection of dopamine (DA by voltammetric method. Due to the unique properties of NG such as large surface area and excellent electrocatalytic activity, electrochemical response of DA was greatly enhanced on NG/GCE with a pair of well-defined redox peaks appeared on cyclic voltammogram. Electrochemical behaviors of DA on NG/GCE were carefully investigated with the electrochemical parameters calculated. Under the selected conditions the oxidation peak currents of DA had a good linear relationship with its concentration in the range from 8.0×10–7 mol L–1 to 8.0×10–4 mol L–1 with a detection limit of 2.55×10–7 mol L–1 (3σ. The proposed method was further applied to the DA injection samples determination with satisfactory results. This work is licensed under a Creative Commons Attribution 4.0 International License.

  3. Biomedical Applications of Modified Carbon Glassy Electrode Sensor with Nanoparticles and Dendrimers

    Directory of Open Access Journals (Sweden)

    Solomon W. LEUNG

    2011-04-01

    Full Text Available We previously reported the development of a biosensor platform that is capable of measuring biometabolites and environmental sensitive species, such as peroxide and nitrate/nitrate, to concentrations in the order of ppb (parts per billion or lower. In this investigation, we modified our platform with dendrimers to enhance its performance. Zero and second generation of dendrimers were coated on the surface of a carbon glassy electrode which was then modified with l-glutamate dehydrogenase (GDH and α-keto glutarate. The resulting electrode was tested with ammonium solutions, concentrations ranged from 2 to 300 nM at pH 7.4; the results were satisfactory. Measurements at lower concentrations had better resolution than at higher concentrations and it is believed that the measurement limit can be lower than 2 nM. This biosensor platform was proven to be versatile and can be employed as a platform for ultrasensitive detecting devices in many biomedical and environmental applications.

  4. Simultaneous voltammetric determination of tramadol and acetaminophen using carbon nanoparticles modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Ghorbani-Bidkorbeh, Fatemeh; Shahrokhian, Saeed; Mohammadi, Ali; Dinarvand, Rassoul

    2010-01-01

    A sensitive and selective electrochemical sensor was fabricated via the drop-casting of carbon nanoparticles (CNPs) suspension onto a glassy carbon electrode (GCE). The application of this sensor was investigated in simultaneous determination of acetaminophen (ACE) and tramadol (TRA) drugs in pharmaceutical dosage form and ACE determination in human plasma. In order to study the electrochemical behaviors of the drugs, cyclic and differential pulse voltammetric studies of ACE and TRA were carried out at the surfaces of the modified GCE (MGCE) and the bare GCE. The dependence of peak currents and potentials on pH, concentration and the potential scan rate were investigated for these compounds at the surface of MGCE. Atomic force microscopy (AFM) was used for the characterization of the film modifier and its morphology on the surface of GCE. The results of the electrochemical investigations showed that CNPs, via a thin layer model based on the diffusion within a porous layer, enhanced the electroactive surface area and caused a remarkable increase in the peak currents. The thin layer of the modifier showed a catalytic effect and accelerated the rate of the electron transfer process. Application of the MGCE resulted in a sensitivity enhancement and a considerable decrease in the anodic overpotential, leading to negative shifts in peak potentials. An optimum electrochemical response was obtained for the sensor in the buffered solution of pH 7.0 and using 2 μL CNPs suspension cast on the surface of GCE. Using differential pulse voltammetry, the prepared sensor showed good sensitivity and selectivity for the determination of ACE and TRA in wide linear ranges of 0.1-100 and 10-1000 μM, respectively. The resulted detection limits for ACE and TRA was 0.05 and 1 μM, respectively. The CNPs modified GCE was successfully applied for ACE and TRA determinations in pharmaceutical dosage forms and also for the determination of ACE in human plasma.

  5. Electrochemical Glucose Oxidation Using Glassy Carbon Electrodes Modified with Au-Ag Nanoparticles: Influence of Ag Content

    Directory of Open Access Journals (Sweden)

    Nancy Gabriela García-Morales

    2015-01-01

    Full Text Available This paper describes the application of glassy carbon modified electrodes bearing Aux-Agy nanoparticles to catalyze the electrochemical oxidation of glucose. In particular, the paper shows the influence of the Ag content on this oxidation process. A simple method was applied to prepare the nanoparticles, which were characterized by transmission electron microscopy, Ultraviolet-Visible spectroscopy, X-ray diffraction spectroscopy, and cyclic voltammetry. These nanoparticles were used to modify glassy carbon electrodes. The effectiveness of these electrodes for electrochemical glucose oxidation was evaluated. The modified glassy carbon electrodes are highly sensitive to glucose oxidation in alkaline media, which could be attributed to the presence of Aux-Agy nanoparticles on the electrode surface. The voltammetric results suggest that the glucose oxidation speed is controlled by the glucose diffusion to the electrode surface. These results also show that the catalytic activity of the electrodes depends on the Ag content of the nanoparticles. Best results were obtained for the Au80-Ag20 nanoparticles modified electrode. This electrode could be used for Gluconic acid (GA production.

  6. Towards the conception of an amperometric sensor of L-tyrosine based on Hemin/PAMAM/MWCNT modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Ma Qiang; Ai Shiyun; Yin Huanshun; Chen Quanpeng; Tang Tiantian

    2010-01-01

    A novel amperometric sensor was fabricated based on the immobilization of hemin onto the poly (amidoamine)/multi-walled carbon nanotube (PAMAM/MWCNT) nanocomposite film modified glassy carbon electrode (GCE). Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and ultraviolet visible (UV-vis) adsorption spectroscopy were used to investigate the possible state and electrochemical activity of the immobilized hemin. In the Hemin/PAMAM/MWCNT nanocomposite film, MWCNT layer possessed excellent inherent conductivity to enhance the electron transfer rate, while the layer of PAMAM greatly enlarged the surface average concentration of hemin (Γ) on the modified electrode. Therefore, the nanocomposite film showed enhanced electrocatalytical activity towards the oxidation of L-tyrosine. The kinetic parameters of the modified electrode were investigated. In pH 7.0 phosphate buffer solution (PBS), the sensor exhibits a wide linear range from 0.1 μM to 28.8 μM L-tyrosine with a detection limit of 0.01 μM and a high sensitivity of 0.31 μA μM -1 cm -2 . In addition, the response time of the L-tyrosine sensor is less than 5 s. The excellent performance of the sensor is largely attributed to the electro-generated high reactive oxoiron (IV) porphyrin (O = Fe IV -P) which effectively catalyzed the oxidation of L-tyrosine. A mechanism was herein proposed for the catalytic oxidation of L-tyrosine by oxoiron (IV) porphyrin complexes.

  7. Modification of glassy carbon electrode with poly(hydroxynaphthol blue)/multi-walled carbon nanotubes composite and construction a new voltammetric sensor for the simultaneous determination of hydroquinone, catechol, and resorcinol

    Science.gov (United States)

    Daneshinejad, Hassan; Arab Chamjangali, Mansour; Goudarzi, Nasser; Hossain Amin, Amir

    2018-03-01

    A novel voltammetric sensor is developed based on a poly(hydroxynaphthol blue)/multi-walled carbon nanotubes-modified glassy carbon electrode for the simultaneous determination of the dihydroxybenzene isomers hydroquinone (HQ), catechol (CC), and resorcinol (RS). The preparation and basic electrochemical performance of the sensor are investigated in details. The electrochemical behavior of the dihydroxybenzene isomers at the sensor is studied by the cyclic and differential pulse voltammetric techniques. The results obtained show that this new electrochemical sensor exhibits an excellent electro-catalytic activity towards oxidation of the three isomers. The mechanism of this electro-catalytic activity is discussed. Using the optimum parameters, limit of detection obtained 0.24, 0.24, and 0.26 μmol L-1 for HQ, CC, and RS, respectively. The modified electrode is also successfully applied to the simultaneous determination of dihydroxybenzene in water samples.

  8. Ultrasensitive Determination of Piroxicam at Diflunisal-Derived Gold Nanoparticle-Modified Glassy Carbon Electrode

    Science.gov (United States)

    Shaikh, Tayyaba; uddin, SiraJ; Talpur, Farah N.; Khaskeli, Abdul R.; Agheem, Muhammad H.; Shah, Muhammad R.; Sherazi, Tufail H.; Siddiqui, Samia

    2017-10-01

    We present a simple and green approach for synthesis of gold nanoparticles (AuNps) using analgesic drug diflunisal (DF) as capping and stabilizing agent in aqueous solution. Characterization of the synthesized diflunisal-derived gold nanoparticles (DF-AuNps) was performed by ultraviolet-visible (UV-Vis) spectroscopy, revealing the surface plasmon absorption band at 520 nm under optimized experimental conditions. Fourier-transform infrared (FTIR) spectroscopy established the effective interaction of the capping agent with the AuNps. Topographical features of the synthesized DF-AuNps were assessed by atomic force microscopy (AFM), revealing average particle height of 29 nm to 32 nm. X-ray diffractometry was used to study the crystalline nature, revealing that the synthesized DF-AuNps possessed excellent crystalline properties. The synthesized DF-AuNps were employed to modify the surface of glassy carbon electrode (GCE) for selective determination of piroxicam (PX) using differential pulse voltammetry technique. The fabricated Nafion/DF-AuNps/GCE sensor exhibited high sensitivity compared with bare GCE. The current response of the fabricated sensor was found to be linear in the PX concentration range of 0.5 μM to 50 μM, with limit of detection (LOD) and limit of quantification (LOQ) of 50 nM and 150 nM, respectively. The proposed sensor was successfully utilized for sensitive and rapid determination of PX in human serum, urine, and pharmaceutical samples.

  9. The Enhanced Photo-Electrochemical Detection of Uric Acid on Au Nanoparticles Modified Glassy Carbon Electrode

    Science.gov (United States)

    Shi, Yuting; Wang, Jin; Li, Shumin; Yan, Bo; Xu, Hui; Zhang, Ke; Du, Yukou

    2017-07-01

    In this work, a sensitive and novel method for determining uric acid (UA) has been developed, in which the glassy carbon electrode (GCE) was modified with electrodeposition Au nanoparticles and used to monitor the concentration of UA with the assistant of visible light illumination. The morphology of the Au nanoparticles deposited on GCE surface were characterized by scanning electron microscope (SEM) and the nanoparticles were found to be well-dispersed spheres with the average diameter approaching 26.1 nm. A series of cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements have revealed that the introduction of visible light can greatly enhance both the strength and stability of response current due to the surface plasmon resonance (SPR). Specifically, the DPV showed a linear relationship between peak current and UA concentration in the range of 2.8 to 57.5 μM with the equation of I pa (μA) = 0.0121 c UA (μM) + 0.3122 ( R 2 = 0.9987). Herein, the visible light illuminated Au/GCE possesses a potential to be a sensitive electrochemical sensor in the future.

  10. Glassy carbon electrode modified with polyanilne/ethylenediamine for detection of copper ions

    Science.gov (United States)

    Patil, Harshada K.; Deshmukh, Megha A.; Bodkhe, Gajanan A.; Shirsat, Mahendra D.

    2018-05-01

    Increasing water pollution is having high concern, since it creates the threats to all leaving organisms of existence. Industrial sewages have not only polluted the main stream lines of water, also the ground level water is having serious contaminations. Heavy metal ions are the pollutants which are not degradable and can be accumulated on living things ultimately the excess accumulation results into the serious concerns. Therefore, it is necessary to develop the sensors which can detect the heavy metal ions up to its maximum contamination limits. Conducting polymers are the materials which possess large application spectra. This investigation reports the electrochemically synthesized polyaniline (PANI) for modification of glassy carbon electrode (GCE). Ethylenediamine (EDA) - chelating ligand used for the modification of polyaniline so as to inculcate the selectivity toward copper ions Cu (II). The electrochemical cyclic voltammetry (CV) was used for the study of redox characteristics of PANI and influence of EDA modification. The result of CV has shown the reduced oxidation and reduction peak currents after modification indicating the domination of EDA. GCE modified with PANI/EDA was then employed for the detection of divalent copper ions and have shown the affinity toward Cu ions. The detection limit achieved was equal to 10mg/lit.

  11. Voltammetric Determination of Codeine on Glassy Carbon Electrode Modified with Nafion/MWCNTs

    Directory of Open Access Journals (Sweden)

    Robert Piech

    2015-01-01

    Full Text Available A glassy carbon electrode modified with a Nafion/MWCNTs composite is shown to enable the determination of codeine using differential pulse voltammetry in phosphate buffer of pH 3.0. At a preconcentration time of 15 s, the calibration graph is linear in the 0.5 µM (0.15 mg·L−1 to 15 µM (4.5 mg·L−1 concentration range with a correlation coefficient of 0.998. The detection limit at a preconcentration time of 120 s is as low as 4.5 μg·L−1. The repeatability of the method at a 0.6 μg·L−1 concentration level, expressed as the RSD, is 3.7% (for n=5. The method was successfully applied and validated by analyzing codeine in drug, human plasma, and urine samples.

  12. Modification of glassy carbon electrode with multi-walled carbon nanotubes and iron(III)-porphyrin film: Application to chlorate, bromate and iodate detection

    International Nuclear Information System (INIS)

    Salimi, Abdollah; MamKhezri, Hussein; Hallaj, Rahman; Zandi, Shiva

    2007-01-01

    In this study, multi-wall carbon nanotubes (MWCTs) is evaluated as a transducer, stabilizer and immobilization matrix for the construction of amperometric sensor based on iron-porphyrin. 5,10,15,20-Tetraphenyl-21H,23H-porphine iron(III) chloride (Fe(III)P) adsorbed on MWCNTs immobilized on the surface of glassy carbon electrode. Cyclic voltammograms of the Fe(III)P-incorporated-MWCNTs indicate a pair of well-defined and nearly reversible redox couple with surface confined characteristics at wide pH range (2-12). The surface coverage (Γ) and charge transfer rate constant (k s ) of Fe(III)P immobilized on MWCNTs were 7.68 x 10 -9 mol cm -2 and 1.8 s -1 , respectively, indicating high loading ability of MWCNTs for Fe(III)P and great facilitation of the electron transfer between Fe(III)P and carbon nanotubes immobilized on the electrode surface. Modified electrodes exhibit excellent electrocatalytic activity toward reduction of ClO 3 - , IO 3 - and BrO 3 - in acidic solutions. The catalytic rate constants for catalytic reduction of bromate, chlorate and iodate were 6.8 x 10 3 , 7.4 x 10 3 and 4.8 x 10 2 M -1 s -1 , respectively. The hydrodynamic amperometry of rotating-modified electrode at constant potential versus reference electrode was used for detection of bromate, chlorate and iodate. The detection limit, linear calibration range and sensitivity for chlorate, bromate and iodate detections were 0.5 μM, 2 μM to 1 mM, 8.4 nA/μM, 0.6 μM, 2 μM to 0.15 mM, 11 nA/μM, and 2.5 μM, 10 μM to 4 mM and 1.5 nA/μM, respectively. Excellent electrochemical reversibility of the redox couple, good reproducibility, high stability, low detection limit, long life time, fast amperometric response time, wide linear concentration range, technical simplicity and possibility of rapid preparation are great advantages of this sensor. The obtained results show promising practical application of the Fe(III)P-MWCNTs-modified electrode as an amperometric sensor for chlorate, iodate and

  13. Modification of glassy carbon electrode with multi-walled carbon nanotubes and iron(III)-porphyrin film: Application to chlorate, bromate and iodate detection

    Energy Technology Data Exchange (ETDEWEB)

    Salimi, Abdollah [Department of Chemistry, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Nanotechnology Research Center of University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); E-mail: absalimi@uok.ac.ir; MamKhezri, Hussein [Department of Chemistry, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Hallaj, Rahman [Department of Chemistry, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Zandi, Shiva [Laboratory of Biochemistry, Kurdistan Medical University, Sanandaj (Iran, Islamic Republic of)

    2007-06-10

    In this study, multi-wall carbon nanotubes (MWCTs) is evaluated as a transducer, stabilizer and immobilization matrix for the construction of amperometric sensor based on iron-porphyrin. 5,10,15,20-Tetraphenyl-21H,23H-porphine iron(III) chloride (Fe(III)P) adsorbed on MWCNTs immobilized on the surface of glassy carbon electrode. Cyclic voltammograms of the Fe(III)P-incorporated-MWCNTs indicate a pair of well-defined and nearly reversible redox couple with surface confined characteristics at wide pH range (2-12). The surface coverage ({gamma}) and charge transfer rate constant (k {sub s}) of Fe(III)P immobilized on MWCNTs were 7.68 x 10{sup -9} mol cm{sup -2} and 1.8 s{sup -1}, respectively, indicating high loading ability of MWCNTs for Fe(III)P and great facilitation of the electron transfer between Fe(III)P and carbon nanotubes immobilized on the electrode surface. Modified electrodes exhibit excellent electrocatalytic activity toward reduction of ClO{sub 3} {sup -}, IO{sub 3} {sup -} and BrO{sub 3} {sup -} in acidic solutions. The catalytic rate constants for catalytic reduction of bromate, chlorate and iodate were 6.8 x 10{sup 3}, 7.4 x 10{sup 3} and 4.8 x 10{sup 2} M{sup -1} s{sup -1}, respectively. The hydrodynamic amperometry of rotating-modified electrode at constant potential versus reference electrode was used for detection of bromate, chlorate and iodate. The detection limit, linear calibration range and sensitivity for chlorate, bromate and iodate detections were 0.5 {mu}M, 2 {mu}M to 1 mM, 8.4 nA/{mu}M, 0.6 {mu}M, 2 {mu}M to 0.15 mM, 11 nA/{mu}M, and 2.5 {mu}M, 10 {mu}M to 4 mM and 1.5 nA/{mu}M, respectively. Excellent electrochemical reversibility of the redox couple, good reproducibility, high stability, low detection limit, long life time, fast amperometric response time, wide linear concentration range, technical simplicity and possibility of rapid preparation are great advantages of this sensor. The obtained results show promising practical

  14. Electrochemical behaviors and simultaneous determination of guanine and adenine based on graphene–ionic liquid–chitosan composite film modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Niu Xiuli; Yang Wu; Ren Jie; Guo Hao; Long Shijia; Chen Jiaojiao; Gao Jinzhang

    2012-01-01

    Highlights: ► This work developed a novel electrochemical biosensors for guanine and adenine detection simultaneously. ► A disposable electrode based on graphene sheets, ionic liquid and chitosan was proposed. ► The presented method was also applied to simultaneous determination of guanine and adenine in denatured DNA samples with satisfying results. ► Easy fabrication, high sensitivity, excellent reproducibility and long-term stability. - Abstract: A graphene sheets (GS), ionic liquid (IL) and chitosan (CS) modified electrode was fabricated and the modified electrode displayed excellent electrochemical catalytic activities toward guanine and adenine. The transfer electron number (n) and the charge transfer coefficient (α) were calculated with the result as n = 2, α = 0.58 for guanine, and n = 2, α = 0.51 for adenine, which indicated the electrochemical oxidation of guanine and adenine on GS/IL/CS modified electrode was a two-electron and two-proton process. The oxidation overpotentials of guanine and adenine were decreased significantly compared with those obtained at the bare glassy carbon electrode and multi-walled carbon nanotubes modified electrode. The modified electrode exhibited good analytical performance and was successfully applied for individual and simultaneous determination of guanine and adenine. Low detection limits of 0.75 μM for guanine and 0.45 μM for adenine were obtained, with the linear calibration curves over the concentration range 2.5–150 μM and 1.5–350 μM, respectively. At the same time, the proposed method was successfully applied for the determination of guanine and adenine in denatured DNA samples with satisfying results. Moreover, the GS/IL/CS modified electrode exhibited good sensitivity, long-term stability and reproducibility for the determination of guanine and adenine.

  15. A sensitive DNA biosensor fabricated from gold nanoparticles, carbon nanotubes, and zinc oxide nanowires on a glassy carbon electrode

    International Nuclear Information System (INIS)

    Wang Jie; Li Shuping; Zhang Yuzhong

    2010-01-01

    We outline here the fabrication of a sensitive electrochemical DNA biosensor for the detection of sequence-specific target DNA. Zinc oxide nanowires (ZnONWs) were first immobilized on the surface of a glassy carbon electrode. Multi-walled carbon nanotubes (MWCNTs) with carboxyl groups were then dropped onto the surface of the ZnONWs. Gold nanoparticles (AuNPs) were subsequently introduced to the surface of the MWNTs/ZnONWs by electrochemical deposition. A single-stranded DNA probe with a thiol group at the end (HS-ssDNA) was covalently immobilized on the surface of the AuNPs by forming an Au-S bond. Scanning electron microscopy (SEM) and cyclic voltammetry (CV) were used to investigate the film assembly process. Differential pulse voltammetry (DPV) was used to monitor DNA hybridization by measuring the electrochemical signals of [Ru(NH 3 ) 6 ] 3+ bounding to double-stranded DNA (dsDNA). The incorporation of ZnONWs and MWCNTs in this sensor design significantly enhances the sensitivity and the selectivity. This DNA biosensor can detect the target DNA quantitatively in the range of 1.0 x 10 -13 to 1.0 x 10 -7 M, with a detection limit of 3.5 x 10 -14 M (S/N = 3). In addition, the DNA biosensor exhibits excellent selectivity, even for single-mismatched DNA detection.

  16. An aptasensor for voltammetric and impedimetric determination of cocaine based on a glassy carbon electrode modified with platinum nanoparticles and using rutin as a redox probe

    International Nuclear Information System (INIS)

    Roushani, Mahmoud; Shahdost-fard, Faezeh

    2016-01-01

    We describe a method for the determination of cocaine that is based on a glassy carbon electrode modified with a nanocomposite consisting of multiwalled carbon nanotubes, an ionic liquid, and chitosan. The electrode was made cocaine-responsive by immobilizing a cocaine-specific aptamer and platinum nanoparticles (PtNPs) on the modified electrode. The use of PtNPs resulted in the acceleration of the electron transfer kinetics of the reduction of the redox probe rutin and enhances sensitivity. The sensor, best operated at a working voltage of 260 mV vs. Ag/AgCl, has a linear response to cocaine in the 1 nM to 11 μM concentration range, and the detection limit is 100 pM (at an S/N ratio of 3). We think this strategy to represent a promising platform for the sensitive and selective determination of cocaine. The sensor is adequately stable and was successfully applied to the determination of cocaine in spiked serum. (author)

  17. Sensitive electrochemical determination of α-fetoprotein using a glassy carbon electrode modified with in-situ grown gold nanoparticles, graphene oxide and MWCNTs acting as signal amplifiers

    International Nuclear Information System (INIS)

    Gao, Yan-Sha; Zhu, Xiao-Fei; Yang, Tao-Tao; Xu, Jing-Kun; Zhang, Kai-Xin; Lu, Li-Min

    2015-01-01

    The authors describe an electrochemical immunoassay for α-fetoprotein (α-FP) using a glassy carbon electrode (GCE) modified with a nanocomposite made from gold nanoparticles, graphene oxide and multi-walled carbon nanotubes (AuNPs/GO-MWCNTs) and acting as a signal amplification matrix. The nanocomposite was synthesized in a one-pot redox reaction between GO and HAuCl 4 without using an additional reductant. The stepwise assembly of the immunoelectrode was characterized by means of cyclic voltammetry and electrochemical impedance spectroscopy. The interaction of antigen and antibody on the surface of the electrode creates a barrier for electrons and causes retarded electron transfer, this resulting in decreased signals in differential pulse voltammetry of hexacyanoferrate which is added as an electrochemical probe. Using this strategy and by working at a potential of 0.2 V (vs. SCE), a wide analytical range (0.01 - 100 ng∙mL -1 ) is covered. The correlation coefficient is 0.9929, and the limit of detection is as low as 3 pg∙mL -1 at a signal-to-noise ratio of 3. This electrochemical immunoassay combines the specificity of an immunological detection scheme with the sensitivity of an electrode modified with AuNPs and GO-MWCNTs. (author)

  18. Alizarin red S functionalized mesoporous silica modified glassy carbon electrode for electrochemical determination of anthracene

    International Nuclear Information System (INIS)

    Liu, Shan; Wei, Maochao; Zheng, Xiangli; Xu, Shuai; Xia, Fangquan; Zhou, Changli

    2015-01-01

    Highlights: • Alizarin red S-SBA15 composite was prepared and characterized. • A novel sensing platform was constructed for anthracene determination. • The proposed sensor exhibited high sensitivity and low detection limit for detecting anthracene. • This method can be applied to the practical detection of anthracene in waste water. - Abstract: In the paper, a novel and sensitive electrochemical sensor based on modification of electroactive alizarin red S functionalized mesoporous silica material SBA15 onto glassy carbon electrode (ARS-SBA15/GCE) was developed. Alizarin red S, called electrochemical probe that can selectively recognize polycyclic aromatic hydrocarbons (PAHs), as tools for the detection of tricyclic aromatic hydrocarbon anthracene. The morphology and interface property of ARS modified SBA15 (ARS-SBA15) were examined by transmission electron microscopy (TEM) and fourier transform infrared spectroscopy (FTIR). Taking advantage of the π-π stacking force between alizarin red S and anthracene, the ARS-SBA15/GCE sensor could detect anthracene quantitatively in a wide range of 1.0 pM–10.0 nM and a low detection limit of 0.5 pM (S/N = 3). Other PAHs, such as naphthalene, phenanthrene, pyrene, and benzo[a]pyrene show little interference on the detection. Consequently, a simple and sensitive electrochemical method was proposed for the determination of anthracene, which can be used to determine anthracene in waste water samples. The electrochemical method provides a general tool that complements the commonly used spectroscopic methods and immune method for the detection of PAHs

  19. Nano-structured Ni(II)-curcumin modified glassy carbon electrode for electrocatalytic oxidation of fructose

    International Nuclear Information System (INIS)

    Elahi, M. Yousef; Mousavi, M.F.; Ghasemi, S.

    2008-01-01

    A nano-structured Ni(II)-curcumin (curcumin: 1,7-bis[4-hydroxy-3-methoxyphenyl]-1,6-heptadiene-3,5-dione) film is electrodeposited on a glassy carbon electrode in alkaline solution. The morphology of polyNi(II)-curcumin (NC) was investigated by scanning electron microscopy (SEM). The SEM results show NC has a nano-globular structure in the range 20-50 nm. Using cyclic voltammetry, linear sweep voltammetry, chronoamperometry, steady-state polarization measurements and electrochemical impedance spectroscopy (EIS) showed that the nano-structure NC film acts as an efficient material for the electrocatalytic oxidation of fructose. According to the voltammetric studies, the increase in the anodic peak current and subsequent decrease in the corresponding cathodic current, fructose was oxidized on the electrode surface via an electrocatalytic mechanism. The EIS results show that the charge-transfer resistance has as a function of fructose concentration, time interval and applied potential. The increase in the fructose concentration and time interval in fructose solution results in enhanced charge transfer resistance in Nyquist plots. The EIS results indicate that fructose electrooxidation at various potentials shows different impedance behaviors. At lower potentials, a semicircle is observed in the first quadrant of impedance plot. With further increase of the potential, a transition of the semicircle from the first to the second quadrant occurs. Also, the results obtained show that the rate of fructose electrooxidation depends on concentration of OH - . Electron transfer coefficient, diffusion coefficient and rate constant of the electrocatalytic oxidation reaction are obtained. The modified electrode was used as a sensor for determination of fructose with a good dynamic range and a low detection limit

  20. Nanocomposite fibers and film containing polyolefin and surface-modified carbon nanotubes

    Science.gov (United States)

    Chu,Benjamin; Hsiao, Benjamin S.

    2010-01-26

    Methods for modifying carbon nanotubes with organic compounds are disclosed. The modified carbon nanotubes have enhanced compatibility with polyolefins. Nanocomposites of the organo-modified carbon nanotubes and polyolefins can be used to produce both fibers and films having enhanced mechanical and electrical properties, especially the elongation-to-break ratio and the toughness of the fibers and/or films.

  1. Modifying the electronic and optical properties of carbon nanotubes

    Science.gov (United States)

    Kinder, Jesse M.

    The intrinsic electronic and optical properties of carbon nanotubes make them promising candidates for circuit elements and LEDs in nanoscale devices. However, applied fields and interactions with the environment can modify these intrinsic properties. This dissertation is a theoretical study of perturbations to an ideal carbon nanotube. It illustrates how transport and optical properties of carbon nanotubes can be adversely affected or intentionally modified by the local environment. The dissertation is divided into three parts. Part I analyzes the effect of a transverse electric field on the single-electron energy spectrum of semiconducting carbon nanotubes. Part II analyzes the effect of the local environment on selection rules and decay pathways relevant to dark excitons. Part III is a series of 26 appendices. Two different models for a transverse electric field are introduced in Part I. The first is a uniform field perpendicular to the nanotube axis. This model suggests the field has little effect on the band gap until it exceeds a critical value that can be tuned with strain or a magnetic field. The second model is a transverse field localized to a small region along the nanotube axis. The field creates a pair of exponentially localized bound states but has no effect on the band gap for particle transport. Part II explores the physics of dark excitons in carbon nanotubes. Two model calculations illustrate the effect of the local environment on allowed optical transitions and nonradiative recombination pathways. The first model illustrates the role of inversion symmetry in the optical spectrum. Broken inversion symmetry may explain low-lying peaks in the exciton spectrum of boron nitride nanotubes and localized photoemission around impurities and interfaces in carbon nanotubes. The second model in Part II suggests that free charge carriers can mediate an efficient nonradiative decay process for dark excitons in carbon nanotubes. The appendices in Part III

  2. Electrochemistry of metoclopramide at multi-walled carbon nanotube modified electrode and its voltammetric detection.

    Science.gov (United States)

    Guo, Wei; Geng, Mingjiang; Zhou, Lingyun

    2012-01-01

    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.

  3. Glassy carbon electrodes modified with hemin-carbon nanomaterial films for amperometric H2O2 and NO2− detection

    International Nuclear Information System (INIS)

    Valentini, Federica; Cristofanelli, Lara; Carbone, Marilena; Palleschi, Giuseppe

    2012-01-01

    In this work a new chemical sensor for the H 2 O 2 and nitrite amperometric detection was assembled, using a glassy carbon (GC) bare electrode modified by two different nanocomposite materials. The nanocomposite films were prepared by casting a functionalised carbon nanofiber (CNF-COOH) and single-walled carbon nanotubes (SWCNT-OH, for comparison) on the glassy carbon electrode surface; then an iron(III) protoporphyrin IX (Fe(III)P) was adsorbed on these modified surfaces. A morphological investigation of the nanocomposite layers was also carried out, using the Scanning Electron Microscopy (SEM). The electrochemical characterization, performed optimising several electro-analytical parameters (such as different medium, pH, temperature, scan rate, and potential window), demonstrated that the direct electrochemistry of the Fe(III)P/Fe(II)P redox couple involves 1e − /1H + process. A kinetic evaluation of the electron-transfer reaction mechanism was also carried out, demonstrating that the heterogeneous electron transfer rate constant resulted higher at CNF/hemin/GC biosensor than that evaluated at SWCNT/hemin/GC modified electrode. Finally, the electrocatalytic activity toward the H 2 O 2 reduction was also demonstrated for both sensors but better results were observed working at CNF/hemin/GC modified electrode, especially in terms of an extended linearity (ranging from 50 to 1000 μM), a lower detection limit (L.O.D. = 3σ) of 2.0 × 10 −6 M, a higher sensitivity of 2.2 × 10 −3 A M −1 cm −2 , a fast response time (9 s), a good reproducibility (RSD% −3 to 2.5 × 10 −1 M), a lower detection limit (L.O.D. = 3σ) of 3.18 × 10 −4 M, a higher sensitivity of 1.2 × 10 −2 A M −1 cm −2 , a fast response time of 10 s, a good reproducibility (RSD% <1, n = 3) and finally a good operational stability.

  4. Anodic stripping voltammetric determination of mercury using multi-walled carbon nanotubes film coated glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Yi, Hongchao [Department of Environmental Engineering, Hubei Agriculture College, 434103, Jingzhou (China)

    2003-10-01

    An electrochemical method for the determination of trace levels of mercury based on a multi-walled carbon nanotubes (MWNT) film coated glassy carbon electrode (GCE) is described. In 0.1 mol L{sup -1} HCl solution containing 0.02 mol L{sup -1} KI, Hg{sup 2+} was firstly preconcentrated at the MWNT film and then reduced at -0.60 V. During the anodic potential sweep, reduced mercury was oxidized, and then a sensitive and well-defined stripping peak at about -0.20 V appeared. Under identical conditions, a MWNT film coated GCE greatly enhances the stripping peak current of mercury in contrast to a bare GCE. Low concentrations of I{sup -} remarkably improve the determining sensitivity, since this increases the accumulation efficiency of Hg{sup 2+} at the MWNT film coated GCE. The stripping peak current is proportional to the concentration of Hg{sup 2+} over the range 8 x 10{sup -10}-5 x 10{sup -7} mol L{sup -1}. The lowest detectable concentration of Hg{sup 2+} is 2 x 10{sup -10} mol L{sup -1} at 5 min accumulation. The relative standard deviation (RSD) at 1 x 10{sup -8} mol L{sup -1} Hg{sup 2+} was about 6% (n=10). By using this proposed method, Hg{sup 2+} in some water samples was determined, and the results were compared with those obtained by atomic absorption spectrometry (AAS). The two results are similar, suggesting that the MWNT-film coated GCE has great potential in practical analysis. (orig.)

  5. Differential pulse voltammetric determination of nanomolar concentrations of antiviral drug acyclovir at polymer film modified glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Dorraji, Parisa S.; Jalali, Fahimeh, E-mail: fjalali@razi.ac.ir

    2016-04-01

    An electrochemical sensor for the sensitive detection of acyclovir was developed by the electropolymerization of Eriochrome black T at a pretreated glassy carbon electrode. The surface morphology of the modified electrode was characterized by field emission scanning electron microscopy. Under the optimized conditions, a significant electrochemical improvement was observed toward the electrooxidation of acyclovir on the modified electrode surface relative to the unmodified electrode. The detection limit of 12 nM and two linear calibration ranges of 0.03–0.3 μM and 0.3–1.5 μM were obtained for acyclovir determination using a differential pulse voltammetric method in acetate buffer (0.1 M, pH 4.0). Real sample studies were carried out in human blood serum and pharmaceutical formulations, which offered good recovery (98–102%). The electrode showed excellent reproducibility, selectivity and antifouling effects. - Graphical abstract: Eriochrome black T (EBT) was electropolymerized at the surface of a pretreated glassy carbon electrode. The modified electrode enhanced the oxidation current of acyclovir, significantly. The sensor was used in the determination of acyclovir in human blood serum samples and pharmaceutical dosages. - Highlights: • Construction of a voltammetric sensor for acyclovir is described. • Eriochrome black T was electropolymerized at the electrode surface. • The sensor improved the sensitivity of the electrode for monitoring acyclovir. • The recoveries and standard deviations were acceptable in spiked human blood serum. • The proposed sensor had good lifetime to be used in biological matrices.

  6. A 3D Microfluidic Chip for Electrochemical Detection of Hydrolysed Nucleic Bases by a Modified Glassy Carbon Electrode

    Directory of Open Access Journals (Sweden)

    Jana Vlachova

    2015-01-01

    Full Text Available Modification of carbon materials, especially graphene-based materials, has wide applications in electrochemical detection such as electrochemical lab-on-chip devices. A glassy carbon electrode (GCE modified with chemically alternated graphene oxide was used as a working electrode (glassy carbon modified by graphene oxide with sulphur containing compounds and Nafion for detection of nucleobases in hydrolysed samples (HCl pH = 2.9, 100 °C, 1 h, neutralization by NaOH. It was found out that modification, especially with trithiocyanuric acid, increased the sensitivity of detection in comparison with pure GCE. All processes were finally implemented in a microfluidic chip formed with a 3D printer by fused deposition modelling technology. As a material for chip fabrication, acrylonitrile butadiene styrene was chosen because of its mechanical and chemical stability. The chip contained the one chamber for the hydrolysis of the nucleic acid and another for the electrochemical detection by the modified GCE. This chamber was fabricated to allow for replacement of the GCE.

  7. A 3D microfluidic chip for electrochemical detection of hydrolysed nucleic bases by a modified glassy carbon electrode.

    Science.gov (United States)

    Vlachova, Jana; Tmejova, Katerina; Kopel, Pavel; Korabik, Maria; Zitka, Jan; Hynek, David; Kynicky, Jindrich; Adam, Vojtech; Kizek, Rene

    2015-01-22

    Modification of carbon materials, especially graphene-based materials, has wide applications in electrochemical detection such as electrochemical lab-on-chip devices. A glassy carbon electrode (GCE) modified with chemically alternated graphene oxide was used as a working electrode (glassy carbon modified by graphene oxide with sulphur containing compounds and Nafion) for detection of nucleobases in hydrolysed samples (HCl pH = 2.9, 100 °C, 1 h, neutralization by NaOH). It was found out that modification, especially with trithiocyanuric acid, increased the sensitivity of detection in comparison with pure GCE. All processes were finally implemented in a microfluidic chip formed with a 3D printer by fused deposition modelling technology. As a material for chip fabrication, acrylonitrile butadiene styrene was chosen because of its mechanical and chemical stability. The chip contained the one chamber for the hydrolysis of the nucleic acid and another for the electrochemical detection by the modified GCE. This chamber was fabricated to allow for replacement of the GCE.

  8. Differential pulse voltammetric determination of nanomolar concentrations of antiviral drug acyclovir at polymer film modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Dorraji, Parisa S.; Jalali, Fahimeh

    2016-01-01

    An electrochemical sensor for the sensitive detection of acyclovir was developed by the electropolymerization of Eriochrome black T at a pretreated glassy carbon electrode. The surface morphology of the modified electrode was characterized by field emission scanning electron microscopy. Under the optimized conditions, a significant electrochemical improvement was observed toward the electrooxidation of acyclovir on the modified electrode surface relative to the unmodified electrode. The detection limit of 12 nM and two linear calibration ranges of 0.03–0.3 μM and 0.3–1.5 μM were obtained for acyclovir determination using a differential pulse voltammetric method in acetate buffer (0.1 M, pH 4.0). Real sample studies were carried out in human blood serum and pharmaceutical formulations, which offered good recovery (98–102%). The electrode showed excellent reproducibility, selectivity and antifouling effects. - Graphical abstract: Eriochrome black T (EBT) was electropolymerized at the surface of a pretreated glassy carbon electrode. The modified electrode enhanced the oxidation current of acyclovir, significantly. The sensor was used in the determination of acyclovir in human blood serum samples and pharmaceutical dosages. - Highlights: • Construction of a voltammetric sensor for acyclovir is described. • Eriochrome black T was electropolymerized at the electrode surface. • The sensor improved the sensitivity of the electrode for monitoring acyclovir. • The recoveries and standard deviations were acceptable in spiked human blood serum. • The proposed sensor had good lifetime to be used in biological matrices.

  9. Modified positron annihilation model for glassy-like As2Se3

    International Nuclear Information System (INIS)

    Kozdras, A.; Shpotyuk, O.; Kovalskiy, A.; Filipecki, J.

    2005-01-01

    An approach to structural characterization of chalcogenide glasses based on the study of void distribution is discussed. The results of positron annihilation lifetime spectra measurements for glassy As 2 Se 3 are compared with nano-void distribution data obtained from Monte Carlo simulation. In this consideration perspectives to involve the parameters of nano-voids calculated from the first sharp diffraction peak in the frame work of known Elliott's model are analyzed. (author)

  10. Photogeneration of singlet oxygen by the phenothiazine derivatives covalently bound to the surface-modified glassy carbon

    Energy Technology Data Exchange (ETDEWEB)

    Blacha-Grzechnik, Agata, E-mail: agata.blacha@polsl.pl [Faculty of Chemistry, Silesian University of Technology, Strzody 9, 44-100 Gliwice (Poland); Piwowar, Katarzyna; Krukiewicz, Katarzyna [Faculty of Chemistry, Silesian University of Technology, Strzody 9, 44-100 Gliwice (Poland); Koscielniak, Piotr; Szuber, Jacek [Institute of Electronics, Silesian University of Technology, Akademicka 16, 44-100 Gliwice (Poland); Zak, Jerzy K. [Faculty of Chemistry, Silesian University of Technology, Strzody 9, 44-100 Gliwice (Poland)

    2016-05-15

    Highlights: • The selected group of four NH{sub 2}-derivatives of phenothiazine was grafted to Glassy Carbon (GC) surface. • The grafted phenothiazines are able to generate {sup 1}O{sub 2} when activated by the radiation. • Such modified solid surfaces may find their application in the wastewater treatment. - Abstract: The selected group of four amine-derivatives of phenothiazine was covalently grafted to the glassy carbon surface in the four-step procedure consisting of the electrochemical reduction of the diazonium salt followed by the electrochemical and chemical post-modification steps. The proposed strategy involves the bonding of linker molecule to which the photosensitizer is attached. The synthesized organic layers were characterized by means of cyclic voltammetry, XPS and Raman Spectroscopy. It was shown that the phenothiazines immobilized via proposed strategy retain their photochemical properties and are able to generate {sup 1}O{sub 2} when activated by the laser radiation. The effectiveness of in situ singlet oxygen generation by those new solid photoactive materials was determined by means of UVVis spectroscopy. The reported, covalently modified solid surfaces may find their application as the singlet oxygen photogenerators in the fine chemicals’ synthesis or in the wastewater treatment.

  11. Electrocatalytical oxidation and sensitive determination of acetaminophen on glassy carbon electrode modified with graphene–chitosan composite

    International Nuclear Information System (INIS)

    Zheng, Meixia; Gao, Feng; Wang, Qingxiang; Cai, Xili; Jiang, Shulian; Huang, Lizhang; Gao, Fei

    2013-01-01

    The electrochemical behaviors of acetaminophen (ACOP) on a graphene–chitosan (GR–CS) nanocomposite modified glassy carbon electrode (GCE) were investigated by cyclic voltammetry (CV), chronocoulometry (CC) and differential pulse voltammetry (DPV). Electrochemical characterization showed that the GR–CS nanocomposite had excellent electrocatalytic activity and surface area effect. As compared with bare GCE, the redox signal of ACOP on GR–CS/GCE was greatly enhanced. The values of electron transfer rate constant (k s ), diffusion coefficient (D) and the surface adsorption amount (Γ ⁎ ) of ACOP on GR–CS/GCE were determined to be 0.25 s −1 , 3.61 × 10 −5 cm 2 s −1 and 1.09 × 10 −9 mol cm −2 , respectively. Additionally, a 2e − /2H + electrochemical reaction mechanism of ACOP was deduced based on the acidity experiment. Under the optimized conditions, the ACOP could be quantified in the range from 1.0 × 10 −6 to 1.0 × 10 −4 M with a low detection limit of 3.0 × 10 −7 M based on 3S/N. The interference and recovery experiments further showed that the proposed method is acceptable for the determination of ACOP in real pharmaceutical preparations. Highlights: ► A chitosan–graphene nanocomposite modified glassy carbon electrode was prepared. ► The modified electrode was electrochemically characterized by CV and EIS. ► Electro-oxidation of acetaminophen was examined on the modified electrode. ► Sensing analysis of the modified electrode toward acetaminophen was studied

  12. Explosive compaction of aluminum oxide modified by multiwall carbon nanotubes

    Science.gov (United States)

    Buzyurkin, A. E.; Kraus, E. I.; Lukyanov, Ya L.

    2018-04-01

    This paper presents experiments and numerical research on explosive compaction of aluminum oxide powder modified by multiwall carbon nanotubes (MWCNT) and modeling of the stress state behind the shock front at shock loading. The aim of this study was to obtain a durable low-porosity compact sample. The explosive compaction technology is used in this problem because the aluminum oxide is an extremely hard and refractory material. Therefore, its compaction by traditional methods requires special equipment and considerable expenses.

  13. Low temperature electrical transport in modified carbon nanotube fibres

    International Nuclear Information System (INIS)

    Lekawa-Raus, Agnieszka; Walczak, Kamil; Kozlowski, Gregory; Hopkins, Simon C.; Wozniak, Mariusz; Glowacki, Bartek A.; Koziol, Krzysztof

    2015-01-01

    Carbon nanotube fibres are a new class of materials highly promising for many electrical/electronic applications. The range of applications could be extended through the modification of their electrical transport properties by inclusions of foreign materials. However, the changes in electrical transport are often difficult to assess. Here, we propose that the analysis of resistance–temperature dependencies of modified fibres supported by a recently developed theoretical model may aid research in this area and accelerate real life applications of the fibres

  14. Glucose biosensing using glassy carbon electrode modified with polyhydroxy-C60, glucose oxidase and ionic-liquid.

    Science.gov (United States)

    Yang, Tian; Yang, Xiao-Lu; Zhang, Yu-Shuai; Xiao, BaoLin; Hong, Jun

    2014-01-01

    Direct electrochemistry of glucose oxidase (GOD) was achieved when an ionic liquid/GOD-Polyhydroxy-C60 functional membrane was confined on a glassy carbon electrode (GCE). The cyclic voltammograms (CVs) of the modified GCE showed a pair of redox peaks with a formal potential (E°') of - 329 ± 2 mV. The heterogeneous electron transfer constant (k(s)) was 1.43 s-1. The modified GCE response to glucose was linear in the range from 0.02 to 2.0 mM. The detection limit was 1 μM. The apparent Michaelis-Menten constant (K(m)(app)) was 1.45 mM.

  15. Assembling gold nanorods on a poly-cysteine modified glassy carbon electrode strongly enhance the electrochemical response to tetrabromobisphenol A

    International Nuclear Information System (INIS)

    Wang, Yanying; Liu, Guishen; Hou, Xiaodong; Huang, Yina; Li, Chunya; Wu, Kangbing

    2016-01-01

    Cysteine (Cys) was electrochemically deposited on a glassy carbon electrode (GCE) by cyclic voltammetry. The poly-Cys modified electrode was placed in a solution of gold nanorods (GNRs) to induced self-assembly of the GNRs. The GNRs/poly-Cys/GCEs were characterized by scanning electron microscopy and electrochemical impedance spectroscopy. A voltammetric study on tetrabromobisphenol A (TBBPA) with this GCE showed the current response to be enhanced by a factor of 11 compared to a non-modified GCE. Based on these findings, a square wave voltammetric assay was worked out. Under optimized conditions, a linear relationship between the oxidation peak current and TBBPA is found for the 10 nM to 10 μM concentration range. The detection limit is 3.2 nM (at an S/N ratio of 3). The electrode was successfully applied to the determination of TBBPA in spiked tap water and lake water samples. (author)

  16. A novel enzymatic glucose sensor based on Pt nanoparticles-decorated hollow carbon spheres-modified glassy carbon electrode

    Science.gov (United States)

    Luhana, Charles; Bo, Xiang-Jie; Ju, Jian; Guo, Li-Ping

    2012-10-01

    A new glucose biosensor was developed based on hollow carbon spheres decorated with platinum nanoparticles (Pt/HCSs)-modified glassy carbon electrode immobilized with glucose oxidase (GOx) with the help of Nafion. The Pt nanoparticles were well dispersed on the HCSs with an average size of 2.29 nm. The detection of glucose was achieved via electrochemical detection of the enzymatically liberated H2O2 at +0.5 V versus Ag/AgCl at physiologic pH of 7.4. The Pt/HCSs-modified electrode exhibited excellent electrocatalytic activities toward both the oxidation and reduction of H2O2. The glucose biosensor showed good electrocatalytic performance in terms of high sensitivity (4.1 μA mM-1), low detection limit (1.8 μM), fast response time tested with this biosensor and a good recovery was achieved for the two spiked serum samples.

  17. Amperometric xanthine biosensors using glassy carbon electrodes modified with electrografted porous silica nanomaterials loaded with xanthine oxidase

    International Nuclear Information System (INIS)

    Saadaoui, Maroua; Sánchez, Alfredo; Díez, Paula; Raouafi, Noureddine; Pingarrón, José M.; Villalonga, Reynaldo

    2016-01-01

    Glassy carbon electrodes were modified with silica materials such as silica nanoparticles, mesoporous silica nanoparticles and mesoporous silica thin films with the aim to introduce scaffolds suitable for the immobilization of enzymes. Xanthine oxidase was selected as a model enzyme, and xanthine as the target analyte. A comparison of the modified electrodes showed the biosensor prepared with mesoporous silica nanoparticles to perform best. By using the respective biosensor, xanthine can be amperometrically determined (via measurement of enzymatically formed hydrogen peroxide) at a working voltage of 0.7 V (vs. Ag/AgCl) with a 0.28 μM detection limit. The biosensor was evaluated in terms of potential interferences, reproducibility and stability, and applied to the determination of fish freshness via sensing of xanthine. (author)

  18. Osteoblast cell response to surface-modified carbon nanotubes

    International Nuclear Information System (INIS)

    Zhang Faming; Weidmann, Arne; Nebe, J. Barbara; Burkel, Eberhard

    2012-01-01

    In order to investigate the interaction of cells with modified multi-walled carbon nanotubes (MWCNTs) for their potential biomedical applications, the MWCNTs were chemically modified with carboxylic acid groups (–COOH), polyvinyl alcohol (PVA) polymer and biomimetic apatite on their surfaces. Additionally, human osteoblast MG-63 cells were cultured in the presence of the surface-modified MWCNTs. The metabolic activities of osteoblastic cells, cell proliferation properties, as well as cell morphology were studied. The surface modification of MWCNTs with biomimetic apatite exhibited a significant increase in the cell viability of osteoblasts, up to 67.23%. In the proliferation phases, there were many more cells in the biomimetic apatite-modified MWCNT samples than in the MWCNTs–COOH. There were no obvious changes in cell morphology in osteoblastic MG-63 cells cultured in the presence of these chemically-modified MWCNTs. The surface modification of MWCNTs with apatite achieves an effective enhancement of their biocompatibility.

  19. Enzymatic biosensor based on entrapment of d-amino acid oxidase on gold nanofilm/MWCNTs nanocomposite modified glassy carbon electrode by sol-gel network: Analytical applications for d-alanine in human serum.

    Science.gov (United States)

    Shoja, Yalda; Rafati, Amir Abbas; Ghodsi, Javad

    2017-05-01

    Sensing and determination of d-alanine is studied by using an enzymatic biosensor which was constructed on the basis of d-amino acid oxidase (DAAO) immobilization by sol-gel film onto glassy carbon electrode surface modified with nanocomposite of gold nanofilm (Au-NF) and multiwalled carbon nanotubes (MWCNTs). The Au-NF/MWCNT nanocomposite was prepared by applying the potentiostatic technique for electrodeposition of Au-NF on the MWCNT immobilized on glassy carbon electrode surface. The modified electrode is investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), linear sweep voltammetry (LSV) and cyclic voltammetry(CV) techniques. The linear sweep voltammetry was used for determination of d-alanine and the results showed an excellent linear relationship between biosensor response and d-alanine concentration ranging from 0.25μM to 4.5μM with correction coefficient of 0.999 (n=20). Detection limit for the fabricated sensor was calculated about 20nM (for S/N=3) and sensitivity was about 56.1μAμM -1 cm -2 . The developed biosensor exhibited rapid and accurate response to d-alanine, a good stability (4 weeks) and an average recovery of 98.9% in human serum samples. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. An Easily Fabricated Electrochemical Sensor Based on a Graphene-Modified Glassy Carbon Electrode for Determination of Octopamine and Tyramine

    Science.gov (United States)

    Zhang, Yang; Zhang, Meiqin; Wei, Qianhui; Gao, Yongjie; Guo, Lijuan; Al-Ghanim, Khalid A.; Mahboob, Shahid; Zhang, Xueji

    2016-01-01

    A simple electrochemical sensor has been developed for highly sensitive detection of octopamine and tyramine by electrodepositing reduced graphene oxide (ERGO) nanosheets onto the surface of a glassy carbon electrode (GCE). The electrocatalytic oxidation of octopamine and tyramine is individually investigated at the surface of the ERGO modified glassy carbon electrode (ERGO/GCE) by using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Several essential factors including the deposition cycle of reduced graphene oxide nanosheets and the pH of the running buffer were investigated in order to determine the optimum conditions. Furthermore, the sensor was applied to the quantification of octopamine and tyramine by DPV in the concentration ranges from 0.5 to 40 μM and 0.1 to 25 μM, respectively. In addition, the limits of detection of octopamine and tyramine were calculated to be 0.1 μM and 0.03 μM (S/N = 3), respectively. The sensor showed good reproducibility, selectivity and stability. Finally, the sensor successfully detected octopamine and tyramine in commercially available beer with satisfactory recovery ranges which were 98.5%–104.7% and 102.2%–103.1%, respectively. These results indicate the ERGO/GCE based sensor is suitable for the detection of octopamine and tyramine. PMID:27089341

  1. Investigation of bioresistant dry building mixes modified by carbon nanotubes

    Directory of Open Access Journals (Sweden)

    Korolev Evgeniy Valer'evich

    2015-04-01

    Full Text Available Dry construction mixes are today a product of high technologies. Depending on the purpose and requirements to the properties it is easy to produce dry construction mixes with different compositions and operating indicators in plant conditions using the necessary modifying additives. Cement, gypsum and other mineral binders are used in the construction mixes. Different types of cement are more heavily used in dry construction mixes. Such dry mixes are believed to be more effective materials comparing to traditional cement-sandy solutions of centralized preparation. The authors present the results of the investigations on obtaining biocidal cement-sand compositions. It was established, that introduction of sodium sulfate into the composition provides obtaining the materials with funginert and fungicide properties. The strength properties of the mixes modified by carbon nanotubes and biocide additive were investigated by mathematical planning methods. The results of the investigations showed that the modification of cement stone structure by carbon nanotubes positively influences their strength and technological properties. Nanomodifying of construction composites by introducing carbon nanotubes may be effectively used at different stages of structure formation of a construction material.

  2. MIPs-graphene nanoplatelets-MWCNTs modified glassy carbon electrode for the determination of cardiac troponin I.

    Science.gov (United States)

    Ma, Ya; Shen, Xiao-Lei; Wang, Hai-Shui; Tao, Jia; Huang, Jian-Zhi; Zeng, Qiang; Wang, Li-Shi

    2017-03-01

    An electrochemical sensor with high selectivity in addition to sensitivity was developed for the determination of cardiac troponin I (cTnI), based on the modification of cTnI imprinted polymer film on a glassy carbon electrode (GCE). The sensor was fabricated by layer-by-layer assembled graphene nanoplatelets (GS), multiwalled carbon nanotubes (MWCNTs), chitosan (CS), glutaraldehyde (GA) composites, which can increase the electronic transfer rate and the active surface area to capture a larger number of antigenic proteins. MWCNTs/GS based imprinted polymers (MIPs/MWCNTs/GS) were synthesized by means of methacrylic acid (MAA) as the monomer, ethylene glycol dimethacrylate (EGDMA) as the cross linker α,α'-azobisisobutyronitrile (AIBN) as the initiator and cTnI as the template. In comparison with conventional methods, the proposed electrochemical sensor is highly sensitive for cTnI, providing a better linear response range from 0.005 to 60 ng cm -3 and a lower limit of detection (LOD) of 0.0008 ng cm -3 under optimal experimental conditions. In addition, the electrochemical sensor exhibited good specificity, acceptable reproducibility and stability. Moreover, satisfactory results were obtained in real human serum samples, indicating that the developed method has the potential to find application in clinical detection of cTnI as an alternative approach. Copyright © 2016 Elsevier Inc. All rights reserved.

  3. Graphene quantum dot modified glassy carbon electrode for the determination of doxorubicin hydrochloride in human plasma

    Directory of Open Access Journals (Sweden)

    Nastaran Hashemzadeh

    2016-08-01

    Full Text Available Low toxic graphene quantum dot (GQD was synthesized by pyrolyzing citric acid in alkaline solution and characterized by ultraviolet--visible (UV–vis spectroscopy, X-ray diffraction (XRD, atomic force microscopy (AFM, spectrofluorimetery and dynamic light scattering (DLS techniques. GQD was used for electrode modification and electro-oxidation of doxorubicin (DOX at low potential. A substantial decrease in the overvoltage (−0.56 V of the DOX oxidation reaction (compared to ordinary electrodes was observed using GQD as coating of glassy carbon electrode (GCE. Differential pulse voltammetry was used to evaluate the analytical performance of DOX in the presence of phosphate buffer solution (pH 4.0 and good limit of detection was obtained by the proposed sensor. Such ability of GQD to promote the DOX electron-transfer reaction suggests great promise for its application as an electrochemical sensor.

  4. Electrochemical sensor for nitrite using a glassy carbon electrode modified with gold-copper nanochain networks

    International Nuclear Information System (INIS)

    Huang, Su-Su; Mei, Li-Ping; Zhou, Jia-Ying; Guo, Fei-Ying; Wang, Ai-Jun; Feng, Jiu-Ju; Liu, Li

    2016-01-01

    Bimetallic gold-copper nanochain networks (AuCu NCNs) were prepared by a single-step wet-chemical approach using metformin as a growth-directing agent. The formation mechanism was investigated in detail, and the AuCu NCNs were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The nanocrystals were deposited on glassy carbon electrode and this resulted in a highly sensitive sensor for nitrite. Features include a low working potential (best at 0.684 V vs. SCE), fair sensitivity (17.55 μA mM −1 ), a wide linear range (0.01 to 4.0 mM), a low detection limit (0.2 μM, S/N = 3), and superior selectivity as compared to other sensors. (author)

  5. Voltammetric Determination of Flunixin on Molecularly Imprinted Polypyrrole Modified Glassy Carbon Electrode

    Directory of Open Access Journals (Sweden)

    Abd-Elgawad Radi

    2016-01-01

    Full Text Available A novel electrochemical sensing approach, based on electropolymerization of a molecularly imprinted polypyrrole (MIPpy film onto a glassy carbon electrode (GCE surface, was developed for the detection of flunixin (FXN. The sensing conditions and the performance of the constructed sensor were assessed by cyclic, differential pulse and (DPV square wave voltammetry (SWV. The sensor exhibited high sensitivity, with linear responses in the range of 5.0 to 50.0 µM with detection limits of 1.5 and 1.0 µM for DPV and SWV, respectively. In addition, the sensor showed high selectivity towards FXN in comparison to other interferents. The sensor was successfully utilized for the direct determination of FXN in buffalo raw milk samples.

  6. Novel glucose biosensor based on a glassy carbon electrode modified with hollow gold nanoparticles and glucose oxidase

    International Nuclear Information System (INIS)

    Wang, W.; Ying, S.; Zhang, Z.; Huang, S.

    2011-01-01

    A novel glucose biosensor is presented as that based on a glassy carbon electrode modified with hollow gold nanoparticles (HGNs) and glucose oxidase. The sensor exhibits a better differential pulse voltammetric response towards glucose than the one based on conventional gold nanoparticles of the same size. This is attributed to the good biological conductivity and biocompatibility of HGNs. Under the optimal conditions, the sensor displays a linear range from 2.0 x 10 -6 to 4.6 x 10 -5 M of glucose, with a detection limit of 1.6 x 10 -6 M (S/N = 3). Good reproducibility, stability and no interference make this biosensor applicable to the determination of glucose in samples such as sports drinks. (author)

  7. Electrochemical behavior of ruthenium-hexacyanoferrate modified glassy carbon electrode and catalytic activity towards ethanol electro oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Costa, Wendell M.; Marques, Aldalea L.B., E-mail: aldalea.ufma@hotmail.com [Universidade Federal do Maranhao (UFMA), Sao Luis, MA (Brazil). Departamento de Quimica Tecnologica; Cardoso, William S.; Marques, Edmar P.; Bezerra, Cicero W.B. [Universidade Federal do Maranhao (UFMA), Sao Luis, MA (Brazil). Departamento de Qumica; Ferreira, Antonio Ap. P. [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Araraquara, SP (Brazil). Instituto de Quimica; Song, Chaojie; Zhang, Jiujun [Energy, Mining and Environment Portfolio, National Research Council of Canada, Vancouver, BC (Canada)

    2013-04-15

    Ruthenium-based hexacyanoferrate (RuHCF) thin film modified glassy carbon electrode was prepared by drop evaporation method. The RuHCF modified electrode exhibited four redox couples in strong acidic solution (pH 1.5) attributed to Fe(CN){sub 6}{sup 3-} ion and three ruthenium forms (Ru(II), Ru(III) and Ru(IV)), characteristic of ruthenium oxide compounds. The modified electrode displayed excellent electrocatalytic activity towards ethanol oxidation in the potential region where electrochemical processes Ru(III)-O-Ru(IV) and Ru(IV)-O-Ru(VI) occur. Impedance spectroscopy data indicated that the charge transfer resistance decreased with the increase of the applied potential and ethanol concentration, indicating the use of the RuHCF modified electrode as an ethanol sensor. Under optimized conditions, the sensor responded linearly and rapidly to ethanol concentration between 0.03 and 0.4 mol L{sup -1} with a limit of detection of 0.76 mmol L{sup -1}, suggesting an adequate sensitivity in ethanol analyses. (author)

  8. Electrochemical detection of L-cysteine using a boron-doped carbon nanotube-modified electrode

    International Nuclear Information System (INIS)

    Deng Chunyan; Chen Jinhua; Chen Xiaoli; Wang Mengdong; Nie Zhou; Yao Shouzhuo

    2009-01-01

    A boron-doped carbon nanotube (BCNT)-modified glassy carbon (GC) electrode was constructed for the detection of L-cysteine (L-CySH). The electrochemical behavior of BCNTs in response to L-cysteine oxidation was investigated. The response current of L-CySH oxidation at the BCNT/GC electrode was obviously higher than that at the bare GC electrode or the CNT/GC electrode. This finding may be ascribed to the excellent electrochemical properties of the BCNT/GC electrode. Moreover, on the basis of this finding, a determination of L-CySH at the BCNT/GC electrode was carried out. The effects of pH, scan rate and interferents on the response of L-CySH oxidation were investigated. Under the optimum experimental conditions, the detection response for L-CySH on the BCNT/GC electrode was fast (within 7 s). It was found to be linear from 7.8 x 10 -7 to 2 x 10 -4 M (r = 0.998), with a high sensitivity of 25.3 ± 1.2 nA mM -1 and a low detection limit of 0.26 ± 0.01 μM. The BCNT/GC electrode exhibited high stability and good resistance against interference by other oxidizable amino acids (tryptophan and tyrosine)

  9. Enhanced luminol electrochemiluminescence triggered by an electrode functionalized with dendrimers modified with titanate nanotubes

    International Nuclear Information System (INIS)

    Lin, Yanyu; Yang, Yusheng; Dai, Hong; Xu, Guifang; Yang, Ting; Tong, Yuejin; Yang, Caiping; Chen, Guonan

    2013-01-01

    We have constructed a novel electro chemiluminescence (ECL) platform by functionalizing a poly(amidoamine) dendrimer (PAAD) with titanate nanotubes (TiNTs). The PAAD has an open spherical structure that possesses a high density of active groups and thus favors mass transport, while the TiNTs possess excellent electronic conductivity and thus can promote electron transfer on the surface of a glassy carbon electrode (GCE). A study on the intensity and stability of the ECL of luminol on the modified GCE revealed a substantial improvement compared to that of a bare GCE. The effects of the concentration of TiNTs, the pH value of the solution, and of electrochemical parameters on the intensity of the ECL of luminol were studied and resulted in a sensitive ECL sensor for hydrogen peroxide (H 2 O 2 ) that works in the concentration range of 1 nM to 0.9 μM. The scavenging effect of superoxide dismutase (SOD) on the H 2 O 2 electrode ECL was then exploited to design a biosensor for the determination of SOD in concentrations between 50 and 500 nM. (author)

  10. Chronocoulometry of wine on multi-walled carbon nanotube modified electrode: Antioxidant capacity assay.

    Science.gov (United States)

    Ziyatdinova, Guzel; Kozlova, Ekaterina; Budnikov, Herman

    2016-04-01

    Phenolic antioxidants of wine were electrochemically oxidized on multi-walled carbon nanotubes modified glassy carbon electrode (MWNT/GCE) in phosphate buffer solution. Three oxidation peaks were observed at 0.39, 0.61 and 0.83V for red dry wine and 0.39, 0.80 and 1.18 V for white dry wine, respectively, using differential pulse voltammetry at pH 4.0. The oxidation potentials for individual phenolic antioxidants confirmed the integral nature of the analytical signals for the wines examined. A one-step chronocoulometric method at 0.83 and 1.18 V for red and white wines, respectively, has been developed for the evaluation of wine antioxidant capacity (AOC). The AOC is expressed in gallic acid equivalents per 1L of wine. The AOC of white wine was significantly less than red wine (386 ± 112 vs. 1224 ± 184, pwine and total antioxidant capacity, based on coulometric titration with electrogenerated bromine (r=0.8957 at n=5 and r=0.8986 at n=4 for red and white wines, respectively). Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. A novel electrochemical sensor of bisphenol A based on stacked graphene nanofibers/gold nanoparticles composite modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Niu, Xiuli; Yang, Wu; Wang, Guoying; Ren, Jie; Guo, Hao; Gao, Jinzhang

    2013-01-01

    In this paper, a novel and convenient electrochemical sensor based on stacked graphene nanofibers (SGNF) and gold nanoparticles (AuNPs) composite modified glassy carbon electrode (GCE) was developed for the determination of bisphenol A (BPA). The AuNPs/SGNF modified electrode showed an efficient electrocatalytic role for the oxidation of BPA, and the oxidation overpotentials of BPA were decreased significantly and the peak current increased greatly compared with bare GCE and other modified electrode. The transfer electron number (n) and the charge transfer coefficient (α) were calculated with the result as n = 4, α = 0.52 for BPA, which indicated the electrochemical oxidation of BPA on AuNPs/SGNF modified electrode was a four-electron and four-proton process. The effective surface areas of AuNPs/SGNF/GCE increased for about 1.7-fold larger than that of the bare GCE. In addition, the kinetic parameters of the modified electrode were calculated and the apparent heterogeneous electron transfer rate constant (k s ) was 0.51 s −1 . Linear sweep voltammetry was applied as a sensitive analytical method for the determination of BPA and a good linear relationship between the peak current and BPA concentration was obtained in the range from 0.08 to 250 μM with a detection limit of 3.5 × 10 −8 M. The modified electrode exhibited a high sensitivity, long-term stability and remarkable reproducible analytical performance and was successfully applied for the determination of BPA in baby bottles with satisfying results

  12. An amperometric penicillin biosensor with enhanced sensitivity based on co-immobilization of carbon nanotubes, hematein, and β-lactamase on glassy carbon electrode

    International Nuclear Information System (INIS)

    Chen Bi; Ma Ming; Su Xiaoli

    2010-01-01

    An amperometric penicillin biosensor with enhanced sensitivity was successfully developed by co-immobilization of multi-walled carbon nanotubes (MWCNTs), hematein, and β-lactamase on glassy carbon electrode using a layer-by-layer assembly technique. Under catalysis of the immobilized enzyme, penicillin was hydrolyzed, decreasing the local pH. The pH change was monitored amperometrically with hematein as a pH-sensitive redox probe. MWCNTs were used as an electron transfer enhancer as well as an efficient immobilization matrix for the sensitivity enhancement. The effects of immobilization procedure, working potential, enzyme quantity, buffer concentration, and sample matrix were investigated. The biosensor offered a minimum detection limit of 50 nM (19 μg L -1 ) for penicillin V, lower than those of the conventional pH change-based biosensors by more than two orders of magnitude. The electrode-to-electrode variation of the response sensitivity was 7.0% RSD.

  13. Analysis of polyphenols in white wine by CZE with amperometric detection using carbon nanotube-modified electrodes.

    Science.gov (United States)

    Moreno, Mónica; Arribas, Alberto Sánchez; Bermejo, Esperanza; Zapardiel, Antonio; Chicharro, Manuel

    2011-04-01

    A method for the simultaneous detection of five polyphenols (caffeic, chlorogenic, ferulic and gallic acids and (+)-catechin) by CZE with electrochemical detection was developed. Separation of these polyphenols was performed in a 100 mM borate buffer (pH 9.2) within 15 min. Under optimized separation conditions, the performance of glassy carbon (GC) electrodes modified with multiwalled carbon nanotube layer obtained from different dispersions was examined. GC electrode modified with a dispersion of multi-walled carbon nanotubes (CNT) in polyethylenimine has proven to be the most suitable CNT-based electrode for its application as amperometric detector for the CZE separation of the studied compounds. The excellent electrochemical properties of this electrode allowed the detection of the selected polyphenols at +200 mV and improved the efficiency and the resolution of their CZE separation. Limits of detection below 3.1 μM were obtained with linear ranges covering the 10⁻⁵ to 10⁻⁴  M range. The proposed method has been successfully applied for the detection (ferulic, caffeic and gallic acids and (+)-catechin) and the quantification (gallic acid and (+)-catechin) of polyphenols in two different white wines without any preconcentration step. A remarkable signal stability was observed on the electrode performance despite the presence of potential fouling substances in wine. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. MIP-graphene-modified glassy carbon electrode for the determination of trimethoprim.

    Science.gov (United States)

    da Silva, Hélder; Pacheco, João G; Magalhães, Júlia M C S; Viswanathan, Subramanian; Delerue-Matos, Cristina

    2014-02-15

    A novel sensitive electrochemical sensor was developed by electropolymerization of pyrrole (PY) and molecularly imprinted polymer (MIP) which was synthesized onto a glassy carbon electrode (GCE) in aqueous solution using cyclic voltammetry in the presence of Trimethoprim (TMP) as template molecules. Furthermore, a previous electrode modification was performed by deposition of a suspension of graphene on the electrode's surface. The performance of the imprinted and non-imprinted (NIP) films was evaluated by impedance spectroscopy (EIS) and cyclic voltammetry (CV) of a ferric solution. The molecularly imprinted film exhibited a high selectivity and sensitivity toward TMP. The sensor presented a linear range, between peak current intensity and logarithm of TMP concentration between 1.0 × 10(-6) and 1.0 × 10(-4)M. The results were accurate (with recoveries higher than 94%), precise (with standard deviations less than 5%) and the detection limit was 1.3 × 10(-7)M. The new sensor is selective, simple to construct and easy to operate. The MIP sensor was successfully applied to quantify TMP in urine samples. © 2013 Elsevier B.V. All rights reserved.

  15. Direct growth of metal-organic frameworks thin film arrays on glassy carbon electrode based on rapid conversion step mediated by copper clusters and hydroxide nanotubes for fabrication of a high performance non-enzymatic glucose sensing platform.

    Science.gov (United States)

    Shahrokhian, Saeed; Khaki Sanati, Elnaz; Hosseini, Hadi

    2018-07-30

    The direct growth of self-supported metal-organic frameworks (MOFs) thin film can be considered as an effective strategy for fabrication of the advanced modified electrodes in sensors and biosensor applications. However, most of the fabricated MOFs-based sensors suffer from some drawbacks such as time consuming for synthesis of MOF and electrode making, need of a binder or an additive layer, need of expensive equipment and use of hazardous solvents. Here, a novel free-standing MOFs-based modified electrode was fabricated by the rapid direct growth of MOFs on the surface of the glassy carbon electrode (GCE). In this method, direct growth of MOFs was occurred by the formation of vertically aligned arrays of Cu clusters and Cu(OH) 2 nanotubes, which can act as both mediator and positioning fixing factor for the rapid formation of self-supported MOFs on GCE surface. The effect of both chemically and electrochemically formed Cu(OH) 2 nanotubes on the morphological and electrochemical performance of the prepared MOFs were investigated. Due to the unique properties of the prepared MOFs thin film electrode such as uniform and vertically aligned structure, excellent stability, high electroactive surface area, and good availability to analyte and electrolyte diffusion, it was directly used as the electrode material for non-enzymatic electrocatalytic oxidation of glucose. Moreover, the potential utility of this sensing platform for the analytical determination of glucose concentration was evaluated by the amperometry technique. The results proved that the self-supported MOFs thin film on GCE is a promising electrode material for fabricating and designing non-enzymatic glucose sensors. Copyright © 2018 Elsevier B.V. All rights reserved.

  16. Laccase on Black Pearl 2000 modified glassy carbon electrode: Characterization of direct electron transfer and biological sensing properties for pyrocatechol

    International Nuclear Information System (INIS)

    Wang Kunqi; Tang Juan; Zhang Zuoming; Gao Ying; Chen Gang

    2012-01-01

    Highlights: ► Laccase can complete direct electron transfer process on BP2000 matrices. ► Laccase immobilized on BP2000 matrices has catalytic oxidation effect to pyrocatechol. ► A pyrocatechol biosensor has constructed been using Nafion/Lac-BP2000/GC electrode. ► Detection limit and linear range of the biosensor are 0.003 mM and 0.003–5.555 mM. - Abstract: In this paper, it was found that Laccase (Lac) could be stably immobilized on the glassy carbon electrode modified with Black Pearl 2000 (BP2000) and Nafion by a simple technique. The adsorption behavior of Lac immobilized on BP2000 matrix was characterized by environment scanning electron microscope (ESEM), ultraviolet–visible (UV–vis) and Fourier transform infrared (FTIR), which demonstrated that BP2000 could facilitate the electron exchange between the active center of Lac and modified electrode. The direct electrochemistry and electrocatalysis behavior of Lac on the modified electrode were characterized by cyclic voltammogram (CV) which indicated that Lac immobilized on the modified electrode displayed a direct, nearly reversible and surface-controlled redox reaction with an enhanced electron-transfer rate constant of 1.940 s −1 at the scan rate of 100 mV s −1 in 0.1 M phosphate buffer solution (PBS) (pH 7.0). Furthermore, it was also discovered that, in the presence of O 2 , Lac immobilized on the modified electrode exhibited the electrocatalytic response to pyrocatechol, and the kinetic apparent Michaelis-constant (K M app ) obtained from the Lineweaver–Burk equation was 1.79 mM. The detection limit, linear range and sensitivity of the Lac biosensor were 0.003 mM, 0.003–5.555 mM and 99.84 μA mM −1 cm −2 , respectively.

  17. MWCNTs/Cu(OH)2 nanoparticles/IL nanocomposite modified glassy carbon electrode as a voltammetric sensor for determination of the non-steroidal anti-inflammatory drug diclofenac

    International Nuclear Information System (INIS)

    Arvand, Majid; Gholizadeh, Tahereh M.; Zanjanchi, Mohammad Ali

    2012-01-01

    This paper describes the development and utilization of a new nanocomposite consisting of Cu(OH) 2 nanoparticles, hydrophobic ionic liquid 1-ethyl-3-methylimidazolium hexafluorophosphate (EMIMPF 6 ) and multiwalled carbon nanotubes for glassy carbon electrode modification. The nanocomposite was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) along with energy-dispersive X-ray spectroscopy (EDX). The modified electrode was used for electrochemical characterization of diclofenac. Using differential pulse voltammetry, the prepared sensor showed good sensitivity and selectivity with low overpotential for the determination of diclofenac in the range from 0.18 to 119 μM, with a detection limit of 0.04 μM. Electrochemical studies suggested that the MWCNTs/Cu(OH) 2 nanoparticles/IL nanocomposite modified electrode provided a synergistic augmentation on the voltammetric behavior of electrochemical oxidation of diclofenac, which was indicated by the improvement of anodic peak current. Highlights: ► This work examines oxidation of diclofenac at a nanocomposite modified electrode. ► The salient feature of this electrode is large diffusion coefficient. ► The proposed electrode decreased overpotential of diclofenac electrooxidation. ► The modified electrode has good stability and reproducibility.

  18. MWCNTs/Cu(OH){sub 2} nanoparticles/IL nanocomposite modified glassy carbon electrode as a voltammetric sensor for determination of the non-steroidal anti-inflammatory drug diclofenac

    Energy Technology Data Exchange (ETDEWEB)

    Arvand, Majid, E-mail: arvand@guilan.ac.ir; Gholizadeh, Tahereh M.; Zanjanchi, Mohammad Ali

    2012-08-01

    This paper describes the development and utilization of a new nanocomposite consisting of Cu(OH){sub 2} nanoparticles, hydrophobic ionic liquid 1-ethyl-3-methylimidazolium hexafluorophosphate (EMIMPF{sub 6}) and multiwalled carbon nanotubes for glassy carbon electrode modification. The nanocomposite was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) along with energy-dispersive X-ray spectroscopy (EDX). The modified electrode was used for electrochemical characterization of diclofenac. Using differential pulse voltammetry, the prepared sensor showed good sensitivity and selectivity with low overpotential for the determination of diclofenac in the range from 0.18 to 119 {mu}M, with a detection limit of 0.04 {mu}M. Electrochemical studies suggested that the MWCNTs/Cu(OH){sub 2} nanoparticles/IL nanocomposite modified electrode provided a synergistic augmentation on the voltammetric behavior of electrochemical oxidation of diclofenac, which was indicated by the improvement of anodic peak current. Highlights: Black-Right-Pointing-Pointer This work examines oxidation of diclofenac at a nanocomposite modified electrode. Black-Right-Pointing-Pointer The salient feature of this electrode is large diffusion coefficient. Black-Right-Pointing-Pointer The proposed electrode decreased overpotential of diclofenac electrooxidation. Black-Right-Pointing-Pointer The modified electrode has good stability and reproducibility.

  19. An enzymatic glucose biosensor based on a glassy carbon electrode modified with cylinder-shaped titanium dioxide nanorods

    International Nuclear Information System (INIS)

    Yang, Zhanjun; Xu, Youbao; Li, Juan; Jian, Zhiqin; Yu, Suhua; Zhang, Yongcai; Hu, Xiaoya; Dionysiou, Dionysios D.

    2015-01-01

    We describe a highly sensitive electrochemical enzymatic glucose biosensor. A glassy carbon electrode was modified with cylinder-shaped titanium dioxide nanorods (TiO 2 -NRs) for the immobilization of glucose oxidase. The modified nanorods and the enzyme biosensor were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, electrochemical impedance spectroscopy and cyclic voltammetry. The glucose oxidase on the TiO 2 -NRs displays a high activity and undergoes fast surface-controlled electron transfer. A pair of well-defined quasi-reversible redox peaks was observed at −0.394 and −0.450 V. The TiO 2 -NRs provide a good microenvironment to facilitate the direct electron transfer between enzyme and electrode surface. The biosensor has two linear response ranges, viz. from 2.0 to 52 μM, and 0.052 to 2.3 mM. The lower detection limit is 0.5 μM, and the sensitivity is 68.58 mA M −1 cm −2 . The glucose biosensor is selective, well reproducible, and stable. In our perception, the cylindrically shaped TiO 2 -NRs provide a promising support for the immobilization of proteins and pave the way to the development of high-performance biosensors. (author)

  20. Simultaneous determination of hydroquinone and catechol based on glassy carbon electrode modified with gold-graphene nanocomposite

    International Nuclear Information System (INIS)

    Ma, X.; Liu, Z.; Qiu, C.; Chen, T.; Ma, H.

    2013-01-01

    We have synthesized a virtually monodisperse gold-graphene (Au-G) nanocomposite by a single-step chemical reduction method in aqueous dimethylformamide solution. The nanoparticles are homogenously distributed over graphene nanosheets. A glassy carbon electrode was modified with this nanocomposite and displayed high electrocatalytic activity and extraordinary electronic transport properties due to its large surface area. It enabled the simultaneous determination of hydroquinone (HQ) and catechol (CC) in acetate buffer solution of pH 4.5. Two pairs of well-defined, quasi-reversible redox peaks are obtained, one for HQ and its oxidized form, with a 43 mV separation of peak potentials (ΔEp), the other for CC and its oxidized form, with a ΔEp of 39 mV. Due to the large separation of oxidation peak potentials (102 mV), the concentrations of HQ and CC can be easily determined simultaneously. The oxidation peak currents for both HQ and CC increase linearly with the respective concentrations in the 1.0 μM to 0.1 mM concentration range, with the detection limits of 0.2 and 0. 15 μM (S/N = 3), respectively. The modified electrode was successfully applied to the simultaneous determination of HQ and CC in spiked tap water, demonstrating that the Au-G nanocomposite may act as a high-performance sensing material in the selective detection of some environmental pollutants. (author)

  1. Determination of fenitrothion in water using a voltammetric sensor based on a polymer-modified glassy carbon electrode.

    Science.gov (United States)

    Amare, Meareg; Abicho, Samuel; Admassie, Shimelis

    2014-01-01

    A glassy carbon electrode (GCE) modified with poly(4-amino-3-hydroxynaphthalene sulfonic acid) (poly-AHNSA) was used for the selective and sensitive determination of fenitrothion (FT) organophosphorus pesticide in water. The electrochemical behavior of FT at the bare GCE and the poly-AHNSA/GCE were compared using cyclic voltammetry. Enhanced peak current response and shift to a lower potential at the polymer-modified electrode indicated the electrocatalytic activity of the polymer film towards FT. Under optimized solution and method parameters, the adsorptive stripping square wave voltammetric reductive peak current of FT was linear to FT concentration in the range of 0.001 to 6.6 x 10(-6) M, and the LOD obtained (3delta/m) was 7.95 x 10(-10) M. Recoveries in the range 96-98% of spiked FT in tap water and reproducible results with RSD of 2.6% (n = 5) were obtained, indicating the potential applicability of the method for the determination of trace levels of FT in environmental samples.

  2. Electro-oxidation nitrite based on copper calcined layered double hydroxide and gold nanoparticles modified glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Cui Lin; Meng Xiaomeng; Xu Minrong; Shang Kun [College of Chemistry and Material Science, Shandong Agricultural University, Taian 271018, Shandong (China); Ai Shiyun, E-mail: ashy@sdau.edu.cn [College of Chemistry and Material Science, Shandong Agricultural University, Taian 271018, Shandong (China); Liu Yinping [College of Chemistry and Material Science, Shandong Agricultural University, Taian 271018, Shandong (China)

    2011-11-30

    Highlights: > A nitrite sensor fabricated based on copper calcined layered double hydroxides and gold nanoparticles modified electrode. > This sensor exhibited excellent electrocatalytic oxidation to nitrite. > This nitrite sensor exhibited very good analytical performance with low cost, convenient preparation and rapid detection. - Abstract: In this paper, a novel nitrite sensor was constructed based on electrodeposition of gold nanoparticles (AuNPs) on a copper calcined layered double hydroxide (Cu-CLDH) modified glassy carbon electrode. Electrochemical experiments showed that AuNPs/CLDH composite film exhibited excellent electrocatalytic oxidation activity with nitrite due to the synergistic effect of the Cu-CLDH with AuNPs. The fabricated sensor exhibited excellent performance for nitrite detection within a wide concentration interval of 1-191 {mu}M and with a detection limit of 0.5 {mu}M. The superior electrocatalytic response to nitrite was mainly attributed to the large surface area, minimized diffusion resistance, and enhanced electron transfer of the Cu-CLDH and AuNPs composition film. This platform offers a novel route for nitrite sensing with wide analytical applications and will supply the practical applications for a variety of simple, robust, and easy-to-manufacture analytical approaches in the future.

  3. Electro-oxidation nitrite based on copper calcined layered double hydroxide and gold nanoparticles modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Cui Lin; Meng Xiaomeng; Xu Minrong; Shang Kun; Ai Shiyun; Liu Yinping

    2011-01-01

    Highlights: → A nitrite sensor fabricated based on copper calcined layered double hydroxides and gold nanoparticles modified electrode. → This sensor exhibited excellent electrocatalytic oxidation to nitrite. → This nitrite sensor exhibited very good analytical performance with low cost, convenient preparation and rapid detection. - Abstract: In this paper, a novel nitrite sensor was constructed based on electrodeposition of gold nanoparticles (AuNPs) on a copper calcined layered double hydroxide (Cu-CLDH) modified glassy carbon electrode. Electrochemical experiments showed that AuNPs/CLDH composite film exhibited excellent electrocatalytic oxidation activity with nitrite due to the synergistic effect of the Cu-CLDH with AuNPs. The fabricated sensor exhibited excellent performance for nitrite detection within a wide concentration interval of 1-191 μM and with a detection limit of 0.5 μM. The superior electrocatalytic response to nitrite was mainly attributed to the large surface area, minimized diffusion resistance, and enhanced electron transfer of the Cu-CLDH and AuNPs composition film. This platform offers a novel route for nitrite sensing with wide analytical applications and will supply the practical applications for a variety of simple, robust, and easy-to-manufacture analytical approaches in the future.

  4. Highly sensitive hydrogen peroxide sensor based on a glassy carbon electrode modified with platinum nanoparticles on carbon nanofiber heterostructures

    International Nuclear Information System (INIS)

    Yang, Yang; Fu, Renzhong; Yuan, Jianjun; Wu, Shiyuan; Zhang, Jialiang; Wang, Haiying

    2015-01-01

    We are presenting a sensor for hydrogen peroxide (H 2 O 2 ) that is based on the use of a heterostructure composed of Pt nanoparticles (NPs) and carbon nanofibers (CNFs). High-density Pt NPs were homogeneously loaded onto a three-dimensional nanostructured CNF matrix and then deposited in a glassy carbon electrode (GCE). The resulting sensor synergizes the advantages of the conducting CNFs and the nanoparticle catalyst. The porous structure of the CNFs also favor the high-density immobilization of the NPs and the diffusion of water-soluble molecules, and thus assists the rapid catalytic oxidation of H 2 O 2 . If operated at a working voltage of −0.2 V (vs. Ag/AgCl), the modified GCE exhibits a linear response to H 2 O 2 in the 5 μM to 15 mM concentration range (total analytical range: 5 μM to 100 mM), with a detection limit of 1.7 μM (at a signal-to-noise ratio of 3). The modified GCE is not interfered by species such as uric acid and glucose. Its good stability, high selectivity and good reproducibility make this electrode a valuable tool for inexpensive amperometric sensing of H 2 O 2 . (author)

  5. A novel enzymatic glucose sensor based on Pt nanoparticles-decorated hollow carbon spheres-modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Luhana, Charles; Bo Xiangjie; Ju Jian; Guo Liping

    2012-01-01

    A new glucose biosensor was developed based on hollow carbon spheres decorated with platinum nanoparticles (Pt/HCSs)-modified glassy carbon electrode immobilized with glucose oxidase (GOx) with the help of Nafion. The Pt nanoparticles were well dispersed on the HCSs with an average size of 2.29 nm. The detection of glucose was achieved via electrochemical detection of the enzymatically liberated H 2 O 2 at +0.5 V versus Ag/AgCl at physiologic pH of 7.4. The Pt/HCSs-modified electrode exhibited excellent electrocatalytic activities toward both the oxidation and reduction of H 2 O 2 . The glucose biosensor showed good electrocatalytic performance in terms of high sensitivity (4.1 μA mM −1 ), low detection limit (1.8 μM), fast response time m ) and the maximum current density (i max ) values for the biosensor were 10.94 mM and 887 μA cm −2 respectively. Furthermore, this biosensor showed an acceptable reproducibility and high stability. The interfering signals from ascorbic acid and uric acid at concentration levels normally found in human blood were not much compared with the response to glucose. Blood serum samples were also tested with this biosensor and a good recovery was achieved for the two spiked serum samples.

  6. Fabrication of electrochemical theophylline sensor based on manganese oxide nanoparticles/ionic liquid/chitosan nanocomposite modified glassy carbon electrode

    International Nuclear Information System (INIS)

    MansouriMajd, Samira; Teymourian, Hazhir; Salimi, Abdollah; Hallaj, Rahman

    2013-01-01

    In this study, the preparation of a glassy carbon (GC) electrode modified with chitosan/NH 2 -ionic liquid/manganese oxide nanoparticles (Chit/NH 2 -IL/MnO x ) was described for electrocatalytic detection of theophylline (TP). First, chitosan hydrogel (Chit) was electrodeposited on the GC electrode surface at a constant potential (−1.5 V) in acidic solution. Then, the previously synthesized amine-terminated 1-(3-Aminopropyl)-3-methylimidazolium bromide ionic liquid (NH 2 -IL) was covalently attached to the modified electrode via glutaraldehyde (GA) as linking agent. Finally, manganese oxide (MnO x ) nanoparticles were electrodeposited onto the Chit/NH 2 -IL film by potential cycling between −1.0 and 1.7 V in Mn(CH 3 COO) 2 ·4H 2 O neutral aqueous solution. Electrochemical behavior of the modified electrode was evaluated by cyclic voltammetry (CV) technique. The charge transfer coefficient (α) and electron transfer rate constant (k s ) for MnOOH/MnO 2 redox couple were calculated to be 0.35 and 1.62 s −1 , respectively. The resulting system brings new capabilities for electrochemical sensing through combining the advantages of IL and MnO x nanoparticles. The differential pulse voltammetric (DPV) results indicated the high ability of GC/Chit/NH 2 -IL/MnO x modified electrode to catalyze the oxidation of TP. DPV determination of TP in acetate buffer solution (pH 5) gave linear responses over the concentration range up to 120 μM with the detection limit of 50 nM and sensitivity of 804 nA μM −1 . Furthermore, the applicability of the sensor for TP analysis in pharmaceutical samples has been successfully demonstrated

  7. Enhanced oxidation and detection of toxic ractopamine using carbon nanotube film-modified electrode

    International Nuclear Information System (INIS)

    Liu Zhuan; Zhou Yikai; Wang Yanying; Cheng Qin; Wu Kangbing

    2012-01-01

    Highlights: ► The enhanced oxidation of ractopamine on MWCNT film surface was firstly studied. ► The oxidation occurred at phenolic hydroxyl groups and transferred two electrons. ► A sensitive and effective electrochemical sensor was developed for ractopamine. ► It was used to detect ractopamine in animal tissues, the recovery was satisfactory. - Abstract: Insoluble multi-walled carbon nanotube (MWCNT) was readily dispersed into water in the presence of dihexadecyl hydrogen phosphate, and then used to modify the surface of glassy carbon electrode (GCE) by means of solvent evaporation. Scanning electron microscopy test indicated that the GCE surface was coated with uniform MWCNT film. The resulting MWCNT film-modified GCE greatly enhanced the oxidation signal of ractopamine. The oxidation mechanism was studied, and it was found that the oxidation of ractopamine occurred at two phenolic hydroxyl groups, involving two protons and two electrons. Moreover, the influences of pH value, amount of MWCNT, accumulation potential and time were investigated on the oxidation signal of ractopamine. Based on the strong enhancement effect of MWCNT, a sensitive, rapid and simple electrochemical method was developed for the detection of ractopamine. The linear range was from 50 μg L −1 to 2 mg L −1 , and the detection limit was 20 μg L −1 . Finally, this method was successfully used to detect the content of ractopamine in pork and liver samples, and the recovery was in the range from 93.1% to 107.2%.

  8. Sensitive electrochemical sensor of tryptophan based on Ag-C core–shell nanocomposite modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Mao Shuxian; Li Weifeng; Long Yumei; Tu Yifeng; Deng, Anping

    2012-01-01

    Graphical abstract: Ag-C and Colloidal carbon sphere modified glassy carbon electrodes were prepared. It was clear that the Ag-C/GCE exhibited enhanced electrocatalytic activity towards Trp, which could result from the synergistic effect between Ag core and carbon shell. The Ag-C/GCE showed excellent analytical properties in the determination of Trp. Highlights: ► The electrochemical behavior of Ag-C core–shell nanocomposite was firstly proposed. ► Ag-C/GC electrode exhibited favorable electrocatalytic properties towards Trp. ► The good electrocatalysis was due to the synergistic effect of Ag-core and C-shell. ► The Ag-C/GC electrode displayed excellent analytical properties in determining Trp. - Abstract: We here reported a simple electrochemical method for the detection of tryptophan (Trp) based on the Ag-C modified glassy carbon (Ag-C/GC) electrode. The Ag-C core–shell structured nanoparticles were synthesized using one-pot hydrothermal method and characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), and Fourier transform-infrared spectroscopy (FTIR). The electrochemical behaviors of Trp on Ag-C/GC electrode were investigated and exhibited a direct electrochemical process. The favorable electrochemical properties of Ag-C/GC electrode were attributed to the synergistic effect of the Ag core and carbon shell. The carbon shell cannot only protect Ag core but also contribute to the enhanced substrate accessibility and Trp-substrate interactions, while nano-Ag core can display good electrocatalytic activity to Trp at the same time. Under the optimum experimental conditions the oxidation peak current was linearly dependent on the Trp concentration in the range of 1.0 × 10 −7 to 1.0 × 10 −4 M with a detection limit of 4.0 × 10 −8 M (S/N = 3). In addition, the proposed electrode was applied for the determination of Trp concentration in real samples and satisfactory results were obtained. The technique offers

  9. Sensitive electrochemical sensor of tryptophan based on Ag-C core-shell nanocomposite modified glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Mao Shuxian [College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China); Li Weifeng, E-mail: liweifeng@suda.edu.cn [College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China); Long Yumei, E-mail: yumeilong@suda.edu.cn [College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China); Tu Yifeng; Deng, Anping [College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China)

    2012-08-13

    Graphical abstract: Ag-C and Colloidal carbon sphere modified glassy carbon electrodes were prepared. It was clear that the Ag-C/GCE exhibited enhanced electrocatalytic activity towards Trp, which could result from the synergistic effect between Ag core and carbon shell. The Ag-C/GCE showed excellent analytical properties in the determination of Trp. Highlights: Black-Right-Pointing-Pointer The electrochemical behavior of Ag-C core-shell nanocomposite was firstly proposed. Black-Right-Pointing-Pointer Ag-C/GC electrode exhibited favorable electrocatalytic properties towards Trp. Black-Right-Pointing-Pointer The good electrocatalysis was due to the synergistic effect of Ag-core and C-shell. Black-Right-Pointing-Pointer The Ag-C/GC electrode displayed excellent analytical properties in determining Trp. - Abstract: We here reported a simple electrochemical method for the detection of tryptophan (Trp) based on the Ag-C modified glassy carbon (Ag-C/GC) electrode. The Ag-C core-shell structured nanoparticles were synthesized using one-pot hydrothermal method and characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), and Fourier transform-infrared spectroscopy (FTIR). The electrochemical behaviors of Trp on Ag-C/GC electrode were investigated and exhibited a direct electrochemical process. The favorable electrochemical properties of Ag-C/GC electrode were attributed to the synergistic effect of the Ag core and carbon shell. The carbon shell cannot only protect Ag core but also contribute to the enhanced substrate accessibility and Trp-substrate interactions, while nano-Ag core can display good electrocatalytic activity to Trp at the same time. Under the optimum experimental conditions the oxidation peak current was linearly dependent on the Trp concentration in the range of 1.0 Multiplication-Sign 10{sup -7} to 1.0 Multiplication-Sign 10{sup -4} M with a detection limit of 4.0 Multiplication-Sign 10{sup -8} M (S/N = 3). In addition

  10. Characterization of surfactant/hydrotalcite-like clay/glassy carbon modified electrodes: Oxidation of phenol

    International Nuclear Information System (INIS)

    Hernandez, Maria; Fernandez, Lenys; Borras, Carlos; Mostany, Jorge; Carrero, Hermes

    2007-01-01

    The characteristics of hydrotalcite (HT)-like clay films containing ionic and nonionic surfactants and their ability to oxidize phenol have been examined. The HT clay (Co/Al-NO 3 ) was synthesized by coprecipitation techniques and then modified with surfactants such as sodium dodecylbenzenesulfonate (SDBS), octylphenoxypolyethoxyethanol (TX100) or cetylpyridinium bromide (CPB). X-ray diffraction analysis revealed that the interlayer basal spacing varied depending on the type of surfactant retained by the HT. The presence of SDBS and CPB expanded the HT interlayer, which in the presence of TX100 did not show an appreciable change. Phenol oxidation is favored at surfactant-HT-GC modified electrodes, after a preconcentration time, compared to phenol oxidation at HT-GC or GC electrodes. Surfactant-HT-GC modified electrodes display good stability in continuous electrochemical phenol oxidation. At pH values between 6 and 10.8, both SDBS-HT-GC and TX100-HT-GC modified electrodes seem to be promising electrodes for the detection of phenol in water; while the CPB-HT-GC modified electrode should be affected by the inorganic anions

  11. Doxycycline-loaded nanotube-modified adhesives inhibit MMP in a dose-dependent fashion.

    Science.gov (United States)

    Palasuk, Jadesada; Windsor, L Jack; Platt, Jeffrey A; Lvov, Yuri; Geraldeli, Saulo; Bottino, Marco C

    2018-04-01

    This article evaluated the drug loading, release kinetics, and matrix metalloproteinase (MMP) inhibition of doxycycline (DOX) released from DOX-loaded nanotube-modified adhesives. DOX was chosen as the model drug, since it is the only MMP inhibitor approved by the U.S. Food and Drug Administration. Drug loading into the nanotubes was accomplished using DOX solution at distinct concentrations. Increased concentrations of DOX significantly improved the amount of loaded DOX. The modified adhesives were fabricated by incorporating DOX-loaded nanotubes into the adhesive resin of a commercial product. The degree of conversion (DC), Knoop microhardness, DOX release kinetics, antimicrobial, cytocompatibility, and anti-MMP activity of the modified adhesives were investigated. Incorporation of DOX-loaded nanotubes did not compromise DC, Knoop microhardness, or cell compatibility. Higher concentrations of DOX led to an increase in DOX release in a concentration-dependent manner from the modified adhesives. DOX released from the modified adhesives did not inhibit the growth of caries-related bacteria, but more importantly, it did inhibit MMP-1 activity. The loading of DOX into the nanotube-modified adhesives did not compromise the physicochemical properties of the adhesives and the released levels of DOX were able to inhibit MMP activity without cytotoxicity. Doxycycline released from the nanotube-modified adhesives inhibited MMP activity in a concentration-dependent fashion. Therefore, the proposed nanotube-modified adhesive may hold clinical potential as a strategy to preserve resin/dentin bond stability.

  12. A reagentless non-enzymatic hydrogen peroxide sensor presented using electrochemically reduced graphene oxide modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Mutyala, Sankararao; Mathiyarasu, Jayaraman

    2016-01-01

    Herein, we report a simple, facile and reproducible non-enzymatic hydrogen peroxide (H 2 O 2 ) sensor using electrochemically reduced graphene oxide (ERGO) modified glassy carbon electrode (GCE). The modified electrode was characterized by Fourier transform infrared (FT-IR), UV–Visible, scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. Cyclic voltammetric (CV) analysis revealed that ERGO/GCE exhibited virtuous charge transfer properties for a standard redox systems and showed excellent performance towards electroreduction of H 2 O 2 . Amperometric study using ERGO/GCE showed high sensitivity (0.3 μA/μM) and faster response upon the addition of H 2 O 2 at an applied potential of − 0.25 V vs. Ag/AgCl. The detection limit is assessed to be 0.7 μM (S/N = 3) and the time to reach a stable study state current is < 3 s for a linear range of H 2 O 2 concentration (1–16 μM). In addition, the modified electrode exhibited good reproducibility and long-term stability. - Graphical abstract: We presented a reagentless non-enzymatic hydrogen peroxide sensor using electrochemically reduced graphene oxide material. - Highlights: • A facile green procedure proposed for high quality graphene synthesis using electrochemical reduction of graphene oxide • A simple, facile and reagentless non-enzymatic hydrogen peroxide sensor developed using ERGO/GCE. • ERGO/GCE exhibited high sensitivity, selectivity and finite limit of detection for H 2 O 2 sensing at low overpotential. • ERGO/GCE exhibited long term stability and good reproducibility.

  13. A reagentless non-enzymatic hydrogen peroxide sensor presented using electrochemically reduced graphene oxide modified glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Mutyala, Sankararao; Mathiyarasu, Jayaraman, E-mail: al_mathi@yahoo.com

    2016-12-01

    Herein, we report a simple, facile and reproducible non-enzymatic hydrogen peroxide (H{sub 2}O{sub 2}) sensor using electrochemically reduced graphene oxide (ERGO) modified glassy carbon electrode (GCE). The modified electrode was characterized by Fourier transform infrared (FT-IR), UV–Visible, scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. Cyclic voltammetric (CV) analysis revealed that ERGO/GCE exhibited virtuous charge transfer properties for a standard redox systems and showed excellent performance towards electroreduction of H{sub 2}O{sub 2}. Amperometric study using ERGO/GCE showed high sensitivity (0.3 μA/μM) and faster response upon the addition of H{sub 2}O{sub 2} at an applied potential of − 0.25 V vs. Ag/AgCl. The detection limit is assessed to be 0.7 μM (S/N = 3) and the time to reach a stable study state current is < 3 s for a linear range of H{sub 2}O{sub 2} concentration (1–16 μM). In addition, the modified electrode exhibited good reproducibility and long-term stability. - Graphical abstract: We presented a reagentless non-enzymatic hydrogen peroxide sensor using electrochemically reduced graphene oxide material. - Highlights: • A facile green procedure proposed for high quality graphene synthesis using electrochemical reduction of graphene oxide • A simple, facile and reagentless non-enzymatic hydrogen peroxide sensor developed using ERGO/GCE. • ERGO/GCE exhibited high sensitivity, selectivity and finite limit of detection for H{sub 2}O{sub 2} sensing at low overpotential. • ERGO/GCE exhibited long term stability and good reproducibility.

  14. Interfacial electron transfer of glucose oxidase on poly(glutamic acid)-modified glassy carbon electrode and glucose sensing.

    Science.gov (United States)

    Zhou, Xuechou; Tan, Bingcan; Zheng, Xinyu; Kong, Dexian; Li, Qinglu

    2015-11-15

    The interfacial electron transfer of glucose oxidase (GOx) on a poly(glutamic acid)-modified glassy carbon electrode (PGA/GCE) was investigated. The redox peaks measured for GOx and flavin adenine dinucleotide (FAD) are similar, and the anodic peak of GOx does not increase in the presence of glucose in a mediator-free solution. These indicate that the electroactivity of GOx is not the direct electron transfer (DET) between GOx and PGA/GCE and that the observed electroactivity of GOx is ascribed to free FAD that is released from GOx. However, efficient electron transfer occurred if an appropriate mediator was placed in solution, suggesting that GOx is active. The PGA/GCE-based biosensor showed wide linear response in the range of 0.5-5.5 mM with a low detection limit of 0.12 mM and high sensitivity and selectivity for measuring glucose. Copyright © 2015 Elsevier Inc. All rights reserved.

  15. Detection of dopamine in non-treated urine samples using glassy carbon electrodes modified with PAMAM dendrimer-Pt composites

    International Nuclear Information System (INIS)

    Garcia, M.G.; Armendariz, G.M.E.; Godinez, Luis A.; Torres, J.; Sepulveda-Guzman, S.; Bustos, E.

    2011-01-01

    Composites of hydroxyl-terminated PAMAM dendrimers, generation 4.0 (64 peripheral OH groups) containing Pt nanoparticles were synthesized at different reaction times using a microwave reactor. The synthetic procedure resulted in dendrimer encapsulated nanoparticles of Pt (DENs-Pt) of 1.53 ± 0.17 nm diameter that was calculated from transmission electron microscopy, and the Pt nanoparticles had single crystal plane in (1 1 1) orientation determinate by selective area diffraction. Each composite was electrochemically immobilized on a pre-functionalized glassy carbon (GC) electrode that was incorporated as a flow injection amperometric (FIA) detector, for the selective detection and quantification of dopamine (DA) in untreated urine samples. Comparison of the analytical performance of the novel electrochemical detector revealed that the DENs-Pt modified GC electrode with the composite synthesized for 30 min in the microwave reactor, showed the best response for the detection of DA in samples of non-treated urine, being the detection and quantification limits smaller (19 and 9 ppb, respectively) than those corresponding to the naked a GC electrode (846 and 423 ppb, respectively) using the FIA detector. In addition, it was found that this electroanalytical approach suffers minimal matrix effects that arise in the analysis of DA in untreated samples of urine.

  16. Electrochemical Determination of Chlorpyrifos on a Nano-TiO₂Cellulose Acetate Composite Modified Glassy Carbon Electrode.

    Science.gov (United States)

    Kumaravel, Ammasai; Chandrasekaran, Maruthai

    2015-07-15

    A rapid and simple method of determination of chlorpyrifos is important in environmental monitoring and quality control. Electrochemical methods for the determination of pesticides are fast, sensitive, reproducible, and cost-effective. The key factor in electrochemical methods is the choice of suitable electrode materials. The electrode materials should have good stability, reproducibility, more sensitivity, and easy method of preparation. Mercury-based electrodes have been widely used for the determination of chlorpyrifos. From an environmental point of view mercury cannot be used. In this study a biocompatible nano-TiO2/cellulose acetate modified glassy carbon electrode was prepared by a simple method and used for the electrochemical sensing of chlorpyrifos in aqueous methanolic solution. Electroanalytical techniques such as cyclic voltammetry, differential pulse voltammetry, and amperometry were used in this work. This electrode showed very good stability, reproducibility, and sensitivity. A well-defined peak was obtained for the reduction of chlorpyrifos in cyclic voltammetry and differential pulse voltammetry. A smooth noise-free current response was obtained in amperometric analysis. The peak current obtained was proportional to the concentration of chlorpyrifos and was used to determine the unknown concentration of chlorpyrifos in the samples. Analytical parameters such as LOD, LOQ, and linear range were estimated. Analysis of real samples was also carried out. The results were validated through HPLC. This composite electrode can be used as an alternative to mercury electrodes reported in the literature.

  17. A study of the electro-catalytic oxidation of methanol on a cobalt hydroxide modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Jafarian, M.; Mahjani, M.G.; Heli, H.; Gobal, F.; Khajehsharifi, H.; Hamedi, M.H.

    2003-01-01

    Cobalt hydroxide modified glassy carbon electrodes (CHM/GC) prepared by the anodic deposition in presence of tartrate ions have been used for the electro-catalytic oxidation of methanol in alkaline solutions where the methods of cyclic voltammetery (CV), chronoamperometry (CA) and impedance spectroscopy (IS) have been employed. In CV studies, in the presence of methanol the peak current of the oxidation of cobalt hydroxide increase is followed by a decrease in the corresponding cathodic current. This suggests that the oxidation of methanol is being catalysed through the mediated electron transfer across the cobalt hydroxide layer comprising of cobalt ions of various valence states. A mechanism based on the electro-chemical generation of Co(IV) active sites and their subsequent consumptions by methanol have been discussed and the corresponding rate law under the control of charge transfer has been developed and kinetic parameters have been derived. In this context the charge transfer resistance accessible both theoretically and through the IS studies have been used as a criteria. Under the CA regimes the reaction followed a Cottrellian behaviour

  18. Detection of dopamine in non-treated urine samples using glassy carbon electrodes modified with PAMAM dendrimer-Pt composites

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, M.G. [Laboratory of Bioelectrochemistry, Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, S. C., Parque Tecnologico, Queretaro, Sanfandila, Pedro Escobedo 76703, Queretaro (Mexico); Department of Chemistry, Universidad de Guanajuato, Cerro de la Venada S/N Col. Pueblito de Rocha, 36040 Guanajuato, Gto (Mexico); Armendariz, G.M.E.; Godinez, Luis A.; Torres, J. [Laboratory of Bioelectrochemistry, Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, S. C., Parque Tecnologico, Queretaro, Sanfandila, Pedro Escobedo 76703, Queretaro (Mexico); Sepulveda-Guzman, S. [Centro de Innovacion, Investigacion y Desarrollo en Ingenieria y Tecnologia, Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, Av. Universidad, San Nicolas de los Garza, Nuevo Leon, 66451 Nuevo Leon (Mexico); Bustos, E., E-mail: ebustos@cideteq.mx [Laboratory of Bioelectrochemistry, Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, S. C., Parque Tecnologico, Queretaro, Sanfandila, Pedro Escobedo 76703, Queretaro (Mexico)

    2011-09-01

    Composites of hydroxyl-terminated PAMAM dendrimers, generation 4.0 (64 peripheral OH groups) containing Pt nanoparticles were synthesized at different reaction times using a microwave reactor. The synthetic procedure resulted in dendrimer encapsulated nanoparticles of Pt (DENs-Pt) of 1.53 {+-} 0.17 nm diameter that was calculated from transmission electron microscopy, and the Pt nanoparticles had single crystal plane in (1 1 1) orientation determinate by selective area diffraction. Each composite was electrochemically immobilized on a pre-functionalized glassy carbon (GC) electrode that was incorporated as a flow injection amperometric (FIA) detector, for the selective detection and quantification of dopamine (DA) in untreated urine samples. Comparison of the analytical performance of the novel electrochemical detector revealed that the DENs-Pt modified GC electrode with the composite synthesized for 30 min in the microwave reactor, showed the best response for the detection of DA in samples of non-treated urine, being the detection and quantification limits smaller (19 and 9 ppb, respectively) than those corresponding to the naked a GC electrode (846 and 423 ppb, respectively) using the FIA detector. In addition, it was found that this electroanalytical approach suffers minimal matrix effects that arise in the analysis of DA in untreated samples of urine.

  19. Fabrication of folic acid sensor based on the Cu doped SnO2 nanoparticles modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Lavanya, N; Radhakrishnan, S; Sudhan, N; Sekar, C; Leonardi, S G; Neri, G; Cannilla, C

    2014-01-01

    A novel folic acid biosensor has been fabricated using Cu doped SnO 2 nanoparticles (NPs) synthesized by a simple microwave irradiation method. Powder XRD and TEM studies confirmed that both the pure and Cu doped SnO 2 (Cu: 0, 10, 20wt%) crystallized in tetragonal rutile-type structure with spherical morphology. The average crystallite size of pure SnO 2 was estimated to be around 16 nm. Upon doping, the crystallite sizes decreased to 9 nm and 5 nm for 10 and 20wt% Cu doped SnO 2 respectively. XPS studies confirmed the electronic state of Sn and Cu to be 4+ and 2+ respectively. Cu (20wt%) doped SnO 2 NPs are proved to be a good sensing element for the determination of folic acid (FA). Cu-SnO 2 NPs (20wt%) modified glassy carbon electrode (GCE) exhibited the lowest detection limit of 0.024 nM over a wide folic acid concentration range of 1.0 × 10 −10 to 6.7 × 10 −5 M at physiological pH of 7.0. The fabricated sensor is highly selective towards the determination of FA even in the presence of a 100 fold excess of common interferent ascorbic acid. The sensor proved to be useful for the estimation of FA content in pharmaceutical sample with satisfactory recovery. (paper)

  20. Electrochemical Detection of Ultratrace (Picomolar) Levels of Hg2+ Using a Silver Nanoparticle-Modified Glassy Carbon Electrode.

    Science.gov (United States)

    Suherman, Alex L; Ngamchuea, Kamonwad; Tanner, Eden E L; Sokolov, Stanislav V; Holter, Jennifer; Young, Neil P; Compton, Richard G

    2017-07-05

    Ultratrace levels of Hg 2+ have been quantified by undertaking linear sweep voltammetry with a silver nanoparticle-modified glassy carbon electrode (AgNP-GCE) in aqueous solutions containing Hg 2+ . This is achieved by monitoring the change in the silver stripping peak with Hg 2+ concentration resulting from the galvanic displacement of silver by mercury: Ag(np) + 1/2Hg 2+ (aq) → Ag + (aq) + 1/2Hg(l). This facile and reproducible detection method exhibits an excellent linear dynamic range of 100.0 pM to 10.0 nM Hg 2+ concentration with R 2 = 0.982. The limit of detection (LoD) based on 3σ is 28 pM Hg 2+ , while the lowest detectable level for quantification purposes is 100.0 pM. This method is appropriate for routine environmental monitoring and drinking water quality assessment since the guideline value set by the US Environmental Protection Agency (EPA) for inorganic mercury in drinking water is 0.002 mg L -1 (10 nM).

  1. Electrochemical determination of 4-nitrophenol at polycarbazole/N-doped graphene modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Zhang, Yuehua; Wu, Lihua; Lei, Wu; Xia, Xifeng; Xia, Mingzhu; Hao, Qingli

    2014-01-01

    Graphical abstract: - Highlights: • Polycarbazole/N-doping graphene (PCZ/N-GE) composite was fabricated. • The PCZ/N-GE composite shows good electrocatalytic activity to 4-nitrophenol. • PCZ/N-GE modified electrode was used for determination of 4-nitrophenol. • The proposed sensor exhibits good sensitivity, stability and reproducibility. - Abstract: Polycarbazole (PCZ)/nitrogen-doped graphene (N-GE) composite was prepared by electropolymerization of carbazole on the N-GE modified glass carbon electrode (N-GE/GCE) for fabricating a novel electrochemical sensor for 4-nitrophenol (4-NP). The PCZ/N-GE shows high conductivity and well-distributed nanostructure. The redox behavior of 4-NP at a PCZ/N-GE/GCE was investigated in acetate buffer solution by cyclic voltammetry (CV), compared with the bare GCE, reduced graphene oxide (RGO), N-GE and PCZ modified GCEs. The results indicate that all modified electrodes show the enhanced reduction peak currents. However, the PCZ/N-GE/GCE exhibits the highest peak current and most positive reduction potential of 4-NP, which reflects the PCZ/N-GE composite has the best electrocatalytic activity towards 4-NP. The enhanced electrochemical performance of PCZ/N-GE and the electrocatalytic activity to 4-NP are contributed to the synergic effect of PCZ and N-GE with highly conductivity and large surface area, which can greatly facilitate the electron-transfer processes between the electrolyte and electrode. An electrochemical sensor for 4-NP was developed based on the PCZ/N-GE modified electrode under the optimized conditions. The reduction peak current was linear with the concentration of 4-NP in the range of 8 × 10 -7 ∼2 × 10 -5 M. The low detection limit of the sensor was estimated to be 0.062 μM (S/N = 3). The sensor based on PCZ/N-GE/GCE was also applied to the detection of 4-NP in real water samples

  2. A novel enzymatic glucose sensor based on Pt nanoparticles-decorated hollow carbon spheres-modified glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Luhana, Charles; Bo Xiangjie; Ju Jian; Guo Liping, E-mail: guolp078@nenu.edu.cn [Northeast Normal University, Faculty of Chemistry (China)

    2012-10-15

    A new glucose biosensor was developed based on hollow carbon spheres decorated with platinum nanoparticles (Pt/HCSs)-modified glassy carbon electrode immobilized with glucose oxidase (GOx) with the help of Nafion. The Pt nanoparticles were well dispersed on the HCSs with an average size of 2.29 nm. The detection of glucose was achieved via electrochemical detection of the enzymatically liberated H{sub 2}O{sub 2} at +0.5 V versus Ag/AgCl at physiologic pH of 7.4. The Pt/HCSs-modified electrode exhibited excellent electrocatalytic activities toward both the oxidation and reduction of H{sub 2}O{sub 2}. The glucose biosensor showed good electrocatalytic performance in terms of high sensitivity (4.1 {mu}A mM{sup -1}), low detection limit (1.8 {mu}M), fast response time <3 s, and wide linear range (0.04-8.62 mM). The apparent Michaelis-Menten constant (K{sub m}) and the maximum current density (i{sub max}) values for the biosensor were 10.94 mM and 887 {mu}A cm{sup -2} respectively. Furthermore, this biosensor showed an acceptable reproducibility and high stability. The interfering signals from ascorbic acid and uric acid at concentration levels normally found in human blood were not much compared with the response to glucose. Blood serum samples were also tested with this biosensor and a good recovery was achieved for the two spiked serum samples.

  3. Poly(alizarin red)/Graphene modified glassy carbon electrode for simultaneous determination of purine and pyrimidine

    Energy Technology Data Exchange (ETDEWEB)

    Ba Xi; Luo Liqiang [Department of Chemistry, Shanghai University, Shanghai 200444 (China); Ding Yaping, E-mail: wdingyp@sina.com [Department of Chemistry, Shanghai University, Shanghai 200444 (China); Zhang Zhen [Department of Chemistry, Shanghai University, Shanghai 200444 (China); Chu Yuliang [Instrumental Analysis and Research Center, Shanghai University, Shanghai 200444 (China); Wang Bijun; Ouyang Xiaoqian [Department of Chemistry, Shanghai University, Shanghai 200444 (China)

    2012-11-08

    Graphical abstract: DPVs of PAR/Graphene/GCE (a) and the bare GCE (c) in 0.1 M PBS containing 50.0 {mu}M G, 50.0 {mu}M A, 100.0 {mu}M T and 100.0 {mu}M C, (b) PAR/Graphene/GCE in 0.1 M PBS. Highlights: Black-Right-Pointing-Pointer The sensor exhibited well-separated peaks and low detection limit. Black-Right-Pointing-Pointer The sensor possesses high sensitivity and wide linear range. Black-Right-Pointing-Pointer The sensor was used for simultaneous detection of G, A, T and C successfully. Black-Right-Pointing-Pointer The sensor was applied in a fish sperm DNA sample with satisfactory results. Black-Right-Pointing-Pointer The proposed sensor has good stability and reproducibility. - Abstract: In this work, a poly(alizarin red)/Graphene composite film modified glassy carbon electrode (PAR/Graphene/GCE) was prepared for simultaneous determination of four DNA bases (guanine, adenine, thymine and cytosine) without any pretreatment. The morphology and interface property of PAR/Graphene films were examined by scanning electron microscopy and electrochemical impedance spectroscopy. The PAR/Graphene/GCE exhibited excellent electrocatalytic activity toward purine (guanine and adenine) and pyrimidine (thymine and cytosine) in 0.1 M phosphate buffer solution (pH 7.4). Under optimum conditions, differential pulse voltammetry was used to detect the oxidation of purine and pyrimidine. The results showed that PAR/Graphene/GCE exhibited well-separated peaks, low detection limit, high sensitivity and wide linear range for simultaneous detection of purine and pyrimidine. The proposed sensor also has good stability and reproducibility. Furthermore, the modified electrode was applied for the detection of DNA bases in a fish sperm DNA sample with satisfactory results.

  4. Poly(alizarin red)/Graphene modified glassy carbon electrode for simultaneous determination of purine and pyrimidine

    International Nuclear Information System (INIS)

    Ba Xi; Luo Liqiang; Ding Yaping; Zhang Zhen; Chu Yuliang; Wang Bijun; Ouyang Xiaoqian

    2012-01-01

    Graphical abstract: DPVs of PAR/Graphene/GCE (a) and the bare GCE (c) in 0.1 M PBS containing 50.0 μM G, 50.0 μM A, 100.0 μM T and 100.0 μM C, (b) PAR/Graphene/GCE in 0.1 M PBS. Highlights: ► The sensor exhibited well-separated peaks and low detection limit. ► The sensor possesses high sensitivity and wide linear range. ► The sensor was used for simultaneous detection of G, A, T and C successfully. ► The sensor was applied in a fish sperm DNA sample with satisfactory results. ► The proposed sensor has good stability and reproducibility. - Abstract: In this work, a poly(alizarin red)/Graphene composite film modified glassy carbon electrode (PAR/Graphene/GCE) was prepared for simultaneous determination of four DNA bases (guanine, adenine, thymine and cytosine) without any pretreatment. The morphology and interface property of PAR/Graphene films were examined by scanning electron microscopy and electrochemical impedance spectroscopy. The PAR/Graphene/GCE exhibited excellent electrocatalytic activity toward purine (guanine and adenine) and pyrimidine (thymine and cytosine) in 0.1 M phosphate buffer solution (pH 7.4). Under optimum conditions, differential pulse voltammetry was used to detect the oxidation of purine and pyrimidine. The results showed that PAR/Graphene/GCE exhibited well-separated peaks, low detection limit, high sensitivity and wide linear range for simultaneous detection of purine and pyrimidine. The proposed sensor also has good stability and reproducibility. Furthermore, the modified electrode was applied for the detection of DNA bases in a fish sperm DNA sample with satisfactory results.

  5. Nanomolar determination of 4-nitrophenol based on a poly(methylene blue)-modified glassy carbon electrode.

    Science.gov (United States)

    Giribabu, Krishnamoorthy; Suresh, Ranganathan; Manigandan, Ramadoss; Munusamy, Settu; Kumar, Sivakumar Praveen; Muthamizh, Selvamani; Narayanan, Vengidusamy

    2013-10-07

    A poly(methylene blue)-modified glassy carbon electrode (PMB/GCE) was fabricated by electropolymerisation of methylene blue on a GCE and further utilized to investigate the electrochemical determination of 4-nitrophenol (4-NP) by cyclic voltammetry (CV), differential pulse voltammetry and chronocoulometry. The morphology of the PMB on GCE was examined using a scanning electron microscope (SEM). An oxidation peak of 4-NP at the PMB modified electrode was observed at 0.28 V, and in the case of bare GCE, no oxidation peak was observed, which indicates that PMB/GCE exhibits a remarkable effect on the electrochemical determination of 4-NP. Due to this remarkable effect of PMB/GCE, a sensitive and simple electrochemical method was proposed for the determination of 4-NP. The effect of the scan rate and pH was investigated to determine the optimum conditions at which the PMB/GCE exhibits a higher sensitivity with a lower detection limit. Moreover, kinetic parameters such as the electron transfer number, proton transfer number and standard heterogeneous rate constant were calculated. Under optimum conditions, the oxidation current of 4-NP is proportional to its concentration in the range of 15-250 nM with a correlation coefficient of 0.9963. The detection limit was found to be 90 nM (S/N = 3). The proposed method based on PMB/GCE is simple, easy and cost effective. To further confirm its possible application, the proposed method was successfully used for the determination of 4-NP in real water samples with recoveries ranging from 97% to 101.6%. The interference due to sodium, potassium, calcium, magnesium, copper, zinc, iron, sulphate, carbonate, chloride, nitrate and phosphate was found to be almost negligible.

  6. Simultaneous Electrochemical Detection of Dopamine and Ascorbic Acid Using an Iron Oxide/Reduced Graphene Oxide Modified Glassy Carbon Electrode

    Directory of Open Access Journals (Sweden)

    Teo Peik-See

    2014-08-01

    Full Text Available The fabrication of an electrochemical sensor based on an iron oxide/graphene modified glassy carbon electrode (Fe3O4/rGO/GCE and its simultaneous detection of dopamine (DA and ascorbic acid (AA is described here. The Fe3O4/rGO nanocomposite was synthesized via a simple, one step in-situ wet chemical method and characterized by different techniques. The presence of Fe3O4 nanoparticles on the surface of rGO sheets was confirmed by FESEM and TEM images. The electrochemical behavior of Fe3O4/rGO/GCE towards electrocatalytic oxidation of DA was investigated by cyclic voltammetry (CV and differential pulse voltammetry (DPV analysis. The electrochemical studies revealed that the Fe3O4/rGO/GCE dramatically increased the current response against the DA, due to the synergistic effect emerged between Fe3O4 and rGO. This implies that Fe3O4/rGO/GCE could exhibit excellent electrocatalytic activity and remarkable electron transfer kinetics towards the oxidation of DA. Moreover, the modified sensor electrode portrayed sensitivity and selectivity for simultaneous determination of AA and DA. The observed DPVs response linearly depends on AA and DA concentration in the range of 1–9 mM and 0.5–100 µM, with correlation coefficients of 0.995 and 0.996, respectively. The detection limit of (S/N = 3 was found to be 0.42 and 0.12 µM for AA and DA, respectively.

  7. Analysis of total polyphenols in wines by FIA with highly stable amperometric detection using carbon nanotube-modified electrodes.

    Science.gov (United States)

    Arribas, Alberto Sánchez; Martínez-Fernández, Marta; Moreno, Mónica; Bermejo, Esperanza; Zapardiel, Antonio; Chicharro, Manuel

    2013-02-15

    The use of glassy carbon electrodes (GCEs) modified with multi-walled carbon nanotube (CNT) films for the continuous monitoring of polyphenols in flow systems has been examined. The performance of these modified electrodes was evaluated and compared to bare GCE by cyclic voltammetry experiments and by flow injection analysis (FIA) with amperometric detection monitoring the response of gallic, caffeic, ferulic and p-coumaric acids in 0.050 M acetate buffer pH 4.5 containing 100 mM NaCl. The GCE modified with CNT dispersions in polyethyleneimine (PEI) provided lower overpotentials, higher sensitivity and much higher signal stability under a dynamic regime than bare GCEs. These properties allowed the estimation of the total polyphenol content in red and white wines with a remarkable long-term stability in the measurements despite the presence of potential fouling substances in the wine matrix. In addition, the versatility of the electrochemical methodology allowed the selective estimation of the easily oxidisable polyphenol fraction as well as the total polyphenol content just by tuning the detection potential at +0.30 or 0.70 V, respectively. The significance of the electrochemical results was demonstrated through correlation studies with the results obtained with conventional spectrophotometric assays for polyphenols (Folin-Ciocalteu, absorbance at 280 nm index and colour intensity index). Copyright © 2012 Elsevier Ltd. All rights reserved.

  8. Facile preparation of molecularly imprinted polypyrrole-graphene-multiwalled carbon nanotubes composite film modified electrode for rutin sensing.

    Science.gov (United States)

    Yang, Lite; Yang, Juan; Xu, Bingjie; Zhao, Faqiong; Zeng, Baizhao

    2016-12-01

    In this paper, a novel molecularly imprinted composite film modified electrode was presented for rutin (RT) detection. The modified electrode was fabricated by electropolymerization of pyrrole on a graphene-multiwalled carbon nanotubes composite (G-MWCNTs) coated glassy carbon electrode in the presence of RT. The netlike G-MWCNTs composite, prepared by in situ hydrothermal process, had high conductivity and electrocatalytic activity. At the resulting MIP/G-MWCNTs/GCE electrode RT could produce a sensitive anodic peak in pH 1.87 Britton-Robinson buffer solution. The factors affecting the electrochemical behavior and response of RT on the modified electrode were carefully investigated and optimized. Under the selected conditions, the linear response range of RT was 0.01-1.0μmolL -1 and the detection limit (S/N=3) was 5.0nmolL -1 . The electrode was successfully applied to the determination of RT in buckwheat tea and orange juice samples, and the recoveries for standards added were 93.4-105%. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Electrochemical Study of Modified Glassy Carbon Electrode with Carboxyphenyl Diazonium Salt in Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Mariem BOUROUROU

    2014-05-01

    Full Text Available The covalent grafting of carboxyphenyl functionalities to planar carbon substrates by reaction with 2-carboxybenezenediazonium salt has been studied in aqueous acid solution. The surface was characterized, before and after the functionnalization process, by cyclic voltammetry, electrochemical impedance spectroscopy and linear sweep voltammetry (LSV in order to control and to prove the formation of a coating on the carbon surface. The results indicate the presence of substituted phenyl groups on the investigated surface. Electrochemical impedance measurements show that the slowing down of the electron transfer kinetics was more evident by increasing the number of cycles resulting to higher DEp and RCT parameters. Besides, the effect of the pH on the electron transfer processes of the Fe(CN63-/4- at the modified electrode is studied. By changing the solution pH the terminal group’s charge state would vary, based on which the surface pKa value is estimated.

  10. Electrodes from carbon nanotubes/NiO nanocomposites synthesized in modified Watts bath for supercapacitors

    Science.gov (United States)

    Hakamada, Masataka; Abe, Tatsuhiko; Mabuchi, Mamoru

    2016-09-01

    A modified Watts bath coupled with pulsed current electroplating is used to uniformly deposit ultrafine nickel oxide particles (diameter < 4 nm) on multiwalled carbon nanotubes. The capacitance of the multiwalled carbon nanotubes/nickel oxide electrodes was as high as 2480 F g-1 (per mass of nickel oxide), which is close to the theoretical capacitance of NiO.

  11. A uric acid sensor based on electrodeposition of nickel hexacyanoferrate nanoparticles on an electrode modified with multi-walled carbon nanotubes

    International Nuclear Information System (INIS)

    Fang, B.; Feng, Y.; Wang, G.; Zhang, C.; Gu, A.; Liu, M.

    2011-01-01

    An electrode sensitive to uric acid was prepared by electrodeposition of nickel(II) hexacyanoferrate(III) on the surface of a glassy carbon electrode modified with multi-walled carbon nanotubes. The morphology of the material was characterized by scanning electron microscopy and Fourier transform infrared spectrometry. The modified electrode were characterized via cyclic voltammetry and amperometry (i - t). It exhibited efficient electron transfer ability and a strong and fast (< 3 s) response towards uric acid which is linear in the range from 0.1 μM to 18 μM, with a lower detection limit of 50 nM (at an S/N ratio of 3). In addition, the electrode exhibited good reproducibility and long-term stability. (author)

  12. Flow injection analysis of sulphide based on its photoelectrocatalytic oxidation at poly-methylene blue modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Dilgin, Yusuf; Canarslan, Seda; Ayyildiz, Onder; Ertek, Bensu; Nişli, Gürel

    2012-01-01

    A new approach for photoelectrocatalytic determination of sulphide in a flow injection analysis (FIA) system was studied using a poly-methylene blue modified glassy carbon electrode (poly-MB/GCE). Results from electrochemical measurements have revealed that poly-MB/GCE is capable of signalling electrocatalytic and photoelectrocatalytic activity towards sulphide oxidation. When the surface of poly-MB/GCE was irradiated with a light source (250 W Halogen lamp), the electrocatalytic current increased substantially. A homemade flow electrochemical cell with a suitable transparent window for the irradiation of the electrode surface was used to perform the photoelectrocatalytic determination of sulphide in FIA system. The currents obtained from the photoamperometric measurements in the FIA system at optimum conditions (carrier solution: pH 9.0 Britton Robinson buffer solution containing 0.1 M KCl; flow rate: 1.3 mL min −1 ; transmission tubing length: 10 cm; injection volume: 100 μL; and constant applied potential: +150 mV vs. Ag/AgCl/KCl sat ) were linearly correlated with the sulphide concentration. The calibration curves were obtained for sulphide concentrations in a range of 0.5–500 μM. The detection limits were found to be 0.27 and 0.15 μM for amperometric and photoamperometric methods, respectively. The proposed method was successfully applied to different wastewaters such as municipal sewage or tannery wastewater. Finally, results from the sulphide measurements by poly-MB/GCE were in good agreement with those attained using spectrophotometric method.

  13. Mechanical, Rheological and Thermal Properties of Polystyrene/1-Octadecanol Modified Carbon Nanotubes Nanocomposites

    KAUST Repository

    Amr, Issam Thaher; Al-Amer, Adnan; Thomas, Selvin P.; Sougrat, Rachid; Atieh, Muataz Ali

    2014-01-01

    The results of the studies on the functionalization of multi-walled carbon nanotubes (MWCNT) with 1-octadecanol and its usage as reinforcing filler in the bulk polymerization of styrene are reported in this article. Both unmodified and modified CNTs

  14. Microstructure and mechanical performance of modified mortar using hemp fibres and carbon nanotubes

    KAUST Repository

    Hamzaoui, Rabah; Guessasma, Sofiane; Mecheri, Boubakeur; Eshtiaghi, Amir M.; Bennabi, Abdelkrim

    2014-01-01

    Mechanical performance of modified mortar using hemp fibres is studied following various processing conditions. Hemp fibres combined with carbon nanotubes (CNT) are introduced in mortar and their effect is studied as function of curing time

  15. Synthesis and Characterization of Ferrocene Derivatives and Preliminarily Electrocatalytic Oxidation of L-Cysteine at Nafion-Ferrocene Derivatives Modified Glassy Carbon Electrode

    Directory of Open Access Journals (Sweden)

    Jianping Yong

    2014-01-01

    Full Text Available Five new structural ferrocene derivatives (2a~2e were firstly synthesized and characterized by 1H NMR, 13C NMR, ESI-MS, and XRD. Subsequently, the preliminarily electrocatalytic oxidation of L-cysteine (L-Cys at nafion-ferrocene derivatives modified glassy carbon electrode (GCE has also been investigated by cyclic voltammetry. The results showed that 2e can dramatically electrocatalyze the oxidation of L-cysteine at its modified GCE in 0.1 mol L−1 NaNO3 aqueous solution with a quasireversible process with ΔEp≈55 mV.

  16. An amperometric penicillin biosensor with enhanced sensitivity based on co-immobilization of carbon nanotubes, hematein, and {beta}-lactamase on glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Chen Bi; Ma Ming [Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research (Ministry of Education of China), College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha 410081 (China); Su Xiaoli, E-mail: xsu@hunnu.edu.cn [Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research (Ministry of Education of China), College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha 410081 (China)

    2010-07-26

    An amperometric penicillin biosensor with enhanced sensitivity was successfully developed by co-immobilization of multi-walled carbon nanotubes (MWCNTs), hematein, and {beta}-lactamase on glassy carbon electrode using a layer-by-layer assembly technique. Under catalysis of the immobilized enzyme, penicillin was hydrolyzed, decreasing the local pH. The pH change was monitored amperometrically with hematein as a pH-sensitive redox probe. MWCNTs were used as an electron transfer enhancer as well as an efficient immobilization matrix for the sensitivity enhancement. The effects of immobilization procedure, working potential, enzyme quantity, buffer concentration, and sample matrix were investigated. The biosensor offered a minimum detection limit of 50 nM (19 {mu}g L{sup -1}) for penicillin V, lower than those of the conventional pH change-based biosensors by more than two orders of magnitude. The electrode-to-electrode variation of the response sensitivity was 7.0% RSD.

  17. Voltammetric determination of polyphenolic content in pomegranate juice using a poly(gallic acid/multiwalled carbon nanotube modified electrode

    Directory of Open Access Journals (Sweden)

    Refat Abdel-Hamid

    2016-07-01

    Full Text Available A simple and sensitive poly(gallic acid/multiwalled carbon nanotube modified glassy carbon electrode (PGA/MWCNT/GCE electrochemical sensor was prepared for direct determination of the total phenolic content (TPC as gallic acid equivalent. The GCE working electrode was electrochemically modified and characterized using scanning electron microscope (SEM, cyclic voltammetry (CV, chronoamperometry and chronocoulometry. It was found that gallic acid (GA exhibits a superior electrochemical response on the PGA/MWCNT/GCE sensor in comparison with bare GCE. The results reveal that a PGA/MWCNT/GCE sensor can remarkably enhance the electro-oxidation signal of GA as well as shift the peak potentials towards less positive potential values. The dependence of peak current on accumulation potential, accumulation time and pH were investigated by square-wave voltammetry (SWV to optimize the experimental conditions for the determination of GA. Using the optimized conditions, the sensor responded linearly to a GA concentration throughout the range of 4.97 × 10−6 to 3.38 × 10−5 M with a detection limit of 3.22 × 10−6 M (S/N = 3. The fabricated sensor shows good selectivity, stability, repeatability and (101% recovery. The sensor was successfully utilized for the determination of total phenolic content in fresh pomegranate juice without interference of ascorbic acid, fructose, potassium nitrate and barbituric acid. The obtained data were compared with the standard Folin–Ciocalteu spectrophotometric results.

  18. A hydroxylamine electrochemical sensor based on electrodeposition of porous ZnO nanofilms onto carbon nanotubes films modified electrode

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Cuihong; Wang Guangfeng; Liu Min; Feng Yuehua; Zhang Zhidan [College of Chemistry and Materials Science, Anhui Key Laboratory of Chem-Biosensing, Beijing East Road No. 1, Anhui Normal University, Anhui, Wuhu 241000 (China); Fang Bin, E-mail: binfang_47@yahoo.com.c [College of Chemistry and Materials Science, Anhui Key Laboratory of Chem-Biosensing, Beijing East Road No. 1, Anhui Normal University, Anhui, Wuhu 241000 (China)

    2010-03-01

    A novel route (electrodeposition) for the fabrication of porous ZnO nanofilms attached multi-walled carbon nanotubes (MWCNTs) modified glassy carbon electrodes (GCEs) was proposed. The morphological characterization of ZnO/MWCNT films was examined by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). The performances of the ZnO/MWCNTs/GCE were characterized with cyclic voltammetry (CV), Nyquist plot (EIS) and typical amperometric response (i-t). The potential utility of electrodes constructed was demonstrated by applying them to the analytical determination of hydroxylamine concentration. An optimized limit of detection of 0.12 muM was obtained at a signal-to-noise ratio of 3 and with a fast response time (within 3 s). Additionally, the ZnO/MWCNTs/GCE exhibited a wide linear range from 0.4 to 1.9 x 10{sup 4} muM and higher sensitivity. The ease of fabrication, high stability, and low cost of the modified electrode are the promising features of the proposed sensor.

  19. Amperometric bienzyme glucose biosensor based on carbon nanotube modified electrode with electropolymerized poly(toluidine blue O) film

    International Nuclear Information System (INIS)

    Wang Wenju; Wang Fang; Yao Yanli; Hu Shengshui; Shiu, Kwok-Keung

    2010-01-01

    The amperometric bienzyme glucose biosensor utilizing horseradish peroxidase (HRP) and glucose oxidase (GOx) immobilized in poly(toluidine blue O) (PTBO) film was constructed on multi-walled carbon nanotube (MWNT) modified glassy carbon electrode. The HRP layer could be used to analyze hydrogen peroxide with toluidine blue O (TBO) mediators, while the bienzyme system (HRP + GOx) could be utilized for glucose determination. Glucose underwent biocatalytic oxidation by GOx in the presence of oxygen to yield H 2 O 2 which was further reduced by HRP at the MWNT-modified electrode with TBO mediators. In the absence of oxygen, glucose oxidation proceeded with electron transfer between GOx and the electrode mediated by TBO moieties without H 2 O 2 production. The bienzyme electrode offered high sensitivity for amperometric determination of glucose at low potential, displaying Michaelis-Menten kinetics. The bienzyme glucose biosensor displayed linear response from 0.1 to 1.2 mM with a sensitivity of 113 mA M -1 cm -2 at an applied potential of -0.10 V in air-saturated electrolytes.

  20. Voltammetric determination of In3+ based on the bifunctionality of a multi-walled carbon nanotubes-nafion modified electrode.

    Science.gov (United States)

    Li, Junhua; Zhang, Fuxing; Wang, Jianqiu; Xu, Zhifeng; Zeng, Rongying

    2009-05-01

    Due to the strong cation-exchange ability of Nafion and the excellent properties of multi-walled carbon nanotubes (MWCNTs), a highly sensitive and mercury-free method of determining trace levels of In(3+) has been established based on the bifunctionality of a MWCNTs/Nafion modified glassy carbon electrode (GCE). The MWCNTs/Nafion modified GCE detects In(3+) in a 0.01 M HAc-NaAc buffer solution at pH 5.0 using anodic stripping voltammetry (ASV). The experimental results suggest that a sensitive anodic stripping peak appears at -0.58 V on anodic stripping voltammograms, which can be used as an analytical signal for the determination of In(3+). A good linear relationship between the stripping peak currents and the In(3+) concentration is obtained, covering the concentration range from 5.0 x 10(-10) to 2.0 x 10(-7) M, with a correlation coefficient of 0.999; the detection limit is 1.0 x 10(-11) M. This proposed method has been applied to detect In(3+) as a new way.

  1. GC electrode modified with carbon nanotubes and NiO for the simultaneous determination of bisphenol A, hydroquinone and catechol

    International Nuclear Information System (INIS)

    Goulart, Lorena Athie; Mascaro, Lucia Helena

    2016-01-01

    This work reports the electrochemical determination of bisphenol A (BPA), hydroquinone (HQ) and catechol (CC) using glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes (MWCNT) and nickel oxide nanoparticles (NiO). MWCNT were functionalized with sulfonitric solution (3H 2 SO 4 :1HNO 3 ) and dispersed in dimethylformamide for the MWCNT/GCE manufacturing. The MWCNT/GCE was modified with NiO using cyclic potential in pH 4 maintained by an acetate buffer solution containing 0.008 mol L −1 of nickel nitrate. The concentration of the nickel solution and the number of cycles in the electrodeposition were studied. Morphological characterization of NiO/MWCNT/GCE was carried out by scanning electron microscopy and the presence of NiO was observed. The electrochemical behavior was evaluated by cyclic voltammetry and electrochemical impedance spectroscopy using BPA solution and the results were compared with those of GCE. The NiO/MWCNT/GCE presented the lowest charge transfer resistance. The electrochemical detection of BPA, HQ and CC was developed using differential pulse voltammetry. The analytical curves showed an excellent linear response and the detection limits for the simultaneous determination of BPA, HQ and CC were 2.8 × 10 −8 mol L −1 , 2.70 × 10 −8 mol L −1 and 5.9 × 10 −8 mol L −1 , respectively.

  2. Hall Measurements on Carbon Nanotube Paper Modified With Electroless Deposited Platinum

    Directory of Open Access Journals (Sweden)

    Iwuoha Emmanuel

    2009-01-01

    Full Text Available Abstract Carbon nanotube paper, sometimes referred to as bucky paper, is a random arrangement of carbon nanotubes meshed into a single robust structure, which can be manipulated with relative ease. Multi-walled carbon nanotubes were used to make the nanotube paper, and were subsequently modified with platinum using an electroless deposition method based on substrate enhanced electroless deposition. This involves the use of a sacrificial metal substrate that undergoes electro-dissolution while the platinum metal deposits out of solution onto the nanotube paper via a galvanic displacement reaction. The samples were characterized using SEM/EDS, and Hall-effect measurements. The SEM/EDS analysis clearly revealed deposits of platinum (Pt distributed over the nanotube paper surface, and the qualitative elemental analysis revealed co-deposition of other elements from the metal substrates used. When stainless steel was used as sacrificial metal a large degree of Pt contamination with various other metals was observed. Whereas when pure sacrificial metals were used bimetallic Pt clusters resulted. The co-deposition of a bimetallic system upon carbon nanotubes was a function of the metal type and the time of exposure. Hall-effect measurements revealed some interesting fluctuations in sheet carrier density and the dominant carrier switched from N- to P-type when Pt was deposited onto the nanotube paper. Perspectives on the use of the nanotube paper as a replacement to traditional carbon cloth in water electrolysis systems are also discussed.

  3. PdCo porous nanostructures decorated on polypyrrole @ MWCNTs conductive nanocomposite-Modified glassy carbon electrode as a powerful catalyst for ethanol electrooxidation

    Science.gov (United States)

    Fard, Leyla Abolghasemi; Ojani, Reza; Raoof, Jahan Bakhsh; Zare, Ehsan Nazarzadeh; Lakouraj, Moslem Mansour

    2017-04-01

    In the current study, well-defined PdCo porous nanostructure (PdCo PNS) is prepared by a simple one-pot wet-chemical method and polypyrrole@multi-walled carbon nanotubes (PPy@MWCNTs) nanocomposite is used as a catalyst support. The morphology and the structural properties of the prepared catalyst were studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The electrocatalytic performance of PdCo PNS/PPy@MWCNTs on glassy carbon electrode has been evaluated by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) techniques. The specific activity of PdCo PNS/PPy@MWCNTs for ethanol electrooxidation (1.65 mA cm-2) is higher than those of other compared electrocatalysts. Also, PdCo PNS/PPy@MWCNTs catalyst represented higher electrocatalytic activity, better long-term stability and high level of poisoning tolerance to the carbonaceous oxidative intermediates for ethanol electrooxidation reaction in alkaline media. Furthermore, the presence of PPY@MWCNTs on the surface of GCE produce a high activity to electrocatalyst, which might be due to the easier charge transfer at polymer/carbon nanotubes interfaces, higher electrochemically accessible surface areas and electronic conductivity. The superior catalytic activity of PdCo PNS/PPy@MWCNTs suggests it to be as a promising electrocatalyst for future direct ethanol fuel cells.

  4. Preparation of yttrium hexacyanoferrate/carbon nanotube/Nafion nanocomposite film-modified electrode: Application to the electrocatalytic oxidation of L-cysteine

    International Nuclear Information System (INIS)

    Qu Lingbo; Yang Suling; Li Gang; Yang Ran; Li Jianjun; Yu Lanlan

    2011-01-01

    An yttrium hexacyanoferrate nanoparticle/multi-walled carbon nanotube/Nafion (YHCFNP/MWNT/Nafion)-modified glassy carbon electrode (GCE) was constructed. Several techniques, including infrared spectroscopy, energy dispersive spectrometry, scanning electron microscopy and electrochemistry, were performed to characterize the yttrium hexacyanoferrate nanoparticles. The electrochemical behavior of the YHCFNP/MWNT/Nafion-modified GCE in response to L-cysteine oxidation was studied. The response current of L-cysteine oxidation at the YHCFNP/MWNT/Nafion-modified GCE was obviously higher than that at the bare GCE or other modified GCE. The effects of pH, scan rate and interference on the response to L-cysteine oxidation were investigated. In addition, on the basis of these findings, a determination of L-cysteine at the YHCFNP/MWNT/Nafion-modified GCE was carried out. Under the optimum experimental conditions, the electrochemical response to L-cysteine at the YHCFNP/MWNT/Nafion-modified GCE was fast (within 4 s). Linear calibration plots were obtained over the range of 0.20-11.4 μmol L -1 with a low detection limit of 0.16 μmol L -1 . The YHCFNP/MWNT/Nafion-modified GCE exhibited several advantages, such as high stability and good resistance against interference by ascorbic acid and other oxidizable amino acids.

  5. Impedimetric PSA aptasensor based on the use of a glassy carbon electrode modified with titanium oxide nanoparticles and silk fibroin nanofibers.

    Science.gov (United States)

    Benvidi, Ali; Banaei, Maryam; Tezerjani, Marzieh Dehghan; Molahosseini, Hosein; Jahanbani, Shahriar

    2017-12-14

    This article describes an impedimetric aptasensor for the prostate specific antigen (PSA), a widely accepted prostate cancer biomarker. A glassy carbon electrode (GCE) was modified with titanium oxide nanoparticles (TiO 2 ) and silk fibroin nanofiber (SF) composite. The aptasensor was obtained by immobilizing a PSA-binding aptamer on the AuNP-modified with 6-mercapto-1-hexanol. The single fabrication steps were characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The assay has two linear response ranges (from 2.5 fg.mL -1 to 25 pg.mL -1 , and from 25 pg.mL -1 to 25 ng.mL -1 ) and a 0.8 fg.mL -1 detection limit. After optimization of experimental conditions, the sensor is highly selective for PSA over bovine serum albumin and lysozyme. It was successfully applied to the detection of PSA in spiked serum samples. Graphical abstract Schematic of the fabrication of an aptasensor for the prostate specific antigen (PSA). It is based on the use of a glassy carbon electrode modified with gold nanoparticles and titanium oxide-silk fibroin. The immobilization process of aptamer and interaction with PSA were followed by electrochemical impedance spectroscopy technique.

  6. Cellobiose Dehydrogenase Aryl Diazonium Modified Single Walled Carbon Nanotubes: Enhanced Direct Electron Transfer through a Positively Charged Surface

    Science.gov (United States)

    2011-01-01

    One of the challenges in the field of biosensors and biofuel cells is to establish a highly efficient electron transfer rate between the active site of redox enzymes and electrodes to fully access the catalytic potential of the biocatalyst and achieve high current densities. We report on very efficient direct electron transfer (DET) between cellobiose dehydrogenase (CDH) from Phanerochaete sordida (PsCDH) and surface modified single walled carbon nanotubes (SWCNT). Sonicated SWCNTs were adsorbed on the top of glassy carbon electrodes and modified with aryl diazonium salts generated in situ from p-aminobenzoic acid and p-phenylenediamine, thus featuring at acidic pH (3.5 and 4.5) negative or positive surface charges. After adsorption of PsCDH, both electrode types showed excellent long-term stability and very efficient DET. The modified electrode presenting p-aminophenyl groups produced a DET current density of 500 μA cm−2 at 200 mV vs normal hydrogen reference electrode (NHE) in a 5 mM lactose solution buffered at pH 3.5. This is the highest reported DET value so far using a CDH modified electrode and comes close to electrodes using mediated electron transfer. Moreover, the onset of the electrocatalytic current for lactose oxidation started at 70 mV vs NHE, a potential which is 50 mV lower compared to when unmodified SWCNTs were used. This effect potentially reduces the interference by oxidizable matrix components in biosensors and increases the open circuit potential in biofuel cells. The stability of the electrode was greatly increased compared with unmodified but cross-linked SWCNTs electrodes and lost only 15% of the initial current after 50 h of constant potential scanning. PMID:21417322

  7. Low potential stable glucose detection at dendrimers modified polyaniline nanotubes

    Directory of Open Access Journals (Sweden)

    Alessandra Nogueira Santos

    2010-03-01

    Full Text Available The utilization of nanostructured materials for development of biosensors is a growing field in medical diagnostics. In this work a glucose biosensor based on bioactive polyglycerol (PGLD and chitosan dendrimers (CHD was developed. PGLD and CHD were bioconjugated with the enzyme glucose oxidase (GOx to obtain dendrimers with glucose sensing properties. Polyaniline nanotubes (PANINT´s were used as electron mediator due to their high ability to promote electron-transfer reactions involving GOx. The PGLD-GOx and CHD-GOx were entrapped in PANINT´s during template electrochemical polymerization of aniline. The prepared PGLD-GOx/PANINT´s and CHD-GOx/PANINT´s biosensors exhibit a strong and stable amperometric response to glucose even at a low potential of +100 mV. The based PGLD-GOx/PANINT´s and CHD-GOx/PANINT´s biosensors showed a good performance in glucose concentrations range in human blood. A comparison of the sensitivities to glucose showed that both biosensors have a linearity range between 0.02 and 10 mM, though PGLD-GOx/PANINT´s is more sensitive (10.41 vs. 7.04 nA.mM-1. The difference in the biosensor behavior and the high sensitivity of the PGLD-GOx/PANINT´s may be due to the specific organization of GOx layer at surface of the modifier macromolecule PGLD and their distribution in PANINT´s. The enzyme affinity for the substrate, K Mapp remains quite good after GOx immobilization on PGLD and CHD dendrimers and entrapment of the bioconjugates in PANINT´s.

  8. Selective Detection of Serotonin from the Interference by Ascorbic Acid and Uric Acid at Poly(thionine)-modified Glassy Carbon Electrode

    Energy Technology Data Exchange (ETDEWEB)

    Ahammad, A. J. Saleh; Nath, Narayan Chandra Deb; Kim, Sung Hyun [Konkuk University, Seoul (Korea, Republic of); Kim, Young Jun; Lee, Jae Joon [Konkuk University, Chungju (Korea, Republic of)

    2011-03-15

    Various approaches, such as using polymer film modified electrode, applying chemical modification, employing nano materials and molecularly imprinted polymers, have been developed to detect 5-HT selectively from interferences. The polymer-modified electrodes have widely been used because of their enhanced selectivity and sensitivity for many analytes. Previously, we have reported the role of poly(thionine) film (PTH) deposited on the electrochemically preanodized glassy carbon electrode (GCE) for the separation of the voltammetric signal of dopamine (DA) from that of AA and UA. In this communication, we are presenting the preliminary results of the electrochemical signal separation of 5-HT by suppressing those of AA and UA on another type PTH modified GCE (PTHGCE) which is prepared by electrochemical deposition of PTH directly on the mechanically polished GCE.

  9. Synthesis of palladium nanoparticle modified reduced graphene oxide and multi-walled carbon nanotube hybrid structures for electrochemical applications

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Jie, E-mail: hujie@tyut.edu.cn [Micro and Nano System Research Center, Key Lab of Advanced Transducers and Intelligent Control System (Ministry of Education) & College of Information Engineering, Taiyuan University of Technology, Taiyuan, 030024, Shanxi (China); Zhao, Zhenting; Zhang, Jun; Li, Gang; Li, Pengwei; Zhang, Wendong [Micro and Nano System Research Center, Key Lab of Advanced Transducers and Intelligent Control System (Ministry of Education) & College of Information Engineering, Taiyuan University of Technology, Taiyuan, 030024, Shanxi (China); Lian, Kun, E-mail: liankun@tyut.edu.cn [Micro and Nano System Research Center, Key Lab of Advanced Transducers and Intelligent Control System (Ministry of Education) & College of Information Engineering, Taiyuan University of Technology, Taiyuan, 030024, Shanxi (China); School of Nano-Science and Nano-Engineering, Suzhou & Collaborative Innovation Center of Suzhou Nano Science and Technology, Xi' an Jiaotong University, Xi' an, 710049 (China); Center for Advanced Microstructures and Devices, Louisiana State University, LA, 70806 (United States)

    2017-02-28

    Graphical abstract: A sensitive hydrazine electrochemical sensor was fabricated by using palladium (Pd) nanoparticle functionalized reduced graphene oxide (rGO) and multi-walled carbon nanotube (MWCNTs) hybrid structures (Pd/rGO-MWCNTs). - Highlights: • rGO-MWCNTs hybrid structures and Pd nanoparticles are prepared using electrochemical methods. • rGO-MWCNTs hybrid films are used as supports and co-catalysts for Pd nanoparticles. • The Pd/rGO-MWCNTs hybrid structure based sensor shows an ultra-high sensitivity of 7.09 μA μM{sup −1} cm{sup −2} and a low detection limit of 0.15 μM. • The proposed electrochemical sensor exhibits excellent selectivity. - Abstract: In this work, palladium (Pd) nanoparticles functionalized reduced graphene oxide (rGO) and multi-walled carbon nanotubes (MWCNTs) hybrid structures (Pd/rGO-MWCNTs) were successfully prepared by a combination of electrochemical reduction with electrodeposition method. The morphology, structure, and composition of the Pd/rGO-MWCNTs hybrid were characterized by scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy. The as-synthesized hybrid structures were modified on the glassy carbon electrode (GCE) and further utilized for hydrazine sensing. Electrochemical impedance spectroscopic, cyclic voltammetry and single-potential amperometry experiments were carried out on Pd/rGO-MWCNTs hybrid structures to investigate the interface properties and sensing performance. The measured results demonstrate that the fabricated Pd/rGO-MWCNTs/GCE sensor show a high sensitivity of 7.09 μA μM{sup −1} cm{sup −2} in a large concentration range of 1.0 to 1100 μM and a low detection limit of 0.15 μM. Moreover, the as-prepared sensor exhibits good selectivity and stability for the determination of hydrazine under interference conditions.

  10. Synthesis of palladium nanoparticle modified reduced graphene oxide and multi-walled carbon nanotube hybrid structures for electrochemical applications

    International Nuclear Information System (INIS)

    Hu, Jie; Zhao, Zhenting; Zhang, Jun; Li, Gang; Li, Pengwei; Zhang, Wendong; Lian, Kun

    2017-01-01

    Graphical abstract: A sensitive hydrazine electrochemical sensor was fabricated by using palladium (Pd) nanoparticle functionalized reduced graphene oxide (rGO) and multi-walled carbon nanotube (MWCNTs) hybrid structures (Pd/rGO-MWCNTs). - Highlights: • rGO-MWCNTs hybrid structures and Pd nanoparticles are prepared using electrochemical methods. • rGO-MWCNTs hybrid films are used as supports and co-catalysts for Pd nanoparticles. • The Pd/rGO-MWCNTs hybrid structure based sensor shows an ultra-high sensitivity of 7.09 μA μM"−"1 cm"−"2 and a low detection limit of 0.15 μM. • The proposed electrochemical sensor exhibits excellent selectivity. - Abstract: In this work, palladium (Pd) nanoparticles functionalized reduced graphene oxide (rGO) and multi-walled carbon nanotubes (MWCNTs) hybrid structures (Pd/rGO-MWCNTs) were successfully prepared by a combination of electrochemical reduction with electrodeposition method. The morphology, structure, and composition of the Pd/rGO-MWCNTs hybrid were characterized by scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy. The as-synthesized hybrid structures were modified on the glassy carbon electrode (GCE) and further utilized for hydrazine sensing. Electrochemical impedance spectroscopic, cyclic voltammetry and single-potential amperometry experiments were carried out on Pd/rGO-MWCNTs hybrid structures to investigate the interface properties and sensing performance. The measured results demonstrate that the fabricated Pd/rGO-MWCNTs/GCE sensor show a high sensitivity of 7.09 μA μM"−"1 cm"−"2 in a large concentration range of 1.0 to 1100 μM and a low detection limit of 0.15 μM. Moreover, the as-prepared sensor exhibits good selectivity and stability for the determination of hydrazine under interference conditions.

  11. Amperometric immunosensor based on multiwalled carbon nanotubes/Prussian blue/nanogold-modified electrode for determination of α-fetoprotein.

    Science.gov (United States)

    Jiang, Wen; Yuan, Ruo; Chai, Ya-Qin; Yin, Bing

    2010-12-01

    In this article, a conspicuously simple and highly sensitive amperometric immunosensor based on the sequential electrodeposition of Prussian blue (PB) and gold nanoparticles (GNPs) on multiwalled carbon nanotube (MWCNT)-modified glassy carbon electrode (GCE) surface is proposed for the detection of α-fetoprotein (AFP). By comparison with PB, the MWCNT/PB composite film had been proven to show much better electrochemical stability and a larger response current. The electrodeposited GNP film can be used not only to immobilize biomolecules but also to avoid the leakage of PB and to prevent shedding of MWCNT/PB composite film from the electrode surface. The performance and factors influencing the performance of the immunosensor were investigated. Under optimal experimental conditions, the proposed immunosensor for AFP was observed with an ultralow limit of detection (LOD) equal to 3 pg/ml (at 3δ), and the linear working range spanned the concentrations of AFP from 0.01 to 300 ng/ml. Moreover, the immunosensor, as well as a commercially available kit, was examined for use in the determination of AFP in real human serum specimens. More significant, the assay mentioned here is simpler than the traditional enzyme-linked immunosorbent assay (ELISA), and an excellent correlation of levels of AFP measured was obtained, indicating that the developed immunoassay could be a promising alternative approach for detection of AFP and other tumor markers in the clinical diagnosis. Copyright © 2010 Elsevier Inc. All rights reserved.

  12. Characterization of poly(5-hydroxytryptamine)-modified glassy carbon electrode and applications to sensing of norepinephrine and uric acid in preparations and human urines

    International Nuclear Information System (INIS)

    Shi, Peiying; Miao, Xiaoqing; Yao, Hong; Lin, Sijie; Wei, Biyu; Chen, Jianji; Lin, Xinhua; Tang, Yuhai

    2013-01-01

    Graphical abstract: A 5-hydroxytryptamine (5-HT) modified electrode was fabricated by electro-polymerization of 5-HT on a glassy carbon electrode (GCE) by cyclic voltammetry (CV) in 0.05 M PBS (pH 7). The characterization of the modified electrode was carried out by atomic force microscopy (AFM), voltammetry and electrochemical impedance spectroscopy (EIS). The mechanism of electro-deposition of 5-HT at GCE was discussed based on electrochemical studies and quantum chemical calculations. The poly(5-HT)-modified electrode could separately detect NE and UA, even in the presence of 10-fold concentration of ascorbic acid (AA) and was applied successfully to the analysis of NE preparations and healthy human urines. Due to the favorable functionalized groups (-NH 2 and -OH), electroactivity, biocompatibility and stability, the poly(5-HT) film could be a promising immobilization matrix for anchoring interested biological molecules in the fabrication of sensors and biosensors. Highlights: ► A poly(5-HT)-modified electrode was fabricated originally by CV. ► The electro-deposition mechanism of 5-HT at GCE was proposed. ► The polymer film shows favorable electrocatalytic properties to NE and UA. ► The modified GCE was applied to the sensing analysis of real samples. -- Abstract: A poly(5-hydroxytryptamine) (poly(5-HT)) modified electrode was fabricated by electropolymerization of 5-hydroxytryptamine (5-HT) on a glassy carbon electrode (GCE) by cyclic voltammetry (CV) in 0.05 M PBS (pH 7). The characterization of poly(5-HT)-modified electrode was carried out by atomic force microscopy (AFM), voltammetry and electrochemical impedance spectroscopy (EIS). Results showed that a brown and heterogeneous film was formed on the surface of the modified electrode. The mechanism of electro-deposition of 5-HT at GCE was discussed. The modified electrode showed good affinity and electrocatalytic properties to some species, such as norepinephrine (NE) and uric acid (UA). Furthermore

  13. Electrochemical characterization of glassy carbon electrode modified with 1,10-phenanthroline groups by two pathways: reduction of the corresponding diazonium ions and reduction of phenanthroline

    International Nuclear Information System (INIS)

    Shul, Galyna; Weissmann, Martin; Bélanger, Daniel

    2015-01-01

    The electrochemical behaviour of 1,10-phenanthroline molecules immobilized on a glassy carbon electrode surface by electrochemical reduction of the corresponding in-situ generated diazonium ions in an aqueous solution was investigated. Firstly, the derivatization of glassy carbon electrode was confirmed by the presence of the barrier effect in the solution of a redox probe. Secondly, atomic force microscopy measurements revealed the deposition of thin (< 2 nm) uniform 1,10-phenanthroline film on the surface of pyrolyzed photoresist film electrode. Thirdly, the initially electrochemically inactive grafted organic film became electroactive after being subjected to electrochemical reduction and oxidation. Fourthly, the electrochemical behaviour of phenanthroline modified electrode by electrochemical reduction of the corresponding diazonium cations was found to be similar to that of electrode modified by electrochemical reduction of only phenanthroline dissolved in an aqueous acid solution. Finally, cyclic voltammetry experiments using various methyl substituted phenanthroline derivatives provided direct evidence that functional groups responsible for the film electroactivity are formed at 5 or/and 6 positions of grafted phenanthroline molecules. On the other hand, a phenanthroline derivative having these positions blocked by methyl groups can also display electroactivity with position 7 being most likely involved in the observed redox process

  14. Glassy carbon electrodes modified with a film of nanodiamond-graphite/chitosan: Application to the highly sensitive electrochemical determination of Azathioprine

    International Nuclear Information System (INIS)

    Shahrokhian, Saeed; Ghalkhani, Masoumeh

    2010-01-01

    A novel modified glassy carbon electrode with a film of nanodiamond-graphite/chitosan is constructed and used for the sensitive voltammetric determination of azathioprine (Aza). The surface morphology and thickness of the film modifier are characterized using atomic force microscopy. The electrochemical response characteristics of the electrode toward Aza are investigated by means of cyclic voltammetry. The modified electrode showed an efficient catalytic role for the electrochemical reduction of Aza, leading to a remarkable decrease in reduction overpotential and enhancement of the kinetics of the electrode reaction with a significant increase of peak current. The effects of experimental variables, such as the deposited amount of modifier suspension, the pH of the supporting electrolyte, the accumulation potential and time were investigated. Under optimal conditions, the modified electrode showed a wide linear response to the concentration of Aza in the range of 0.2-100 μM with a detection limit of 65 nM. The prepared modified electrode showed several advantages: simple preparation method, high stability and uniformity in the composite film, high sensitivity, excellent catalytic activity in physiological conditions and good reproducibility. The modified electrode can be successfully applied to the accurate determination of trace amounts of Aza in pharmaceutical and clinical preparations.

  15. Glassy carbon electrodes modified with a film of nanodiamond-graphite/chitosan: Application to the highly sensitive electrochemical determination of Azathioprine

    Energy Technology Data Exchange (ETDEWEB)

    Shahrokhian, Saeed, E-mail: shahrokhian@sharif.ed [Department of Chemistry, Sharif University of Technology, Tehran 11155-9516 (Iran, Islamic Republic of); Institute for Nanoscience and Technology, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Ghalkhani, Masoumeh [Department of Chemistry, Sharif University of Technology, Tehran 11155-9516 (Iran, Islamic Republic of)

    2010-04-15

    A novel modified glassy carbon electrode with a film of nanodiamond-graphite/chitosan is constructed and used for the sensitive voltammetric determination of azathioprine (Aza). The surface morphology and thickness of the film modifier are characterized using atomic force microscopy. The electrochemical response characteristics of the electrode toward Aza are investigated by means of cyclic voltammetry. The modified electrode showed an efficient catalytic role for the electrochemical reduction of Aza, leading to a remarkable decrease in reduction overpotential and enhancement of the kinetics of the electrode reaction with a significant increase of peak current. The effects of experimental variables, such as the deposited amount of modifier suspension, the pH of the supporting electrolyte, the accumulation potential and time were investigated. Under optimal conditions, the modified electrode showed a wide linear response to the concentration of Aza in the range of 0.2-100 muM with a detection limit of 65 nM. The prepared modified electrode showed several advantages: simple preparation method, high stability and uniformity in the composite film, high sensitivity, excellent catalytic activity in physiological conditions and good reproducibility. The modified electrode can be successfully applied to the accurate determination of trace amounts of Aza in pharmaceutical and clinical preparations.

  16. Disposable pencil graphite electrode modified with peptide nanotubes for Vitamin B{sub 12} analysis

    Energy Technology Data Exchange (ETDEWEB)

    Pala, Betül Bozdoğan [Nanotechnology and Nanomedicine Division, Institute of Science, Hacettepe University, 06800 Ankara (Turkey); Vural, Tayfun [Department of Chemistry, Faculty of Science, Hacettepe University, 06800 Beytepe, Ankara (Turkey); Kuralay, Filiz [Department of Chemistry, Faculty of Science and Arts, Ordu University, 52200 Ordu (Turkey); Çırak, Tamer [Nanotechnology and Nanomedicine Division, Institute of Science, Hacettepe University, 06800 Ankara (Turkey); Bolat, Gülçin; Abacı, Serdar [Department of Chemistry, Faculty of Science, Hacettepe University, 06800 Beytepe, Ankara (Turkey); Denkbaş, Emir Baki, E-mail: denkbas@hacettepe.edu.tr [Department of Chemistry, Faculty of Science, Hacettepe University, 06800 Beytepe, Ankara (Turkey)

    2014-06-01

    In this study, peptide nanostructures from diphenylalanine were synthesized in various solvents with various polarities and characterized with Scanning Electron Microscopy (SEM) and Powder X-ray Diffraction (PXRD) techniques. Formation of peptide nanofibrils, nanovesicles, nanoribbons, and nanotubes was observed in different solvent mediums. In order to investigate the effects of peptide nanotubes (PNT) on electrochemical behavior of disposable pencil graphite electrodes (PGE), electrode surfaces were modified with fabricated peptide nanotubes. Electrochemical activity of the pencil graphite electrode was increased with the deposition of PNTs on the surface. The effects of the solvent type, the peptide nanotube concentration, and the passive adsorption time of peptide nanotubes on pencil graphite electrode were studied. For further electrochemical studies, electrodes were modified for 30 min by immobilizing PNTs, which were prepared in water at 6 mg/mL concentration. Vitamin B{sub 12} analyses were performed by the Square Wave (SW) voltammetry method using modified PGEs. The obtained data showed linearity over the range of 0.2 μM and 9.50 μM Vitamin B{sub 12} concentration with high sensitivity. Results showed that PNT modified PGEs were highly simple, fast, cost effective, and feasible for the electro-analytical determination of Vitamin B{sub 12} in real samples.

  17. Disposable pencil graphite electrode modified with peptide nanotubes for Vitamin B12 analysis

    International Nuclear Information System (INIS)

    Pala, Betül Bozdoğan; Vural, Tayfun; Kuralay, Filiz; Çırak, Tamer; Bolat, Gülçin; Abacı, Serdar; Denkbaş, Emir Baki

    2014-01-01

    In this study, peptide nanostructures from diphenylalanine were synthesized in various solvents with various polarities and characterized with Scanning Electron Microscopy (SEM) and Powder X-ray Diffraction (PXRD) techniques. Formation of peptide nanofibrils, nanovesicles, nanoribbons, and nanotubes was observed in different solvent mediums. In order to investigate the effects of peptide nanotubes (PNT) on electrochemical behavior of disposable pencil graphite electrodes (PGE), electrode surfaces were modified with fabricated peptide nanotubes. Electrochemical activity of the pencil graphite electrode was increased with the deposition of PNTs on the surface. The effects of the solvent type, the peptide nanotube concentration, and the passive adsorption time of peptide nanotubes on pencil graphite electrode were studied. For further electrochemical studies, electrodes were modified for 30 min by immobilizing PNTs, which were prepared in water at 6 mg/mL concentration. Vitamin B 12 analyses were performed by the Square Wave (SW) voltammetry method using modified PGEs. The obtained data showed linearity over the range of 0.2 μM and 9.50 μM Vitamin B 12 concentration with high sensitivity. Results showed that PNT modified PGEs were highly simple, fast, cost effective, and feasible for the electro-analytical determination of Vitamin B 12 in real samples.

  18. Strain-modified RKKY interaction in carbon nanotubes

    DEFF Research Database (Denmark)

    Gorman, P. D.; Duffy, J. M.; Power, Stephen R.

    2015-01-01

    been shown that the interaction range depends on the conformation of the magnetic dopants in both graphene and nanotubes. Here we examine the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction in carbon nanotubes in the presence of uniaxial strain for a range of different impurity configurations. We show......For low-dimensionalmetallic structures, such as nanotubes, the exchange coupling between localized magnetic dopants is predicted to decay slowly with separation. The long-range character of this interaction plays a significant role in determining the magnetic order of the system. It has previously...... that strain is capable of amplifying or attenuating the RKKY interaction, significantly increasing certain interaction ranges, and acting as a switch: effectively turning on or off the interaction. We argue that uniaxial strain can be employed to significantly manipulate magnetic interactions in carbon...

  19. Electrocatalytic determination of L-ascorbic acid by modified glassy carbon with Ni(Me2(CH3CO)2[14]tetraenoN4) complex.

    Science.gov (United States)

    Khorasani-Motlagh, Mozhgan; Noroozifar, Meissam

    2003-12-01

    A novel modified glassy carbon electrode containing Ni(Me2(CH3CO)2[14]tetraenoN4) complex was used as an electrocatalytic sensor for the determination of L-ascorbic acid in pH = 6.6. The peak potential shifted to negative by 205 mV compared with that for a bare electrode in cyclic voltammograms. The calibration curve was linear up to 6.2 x 10(-3) M with a detection limit 3.1 x 10(-7) M and an RSD% better than 2.47%. This newly modified electrode was applied to commercial pharmaceutical tablets, injections and foods. The obtained results were identical to those obtained by the classical 2,6-dichlorophenolindophenol method.

  20. A glassy carbon electrode modified with an iron N4-macrocycle and reduced graphene oxide for voltammetric sensing of dissolved oxygen

    International Nuclear Information System (INIS)

    Silva, Saimon M.; Aguiar, Lucas F.; Carvalho, Rita M. S.; Tanaka, Auro A.; Damos, Flavio S.; Luz, Rita C. S.

    2016-01-01

    The authors describe a platform for the electrochemical reduction of oxygen. It is based on the use of a glassy carbon electrode (GCE) that was modified in a single-step microwave assisted reaction with a N4-macrocycle containing iron(III) (FeN4) and with reduced graphene oxide. The FeN4/rGO composite was characterized by cyclic voltammetry, differential pulse voltammetry, and scanning electrochemical microscopy (SECM). Cyclic voltammetry showed the composite to enable efficient reduction of O_2 at a very low overpotential (−0.05 V vs. Ag/AgCl). SECM measurements were carried out to map (in the redox competition mode) the activity of a GCE microelectrode modified with FeN4/rGO. Under optimized conditions, the response to dissolved O_2 ranges from 0.8 up to 25 mg⋅L"-"1, and the limit of detection is 0.2 mg⋅L"-"1. (author)

  1. Simultaneous detection of metronidazole and chloramphenicol by differential pulse stripping voltammetry using a silver nanoparticles/sulfonate functionalized graphene modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Zhai, Haiyun; Liang, Zhixian; Chen, Zuanguang; Wang, Haihang; Liu, Zhenping; Su, Zihao; Zhou, Qing

    2015-01-01

    Graphical abstract: Display Omitted -- Highlights: • A novel and reliable AgNPs/SF-GR modified glassy carbon electrode was constructed and characterized. • The AgNPs/SF-GR/GCE was successfully applied in the shrimp for simultaneous determination of MTZ and CAP. • Under optimized conditions, common substances such as UA, AA, DA and ion did not interfered in the electrode performance. • The modified electrode exhibited considerable sensitivity, stability and reproducibility. • This fabricated electrode achieved a satisfactory level compared with other electrodes toward MTZ and CAP. -- Abstract: A novel silver nanoparticles/sulfonated functionalized graphene modified glassy carbon electrode (AgNPs/SF-GR/GCE) was fabricated to determine chloramphenicol and metronidazole simultaneously. Taking advantage of sulfonic group, AgNPs were successfully electrodeposited on functionalized GR immobilized on the surface of a GCE. Scanning electron microscopy and energy spectrum analysis results confirmed that AgNPs were deposited on the functionalized GR film. Compared to the bare GCE or the pristine SF-GR modified electrode, AgNPs/SF-GR/GCE exhibited excellent electroreduction towards chloramphenicol and metronidazole. In addition, the two antibacterial drugs were separated completely in 0.10 M citric acid-sodium citrate buffer (pH 4.0) by differential pulse stripping voltammetry under optimum conditions. The cathodic current was linearly related with 0.02∼20.0 μM chloramphenicol and 0.10∼20.0 μM metronidazole, with the detection limits of 0.01 μM and 0.05 μM respectively. Furthermore, AgNPs/SF-GR/GCE was applied to the simultaneous determination of chloramphenicol and metronidazole in an aquatic product

  2. A sensitive voltammetric detection of pramipexole based on 1,1,3,3-tetramethyldisilazanecarbon nanotube modified electrode

    Energy Technology Data Exchange (ETDEWEB)

    Amirighadi, Saeede [Electroanalytical Chemistry Research Laboratory, Department of Analytical Chemistry, Faculty of Chemistry, University of Mazandaran, Babolsar (Iran, Islamic Republic of); Raoof, Jahan Bakhsh, E-mail: j.raoof@umz.ac.ir [Electroanalytical Chemistry Research Laboratory, Department of Analytical Chemistry, Faculty of Chemistry, University of Mazandaran, Babolsar (Iran, Islamic Republic of); Department of Chemistry, Ayatollah Amoli Branch, Islamic Azad University, Amol (Iran, Islamic Republic of); Chekin, Fereshteh [Department of Chemistry, Ayatollah Amoli Branch, Islamic Azad University, Amol (Iran, Islamic Republic of); Ojani, Reza [Electroanalytical Chemistry Research Laboratory, Department of Analytical Chemistry, Faculty of Chemistry, University of Mazandaran, Babolsar (Iran, Islamic Republic of)

    2017-06-01

    A simple low-cost method is proposed to fabricate a functionalized multi-wall carbon nanotube (MWCNT) with 1,1,3,3-tetramethyldisilazane (TMDS) molecule. The techniques of scanning electron microscope (SEM) with electron diffraction and energy dispersive X-ray (EDAX) analysis were applied to characterize the functionalized TMDS-MWCNT. The results showed that a MWCNT with high functionalization of TMDS can be obtained using this simple method. A new nanostructure sensor was constructed based on a glassy carbon electrode modified with TMDS-MWCNT (TMDS-MWCNT/GCE). It was found that the TMDS-MWCNT/GCE exhibits good catalytic activity toward oxidation of pramipexole (PPX) drug, leading to a concentration range of 0.8 to 600 μM with a detection limit of 0.2 μM at 3σ using the differential pulse voltammetry technique, a sensitivity of 0.084 μA μM{sup −1}, and a correlation coefficient of 0.991. Furthermore, the TMDS-MWCNT/GCE was used for PPX detection in tablets and human blood serum samples. The method showed no interference from tablet excipients; hence, it can be useful and fit for the quantification of PPX in bulk and tablet dosage forms. The proposed method was validated successfully as applied to the quantification of the drug in tablet dosage forms. The accuracy of detection results using the proposed method was evaluated as excellent comparing with those obtained by the reference method. - Highlights: • The MWCNT was functionalized with TMDS molecule by a simple and low-cost method. • The new nanostructure sensor based on glassy carbon electrode modified with TMDS-MWCNT • It was found that TMDS-MWCNT/GCE exhibits good catalytic activity toward the oxidation of pramipexole. • This sensor showed concentration range of 0.8 to 600 μM with a detection limit of 0.2 μM. • The proposed method does not differ significantly in precision and accuracy from the reference method.

  3. PdCo porous nanostructures decorated on polypyrrole @ MWCNTs conductive nanocomposite—Modified glassy carbon electrode as a powerful catalyst for ethanol electrooxidation

    Energy Technology Data Exchange (ETDEWEB)

    Fard, Leyla Abolghasemi [Electroanalytical Chemistry Research Laboratory, Department of Analytical Chemistry, Faculty of Chemistry, University of Mazandaran, 3rd Kilometer of Air Force Road, 47416-95447, Babolsar (Iran, Islamic Republic of); Ojani, Reza, E-mail: fer-o@umz.ac.ir [Electroanalytical Chemistry Research Laboratory, Department of Analytical Chemistry, Faculty of Chemistry, University of Mazandaran, 3rd Kilometer of Air Force Road, 47416-95447, Babolsar (Iran, Islamic Republic of); Raoof, Jahan Bakhsh [Electroanalytical Chemistry Research Laboratory, Department of Analytical Chemistry, Faculty of Chemistry, University of Mazandaran, 3rd Kilometer of Air Force Road, 47416-95447, Babolsar (Iran, Islamic Republic of); Zare, Ehsan Nazarzadeh; Lakouraj, Moslem Mansour [Polymer Research Laboratory Department of Organic-Polymer Chemistry, Faculty of Chemistry, University of Mazandaran, 3rd Kilometer of Air Force Road, 47416-95447, Babolsar (Iran, Islamic Republic of)

    2017-04-15

    Highlights: • The PdCo PNS/PPy@MWCNT electrocatalyst was easily prepared. • The electrocatalyst exhibits high electrocatalytic activity and stability toward the EOR. • The specific activity of PdCo PNS/PPy@MWCNTs for ethanol electrooxidation (1.65 mA cm{sup −2}) is higher than those of other compared electrocatalysts. • The high electrocatalytic performance is attributed to concerted effects of Porous nature, Co and PPy@MWCNT. • The PdCo PNS/PPy@MWCNT electrocatalyst has never been reported. - Abstract: In the current study, well-defined PdCo porous nanostructure (PdCo PNS) is prepared by a simple one-pot wet-chemical method and polypyrrole@multi-walled carbon nanotubes (PPy@MWCNTs) nanocomposite is used as a catalyst support. The morphology and the structural properties of the prepared catalyst were studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The electrocatalytic performance of PdCo PNS/PPy@MWCNTs on glassy carbon electrode has been evaluated by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) techniques. The specific activity of PdCo PNS/PPy@MWCNTs for ethanol electrooxidation (1.65 mA cm{sup −2}) is higher than those of other compared electrocatalysts. Also, PdCo PNS/PPy@MWCNTs catalyst represented higher electrocatalytic activity, better long-term stability and high level of poisoning tolerance to the carbonaceous oxidative intermediates for ethanol electrooxidation reaction in alkaline media. Furthermore, the presence of PPY@MWCNTs on the surface of GCE produce a high activity to electrocatalyst, which might be due to the easier charge transfer at polymer/carbon nanotubes interfaces, higher electrochemically accessible surface areas and electronic conductivity. The superior catalytic activity of PdCo PNS/PPy@MWCNTs suggests it to be as a promising electrocatalyst for future direct ethanol fuel cells.

  4. Electrochemical mechanism of eugenol at a Cu doped gold nanoparticles modified glassy carbon electrode and its analytical application in food samples

    International Nuclear Information System (INIS)

    Lin, Xiaoyun; Ni, Yongnian; Kokot, Serge

    2014-01-01

    Graphical abstract: A simple one-step electrodeposition method was used to fabricate a Cu doped gold nanoparticles modified glassy carbon electrode. An electrochemical reaction mechanism for o-methoxy phenols was suggested. In addition, the above Cu@AuNPs/GCE was successfully employed for the analysis of eugenol in food samples. - Highlights: • One-step construction of the Cu@AuNPs/GCE electrode. • The modified electrode showed high sensitivity for the analysis of eugenol. • Electrochemical mechanism of eugenol by use of Cu@AuNPs/GCE was inferred. • The novel method was successfully employed for analysis of eugenol in food samples. - Abstract: A simple one-step electrodeposition method was used to construct a glassy carbon electrode (GCE), which has been modified with Cu doped gold nanoparticles (GNPs), i.e. a Cu@AuNPs/GCE. This electrode was characterized with the use of scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The eugenol was electrocatalytically oxidized at the Cu@AuNPs/GCE. At this electrode, in comparison with the behavior at the GCE alone, the corresponding oxidation peak current was enhanced and the shift of the oxidation potentials to lower values was observed. Electrochemical behavior of eugenol at the Cu@AuNPs/GCE was investigated with the use of the cyclic voltammetry (CV) technique, and additionally, in order to confirm the electrochemical reaction mechanism for o-methoxy phenols, CVs for catechol, guaiacol and vanillin were investigated consecutively. Based on this work, an electrochemical reaction mechanism for o-methoxy phenols was suggested, and in addition, the above Cu@AuNPs/GCE was successfully employed for the analysis of eugenol in food samples

  5. Electrocatalytic reduction of oxygen at glassy carbon electrode modified by polypyrrole/anthraquinones composite film in various pH media

    International Nuclear Information System (INIS)

    Valarselvan, S.; Manisankar, P.

    2011-01-01

    Graphical abstract: The electrocatalytic reduction of dioxygen by one mono and four dihydroxy derivatives of 9,10-anthraquinone (AQ) incorporated in polypyrrole (PPy) matrix on glassy carbon electrode has been investigated. AQ and PPy composite film showed excellent electrocatalytic performance for the reduction of O 2 to H 2 O 2 . Highlights: → Hydroxyl derivatives of anthraquinones as electrocatalysts for dioxygen reduction. → AQ/PPy composite film on GC electrode exhibits potent electrocatalytic activity. → Substituent groups influence electrocatalytic dioxygen reduction. → Surface coverage varies the rate of electrocatalytic dioxygen reduction. - Abstract: The electrocatalytic reduction of dioxygen by one mono and four dihydroxy derivatives of 9,10-anthraquinone (AQ) incorporated in polypyrrole (PPy) matrix on glassy carbon electrode has been investigated. The electrochemical behaviour of the modified electrodes was examined in various pH media and both the formal potential of anthraquinones and reduction potential of dioxygen exhibited pH dependence. AQ and PPy composite film showed excellent electrocatalytic performance for the reduction of O 2 to H 2 O 2 . pH 6.0 was chosen as the most suitable medium to study the electrocatalysis by comparing the peak potential of oxygen reduction and enhancement in peak current for oxygen reduction. The diffusion coefficient values of AQ at the modified electrodes and the number of electrons involved in AQ reduction were evaluated by chronoamperometric and chronocoulometric techniques, respectively. In addition, hydrodynamic voltammetric studies showed the involvement of two electrons in O 2 reduction. The mass specific activity of AQ used, the diffusion coefficient of oxygen and the heterogeneous rate constants for the oxygen reduction at the surface of modified electrodes were also determined by rotating disk voltammetry.

  6. Thermal desorption of deuterium from modified carbon nanotubes and its correlation to the microstructure

    NARCIS (Netherlands)

    Lisowski, W.F.; Keim, Enrico G.; van den Berg, A.H.J.; Smithers, Mark A.; Smithers, M.A.

    2006-01-01

    The process of deuterium desorption from single-wall carbon nanotubes (SWNTs) modified by atomic (D) and molecular (D2) deuterium treatment was investigated in an ultrahigh vacuum environment using thermal desorption mass spectroscopy (TDMS). Microstructural and chemical analyses of SWNT material,

  7. Electrocatalytic oxidation of hydrazine and hydroxylamine by graphene oxide-Pd nanoparticle-modified glassy carbon electrode.

    Science.gov (United States)

    Lee, Eunhee; Kim, Daekun; You, Jung-Min; Kim, Seul Ki; Yun, Mira; Jeon, Seungwon

    2012-12-01

    Pd nanoparticle catalysts supported by thiolated graphene oxide (tGO) on a glassy carbon electrode (GCE), and denoted as tGO-Pd/GCE, are used in this study for the electrochemical determination of hydroxylamine and hydrazine. The physicochemical properties of tGO-Pd were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). They showed strong catalytic activity toward the oxidation of hydroxylamine and hydrazine. Cyclic voltammetry (CV) and amperometry were used to characterize the sensors' performances. The detection limits of hydroxylamine and hydrazine by tGO-Pd/GCE were 0.31 and 0.25 microM (s/n = 3), respectively. The sensors' sensitivity, selectivity, and stability were also investigated.

  8. Flower-Like Nanoparticles of Pt-BiIII Assembled on Agmatine Sulfate Modified Glassy Carbon Electrode and Their Electrocatalysis of H2O2

    Science.gov (United States)

    Xiao, Mingshu; Yan, Yuhua; Feng, Kai; Tian, Yanping; Miao, Yuqing

    2015-04-01

    A new electrochemical technique to detect hydrogen peroxide (H2O2) was developed. The Pt nanoparticles and BiIII were subsequently assembled on agmatine sulfate (AS) modified glassy carbon electrode (GCE) and the prepared GCE-AS-Pt-BiIII was characterized by scanning electron microscopy (SEM) with result showing that the flower-like nanostructure of Pt-BiIII was yielded. Compared with Pt nanoparticles, the flower-like nanostructure of Pt-BiIII greatly enhanced the electrocatalysis of GCE-AS-Pt-BiIII towards H2O2, which is ascribed to more Pt-OH obtained on GCE-AS-Pt-BiIII surface for the presence of BiIII. Based on its high electrocatalysis, GCE-AS-Pt-BiIII was used to determine the content of H2O2 in the sample of sheet bean curd with standard addition method. Meantime, its electrocatalytic activity also was studied.

  9. A glassy carbon electrode modified with a nanocomposite consisting of molybdenum disulfide intercalated into self-doped polyaniline for the detection of bisphenol A

    International Nuclear Information System (INIS)

    Yang, Tao; Chen, Huaiyin; Yang, Ruirui; Jiang, Yuhang; Jiao, Kui; Li, Weihua

    2015-01-01

    Thin-layered molybdenum disulfide (MoS 2 ) was intercalated, via ultrasonic exfoliation, into self-doped polyaniline (SPAN). This material, when placed on a glassy carbon electrode (GCE), exhibits excellent electrical conductivity and synergistic catalytic activity with respect to the detection of bisphenol A (BPA). The electrochemical response of the modified GCE to BPA was investigated by cyclic voltammetry and differential pulse voltammetry. Under optimal conditions, the oxidation peak current (measured best at 446 mV vs. SCE) is related to the concentration of BPA in the range from 1.0 nM to 1.0 μM, and the detection limit is 0.6 nM. (author)

  10. Chemically modified carbon nanotubes as material enhanced laser desorption ionisation (MELDI) material in protein profiling

    International Nuclear Information System (INIS)

    Najam-ul-Haq, M.; Rainer, M.; Schwarzenauer, T.; Huck, C.W.; Bonn, G.K.

    2006-01-01

    Biomarkers play a potential role in the early detection and diagnosis of a disease. Our aim is to derivatize carbon nanotubes for exploration of the differences in human body fluids e.g. serum, through matrix assisted laser desorption ionisation/time of flight mass spectrometry (MALDI/TOF-MS) that can be related to disease and subsequently to be employed in the biomarker discovery process. This application we termed as the material enhanced laser desorption ionisation (MELDI). The versatility of this technology is meant to increase the amount of information from biological samples on the protein level, which will have a major impact to serve the cause of diagnostic markers. Serum peptides and proteins are immobilized on derivatized carbon nanotubes, which function as binding material. Protein-loaded suspension is placed on a stainless steel target or buckypaper on aluminum target for direct analysis with MALDI-MS. The elution method to wash the bound proteins from carbon nanotubes was employed to compare with the direct analysis procedure. Elution is carried out by MALDI matrix solution to get them out of the entangled nanotubes, which are difficult to desorb by laser due to the complex nanotube structures. The advantage of these optimized methods compared to the conventional screening methods is the improved sensitivity, selectivity and the short analysis time without prior albumin and immunoglobulin depletion. The comparison of similarly modified diamond and carbon nanotubes exhibit differences in their nature to bind the proteins out of serum due to the differences in their physical characteristics. Infrared (IR) spectroscopy provided hint for the presence of tertiary amine peak at the crucial chemical step of iminodiacetic acid addition to acid chloride functionality on carbon nanotubes. Atomic absorption spectroscopy (AAS) was utilized to quantitatively measure the copper capacity of these derivatized carbon nanotubes which is a direct measure of capacity of

  11. Glassy Dynamics

    DEFF Research Database (Denmark)

    Jensen, Henrik J.; Sibani, Paolo

    2007-01-01

    The term glassy dynamics is often used to refer to the extremely slow relaxation observed in several types of many component systems. The time span needed to reach a steady, time independent, state will typically be far beyond experimentally accessible time scales. When melted alloys are cooled...... down they typically do not enter a crystalline ordered state. Instead the atoms retain the amorphous arrangement characteristic of the liquid high temperature phase while the mobility of the molecules decreases very many orders of magnitude. This colossal change in the characteristic dynamical time...

  12. Surface modification of halloysite nanotubes by vulcanization accelerator and properties of styrene-butadiene rubber nanocomposites with modified halloysite nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Bangchao; Jia, Zhixin, E-mail: zxjia@scut.edu.cn; Hu, Dechao; Luo, Yuanfang; Guo, Baochun; Jia, Demin

    2016-03-15

    Graphical abstract: - Highlights: • Vulcanization accelerant was used to modify halloysite nanotubes (HNTs). • The modified HNTs reduced the activation energy of vulcanization. • Strong filler–rubber interaction was achieved in rubber/modified HNTs composites. • The modified HNTs exhibited excellent reinforcement effect on rubber. - Abstract: Vulcanization accelerant N-cyclohexyl-2-benzothiazole sulfenamide (CZ) was used as a surface modifier and chemically grafted on the surface of halloysite nanotubes (HNTs) to obtain CZ-functionalized HNTs (HNTs-s-CZ). It was found that HNTs-s-CZ could be homogeneously dispersed into styrene-butadiene rubber (SBR). The grafted CZ molecules, exactly located at the filler-rubber interface, reduced the activation energy of vulcanization of SBR/HNTs-s-CZ compounds. Besides, the density of chain segments introduced by the interfacial phase of SBR/HNTs-s-CZ nanocomposites was higher than the other nanocomposites with silane-modified HNTs (m-HNTs) or pristine HNTs, manifesting an indication of enhanced filler-rubber interfacial interaction in SBR/HNTs-s-CZ nanocomposites. Consequently, SBR/HNTs-s-CZ nanocomposites showed excellent mechanical properties. The tensile strength could be enhanced by as much as 38.6% and 102.5% compared to those of SBR/m-HNTs and SBR/HNTs nanocomposites, respectively, though containing equivalent accelerant component. The value of this work lies in the fact that apparent properties improvement of elastomer composites has been achieved by the incorporation of vulcanization accelerant-functionalized HNTs, which may be fruitful for the rational design of filler surface treatment and offer new scientific and technological opportunities for the preparation of high performance elastomer composites.

  13. Surface modification of halloysite nanotubes by vulcanization accelerator and properties of styrene-butadiene rubber nanocomposites with modified halloysite nanotubes

    International Nuclear Information System (INIS)

    Zhong, Bangchao; Jia, Zhixin; Hu, Dechao; Luo, Yuanfang; Guo, Baochun; Jia, Demin

    2016-01-01

    Graphical abstract: - Highlights: • Vulcanization accelerant was used to modify halloysite nanotubes (HNTs). • The modified HNTs reduced the activation energy of vulcanization. • Strong filler–rubber interaction was achieved in rubber/modified HNTs composites. • The modified HNTs exhibited excellent reinforcement effect on rubber. - Abstract: Vulcanization accelerant N-cyclohexyl-2-benzothiazole sulfenamide (CZ) was used as a surface modifier and chemically grafted on the surface of halloysite nanotubes (HNTs) to obtain CZ-functionalized HNTs (HNTs-s-CZ). It was found that HNTs-s-CZ could be homogeneously dispersed into styrene-butadiene rubber (SBR). The grafted CZ molecules, exactly located at the filler-rubber interface, reduced the activation energy of vulcanization of SBR/HNTs-s-CZ compounds. Besides, the density of chain segments introduced by the interfacial phase of SBR/HNTs-s-CZ nanocomposites was higher than the other nanocomposites with silane-modified HNTs (m-HNTs) or pristine HNTs, manifesting an indication of enhanced filler-rubber interfacial interaction in SBR/HNTs-s-CZ nanocomposites. Consequently, SBR/HNTs-s-CZ nanocomposites showed excellent mechanical properties. The tensile strength could be enhanced by as much as 38.6% and 102.5% compared to those of SBR/m-HNTs and SBR/HNTs nanocomposites, respectively, though containing equivalent accelerant component. The value of this work lies in the fact that apparent properties improvement of elastomer composites has been achieved by the incorporation of vulcanization accelerant-functionalized HNTs, which may be fruitful for the rational design of filler surface treatment and offer new scientific and technological opportunities for the preparation of high performance elastomer composites.

  14. Anti-tumor response with immunologically modified carbon nanotubes and phototherapy

    Science.gov (United States)

    Acquaviva, Joseph T.; Zhou, Feifan; Boarman, Ellen; Chen, Wei R.

    2013-02-01

    While successes of different cancer therapies have been achieved in various degrees a systemic immune response is needed to effectively treat late-stage, metastatic cancers, and to establish long-term tumor resistance in the patients. A novel method for combating metastatic cancers has been developed using immunologically modified carbon nanotubes in conjunction with phototherapy. Glycated chitosan (GC) is a potent immunological adjuvant capable of increasing host immune responses, including antigen presentation by activation of dendritic cells (DCs) and causing T cell proliferation. GC is also an effective surfactant for nanomaterials. By combining single-walled carbon nanotubes (SWNTs) and GC, immunologically modified carbon nanotubes (SWNT-GC) were constructed. The SWNT-GC suspension retains the enhanced light absorption properties in the near infrared (NIR) region and the ability to enter cells, which are characteristic of SWNTs. The SWNT-GC also retains the immunological properties of GC. Cellular SWNT-GC treatments increased macrophage activity, DC activation and T cell proliferation. When cellular SWNT-GC was irradiated with a laser of an appropriate wavelength, these immune activities could be enhanced. The combination of laser irradiation and SWNT-GC induced cellular toxicity in targeted tumor cells, leading to a systemic antitumor response. Immunologically modified carbon nanotubes in conjunction with phototherapy is a novel and promising method to produce a systemic immune response for the treatment of metastatic cancers.

  15. Voltammetric Determination of Acetaminophen in the Presence of Codeine and Ascorbic Acid at Layer-by-Layer MWCNT/Hydroquinone Sulfonic Acid-Overoxidized Polypyrrole Modified Glassy Carbon Electrode

    OpenAIRE

    Shahrokhian, Saeed; Saberi, Reyhaneh-Sadat

    2011-01-01

    A very sensitive electrochemical sensor constructed of a glassy carbon electrode modified with a layer-by-layer MWCNT/doped-overoxidized polypyrrole (oppy/MWCNT /GCE) was used for the determination of acetaminophen (AC) in the presence of codeine and ascorbic acid (AA). In comparison to the bare glassy carbon electrode, a considerable shift in the peak potential together with an increase in the peak current was observed for AC on the surface of oppy/MWCNT/GCE, which can be related to the enla...

  16. Electrochemical behavior and voltammetric determination of acetaminophen based on glassy carbon electrodes modified with poly(4-aminobenzoic acid)/electrochemically reduced graphene oxide composite films

    International Nuclear Information System (INIS)

    Zhu, Wencai; Huang, Hui; Gao, Xiaochun; Ma, Houyi

    2014-01-01

    Poly(4-aminobenzoic acid)/electrochemically reduced graphene oxide composite film modified glassy carbon electrodes (4-ABA/ERGO/GCEs) were fabricated by a two-step electrochemical method. The electrochemical behavior of acetaminophen at the modified electrode was investigated by means of cyclic voltammetry. The results indicated that 4-ABA/ERGO composite films possessed excellent electrocatalytic activity towards the oxidation of acetaminophen. The electrochemical reaction of acetaminophen at 4-ABA/ERGO/GCE is proved to be a surface-controlled process involving the same number of protons and electrons. The voltammetric determination of acetaminophen performed with the 4-ABA/ERGO modified electrode presents a good linearity in the range of 0.1–65 μM with a low detection limit of 0.01 μM (S/N = 3). In the case of using the 4-ABA/ERGO/GCE, acetaminophen and dopamine can be simultaneously determined without mutual interference. Furthermore, the 4-ABA/ERGO/GCE has good reproducibility and stability, and can be used to determine acetaminophen in tablets. - Highlights: • The 4-ABA/ERGO/GCE was fabricated by a two-step electrochemical method. • Electrochemical behavior of acetaminophen at the 4-ABA/ERGO/GCE was investigated. • The electrochemical sensor exhibited a low detection limit and good selectivity. • This sensor was applied to the detection of acetaminophen in commercial tablets

  17. Electrochemical behavior and voltammetric determination of acetaminophen based on glassy carbon electrodes modified with poly(4-aminobenzoic acid)/electrochemically reduced graphene oxide composite films

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Wencai [Key Laboratory for Colloid and Interface Chemistry of State Education Ministry, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China); School of Chemistry and Chemical Engineering, Qilu Normal University, Jinan 250013 (China); Huang, Hui; Gao, Xiaochun [Key Laboratory for Colloid and Interface Chemistry of State Education Ministry, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China); Ma, Houyi, E-mail: hyma@sdu.edu.cn [Key Laboratory for Colloid and Interface Chemistry of State Education Ministry, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China)

    2014-12-01

    Poly(4-aminobenzoic acid)/electrochemically reduced graphene oxide composite film modified glassy carbon electrodes (4-ABA/ERGO/GCEs) were fabricated by a two-step electrochemical method. The electrochemical behavior of acetaminophen at the modified electrode was investigated by means of cyclic voltammetry. The results indicated that 4-ABA/ERGO composite films possessed excellent electrocatalytic activity towards the oxidation of acetaminophen. The electrochemical reaction of acetaminophen at 4-ABA/ERGO/GCE is proved to be a surface-controlled process involving the same number of protons and electrons. The voltammetric determination of acetaminophen performed with the 4-ABA/ERGO modified electrode presents a good linearity in the range of 0.1–65 μM with a low detection limit of 0.01 μM (S/N = 3). In the case of using the 4-ABA/ERGO/GCE, acetaminophen and dopamine can be simultaneously determined without mutual interference. Furthermore, the 4-ABA/ERGO/GCE has good reproducibility and stability, and can be used to determine acetaminophen in tablets. - Highlights: • The 4-ABA/ERGO/GCE was fabricated by a two-step electrochemical method. • Electrochemical behavior of acetaminophen at the 4-ABA/ERGO/GCE was investigated. • The electrochemical sensor exhibited a low detection limit and good selectivity. • This sensor was applied to the detection of acetaminophen in commercial tablets.

  18. para-Sulfonatocalix[6]arene-modified silver nanoparticles electrodeposited on glassy carbon electrode: preparation and electrochemical sensing of methyl parathion.

    Science.gov (United States)

    Bian, Yinghui; Li, Chunya; Li, Haibing

    2010-05-15

    In this paper, a new electrochemical sensor, based on modified silver nanoparticles, was fabricated using one-step electrodeposition approach. The para-sulfonatocalix[6]arene-modified silver nanoparticles coated on glassy carbon electrode (pSC(6)-Ag NPs/GCE) was characterized by attenuated total reflection IR spectroscopy (ATR-IR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), etc. The pSC(6) as the host are highly efficient to capture organophosphates (OPs), which dramatically facilitates the enrichment of nitroaromatic OPs onto the electrochemical sensor surface. The combination of the host-guest supramolecular structure and the excellent electrochemical catalytic activities of the pSC(6)-Ag NPs/GCE provides a fast, simple, and sensitive electrochemical method for detecting nitroaromatic OPs. In this work, methyl parathion (MP) was used as a nitroaromatic OP model for testing the proposed sensor. In comparison with Ag NPs-modified electrode, the cathodic peak current of MP was amplified significantly. Differential pulse voltammetry was used for the simultaneous determination of MP. Under optimum conditions, the current increased linearly with the increasing concentration of MP in the range of 0.01-80microM, with a detection limit of 4.0nM (S/N=3). The fabrication reproducibility and stability of the sensor is better than that of enzyme-based electrodes. The possible underlying mechanism is discussed.

  19. Electrochemical behavior and voltammetric determination of acetaminophen based on glassy carbon electrodes modified with poly(4-aminobenzoic acid)/electrochemically reduced graphene oxide composite films.

    Science.gov (United States)

    Zhu, Wencai; Huang, Hui; Gao, Xiaochun; Ma, Houyi

    2014-12-01

    Poly(4-aminobenzoic acid)/electrochemically reduced graphene oxide composite film modified glassy carbon electrodes (4-ABA/ERGO/GCEs) were fabricated by a two-step electrochemical method. The electrochemical behavior of acetaminophen at the modified electrode was investigated by means of cyclic voltammetry. The results indicated that 4-ABA/ERGO composite films possessed excellent electrocatalytic activity towards the oxidation of acetaminophen. The electrochemical reaction of acetaminophen at 4-ABA/ERGO/GCE is proved to be a surface-controlled process involving the same number of protons and electrons. The voltammetric determination of acetaminophen performed with the 4-ABA/ERGO modified electrode presents a good linearity in the range of 0.1-65 μM with a low detection limit of 0.01 μM (S/N=3). In the case of using the 4-ABA/ERGO/GCE, acetaminophen and dopamine can be simultaneously determined without mutual interference. Furthermore, the 4-ABA/ERGO/GCE has good reproducibility and stability, and can be used to determine acetaminophen in tablets. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. Differential pulse voltammetric determination of salbutamol sulfate in syrup pharmaceutical formulation using poly(4-amino-3-hydroxynaphthalene sulfonic acid modified glassy carbon electrode

    Directory of Open Access Journals (Sweden)

    Meareg Amare

    2017-10-01

    Full Text Available A new method for determination of salbutamol sulfate has been developed using poly(4-amino-3-hydroxynaphthalene sulfonic acid/GCE. Cyclic voltammetric investigation of the electrochemical behavior of salbutamol sulfate at the polymer modified glassy carbon unveiled electrocatalytic activity of the modifier towards irreversible oxidation of salbutamol sulfate. Dependence of peak current predominantly on scan rate than on square root of scan rate, and peak potential shift with pH demonstrated that oxidation of salbutamol sulfate at the polymer modified electrode follows adsorption reaction kinetics with proton participation.Under optimized solution and differential pulse voltammetric parameters, the oxidative peak current showed linear dependence on salbutamol sulfate concentration in the range 0.2 to 8 μM with method detection limit (3s/m and determination coefficient (R2 of 6.8 × 10−8 M and 0.99786, respectively. Low method detection limit, relatively wide linear range, and recovery results of spiked standard salbutamol sulfate in syrup samples in the range 96.7–98.9% validated the method for determination of salbutamol sulfate in pharmaceutical formulations.Differential pulse voltammetric analysis of salbutamol sulfate syrup formulation for its salbutamol sulfate content revealed 98.8 to 99.3% of the labeled value confirming the applicability of the developed method for determination of salbutamol sulfate in real samples. Keywords: Electrochemistry, Analytical chemistry

  1. Differential pulse voltammetric determination of methyl parathion based on multiwalled carbon nanotubes-poly(acrylamide) nanocomposite film modified electrode

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Yanbo [Department of Chemistry and Shanghai Key Laboratory of Green Chemistry and Chemical Process, East China Normal University, 3663 Zhongshan Road(N), Shanghai, 200062 (China); College of Biological, Chemical Sciences and Engineering, Jiaxing University, Jiaxing 314001 (China); Yu, Dajun; Yu, Yanyan [Department of Chemistry and Shanghai Key Laboratory of Green Chemistry and Chemical Process, East China Normal University, 3663 Zhongshan Road(N), Shanghai, 200062 (China); Zhou, Tianshu [Department of Environmental Science, East China Normal University, 3663 Zhongshan Road(N), Shanghai, 200062 (China); Shi, Guoyue, E-mail: gyshi@chem.ecnu.edu.cn [Department of Chemistry and Shanghai Key Laboratory of Green Chemistry and Chemical Process, East China Normal University, 3663 Zhongshan Road(N), Shanghai, 200062 (China)

    2012-05-30

    Highlights: Black-Right-Pointing-Pointer A sensitive electrochemical sensor for detecting methyl parathion in environmental samples. Black-Right-Pointing-Pointer The preparation, characterization and application of this novel MWCNTs-PAAM nanocomposite. Black-Right-Pointing-Pointer The MWCNTs-PAAM/GCE exhibited a high adsorption and strong affinity toward methyl parathion. Black-Right-Pointing-Pointer Wide linear range and low detection limit of the proposed method for detecting methyl parathion. - Abstract: A sensitive electrochemical differential pulse voltammetry method was developed for detecting methyl parathion based on multiwalled carbon nanotubes-poly(acrylamide) (MWCNTs-PAAM) nanocomposite film modified glassy carbon electrode. The novel MWCNTs-PAAM nanocomposite, containing high content of amide groups, was synthesized by PAAM polymerizing at the vinyl group functionalized MWCNTs surface using free radical polymerization. The MWCNTs-PAAM nanocomposite was characterized by Fourier transform infrared spectroscopy, thermal gravimetric analysis and scanning electron microscopy. Electrochemical behavior and interference studies of MWCNTs-PAAM/GCE for methyl parathion were investigated. The experimental results demonstrated that the MWCNTs-PAAM/GCE exhibited a high adsorption and strong affinity toward methyl parathion compared with some metal ions and nitroaromatic compounds, which exist in environmental samples. The adsorbed amount of methyl parathion on the MWCNTs-PAAM/GCE approached the equilibrium value upon 5 min adsorption time. A linear calibration curve for methyl parathion was obtained in the concentration range from 5.0 Multiplication-Sign 10{sup -9} to 1.0 Multiplication-Sign 10{sup -5} mol L{sup -1}, with a detection limit of 2.0 Multiplication-Sign 10{sup -9} mol L{sup -1}. The MWCNTs-PAAM/GCE was proved to be a suitable sensing tool for the fast, sensitive and selective determination of methyl parathion in environmental water samples.

  2. Glassy carbon electrode modified by conductive polyaniline coating for determination of trace lead and cadmium ions in acetate buffer solution

    International Nuclear Information System (INIS)

    Wang Zhaomeng; Liu Erjia; Zhao Xing

    2011-01-01

    Polyaniline (PANI) coatings were electrodeposited on the surfaces of glassy carbon electrodes (GCEs) to form new electrodes, i.e. PANI/GCEs. It was found that with increased deposition time, the PANI coatings became more compact while the charge transfer resistance of the coatings became higher. The PANI/GCEs were used to detect Cd 2+ and Pb 2+ ions contained in 0.1 M acetate buffer solutions using square wave anodic stripping voltammetry (SWASV). It was found that the PANI/GCE had a highest anodic stripping peak current in a solution of pH 5.3. The study of the cleaning performance of the PANI/GCEs indicated that there were less remaining metals on the surfaces of the PANI/GCEs compared to the bare GCEs after cleaning at a potential of 0.4 V, which was probably due to that the PANI coatings could effectively prevent the deposition of the metals into the surface defects of the GCEs. The PANI coatings could also reduce the passivation effect of the GCEs, thus improving the repeatability of the electrodes.

  3. Polyaniline Langmuir-Blodgett film modified glassy carbon electrode as a voltammetric sensor for determination of Ag+ ions

    International Nuclear Information System (INIS)

    Liu Qiongyan; Wang Fei; Qiao Yonghui; Zhang Shusheng; Ye Baoxian

    2010-01-01

    A highly sensitive electrochemical sensor made of a glassy carbon electrode (GCE) coated with a Langmuir-Blodgett film (LB) containing polyaniline (PAn) doped with p-toluenesulfonic acid (PTSA) (LB/PAn-PTSA/GCE) has been used for the detection of trace concentrations of Ag + . UV-vis absorption spectra indicated that the PAn was doped by PTSA. The surface morphology of the PAn LB film was characterized by atomic force microscopy (AFM). The electrochemical properties of this LB/PAn-PTSA/GCE were studied using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. The LB/PAn-PTSA/GCE was used as a voltammetric sensor for determination of trace Ag + at pH 5.0 using linear scanning stripping voltammetry. Under the optimal experimental conditions, the stripping current was proportional to the Ag + concentration over the range from 6.0 x 10 -10 mol L -1 to 1.0 x 10 -6 mol L -1 , with a detection limit of 4.0 x 10 -10 mol L -1 . The high sensitivity, selectivity, and stability of this LB/PAn-PTSA/GCE also demonstrated its practical utility for simple, rapid and economical determination of Ag + in water samples.

  4. Amperometric detection of carbohydrates based on the glassy carbon electrode modified with gold nano-flake layer

    Directory of Open Access Journals (Sweden)

    Huy Du Nguyen

    2015-09-01

    Full Text Available An electro-deposition approach was established to incorporate the gold nano-flakes onto the glassy carbon electrode in electrochemical cells (nano-Au/GC/ECCs. Using pulsed amperometric detection (PAD without any gold oxidation for cleaning (non-oxidative PAD, the nano-Au/GC/ECCs were able to maintain their activity for oxidizing of carbohydrates in a normal alkaline medium. The reproducibility of peak area was about 2 relative standard deviation (RSD,% for 6 consecutive injections. A dynamic range of carbohydrates was obtained over a concentration range of 5–80 mg L−1 and the limits of detection (LOD were of 2 mg L−1 for fructose and lactose and 1 mg L−1 for glucose and galactose. Moreover, the nano-Au/GC/ECC using the non-oxidative PAD was able to combine with the internal standard method for determination of lactose in fresh cow milk sample.

  5. Plasmonic gold nanoparticles modified titania nanotubes for antibacterial application

    International Nuclear Information System (INIS)

    Li, Jinhua; Zhou, Huaijuan; Qian, Shi; Liu, Ziwei; Feng, Jingwei; Jin, Ping; Liu, Xuanyong

    2014-01-01

    Close-packed TiO 2 nanotube arrays are prepared on metallic Ti surface by electrochemical anodization. Subsequently, by magnetron sputtering, Au nanoparticles are coated onto the top sidewall and tube inwall. The Au@TiO 2 systems can effectively kill Staphylococcus aureus and Escherichia coli in darkness due to the existence of Au nanoparticles. On the basis of classical optical theories, the antibacterial mechanism is proposed from the perspective of localized surface plasmon resonance. Respiratory electrons of bacterial membrane transfer to Au nanoparticles and then to TiO 2 , which makes bacteria steadily lose electrons until death. This work provides insights for the better understanding and designing of noble metal nanoparticles-based plasmonic heterostructures for antibacterial application.

  6. Electron transfer study on graphene modified glassy carbon substrate via electrochemical reduction and the application for tris(2,2'-bipyridyl)ruthenium(II) electrochemiluminescence sensor fabrication.

    Science.gov (United States)

    Xu, Yuanhong; Cao, Mengmei; Liu, Huihui; Zong, Xidan; Kong, Na; Zhang, Jizhen; Liu, Jingquan

    2015-07-01

    In this study, electron transfer behavior of the graphene nanosheets attachment on glassy carbon electrode (GCE) via direct electrochemical reduction of graphene oxide (GO) is investigated for the first time. The graphene modified electrode was achieved by simply dipping the GCE in GO suspension, followed by cyclic voltammetric scanning in the potential window from 0V to -1.5V. Tris(2,2'-bipyridyl)ruthenium(II) [Ru(bpy)3(2+)] was immobilized on the graphene modified electrode and used as the redox probe to evaluate the electron transfer behavior. The electron transfer rate constant (Ks) was calculated to be 61.9±5.8s(-1), which is much faster than that of tiled graphene modified GCE (7.1±0.6s(-1)). The enhanced electron transfer property observed with the GCE modified by reductively deposited graphene is probably due to its standing configuration, which is beneficial to the electron transfer comparing with the tiled one. Because the abundant oxygen-containing groups are mainly located at the edges of GO, which should be much easier for the reduction to start from, the reduced GO should tend to stand on the electrode surface as evidenced by scanning electron microscopy analysis. In addition, due to the favored electron transfer and standing configuration, the Ru(bpy)3(2+) electrochemiluminescence sensor fabricated with standing graphene modified GCE provided much higher and more stable efficiency than that fabricated with tiled graphene. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Removal of Chromium (III from Water by Using Modified and Nonmodified Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Muataz Ali Atieh

    2010-01-01

    Full Text Available This study was carried out to evaluate the environmental application of modified and nonmodified carbon nanotubes through the experiment removal of chromium trivalent (III from water. The aim was to find the optimal condition of the chromium (III removal from water under different treatment conditions of pH, adsorbent dosage, contact time and agitation speed. Multi wall carbon nanotubes (MW-CNTs were characterized by field emission scanning electron microscopy (FE-SEM and transmission electron microscopy (TEM. The diameter of the carbon nanotubes produced varied from 20–40 nm with average diameter of 24 nm and 10 micrometer in length. Adsorption isotherms were used to model the adsorption behavior and to calculate the adsorption capacity of the absorbents. The results showed that, 18% of chromium (III removal was achieved using modified carbon nanotubes (M-CNTs at pH 7, 150 rpm, and 2 hours for a dosage of 150 mg of CNTs. The removal of Cr (III is mainly attributed to the affinity of chromium (III to the physical and chemical properties of the CNTs. The adsorption isotherms plots were well fitted with experimental data.

  8. Direct electron transfer and electrocatalysis of glucose oxidase immobilized on glassy carbon electrode modified with Nafion and mesoporous carbon FDU-15

    International Nuclear Information System (INIS)

    Wang Kunqi; Yang Hua; Zhu Lin; Ma Zhongsu; Xing Shenyang; Lv Qiang; Liao Jianhui; Liu Changpeng; Xing Wei

    2009-01-01

    In this paper, it was found that glucose oxidase (GOD) has been stably immobilized on glassy carbon electrode modified with mesoporous carbon FDU-15 (MC-FDU-15) and Nafion by simple technique. The sorption behavior of GOD immobilized on MC-FDU-15 matrix was characterized by transmission electron microscopy (TEM), ultraviolet-visible (UV-vis), FTIR, respectively, which demonstrated that MC-FDU-15 could facilitate the electron exchange between the active center of GOD and electrode. The direct electrochemistry and electrocatalysis behavior of GOD on the modified electrode were characterized by cyclic voltammogram (CV) which indicated that GOD immobilized on Nafion and MC-FDU-15 matrices display direct, reversible and surface-controlled redox reaction with an enhanced electron transfer rate constant of 4.095 s -1 in 0.1 M phosphate buffer solution (PBS) (pH 7.12). Furthermore, it was also discovered that, in the presence of O 2 , GOD immobilized on Nafion and MC-FDU-15 matrices could produce a linear response to glucose. Thus, Nafion/GOD-MC-FDU-15/GC electrode is hopeful to be used in glucose biosensor. In addition, GOD immobilized on MC-FDU-15 and Nafion matrices possesses an excellent bioelectrocatalytic activity for the reduction of O 2 . So, the Nafion/GOD-MC-FDU-15/GC electrode can be utilized as the cathode in biofuel cell.

  9. Anodic stripping voltammetric determination of traces of Pb(II) and Cd(II) using a glassy carbon electrode modified with bismuth nanoparticles

    International Nuclear Information System (INIS)

    Yang, Die; Wang, Liang; Chen, Zuliang; Megharaj, Mallavarapu; Naidu, Ravi

    2014-01-01

    We report on a glassy carbon electrode modified with bismuth nanoparticles (NanoBiE) for the simultaneous determination Pb 2+ and Cd 2+ by anodic stripping voltammetry. Operational parameters such as bismuth nanoparticles labelling amount, deposition potential, deposition time and stripping parameters were optimized with respect to the determination of Pb 2+ and Cd 2+ in 0.1 M acetate buffer solution (pH 4.5). The NanoBiE gives well-defined, reproducible and sharp stripping peaks. The peak current response increases linearly with the metal concentration in a range of 5.0–60.0 μg L −1 , with a detection limit of 0.8 and 0.4 μg L −1 for Pb 2+ and Cd 2+ , respectively. The morphology and composition of the modified electrode before and after voltammetric measurements were analysed by scanning electron microscopy and energy dispersive X-ray analysis. The NanoBiE was successfully applied to analysis of Pb 2+ and Cd 2+ in real water samples and the method was validated by ICP-MS technique, suggesting that the electrode can be considered as an interesting alternative to the bismuth film electrode for possible use in electrochemical studies and electro analysis. (author)

  10. Very sensitive electrochemical determination of diuron on glassy carbon electrode modified with reduced graphene oxide-gold nanoparticle-Nafion composite film.

    Science.gov (United States)

    Zarei, K; Khodadadi, A

    2017-10-01

    In this work, a very sensitive electrochemical sensor based on glassy carbon electrode (GCE) modified with reduced graphene oxide-gold nanoparticles/Nafion (rGO-AuNPs/Nafion) composite film was applied to determine diuron. Synthesized GO was characterized using X-ray diffraction (XRD) and UV-visible spectroscopy. The surface morphology of the rGO-AuNPs/Nafion film was also characterized using scanning electron microscopy and electrochemical impedance spectroscopy. Cyclic voltammetry (CV) and adsorptive differential pulse voltammetry (AdDPV) were applied to investigate the electrochemical response of the diuron on the modified electrode. The electrode showed a linear response at 1.0×10 -9 -1.0×10 -7 M and a detection limit of 0.3nM under the optimized conditions. The effect of some other species on the determination of diuron was investigated and the sensor showed good selectivity for determination of diuron. The constructed sensor was applied to determine diuron in enriched samples of orange juice, mineral and tap water which statistical t-test showed accuracy of method. Also the sensor was applied to obtain diuron content in the tea sample. The reliability of the proposed sensor was confirmed after comparing the results with those obtained using high performance liquid chromatography (HPLC) as a comparative method. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. Electrocatalytic simultaneous determination of ascorbic acid, uric acid and L-Cysteine in real samples using quercetin silver nanoparticles-graphene nanosheets modified glassy carbon electrode

    Science.gov (United States)

    Zare, Hamid R.; Jahangiri-Dehaghani, Fahime; Shekari, Zahra; Benvidi, Ali

    2016-07-01

    By immobilizing of quercetin at the surface of a glassy carbon electrode modified with silver nanoparticles and graphene nanosheets (Q-AgNPs-GNs-GCE) a new sensor has been fabricated. The cyclic voltammogram of Q-AgNPs-GNs-GCE shows a stable redox couple with surface confined characteristics. Q-AgNPs-GNs-GCE demonstrated a high catalytic activity for L-Cysteine (L-Cys) oxidation. Results indicated that L-Cys peak potential at Q-AgNPs-GNs-GCE shifted to less positive values compared to GNs-GCE or AgNPs-GCE. Also, the kinetic parameters such as the electron transfer coefficient,, and the heterogeneous electron transfer rate constant, k‧, for the oxidation of L-Cys at the Q-AgNPs-GNs-GCE surface were estimated. In differential pulse voltammetric determination, the detection limit of L-Cys was obtained 0.28 μM, and the calibration plots were linear within two ranges of 0.9-12.4 μM and 12.4-538.5 μM of L-Cys. Also, the proposed modified electrode is used for the simultaneous determinations of ascorbic acid (AA), uric acid (UA), and L-Cys. Finally, this study has demonstrated the practical analytical utility of the sensor for determination of AA in vitamin C tablet, L-Cys in a milk sample and UA in a human urine sample.

  12. Electrochemical sensor for the determination of thiourea using a glassy carbon electrode modified with a self-assembled monolayer of an oxadiazole derivative and with silver nanoparticles

    International Nuclear Information System (INIS)

    Moghadam, Masoud Rohani; Akbarzadeh, Sanaz; Nasirizadeh, Navid

    2016-01-01

    This article reports on an electrochemical sensor for thiourea. It is based on a glassy carbon electrode (GCE) modified with a self-assembled monolayer of an oxadiazole derivative and with silver nanoparticles. The modified GCE demonstrated highly catalytic activity in terms of thiourea oxidation. The peak potential is shifted to negative values compared to a GCE coated with silver nanoparticles only. The electrode was characterized by linear sweep voltametry, cyclic voltammetry and chronoamperometry, and thiourea was determined by differential pulse voltammetry in aqueous buffer of pH 7.0 resulting in two linear response ranges of 0.001 − 69.4 and 69.4 − 833.3 μM and the limit of detection of 0.1 nM. The method was applied to the determination of thiourea in copper refinery electrolyte, orange juice and tap water samples. The recoveries ranged from 96.9 to 108.0 %. (author)

  13. Cyclovoltammetric acetylcholinesterase activity assay after inhibition and subsequent reactivation by using a glassy carbon electrode modified with palladium nanorods composited with functionalized C60 fullerene

    International Nuclear Information System (INIS)

    Ye, Cui; Zhong, Xia; Chai, Yaqin; Yuan, Ruo; Wang, Min-Qiang

    2016-01-01

    A glassy carbon electrode (GCE) was modified with a nanocomposite consisting of tetraoctylammonium bromide (TOAB), C 60 fullerene, and palladium nanorods (PdNRs). The PdNRs were hydrothermally prepared and had a typical width of 20 ± 2 nm. The nanocomposite forms stable films on the GCE and exhibits a reversible redox pair for the C 60 /C 60 − system while rendering the surface to be positively charged. The modified GCE was applied to fabricate an electrochemical biosensor for detecting acetylcholinesterase (AChE) by measurement of the amount of thiocholine formed from acetylthiocholine, best at a working voltage of −0.19 V (vs. SCE). The detection scheme is based on (a) measurement of the activity of ethyl paraoxon-inhibited AChE, and (b) measurement of AChE activity after reactivation with pralidoxime (2-PAM). Compared to the conventional methods using acetylthiocholine as a substrate, the dual method presented here provides data on the AChE activity after inhibition and subsequent reactivation, thereby yielding credible data on reactivated enzyme activity. The linear analytical range for AChE activity extends from 2.5 U L −1 to 250 kU·L −1 , and the detection limit is 0.83 U L −1 . (author)

  14. Voltammetric determination of total dissolved iron in coastal waters using a glassy carbon electrode modified with reduced graphene oxide, Methylene Blue and gold nanoparticles

    International Nuclear Information System (INIS)

    Lin, Mingyue; Zhang, Haiyun; Han, Haitao; Pan, Dawei; Su, Zhencui

    2015-01-01

    A nanocomposite, prepared from reduced graphene oxide (rGO), Methylene Blue (MB) and gold nanoparticles (AuNPs), was used to modify a glassy carbon electrode for the determination of total dissolved iron by differential pulse voltammetry. The use of rGO warrants a larger electrode surface and the presence of more active sites, while electron transfer is accelerated by incorporating AuNPs. MB acts as an electron mediator, as an anchor for the AuNPs (which were grown in situ), and also prevents the aggregation of rGO. The modified electrode displayed a remarkably improved sensitivity and selectivity for Fe(III). The kinetics of the electrode reaction is adsorption-controlled, and the reversible process involves one proton and one electron. The response to Fe(III) is linear in the 0.3 to 100 μM concentration range, and the detection limit is 15 nM. Possible interferences by other ions were studied. The electrode was successfully applied to the determination of total dissolved iron in real coastal waters. (author)

  15. Synthesis and characterization of manganese diselenide nanoparticles (MnSeNPs): Determination of capsaicin by using MnSeNP-modified glassy carbon electrode.

    Science.gov (United States)

    Sukanya, Ramaraj; Sakthivel, Mani; Chen, Shen-Ming; Chen, Tse-Wei; Al-Hemaid, Fahad M A; Ajmal Ali, M; Elshikh, Mohamed Soliman

    2018-06-02

    A new type of manganese diselenide nanoparticles (MnSeNPs) was synthesized by using a hydrothermal method. Their surface morphology, crystallinity and elemental distribution were characterized by using transmission electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy which scrutinize the formation of the NPs. The NPs were coated on a glassy carbon electrode (GCE), and electrochemical impedance spectroscopy, cyclic voltammetry and differential pulse voltammetry were applied to study the electroanalytical properties towards the oxidation of the food additive capsaicin. The modified GCE displays lower charge transfer resistance (R ct  = 29.52 Ω), a larger active surface area (0.089 cm 2 /g, and more efficient electrochemical oxidation of capsaicin compared to a MnS 2 /GCE and a bare GCE. The oxidation peak potential is 0.43 V (vs. Ag/AgCl) which is lower than that of previously reported GCEs. The sensor has a detection limit as low as 0.05 μM and an electrochemical sensitivity of 2.41 μA μM -1  cm -2 . The method was applied to the determination of capsaicin in pepper samples. Graphical abstract Electrochemical determination of capsaicin in pepper extract by using MnSeNPs modified electrode.

  16. Voltammetric determination of nitric oxide using a glassy carbon electrode modified with a nanohybrid consisting of myoglobin, gold nanorods, and reduced graphene oxide

    International Nuclear Information System (INIS)

    Marlinda, Ab Rahman; Jayabal, Subramaniam; Yusoff, Norazriena; Huang, Nay Ming; Pandikumar, Alagarsamy; Suriani, Abu Bakar

    2016-01-01

    Myoglobin-modified gold nanorods incorporating reduced graphene oxide (rGO) were fabricated and deposited on a glassy carbon electrode (GCE) to obtain a sensor for nitric oxide (NO). The Mb-AuNR/rGO nanohybrid showed a transverse localized surface plasmon resonance (LSPR) band with a peak at 508 nm, and a longitudinal LSPR band at 724 nm. The AuNRs have an average length of 38 ± 3 nm and a width of 11 ± 1 nm. The GCE modified with the nanohybrid is shown to be a viable sensor for the determination of NO by linear sweep voltammetry. Its electrocatalytic response toward the oxidation of NO is distinctly enhanced compared to other electrodes. The sensor, best operated at a working voltage of 0.85 V (vs. SCE), showed two linear response ranges (from 10 to 100 μM, and from 100 to 1000 μM), with a detection limit of 5.5 μM. Furthermore, it exhibits excellent selectivity for NO over common interferents such as NaNO 3 , and also over electroactive species such as ascorbate, dopamine, glucose, and uric acid. These properties make it a promising tool for the detection of NO in situations such as capillary and pulmonary hypertension and embolism, and during vasodilation. (author)

  17. Hydrogen peroxide biosensor based on hemoglobin immobilized at graphene, flower-like zinc oxide, and gold nanoparticles nanocomposite modified glassy carbon electrode.

    Science.gov (United States)

    Xie, Lingling; Xu, Yuandong; Cao, Xiaoyu

    2013-07-01

    In this work, a highly sensitive hydrogen peroxide (H2O2) biosensor based on immobilization of hemoglobin (Hb) at Au nanoparticles (AuNPs)/flower-like zinc oxide/graphene (AuNPs/ZnO/Gr) composite modified glassy carbon electrode (GCE) was constructed, where ZnO and Au nanoparticles were modified through layer-by-layer onto Gr/GCE. Flower-like ZnO nanoparticles could be easily prepared by adding ethanol to the precursor solution having higher concentration of hydroxide ions. The Hb/AuNPs/ZnO/Gr composite film showed a pair of well-defined, quasi-reversible redox peaks with a formal potential (E(0)) of -0.367 V, characteristic features of heme redox couple of Hb. The electron transfer rate constant (k(s)) of immobilized Hb was 1.3 s(-1). The developed biosensor showed a very fast response (<2 s) toward H2O2 with good sensitivity, wide linear range, and low detection limit of 0.8 μM. The fabricated biosensor showed interesting features, including high selectivity, acceptable stability, good reproducibility, and repeatability along with excellent conductivity, facile electron mobility of Gr, and good biocompatibility of ZnO and AuNPs. The fabrication method of this biosensor was simple and effective for determination of H2O2 in real samples with quick response, good sensitivity, high selectivity, and acceptable recovery. Copyright © 2013 Elsevier B.V. All rights reserved.

  18. A glassy carbon electrode modified with a film composed of cobalt oxide nanoparticles and graphene for electrochemical sensing of H2O2

    International Nuclear Information System (INIS)

    Li, Su-Juan; Du, Ji-Min; Zhang, Jia-Ping; Zhang, Meng-Jie; Chen, Jing

    2014-01-01

    We have prepared a graphene-based hybrid nanomaterial by electrochemical deposition of cobalt oxide nanoparticles (CoOxNPs) on the surface of electrochemically reduced graphene oxide deposited on a glassy carbon electrode (GCE). Scanning electron microscopy and cyclic voltammetry were used to characterize the immobilized nanoparticles. Electrochemical determination of H 2 O 2 is demonstrated with the modified GCE at pH 7. Compared to GCEs modified with CoO x NPs or graphene sheets only, the new electrode displays larger oxidative current response to H 2 O 2 , probably due to the synergistic effects between the graphene sheets and the CoO x NPs. The sensor responds to H 2 O 2 with a sensitivity of 148.6 μA mM −1 cm −2 and a linear response range from 5 μM to 1 mM. The detection limit is 0.2 μM at a signal to noise ratio (SNR) of three. The method was successfully applied to the determination of H 2 O 2 in hydrogen peroxide samples. (author)

  19. Simultaneous determination of caffeine and paracetamol by square wave voltammetry at poly(4-amino-3-hydroxynaphthalene sulfonic acid)-modified glassy carbon electrode.

    Science.gov (United States)

    Tefera, Molla; Geto, Alemnew; Tessema, Merid; Admassie, Shimelis

    2016-11-01

    Poly(4-amino-3-hydroxynaphthalene sulfonic acid)-modified glassy carbon electrode (poly(AHNSA)/GCE) was prepared for simultaneous determination of caffeine and paracetamol using square-wave voltammetry. The method was used to study the effects of pH and scan rate on the voltammetric response of caffeine and paracetamol. Linear calibration curves in the range of 10-125μM were obtained for both caffeine and paracetamol in acetate buffer solution of pH 4.5 with a correlation coefficient of 0.9989 and 0.9986, respectively. The calculated detection limits (S/N=3) were 0.79μM for caffeine and 0.45μM for paracetamol. The effects of some interfering substances in the determination of caffeine and paracetamol were also studied and their interferences were found to be negligible which proved the selectivity of the modified electrode. The method was successfully applied for the quantitative determination of caffeine and paracetamol in Coca-Cola, Pepsi-Cola and tea samples. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. A non-enzymatic hydrogen peroxide sensor based on a glassy carbon electrode modified with cuprous oxide and nitrogen-doped graphene in a nafion matrix

    International Nuclear Information System (INIS)

    Jiang, Bin-Bin; Wei, Xian-Wen; Wu, Fang-Hui; Chen, Le; Yuan, Guo-Zan; Wu, Kong-Lin; Dong, Chao; Ye, Yin

    2014-01-01

    We have modified a glassy carbon electrode (GCE) with copper(I) oxide nanoparticles (NPs), nitrogen-doped graphene (N-graphene) and Nafion to obtain a novel sensing platform for the non-enzymatic detection of hydrogen peroxide. The deposition of the Cu 2 O NPs on N-graphene was accomplished by single-step chemical reduction. The nanocomposite was characterized by using X-ray diffraction and scanning electron microscopy which revealed the successful attachment of monodispersed Cu 2 O NPs to the N-graphene. Electrochemical studies revealed that the composite possesses excellent electrocatalytic activity toward the reduction of H 2 O 2 in pH 7.4 phosphate buffer solution at a working potential of −0.60 V. Nafion obviously enhances the stability of the modified GCE and repels any negatively charged species. Compared to a conventional Cu 2 O/Nafion-modified GCE, the modified GCE presented here exhibits (a) a higher catalytic activity for the reduction of H 2 O 2 (1.94 times), (b) a wider linear range (from 5.0 μM to 3.57 mM), (c) a lower detection limit (0.8 μM at an S/N of 3), (d) higher sensitivity (26.67 μA mM −1 ) and (e) a shorter response time (2 s). Moreover, the new GCE exhibits good selectivity and stability. These properties make the new hybrid electrode a promising tool for to the development of electrochemical sensors, molecular bioelectronic devices, biosensors, and biofuel cells. (author)

  1. A Glucose Sensor Based on Glucose Oxidase Immobilized by Electrospinning Nanofibrous Polymer Membranes Modified with Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    You Wang

    2013-05-01

    Full Text Available A glucose biosensor based on glucose oxidase immobilized by electrospinning nanofibrous membranes has been developed. Nanofibrous membranes were electrospun from the solution of poly(acrylonitrile-co-acrylic acid containing carbon nanotubes suspension and directly deposited on Pt electrodes for immobilizing glucose oxidase. The morphologies and structure of the nanofibrous membranes with or without carbon nanotubes were characterized by scanning electron microscopy. The fabrication parameters of nanofibers were optimized such as thickness of the nanofibrous membranes and mass ration of carbon nanotubes. The biosensor showed the relationship with a concentration range of 0.1–10 mM and response time was 60 s. The sensitivity of carbon nanotubes modified biosensors was two times larger than which of no carbon nanotubes modified ones. The pH effect, interference and lifetime of biosensors were discussed.

  2. Microstructure and mechanical performance of modified mortar using hemp fibres and carbon nanotubes

    KAUST Repository

    Hamzaoui, Rabah

    2014-04-01

    Mechanical performance of modified mortar using hemp fibres is studied following various processing conditions. Hemp fibres combined with carbon nanotubes (CNT) are introduced in mortar and their effect is studied as function of curing time. The cement phase is replaced by different percentages of dry or wet hemp fibres ranging from 1.1. wt% up to 3.1. wt% whereas carbon nanotubes are dispersed in the aqueous solution. Our experimental results show that compressive and flexural strengths of wet fibres modified mortar are higher than those for dry hemp-mortar material. The achieved optimal percentage of wet hemp fibres is 2.1. wt% allowing a flexural strength higher than that of reference mortar. The addition of an optimal CNT concentration (0.01. wt%) combined with wet hemp has a reinforcing effect which turns to be related to an improvement of compressive and flexural strengths by 10% and 24%, respectively, in comparison with reference condition. © 2013 Elsevier Ltd.

  3. Amperometric detection of hydrogen peroxide at nano-nickel oxide/thionine and celestine blue nanocomposite-modified glassy carbon electrodes

    International Nuclear Information System (INIS)

    Noorbakhsh, Abdollah; Salimi, Abdollah

    2009-01-01

    A simple procedure was developed to prepare a glassy carbon (GC) electrode modified with nickel oxide (NiOx) nanoparticles and water-soluble dyes. By immersing the GC/NiOx modified electrode into thionine (TH) or celestine blue (CB) solutions for a short period of time (5-120 s), a thin film of the proposed molecules was immobilized onto the electrode surface. The modified electrodes showed stable and a well-defined redox couples at a wide pH range (2-12), with surface confined characteristics. In comparison to usual methods for the immobilization of dye molecules, such as electropolymerization or adsorption on the surface of preanodized electrodes, the electrochemical reversibility and stability of these modified electrodes have been improved. The surface coverage and heterogeneous electron transfer rate constants (k s ) of thionin and celestin blue immobilized on a NiOx-GC electrode were approximately 3.5 x 10 -10 mol cm -2 , 6.12 s -1 , 5.9 x 10 -10 mol cm -2 and 6.58 s -1 , respectively. The results clearly show the high loading ability of the NiOx nanoparticles and great facilitation of the electron transfer between the immobilized TH, CB and NiOx nanoparticles. The modified electrodes show excellent electrocatalytic activity toward hydrogen peroxide reduction at a reduced overpotential. The catalytic rate constants for hydrogen peroxide reduction at GC/NiOx/CB and GC/NiOx/TH were 7.96 (±0.2) x 10 3 M -1 s -1 and 5.5 (±0.2) x 10 3 M -1 s -1 , respectively. The detection limit, sensitivity and linear concentration range for hydrogen peroxide detection were 1.67 μM, 4.14 nA μM -1 nA μM -1 and 5 μM to 20 mM, and 0.36 μM, 7.62 nA μM -1 , and 1 μM to 10 mM for the GC/NiOx/TH and GC/NiOx/CB modified electrodes, respectively. Compared to other modified electrodes, these modified electrodes have many advantages, such as remarkable catalytic activity, good reproducibility, simple preparation procedures and long-term stabilities of signal responses during

  4. Electronic properties of pristine and modified single-walled carbon nanotubes

    International Nuclear Information System (INIS)

    Kharlamova, M V

    2013-01-01

    The current status of research on the electronic properties of filled single-walled carbon nanotubes (SWCNTs) is reviewed. SWCNT atomic structure and electronic properties are described, and their correlation is discussed. Methods for modifying the electronic properties of SWCNTs are considered. SWCNT filling materials are systematized. Experimental and theoretical data on the electronic properties of filled SWCNTs are analyzed. Possible application areas for filled SWCNTs are explored. (reviews of topical problems)

  5. Electrochemical immunosensor for the determination of insulin-like growth factor-1 using electrodes modified with carbon nanotubes-poly(pyrrole propionic acid) hybrids.

    Science.gov (United States)

    Serafín, V; Agüí, L; Yáñez-Sedeño, P; Pingarrón, J M

    2014-02-15

    An amperometric immunosensor for the determination of the hormone insulin-like growth factor 1 (IGF1) is reported for the first time in this work. As electrochemical transducer, a multiwalled carbon nanotubes-modified glassy carbon electrode on which poly(pyrrole propionic acid) was electropolymerized was prepared. This approach provided a high content of surface confined carboxyl groups suitable for direct covalent binding of anti-IGF1 monoclonal antibody. A sandwich-type immunoassay using a polyclonal antibody labeled with peroxidase, hydrogen peroxide as the enzyme substrate and catechol as redox mediator was employed to monitor the affinity reaction. All the variables involved in the preparation of the modified electrode were optimized and the electrodes were characterized by electrochemical impedance spectroscopy and cyclic voltammetry. Moreover, the different experimental variables affecting the amperometric response of the immunosensor were also optimized. The calibration graph for IGF1 showed a range of linearity extending from 0.5 to 1000 pg/mL, with a detection limit, 0.25 pg/mL, more than 100 times lower than the lowest values reported for the ELISA immunoassays available for IGF1 (30 pg/mL, approximately). Excellent reproducibility for the measurements carried out with different immunosensors and selectivity against other hormones were also evidenced. A commercial human serum spiked with IGF1 at different levels between 0.01 and 10.0 ng/mL was analyzed with good results. © 2013 Elsevier B.V. All rights reserved.

  6. Carbon nanotubes and graphene modified screen-printed carbon electrodes as sensitive sensors for the determination of phytochelatins in plants using liquid chromatography with amperometric detection.

    Science.gov (United States)

    Dago, Àngela; Navarro, Javier; Ariño, Cristina; Díaz-Cruz, José Manuel; Esteban, Miquel

    2015-08-28

    Nanomaterials are of great interest for the development of electrochemical sensors. Multi-walled carbon nanotubes and graphene were used to modify the working electrode surface of different screen-printed carbon electrodes (SPCE) with the aim of improving the sensitivity of the SPCE and comparing it with the conventional glassy carbon electrode. To assay the usability of these sensors, a HPLC methodology with amperometric detection was developed to analyze several phytochelatins in plants of Hordeum vulgare and Glycine max treated with Hg(II) or Cd(II) giving detection limits in the low μmolL(-1) range. Phytochelatins are low molecular weight peptides with the general structure γ-(Glu-Cys)n-Gly (n=2-5) which are synthesized in plants in the presence of heavy metal ions. These compounds can chelate heavy metal ions by the formation of complexes which, are transported to the vacuoles, where the toxicity is not threatening. For this reason phytochelatins are essential in the detoxification of heavy metal ions in plants. The developed HPLC method uses a mobile phase of 1% of formic acid in water with KNO3 or NaCl (pH=2.00) and 1% of formic acid in acetonitrile. Electrochemical detection at different carbon-based electrodes was used. Among the sensors tested, the conventional glassy carbon electrode offers the best sensitivity although modification improves the sensitivity of the SPCE. Glutathione and several isoforms of phytochelatin two were found in plant extracts of both studied species. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. A novel sensitive Cu(II) and Cd(II) nanosensor platform: Graphene oxide terminated p-aminophenyl modified glassy carbon surface

    International Nuclear Information System (INIS)

    Gupta, Vinod Kumar; Yola, Mehmet Lütfi; Atar, Necip; Ustundag, Zafer; Solak, Ali Osman

    2013-01-01

    Graphical abstract: - Highlights: • We electrochemically prepared sensor based on graphene oxide. • The prepared electrode was characterized by using various techniques. • The proposed nanosensor showed good stability, selectivity and high sensitivity. • The proposed nanosensor electrode was used for the analysis of Cd(II) and Cu(II). - Abstract: Graphene oxide (GO) based glassy carbon (GC) electrode has been prepared. Firstly, p-nitrophenyl (NP) modified GC (NP/GC) electrode was prepared via the electrochemical reduction of its tetraflouroborate diazonium salt. After the formation of NP/GC electrode, the negative potential was applied to NP/GC electrode to reduce the nitro groups to amine. p-Aminophenyl (AP) modified GC (AP/GC) electrode was immersed into a graphene oxide solution containing 1-ethyl-3(3-(dimethlyamino)propyl)-carbodiimide. Hence, we constructed GO terminated AP modified GC (GO/AP/GC) electrode. NP/GC, AP/GC and GO/AP/GC electrodes were characterized sequentially using cyclic voltammetry (CV) in the presence of 1.0 mM of potassium ferricyanide in 0.1 M KCl. In addition, GO and GO/AP/GC surfaces were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The GO/AP/GC electrode was used for the analysis of Cd(II) and Cu(II) ions by adsorptive stripping voltammetry. The linearity range and the detection limit of Cd(II) and Cu(II) ions were 1.0 × 10 −11 –5.0 × 10 −10 M and 3.3 × 10 −12 M (S/N = 3), respectively

  8. Development of sensitive amperometric hydrogen peroxide sensor using a CuNPs/MB/MWCNT-C_6_0-Cs-IL nanocomposite modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Roushani, Mahmoud; Bakyas, Kobra; Zare Dizajdizi, Behruz

    2016-01-01

    A sensitive hydrogen peroxide (H_2O_2) sensor was constructed based on copper nanoparticles/methylene blue/multiwall carbon nanotubes–fullerene–chitosan–ionic liquid (CuNPs/MB/MWCNTs–C_6_0–Cs–IL) nanocomposites. The MB/MWCNTs–C_6_0–Cs–IL and CuNPs were modified glassy carbon electrode (GCE) by the physical adsorption and electrodeposition of copper nitrate solution, respectively. The physical morphology and chemical composition of the surface of modified electrode was investigated by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), respectively. The electrochemical properties of CuNPs/MB/MWCNTs–C_6_0–Cs–IL/GCE were investigated by cyclic voltammetry (CV) and amperometry techniques and the sensor exhibited remarkably strong electrocatalytic activities toward the reduction of hydrogen peroxide. The peak currents possess a linear relationship with the concentration of H_2O_2 in the range of 0.2 μM to 2.0 mM, and the detection limit is 55.0 nM (S/N = 3). In addition, the modified electrode was used to determine H_2O_2 concentration in human blood serum sample with satisfactory results. - Highlights: • CuNPs/MB/MWCNT-C_6_0-Cs-IL/GC electrode was constructed by layer-by-layer method. • The catalytic performance of the sensor was studied with the use of amperometric technique. • The constructed sensor showed enhanced electrocatalytic activity toward the reduction of H_2O_2. • The CuNPs/MB/MWCNT-C_6_0-Cs-IL/GC electrode demonstrated high stability for the detection of H_2O_2.

  9. Differential pulse voltammetric simultaneous determination of ascorbic acid, dopamine and uric acid on a glassy carbon electrode modified with electro reduced graphene oxide and imidazolium groups

    International Nuclear Information System (INIS)

    Wu, Feng; Huang, Ting; Xie, Qingji; Hu, Yangjian; Yang, Xin; Ouyang, Yuejun

    2016-01-01

    A glassy carbon electrode (GCE) was anodically oxidized by cyclic voltammetry (CV) in 0.05 M sulfuric acid to introduce hydroxy groups on its surface (GCE ox ). Next, an imidazolium alkoxy silane (ImAS) is covalently tethered to the surface of the GCE ox via silane chemistry. This electrode is further modified with graphene oxide (GO) which, dispersed in water, spontaneously assembles on the electrode surface through electrostatic interaction and π-interaction to give an electrode of type GO/ImAS/GCE. Electroreduction of GO and GCE ox by CV yields electro reduced GO (erGO) and an electrode of the type erGO/ImAS/GCE. This electrode displays excellent electrocatalytic activity for the oxidation of ascorbic acid (AA), dopamine (DA) and uric acid (UA). Three fully resolved anodic peaks (at −50 mV, 150 mV and 280 mV vs. Ag/AgCl) are observed during differential pulse voltammetry (DPV). Under optimized conditions, the linear detection ranges are from 30 to 2000 μM for AA, from 20 to 490 μM for UA, and from 0.1 to 5 μM and from 5 μM to 200 μM (two linear ranges) for DA. The respective limits of detection (for an S/N of 3) are 10 μM, 5 μM and 0.03 μM. The GCE modified with erGO and ImAS performs better than a bare GCE or a GCE modified with ImAS only, and also outperforms many other reported electrodes for the three analytes. The method was successfully applied to simultaneous analysis of AA, DA and UA in spiked human urine. (author)

  10. Development of sensitive amperometric hydrogen peroxide sensor using a CuNPs/MB/MWCNT-C{sub 60}-Cs-IL nanocomposite modified glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Roushani, Mahmoud, E-mail: mahmoudroushani@yahoo.com; Bakyas, Kobra; Zare Dizajdizi, Behruz

    2016-07-01

    A sensitive hydrogen peroxide (H{sub 2}O{sub 2}) sensor was constructed based on copper nanoparticles/methylene blue/multiwall carbon nanotubes–fullerene–chitosan–ionic liquid (CuNPs/MB/MWCNTs–C{sub 60}–Cs–IL) nanocomposites. The MB/MWCNTs–C{sub 60}–Cs–IL and CuNPs were modified glassy carbon electrode (GCE) by the physical adsorption and electrodeposition of copper nitrate solution, respectively. The physical morphology and chemical composition of the surface of modified electrode was investigated by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), respectively. The electrochemical properties of CuNPs/MB/MWCNTs–C{sub 60}–Cs–IL/GCE were investigated by cyclic voltammetry (CV) and amperometry techniques and the sensor exhibited remarkably strong electrocatalytic activities toward the reduction of hydrogen peroxide. The peak currents possess a linear relationship with the concentration of H{sub 2}O{sub 2} in the range of 0.2 μM to 2.0 mM, and the detection limit is 55.0 nM (S/N = 3). In addition, the modified electrode was used to determine H{sub 2}O{sub 2} concentration in human blood serum sample with satisfactory results. - Highlights: • CuNPs/MB/MWCNT-C{sub 60}-Cs-IL/GC electrode was constructed by layer-by-layer method. • The catalytic performance of the sensor was studied with the use of amperometric technique. • The constructed sensor showed enhanced electrocatalytic activity toward the reduction of H{sub 2}O{sub 2}. • The CuNPs/MB/MWCNT-C{sub 60}-Cs-IL/GC electrode demonstrated high stability for the detection of H{sub 2}O{sub 2}.

  11. Dispersing surface-modified imogolite nanotubes in polar and non-polar solvents

    Science.gov (United States)

    Li, Ming; Brant, Jonathan A.

    2018-02-01

    Furthering the development of nanocomposite structures, namely membranes for water treatment applications, requires that methods be developed to ensure nanoparticle dispersion in polar and non-polar solvents, as both are widely used in associated synthesis techniques. Here, we report on a two-step method to graft polyvinylpyrrolidone (PVP), and a one-step method for octadecylphosphonic acid (OPA), onto the outer surfaces of imogolite nanotubes. The goal of these approaches was to improve and maintain nanotube dispersion in polymer compatible polar and non-polar solvents. The PVP coating modified the imogolite surface charge from positive to weakly negative at pH ≤ 9; the OPA made it weakly positive at acidic pH values to negative at pH ≥ 7. The PVP surface coating stabilized the nanotubes through steric hindrance in polar protic, dipolar aprotic, and chloroform. In difference to the PVP, the OPA surface coating allowed the nanotubes to be dispersed in n-hexane and chloroform, but not in the polar solvents. The lack of miscibility in the polar solvents, as well as the better dispersion in n-hexane, was attributed to the stronger hydrophobicity of the OPA polymer relative to the PVP. [Figure not available: see fulltext.

  12. Investigation of bioresistant dry building mixes modified by carbon nanotubes

    OpenAIRE

    Korolev Evgeniy Valer'evich; Erofeev Vladimir Trofimovich; Suraeva Ekaterina Nikolaevna

    2015-01-01

    Dry construction mixes are today a product of high technologies. Depending on the purpose and requirements to the properties it is easy to produce dry construction mixes with different compositions and operating indicators in plant conditions using the necessary modifying additives. Cement, gypsum and other mineral binders are used in the construction mixes. Different types of cement are more heavily used in dry construction mixes. Such dry mixes are believed to be more effective materials co...

  13. Cobalt oxide nanoparticle-modified carbon nanotubes as an ...

    Indian Academy of Sciences (India)

    of 60 mV were observed at. 100 mV s. −1 for CoOx−MWNT/GCE. An anodic peak at. 100 mV attributed to Co(II)/Co(III) redox transition associated with the electrode surface. The cathodic peak at 20 mV corre- spond to the reduction of various cobalt oxide species formed during the anodic sweep. The stability of the modified ...

  14. A glucose biosensor based on direct electron transfer of glucose oxidase immobilized onto glassy carbon electrode modified with nitrophenyl diazonium salt

    International Nuclear Information System (INIS)

    Nasri, Zahra; Shams, Esmaeil

    2013-01-01

    Graphical abstract: - Abstract: This study reports a novel, simple and fast approach for construction of a highly stable glucose biosensor based on the immobilization of glucose oxidase (GOx) onto a glassy carbon electrode (GCE) electrografted with 4-aminophenyl (AP) by diazonium chemistry. Aminophenyl was used as cross-linker for covalent attachment of glucose oxidase to the electrode surface. Cyclic voltammograms of the GOx-modified GCE in phosphate buffer solution exhibited a pair of well-defined redox peaks, attesting the direct electron transfer (DET) of GOx with the underlying electrode. The proposed biosensor could be used to detect glucose based on the consumption of O 2 with the oxidation of glucose catalyzed by GOx and exhibited a wide linear range of glucose from 0.05 mM to 4.5 mM and low detection limit of 10 μM. The surface coverage of active GOx, heterogeneous electron transfer rate constant (k s ) and Michaelis–Menten constant (K M ) of immobilized GOx were 1.23 × 10 −12 mol cm −2 , 4.25 s −1 and 2.95 mM, respectively. The great stability of this biosensor, technically simple and possibility of preparation at short period of time make this method suitable for fabrication of low-cost glucose biosensors

  15. Determination of Silver(I by Differential Pulse Voltammetry Using a Glassy Carbon Electrode Modified with Synthesized N-(2-Aminoethyl-4,4'-Bipyridine

    Directory of Open Access Journals (Sweden)

    Gabriel Lucian Radu

    2010-12-01

    Full Text Available A new modified glassy carbon electrode (GCE based on a synthesized N-(2-aminoethyl-4,4'-bipyridine (ABP was developed for the determination of Ag(I by differential pulse voltammetry (DPV. ABP was covalently immobilized on GC electrodes surface using 4-nitrobenzendiazonium (4-NBD and glutaraldehyde (GA. The Ag(I ions were preconcentrated by chemical interaction with bipyridine under a negative potential (−0.6 V; then the reduced ions were oxidized by differential pulse voltammetry and a peak was observed at 0.34 V. The calibration curve was linear in the concentration range from 0.05 μM to 1 μM Ag(I with a detection limit of 0.025 μM and RSD = 3.6%, for 0.4 μM Ag(I. The presence of several common ions in more than 125-fold excess had no effect on the determination of Ag(I. The developed sensor was applied to the determination of Ag(I in water samples using a standard addition method.

  16. Glassy carbon electrode modified with gold nanoparticles and hemoglobin in a chitosan matrix for improved pH-switchable sensing of hydrogen peroxide

    International Nuclear Information System (INIS)

    Liu, Yang; Shi, Liang; Gong, Jin; Fang, Yu-Ting; Bao, Ning; Gu, Hai-Ying; Zeng, Jiang

    2015-01-01

    Hemoglobin (Hb) has been demonstrated to endow electrochemical sensors with pH-switchable response because of the presence of carboxyl and amino groups. Hb was deposited in a chitosan matrix on a glassy carbon electrode (GCE) that was previously coated with clustered gold nanoparticles (Au-NPs) by electrodeposition. The switching behavior is active (“on”) to the negatively charged probe [Fe(CN) 6 3− ] at pH 4.0, but inactive (“off”) to the probe at pH 8.0. This switch is fully reversible by simply changing the pH value of the solution and can be applied for pH-controlled reversible electrochemical reduction of H 2 O 2 catalyzed by Hb. The modified electrode was tested for its response to the different electroactive probes. The response to these species strongly depends on pH which was cycled between 4 and 8. The effect is also attributed to the presence of pH dependent charges on the surface of the electrode which resulted in either electrostatic attraction or repulsion of the electroactive probes. The presence of Hb, in turn, enhances the pH-controllable response, and the electrodeposited Au-NPs improve the capability of switching. This study reveals the potential of protein based pH-switchable materials and also provides a simple and effective strategy for fabrication of switchable chemical sensors as exemplified in a pH-controllable electrode for hydrogen peroxide. (author)

  17. Electrocatalytic oxidation behavior of NADH at Pt/Fe{sub 3}O{sub 4}/reduced-graphene oxide nanohybrids modified glassy carbon electrode and its determination

    Energy Technology Data Exchange (ETDEWEB)

    Roushani, Mahmoud, E-mail: mahmoudroushani@yahoo.com [Department of Chemistry, Faculty of Sciences, Ilam University, Ilam, 69315516 (Iran, Islamic Republic of); Hoseini, S. Jafar [Department of Chemistry, Faculty of Sciences, Yasouj University, Yasouj, 7591874831 (Iran, Islamic Republic of); Azadpour, Mitra [Department of Chemistry, Faculty of Sciences, Ilam University, Ilam, 69315516 (Iran, Islamic Republic of); Heidari, Vahid; Bahrami, Mehrangiz; Maddahfar, Mahnaz [Department of Chemistry, Faculty of Sciences, Yasouj University, Yasouj, 7591874831 (Iran, Islamic Republic of)

    2016-10-01

    We have developed Pt/Fe{sub 3}O{sub 4}/reduced-graphene oxide nanohybrids modified glassy carbon (Pt/Fe{sub 3}O{sub 4}/RGO/GC) electrode as a novel system for the preparation of electrochemical sensing platform. Characterization of as-made composite was determined using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM) and energy-dispersive analysis of X-ray (EDAX) where the Pt, Fe, Si, O and C elements were observed. The Pt/Fe{sub 3}O{sub 4}/RGO/GC electrode was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Due to the synergistic effect between Pt, Fe{sub 3}O{sub 4} and RGO, the nanohybrid exhibited excellent performance toward dihydronicotinamide adenine dinucleotide (NADH) oxidation in 0.1 M phosphate buffer solution, pH 7.0, with a low detection limit of 5 nM. - Highlights: • Preparation of a novel electrochemical sensing platform system • Excellent performance of Pt/Fe{sub 3}O{sub 4}/reduced-graphene oxide nanohybrids • Dihydronicotinamide adenine dinucleotide oxidation with a low detection limit of 5 nM.

  18. Dopamine and uric acid electrochemical sensor based on a glassy carbon electrode modified with cubic Pd and reduced graphene oxide nanocomposite.

    Science.gov (United States)

    Wang, Jin; Yang, Beibei; Zhong, Jiatai; Yan, Bo; Zhang, Ke; Zhai, Chunyang; Shiraishi, Yukihide; Du, Yukou; Yang, Ping

    2017-07-01

    A cubic Pd and reduced graphene oxide modified glassy carbon electrode (Pd/RGO/GCE) was fabricated to simultaneously detect dopamine (DA) and uric acid (UA) by cyclic voltammetry (CV) and different pulse voltammetry (DPV) methods. Compared with Pd/GCE and RGO/GCE, the Pd/RGO/GCE exhibited excellent electrochemical activity in electrocatalytic behaviors. Performing the Pd/RGO/GCE in CV measurement, the well-defined oxidation peak potentials separation between DA and UA reached to 145mV. By using the differential pulse voltammetry (DPV) technique, the calibration curves for DA and UA were found linear with the concentration range of 0.45-421μM and 6-469.5μM and the detection limit (S/N =3) were calculated to be 0.18μM and 1.6μM, respectively. Furthermore, the Pd/RGO/GCE displayed high selectivity when it was applied into the determination of DA and UA even though in presence of high concentration of interferents. Additionally, the prepared electrochemical sensor of Pd/RGO/GCE demonstrated a practical feasibility in rat urine and serum samples determination. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. Voltammetric determination of sudan ii in food samples at graphene modified glassy carbon electrode based on the enhancement effect of sodium dodecyl sulfate

    International Nuclear Information System (INIS)

    Ma, X.; Chen, M.; Chao, M.

    2013-01-01

    Summary: Herein, a novel electrochemical method was de veloped for the determination of Sudan II based on the electrochemical catalytic activity of graphene modified glassy carbon electrode (GME) and the enhancement effect of sodium dodecyl sulfate (SDS). In a pH 6.0 phosphate buffer solution, Sudan II exhibited a pair of well-defined quasi reversible redox peaks at the GME in the presence of 5.0x10/sup -5/ mol L/sup 1/ SDS. The oxidation peak current of Sudan II was linearly proportional to its concentration in a range from 4.0x10/sup -8/ to 4.0x10/sup -6/ mol L/sup 1/, with a linear regression equation of ipa (A) = 3.35 c + 5.96 x 10/sup -6/, r = 0.9988 and a detection limit of 8.0x10/sup -9/ mol L/sup 1/. The recoveries from the standards fortified blank samples were in the range of 94.7% to 97.5% with RSD lower than 4.0%. The novel method has been successfully used to determine Sudan II in food products with satisfactory results. (author)

  20. In Situ Determination of Bisphenol A in Beverage Using a Molybdenum Selenide/Reduced Graphene Oxide Nanoparticle Composite Modified Glassy Carbon Electrode

    Directory of Open Access Journals (Sweden)

    Rongguang Shi

    2018-05-01

    Full Text Available Due to the endocrine disturbing effects of bisphenol A (BPA on organisms, rapid detection has become one of the most important techniques for monitoring its levels in the aqueous solutions associated with plastics and human beings. In this paper, a glassy carbon electrode (GCE modified with molybdenum selenide/reduced graphene oxide (MoSe2/rGO was fabricated for in situ determination of bisphenol A in several beverages. The surface area of the electrode dramatically increases due to the existence of ultra-thin nanosheets in a flower-like structure of MoSe2. Adding phosphotungstic acid in the electrolyte can significantly enhance the repeatability (RSD = 0.4% and reproducibility (RSD = 2.2% of the electrode. Under the optimized condition (pH = 6.5, the linear range of BPA was from 0.1 μM–100 μM and the detection limit was 0.015 μM (S/N = 3. When using the as-prepared electrode for analyzing BPA in beverage samples without any pretreatments, the recoveries ranged from 98–107%, and the concentrations were from below the detection limit to 1.7 μM, indicating its potential prospect for routine analysis of BPA.

  1. In Situ Determination of Bisphenol A in Beverage Using a Molybdenum Selenide/Reduced Graphene Oxide Nanoparticle Composite Modified Glassy Carbon Electrode.

    Science.gov (United States)

    Shi, Rongguang; Liang, Jing; Zhao, Zongshan; Liu, Yi; Liu, Aifeng

    2018-05-22

    Due to the endocrine disturbing effects of bisphenol A (BPA) on organisms, rapid detection has become one of the most important techniques for monitoring its levels in the aqueous solutions associated with plastics and human beings. In this paper, a glassy carbon electrode (GCE) modified with molybdenum selenide/reduced graphene oxide (MoSe₂/rGO) was fabricated for in situ determination of bisphenol A in several beverages. The surface area of the electrode dramatically increases due to the existence of ultra-thin nanosheets in a flower-like structure of MoSe₂. Adding phosphotungstic acid in the electrolyte can significantly enhance the repeatability (RSD = 0.4%) and reproducibility (RSD = 2.2%) of the electrode. Under the optimized condition (pH = 6.5), the linear range of BPA was from 0.1 μM⁻100 μM and the detection limit was 0.015 μM (S/ N = 3). When using the as-prepared electrode for analyzing BPA in beverage samples without any pretreatments, the recoveries ranged from 98⁻107%, and the concentrations were from below the detection limit to 1.7 μM, indicating its potential prospect for routine analysis of BPA.

  2. Amperometric cholesterol biosensor based on the direct electrochemistry of cholesterol oxidase and catalase on a graphene/ionic liquid-modified glassy carbon electrode.

    Science.gov (United States)

    Gholivand, Mohammad Bagher; Khodadadian, Mehdi

    2014-03-15

    Cholesterol oxidase (ChOx) and catalase (CAT) were co-immobilized on a graphene/ionic liquid-modified glassy carbon electrode (GR-IL/GCE) to develop a highly sensitive amperometric cholesterol biosensor. The H2O2 generated during the enzymatic reaction of ChOx with cholesterol could be reduced electrocatalytically by immobilized CAT to obtain a sensitive amperometric response to cholesterol. The direct electron transfer between enzymes and electrode surface was investigated by cyclic voltammetry. Both enzymes showed well-defined redox peaks with quasi-reversible behaviors. An excellent sensitivity of 4.163 mA mM(-1)cm(-2), a response time less than 6s, and a linear range of 0.25-215 μM (R(2)>0.99) have been observed for cholesterol determination using the proposed biosensor. The apparent Michaelis-Menten constant (KM(app)) was calculated to be 2.32 mM. The bienzymatic cholesterol biosensor showed good reproducibility (RSDsascorbic acid and uric acid. The CAT/ChOx/GR-IL/GCE showed excellent analytical performance for the determination of free cholesterol in human serum samples. © 2013 Elsevier B.V. All rights reserved.

  3. Electroanalysis of formetanate hydrochloride by a cobalt phthalocyanine functionalized multiwalled carbon nanotubes modified electrode: characterization and application in fruits

    International Nuclear Information System (INIS)

    Ribeiro, Francisco Wirley Paulino; Souza Lucas, Francisco Willian de; Mascaro, Lucia H.; Morais, Simone; Naftali da Silva Casciano, Paulo; Lima-Neto, Pedro de; Correia, Adriana N.

    2016-01-01

    Highlights: • A Co-phthalocyanine functionalized MWCNT modified carbon electrode was developed. • Formetanate (FMT) electroanalytical behavior is consistent with an ECE mechanism. • CoPc-fMWCNT/GCE exhibited good analytical performance to quantify FMT. • CoPc-fMWCNT/GCE was successfully applied to fruits (recoveries ≥ 94.2%). - Abstract: This study characterizes the electroanalytical behavior of the carbamate pesticide formetanate hydrochloride (FMT) at a cobalt phthalocyanine (CoPc) functionalized multiwalled carbon nanotubes (fMWCNT) modified glassy carbon electrode (CoPc-fMWCNT/GCE). Nafion ® was used to improve solubility and dispersibility of fMWCNT. The construction of the developed electrode was characterized by high-resolution field-emission gun scanning electron microscopy, Raman spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy. FMT exhibited a behavior consistent with a three-step reaction of the electrochemical-chemical-electrochemical mechanistic type at CoPc-fMWCNT/GCE (three anodic peaks at 0.26, 0.55 and 1.2 V, and two cathodic peaks at 0.35 and 0.50 V vs. Ag/AgCl/3 M KCl). Highly reproducible and well-defined peaks were obtained at the optimum experimental conditions (Britton-Robinson buffer at pH 5.0, accumulation potential 1.55 V, accumulation time 5 s, frequency 100 s −1 , amplitude 30 mV, and scan increment 3 mV). Peak currents were found to be proportional to the FMT concentrations in the range of 9.80 × 10 −8 to 3.92 × 10 −6 mol dm −3 with a detection limit (LOD) of 9.7 × 10 −8 mol dm −3 . The modification of GCE with CoPc-fMWCNT enhanced the electrocatalytic activity and provided high sensitivity (3.51 A mol −1 dm 3 ). The developed electroanalytical methodology was successfully applied to FMT residue analysis in mango and grape samples with recoveries in the range of 94.2 ± 4.5 to 105.7 ± 1.8%. The proposed electroanalytical approach represents a reliable, sensitive and environmental

  4. Microbial electrolysis cells with polyaniline/multi-walled carbon nanotube-modified biocathodes

    International Nuclear Information System (INIS)

    Chen, Yingwen; Xu, Yuan; Chen, Liuliu; Li, Peiwen; Zhu, Shemin; Shen, Shubao

    2015-01-01

    In this paper, we modified biocathodes with PANI (Polyaniline)/MWCNT (Multi-Walled Carbon Nanotube) composites to improve hydrogen production in single-chamber, membrane-free biocathode MECs. The results showed that the hydrogen production rates increased with an increase in applied voltage. At an applied voltage of 0.9 V, the modified biocathode MECs achieved a hydrogen production rate of 0.67m 3 m −3 d −1 , current density of 205 Am −3 , COD of 86.8%, coulombic efficiency of 72%, cathodic hydrogen recovery of 42%, and energy efficiency of 81% with respect to the electrical power input. LSV (Linear Sweep Voltammetry) scans, SEM (Scanning Electron Microscopy) images and DGGE (Denaturing Gradient Gel Electrophoresis) demonstrated that hydrogen production is catalyzed by the special biofilm attached on a modified biocathode, and the microorganism species and quantity present were significantly different between the modified biocathode and the non-modified biocathode. In general, the performance of MECs with modified biocathodes was improved in the presence of a higher current density and hydrogen generation rate. - Highlights: • Different PANI/MWCNT composites were prepared and used to modify biocathode in MECs. • The performance of MECs was improved by the modification. • 75% wt PANI/MWCNT modified biocathode showed the better capacity on hydrogen generation. • LVS, SEM, DGGE were determined to figure out the effect of modification on MECs. • PANI/MWCNT modified biocathode in MECs was first studied to push MECs technology forward

  5. A novel voltammetric sensor for sensitive detection of mercury(II) ions using glassy carbon electrode modified with graphene-based ion imprinted polymer

    Energy Technology Data Exchange (ETDEWEB)

    Ghanei-Motlagh, Masoud, E-mail: m.ghaneimotlagh@yahoo.com [Young Researchers and Elite Club, Kerman Branch, Islamic Azad University, Kerman (Iran, Islamic Republic of); Taher, Mohammad Ali; Heydari, Abolfazl [Department of Chemistry, Faculty of Sciences, Shahid Bahonar University of Kerman, Kerman (Iran, Islamic Republic of); Ghanei-Motlagh, Reza [Department of Pathobiology, Faculty of Veterinary Medicine, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Gupta, Vinod K. [Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee 247667 (India); Department of Applied Chemistry, University of Johannesburg, Johannesburg (South Africa)

    2016-06-01

    In this paper, a novel strategy was proposed to prepare ion-imprinted polymer (IIP) on the surface of reduced graphene oxide (RGO). Polymerization was performed using methacrylic acid (MAA) as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linker, 2,2′–((9E,10E)–1,4–dihydroxyanthracene–9,10–diylidene) bis(hydrazine–1–carbothioamide) (DDBHCT) as the chelating agent and ammonium persulfate (APS) as initiator, via surface imprinted technique. The RGO–IIP was characterized by means of Fourier transform infrared spectroscopy (FT–IR), field emission scanning electron microscopy (FE–SEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The electrochemical procedure was based on the accumulation of Hg(II) ions at the surface of a modified glassy carbon electrode (GCE) with RGO–IIP. The prepared RGO–IIP sensor has higher voltammetric response compared to the non-imprinted polymer (NIP), traditional IIP and RGO. The RGO–IIP modified electrode exhibited a linear relationship toward Hg(II) concentrations ranging from 0.07 to 80 μg L{sup −1}. The limit of detection (LOD) was found to be 0.02 μg L{sup −1} (S/N = 3), below the guideline value from the World Health Organization (WHO). The applicability of the proposed electrochemical sensor to determination of mercury(II) ions in different water samples was reported. - Highlights: • The novel Hg(II)-imprinted polymer was synthesized and characterized. • The resulting RGO–IIP was applied for electrochemical monitoring of Hg(II) ions. • The proposed sensor was successfully applied for determination of Hg(II) in real water samples.

  6. Carbon fiber microelectrodes modified with carbon nanotubes as a new support for immobilization of glucose oxidase

    International Nuclear Information System (INIS)

    Wen, H.; Nallathambi, V.; Chakraborty, D.; Barton, S.C.

    2011-01-01

    Carboxylated carbon nanotubes were coated onto carbon microfiber electrodes to create a micron-scale bioelectrode. This material has a high surface area and can serve as a support for immobilization of enzymes such as glucose oxidase. A typical carbon nanotube loading of 13 μg cm -1 yields a coating thickness of 17 μm and a 2000-fold increase in surface capacitance. The modified electrode was further coated with a biocatalytic hydrogel composed of a conductive redox polymer, glucose oxidase, and a crosslinker to create a glucose bioelectrode. The current density on oxidation of glucose is 16.6 mA cm-2 at 0.5 V (vs. Ag/AgCl) in oxygen-free glucose solution. We consider this approach to be useful for designing and characterizing surface treatments for carbon mats and papers by mimicking their local microenvironment. (author)

  7. Two-dimensional dopant profiling by electrostatic force microscopy using carbon nanotube modified cantilevers

    International Nuclear Information System (INIS)

    Chin, S.-C.; Chang, Y.-C.; Chang, C.-S.; Tsong, T T; Hsu, Chen-Chih; Wu, Chih-I; Lin, W-H; Woon, W-Y; Lin, L-T; Tao, H-J

    2008-01-01

    A two-dimensional (2D) dopant profiling technique is demonstrated in this work. We apply a unique cantilever probe in electrostatic force microscopy (EFM) modified by the attachment of a multiwalled carbon nanotube (MWNT). Furthermore, the tip apex of the MWNT was trimmed to the sharpness of a single-walled carbon nanotube (SWNT). This ultra-sharp MWNT tip helps us to resolve dopant features to within 10 nm in air, which approaches the resolution achieved by ultra-high vacuum scanning tunnelling microscopy (UHV STM). In this study, the CNT-probed EFM is used to profile 2D buried dopant distribution under a nano-scale device structure and shows the feasibility of device characterization for sub-45 nm complementary metal-oxide-semiconductor (CMOS) field-effect transistors

  8. Visible light photoelectrocatalysis with salicylic acid-modified TiO2 nanotube array electrode for p-nitrophenol degradation

    International Nuclear Information System (INIS)

    Wang Xin; Zhao Huimin; Quan Xie; Zhao Yazhi; Chen Shuo

    2009-01-01

    This research focused on immersion method synthesis of visible light active salicylic acid (SA)-modified TiO 2 nanotube array electrode and its photoelectrocatalytic (PEC) activity. The SA-modified TiO 2 nanotube array electrode was synthesized by immersing in SA solution with an anodized TiO 2 nanotube array electrode. Scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (IR), UV-vis diffuse reflectance spectrum (DRS), and Surface photovoltage (SPV) were used to characterize this electrode. It was found that SA-modified TiO 2 nanotube array electrode absorbed well into visible region and exhibited enhanced visible light PEC activity on the degradation of p-nitrophenol (PNP). The degradation efficiencies increased from 63 to 100% under UV light, and 79-100% under visible light (λ > 400 nm), compared with TiO 2 nanotube array electrode. The enhanced PEC activity of SA-modified TiO 2 nanotube array electrode was attributed to the amount of surface hydroxyl groups introduced by SA-modification and the extension of absorption wavelength range.

  9. Electrocatalytic simultaneous determination of ascorbic acid, uric acid and L–Cysteine in real samples using quercetin silver nanoparticles–graphene nanosheets modified glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Zare, Hamid R., E-mail: hrzare@yazd.ac.ir; Jahangiri-Dehaghani, Fahime; Shekari, Zahra; Benvidi, Ali

    2016-07-01

    Highlights: • Quercetin AgNPs graphene nanosheets modified GCE (Q–AgNPs–GNs–GCE) was prepared as a new sensor. • Q–AgNPs–GNs–GCE shows a high catalytic activity for L–Cysteine (L–Cys) oxidation. • In DPV, the calibration plots were linear within two ranges of 0.9–12.4 μM and 12.4–538.5 μM of L–Cys. • The proposed modified electrode is used for the simultaneous determinations of AA, UA and L–Cys. • Q–AgNPs–GNs–GCE was satisfactorily used for the determination of AA, UA and L–Cys in real samples. - Abstract: By immobilizing of quercetin at the surface of a glassy carbon electrode modified with silver nanoparticles and graphene nanosheets (Q–AgNPs–GNs–GCE) a new sensor has been fabricated. The cyclic voltammogram of Q–AgNPs–GNs–GCE shows a stable redox couple with surface confined characteristics. Q–AgNPs–GNs–GCE demonstrated a high catalytic activity for L–Cysteine (L–Cys) oxidation. Results indicated that L–Cys peak potential at Q–AgNPs–GNs–GCE shifted to less positive values compared to GNs–GCE or AgNPs–GCE. Also, the kinetic parameters such as the electron transfer coefficient,, and the heterogeneous electron transfer rate constant, k′, for the oxidation of L–Cys at the Q–AgNPs–GNs–GCE surface were estimated. In differential pulse voltammetric determination, the detection limit of L–Cys was obtained 0.28 μM, and the calibration plots were linear within two ranges of 0.9–12.4 μM and 12.4–538.5 μM of L–Cys. Also, the proposed modified electrode is used for the simultaneous determinations of ascorbic acid (AA), uric acid (UA), and L–Cys. Finally, this study has demonstrated the practical analytical utility of the sensor for determination of AA in vitamin C tablet, L–Cys in a milk sample and UA in a human urine sample.

  10. Electrocatalytic simultaneous determination of ascorbic acid, uric acid and L–Cysteine in real samples using quercetin silver nanoparticles–graphene nanosheets modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Zare, Hamid R.; Jahangiri-Dehaghani, Fahime; Shekari, Zahra; Benvidi, Ali

    2016-01-01

    Highlights: • Quercetin AgNPs graphene nanosheets modified GCE (Q–AgNPs–GNs–GCE) was prepared as a new sensor. • Q–AgNPs–GNs–GCE shows a high catalytic activity for L–Cysteine (L–Cys) oxidation. • In DPV, the calibration plots were linear within two ranges of 0.9–12.4 μM and 12.4–538.5 μM of L–Cys. • The proposed modified electrode is used for the simultaneous determinations of AA, UA and L–Cys. • Q–AgNPs–GNs–GCE was satisfactorily used for the determination of AA, UA and L–Cys in real samples. - Abstract: By immobilizing of quercetin at the surface of a glassy carbon electrode modified with silver nanoparticles and graphene nanosheets (Q–AgNPs–GNs–GCE) a new sensor has been fabricated. The cyclic voltammogram of Q–AgNPs–GNs–GCE shows a stable redox couple with surface confined characteristics. Q–AgNPs–GNs–GCE demonstrated a high catalytic activity for L–Cysteine (L–Cys) oxidation. Results indicated that L–Cys peak potential at Q–AgNPs–GNs–GCE shifted to less positive values compared to GNs–GCE or AgNPs–GCE. Also, the kinetic parameters such as the electron transfer coefficient,, and the heterogeneous electron transfer rate constant, k′, for the oxidation of L–Cys at the Q–AgNPs–GNs–GCE surface were estimated. In differential pulse voltammetric determination, the detection limit of L–Cys was obtained 0.28 μM, and the calibration plots were linear within two ranges of 0.9–12.4 μM and 12.4–538.5 μM of L–Cys. Also, the proposed modified electrode is used for the simultaneous determinations of ascorbic acid (AA), uric acid (UA), and L–Cys. Finally, this study has demonstrated the practical analytical utility of the sensor for determination of AA in vitamin C tablet, L–Cys in a milk sample and UA in a human urine sample.

  11. An electrochemical sensor for warfarin determination based on covalent immobilization of quantum dots onto carboxylated multiwalled carbon nanotubes and chitosan composite film modified electrode

    International Nuclear Information System (INIS)

    Gholivand, Mohammad Bagher; Mohammadi-Behzad, Leila

    2015-01-01

    A method is described for the construction of a novel electrochemical warfarin sensor based on covalent immobilization of CdS-quantum dots (CdS-QDs) onto carboxylated multiwalled carbon nanotubes/chitosan (CS) composite film on the surface of a glassy carbon electrode. The CdS-QDs/CS/MWCNTs were characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infra-red (FTIR) spectroscopy, XRD analysis and electrochemical impedance spectroscopy (EIS). The sensor showed optimum anodic stripping response within 90 s at an accumulation potential of 0.75 V. The modified electrode was used to detect the concentration of warfarin with a wide linear range of 0.05–80 μM and a detection limit (S/N = 3) of 8.5 nM. The proposed sensor has good storage stability, repeatability and reproducibility and was successfully applied for the determination of warfarin in real samples such as urine, serum and milk. - Highlights: • A new sensitive sensor for warfarin determination was developed. • The sensor was constructed based on covalent immobilization of CdS-QDs on the chitosan/MWCNTs/GCE. • The parameters affecting the stripping analysis of warfarin were optimized. • The proposed sensor is used for trace determination of warfarin in urine, serum and milk

  12. Amperometric sensing of NADH and ethanol using a hybrid film electrode modified with electrochemically fabricated zirconia nanotubes and poly (acid fuchsin)

    International Nuclear Information System (INIS)

    Liu, X.; Li, B.; Zhan, G.; Liu, C.; Li, C.; Ma, M.

    2012-01-01

    We report on a glassy carbon electrode (GCE) modified with a film of chitosin containing acid fuchsin (AF) adsorbed onto zirconia nanotubes. The mixture was polymerized by cyclic voltammetric scannings in the potential range from - 0. 8 V to +1. 3 V in buffer solution to produce a hybrid film electrode (nano-ZrO 2 /PAF/GCE). The morphology of the hybrid film electrode surface was characterized by scanning electron microscopy. Its electrochemical properties were studied via electrochemical impedance spectroscopy. The electrochemical response of nicotinamide adenine dinucleotide (NADH) was investigated by differential pulse voltammetry and amperometry. The results indicated that the nano-ZrO 2 /PAF/GCE possesses well synergistic catalytic activity towards NADH. Compared to an unmodified GCE, the oxidation overpotential is negatively shifted by 224 mV, and the oxidation current is significantly increased. Under optimal conditions, the amperometric response is linearly proportional to the concentration of NADH in the 1. 0 - 100. 0 μM concentration range. Ethanol also can be determined by amperometry if alcohol dehydrogenase and NADH are added to the sample. Two linear relationships between current and alcohol concentration were obtained. They cover the range from 0. 03 to 1. 0 mM, and from 1. 0 to 12. 0 mM. (author)

  13. An electrochemical sensor for warfarin determination based on covalent immobilization of quantum dots onto carboxylated multiwalled carbon nanotubes and chitosan composite film modified electrode

    Energy Technology Data Exchange (ETDEWEB)

    Gholivand, Mohammad Bagher, E-mail: mbgholivand2013@gmail.com; Mohammadi-Behzad, Leila

    2015-12-01

    A method is described for the construction of a novel electrochemical warfarin sensor based on covalent immobilization of CdS-quantum dots (CdS-QDs) onto carboxylated multiwalled carbon nanotubes/chitosan (CS) composite film on the surface of a glassy carbon electrode. The CdS-QDs/CS/MWCNTs were characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infra-red (FTIR) spectroscopy, XRD analysis and electrochemical impedance spectroscopy (EIS). The sensor showed optimum anodic stripping response within 90 s at an accumulation potential of 0.75 V. The modified electrode was used to detect the concentration of warfarin with a wide linear range of 0.05–80 μM and a detection limit (S/N = 3) of 8.5 nM. The proposed sensor has good storage stability, repeatability and reproducibility and was successfully applied for the determination of warfarin in real samples such as urine, serum and milk. - Highlights: • A new sensitive sensor for warfarin determination was developed. • The sensor was constructed based on covalent immobilization of CdS-QDs on the chitosan/MWCNTs/GCE. • The parameters affecting the stripping analysis of warfarin were optimized. • The proposed sensor is used for trace determination of warfarin in urine, serum and milk.

  14. Surface-enhanced oxidation and detection of Sunset Yellow and Tartrazine using multi-walled carbon nanotubes film-modified electrode.

    Science.gov (United States)

    Zhang, Weikang; Liu, Tao; Zheng, Xiaojiang; Huang, Wensheng; Wan, Chidan

    2009-11-01

    The insoluble multi-walled carbon nanotubes (MWNT) was successfully dispersed into water in the presence of hydrophobic surfactant. After that, MWNT film-coated glassy carbon electrode (GCE) was achieved via dip-coating and evaporating water. Owing to huge surface area, high sorption capacity and subtle electronic properties, MWNT film exhibits highly efficient accumulation efficiency as well as considerable surface enhancement effects to Sunset Yellow and Tartrazine. As a result, the oxidation peak currents of Sunset Yellow and Tartrazine remarkably increase at the MWNT film-modified GCE. Based on this, a novel electrochemical method was developed for the simultaneous determination of Sunset Yellow and Tartrazine. The limits of detection are 10.0 ng mL(-1) (2.2 x 10(-8)mol L(-1)) and 0.1 microg mL(-1) (1.88 x 10(-7)mol L(-1)) for Sunset Yellow and Tartrazine. Finally, the proposed method was successfully used to detect Sunset Yellow and Tartrazine in soft drinks.

  15. Layer-by-Layer Assembly of Glucose Oxidase on Carbon Nanotube Modified Electrodes.

    Science.gov (United States)

    Suroviec, Alice H

    2017-01-01

    The use of enzymatically modified electrodes for the detection of glucose or other non-electrochemically active analytes is becoming increasingly common. Direct heterogeneous electron transfer to glucose oxidase has been shown to be kinetically difficult, which is why electron transfer mediators or indirect detection is usually used for monitoring glucose with electrochemical sensors. It has been found, however, that electrodes modified with single or multi-walled carbon nanotubes (CNTs) demonstrate fast heterogeneous electron transfer kinetics as compared to that found for traditional electrodes. Incorporating CNTs into the assembly of electrochemical glucose sensors, therefore, affords the possibility of facile electron transfer to glucose oxidase, and a more direct determination of glucose. This chapter describes the methods used to use CNTs in a layer-by-layer structure along with glucose oxidase to produce an enzymatically modified electrode with high turnover rates, increased stability and shelf-life.

  16. Removal of copper ions from water using chemical modified multi-walled carbon nanotubes

    International Nuclear Information System (INIS)

    Zhang, Y.J.; Yang, J.

    2014-01-01

    Multi-walled carbon nanotubes (CNTs) were modified by oxidation with sodium hypochlorite (NaClO) solutions and were employed as adsorbents to study the adsorption characteristics of copper ions from water. The results show that adsorption capacity of CNTs treated by NaClO solution can be greatly enhanced. The adsorption capacity of Cu2+ on as received and modified CNTs increased with the increase of pH and CNTs mass, but it decreased with the temperature. Experimental data also indicated that the adsorption process could achieve equilibrium within 40 min. Both Langmuir and Freundlich isotherm models fitted the experimental data very well. According to the Langmuir model the maximum copper ions adsorption uptake onto modified CNTs was determined as 40.00 mg/g. Our results suggest that CNTs have profound potential application in environmental protection. (author)

  17. Simultaneous determination of 2,4,6-trichlorophenol and pentachlorophenol based on poly(Rhodamine B)/graphene oxide/multiwalled carbon nanotubes composite film modified electrode

    International Nuclear Information System (INIS)

    Zhu, Xiaolin; Zhang, Kexin; Lu, Nan; Yuan, Xing

    2016-01-01

    Graphical abstract: A poly(Rhodamine B)/graphene oxide/multiwalled carbon nanotubes composite film modified glassy carbon electrode (PRhB/GO/MWCNTs/GCE) was developed for the simultaneous determination of 2,4,6-trichlorophenol (2,4,6-TCP) and pentachlorophenol (PCP) without any pretreatment. - Highlights: • A poly(RhB)/graphene oxide/multiwalled carbon nanotubes composite was synthesized. • The composite film was characterized by SEM, XRD, EIS and Raman spectroscopy. • The simultaneous electrochemical determination of 2,4,6-TCP and PCP was realized. • The electrode showed high sensitivity, excellent reproducibility and good stability. • The electrode was used to determine 2,4,6-TCP and PCP in practical water samples. - Abstract: In the present study, a poly(Rhodamine B)/graphene oxide/multiwalled carbon nanotubes nanocomposite modified glass carbon electrode (PRhB/GO/MWCNTs/GCE) was developed for the simultaneous determination of 2,4,6-trichlorophenol (2,4,6-TCP) and pentachlorophenol (PCP). The PRhB/GO/MWCNTs film was extensively characterized by emission scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and electrochemical impedance spectroscopy (EIS). The electrochemical behaviors of 2,4,6-TCP and PCP were investigated by cyclic voltammetry, linear sweep voltammetry and differential pulse voltammetry. Due to the synergistic effect, the PRhB/GO/MWCNTs/GCE significantly facilitated the simultaneous electro-oxidation of 2,4,6-TCP and PCP with peak potential difference of 160 mV and enhanced oxidation currents. Under optimum conditions, the oxidation current of 2,4,6-TCP was linear to its concentration in the ranges of 4.0 × 10"−"9 to 1.0 × 10"−"7 M and 1.0 × 10"−"7 to 1.0 × 10"−"4 M with the detection limit (S/N = 3) of 8.0 × 10"−"1"0 M. And the linear concentration ranges for PCP were 2.0 × 10"−"9 to 1.0 × 10"−"7 M and 1.0 × 10"−"7 to 9.0 × 10"−"5 M with the detection limit of 5.0 × 10"−"1"0 M

  18. Simultaneous determination of 2,4,6-trichlorophenol and pentachlorophenol based on poly(Rhodamine B)/graphene oxide/multiwalled carbon nanotubes composite film modified electrode

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Xiaolin; Zhang, Kexin; Lu, Nan; Yuan, Xing, E-mail: yuanx@nenu.edu.cn

    2016-01-15

    Graphical abstract: A poly(Rhodamine B)/graphene oxide/multiwalled carbon nanotubes composite film modified glassy carbon electrode (PRhB/GO/MWCNTs/GCE) was developed for the simultaneous determination of 2,4,6-trichlorophenol (2,4,6-TCP) and pentachlorophenol (PCP) without any pretreatment. - Highlights: • A poly(RhB)/graphene oxide/multiwalled carbon nanotubes composite was synthesized. • The composite film was characterized by SEM, XRD, EIS and Raman spectroscopy. • The simultaneous electrochemical determination of 2,4,6-TCP and PCP was realized. • The electrode showed high sensitivity, excellent reproducibility and good stability. • The electrode was used to determine 2,4,6-TCP and PCP in practical water samples. - Abstract: In the present study, a poly(Rhodamine B)/graphene oxide/multiwalled carbon nanotubes nanocomposite modified glass carbon electrode (PRhB/GO/MWCNTs/GCE) was developed for the simultaneous determination of 2,4,6-trichlorophenol (2,4,6-TCP) and pentachlorophenol (PCP). The PRhB/GO/MWCNTs film was extensively characterized by emission scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and electrochemical impedance spectroscopy (EIS). The electrochemical behaviors of 2,4,6-TCP and PCP were investigated by cyclic voltammetry, linear sweep voltammetry and differential pulse voltammetry. Due to the synergistic effect, the PRhB/GO/MWCNTs/GCE significantly facilitated the simultaneous electro-oxidation of 2,4,6-TCP and PCP with peak potential difference of 160 mV and enhanced oxidation currents. Under optimum conditions, the oxidation current of 2,4,6-TCP was linear to its concentration in the ranges of 4.0 × 10{sup −9} to 1.0 × 10{sup −7} M and 1.0 × 10{sup −7} to 1.0 × 10{sup −4} M with the detection limit (S/N = 3) of 8.0 × 10{sup −10} M. And the linear concentration ranges for PCP were 2.0 × 10{sup −9} to 1.0 × 10{sup −7} M and 1.0 × 10{sup −7} to 9.0 × 10{sup −5} M with the

  19. Highly Sensitive and Selective Detection of Dopamine at Poly(chromotrope 2B)-Modified Glassy Carbon Electrode in the Presence of Uric Acid and Ascorbic Acid

    International Nuclear Information System (INIS)

    Li, Xiao-Bo; Rahman, Md. Mahbubur; Xu, Guang-Ri; Lee, Jae-Joon

    2015-01-01

    A highly sensitive and selective electrochemical method based on a poly(chromotrope 2B)-modified anodized glassy carbon electrode (PCHAGCE) was developed for the determination of dopamine (DA) in the presence of uric acid (UA) and ascorbic acid (AA). The PCHAGCE sensor exhibited excellent electron-mediating behavior towards the oxidation of DA in 0.1 M phosphate buffer solution (PBS) (pH 7.0). It was found that the electrocatalytic activity was significantly dependent on the charge status and molecular structure of the target molecules. Differential pulse voltammetry (DPV) measurements revealed oxidation signals for DA, UA, and AA that were well-resolved into three distinct peaks with AA–DA, DA–UA, and AA–UA peak potential separations (ΔE p ) of 172, 132, and 304 mV, respectively. A detection limit of 0.04 ± 0.001 μM (S/N = 3) and a quantification limit (S/N = 10) of 0.149 ± 0.03 μM were obtained for DA sensing in a linear range of 1 to 40 μM in PBS (pH 7.0) with a very high sensitivity of 1.522 ± 0.032 μA·μM −1 . The DA concentrations in human urine samples were also successfully determined with recoveries of 94.0–98.0%. This approach provides a simple, easy, sensitive, and selective method to detect DA in the presence of AA and UA

  20. A new kinetic–mechanistic approach to elucidate electrooxidation of doxorubicin hydrochloride in unprocessed human fluids using magnetic graphene based nanocomposite modified glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Soleymani, Jafar [Hematology–Oncology Research Center, Tabriz University of Medical Sciences, Tabriz 51664 (Iran, Islamic Republic of); Hasanzadeh, Mohammad, E-mail: Mhmmd_hasanzadeh@yahoo.com [Drug Applied Research Center, Tabriz University of Medical Sciences, Tabriz (Iran, Islamic Republic of); Shadjou, Nasrin [Department of Nanochemistry, Nano Technology Center, and Faculty of Chemistry, Urmia University, Urmia (Iran, Islamic Republic of); Khoubnasab Jafari, Maryam [Tuberculosis and Lung Disease Research Center, Tabriz University of Medical Sciences, Tabriz (Iran, Islamic Republic of); Gharamaleki, Jalil Vaez [Hematology–Oncology Research Center, Tabriz University of Medical Sciences, Tabriz 51664 (Iran, Islamic Republic of); Yadollahi, Mehdi [Department of Organic Chemistry, Faculty of Chemistry, Tabriz University, Tabriz (Iran, Islamic Republic of); Jouyban, Abolghasem [Pharmaceutical Analysis Research Center and Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz (Iran, Islamic Republic of)

    2016-04-01

    A novel magnetic nanocomposite was synthesized in one step using polymerization of magnetic graph oxide grafted with chlorosulfonic acid (Fe{sub 3}O{sub 4}–GO–SO{sub 3}H) in the presence of polystyrene. The prepared magnetic nanocomposite was characterized using transmission electron microscopy (TEM), dynamic differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), (Thermo-gravimetric/differential thermal analysis (DTA)), Fourier transform infrared (FTIR), and UV–Vis techniques. Magnetic nanocomposite was casted on the surface of the glassy carbon electrode (PS/Fe{sub 3}O{sub 4}–GO–SO{sub 3}H/GCE) and used for the detection and determination of doxorubicin hydrochloride (DOX) in human biological fluids. The cyclic voltammograms (CVs) of the modified electrode in aqueous solution displayed a pair of well-defined, stable and irreversible reductive/oxidation redox systems. CV study indicated that the oxidation process is irreversible and adsorption controlled. In addition, CV results indicated that DOX is oxidized via two electrons and three protons which is an unusual approach for the oxidation of DOX. A sensitive and time-saving procedure was developed for the analysis of DOX in plasma, cerebrospinal fluid, and urine with detection limit of 4.9 nM, 14 nM and 4.3 nM, respectively. - Highlights: • A novel magneto-polymeric nanocomposite (PS/Fe{sub 3}O{sub 4}–GO–SO{sub 3}H) was synthesized. • Application of PS/Fe{sub 3}O{sub 4}–GO–SO{sub 3}H toward detection of DOX was investigated by electrochemistry. • A new kinetic–mechanistic approach to elucidate electrooxidation of DOX was obtained. • DOX was detected in plasma, cerebrospinal fluid, and urine.

  1. The Cu-MOF-199/single-walled carbon nanotubes modified electrode for simultaneous determination of hydroquinone and catechol with extended linear ranges and lower detection limits

    International Nuclear Information System (INIS)

    Zhou, Jian; Li, Xi; Yang, Linlin; Yan, Songlin; Wang, Mengmeng; Cheng, Dan; Chen, Qi; Dong, Yulin; Liu, Peng; Cai, Weiquan; Zhang, Chaocan

    2015-01-01

    A novel electrochemical sensor based on Cu-MOF-199 [Cu-MOF-199 = Cu 3 (BTC) 2 (BTC = 1,3,5-benzenetricarboxylicacid)] and SWCNTs (single-walled carbon nanotubes) was fabricated for the simultaneous determination of hydroquinone (HQ) and catechol (CT). The modification procedure was carried out through casting SWCNTs on the bare glassy carbon electrode (GCE) and followed by the electrodeposition of Cu-MOF-199 on the SWCNTs modified electrode. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) were performed to characterize the electrochemical performance and surface characteristics of the as-prepared sensor. The composite electrode exhibited an excellent electrocatalytic activity with increased electrochemical signals towards the oxidation of HQ and CT, owing to the synergistic effect of SWCNTs and Cu-MOF-199. Under the optimized condition, the linear response range were from 0.1 to 1453 μmol L −1 (R HQ  = 0.9999) for HQ and 0.1–1150 μmol L −1 (R CT  = 0.9990) for CT. The detection limits for HQ and CT were as low as 0.08 and 0.1 μmol L −1 , respectively. Moreover, the modified electrode presented the good reproducibility and the excellent anti-interference performance. The analytical performance of the developed sensor for the simultaneous detection of HQ and CT had been evaluated in practical samples with satisfying results. - Highlights: • Cu-MOF-199/SWCNTs/GCE was facilely fabricated by the electrodeposition on SWCNTs/GCE. • An electrochemical sensor for detecting HQ and CT was constructed based on this modified electrode. • The proposed electrochemical sensor showed an extended linear range and lower detection limits. • The proposed electrochemical sensor had an excellent stability and reproducibility.

  2. Simultaneous Determination of Copper, Lead, and Cadmium Ions at a Mo6S9-xIx Nanowires Modified Glassy Carbon Electrode Using Differential Pulse Anodic Stripping Voltammetry

    International Nuclear Information System (INIS)

    Lin, Hong; Li, Meixian; Mihailovič, Dragan

    2015-01-01

    Highlights: • An electrochemical sensor based on Mo 6 S 9-x I x nanowires was constructed. • Mo 6 S 9-x I x nanowires can amplify electrochemical responses of heavy metal ions. • Mo 6 S 9-x I x nanowires can promote electron transfer. • Mo 6 S 9-x I x nanowires can accumulate metal ions due to large surface area. • The preparation of the sensor is simple, short-time and it does not require a special apparatus. -- ABSTRACT: A novel electrochemical sensor based on a new kind of nanomaterials Mo 6 S 9-x I x nanowires modified glassy carbon electrode (GCE) was constructed for simultaneous determination of cadmium(II), lead(II) and copper(II) using differential pulse anodic stripping voltammetry (DPASV). Various experimental parameters such as the modified amount, pH, deposition time and deposition potential were optimized. Under the optimal conditions, the stripping peak currents increase linearly with increasing concentrations of Cd(II), Pb(II) and Cu(II) ions in the ranges of 0.5∼150 μg · L −1 , 1.5∼450 μg · L −1 and 0.8~240 μg · μg·L −1 , 1.5∼450 μg·L −1 and 0.8∼240 μg·L −1 , respectively. And the limits of detection (S/N = 3) are estimated to be 0.10 μg · L −1 for Cd (II), 0.45 μg·L −1 for Pb(II) and 0.20 μg·L −1 for Cu(II), which are two orders of magnitude lower than those obtained at the unmodified electrodes. Most importantly, the sensor has been successfully applied to the determination of trace metal ions in the tap water samples. This developed electrochemical sensor exhibits high sensitivity, good stability and reproducibility

  3. Aspects of the Fracture Toughness of Carbon Nanotube Modified Epoxy Polymer Composites

    Science.gov (United States)

    Mirjalili, Vahid

    Epoxy resins used in fibre reinforced composites exhibit a brittle fracture behaviour, because they show no sign of damage prior to a catastrophic failure. Rubbery materials and micro-particles have been added to epoxy resins to improve their fracture toughness, which reduces strength and elastic properties. In this research, carbon nanotubes (CNTs) are investigated as a potential toughening agent for epoxy resins and carbon fibre reinforced composites, which can also enhance strength and elastic properties. More specifically, the toughening mechanisms of CNTs are investigated theoretically and experimentally. The effect of aligned and randomly oriented carbon nanotubes (CNTs) on the fracture toughness of polymers was modelled using Elastic Plastic Fracture Mechanics. Toughening from CNT pull-out and rupture were considered, depending on the CNTs critical length. The model was used to identify the effect of CNTs geometrical and mechanical properties on the fracture toughness of CNT-modified epoxies. The modelling results showed that a uniform dispersion and alignment of a high volume fraction of CNTs normal to the crack growth plane would lead to the maximum fracture toughness enhancement. To achieve a uniform dispersion, the effect of processing on the dispersion of single walled and multi walled CNTs in epoxy resins was investigated. An instrumented optical microscope with a hot stage was used to quantify the evolution of the CNT dispersion during cure. The results showed that the reduction of the resin viscosity at temperatures greater than 100 °C caused an irreversible re-agglomeration of the CNTs in the matrix. The dispersion quality was then directly correlated to the fracture toughness of the modified resin. It was shown that the fine tuning of the ratio of epoxy resin, curing agent and CNT content was paramount to the improvement of the base resin fracture toughness. For the epoxy resin (MY0510 from Hexcel), an improvement of 38% was achieved with 0.3 wt

  4. Plasma-modified graphene nanoplatelets and multiwalled carbon nanotubes as fillers for advanced rubber composites

    International Nuclear Information System (INIS)

    Sicinski, M; Gozdek, T; Bielinski, D M; Kleczewska, J; Szymanowski, H; Piatkowska, A

    2015-01-01

    In modern rubber industry, there still is a room for new fillers, which can improve the mechanical properties of the composites, or introduce a new function to the material. Modern fillers like carbon nanotubes or graphene nanoplatelets (GnP), are increasingly applied in advanced polymer composites technology. However, it might be hard to obtain a well dispersed system for such systems. The polymer matrix often exhibits higher surface free energy (SFE) level with the filler, which can cause problems with polymer-filler interphase adhesion. Filler particles are not wet properly by the polymer, and thus are easier to agglomerate. As a consequence, improvement in the mechanical properties is lower than expected. In this work, multi-walled carbon nanotubes (MWCNT) and GnP surface were modified with low-temperature plasma. Attempts were made to graft some functionalizing species on plasma-activated filler surface. The analysis of virgin and modified fillers’ SFE was carried out. MWCNT and GnP rubber composites were produced, and ultimately, their morphology and mechanical properties were studied. (paper)

  5. Electrochemical sensor for hazardous food colourant quinoline yellow based on carbon nanotube-modified electrode.

    Science.gov (United States)

    Zhao, Jun; Zhang, Yu; Wu, Kangbing; Chen, Jianwei; Zhou, Yikai

    2011-09-15

    A novel electrochemical method using multi-wall carbon nanotube (MWNT) film-modified electrode was developed for the detection of quinoline yellow. In pH 8 phosphate buffer, an irreversible oxidation peak at 0.71V was observed for quinoline yellow. Compared with the unmodified electrode, the MWNT film-modified electrode greatly increases the oxidation peak current of quinoline yellow, showing notable enhancement effect. The effects of pH value, amount of MWNT, accumulation potential and time were studied on the oxidation peak current of quinoline yellow. The linear range is from 0.75 to 20mgL(-1), and the limit of detection is 0.5mgL(-1). It was applied to the detection of quinoline yellow in commercial soft drinks, and the results consisted with the value that obtained by high-performance liquid chromatography. Copyright © 2011 Elsevier Ltd. All rights reserved.

  6. Synthesis and Characterizations of Poly(3-hexylthiophene and Modified Carbon Nanotube Composites

    Directory of Open Access Journals (Sweden)

    Mohammad Rezaul Karim

    2012-01-01

    Full Text Available Poly(3-hexylthiophene and modified (functionalized and silanized multiwall carbon nanotube (MWNT nanocomposites have been prepared through in situ polymerization process in chloroform medium with FeCl3 oxidant at room temperature. The composites are characterized through Fourier transfer infrared spectroscopy (FT-IR, Raman, and X-ray diffraction (XRD measurements to probe the nature of interaction between the moieties. Optical properties of the composites are measured from ultraviolet-visible (UV-Vis and photoluminescence (PL spectroscopy. Conductivity of the composites is followed by four probe techniques to understand the conduction mechanism. The change (if any in C=C symmetric and antisymmetric stretching frequencies in FT-IR, the shift in G band frequencies in Raman, any alterations in λmax of UV-Vis, and PL spectroscopic measurements are monitored with modified MWNT loading in the polymer matrix.

  7. Electrochemical properties of seamless three-dimensional carbon nanotubes-grown graphene modified with horseradish peroxidase.

    Science.gov (United States)

    Komori, Kikuo; Terse-Thakoor, Trupti; Mulchandani, Ashok

    2016-10-01

    Horseradish peroxidase (HRP) was immobilized through sodium dodecyl sulfate (SDS) on the surface of a seamless three-dimensional hybrid of carbon nanotubes grown at the graphene surface (HRP-SDS/CNTs/G) and its electrochemical properties were investigated. Compared with graphene alone electrode modified with HRP via SDS (HRP-SDS/G electrode), the surface coverage of electroactive HRP at the CNTs/G electrode surface was approximately 2-fold greater because of CNTs grown at the graphene surface. Based on the increase in the surface coverage of electroactive HRP, the sensitivity to H2O2 at the HRP-SDS/CNTs/G electrode was higher than that at the HRP-SDS/G electrode. The kinetics of the direct electron transfer from the CNTs/G electrode to compound I and II of modified HRP was also analyzed. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. Multilayer poly(3,4-ethylenedioxythiophene)-dexamethasone and poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate-carbon nanotubes coatings on glassy carbon microelectrode arrays for controlled drug release.

    Science.gov (United States)

    Castagnola, Elisa; Carli, Stefano; Vomero, Maria; Scarpellini, Alice; Prato, Mirko; Goshi, Noah; Fadiga, Luciano; Kassegne, Sam; Ricci, Davide

    2017-07-13

    The authors present an electrochemically controlled, drug releasing neural interface composed of a glassy carbon (GC) microelectrode array combined with a multilayer poly(3,4-ethylenedioxythiophene) (PEDOT) coating. The system integrates the high stability of the GC electrode substrate, ideal for electrical stimulation and electrochemical detection of neurotransmitters, with the on-demand drug-releasing capabilities of PEDOT-dexamethasone compound, through a mechanically stable interlayer of PEDOT-polystyrene sulfonate (PSS)-carbon nanotubes (CNT). The authors demonstrate that such interlayer improves both the mechanical and electrochemical properties of the neural interface, when compared with a single PEDOT-dexamethasone coating. Moreover, the multilayer coating is able to withstand 10 × 10 6 biphasic pulses and delamination test with negligible change to the impedance spectra. Cross-section scanning electron microscopy images support that the PEDOT-PSS-CNT interlayer significantly improves the adhesion between the GC substrate and PEDOT-dexamethasone coating, showing no discontinuities between the three well-interconnected layers. Furthermore, the multilayer coating has superior electrochemical properties, in terms of impedance and charge transfer capabilities as compared to a single layer of either PEDOT coating or the GC substrate alone. The authors verified the drug releasing capabilities of the PEDOT-dexamethasone layer when integrated into the multilayer interface through repeated stimulation protocols in vitro, and found a pharmacologically relevant release of dexamethasone.

  9. Probing the electrochemical double layer of an ionic liquid using voltammetry and impedance spectroscopy: a comparative study of carbon nanotube and glassy carbon electrodes in [EMIM](+)[EtSO(4)](-).

    Science.gov (United States)

    Zheng, J P; Goonetilleke, P C; Pettit, C M; Roy, D

    2010-05-15

    Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are compared as techniques for analyzing double layer capacitances of ionic liquids (ILs) at the surfaces of two carbon-based electrodes. These systems are relevant for energy storage supercapacitors and often are associated with unconventional electrochemical properties. Certain theoretical and experimental aspects of CV and EIS necessary for quantitative evaluation of the capacitance characteristics of such systems are explored. The experiments use 1-ethyl-3-methyl imidazolium ethylsulfate as a model IL electrolyte in combination with a porous electrode of carbon nanotubes (CNTs). The results are compared with those obtained with a nonporous glassy carbon (GC) electrode. The time is constant, and hence the power delivery characteristics of the experimental cell are affected by the electrolyte resistance and residual faradaic reactions of the IL, as well as by the spatially inhomogeneous electrode surfaces. It is shown that adequate characterization of these IL-electrode systems can be achieved by combining CV with EIS. A phenomenological framework for utilizing this combination is discussed.

  10. The heat storage material based on paraffin-modified multilayer carbon nanotubes with Nickel-zinc ferrite

    Science.gov (United States)

    Shchegolkov, A.; Shchegolkov, A.; Dyachkova, T.; Semenov, A.

    2018-02-01

    The paper presents an investigation of magnetically controlled heat-storage material based on paraffin, modified with multilayer carbon nanotubes with nickel-zinc ferrite. The technology of obtaining nanomodified material capable of interacting with magnetic field is presented. The study of the heat-exchange processes of charge/discharge with the help of magnetic field are carried out.

  11. Structural, electronic and mechanical properties of inner surface modified imogolite nanotubes

    Directory of Open Access Journals (Sweden)

    Maurício Chagas Da Silva

    2015-03-01

    Full Text Available The electronic, structural and mechanical properties of the modified imogolites have been investigated using self consistent charge-density functional-tight binding method with a posteriori treatment of the dispersion interaction (SCC-DFTB-D. The zigzag (12,0 imogolite has been used as the initial structure for the calculations. The functionalization of the interior (12,0 imogolite nanotubes by organosilanes and by heat treatment leading to the dehydroxylation of the silanols were investigated. The reaction of the silanols with the trimethylmethoxysilanes is favored and the arrangement of the different substitutions that leads to the most symmetrical structures are preferred. The Young moduli and band gaps are slightly decreased. However, the dehydroxylation of the silanol groups in the inner surface of the imogolite leads to the increase of the Young moduli and a drastic decrease of the band gap of about 4.4 eV. It has been shown that the degree of the dehydroxylation can be controlled by heat treatment and tune the band gap, eventually, leading to a semiconductor material with well defined nanotube structure.

  12. Bilirubin oxidase bound to multi-walled carbon nanotube-modified gold

    International Nuclear Information System (INIS)

    Schubert, Kirsten; Goebel, Gero; Lisdat, Fred

    2009-01-01

    We report on direct electron transfer (DET) reactions of bilirubin oxidase at multi-walled carbon nanotube-(MWCNT) modified gold electrodes. MWCNTs are very suitable for protein immobilisation and provide surface groups that can be used for the stable fixation on electrodes. They can also effectively replace the natural substrate of BOD - bilirubin, the electron donor for oxygen reduction. The bioelectrocatalytic oxygen reduction was recorded using linear sweep voltammetry (LSV) with BOD covalently linked to the nanotubes. The start potential of the bioelectrocatalytic oxygen reduction at pH 7 and a scan rate of 10 mV/s was determined to be 485 ± 10 mV vs. Ag/AgCl, 1 M KCl (720 mV vs. SHE). Current densities up to 500 μA/cm 2 were detected in an air-saturated buffer at room temperature (25 ± 5 deg. C). Experiments with a rotating disk electrode (RDE) indicate a diffusion controlled electrode reaction. A k s value in the range of 80-100 s -1 could be estimated. The DET could also be observed directly by the redox conversion of a copper centre of BOD under anaerobic conditions. A peak pair with a formal potential of 680 ± 10 mV vs. SHE was found. The T1 site is probably addressed by the electrode as indicated by several experimental studies

  13. XPS analysis of the carbon fibers surface modified via HMDSO to carbon nanotube growth

    Energy Technology Data Exchange (ETDEWEB)

    Cardoso, L.D.R.; Gomes, M.C.B.; Trava-Airoldi, V.J.; Corat, E.J.; Lugo, D.C. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil)

    2016-07-01

    Full text: Carbon fibers (CF) have been widely used to reinforce structural composites. Due to their strength-to-weight properties, CF composites are finding increased structural uses in areas such as aerospace, aeronautical, automobile and others. The strength of the fiber-resin interface bond has been found to be the limiting factor to the mechanical properties of CF-epoxy materials, due to their non-polar nature that limit the affinity of CF to bind chemically to any matrix. The growth of carbon nanotubes (CNTs) on the surface of CF is a promising approach for improving mechanical, electrical and thermal properties of structural composites. However growing CNTs on CF presents some obstacles, such as diffusion of metal catalyst particles on CF, uneven CNT growth and loss of mechanical properties of CF. To avoid the diffusion of catalyst particles we modified the CF surface with hexamethyldisiloxane (HMDSO) at low temperature (400 °C), also preventing the loss of mechanical properties and allowing uniform CNTs growth. We deposited CNTs via floating catalyst method, with ferrocene providing the catalyst particle and the oxidative dehydrogenation reaction of acetylene providing the carbon. The CF surface modification was analyzed via X-ray photoelectron spectroscopy (XPS) and CNTs growth via scanning electron microscopy with field emission gun. The XPS analysis showed that HMDSO promotes the binding of oxygen to carbon and silicon present on CF surface, the chemical modification of the surface of the CF enables the uniform growth of carbon nanotubes. (author)

  14. XPS analysis of the carbon fibers surface modified via HMDSO to carbon nanotube growth

    International Nuclear Information System (INIS)

    Cardoso, L.D.R.; Gomes, M.C.B.; Trava-Airoldi, V.J.; Corat, E.J.; Lugo, D.C.

    2016-01-01

    Full text: Carbon fibers (CF) have been widely used to reinforce structural composites. Due to their strength-to-weight properties, CF composites are finding increased structural uses in areas such as aerospace, aeronautical, automobile and others. The strength of the fiber-resin interface bond has been found to be the limiting factor to the mechanical properties of CF-epoxy materials, due to their non-polar nature that limit the affinity of CF to bind chemically to any matrix. The growth of carbon nanotubes (CNTs) on the surface of CF is a promising approach for improving mechanical, electrical and thermal properties of structural composites. However growing CNTs on CF presents some obstacles, such as diffusion of metal catalyst particles on CF, uneven CNT growth and loss of mechanical properties of CF. To avoid the diffusion of catalyst particles we modified the CF surface with hexamethyldisiloxane (HMDSO) at low temperature (400 °C), also preventing the loss of mechanical properties and allowing uniform CNTs growth. We deposited CNTs via floating catalyst method, with ferrocene providing the catalyst particle and the oxidative dehydrogenation reaction of acetylene providing the carbon. The CF surface modification was analyzed via X-ray photoelectron spectroscopy (XPS) and CNTs growth via scanning electron microscopy with field emission gun. The XPS analysis showed that HMDSO promotes the binding of oxygen to carbon and silicon present on CF surface, the chemical modification of the surface of the CF enables the uniform growth of carbon nanotubes. (author)

  15. Carbon nanotubes modified with SnO{sub 2} rods for levofloxacin detection

    Energy Technology Data Exchange (ETDEWEB)

    Cesarino, Vivian [Universidade de Sao Paulo (USP), Sao Carlos, SP (Brazil). Escola de Engenharia; Cesarino, Ivana; Moraes, Fernando C.; Machado, Sergio A.S., E-mail: ivana@iqsc.usp.br [Universidade de Sao Paulo (USP), Sao Carlos, SP (Brazil). Instituto de Quimica; Mascaro, Lucia H. [Universidade Federal de Sao Carlos (UFSCar), SP (Brazil). Departamento de Quimica

    2014-03-15

    A new sensor based on multi-walled carbon nanotubes modified with SnO{sub 2} rods for the electrochemical determination of levofloxacin has been investigated. The morphology, the structure, and the electrochemical performance of the composite electrode were characterised by scanning electron microscopy, energy dispersive X-ray spectroscopy, and cyclic voltammetry, respectively. Differential pulse voltammetry in phosphate buffer solution at pH 6.0, allowed the application of a method to determine levofloxacin levels in a range of 1.0-9.9 μmol L{sup -1}, with a limit of detection calculated at 0.2 μmol L{sup -1} (72.0 mg L{sup -1}). (author)

  16. Mechanical, Rheological and Thermal Properties of Polystyrene/1-Octadecanol Modified Carbon Nanotubes Nanocomposites

    KAUST Repository

    Amr, Issam Thaher

    2014-09-04

    The results of the studies on the functionalization of multi-walled carbon nanotubes (MWCNT) with 1-octadecanol and its usage as reinforcing filler in the bulk polymerization of styrene are reported in this article. Both unmodified and modified CNTs were utilized in different loadings, however, without any initiator. The resulting composites were characterized by using mechanical testing, differential scanning calorimetry, thermogravimetric analysis and melt rheology. The tensile tests show the addition of 0.5wt% of CNT-C18 results in 19.5% increment of Young\\'s modulus. The DSC study shows a decrease in T-g values of prepared PS/CNT nanocomposite. The rheological study was conducted at 190 degrees C and shows that addition of pure CNT increased the viscoelastic behavior of the PS matrices, while the CNT-C18 act as plasticizer. Thermogravimetric analysis shows that the incorporation of CNT into PS enhanced the thermal properties significantly.

  17. Titania nanotube arrays surface-modified with ZnO for enhanced photocatalytic applications

    Energy Technology Data Exchange (ETDEWEB)

    Nageri, Manoj; Kalarivalappil, Vijila; Vijayan, Baiju K.; Kumar, Viswanathan, E-mail: vkumar10@yahoo.co.in

    2016-05-15

    Highlights: • Heterostructures of TNA/ZnO synthesised through potentiostatic anodisation followed by hydrothermal method. • Evaluation of morphological features of the heterostructure with hydrothermal processing time. • Correlation of photocatalytic activity of the hetrostructure with its morphology and surface texture. - Abstract: Well ordered titanium dioxide nanotube arrays (TNA) of average diameter 129 nm and wall thickness of 25 nm were fabricated through potentiostatic anodisation of titanium (Ti) metal substrates. Such TNA were subsequently surface-modified with various amounts of zinc oxide (ZnO) nanopowders using hydrothermal technique to obtain heterogeneous TNA/ZnO nanostructures. The crystalline phase and surface microstructure of the heterostructures were determined by X-ray diffraction, Raman spectroscopy and scanning electron microscopy respectively. The morphology of the heterostructures strongly depended on the hydrothermal conditions employed. The photocatalytic activity of the heterostructures have also been investigated and correlated with their surface morphology and texture.

  18. Voltammetric determination of carbidopa and folic acid using a modified carbon nanotubes paste electrode

    Directory of Open Access Journals (Sweden)

    Keshtkar Nasrin

    2015-01-01

    Full Text Available A novel electrochemical sensor for the selective and sensitive detection of carbidopa in presence of large excess of folic acid at physiological pH was developed by the bulk modification of carbon paste electrode (CPE with carbon nanotubes (CNTs and vinylferrocene. Large peak separation, good sensitivity and stability allow this modified electrode to analyze carbidopa individually and simultaneously along with folic acid. Applying square wave voltammetry (SWV, a linear dynamic range of 1.0×10-6- 7.0×10-4 M with detection limit of 2.0×10-7 M was obtained for carbidopa. Finally, the proposed method was applied to the determination of carbidopa and folic acid in urine sample.

  19. Electrochemical detection of carbidopa using a ferrocene-modified carbon nanotube paste electrode

    Directory of Open Access Journals (Sweden)

    FATEMEH KARIMI

    2009-12-01

    Full Text Available A chemically modified carbon paste electrode (MCPE containing ferrocene (FC and carbon nanotubes (CNT was constructed. The electrochemical behavior and stability of the MCPE were investigated by cyclic voltammetry. The electrocatalytic activity of the MCPE was investigated and it showed good characteristics for the oxidation of carbidopa (CD in phosphate buffer solution (PBS. A linear concentration range of 5 to 600 μM CD, with a detection limit of 3.6±0.17 μM CD, was obtained. The diffusion coefficient of CD and the transfer coefficient ( were also determined. The MCPE 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 the determination of CD in real samples, such as urine samples.

  20. Chitosan matrices modified with carbon nanotubes for use in mediated microbial biosensing

    International Nuclear Information System (INIS)

    Demirkol, D.O.; Timur, S.

    2011-01-01

    We describe a microbial sensor based on Pseudomonas fluorescens cells that was prepared by modifying graphite electrodes with chitosan and carbon nanotubes. Chronoamperometry was performed at +0.3 V in the presence of hexacyanoferrate as a mediator and revealed a good response to glucose which is linear in the 1.0 to 5.0 mM concentration range. Linearity was defined by the equation of y = 102.120x-13.279 (R2 = 0.998) (y shows current density as nA. cm-2 and x shows glucose concentration in mM). The effect of the CNTs on the response was compared to that of electrodes made without CNTs. (author)

  1. Photoelectrochemical performance of cadmium sulfide quantum dots modified titania nanotube arrays

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Yibing, E-mail: ybxie@seu.edu.cn

    2016-01-01

    The cadmium sulfide quantum dots modified titania nanotube arrays (CdS QDs/TiO{sub 2} NTAs) were prepared through a sequential sonication-assisted chemical bath deposition (CBD) process. The morphology and microstructure of CdS QDs/TiO{sub 2} NTAs were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectroscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy and UV–vis diffuse reflectance spectroscopy. The photoelectrochemical performance of CdS QDs/TiO{sub 2} NTAs was investigated under solar light illumination. The affecting parameters were studied including the nanotube length of TiO{sub 2} NTAs, CBD cycles of CdS QDs and the annealing treatment of CdS QDs/TiO{sub 2} NTAs. CdS QDs synthesized through 8 CBD cycles could uniformly cover on the tube walls of TiO{sub 2} NTAs to form unique CdS QDs/TiO{sub 2} NTAs with an open pore mouth. The appropriate annealing treatment at 400 °C for 60 min in N{sub 2} atmosphere could improve the crystallinity of CdS QDs, and accordingly enhance the photovoltaic properties of CdS QDs/TiO{sub 2} NTAs. Significantly, the nanotube length was the predominant factor affecting photoelectrochemical performance of CdS QDs/TiO{sub 2} NTAs. The unannealed CdS QDs/TiO{sub 2} NTAs with an optimal nanotube length of 12 μm achieved a short-circuit photocurrent density of 4.37 mA cm{sup −2}, an open circuit photovoltage of 1.10 V and a top photoconversion efficiency of 3.56%. Comparatively, the annealed CdS QDs/TiO{sub 2} NTAs with an optimal nanotube length of 4 μm achieved a short-circuit photocurrent density of 6.31 mA cm{sup −2}, an open circuit photovoltage of 1.23 V and a top photoconversion efficiency of 4.18%. The suitable modification of crystalline CdS QDs could well improve the photoelectrochemical performance of TiO{sub 2} NTAs photoanode. - Highlights: • CdS QDs are uniformly loaded into short and long TiO{sub 2} NTAs to form CdS QDs/TiO{sub 2} NTAs.

  2. Mechanical performance of HMA-2 modified with purified and unpurified carbon nanotubes and nanofibers

    Directory of Open Access Journals (Sweden)

    Mario Rodrigo Rubio

    2017-05-01

    Full Text Available The present study evaluates the mechanical performance of a Hot Mix Asphalt – Type II (HMA-2 modified with carbon nanotubes and carbon nanofibers (CNTF. CNTF were made by means the Catalytic Vapor Deposition (CVD technique at 700° C using a Nickel, Copper and Aluminum (NiCuAl catalyst with a Cu/Ni molar relation of 0,33. In order to properly assess HMA-2 performance, three different mixtures were analyzed: 1 HMA-2 modified with purified CNTF; 2 HMA-2 modified with non-purified CNTF and, 3 a Conventional HMA-2 (control. Samples manufactured in accordance with the Marshall Mix Design were tested in the laboratory to study rutting, resilient modulus (Mr and fatigue. In addition to the aforementioned dynamic characterization, the effect of CNTF purification on the asphalt mixture’s mechanical properties was analyzed. In short, a comparative study was designed to determine whether or not CNTF should be purified before introduction into the HMA-2. This investigation responds to the growing demand for economical materials capable of withstanding traffic loads while simultaneously enhancing pavement durability and mechanical properties. Although purified CNTF increased HMA-2 stiffness and elastic modulus, non-purified CNTF increased the asphalt mixture’s elastic modulus without considerable increases in stiffness. Thus, the latter modification is deemed to help address fatiguerelated issues and improve the long-term durability of flexible pavements.

  3. Oxidized multi walled carbon nanotubes for improving the electrocatalytic activity of a benzofuran derivative modified electrode

    Directory of Open Access Journals (Sweden)

    Mohammad Mazloum-Ardakani

    2016-01-01

    Full Text Available In the present paper, the use of a novel carbon paste electrode modified by 7,8-dihydroxy-3,3,6-trimethyl-3,4-dihydrodibenzo[b,d]furan-1(2H-one (DTD and oxidized multi-walled carbon nanotubes (OCNTs is described for determination of levodopa (LD, acetaminophen (AC and tryptophan (Trp by a simple and rapid method. At first, the electrochemical behavior of DTD is studied, then, the mediated oxidation of LD at the modified electrode is investigated. At the optimum pH of 7.4, the oxidation of LD occurs at a potential about 330 mV less positive than that of an unmodified carbon paste electrode. Based on differential pulse voltammetry (DPV, the oxidation current of LD exhibits a linear range between 1.0 and 2000.0 μM of LD with a detection limit (3σ of 0.36 μM. DPV was also used for simultaneous determination of LD, AC and Trp at the modified electrode. Finally, the proposed electrochemical sensor was used for determinations of these substances in human serum sample.

  4. Deposition of carbon nanotubes onto aramid fibers using as-received and chemically modified fibers

    International Nuclear Information System (INIS)

    Rodríguez-Uicab, O.; Avilés, F.; Gonzalez-Chi, P.I; Canché-Escamilla, G.; Duarte-Aranda, S.; Yazdani-Pedram, M.; Toro, P.; Gamboa, F.; Mazo, M.A.; Nistal, A.; Rubio, J.

    2016-01-01

    Highlights: • The surface of aramid fibers was functionalized by two acid treatments. • The treatment based on HNO_3/H_2SO_4 reduced the mechanical properties of the fibers. • CNTs were deposited on the aramid fibers, reaching electrical conductivity. • Homogeneous CNT distribution was achieved by using pristine fibers or chlorosulfonic acid. - Abstract: Multiwall carbon nanotubes (MWCNTs) oxidized by an acid treatment were deposited on the surface of as-received commercial aramid fibers containing a surface coating (“sizing”), and fibers modified by either a chlorosulfonic treatment or a mixture of nitric and sulfuric acids. The surface of the aramid fiber activated by the chemical treatments presents increasing density of CO, COOH and OH functional groups. However, these chemical treatments reduced the tensile mechanical properties of the fibers, especially when the nitric and sulfuric acid mixture was used. Characterization of the MWCNTs deposited on the fiber surface was conducted by scanning electron microscopy, Raman spectroscopy mapping and X-ray photoelectron spectroscopy. These characterizations showed higher areal concentration and more homogeneous distribution of MWCNTs over the aramid fibers for as-received fibers and for those modified with chlorosulfonic acid, suggesting the existence of interaction between the oxidized MWCNTs and the fiber coating. The electrical resistance of the MWCNT-modified aramid yarns comprising ∼1000 individual fibers was in the order of MΩ/cm, which renders multifunctional properties.

  5. Deposition of carbon nanotubes onto aramid fibers using as-received and chemically modified fibers

    Energy Technology Data Exchange (ETDEWEB)

    Rodríguez-Uicab, O. [Centro de Investigación Científica de Yucatán A.C., Unidad de Materiales, Calle 43 No.130, Col. Chuburna de Hidalgo, C.P. 97200 Mérida, Yucatán (Mexico); Avilés, F., E-mail: faviles@cicy.mx [Centro de Investigación Científica de Yucatán A.C., Unidad de Materiales, Calle 43 No.130, Col. Chuburna de Hidalgo, C.P. 97200 Mérida, Yucatán (Mexico); Gonzalez-Chi, P.I; Canché-Escamilla, G.; Duarte-Aranda, S. [Centro de Investigación Científica de Yucatán A.C., Unidad de Materiales, Calle 43 No.130, Col. Chuburna de Hidalgo, C.P. 97200 Mérida, Yucatán (Mexico); Yazdani-Pedram, M. [Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, S. Livingstone 1007, Independencia, Santiago (Chile); Toro, P. [Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Av. Beauchef 850, Santiago (Chile); Gamboa, F. [Centro de Investigacion y de Estudios Avanzados del IPN, Unidad Mérida, Depto. de Física Aplicada, Km. 6 Antigua Carretera a Progreso, 97310 Mérida, Yucatán (Mexico); Mazo, M.A.; Nistal, A.; Rubio, J. [Instituto de Cerámica y Vidrio (ICV-CSIC), Kelsen 5, 28049 Madrid (Spain)

    2016-11-01

    Highlights: • The surface of aramid fibers was functionalized by two acid treatments. • The treatment based on HNO{sub 3}/H{sub 2}SO{sub 4} reduced the mechanical properties of the fibers. • CNTs were deposited on the aramid fibers, reaching electrical conductivity. • Homogeneous CNT distribution was achieved by using pristine fibers or chlorosulfonic acid. - Abstract: Multiwall carbon nanotubes (MWCNTs) oxidized by an acid treatment were deposited on the surface of as-received commercial aramid fibers containing a surface coating (“sizing”), and fibers modified by either a chlorosulfonic treatment or a mixture of nitric and sulfuric acids. The surface of the aramid fiber activated by the chemical treatments presents increasing density of CO, COOH and OH functional groups. However, these chemical treatments reduced the tensile mechanical properties of the fibers, especially when the nitric and sulfuric acid mixture was used. Characterization of the MWCNTs deposited on the fiber surface was conducted by scanning electron microscopy, Raman spectroscopy mapping and X-ray photoelectron spectroscopy. These characterizations showed higher areal concentration and more homogeneous distribution of MWCNTs over the aramid fibers for as-received fibers and for those modified with chlorosulfonic acid, suggesting the existence of interaction between the oxidized MWCNTs and the fiber coating. The electrical resistance of the MWCNT-modified aramid yarns comprising ∼1000 individual fibers was in the order of MΩ/cm, which renders multifunctional properties.

  6. Electrochemical immunoassay for the carcinoembryonic antigen based on the use of a glassy carbon electrode modified with an octahedral Cu2O-gold nanocomposite and staphylococcal protein for signal amplification.

    Science.gov (United States)

    Qin, Zhen; Xu, Wei; Chen, Shuai; Chen, Jun; Qiu, Jing Fu; Li, Chao Rui

    2018-04-24

    The authors describe an electrochemical immunoassay for ultrasensitive direct determination of the carcinoembryonic antigen (CEA). A nanocomposite consisting of octahedral Cu2O nanocrystals covered with gold nanoparticles was utilized to modify a glassy carbon electrode which gives a strongly enhanced chronoamperometric signal for H 2 O 2 which is used as an electrochemical probe. The morphology and elemental composition of the the nanocomposite was studied by field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. In addition, staphylococcal protein A was placed on the electrode for efficient capture of antibody to further enhance the sensitivity of the assay. Under optimal conditions and at a typical working voltage of -0.4 V (vs. Ag/AgCl), the response covers the 2 pg·mL -1 to 20 ng·mL -1 CEA concentration range with a 200 fg·mL -1 lower detection limit. The method was successfully applied to the determination of CEA in (spiked) human serum. Graphical abstract Schematic of the fabrication of an electrochemical immunosensor for ultrasensitive detection the carcinoembryonic antigen. The sensor is based on the use of a glassy carbon electrode modified with an octahedral Cu 2 O-gold nanocomposite and staphylococcal protein A for signal amplification.

  7. Electrochemical and Electron Paramagnetic Resonance Study of the Mechanism of Oxidation of Phenazine-di-N-oxide in the Presence of Isopropyl alcohol at Glassy Carbon and Single-Walled Carbon Nanotube Electrodes

    International Nuclear Information System (INIS)

    Kulakovskaya, S.I.; Kulikov, A.V.; Sviridova, L.N.; Stenina, E.V.

    2014-01-01

    Graphical abstract: - Highlights: • The mechanism of oxidation of phenazine-di-N-oxide in the presence of isopropyl alcohol was studied. • The results are explained in terms of the E 1 C 1 E 2 C 2 mechanism of the two-stage electrode process. • The total two-electron catalytic oxidation of i-PrOH in the complex with the phenazine-di-N-oxide radical cation was assumed to occur. - Abstract: The mechanism of oxidation of phenazine-di-N-oxide in the presence of isopropyl alcohol was studied by cyclic voltammetry at glassy carbon (GC) and single-walled carbon nanotubes (SWCNT) electrodes in 0.1 M LiClO 4 solutions in acetonitrile. The adsorption of phenazine-di-N-oxide at SWCNT electrode in 0.1 M LiClO 4 solution in acetonitrile was investigated by measurement of the dependence of the differential double layer capacitance of the electrode C on potential E. The effect of isopropyl alcohol on the shape of cyclic voltammograms (CVs) of phenazine-di-N-oxide and the intensity of Electron Paramagnetic Resonance (EPR) signal of its radical cation was investigated. The catalytic currents were recorded at the oxidation of phenazine-di-N-oxide at SWCNT and GC electrodes in the presence of isopropyl alcohol. The results were explained in terms of the E 1 C 1 E 2 C 2 mechanism of two-stage electrode process characterized by catalytic current recorded at the second electrode stage. The overall two-electron catalytic oxidation of isopropyl alcohol in complex with the phenazine-di-N-oxide radical cation was assumed to occur. It was shown that SWCNT electrodes can be used in the electrocatalytic oxidation of organic compounds in the presence of electrochemically generated phenazine-di-N-oxide radical cation

  8. A pH sensor based on the TiO{sub 2} nanotube array modified Ti electrode

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Rongrong; Xu Meizhu [Ministry of Education Key Laboratory of Analysis and Detection for Food Safety, Fujian Provincial Key Laboratory of Analysis and Detection for Food Safety, Department of Chemistry, Fuzhou University, 523 Gongye Road, Fuzhou 350002, Fujian (China); Wang Jian, E-mail: jwang@fzu.edu.c [Ministry of Education Key Laboratory of Analysis and Detection for Food Safety, Fujian Provincial Key Laboratory of Analysis and Detection for Food Safety, Department of Chemistry, Fuzhou University, 523 Gongye Road, Fuzhou 350002, Fujian (China); Chen Guonan, E-mail: guonanchen@126.co [Ministry of Education Key Laboratory of Analysis and Detection for Food Safety, Fujian Provincial Key Laboratory of Analysis and Detection for Food Safety, Department of Chemistry, Fuzhou University, 523 Gongye Road, Fuzhou 350002, Fujian (China)

    2010-08-01

    In this paper, a novel solid state pH sensor was fabricated by anodization of titanium substrate electrode. The relationship between pH sensitivity and hydrophilicity or surface morphology of TiO{sub 2} film was investigated. Amorphous TiO{sub 2} nanotube has better pH response than anatase TiO{sub 2} nanotube. After being irradiated by ultraviolet light (UV), the potential response of the electrode modified by amorphous TiO{sub 2} nanotube was close to Nernst equation (59 mV/pH). SEM, XRD, and XPS were used to characterize electrodes. Possible mechanism was discussed by analyzing surface hydroxyl groups, crystal structure and hydrophilicity of the electrodes. The electrode has been used to detect some kinds of soft drinks and shows good response.

  9. Carbon nanotubes modified with antimony nanoparticles: A novel material for electrochemical sensing

    International Nuclear Information System (INIS)

    Moraes, Fernando C.; Cesarino, Ivana; Cesarino, Vivian; Mascaro, Lucia H.; Machado, Sergio A.S.

    2012-01-01

    Highlights: ► A novel material for the electrochemical sensing was developed. ► Sensor based CNTs modified with Sb-nanoparticles was characterised and applied. ► The proposed sensor was suitable and sensitive for the determination of bisphenol A. - Abstract: In this study, a novel material for the electrochemical determination of bisphenol A using a nanocomposite based on multi-walled carbon nanotubes modified with antimony nanoparticles has been investigated. The morphology, structure, and electrochemical performance of the nanocomposite electrodes were characterised by field emission gun scanning electron microscopy, energy-dispersive X-ray spectroscopy, and cyclic voltammetry. A scan rate study and electrochemical impedance spectroscopy showed that the bisphenol A oxidation product is adsorbed on nanocomposite electrode surface. Differential pulse voltammetry in phosphate buffer solution at pH 6, allowed the development of a method to determine bisphenol A levels in the range of 0.5–5.0 μmol L −1 , with a detection limit of 5.24 nmol L −1 (1.19 μg L −1 ).

  10. Detection of NADH via electrocatalytic oxidation at single-walled carbon nanotubes modified with Variamine blue

    International Nuclear Information System (INIS)

    Radoi, A.; Compagnone, D.; Valcarcel, M.A.; Placidi, P.; Materazzi, S.; Moscone, D.; Palleschi, G.

    2008-01-01

    Screen-printed electrodes (SPEs) modified with Variamine blue (VB), covalently attached to the oxidized single-walled carbon nanotubes (SWCNTs-COOH), were developed and used as chemical sensors for the detection of the reduced nicotinamide adenine dinucleotide (NADH). The Variamine blue redox mediator was covalently linked to the SWCNTs-COOH by the N,N'-dicyclohexylcarbodiimide (DCC) and N-hydroxysuccinimide (NHS) chemistry. Infrared Fourier transform (FT-IR) spectroscopy revealed the presence of the amide bands situated at 1623 cm -1 (I band), 1577 cm -1 (II band) and 1437 cm -1 (III band) demonstrating the covalent linkage of Variamine blue to SWCNTs-COOH. The heterogeneous electron transfer rate, k obs. , was 13,850 M -1 s -1 , and the k s and α were 0.8 s -1 and 0.56, respectively. The pH dependence was also investigated. SPEs modified with Variamine blue by using the DCC/NHS conjugation method, showed a variation of -36 mV per pH unit. A successful application was the development of a lactate biosensor obtained by the immobilization of the L-lactate dehydrogenase on the NADH sensor

  11. Electrochemical sensors and biosensors based on redox polymer/carbon nanotube modified electrodes: a review.

    Science.gov (United States)

    Barsan, Madalina M; Ghica, M Emilia; Brett, Christopher M A

    2015-06-30

    The aim of this review is to present the contributions to the development of electrochemical sensors and biosensors based on polyphenazine or polytriphenylmethane redox polymers together with carbon nanotubes (CNT) during recent years. Phenazine polymers have been widely used in analytical applications due to their inherent charge transport properties and electrocatalytic effects. At the same time, since the first report on a CNT-based sensor, their application in the electroanalytical chemistry field has demonstrated that the unique structure and properties of CNT are ideal for the design of electrochemical (bio)sensors. We describe here that the specific combination of phenazine/triphenylmethane polymers with CNT leads to an improved performance of the resulting sensing devices, because of their complementary electrical, electrochemical and mechanical properties, and also due to synergistic effects. The preparation of polymer/CNT modified electrodes will be presented together with their electrochemical and surface characterization, with emphasis on the contribution of each component on the overall properties of the modified electrodes. Their importance in analytical chemistry is demonstrated by the numerous applications based on polymer/CNT-driven electrocatalytic effects, and their analytical performance as (bio) sensors is discussed. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. Electrochemical characteristics of Shewanella loihica on carbon nanotubes-modified graphite surfaces

    International Nuclear Information System (INIS)

    Zhang, Xiaoming; Epifanio, Monica; Marsili, Enrico

    2013-01-01

    Highlights: • We deposited CNT coatings on graphite electrode by electrophoretic deposition. • CNT coating increased extracellular electron transfer in Shewanella loihica biofilms. • Thick electroactive biofilms hinder the electroactivity of CNT coatings. -- Abstract: High specific surface and electrocatalytic activity of the electrode surface favour extracellular electron transfer from electrochemically active biofilms to polarized electrodes. We coated layer-by-layer carbon nanotubes (CNTs) on graphite electrodes through electrophoretic deposition, thus increasing the electrocatalytic activity. After determining the optimal number of CNT layers through electrochemical methods, we grew Shewanella loihica PV-4 biofilms on the CNT-coated electrodes to quantify the increase in extracellular electron transfer rate compared with unmodified electrodes. Current density on CNT-modified electrodes was 1.7 times higher than that observed on unmodified electrodes after 48 h from inoculation. Rapid microbial cells attachment on CNT-coated electrodes, as determined from scanning electronic microscopy, explained the rapid increase of the current. Also, the CNT reduced the charge transfer resistance of the graphite electrodes, as measured by Electrochemical Impedance Spectroscopy. However, the electrocatalytic activity of the CNT-coated electrode decreased as the biofilm grew thicker and covered the CNT-coating. These result confirmed that surface-modified electrodes improve the electron transfer rate in thin biofilms (<5 μm), but are not feasible for power production in microbial fuel cells, where the biofilm thickness is much higher

  13. Improving the thermal properties of fluoroelastomer (Viton GF-600S using acidic surface modified carbon nanotube

    Directory of Open Access Journals (Sweden)

    Javad Heidarian

    2015-08-01

    Full Text Available AbstractAcid surface modified carbon nanotube (MCNT-, Carbon nanotube (CNT-filled fluoroelastomer (FE and unfilled-FE were prepared (MCNT/FE, CNT/FE and FE. The compounds were subjected to thermogravimetric analysis (TGA and heat air aging, and characterized by Energy Dispersive X-Ray (EDX. Results showed that MCNT improved the thermal properties of FE, resulting in a larger amount of FE and char remaining in the temperature range of 400-900 °C relative to unfilled FE and CNT/FE. The MCNT/FE TGA curve shifted towards higher temperatures compared to CNT/FE and FE. The same results also revealed that higher percentages of FE were undegraded or less degraded especially near MCNT in the temperature range of 400-540 °C. Energy Dispersive X-Ray (EDX results indicated that the percentage of carbon and fluorine in the residue of TGA scans, up to 560 °C, of MCNT/FE were the same as CNT/FE, and were higher than FE. EDX results of TGA residue (run up to 900 °C showed that most of the undegraded FE, which was not degraded at temperatures below 560 °C, was degraded from 560 °C to 900 °C in both MCNT/FE and CNT/FE, with the char in MCNT/FE being more than that in CNT/FE. EDX analysis of thermal aged specimens under air showed that, with increasing aging time, a greater percentage of C, O and F was lost from the surface of filler/FE and FE. The order of element loss after 24 hour aging time was: MCNT/FE > FE > CNT/FE.

  14. Impedimetric microbial biosensor based on single wall carbon nanotube modified microelectrodes for trichloroethylene detection

    International Nuclear Information System (INIS)

    Hnaien, M.; Bourigua, S.; Bessueille, F.; Bausells, J.; Errachid, A.; Lagarde, F.; Jaffrezic-Renault, N.

    2011-01-01

    Highlights: ► We propose an impedimetric microbial biosensor for trichloroethylene detection. ► A new transducer modified with carbon nanotubes and Pseudomonas putida is evaluated. ► Functionalization steps are controlled by impedance spectroscopy and AFM. ► The biosensor offers good sensitivity, selectivity, linear range and stability. ► The biosensor is successfully applied to spiked natural water samples. - Abstract: Contamination of soils and groundwaters with persistent organic pollutants is a matter of increasing concern. The most common organic pollutants are chlorinated hydrocarbons such as perchloroethylene and trichloroethylene (TCE). In this study, we developed a bacterial impedimetric biosensor for TCE detection, based on the immobilization of Pseudomonas putida F1 strain on gold microelectrodes functionalized with single wall carbon nanotubes covalently linked to anti-Pseudomonas antibodies. The different steps of microelectrodes functionalization were characterized by electrochemical impedance and atomic force spectroscopies, and analytical performances of the developed microbial biosensor were determined. The impedimetric biosensor response was linear with TCE concentration up to 150 μg L −1 and a low limit of detection (20 μg L −1 ) was achieved. No significant loss of signal was observed after 4 weeks of storage at 4 °C in phosphate buffer saline pH 7 (three to four measurements a week). After 5 weeks, 90% of the initial value still remained. cis-1,2-Dichloroethylene and vinylchloride, the main TCE degradation products, did not significantly interfere with TCE. The microbial sensor was finally applied to the determination of TCE in natural water samples spiked at the 30, 50 and 75 μg L −1 levels. Recoveries were very good, ranging from 100 to 103%.

  15. A novel highly selective and sensitive detection of serotonin based on Ag/polypyrrole/Cu2O nanocomposite modified glassy carbon electrode.

    Science.gov (United States)

    Selvarajan, S; Suganthi, A; Rajarajan, M

    2018-06-01

    A silver/polypyrrole/copper oxide (Ag/PPy/Cu 2 O) ternary nanocomposite was prepared by sonochemical and oxidative polymerization simple way, in which Cu 2 O was decorated with Ag nanoparticles, and covered by polyprrole (PPy) layer. The as prepared materials was characterized by UV-vis-spectroscopy (UV-vis), FT-IR, X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM) with EDX, high resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS). Sensing of serotonin (5HT) was evaluated electrocatalyst using polypyrrole/glassy carbon electrode (PPy/GCE), polypyrrole/copper oxide/glassy carbon electrode (PPy/Cu 2 O/GCE) and silver/polypyrrole/copper oxide/glassy carbon electrode (Ag/PPy/Cu 2 O/GCE). The Ag/PPy/Cu 2 O/GCE was electrochemically treated in 0.1MPBS solution through cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The peak current response increases linearly with 5-HT concentration from 0.01 to 250 µmol L -1 and the detection limit was found to be 0.0124 μmol L -1 . It exhibits high electrocatalytic activity, satisfactory repeatability, stability, fast response and good selectivity against potentially interfering species, which suggests its potential in the development of sensitive, selective, easy-operation and low-cost serotonin sensor for practical routine analyses. The proposed method is potential to expand the possible applied range of the nanocomposite material for detection of various concerned electro active substances. Copyright © 2018 Elsevier B.V. All rights reserved.

  16. Sol–gel synthesis of tantalum oxide and phosphonic acid-modified carbon nanotubes composite coatings on titanium surfaces

    International Nuclear Information System (INIS)

    Maho, Anthony; Detriche, Simon; Delhalle, Joseph; Mekhalif, Zineb

    2013-01-01

    Carbon nanotubes used as fillers in composite materials are more and more appreciated for the outstanding range of accessible properties and functionalities they generate in numerous domains of nanotechnologies. In the framework of biological and medical sciences, and particularly for orthopedic applications and devices (prostheses, implants, surgical instruments, …), titanium substrates covered by tantalum oxide/carbon nanotube composite coatings have proved to constitute interesting and successful platforms for the conception of solid and biocompatible biomaterials inducing the osseous regeneration processes (hydroxyapatite growth, osteoblasts attachment). This paper describes an original strategy for the conception of resistant and homogeneous tantalum oxide/carbon nanotubes layers on titanium through the introduction of carbon nanotubes functionalized by phosphonic acid moieties (-P(=O)(OH) 2 ). Strong covalent C-P bonds are specifically inserted on their external sidewalls with a ratio of two phosphonic groups per anchoring point. Experimental results highlight the stronger “tantalum capture agent” effect of phosphonic-modified nanotubes during the sol–gel formation process of the deposits compared to nanotubes bearing oxidized functions (-OH, -C=O, -C(=O)OH). Particular attention is also paid to the relative impact of the rate of functionalization and the dispersion degree of the carbon nanotubes in the coatings, as well as their wrapping level by the tantalum oxide matrix material. The resulting effect on the in vitro growth of hydroxyapatite is also evaluated to confirm the primary osseous bioactivity of those materials. Chemical, structural and morphological features of the different composite deposits described herein are assessed by X-ray photoelectron spectroscopy (XPS), scanning (SEM) and transmission (TEM) electronic microscopies, energy dispersive X-rays analysis (EDX) and peeling tests. Highlights: ► Formation of tantalum/carbon nanotube

  17. Sol–gel synthesis of tantalum oxide and phosphonic acid-modified carbon nanotubes composite coatings on titanium surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Maho, Anthony [Laboratory of Chemistry and Electrochemistry of Surfaces, University of Namur (FUNDP), Rue de Bruxelles 61, B-5000 Namur (Belgium); Fonds pour la Formation à la Recherche dans l' Industrie et dans l' Agriculture (FRIA), Rue d' Egmont 5, B-1000 Bruxelles (Belgium); Detriche, Simon; Delhalle, Joseph [Laboratory of Chemistry and Electrochemistry of Surfaces, University of Namur (FUNDP), Rue de Bruxelles 61, B-5000 Namur (Belgium); Mekhalif, Zineb, E-mail: zineb.mekhalif@fundp.ac.be [Laboratory of Chemistry and Electrochemistry of Surfaces, University of Namur (FUNDP), Rue de Bruxelles 61, B-5000 Namur (Belgium)

    2013-07-01

    Carbon nanotubes used as fillers in composite materials are more and more appreciated for the outstanding range of accessible properties and functionalities they generate in numerous domains of nanotechnologies. In the framework of biological and medical sciences, and particularly for orthopedic applications and devices (prostheses, implants, surgical instruments, …), titanium substrates covered by tantalum oxide/carbon nanotube composite coatings have proved to constitute interesting and successful platforms for the conception of solid and biocompatible biomaterials inducing the osseous regeneration processes (hydroxyapatite growth, osteoblasts attachment). This paper describes an original strategy for the conception of resistant and homogeneous tantalum oxide/carbon nanotubes layers on titanium through the introduction of carbon nanotubes functionalized by phosphonic acid moieties (-P(=O)(OH){sub 2}). Strong covalent C-P bonds are specifically inserted on their external sidewalls with a ratio of two phosphonic groups per anchoring point. Experimental results highlight the stronger “tantalum capture agent” effect of phosphonic-modified nanotubes during the sol–gel formation process of the deposits compared to nanotubes bearing oxidized functions (-OH, -C=O, -C(=O)OH). Particular attention is also paid to the relative impact of the rate of functionalization and the dispersion degree of the carbon nanotubes in the coatings, as well as their wrapping level by the tantalum oxide matrix material. The resulting effect on the in vitro growth of hydroxyapatite is also evaluated to confirm the primary osseous bioactivity of those materials. Chemical, structural and morphological features of the different composite deposits described herein are assessed by X-ray photoelectron spectroscopy (XPS), scanning (SEM) and transmission (TEM) electronic microscopies, energy dispersive X-rays analysis (EDX) and peeling tests. Highlights: ► Formation of tantalum

  18. Voltammetric Determination of Acetaminophen in the Presence of Codeine and Ascorbic Acid at Layer-by-Layer MWCNT/Hydroquinone Sulfonic Acid-Overoxidized Polypyrrole Modified Glassy Carbon Electrode

    Directory of Open Access Journals (Sweden)

    Saeed Shahrokhian

    2011-01-01

    Full Text Available A very sensitive electrochemical sensor constructed of a glassy carbon electrode modified with a layer-by-layer MWCNT/doped-overoxidized polypyrrole (oppy/MWCNT /GCE was used for the determination of acetaminophen (AC in the presence of codeine and ascorbic acid (AA. In comparison to the bare glassy carbon electrode, a considerable shift in the peak potential together with an increase in the peak current was observed for AC on the surface of oppy/MWCNT/GCE, which can be related to the enlarged microscopic surface area of the electrode. The effect of the experimental conditions on the electrode response, such as types of counter ion, pyrrole and counter ion concentration, potential and number of cycles in the polymerization procedure, amount of MWCNT, and the pH, were investigated. Under the optimized conditions, the calibration curve was obtained over two concentration ranges of 2 × 10−7–6 × 10−6 M and 4 × 10−5–1 × 10−4 M of AC with a linear correlation coefficient (R2 of 0.9959 and 0.9947, respectively. The estimated detection limit (3σ for AC was obtained as 5 × 10−8 M. The developed method was successfully applied to analyze the pharmaceutical preparations of AC, and a recovery of 95% with a relative standard deviation of 0.98% was obtained for AC.

  19. Poly(3,4-ethylenedioxythiophene-co-(5-amino-2-naphthalenesulfonic acid)) (PEDOT-PANS) film modified glassy carbon electrode for selective detection of dopamine in the presence of ascorbic acid and uric acid

    International Nuclear Information System (INIS)

    Balamurugan, A.; Chen Shenming

    2007-01-01

    Poly(3,4-ethylenedioxythiophene-co-(5-amino-2-naphthalenesulfonic acid)) (PEDOT-PANS) film modified glassy carbon electrode was prepared by electrochemical polymerization technique. The properties of modified electrode was studied. It was found that the electrochemical properties of modified electrode was very much dependent on the experimental conditions, such as monomer oxidation potential and pH. The modified electrode surface was characterized by scanning electron microscopy (SEM). The PEDOT-PANS film modified electrode shows electrocatalytic activity toward oxidation of dopamine (DA) in acetate buffer solution (pH 5.0) and results in a marked enhancement of the current response. The linear sweep voltammetric (LSV) peak heights are linear with DA concentration from 2 x 10 -6 to 1 x 10 -5 M. The detection limit is 5 x 10 -7 M. More over, the interferences of ascorbic acid (AA) and uric acid (UA) were effectively diminished. This work provides a simple and easy approach for selective determination of dopamine in the presence of ascorbic acid and uric acid

  20. Cathodic stripping voltammetric determination of arsenic in sugarcane brandy at a modified carbon nanotube paste electrode.

    Science.gov (United States)

    Teixeira, Meryene C; Tavares, Elisângela de F L; Saczk, Adelir A; Okumura, Leonardo L; Cardoso, Maria das Graças; Magriotis, Zuy M; de Oliveira, Marcelo F

    2014-07-01

    We have developed an eletroanalytical method that employs Cu(2+) solutions to determine arsenic in sugarcane brandy using an electrode consisting of carbon paste modified with carbon nanotubes (CNTPE) and polymeric resins. We used linear sweep (LSV) and differential-pulse (DPV) voltammetry with cathodic stripping for CNTPE containing mineral oil or silicone as binder. The analytical curves were linear from 30 to 110μgL(-1) and from 10 to 110μgL(-1) for LSV and DPV, respectively. The limits of detection (L.O.D.) and quantification (L.O.Q.) of CNTPE were 10.3 and 34.5μgL(-1) for mineral oil and 3.4 and 11.2μgL(-1) for silicone. We applied this method to determine arsenic in five commercial sugarcane brandy samples. The results agreed well with those obtained by hydride generation combined with atomic absorption spectrometry (HG AAS). Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. Styrene-butadiene rubber/halloysite nanotubes nanocomposites modified by methacrylic acid

    International Nuclear Information System (INIS)

    Guo Baochun; Lei Yanda; Chen Feng; Liu Xiaoliang; Du Mingliang; Jia Demin

    2008-01-01

    Methacrylic acid (MAA) was used to improve the performance of styrene-butadiene rubber (SBR)/halloysite nanotubes (HNTs) nanocomposites by direct blending. The detailed interaction mechanisms of MAA and the in situ formed zinc methacrylate (ZDMA) were revealed by X-ray diffraction (XRD), surface area and porosity analysis, X-ray photoelectron spectroscopy (XPS) together with crosslink density determination. The strong interfacial bonding between HNTs and rubber matrix is resulted through ZDMA and MAA intermediated linkages. ZDMA connects SBR and HNTs via grafting/complexation mechanism. MAA bonds SBR and HNTs through grafting/hydrogen bonding mechanism. Significantly improved dispersion of HNTs in virtue of the interactions between HNTs and MAA or ZDMA was achieved. Effects of MAA content on the vulcanization behavior, morphology and mechanical properties of the nanocomposites were investigated. Promising mechanical properties of MAA modified SBR/HNTs nanocomposites were obtained. The changes in vulcanization behavior, mechanical properties and morphology were correlated with the interactions between HNTs and MAA or ZDMA and the largely improved dispersion of HNTs

  2. Styrene-butadiene rubber/halloysite nanotubes nanocomposites modified by methacrylic acid

    Energy Technology Data Exchange (ETDEWEB)

    Guo Baochun [Department of Polymer Materials and Engineering, South China University of Technology, Guangzhou 510640 (China)], E-mail: psbcguo@scut.edu.cn; Lei Yanda; Chen Feng; Liu Xiaoliang; Du Mingliang; Jia Demin [Department of Polymer Materials and Engineering, South China University of Technology, Guangzhou 510640 (China)

    2008-12-30

    Methacrylic acid (MAA) was used to improve the performance of styrene-butadiene rubber (SBR)/halloysite nanotubes (HNTs) nanocomposites by direct blending. The detailed interaction mechanisms of MAA and the in situ formed zinc methacrylate (ZDMA) were revealed by X-ray diffraction (XRD), surface area and porosity analysis, X-ray photoelectron spectroscopy (XPS) together with crosslink density determination. The strong interfacial bonding between HNTs and rubber matrix is resulted through ZDMA and MAA intermediated linkages. ZDMA connects SBR and HNTs via grafting/complexation mechanism. MAA bonds SBR and HNTs through grafting/hydrogen bonding mechanism. Significantly improved dispersion of HNTs in virtue of the interactions between HNTs and MAA or ZDMA was achieved. Effects of MAA content on the vulcanization behavior, morphology and mechanical properties of the nanocomposites were investigated. Promising mechanical properties of MAA modified SBR/HNTs nanocomposites were obtained. The changes in vulcanization behavior, mechanical properties and morphology were correlated with the interactions between HNTs and MAA or ZDMA and the largely improved dispersion of HNTs.

  3. Styrene-butadiene rubber/halloysite nanotubes nanocomposites modified by sorbic acid

    Energy Technology Data Exchange (ETDEWEB)

    Guo Baochun, E-mail: psbcguo@scut.edu.cn [Department of Polymer Materials and Engineering, South China University of Technology, Guangzhou 510640 (China); Chen Feng; Lei Yanda; Liu Xiaoliang; Wan Jingjing; Jia Demin [Department of Polymer Materials and Engineering, South China University of Technology, Guangzhou 510640 (China)

    2009-05-30

    Sorbic acid (SA) was used to improve the performance of styrene-butadiene rubber (SBR)/halloysite nanotubes (HNTs) nanocomposites by direct blending. The detailed mechanisms for the largely improved performance were studied by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), differential scanning calorimetry (DSC), porosity analysis and crosslink density determination. The strong interfacial bonding between HNTs and rubber matrix is resulted through SA intermediated linkages. SA bonds SBR and HNTs through grafting copolymerization/hydrogen bonding mechanism. Significantly improved dispersion of HNTs in virtue of the interactions between HNTs and SA was achieved. Formation of zinc disorbate (ZDS) was revealed during the vulcanization of the composites. However, in the present systems, the contribution of ZDS to the reinforcement was limited. Effects of SA content on the vulcanization behavior, morphology and mechanical properties of the nanocomposites were investigated. Promising mechanical properties of SA modified SBR/HNTs nanocomposites were obtained. The changes in vulcanization behavior, mechanical properties and morphology were correlated with the interactions between HNTs and SA and the largely improved dispersion of HNTs.

  4. Enhancement of Capacitive Performance in Titania Nanotubes Modified by an Electrochemical Reduction Method

    Directory of Open Access Journals (Sweden)

    Nurul Asma Samsudin

    2018-01-01

    Full Text Available Highly ordered titania nanotubes (TNTs were synthesised by an electrochemical anodization method for supercapacitor applications. However, the capacitive performance of the TNTs was relatively low and comparable to the conventional capacitor. Therefore, in order to improve the capacitive performance of the TNTs, a fast and facile electrochemical reduction method was applied to modify the TNTs (R-TNTs by introducing oxygen vacancies into the lattice. X-ray photoelectron spectroscopy (XPS data confirmed the presence of oxygen vacancies in the R-TNTs lattice upon the reduction of Ti4+ to Ti3+. Electrochemical reduction parameters such as applied voltage and reduction time were varied to optimize the best conditions for the modification process. The electrochemical performance of the samples was analyzed in a three-electrode configuration cell. The cyclic voltammogram recorded at 200 mV s−1 showed a perfect square-shaped voltammogram indicating the excellent electrochemical performance of R-TNTs prepared at 5 V for 30 s. The total area of the R-TNTs voltammogram was 3 times larger than the unmodified TNTs. A specific capacitance of 11.12 mF cm−2 at a current density of 20 μA cm−2 was obtained from constant current charge-discharge measurements, which was approximately 57 times higher than that of unmodified TNTs. R-TNTs also displayed outstanding cycle stability with 99% capacity retention after 1000 cycles.

  5. Anodic stripping voltammetric determination of silver ion at a carbon paste electrode modified with carbon nanotubes

    International Nuclear Information System (INIS)

    Tashkhourian, J.; Javadi, S.; Ana, F.N.

    2011-01-01

    A carbon paste electrode (CPE) was modified with multi-wall carbon nanotubes and successfully applied to the determination of silver ion by differential pulse anodic stripping voltammetry. Compared to a conventional CPE, a remarkably improved peak current response and sensitivity is observed. The analytical procedure consisted of an open circuit accumulation step for 2 min in -0.4 V, this followed by an anodic potential scan between +0.2 and + 0.6 V to obtain the voltammetric peak. The oxidation peak current is proportional to the concentration of silver ion in the range from 1.0 x 10 -8 to 1.0 x 10 -5 mol L -1 , with a detection limit of 1.8 x 10 -9 mol L -1 after an accumulation time of 120 s. The relative standard deviation for 7 successive determinations of Ag(I) at 0.1 μM concentration is 1.99%. The procedure was validated by determining Ag(I) in natural waters. (author)

  6. Carbon nanotubes paste sensor modified with bismuth film for determination of metallic ions in ethanol fuel

    Directory of Open Access Journals (Sweden)

    Felipe Augusto Gorla

    2015-05-01

    Full Text Available In the present study an anodic stripping voltammetric method using a bismuth film modified carbon nanotubes paste electrode for simultaneous determination of metals Zn2+, Cd2+and Pb2+in ethanol fuel is described. The metallic ions were preconcentrated on the bismuth film in the time and deposition potential of 500 s and -1.2 V and the stripping step was carried out by square wave voltammetry (frequency of 15 Hz, pulse amplitude of 25 mV and potential step of 5 mV. Acetate buffer at 0.1 mol L-1concentration and pH 4.5 was used as support electrolyte. The method showed linearity including the analytical blank up to 48.39 ?g L-1 for the metals and the obtained limits of detection were 3.36, 0.32 and 0.47 ?g L-1for Zn2+, Cd2+and Pb2+, respectively. The proposed method was applied in ethanol fuel samples.

  7. Electrochemical Treatment of Wastewater Containing Mixed Reactive Dyes Using Carbon Nanotube Modified Cathode Electrodes

    Directory of Open Access Journals (Sweden)

    Nader Djafarzadeh

    2016-11-01

    Full Text Available Nowadays, advanced electrochemical oxidation processes are promising methods for the treatment of wastewaters containing organic dyes. One of these methods is the Electro-Fenton (EF technique in which an electrical current is applied to the cathode and anode electrodes to promote electrochemical reactions that generate hydroxyl radicals which mineralize organic pollutants and remove them from wastewater. To carry out the Electro-Fenton process iIn this work, the carbon paper (CP electrode was initially modified with carbon nanotubes (CNT to produce the CP-CNT electrode which was used as the cathode to remove a mixture of organic dyestuff (containing Reactive Blue 69, Reactive Red 195, and Reactive Yellow 84 from wastewaters. Comparison of the two types of cathode electrodes (i.e., CNT and the modified CP-CNT showed that the CP-CNT outperformed the CP electrode. The EF process was employed to treat 500 ml of a mixture of dyes (50 mg/L of each dye containing sodium soulfate and Fe+3 ions. The results revealed that the highest color removal efficiency was achieved when a current of 300 mA was applied for 210 min. COD measurments were used to calculate the effective current and power consumption. It was found that the 300 mA current applied over a period of 210 min yielded the highest effective current and the lowest power consumption. The amount of dyes mineralized by the EF process in the dye solution indicated that 78% of the initial COD had been removed under the above conditions. It may be concluded that the Electro-Fenton process can be successfully used for the treatment of wastewaters containing mixtures of dye pollutants. Cathode electrode type, electrical current, and electrolysis duration were identified as the parameters affecting the process.

  8. Biosensor for pesticide triazophos based on its inhibition of acetylcholinesterase and using a glassy carbon electrode modified with coral-like gold nanostructures supported on reduced graphene oxide

    International Nuclear Information System (INIS)

    Ju, Ke-Jian; Feng, Jin-Xia; Zhang, Qian-Li; Xu, Tian-Qi; Wei, Jie; Feng, Jiu-Ju; Wang, Ai-Jun

    2015-01-01

    A nanocomposite consisting of coral-like gold nanostructures on reduced graphene oxide (RGO) was synthesized with the assistance of dimethylbiguanide (DMBG). It was then fabricated on a glassy carbon electrode, coating with cysteamine in order to enable the immobilization of acetylcholinesterase (AChE) as a model enzyme whose activity of hydrolyzing the substrate of acetylthiocholine is inhibited by the pesticide triazophos. The biosensor has response to acetylthiocholine in the 0.3 ∼ 300 μM concentration range at 0.65 V (vs. SCE). The inhibition of the enzyme by triazophos can be determined in concentrations of up to 210 ppb, with a detection limit of 0.35 ppb of triazophos (S/N = 3). The biosensor is highly reproducible and acceptably stable. (author)

  9. Amperometric sensing of nitrite using a glassy carbon electrode modified with a multilayer consisting of carboxylated nanocrystalline cellulose and poly(diallyldimethyl ammonium) ions in a PEDOT host

    International Nuclear Information System (INIS)

    Xu, Guiyun; Liang, Shaoping; Sheng, Ge; Luo, Xiliang; Fan, Jinshi

    2016-01-01

    Negatively charged carboxylated nanocrystalline cellulose (CNCC) and positively charged poly(diallyldimethyl ammonium chloride) (PDDA) were alternatingly assembled on the surface of a glassy carbon electrode to form a relatively uniform polyelectrolyte multilayer nanocomposite (CNCC/PDDA)n. It was then incorporated into a matrix of conducting poly(3,4-ethylenedioxythiophene) (PEDOT) electrodeposited on the surface of the electrode. The nanocomposites were prepared in various ratios of PEDOT and (CNCC/PDDA), and then characterized by transmission electron microscopy, scanning electron microscopy, electrochemical impedance spectroscopy, cyclic voltammetry, and differential pulse voltammetry. The PEDOT/(CNCC/PDDA)4 nanocomposite showed the lowest electrochemical impedance and best electrocatalytic activity towards the oxidation of nitrite. Based on these findings, an amperometric sensor was developed which, if operated at 0.80 V (vs. SCE), can detect nitrite in the 0.2 μM to 1.73 mM concentration range with a 57 nM detection limit. (author)

  10. A glassy carbon electrode modified with a composite consisting of reduced graphene oxide, zinc oxide and silver nanoparticles in a chitosan matrix for studying the direct electron transfer of glucose oxidase and for enzymatic sensing of glucose

    International Nuclear Information System (INIS)

    Li, Zhenjiang; Sheng, Liying; Xie, Cuicui; Meng, Alan; Zhao, Kun

    2016-01-01

    The authors describe the fabrication of a nanocomposite consisting of reduced graphene oxide, zinc oxide and silver nanoparticles by microwave-assisted synthesis. The composite was further reduced in-situ with hydrazine hydrate and then placed, along with the enzyme glucose oxidase, on a glassy carbon electrode. The synergistic effect of the materials employed in the nanocomposite result in excellent electrocatalytic activity. The Michaelis-Menten constant of the adsorbed GOx is 0.25 mM, implying a remarkable affinity of the GOx for glucose. The amperometric response of the modified GCE is linearly proportional to the concentration of glucose in 0.1 to 12.0 mM concentration range, and the detection limit is 10.6 µM. The biosensor is highly selective, well reproducible and stable. (author)

  11. Simultaneous determination of cysteine, uric acid and tyrosine using Au-nanoparticles/poly(E)-4-(p-tolyldiazenyl)benzene-1,2,3-triol film modified glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Taei, M., E-mail: m.taei@ch.iut.ac.ir; Hasanpour, F.; Salavati, H.; Banitaba, S.H.; Kazemi, F.

    2016-02-01

    A novel Au nanoparticles/poly(E)-4-(p-tolyldiazenyl)benzene-1,2,3-triol (AuNPs/PTAT) film modified glassy carbon electrode (AuNPs/PTAT/GCE) was fabricated for the simultaneous determination of three antioxidants named, cysteine (Cys), uric acid (UA) and tyrosine (Tyr). The bare glassy carbon electrode (GCE) fails to separate the oxidation peak potentials of these molecules, while PTAT film modified electrode can resolve them. Electrochemical impedance spectroscopy (EIS) study indicates that the charge transfer resistance of bare electrode increased as (E)-4-(p-tolyldiazenyl)benzene-1,2,3-triol was electropolymerized at the bare electrode. Furthermore, EIS exhibits enhancement of electron transfer kinetics between analytes and electrode after electrodeposition of Au nanoparticles. Differential pulse voltammetry results show that the electrocatalytic current increases linearly in the ranges of 2–540 μmol L{sup −1} for Cys, 5–820 μmol L{sup −1} for UA and 10–560 μmol L{sup −1} for Tyr with detection limits (S/N = 3) of 0.04 μmol L{sup −1}, 0.1 μmol L{sup −1} and 2 μmol L{sup −1} for Cys, UA and Tyr, respectively. The proposed method was successfully applied for simultaneous determination of Cys, UA and Tyr in human urine samples. - Highlights: • AuNPs/PTAT/GCE was fabricated by electrodeposition and electropolymerization. • The sensor reduced the overpotential for oxidation of Cys. • This electrode was successfully used for simultaneous sensing of Cys, UA and Tyr. • This sensor was effectively used for detection Cys, UA and Tyr in real samples.

  12. Use of modified halloysite nanotubes in the feed reduces the toxic effects of zearalenone on sow reproduction and piglet development.

    Science.gov (United States)

    Zhang, Yuanyuan; Gao, Rui; Liu, Min; Shi, Baoming; Shan, Anshan; Cheng, Baojing

    2015-03-15

    A study was conducted to determine the effects of feeding a blend of corn contaminated with Fusarium mycotoxins on the physical condition of pregnant and suckling sows and the development of their offspring. Halloysite nanotubes modified using the surfactant, stearyldimethylbenzylammonium chloride, were tested for its efficacy in protecting against the detrimental effects of zearalenone (ZEN) exposure. A total of 18 pregnant second parity Yorkshire sows (six per treatment) were fed control diet, contaminated grain diet (ZEN, 2.77 mg/kg), and contaminated grain + 1% modified halloysite nanotube (MHNT) diet (ZEN, 2.76 mg/kg) from 35 to 70 days in pregnancy (DIP), which is the critical period in development of fetuses. The results show that consumption of ZEN led to a reduction in sow's mass gain during 35 to 70 DIP and mass at 110 DIP, backfat at 70 DIP and weaning, placenta weight at 70 DIP and farrowing, the lactation average daily feed intake, and an increase in the weight of ovary at 70 DIP of sows (P halloysite nanotubes could be used as adsorbent in the feed to reduce the toxic effects of ZEN. Copyright © 2015 Elsevier Inc. All rights reserved.

  13. Polyoxometalate-modified TiO2 nanotube arrays photoanode materials for enhanced dye-sensitized solar cells

    Science.gov (United States)

    Liu, Ran; Sun, Zhixia; Zhang, Yuzhuo; Xu, Lin; Li, Na

    2017-10-01

    In this work, we prepared for the first time the TiO2 nanotube arrays (TNAs) photoanode with polyoxometalate(POMs)-modified TiO2 electron-transport layer for improving the performance of zinc phthalocyanine(ZnPc)-sensitized solar cells. The as-prepared POMs/TNAs/ZnPc composite photoanode exhibited higher photovoltaic performances than the TNAs/ZnPc photoanode, so that the power conversion efficiency of the solar cell device based on the POMs/TNAs/ZnPc photoanode displayed a notable improvement of 45%. These results indicated that the POMs play a key role in reducing charge recombination in phthalocyanine-sensitized solar cells, together with TiO2 nanotube arrays being helpful for electron transport. The mechanism of the performance improvement was demonstrated by the measurements of electrochemical impedance spectra and open-circuit voltage decay curves. Although the resulting performance is still below that of the state-of-the-art dye-sensitized solar cells, this study presents a new insight into improving the power conversion efficiency of phthalocyanine-sensitized solar cells via polyoxometalate-modified TiO2 nanotube arrays photoanode.

  14. Bonding Characteristics of Macrosynthetic Fiber in Latex-Modified Fiber-Reinforced Cement Composites as a Function of Carbon Nanotube Content

    Directory of Open Access Journals (Sweden)

    Ji-Hong Jean

    2016-01-01

    Full Text Available The effect of carbon nanotube content (0, 0.5, 1.0, 1.5, and 2.0% of the cement weight on the bonding properties of macrosynthetic fiber in latex-modified hybrid fiber cement-based composites (LMHFRCCs was evaluated. The slump value, compressive strength, and bonding strength were measured for each LMHFRCC. As the carbon nanotube content increased to 1.5%, the bonding properties of the macrosynthetic fiber improved. However, the bonding performance deteriorated at a carbon nanotube content of 2.0%. A decrease in the fluidity of the mix negatively affected the dispersion of the nanotubes in the LMHFRCCs. The addition of carbon nanotubes also affected the relative bonding strength independently of the improvement in compressive strength. Microscopic analysis of the macrosynthetic fiber surfaces was used to understand changes in the bonding behavior.

  15. Determination of Patulin Using Amperometric Tyrosinase Biosensors Based on Electrodes Modified with Carbon Nanotubes and Gold Nanoparticles

    Directory of Open Access Journals (Sweden)

    R.M. Varlamova

    2016-06-01

    Full Text Available New amperometric biosensors based on platinum screen printed electrodes modified with multi-walled carbon nanotubes, gold nanoparticles, and immobilized enzyme – tyrosinase have been developed for determination of patulin in the concentrations of 1·10–6 – 8·10–12 mol/L with an error of no more than 0.063. The best conditions for obtaining gold nanoparticles have been chosen. The conditions for immobilization of multi-walled carbon nanotubes and gold nanoparticles on the surface of the planar electrode have been revealed. The conditions for functioning of the proposed biosensors have been identified. The results have been used to control the content of patulin in food products within and lower than the maximum allowable levels.

  16. Highly selective and sensitive detection of neurotransmitters using receptor-modified single-walled carbon nanotube sensors

    Science.gov (United States)

    Kim, Byeongju; Song, Hyun Seok; Jin, Hye Jun; Park, Eun Jin; Lee, Sang Hun; Lee, Byung Yang; Park, Tai Hyun; Hong, Seunghun

    2013-07-01

    We present receptor-modified carbon nanotube sensors for the highly selective and sensitive detection of acetylcholine (ACh), one kind of neurotransmitter. Here, we successfully expressed the M1 muscarinic acetylcholine receptor (M1 mAChR), a family of G protein-coupled receptors (GPCRs), in E. coli and coated single-walled carbon nanotube (swCNT)-field effect transistors (FETs) with lipid membrane including the receptor, enabling highly selective and sensitive ACh detection. Using this sensor, we could detect ACh at 100 pM concentration. Moreover, we showed that this sensor could selectively detect ACh among other neurotransmitters. This is the first demonstration of the real-time detection of ACh using specific binding between ACh and M1 mAChR, and it may lead to breakthroughs for various applications such as disease diagnosis and drug screening.

  17. Highly selective and sensitive detection of neurotransmitters using receptor-modified single-walled carbon nanotube sensors

    International Nuclear Information System (INIS)

    Kim, Byeongju; Jin, Hye Jun; Park, Eun Jin; Hong, Seunghun; Song, Hyun Seok; Lee, Sang Hun; Park, Tai Hyun; Lee, Byung Yang

    2013-01-01

    We present receptor-modified carbon nanotube sensors for the highly selective and sensitive detection of acetylcholine (ACh), one kind of neurotransmitter. Here, we successfully expressed the M1 muscarinic acetylcholine receptor (M1 mAChR), a family of G protein-coupled receptors (GPCRs), in E. coli and coated single-walled carbon nanotube (swCNT)-field effect transistors (FETs) with lipid membrane including the receptor, enabling highly selective and sensitive ACh detection. Using this sensor, we could detect ACh at 100 pM concentration. Moreover, we showed that this sensor could selectively detect ACh among other neurotransmitters. This is the first demonstration of the real-time detection of ACh using specific binding between ACh and M1 mAChR, and it may lead to breakthroughs for various applications such as disease diagnosis and drug screening. (paper)

  18. Synthesis and CO2 adsorption study of modified MOF-5 with multi-wall carbon nanotubes and expandable graphite

    International Nuclear Information System (INIS)

    Ullah, Sami; Bustam, M. A.; Shariff, A. M.; Elkhalifah, Ali E. I.; Murshid, G.; Riaz, Nadia

    2014-01-01

    MOF-5 was synthesized by solvothermal method and its reactivation under anhydrous conditions. This research is conducted to investigate the effect of MOF-5 and MOF-5 modified with multi-wall carbon nanotubes (MWCNTs) and expandable graphite (EG) on the performance of CO 2 adsorption. The synthesized MOFs were characterized using Field emission scanning electron microscopy (FESEM) for surface morphology, Thermogravimetric analysis (TGA) for thermal stability, X-ray diffraction (XRD) for crystals plane, Brunauer-Emmet-Teller (BET) for surface area and CO 2 adsorption. The result had showed that the modified MOF-5 enhanced the CO 2 adsorption compared to the pure MOF-5. The increment in the CO 2 uptake capacities of MOF materials was attributed to the decrease in the pore size and enhancement of micropore volume of MOF-5 by multi-walled carbon nanotube and EG incorporation. The BET surface area of the synthesized MOF-5@MWCNTs is more than MOF-5. The CO 2 sorption capacities of MOF-5 and MOF-5@MWCNTs were observed to increase from 0.00008 to 0.00048 mol g-1 at 298 K and 1 bar. The modified MOF-5@MWCNTs resulted in the highest CO 2 adsorption followed by the modified MOF-5@ EG and lastly, MOF-5

  19. Photoelectrocatalytic reduction of CO2 into chemicals using Pt-modified reduced graphene oxide combined with Pt-modified TiO2 nanotubes.

    Science.gov (United States)

    Cheng, Jun; Zhang, Meng; Wu, Gai; Wang, Xin; Zhou, Junhu; Cen, Kefa

    2014-06-17

    The photoelectrocatalytic (PEC) reduction of CO2 into high-value chemicals is beneficial in alleviating global warming and advancing a low-carbon economy. In this work, Pt-modified reduced graphene oxide (Pt-RGO) and Pt-modified TiO2 nanotubes (Pt-TNT) were combined as cathode and photoanode catalysts, respectively, to form a PEC reactor for converting CO2 into valuable chemicals. XRD, XPS, TEM, AFM, and SEM were employed to characterize the microstructures of the Pt-RGO and Pt-TNT catalysts. Reduction products, such as C2H5OH and CH3COOH, were obtained from CO2 under band gap illumination and biased voltage. A combined liquid product generation rate (CH3OH, C2H5OH, HCOOH, and CH3COOH) of approximately 600 nmol/(h·cm(2)) was observed. Carbon atom conversion rate reached 1,130 nmol/(h·cm(2)), which were much higher than those achieved using Pt-modified carbon nanotubes and platinum carbon as cathode catalysts.

  20. High performance natural rubber composites with a hierarchical reinforcement structure of carbon nanotube modified natural fibers

    International Nuclear Information System (INIS)

    Tzounis, Lazaros; Debnath, Subhas; Rooj, Sandip; Fischer, Dieter; Mäder, Edith; Das, Amit; Stamm, Manfred; Heinrich, Gert

    2014-01-01

    A simple and facile method for depositing multiwall carbon nanotubes (MWCNTs) onto the surface of naturally occurring short jute fibers (JFs) is reported. Hierarchical multi-scale structures were formed with CNT-networks uniformly distributed and fully covering the JFs (JF–CNT), as depicted by the scanning electron microscopy (SEM) micrographs. The impact of these hybrid fillers on the mechanical properties of a natural rubber (NR) matrix was systematically investigated. Pristine JFs were cut initially to an average length of 2.0 mm and exposed to an alkali treatment (a-JFs) to remove impurities existing in the raw jute. MWCNTs were treated under mild acidic conditions to generate carboxylic acid moieties. Afterward, MWCNTs were dispersed in an aqueous media and short a-JFs were allowed to react with them. Raman spectroscopy confirmed the chemical interaction between CNTs and JFs. The JF–CNT exposed quite hydrophobic behavior as revealed by the water contact angle measurements, improving the wettability of the non-polar NR. Consequently, the composite interfacial adhesion strength was significantly enhanced while a micro-scale “mechanical interlocking” mechanism was observed from the interphase-section transmission electron microscopy (TEM) images. SEM analysis of the composite fracture surfaces demonstrated the interfacial strength of NR/a-JF and NR/JF–CNT composites, at different fiber loadings. It can be presumed that the CNT-coating effectively compatibillized the composite structure acting as a macromolecular coupling agent. A detailed analysis of stress-strain and dynamic mechanical spectra confirmed the high mechanical performance of the hierarchical composites, consisting mainly of materials arising from natural resources. - Highlights: • Natural rubber (NR) composites reinforced with CNT-modified short jute fibers. • MWCNTs deposited to the surface of jute fibers via non-covalent interactions. • Hierarchical reinforcement structure with

  1. Application of modified multiwall carbon nanotubes as a sorbent for zirconium (IV) adsorption from aqueous solution

    International Nuclear Information System (INIS)

    Yavari, R.; Davarkhah, R.

    2013-01-01

    Modified multiwall carbon nanotubes (MWCNTs) by nitric acid solution were used to investigate the adsorption behavior of zirconium from aqueous solution. Pristine and oxidized MWCNTs were characterized using nitrogen adsorption/desorption isotherm, Boehm's titration method, thermogravimetry analysis, transmission electron microscopy and Fourier transform infrared spectroscopy. The results showed that the surface properties of MWCNTs such as specific surface area, total pore volume, functional groups and the total number of acidic and basic sites were improved after oxidation. These improvements are responsible for their hydrophobic properties and consequently an easy dispersion in water and suitable active sites for more adsorption of zirconium. The adsorption of Zr(IV) as a function of initial concentration of zirconium, contact time, MWCNTs dosage, HCl and HNO 3 concentration and also ionic strength was investigated using a batch technique under ambient conditions. The experimental results indicated that sorption of Zr(IV) was strongly influenced by zirconium concentrations, oxidized MWCNTs content and acid pH values. The calculated correlation coefficient of the linear regressions values showed that Langmuir model fits the adsorption equilibrium data better than the Freundlich model. Kinetic data of sorption indicated that equilibrium was achieved within 60 min and the adsorption process can be described by the pseudo second-order reaction rate model. Based on the experimental results, surface complexation is the major mechanism for adsorption of Zr(IV) onto MWCNTs. Also, Study on the desorption process of zirconium showed that the complete recovery can be obtained using nitric or hydrochloric acids of 4 M. (author)

  2. Voltammetric determination of paracetamole using a glassy carbon electrode modified with Prussian Blue and a molecularly imprinted polymer, and ratiometric read-out of two signals

    International Nuclear Information System (INIS)

    Dai, Yunlong; Li, Xueyan; Lu, Xiaojing; Kan, Xianwen

    2016-01-01

    The authors report on a ratiometric electrochemical sensor for paracetamole (PR) which was fabricated by successively electropolymerizing a layer of Prussian blue (PB) and a layer of molecularly imprinted polypyrrole (MIP) on the surface of a glassy carbon electrode (GCE). The binding of PR molecules to the MIP has two effects: The first is an increase of the oxidation current for PR at 0.42 V (vs. SCE), and the second is a decrease in the current for PB (at 0.18 V) due to partial blocking of the channels which results in reduced electron transmissivity. Both currents, and in particular their ratio, can serve as analytical information. Under optimized conditions, the sensor displays enhanced sensitivity for PR in the 1.0 nM to 0.1 mM concentration range and a 0.53 nM lower limit of detection. The sensor was applied to the determination of PR in tablets and urines where it gave recoveries in the range between 94.6 and 104.9 %. This dual-signal (ratiometric) detection scheme (using electro polymerized Prussian Blue and analyte-specific MIP) in our perception has a wide scope in that it may be applied to numerous other electro active species for which specific MIP can be made available. (author)

  3. Molecularly imprinted poly(4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid) modified glassy carbon electrode as an electrochemical theophylline sensor.

    Science.gov (United States)

    Aswini, K K; Vinu Mohan, A M; Biju, V M

    2016-08-01

    Theophylline is an inexpensive drug employed in asthma and chronic obstructive pulmonary disorder medications and is toxic at higher concentration. The development of a molecularly imprinted polymer based theophylline electrochemical sensor on glassy carbon electrode by the electropolymerization of 4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid is being discussed in this work. The MIP modification enhances the theophylline recognition ability and the electron transfer kinetics of the bare electrode. The parameters, controlling the performance of the imprinted polymer based sensor, like number of electropolymerization cycles, composition of the pre-polymerization mixture, pH and immersion time were investigated and optimized. The interaction energy and the most stable conformation of the template-monomer complex in the pre-polymerization mixture were determined computationally using ab initio calculations based on density functional theory. The amperometric measurements showed that the developed sensor has a method detection limit of 0.32μM for the dynamic range of 0.4 to 17μM, at optimized conditions. The transducer possesses appreciable selectivity in the presence of structurally similar interferents such as theobromine, caffeine and doxofylline. The developed sensor showed remarkable stability and reproducibility and was also successfully employed in theophylline detection from commercially available tablets. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Voltammetric Determination of Meloxicam in Pharmaceutical Formulation and Human Serum at Glassy Carbon Electrode Modified by Cysteic Acid Formed by Electrochemical Oxidation of L-cysteine

    Directory of Open Access Journals (Sweden)

    Xiao Ya Hu

    2005-09-01

    Full Text Available The improvement of electrochemical detection of meloxicam is presented bymodification of a glassy carbon electrode with anionic layer of cysteic acid providingelectrostatic accumulation of the analyte onto the electrode surface. The modificationformed by electrochemical oxidation of L-cysteine was performed by cycling potential incysteine solution. The anodic peak current obtained at 1.088 V (vs. Ag/AgCl byvoltammetry was linearly dependent on the meloxicam concentration in the range of 4.3 ×10-8 ~ 8.5 × 10-6 M in the B-R buffer solution (0.04 M, pH 1.86 with a correlationcoefficient of 0.999. The detection limit (S/N = 3 is 1.5 × 10-9 M. The low-cost modifiedelectrode shows good sensitivity, selectivity and stability and has been applied to thedetermination of meloxicam in pharmaceutical formulation and spiked serum withsatisfactory results. The electrochemical reaction mechanism of meloxicam was discussed.

  5. A novel lable-free electrochemical immunosensor for carcinoembryonic antigen based on gold nanoparticles-thionine-reduced graphene oxide nanocomposite film modified glassy carbon electrode.

    Science.gov (United States)

    Kong, Fen-Ying; Xu, Mao-Tian; Xu, Jing-Juan; Chen, Hong-Yuan

    2011-10-15

    In this paper, gold nanoparticle-thionine-reduced graphene oxide (GNP-THi-GR) nanocomposites were prepared to design a label-free immunosensor for the sensitive detection of carcinoembryonic antigen (CEA). The nanocomposites with good biocompatibility, excellent redox electrochemical activity and large surface area were coated onto the glassy carbon electrode (GCE) surface and then CEA antibody (anti-CEA) was immobilized on the electrode to construct the immunosensor. The morphologies and electrochemistry of the formed nanocomposites were investigated by using scanning electron microscopy (SEM), ultraviolet-visible (UV-vis) spectrometry, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). CV and differential pulse voltammetry (DPV) studies demonstrated that the formation of antibody-antigen complexes decreased the peak current of THi in the GNP-THi-GR nanocomposites. The decreased currents were proportional to the CEA concentration in the range of 10-500 pg/mL with a detection limit of 4 pg/mL. The proposed method was simple, fast and inexpensive for the determination of CEA at very low levels. Copyright © 2011 Elsevier B.V. All rights reserved.

  6. Amperometric biosensor for total monoamines using a glassy carbon paste electrode modified with human monoamine oxidase B and manganese dioxide particles

    International Nuclear Information System (INIS)

    Aigner, Maximilian; Telsnig, Dietlind; Teubl, Christian; Ortner, Astrid; Kalcher, Kurt; Macheroux, Peter; Wallner, Silvia; Edmondson, Dale

    2015-01-01

    We have prepared a biosensor for the determination of the total monoamine content in complex matrices by immobilizing a human monoamine oxidase B (hMAO B) on a glassy carbon paste electrode and adding manganese dioxide microparticles as the mediator. The enzyme hMAO B (expressed in Pichia pastoris and immobilized by using a dialysis membrane) catalyzes the oxidative deamination of monoamines, and this results in the formation of the corresponding aldehyde, ammonia and hydrogen peroxide. The latter was detected at pH 7.5 at a working voltage of 400 mV (vs. Ag/AgCl) by differential pulse voltammetry and amperometrically by applying flow injection analysis. Analytical parameters were established by using phenylethylamine (PEA) as a standard substrate. Peak height and concentration of PEA are linearly related in the 0.5 to 150 μg mL −1 concentration range, and the limits of detection and of quantification are 0.15 and 0.5 μg mL −1 of PEA, respectively. Substrate specificity was investigated with different monoamines including PEA, serotonin, benzylamine, dopamine, tyramine, and norepinephrine. The applicability of the biosensor was successfully tested in a commercial fish sauce that served as a complex matrix. The total monoamine content was calculated as PEA-equivalents. (author)

  7. TiO{sub 2}-based nanotubes modified with nickel: synthesis, properties, and improved photocatalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    Qamar, M; Ganguli, A K [Department of Chemistry, Indian Institute of Technology, Hauz Khas, New Delhi 110016 (India); Kim, S J, E-mail: sjkim1@sejong.ac.k, E-mail: ashok@chemistry.iitd.ac.i [Department of Nano Science and Technology, Sejong Advanced Institute of Nano Technologies, Sejong University, 98, Gunja-dong, Gwangjin-gu, Seoul 143-747 (Korea, Republic of)

    2009-11-11

    Titanate nanotubes containing 2.5 wt% Ni were synthesized from TiO{sub 2} sol using alkali hydrothermal treatment followed by a simple ion-exchange process. The changes in phase, shape and morphology, surface area, and photocatalytic activity of these nanotubes have been explored as a function of calcination temperature. The samples were characterized using standard techniques, including x-ray diffraction, transmission electron microscopy, scanning electron microscopy, inductively coupled plasma spectrometry, energy dispersive x-ray spectroscopy, and Brauner-Emmett-Teller surface area analysis. The study revealed that the titanate phase containing Ni ions can be converted to the anatase phase after certain heat treatments but, at the same time, the tubular morphology was partially lost. Investigation of photocatalytic properties demonstrated that the as-prepared Ni-titanate nanotubes were photocatalytically inactive, but when heated at temperatures below 500 {sup 0}C their activity was significantly enhanced with the change in phase. The calcined nanotube samples carrying nickel ion showed better photocatalytic activity than calcined nanotube samples containing protons. The hydrogen adsorption capacity of these titanates has also been measured, and it was found that Ni-titanate nanotubes can adsorb more hydrogen than its counterpart Na-titanate.

  8. Amperometric sensor for detection of bisphenol A using a pencil graphite electrode modified with polyaniline nanorods and multiwalled carbon nanotubes

    International Nuclear Information System (INIS)

    Poorahong, S.; Thammakhet, C.; Numnuam, A.; Kanatharana, P.; Thavarungkul, P.; Limbut, W.

    2012-01-01

    We report on a simple and highly sensitive amperometric method for the determination of bisphenol A (BPA) using pencil graphite electrodes modified with polyaniline nanorods and multiwalled carbon nanotubes. The modified electrodes display enhanced electroactivity for the oxidation of BPA compared to the unmodified pencil graphite electrode. Under optimized conditions, the sensor has a linear response to BPA in the 1. 0 and 400 μM concentration range, with a limit of detection of 10 nM (at S/N = 3). The modified electrode also has a remarkably stable response, and up to 95 injections are possible with a relative standard deviation of 4. 2% at 100 μM of BPA. Recoveries range from 86 to 102% for boiling water spiked with BPA from four brands of baby bottles. (author)

  9. Ferromagnetic bulk glassy alloys

    International Nuclear Information System (INIS)

    Inoue, Akihisa; Makino, Akihiro; Mizushima, Takao

    2000-01-01

    This paper deals with the review on the formation, thermal stability and magnetic properties of the Fe-based bulk glassy alloys in as-cast bulk and melt-spun ribbon forms. A large supercooled liquid region over 50 K before crystallization was obtained in Fe-(Al, Ga)-(P, C, B, Si), Fe-(Cr, Mo, Nb)-(Al, Ga)-(P, C, B) and (Fe, Co, Ni)-Zr-M-B (M=Ti, Hf, V, Nb, Ta, Cr, Mo and W) systems and bulk glassy alloys were produced in a thickness range below 2 mm for the Fe-(Al, Ga)-(P, C, B, Si) system and 6 mm for the Fe-Co-(Zr, Nb, Ta)-(Mo, W)-B system by copper-mold casting. The ring-shaped glassy Fe-(Al, Ga)-(P, C, B, Si) alloys exhibit much better soft magnetic properties as compared with the ring-shaped alloy made from the melt-spun ribbon because of the formation of the unique domain structure. The good combination of high glass-forming ability and good soft magnetic properties indicates the possibility of future development as a new bulk glassy magnetic material

  10. Molecularly imprinted poly(4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid) modified glassy carbon electrode as an electrochemical theophylline sensor

    International Nuclear Information System (INIS)

    Aswini, K.K.; Vinu Mohan, A.M.; Biju, V.M.

    2016-01-01

    Theophylline is an inexpensive drug employed in asthma and chronic obstructive pulmonary disorder medications and is toxic at higher concentration. The development of a molecularly imprinted polymer based theophylline electrochemical sensor on glassy carbon electrode by the electropolymerization of 4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid is being discussed in this work. The MIP modification enhances the theophylline recognition ability and the electron transfer kinetics of the bare electrode. The parameters, controlling the performance of the imprinted polymer based sensor, like number of electropolymerization cycles, composition of the pre-polymerization mixture, pH and immersion time were investigated and optimized. The interaction energy and the most stable conformation of the template–monomer complex in the pre-polymerization mixture were determined computationally using ab initio calculations based on density functional theory. The amperometric measurements showed that the developed sensor has a method detection limit of 0.32 μM for the dynamic range of 0.4 to 17 μM, at optimized conditions. The transducer possesses appreciable selectivity in the presence of structurally similar interferents such as theobromine, caffeine and doxofylline. The developed sensor showed remarkable stability and reproducibility and was also successfully employed in theophylline detection from commercially available tablets. - Highlights: • Molecularly imprinted polymer based theophylline sensor was developed. • Imprinted poly(4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid) was electrodeposited. • Most stable template-monomer complex was assigned by computational analysis. • Possessed remarkable selectivity in the presence of structurally similar interferents • Employed for theophylline detection from commercially available tablets

  11. Layer by layer assembly of catalase and amine-terminated ionic liquid onto titanium nitride nanoparticles modified glassy carbon electrode: Study of direct voltammetry and bioelectrocatalytic activity

    International Nuclear Information System (INIS)

    Saadati, Shagayegh; Salimi, Abdollah; Hallaj, Rahman; Rostami, Amin

    2012-01-01

    Highlights: ► Catalase and amine-terminated ionic liquid were immobilized to GC/TiNnp with LBL assembly method. ► First a thin layer of NH 2 -IL is covalently attached to GC/TiNnp electrode using electro-oxidation. ► With alternative assemble of IL and catalase with positive and negative charged, multilayer was formed. ► Immobilized catalase shows excellent electrocatalytic activity toward H 2 O 2 reduction. ► Biosensor response is directly correlated to the number of bilayers. - Abstract: A novel, simple and facile layer by layer (LBL) approach is used for modification of glassy carbon (GC) electrode with multilayer of catalase and nanocomposite containing 1-(3-Aminopropyl)-3-methylimidazolium bromide (amine terminated ionic liquid (NH 2 -IL)) and titanium nitride nanoparticles (TiNnp). First a thin layer of NH 2 -IL is covalently attached to GC/TiNnp electrode using electro-oxidation method. Then, with alternative self assemble positively charged NH 2 -IL and negatively charged catalase a sensitive H 2 O 2 biosensor is constructed, whose response is directly correlated to the number of bilayers. The surface coverage of active catalase per bilayer, heterogeneous electron transfer rate constant (k s ) and Michaelis–Menten constant (K M ) of immobilized catalase were 3.32 × 10 −12 mol cm −2 , 5.28 s −1 and 1.1 mM, respectively. The biosensor shows good stability, high reproducibility, long life-time, and fast amperometric response with the high sensitivity of 380 μA mM −1 cm −2 and low detection limit of 100 nM at concentration range up to 2.1 mM.

  12. Molecularly imprinted poly(4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid) modified glassy carbon electrode as an electrochemical theophylline sensor

    Energy Technology Data Exchange (ETDEWEB)

    Aswini, K.K., E-mail: aswinikk@ymail.com; Vinu Mohan, A.M.; Biju, V.M., E-mail: vmbiju@ymail.com

    2016-08-01

    Theophylline is an inexpensive drug employed in asthma and chronic obstructive pulmonary disorder medications and is toxic at higher concentration. The development of a molecularly imprinted polymer based theophylline electrochemical sensor on glassy carbon electrode by the electropolymerization of 4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid is being discussed in this work. The MIP modification enhances the theophylline recognition ability and the electron transfer kinetics of the bare electrode. The parameters, controlling the performance of the imprinted polymer based sensor, like number of electropolymerization cycles, composition of the pre-polymerization mixture, pH and immersion time were investigated and optimized. The interaction energy and the most stable conformation of the template–monomer complex in the pre-polymerization mixture were determined computationally using ab initio calculations based on density functional theory. The amperometric measurements showed that the developed sensor has a method detection limit of 0.32 μM for the dynamic range of 0.4 to 17 μM, at optimized conditions. The transducer possesses appreciable selectivity in the presence of structurally similar interferents such as theobromine, caffeine and doxofylline. The developed sensor showed remarkable stability and reproducibility and was also successfully employed in theophylline detection from commercially available tablets. - Highlights: • Molecularly imprinted polymer based theophylline sensor was developed. • Imprinted poly(4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid) was electrodeposited. • Most stable template-monomer complex was assigned by computational analysis. • Possessed remarkable selectivity in the presence of structurally similar interferents • Employed for theophylline detection from commercially available tablets.

  13. Layer by layer assembly of catalase and amine-terminated ionic liquid onto titanium nitride nanoparticles modified glassy carbon electrode: Study of direct voltammetry and bioelectrocatalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    Saadati, Shagayegh [Department of Chemistry, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Salimi, Abdollah, E-mail: absalimi@uok.ac.ir [Department of Chemistry, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Research Center for Nanotechnology, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of); Hallaj, Rahman; Rostami, Amin [Department of Chemistry, University of Kurdistan, P.O. Box 416, Sanandaj (Iran, Islamic Republic of)

    2012-11-13

    Highlights: Black-Right-Pointing-Pointer Catalase and amine-terminated ionic liquid were immobilized to GC/TiNnp with LBL assembly method. Black-Right-Pointing-Pointer First a thin layer of NH{sub 2}-IL is covalently attached to GC/TiNnp electrode using electro-oxidation. Black-Right-Pointing-Pointer With alternative assemble of IL and catalase with positive and negative charged, multilayer was formed. Black-Right-Pointing-Pointer Immobilized catalase shows excellent electrocatalytic activity toward H{sub 2}O{sub 2} reduction. Black-Right-Pointing-Pointer Biosensor response is directly correlated to the number of bilayers. - Abstract: A novel, simple and facile layer by layer (LBL) approach is used for modification of glassy carbon (GC) electrode with multilayer of catalase and nanocomposite containing 1-(3-Aminopropyl)-3-methylimidazolium bromide (amine terminated ionic liquid (NH{sub 2}-IL)) and titanium nitride nanoparticles (TiNnp). First a thin layer of NH{sub 2}-IL is covalently attached to GC/TiNnp electrode using electro-oxidation method. Then, with alternative self assemble positively charged NH{sub 2}-IL and negatively charged catalase a sensitive H{sub 2}O{sub 2} biosensor is constructed, whose response is directly correlated to the number of bilayers. The surface coverage of active catalase per bilayer, heterogeneous electron transfer rate constant (k{sub s}) and Michaelis-Menten constant (K{sub M}) of immobilized catalase were 3.32 Multiplication-Sign 10{sup -12} mol cm{sup -2}, 5.28 s{sup -1} and 1.1 mM, respectively. The biosensor shows good stability, high reproducibility, long life-time, and fast amperometric response with the high sensitivity of 380 {mu}A mM{sup -1} cm{sup -2} and low detection limit of 100 nM at concentration range up to 2.1 mM.

  14. Highly Stable and Flexible Pressure Sensors with Modified Multi-Walled Carbon Nanotube/Polymer Composites for Human Monitoring.

    Science.gov (United States)

    He, Yin; Ming, Yue; Li, Wei; Li, Yafang; Wu, Maoqi; Song, Jinzhong; Li, Xiaojiu; Liu, Hao

    2018-04-26

    A facile method for preparing an easy processing, repeatable and flexible pressure sensor was presented via the synthesis of modified multi-walled carbon nanotubes (m-MWNTs) and polyurethane (PU) films. The surface modification of multi-walled carbon nanotubes (MWNTs) simultaneously used a silane coupling agent (KH550) and sodium dodecyl benzene sulfonate (SDBS) to improve the dispersibility and compatibility of the MWNTs in a polymer matrix. The electrical property and piezoresistive behavior of the m-MWNT/PU composites were compared with raw multi-walled carbon nanotube (raw MWNT)/PU composites. Under linear uniaxial pressure, the m-MWNT/PU composite exhibited 4.282%kPa −1 sensitivity within the pressure of 1 kPa. The nonlinear error, hysteresis error and repeatability error of the piezoresistivity of m-MWNT/PU decreased 9%, 16.72% and 54.95% relative to raw MWNT/PU respectively. Therefore, the piezoresistive response of m-MWNT/PU had better stability than that of raw MWNT/PU composites. The m-MWNT/PU sensors could be utilized in wearable devices for body movement detection, monitoring of respiration and pressure detection in garments.

  15. Covalent attachment of pyridine-type molecules to glassy carbon surfaces by electrochemical reduction of in situ generated diazonium salts. Formation of ruthenium complexes on ligand-modified surfaces

    International Nuclear Information System (INIS)

    Yesildag, Ali; Ekinci, Duygu

    2010-01-01

    In this study, pyridine, quinoline and phenanthroline molecules were covalently bonded to glassy carbon (GC) electrode surfaces for the first time using the diazonium modification method. Then, the complexation ability of the modified films with ruthenium metal cations was investigated. The derivatization of GC surfaces with heteroaromatic molecules was achieved by electrochemical reduction of the corresponding in situ generated diazonium salts. X-ray photoelectron spectroscopy (XPS) was used to confirm the attachment of heteroaromatic molecules to the GC surfaces and to determine the surface concentration of the films. The barrier properties of the modified GC electrodes were studied in the presence of redox probes such as Fe(CN) 6 3- and Ru(NH 3 ) 6 3+ by cyclic voltammetry. Additionally, the presence of the resulting organometallic films on the surfaces was verified by XPS after the chemical transformation of the characterized ligand films to the ruthenium complex films. The electrochemical behavior of these films in acetonitrile solution was investigated using voltammetric methods, and the surface coverage of the organometallic films was determined from the reversible metal-based Ru(II)/Ru(III) oxidation waves.

  16. Covalent attachment of pyridine-type molecules to glassy carbon surfaces by electrochemical reduction of in situ generated diazonium salts. Formation of ruthenium complexes on ligand-modified surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Yesildag, Ali [Department of Chemistry, Faculty of Sciences, Atatuerk University, 25240 Erzurum (Turkey); Ekinci, Duygu, E-mail: dekin@atauni.edu.t [Department of Chemistry, Faculty of Sciences, Atatuerk University, 25240 Erzurum (Turkey)

    2010-09-30

    In this study, pyridine, quinoline and phenanthroline molecules were covalently bonded to glassy carbon (GC) electrode surfaces for the first time using the diazonium modification method. Then, the complexation ability of the modified films with ruthenium metal cations was investigated. The derivatization of GC surfaces with heteroaromatic molecules was achieved by electrochemical reduction of the corresponding in situ generated diazonium salts. X-ray photoelectron spectroscopy (XPS) was used to confirm the attachment of heteroaromatic molecules to the GC surfaces and to determine the surface concentration of the films. The barrier properties of the modified GC electrodes were studied in the presence of redox probes such as Fe(CN){sub 6}{sup 3-} and Ru(NH{sub 3}){sub 6}{sup 3+} by cyclic voltammetry. Additionally, the presence of the resulting organometallic films on the surfaces was verified by XPS after the chemical transformation of the characterized ligand films to the ruthenium complex films. The electrochemical behavior of these films in acetonitrile solution was investigated using voltammetric methods, and the surface coverage of the organometallic films was determined from the reversible metal-based Ru(II)/Ru(III) oxidation waves.

  17. Impedance response of carbon nanotube-titania electrodes dried under modified gravity

    International Nuclear Information System (INIS)

    Ordenana-Martinez, A.S.; Rincon, M.E.; Vargas, M.; Ramos, E.

    2011-01-01

    The synthesis and impregnation of porous titania films by commercial multiwalled carbon nanotubes and nanotube rich carbon soot are reported. The samples were dried under terrestrial gravity g and in a centrifuge accelerated at 13 g. X-Ray Diffraction data and Scanning Electron Microscopy images indicated differences in the crystal structure and tendency to agglomeration in both carbon types, providing different microstructures of functionally graded electrodes. Drying the samples in a centrifuge helps to the distribution of carbon nanoparticles and to the decrement of the impedance at the contact interfaces. The presence of titania weakens the differences observed in both drying protocols, but not the differences due to the carbon source. Superior capacitance and network conductivity were observed in electrodes based on commercial carbon nanotubes.

  18. Fabrication and characterization of drug-loaded nano-hydroxyapatite/polyamide 66 scaffolds modified with carbon nanotubes and silk fibroin

    Directory of Open Access Journals (Sweden)

    Yao MZ

    2016-11-01

    Full Text Available Meng-Zhu Yao,1 Ming-Yi Huang-Fu,1 Hui-Na Liu,1 Xia-Rong Wang,1 Xiaoxia Sheng,2 Jian-Qing Gao1 1Institute of Pharmaceutics, College of Pharmaceutical Sciences, Zhejiang University, 2Hangzhou SoliPharma Co., Ltd, Hangzhou, Zhejiang, People’s Republic of China Abstract: Nano-hydroxyapatite/polyamide 66 (nHA/PA66 porous scaffolds were fabricated by a phase inversion method. Carbon nanotubes (CNTs and silk fibroin (SF were used to modify the surface of the nHA/PA66 scaffolds by freeze-drying and cross-linking. Dexamethasone was absorbed to the CNTs to promote the osteogenic differentiation of bone mesenchymal stem cells (BMSCs. The cell viability of BMSCs was investigated by changing the concentration of the CNT dispersion, and the most biocompatible scaffold was selected. In addition, the morphology and mechanical property of the scaffolds were investigated. The results showed that the nHA/PA66 scaffolds modified with CNTs and SF met the requirements of bone tissue engineering scaffolds. The dexamethasone-loaded CNT/SF-nHA/PA66 composite scaffold promoted the osteogenic differentiation of BMSCs, and the drug-loaded scaffolds are expected to function as effective bone tissue engineering scaffolds. Keywords: BMSCs, tissue engineering, porous scaffold, carbon nanotubes, silk fibroin, surface modification, dexamethasone

  19. Disposable screen-printed bismuth electrode modified with multi-walled carbon nanotubes for electrochemical stripping measurements.

    Science.gov (United States)

    Niu, Xiangheng; Zhao, Hongli; Lan, Minbo

    2011-01-01

    Integrating the advantages of screen printing technology with the encouraging electroanalytical characteristic of metallic bismuth, we developed an ultrasensitive and disposable screen-printed bismuth electrode (SPBE) modified with multi-walled carbon nanotubes (MWCNTs) for electrochemical stripping measurements. Metallic bismuth powders and MWCNTs were homogeneously mixed with graphite-carbon ink to mass-prepare screen-printed bismuth electrode doped with multi-walled carbon nanotubes (SPBE/MWCNT). The electroanalytical performance of the prepared SPBE/MWCNT was intensively evaluated by measuring trace Hg(II) with square-wave anodic stripping voltammetry (SWASV). The results indicated that the SPBE modified with 2 wt% MWCNTs could offer a more sensitive response to trace Hg(II) than the bare SPBE. The stripping current obtained at SPBE/MWCNT was linear with Hg(II) concentration in the range from 0.2 to 40 µg/L (R(2) = 0.9976), with a detection limit of 0.09 µg/L (S/N = 3) under 180 s accumulation. The proposed "mercury-free" electrode, with extremely simple preparation and ultrahigh sensitivity, holds wide application prospects in both environmental and industrial monitoring. 2011 © The Japan Society for Analytical Chemistry

  20. In-Situ Liquid Hydrogenation of m-Chloronitrobenzene over Fe-Modified Pt/Carbon Nanotubes Catalysts

    Directory of Open Access Journals (Sweden)

    Feng Li

    2018-02-01

    Full Text Available In-situ liquid-phase hydrogenation of m-chloronitrobenzene (m-CNB based on aqueous-phase reforming (APR of ethanol and catalytic hydrogenation was carried out over Fe-modified Pt/carbon nanotubes (CNTs catalysts. The effects of Pt loading over CNTs and Fe modification on the catalytic performance of Pt/CNTs catalysts were studied. In-tube loading of Pt particles, compared with out-tube loading, considerably improved the catalytic activity. With in-tube loading, Fe-modified Pt/CNTs catalysts further improved the m-CNB in-situ hydrogenation performance. After Fe modification, Pt–Fe/CNTs catalysts formed, inside CNTs, a Pt–Fe alloy and iron oxides, which both improved catalytic hydrogenation performance and significantly enhanced ethanol APR hydrogen producing performance, thereby increasing the m-CNB in-situ hydrogenation reactivity.

  1. Electrochemical capacitive behaviour of multiwalled carbon nanotubes modified with electropolymeric films of nickel tetraaminophthalocyanine

    CSIR Research Space (South Africa)

    Chidembo, AT

    2010-11-01

    Full Text Available Electrochemical capacitive behaviour of the electropolymeric nickel tetra-aminophthalocyanine (poly-NiTAPc) supported on multiwalled carbon nanotube (MWCNT) platform is described. From the data in 1 M H2SO4, the MWCNT-poly-NiTAPc exhibited superior...

  2. Human osteoblast-like MG 63 cells on polysulfone modified with carbon nanotubes or carbon nanohorns

    Czech Academy of Sciences Publication Activity Database

    Staňková, Ľubica; Fraczek-Szczypta, A.; Blazewicz, M.; Filová, Elena; Blazewicz, S.; Lisá, Věra; Bačáková, Lucie

    2014-01-01

    Roč. 67, Feb 2014 (2014), s. 578-591 ISSN 0008-6223 R&D Projects: GA ČR(CZ) GAP108/12/1168 Institutional support: RVO:67985823 Keywords : carbon * nanotubes * cells Subject RIV: EI - Biotechnology ; Bionics Impact factor: 6.196, year: 2014

  3. Novel Polyvinyl Alcohol/Styrene Butadiene Rubber Latex/Carboxymethyl Cellulose Nanocomposites Reinforced with Modified Halloysite Nanotubes

    Directory of Open Access Journals (Sweden)

    Yanjun Tang

    2013-01-01

    Full Text Available Novel polyvinyl alcohol (PVA/styrene butadiene rubber (SBR latex/carboxymethyl cellulose (CMC/halloysite nanotubes (HNTs nanocomposites were successfully prepared through physical blending. The as-obtained PVA/SBR/CMC/HNTs nanocomposites were coated on the surface of old corrugated container (OCC-based paper in an effort to improve the mechanical properties of paper. To improve the dispersion of HNTs and enhance the compatibility between HNTs and polymer matrix, HNTs were modified with titanate coupling agent (TCA. FT-IR, together with TGA, confirmed that TCA was grafted onto the surface of HNTs successfully. XRD demonstrated that the crystal structures of HNTs remained almost unchanged. TEM showed that modified HNTs exhibited good dispersion and possessed nanotubular structures with an outer diameter of around 50 nm and an inner diameter of about 20 nm. SEM gave an indication that modified HNTs were dispersed more uniformly than unmodified HNTs within PVA/SBR/CMC matrix. Rheological measurement exhibited that surface modification process enhanced the compatibility between HNTs and polymer matrix, thus resulting in the decreased viscosity of nanocomposites. In comparison with unmodified HNTs, modified HNTs were found to contribute more to the enhancement in mechanical properties, which might be attributed to the better dispersion and compatibility of modified HNTs evidenced by TEM, SEM, and rheological measurement.

  4. Aptamer-based electrochemical assay of 17β-estradiol using a glassy carbon electrode modified with copper sulfide nanosheets and gold nanoparticles, and applying enzyme-based signal amplification

    International Nuclear Information System (INIS)

    Huang, Ke-Jing; Liu, Yu-Jie; Zhang, Ji-Zong

    2015-01-01

    We have developed an electrochemical method for the determination of 17β-estradiol. A glassy carbon electrode was modified with a composite made from copper sulfide nanosheets, gold nanoparticles, and glucose oxidase. The copper sulfide nanosheet was prepared by a single-step hydrothermal process, and its properties were characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. Finally, an estradiol-specific aptamer was assembled on the electrode. The copper sulfide nanosheet on the electrode surface acts as a relatively good electrical conductor. Glucose oxidase acts as an indicator, and the dual modification of glucose oxidase and gold nanoparticles for signal amplification. The determination of 17β-estradiol was performed by differential pulse voltammetry of glucose oxidase because the signal measured at typically −0.43 V depends on the concentration of 17β-estradiol because addition of 17β-estradiol at electrode hinders electron transfer. A linear relationship exists between the peak current and the logarithm of concentration of 17β-estradiol in the 0.5 pM to 5 nM range, with a 60 f. detection limit (at 3σ/S). The method displays good selectivity over bisphenol A, 1-aminoanthraquinone and naphthalene even if present in 100-fold concentrations. (author)

  5. A glassy carbon electrode modified with porous Cu_2O nanospheres on reduced graphene oxide support for simultaneous sensing of uric acid and dopamine with high selectivity over ascorbic acid

    International Nuclear Information System (INIS)

    Mei, Li-Ping; Feng, Jiu-Ju; Wu, Liang; Chen, Jian-Rong; Shen, Liguo; Wang, Ai-Jun; Xie, Yunlong

    2016-01-01

    Porous cuprous oxide nanospheres were deposited on reduced graphene oxide (pCu_2O NS-rGO) by a solvothermal approach that uses hexadecyltrimethylammonium bromide as the capping agent and L-glutamic acid as the reducing agent. The nanomaterial was characterized by transmission electron microscopy, Raman spectroscopy, thermogravimetry, and electrochemical methods. A glassy carbon electrode was modified with pCu_2O NS-rGO, and the respective electrode displays a well expressed oxidation peak for dopamine (DA) located at 160 mV (vs. SCE). It also gives a strong peak for uric acid (UA) which is separated from the DA peak by 130 mV (vs. SCE). No signals can be detected for ascorbic acid (AA) in concentrations up to 2.0 mM. The findings are exploited in a method for simultaneous determination of UA and DA. The linear ranges are from 1.0 to 138 μM for UA, and from 0.05 to 109 μM for DA even in the presence of relatively high concentrations of AA. The detection limits are 112 nM for UA and 15 nM for DA (at an S/N ratio of 3). (author)

  6. Electrochemical behavior and assembly of tetranuclear Dawson-derived sandwich compound [Cd4(H2O)2(As2W15O56)2]16- on 4-aminobenzoic acid modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Bi Lihua; Shen Yan; Jiang Junguang; Wang Erkang; Dong Shaojun

    2005-01-01

    The transition metal-substituted heteropolyoxoanion, Cd 4 (H 2 O) 2 (As 2 W 15 O 56 ) 2 12- (As 4 W 30 Cd 4 ), is one of the trivacant Dawson derivatives. Its redox electrochemistry has been studied in acid buffer solutions using cyclic voltammetry. It exhibited three steps of four-electron redox waves attributed to redox processes of the tungsten-oxo framework. Through layer-by-layer assembly, the compound was first successfully immobilized on a 4-aminobenzoic acid modified glassy carbon electrode surface by alternate deposition with a quaternized poly(4-vinylpyridine) partially complexed with [Os(bpy) 2 Cl] 2+/+ (denoted as QPVP-Os). Thus, prepared multilayer films have been characterized by cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS) and UV-vis spectroscopy (UV-vis). The electrocatalytic activities of the multilayer films containing As 4 W 30 Cd 4 have been investigated on the reduction of three substrates of important analytical interests, NO 2 - , BrO 3 - and IO 3 - . And with the increase of the number of As 4 W 30 Cd 4 layers, the catalytic current towards the reduction of BrO 3 - was enhanced and the catalytic potential shifted positively

  7. Electrodeposition of gold nanoclusters on overoxidized polypyrrole film modified glassy carbon electrode and its application for the simultaneous determination of epinephrine and uric acid under coexistence of ascorbic acid

    Energy Technology Data Exchange (ETDEWEB)

    Li Jing [Department of Chemistry, University of Science and Technology of China, Hefei 230026 (China); Lin Xiangqin [Department of Chemistry, University of Science and Technology of China, Hefei 230026 (China)]. E-mail: xqlin@ustc.edu.cn

    2007-07-23

    A novel biosensor was fabricated by electrochemical deposition of gold nanoclusters on ultrathin overoxidized polypyrrole (PPyox) film, formed a nano-Au/PPyox composite on glassy carbon electrode (nano-Au/PPyox/GCE). The properties of the nanocomposite have been characterized by field emission scanning electron microscope (FE-SEM), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD) and electrochemical investigations. The nano-Au/PPyox/GCE had strongly catalytic activity toward the oxidation of epinephrine (EP), uric acid (UA) and ascorbic acid (AA), and resolved the overlapping voltammetric response of EP, UA and AA into three well-defined peaks with a large anodic peak difference. The catalytic peak currents obtained from differential pulse voltammetry increased linearly with increasing EP and UA concentrations in the range of 3.0 x 10{sup -7} to 2.1 x 10{sup -5} M and 5.0 x 10{sup -8} to 2.8 x 10{sup -5} M with a detection limit of 3.0 x 10{sup -8} and 1.2 x 10{sup -8} M (s/n = 3), respectively. The results showed that the modified electrode can selectively determine EP and UA in the coexistence of a large amount of AA. In addition, the sensor exhibited excellent sensitivity, selectivity and stability. The nano-Au/PPyox/GCE has been applied to determination of EP in epinephrine hydrochloride injection and UA in urine samples with satisfactory results.

  8. Nonenzymatic sensing of glucose at neutral pH values using a glassy carbon electrode modified with graphene nanosheets and Pt-Pd bimetallic nanocubes

    International Nuclear Information System (INIS)

    Chen, Xiaomei; Tian, Xiaotian; Zhao, Limin; Huang, Zhiyong; Oyama, Munetaka

    2014-01-01

    We report on a nonenzymatic method for the determination of glucose using an electrode covered with graphene nanosheets (GNs) modified with Pt-Pd nanocubes (PtPdNCs). The latter were prepared on GNs by using N,N-dimethylformamide as a bifunctional solvent for the reduction of both metallic precursors and graphene oxide, and for confining the growth of PtPdNCs on the surface. The modified electrode displays strong and sensitive current response to the electrooxidation of glucose, notably at pH 7. The sensitivities increase in the order of Pt 1 Pd 5 NCs< Pt 1 Pd 3 NCs< Pt 5 Pd 1 NCs< Pt 3 Pd 1 NCs< Pt 1 Pd 1 NCs. At an applied potential of +0.25 V, the electrode responds linearly (R = 0.9987) to glucose in up to 24.5 mM concentration, with a sensitivity of 1.4 μA cm −2 M −1 . The sensor is not poisoned by chloride, and not interfered by ascorbic acid, uric acid and p-acetamidophenol under normal physiological conditions. The modified electrode also displays a wide linear range, good stability and fast amperometric response, thereby indicating the potential of the bimetallic materials for nonenzymatic sensing of glucose. (author)

  9. Development of a modified electrode with amine-functionalized TiO{sub 2}/multi-walled carbon nanotubes nanocomposite for electrochemical sensing of the atypical neuroleptic drug olanzapine

    Energy Technology Data Exchange (ETDEWEB)

    Arvand, Majid, E-mail: arvand@guilan.ac.ir; Palizkar, Bahareh

    2013-12-01

    In this work, using of amine-functionalized TiO{sub 2}/multi-walled carbon nanotubes (NH{sub 2}-TiO{sub 2}-MWCNTs) nanocomposite for modification of glassy carbon electrode (GCE) was investigated. The nanocomposite was characterized by Fourier transformed infrared spectroscopy, transmission electron microscopy and scanning electron microscopy. The efficiency of modified electrode for electrocatalytic the oxidation of olanzapine was studied by cyclic voltammetry, square wave voltammetry and chronoamperometry. The electrochemical measurements were carried out in phosphate-buffered solution (PBS, pH 5.0). The NH{sub 2}-TiO{sub 2}-MWCNTs/GCE provided high surface area and more sensitive performance. The charge transfer coefficient (α) and the apparent charge transfer rate constant (k{sub s}) were calculated to be equal to 0.42 and 0.173 s{sup −1}, respectively. The square wave voltammetry exhibited two linear dynamic ranges and a detection limit of 0.09 μM of olanzapine. In addition, the modified electrode was employed for the determination of olanzapine in pharmaceutical and human blood serum samples in order to illustrate the applicability of proposed method. - Highlights: • A simple and rapid sensor for determination of olanzapine in tablet and serum was prepared. • The amine-functionalized TiO{sub 2}-MWCNTs/GCE showed an obvious increase in surface area. • The presence of NH{sub 2}-TiO{sub 2} nanoparticles showed good ability to distinguish the response of olanzapine.

  10. Metal-modified and vertically aligned carbon nanotube sensors array for landfill gas monitoring applications.

    Science.gov (United States)

    Penza, M; Rossi, R; Alvisi, M; Serra, E

    2010-03-12

    Vertically aligned carbon nanotube (CNT) layers were synthesized on Fe-coated low-cost alumina substrates using radio-frequency plasma enhanced chemical vapour deposition (RF-PECVD) technology. A miniaturized CNT-based gas sensor array was developed for monitoring landfill gas (LFG) at a temperature of 150 degrees C. The sensor array was composed of 4 sensing elements with unmodified CNT, and CNT loaded with 5 nm nominally thick sputtered nanoclusters of platinum (Pt), ruthenium (Ru) and silver (Ag). Chemical analysis of multicomponent gas mixtures constituted of CO(2), CH(4), H(2), NH(3), CO and NO(2) has been performed by the array sensor responses and pattern recognition based on principal component analysis (PCA). The PCA results demonstrate that the metal-decorated and vertically aligned CNT sensor array is able to discriminate the NO(2) presence in the multicomponent mixture LFG. The NO(2) gas detection in the mixture LFG was proved to be very sensitive, e.g.: the CNT:Ru sensor shows a relative change in the resistance of 1.50% and 0.55% for NO(2) concentrations of 3.3 ppm and 330 ppb dispersed in the LFG, respectively, with a wide NO(2) gas concentration range measured from 0.33 to 3.3 ppm, at the sensor temperature of 150 degrees C. The morphology and structure of the CNT networks have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. A forest-like nanostructure of vertically aligned CNT bundles in the multi-walled form appeared with a height of about 10 microm and a single-tube diameter varying in the range of 5-35 nm. The intensity ratio of the Raman spectroscopy D-peak and G-peak indicates the presence of disorder and defects in the CNT networks. The size of the metal (Pt, Ru, Ag) nanoclusters decorating the CNT top surface varies in the range of 5-50 nm. Functional characterization based on electrical charge transfer sensing mechanisms in the metal-modified CNT-chemoresistor array

  11. Cobalt hexacyanoferrate modified multi-walled carbon nanotubes/graphite composite electrode as electrochemical sensor on microfluidic chip

    International Nuclear Information System (INIS)

    Li Xinchun; Chen Zuanguang; Zhong Yuwen; Yang Fan; Pan Jianbin; Liang Yajing

    2012-01-01

    Highlights: ► CoHCF nanoparticles modified MWCNTs/graphite electrode use for electrochemistry on electrophoresis microchip for the first time. ► Simultaneous, rapid, and sensitive electrochemical detection of hydrazine and isoniazid in real samples. ► An exemplary work of CME sensor assembly onto microchip for determination of analytes with environmental significance. ► Manifestation of the applicability and flexibility of CME sensor for electroanalysis on microfluidic chip. - Abstract: Nanomaterial-based electrochemical sensor has received significant interest. In this work, cobalt hexacyanoferrate modified multi-walled carbon nanotubes/graphite composite electrode was electrochemically prepared and exploited as an amperometric detector for microchip electrophoresis. The prepared sensor displayed rapid and sensitive response towards hydrazine and isoniazid oxidation, which was attributed to synergetic electrocatalytic effect of cobalt hexacyanoferrate and multi-walled carbon nanotubes. The sensitivity enhancement with nearly two orders of magnitude was gained, compared with the bare carbon paste electrode, with the detection limit of 0.91 μM (S/N = 3) for hydrazine. Acceptable repeatability of the microanalysis system was verified by consecutive eleven injections of hydrazine without chip and electrode treatments, the RSDs for peak current and migration time were 3.4% and 2.1%, respectively. Meanwhile, well-shaped electrophoretic peaks were observed, mainly due to fast electron transfer of electroactive species on the modified electrode. The developed microchip-electrochemistry setup was successfully applied to the determination of hydrazine and isoniazid in river water and pharmaceutical preparation, respectively. Several merits of the novel electrochemical sensor coupled with microfluidic platform, such as comparative stability, easy fabrication and high sensitivity, hold great potential for hydrazine compounds assay in the lab-on-a-chip system.

  12. Cobalt hexacyanoferrate modified multi-walled carbon nanotubes/graphite composite electrode as electrochemical sensor on microfluidic chip

    Energy Technology Data Exchange (ETDEWEB)

    Li Xinchun [School of Pharmaceutical Sciences, Sun Yat-sen University, 132 Waihuan East Road of Higher Education Mega Centre, Guangzhou 510006 (China); Chen Zuanguang, E-mail: chenzg@mail.sysu.edu.cn [School of Pharmaceutical Sciences, Sun Yat-sen University, 132 Waihuan East Road of Higher Education Mega Centre, Guangzhou 510006 (China); Zhong Yuwen, E-mail: yu0106@163.com [Center for Disease Control and Prevention of Guangdong Province, 176 Xingangxi, Guangzhou 510300 (China); Yang Fan; Pan Jianbin; Liang Yajing [School of Pharmaceutical Sciences, Sun Yat-sen University, 132 Waihuan East Road of Higher Education Mega Centre, Guangzhou 510006 (China)

    2012-01-13

    Highlights: Black-Right-Pointing-Pointer CoHCF nanoparticles modified MWCNTs/graphite electrode use for electrochemistry on electrophoresis microchip for the first time. Black-Right-Pointing-Pointer Simultaneous, rapid, and sensitive electrochemical detection of hydrazine and isoniazid in real samples. Black-Right-Pointing-Pointer An exemplary work of CME sensor assembly onto microchip for determination of analytes with environmental significance. Black-Right-Pointing-Pointer Manifestation of the applicability and flexibility of CME sensor for electroanalysis on microfluidic chip. - Abstract: Nanomaterial-based electrochemical sensor has received significant interest. In this work, cobalt hexacyanoferrate modified multi-walled carbon nanotubes/graphite composite electrode was electrochemically prepared and exploited as an amperometric detector for microchip electrophoresis. The prepared sensor displayed rapid and sensitive response towards hydrazine and isoniazid oxidation, which was attributed to synergetic electrocatalytic effect of cobalt hexacyanoferrate and multi-walled carbon nanotubes. The sensitivity enhancement with nearly two orders of magnitude was gained, compared with the bare carbon paste electrode, with the detection limit of 0.91 {mu}M (S/N = 3) for hydrazine. Acceptable repeatability of the microanalysis system was verified by consecutive eleven injections of hydrazine without chip and electrode treatments, the RSDs for peak current and migration time were 3.4% and 2.1%, respectively. Meanwhile, well-shaped electrophoretic peaks were observed, mainly due to fast electron transfer of electroactive species on the modified electrode. The developed microchip-electrochemistry setup was successfully applied to the determination of hydrazine and isoniazid in river water and pharmaceutical preparation, respectively. Several merits of the novel electrochemical sensor coupled with microfluidic platform, such as comparative stability, easy fabrication and

  13. Enhanced performance of microbial fuel cells by using MnO_2/Halloysite nanotubes to modify carbon cloth anodes

    International Nuclear Information System (INIS)

    Chen, Yingwen; Chen, Liuliu; Li, Peiwen; Xu, Yuan; Fan, Mengjie; Zhu, Shemin; Shen, Shubao

    2016-01-01

    The modification of anode materials is important to enhance the power generation of MFCs (microbial fuel cells). A novel and cost-effective modified anode that is fabricated by dispersing manganese dioxide (MnO_2) and HNTs (Halloysite nanotubes) on carbon cloth to improve the MFCs' power production was reported. The results show that the MnO_2/HNT anodes acquire more bacteria and provide greater kinetic activity and power density compared to the unmodified anode. Among all modified anodes, 75 wt% MnO_2/HNT exhibits the highest electrochemical performance. The maximum power density is 767.3 mWm"−"2, which 21.6 higher than the unmodified anode (631 mW/m"2). Besides, CE (Coulombic efficiency) was improved 20.7, indicating that more chemical energy transformed to electricity. XRD (X-Ray powder diffraction) and FTIR (Fourier transform infrared spectroscopy) are used to characterize the structure and functional groups of the anode. CV (cyclic voltammetry) scans and SEM (scanning electron microscope) images demonstrate that the measured power density is associated with the attachment of bacteria, the microorganism morphology differed between the modified and the original anode. These findings demonstrate that MnO_2/HNT nanocomposites can alter the characteristics of carbon cloth anodes to effectively modify the anode for practical MFC applications. - Highlights: • Different contents of MnO_2/HNT composites were prepared and used to modify anodes in MFCs. • The performance of MFCs was improved by the anode modification. • 75% wt MnO_2/HNT modified anode showed the better capacity on power density. • Water contact angle, CV, SEM were determined to figure out the effect of modification on MFCs. • MnO_2/HNT modified anode in MFCs was first studied to push MFCs technology forward.

  14. Fabrication of β-cyclodextrin-coated poly (diallyldimethylammonium chloride)-functionalized graphene composite film modified glassy carbon-rotating disk electrode and its application for simultaneous electrochemical determination colorants of sunset yellow and tartrazine.

    Science.gov (United States)

    Ye, Xiaoliang; Du, Yongling; Lu, Daban; Wang, Chunming

    2013-05-24

    We proposed a green and facile approach for the synthesis of β-cyclodextrin-coated poly(diallyldimethylammonium chloride)-functionalized graphene composite film (β-CD-PDDA-Gr) by using L-ascorbic acid (L-AA) as the reducing agent at room temperature. The β-CD-PDDA-Gr composite film modified glassy carbon-rotating disk electrode (GC-RDE) was then developed for the sensitive simultaneous determination of two synthetic food colorants: sunset yellow (SY) and tartrazine (TT). By cyclic voltammetry (CV), the peak currents of SY and TT increased obviously on the developed electrochemical sensor. The kinetic parameters, such as diffusion coefficient D and standard heterogeneous rate constant kb, were estimated by linear sweep voltammetry (LSV). Under the optimal conditions, the differential pulse voltammetry (DPV) signals of SY and TT on the β-CD-PDDA-Gr modified GC-RDE were significantly enhanced. The enhanced anodic peak currents represented the excellent analytical performance of simultaneous detection of SY and TT in the range of 5.0×10(-8) to 2.0×10(-5) mol L(-1), with a low limit of detection (LOD) of 1.25×10(-8) mol L(-1) for SY and 1.43×10(-8) mol L(-1) for TT (SN(-1)=3). This proposed method displayed outstanding selectivity, good stability and acceptable repeatability and reproducibility, and also has been used to simultaneously determine SY and TT in some commercial soft drinks with satisfactory results. The obtained results were compared to HPLC of analysis for those two colorants and no significant differences were found. By the treatment of the experimental data, the electrochemical reaction mechanisms of SY and TT both involved a one-electron-one-proton-transfer process. Copyright © 2013 Elsevier B.V. All rights reserved.

  15. Determination of kojic acid based on the interface enhancement effects of carbon nanotube/alizarin red S modified electrode.

    Science.gov (United States)

    Liu, Jieshu; Zhou, Dazhai; Liu, Xiaopeng; Wu, Kangbing; Wan, Chidan

    2009-04-01

    Based on non-covalent interactions such as pi-pi stacking, van der Waals interactions and strong adsorption, alizarin red S (ARS) interacts with multi-walled carbon nanotubes (MWNT), improving the solubility of MWNT in water and resulting in a stable MWNT/ARS solution. By successive cyclic sweeps between 0.0 and 2.2V in the MWNT/ARS solution, a MWNT/ARS composite film was fabricated on an electrode surface. The electrochemical behaviors of kojic acid at the bare electrode, the ARS film-modified electrode and the MWNT/ARS film-modified electrode were investigated. It was found that the oxidation signal of kojic acid significantly increased at the MWNT/ARS film-modified electrode, which was attributed to the unique properties of MWNT such as large surface area, strong adsorptive ability and subtle electronic character. The effects of pH and cyclic number of electropolymerization were examined. A rapid, sensitive and simple electrochemical method was then developed for the determination of kojic acid. This method exhibits good linearity over the range from 4.0 x 10(-7) to 6.0 x 10(-5)mol L(-1), and the limit of detection is as low as 1.0 x 10(-7)mol L(-1). In order to validate feasibility, the MWNT/ARS film-modified electrode was used for quantitative analysis of kojic acid in food samples.

  16. Polyurethane foams obtained from residues of PET manufacturing and modified with carbon nanotubes

    International Nuclear Information System (INIS)

    Stiebra, L; Cabulis, U; Knite, M

    2016-01-01

    In this work we report the preparation of rigid microcellular polyurethane/carbon nanotube nanocomposites with different CNT loadings (0.09-0.46%) and various isocyanate indexes (110-260). Water was used as a blowing agent for samples. Density of all obtained samples – 200 ± 10 kg/m 3 . Electrical properties, as well as heat conductivity, cellular structure and mechanical properties of these nanocomposites were investigated. (paper)

  17. Polyurethane foams obtained from residues of PET manufacturing and modified with carbon nanotubes

    Science.gov (United States)

    Stiebra, L.; Cabulis, U.; Knite, M.

    2016-04-01

    In this work we report the preparation of rigid microcellular polyurethane/carbon nanotube nanocomposites with different CNT loadings (0.09-0.46%) and various isocyanate indexes (110-260). Water was used as a blowing agent for samples. Density of all obtained samples - 200 ± 10 kg/m3. Electrical properties, as well as heat conductivity, cellular structure and mechanical properties of these nanocomposites were investigated.

  18. Enhanced performance of electrospun carbon fibers modified with carbon nanotubes: promising electrodes for enzymatic biofuel cells.

    Science.gov (United States)

    Engel, A Both; Cherifi, A; Tingry, S; Cornu, D; Peigney, A; Laurent, Ch

    2013-06-21

    New nanostructured electrodes, promising for the production of clean and renewable energy in biofuel cells, were developed with success. For this purpose, carbon nanofibers were produced by the electrospinning of polyacrylonitrile solution followed by convenient thermal treatments (stabilization followed by carbonization at 1000, 1200 and 1400° C), and carbon nanotubes were adsorbed on the surfaces of the fibers by a dipping method. The morphology of the developed electrodes was characterized by several techniques (SEM, Raman spectroscopy, electrical conductivity measurement). The electrochemical properties were evaluated through cyclic voltammetry, where the influence of the carbonization temperature of the fibers and the beneficial contribution of the carbon nanotubes were observed through the reversibility and size of the redox peaks of K3Fe(CN)6 versus Ag/AgCl. Subsequently, redox enzymes were immobilized on the electrodes and the electroreduction of oxygen to water was realized as a test of their efficiency as biocathodes. Due to the fibrous and porous structure of these new electrodes, and to the fact that carbon nanotubes may have the ability to promote electron transfer reactions of redox biomolecules, the new electrodes developed were capable of producing higher current densities than an electrode composed only of electrospun carbon fibers.

  19. Carboxyl-terminated butadiene-acrylonitrile-toughened epoxy/carboxyl-modified carbon nanotube nanocomposites: Thermal and mechanical properties

    Directory of Open Access Journals (Sweden)

    H. F. Xie

    2012-09-01

    Full Text Available Carboxyl-modified multi-walled carbon nanotubes (MWCNT–COOHs as nanofillers were incorporated into diglycidyl ether of bisphenol A (DGEBA toughened with carboxyl-terminated butadiene-acrylonitrile (CTBN. The carboxyl functional carbon nanotubes were characterized by Fourier-transform infrared spectroscopy and thermogravimetric analysis. Furthermore, cure kinetics, glass transition temperature (Tg, mechanical properties, thermal stability and morphology of DGEBA/CTBN/MWCNT–COOHs nanocomposites were investigated by differential scanning calorimetry (DSC, dynamic mechanical analysis (DMA, universal test machine, thermogravimetric analysis and scanning electron microscopy (SEM. DSC kinetic studies showed that the addition of MWCNT–COOHs accelerated the curing reaction of the rubber-toughened epoxy resin. DMA results revealed that Tg of rubber-toughened epoxy nanocomposites lowered with MWCNT–COOH contents. The tensile strength, elongation at break, flexural strength and flexural modulus of DGEBA/CTBN/MWCNT-COOHs nanocomposites were increased at lower MWCNT-COOH concentration. A homogenous dispersion of nanocomposites at lower MWCNT–COOH concentration was observed by SEM.

  20. Magnetic and Electrical Properties of Nitrogen-Doped Multiwall Carbon Nanotubes Fabricated by a Modified Chemical Vapor Deposition Method

    Directory of Open Access Journals (Sweden)

    María Luisa García-Betancourt

    2015-01-01

    Full Text Available Chemical vapor deposition (CVD is a preferential method to fabricate carbon nanotubes (CNTs. Several changes have been proposed to obtain improved CNTs. In this work we have fabricated nitrogen-doped multiwall carbon nanotubes (N-MWCNTs by means of a CVD which has been slightly modified. Such modification consists in changing the content of the by-product trap. Instead of acetone, we have half-filled the trap with an aqueous solution of NaCl (0–26.82 wt.%. Scanning electron microscope (SEM characterization showed morphological changes depending upon concentration of NaCl included in the trap. Using high resolution transmission electron microscopy several shape changes on the catalyst nanoparticles were also observed. According to Raman spectroscopy results N-MWCNTs fabricated using pure distillate water exhibit better crystallinity. Resistivity measurements performed on different samples by physical properties measurement Evercool system (PPMS showed metallic to semiconducting temperature dependent transitions when high content of NaCl is used. Results of magnetic properties show a ferromagnetic response to static magnetic fields and the coercive fields were very similar for all the studied cases. However, saturation magnetization is decreased if aqueous solution of NaCl is used in the trap.

  1. Interface control: A modified rooting technique for enhancing field emission from multiwall carbon nanotube based bulk emitters

    Energy Technology Data Exchange (ETDEWEB)

    Lahiri, Indranil [Nanomaterials and Device Lab, Department of Mechanical and Materials Engineering, Florida International University, 10555 West Flagler Street, Miami, FL 33174 (United States); Choi, Wonbong, E-mail: choiw@fiu.edu [Nanomaterials and Device Lab, Department of Mechanical and Materials Engineering, Florida International University, 10555 West Flagler Street, Miami, FL 33174 (United States)

    2011-08-15

    The unique properties of carbon nanotubes (CNTs) have raised hopes that these materials might find wide application as cold cathodes in various electron sources. The excellent field emission properties shown by CNT-based field emitters has further stimulated this expectation. However, efficient performance of a practical field emitter, which comprises a large number of randomly or regularly oriented CNTs, is restricted primarily due to poor junctions formed between CNTs and substrates. This study is aimed at enhancing the junction performance by way of a modified 'rooting' technique-interface control. In this process, the interface between CNTs and substrate has been tailored with different metals in an attempt to improve the CNT-substrate junction performance. Multiwall carbon nanotubes (MWCNTs) were synthesized on different interface-controlled substrates, i.e. Cu, Al, W, Si and low-temperature co-fired ceramic. All the samples produced mat-type, randomly oriented MWCNT structures. Among the four different substrates studied, MWCNT-based field emitters on Cu substrate demonstrated the best field emission response, in terms of low turn-on field, high emission current, good field enhancement factor and excellent stability in long-term operation. Emitter structures and their field emission behavior were correlated and it was shown that interface control, as an advanced 'rooting' process, plays an important role in determining the emission response from a bulk field emitter.

  2. Interface control: A modified rooting technique for enhancing field emission from multiwall carbon nanotube based bulk emitters

    International Nuclear Information System (INIS)

    Lahiri, Indranil; Choi, Wonbong

    2011-01-01

    The unique properties of carbon nanotubes (CNTs) have raised hopes that these materials might find wide application as cold cathodes in various electron sources. The excellent field emission properties shown by CNT-based field emitters has further stimulated this expectation. However, efficient performance of a practical field emitter, which comprises a large number of randomly or regularly oriented CNTs, is restricted primarily due to poor junctions formed between CNTs and substrates. This study is aimed at enhancing the junction performance by way of a modified 'rooting' technique-interface control. In this process, the interface between CNTs and substrate has been tailored with different metals in an attempt to improve the CNT-substrate junction performance. Multiwall carbon nanotubes (MWCNTs) were synthesized on different interface-controlled substrates, i.e. Cu, Al, W, Si and low-temperature co-fired ceramic. All the samples produced mat-type, randomly oriented MWCNT structures. Among the four different substrates studied, MWCNT-based field emitters on Cu substrate demonstrated the best field emission response, in terms of low turn-on field, high emission current, good field enhancement factor and excellent stability in long-term operation. Emitter structures and their field emission behavior were correlated and it was shown that interface control, as an advanced 'rooting' process, plays an important role in determining the emission response from a bulk field emitter.

  3. Photocatalytic, antimicrobial activities of biogenic silver nanoparticles and electrochemical degradation of water soluble dyes at glassy carbon/silver modified past electrode using buffer solution.

    Science.gov (United States)

    Khan, Zia Ul Haq; Khan, Amjad; Shah, Afzal; Chen, Yongmei; Wan, Pingyu; Khan, Arif Ullah; Tahir, Kamran; Muhamma, Nawshad; Khan, Faheem Ullah; Shah, Hidayat Ullah

    2016-03-01

    In the present research work a novel, nontoxic and ecofriendly procedure was developed for the green synthesis of silver nano particle (AgNPs) using Caruluma edulis (C. edulis) extract act as reductant as well as stabilizer agents. The formation of AgNPs was confirmed by UV/Vis spectroscopy. The small and spherical sizes of AgNPs were conformed from high resolution transmission electron microscopy (HRTEM) analysis and were found in the range of 2-10nm, which were highly dispersion without any aggregation. The crystalline structure of AgNPs was conformed from X-ray diffraction (XRD) analysis. For the elemental composition EDX was used and FTIR helped to determine the type of organic compounds in the extract. The potential electrochemical property of modified silver electrode was also studied. The AgNPs showed prominent antibacterial motion with MIC values of 125 μg/mL against Bacillus subtilis and Staphylococcus aureus while 250 μg/mL against Escherichia coli. High cell constituents' release was exhibited by B. subtilis with 2 × MIC value of silver nanoparticles. Silver nanoparticles also showed significant DPPH free radical scavenging activity. This research would have an important implication for the synthesis of more efficient antimicrobial and antioxidant agent. The AgNP modified electrode (GC/AgNPs) exhibited an excellent electro-catalytic activity toward the redox reaction of phenolic compounds. The AgNPs were evaluated for electrochemical degradation of bromothymol blue (BTB) dyes which showed a significant activity. From the strong reductive properties it is obvious that AgNPs can be used in water sanitization and converting some organic perilous in to non-hazardous materials. The AgNPs showed potential applications in the field of electro chemistry, sensor, catalyst, nano-devices and medical. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Voltammetric sensing of bisphenol A based on a single-walled carbon nanotubes/poly{3-butyl-1-[3-(N-pyrrolyl)propyl] imidazolium ionic liquid} composite film modified electrode

    International Nuclear Information System (INIS)

    Chen, Xuemin; Ren, Tongqing; Ma, Ming; Wang, Zhengguo; Zhan, Guoqing; Li, Chunya

    2013-01-01

    Highlights: • Single-walled carbon nanotubes (SWCNTs)-ionic liquid (IL) nanocomposite fabrication. • SWCNTs-Poly-IL film modified electrode was prepared and characterized. • Voltammetric behaviors of bisphenol A were investigated thoroughly. • Sensitive voltammetric method for bisphenol A determination was developed. -- Abstract: Using carboxylic acid-functionalized single walled carbon nanotubes (SWCNTs-COO − ) as an anion and 3-butyl-1-[3-(N-pyrrolyl)propyl]imidazolium as a cation, a novel SWCNTs-COO-ionic liquid (SWCNTs-COO-IL) nanocomposite was fabricated successfully. The as-prepared SWCNTs-COO-IL nanocomposite was confirmed with transmission electron microscopy, X-ray photoelectron spectroscopy, UV–vis, FTIR and Raman spectroscopy. The SWCNTs-COO-IL nanocomposite was coated onto a glassy carbon electrode surface followed by cyclic voltammetric scanning to fabricate a SWCNTs/poly{3-butyl-1-[3-(N-pyrrolyl)propyl] imidazolium ionic liquid} composite film modified electrode (SWCNTs/Poly-IL/GCE). Scanning electron microscope and electrochemical impedance spectroscopy were used to characterize SWCNTs/Poly-IL/GCE. Electrochemical behaviors of bisphenol A (BPA) at the SWCNTs/Poly-IL/GCE were investigated thoroughly. It was found that an obvious oxidation peak appeared without reduction peak in the reverse scanning, indicating an irreversible electrochemical process. The oxidation peak currents of BPA were linearly related to scan rate in the range of 20–300 mV s −1 , suggesting an adsorption controlled process rather than a diffusion controlled process. Differential pulse voltammetry was employed for the voltammetric sensing of BPA. Experimental conditions such as film thickness, pH value, accumulation potential and time that influence the analytical performance of the SWCNTs/Poly-IL/GCE were optimized. Under optimal conditions, the oxidation peak current was linearly related to BPA concentration in the range of 5.0 × 10 −9 to 3.0 × 10 −5 mol L

  5. Biopolymer protected silver nanoparticles on the support of carbon nanotube as interface for electrocatalytic applications

    Energy Technology Data Exchange (ETDEWEB)

    Satyanarayana, M.; Kumar, V. Sunil; Gobi, K. Vengatajalabathy, E-mail: drkvgobi@gmail.com, E-mail: satyam.nitw@gmail.com [Department of Chemistry, National Institute of Technology, Warangal - 506004, Telangana (India)

    2016-04-13

    In this research, silver nanoparticles (SNPs) are prepared on the surface of carbon nanotubes via chitosan, a biopolymer linkage. Here chitosan act as stabilizing agent for nanoparticles and forms a network on the surface of carbon nanotubes. Synthesized silver nanoparticles-MWCNT hybrid composite is characterized by UV-Visible spectroscopy, XRD analysis, and FESEM with EDS to evaluate the structural and chemical properties of the nanocomposite. The electrocatalytic activity of the fabricated SNP-MWCNT hybrid modified glassy carbon electrode has been evaluated by cyclic voltammetry and electrochemical impedance analysis. The silver nanoparticles are of size ∼35 nm and are well distributed on the surface of carbon nanotubes with chitosan linkage. The prepared nanocomposite shows efficient electrocatalytic properties with high active surface area and excellent electron transfer behaviour.

  6. Carbon nanotube/platinum nanoparticle nanocomposites: preparation, characterization and application in electro oxidation of alcohols

    International Nuclear Information System (INIS)

    Kalinke, Adir H.; Zarbin, Aldo J. G.

    2014-01-01

    The synthesis and characterization of different platinum nanoparticle/ carbon nanotube nanocomposite samples are described along with the application of these nanocomposites as electrocatalysts for alcohol oxidation. Samples were prepared by a biphasic system in which platinum nanoparticles (Pt-NPs) are synthesized in situ in contact with a carbon nanotube (CNT) dispersion. Variables including platinum precursor/CNT ratio, previous chemical treatment of carbon nanotubes, and presence or absence of a capping agent were evaluated and correlated with the characteristic of the synthesized materials. Samples were characterized by Raman spectroscopy, X-ray diffraction, thermogravimetric analysis and transmission electron microscopy. Glassy carbon electrodes were modified by the nanocomposite samples and evaluated as electrocatalysts for alcohol oxidation. Current densities of 56.1 and 79.8/104.7 mA cm -2 were determined for the oxidation of methanol and ethanol, respectively. (author)

  7. Photo-assisted electrochemical oxidation of the urea onto TiO2-nanotubes modified by hematite

    Directory of Open Access Journals (Sweden)

    Waleed M. Omymen

    2017-12-01

    Full Text Available The electrochemical oxidation of the urea in near neutral pH is investigated on platinum electrode. It is shown that oxidation reaction is practically inhibited up to the potentials of ∼0.9 V. The same reaction is investigated onto electrochemically obtained titanium dioxide nanotubes modified by hematite using facile, low-cost successive ion layer adsorption and reaction (SILAR method. It is shown that such system possesses electrocatalytic activity at very low potentials, and activity can be further improved by the illumination of the electrode in the photo-assisted reaction. The possible application of the photoactive anode is considered in the application of urea based water electrolysis and urea based fuel cell. Keywords: Photoelectrochemical cell, Water electrolysis, Fuel cell, SILAR

  8. Bending analysis of agglomerated carbon nanotube-reinforced beam resting on two parameters modified Vlasov model foundation

    Science.gov (United States)

    Ghorbanpour Arani, A.; Zamani, M. H.

    2018-06-01

    The present work deals with bending behavior of nanocomposite beam resting on two parameters modified Vlasov model foundation (MVMF), with consideration of agglomeration and distribution of carbon nanotubes (CNTs) in beam matrix. Equivalent fiber based on Eshelby-Mori-Tanaka approach is employed to determine influence of CNTs aggregation on elastic properties of CNT-reinforced beam. The governing equations are deduced using the principle of minimum potential energy under assumption of the Euler-Bernoulli beam theory. The MVMF required the estimation of γ parameter; to this purpose, unique iterative technique based on variational principles is utilized to compute value of the γ and subsequently fourth-order differential equation is solved analytically. Eventually, the transverse displacements and bending stresses are obtained and compared for different agglomeration parameters, various boundary conditions simultaneously and variant elastic foundation without requirement to instate values for foundation parameters.

  9. New Electrochemically-Modified Carbon Paste Inclusion β-Cyclodextrin and Carbon Nanotubes Sensors for Quantification of Dorzolamide Hydrochloride

    Directory of Open Access Journals (Sweden)

    Nawal Ahmad Alarfaj

    2016-12-01

    Full Text Available The present article introduces a new approach to fabricate carbon paste sensors, including carbon paste, modified carbon paste inclusion β-cyclodextrin, and carbon nanotubes for the quantification of dorzolamide hydrochloride (DRZ. This study is mainly based on the construction of three different carbon paste sensors by the incorporation of DRZ with phosphotungstic acid (PTA to form dorzolamide-phosphotungstate (DRZ-PT as an electroactive material in the presence of the solvent mediator ortho-nitrophenyloctyl ether (o-NPOE. The fabricated conventional carbon paste sensor (sensor I, as well as the other modified carbon paste sensors using β-cyclodextrin (sensor II and carbon nanotubes (sensor III, have been investigated. The sensors displayed Nernstian responses of 55.4 ± 0.6, 56.4 ± 0.4 and 58.1 ± 0.2 mV·decade−1 over concentration ranges of 1.0 × 10−5–1.0 × 10−2, 1.0 × 10−6–1.0 × 10−2, and 5.0 × 10−8–1.0 × 10−2 mol·L−1 with lower detection limits of 5.0 × 10−6, 5.0 × 10−7, and 2.5 × 10−9 mol·L−1 for sensors I, II, and III, respectively. The critical performance of the developed sensors was checked with respect to the effect of various parameters, including pH, selectivity, response time, linear concentration relationship, lifespan, etc. Method validation was applied according to the international conference on harmonisation of technical requirements for registration of pharmaceuticals for human use ICH guidelines. The developed sensors were employed for the determination of DRZ in its bulk and dosage forms, as well as bio-samples. The observed data were statistically analyzed and compared with those obtained from other published methods.

  10. Bioelectrocatalytic and biosensing properties of horseradish peroxidase covalently immobilized on (3-aminopropyl)trimethoxysilane-modified titanate nanotubes

    International Nuclear Information System (INIS)

    Sovic, David; Gajovic, Andreja; Ivekovic, Damir

    2011-01-01

    Titanate nanotubes (TiNT) surface modified with (3-aminopropyl)trimethoxysilane were employed as a support for covalent immobilization of horseradish peroxidase (HRP) by using 1,4-benzoquinone as a coupling agent. Composite film-electrodes consisting of HRP-modified TiNT embedded into the porous carbon powder/Nafion matrix were fabricated and their applicability in direct bioelectrocatalytic reduction of H 2 O 2 and H 2 O 2 biosensing were investigated. An efficient direct electron transfer between the immobilized HRP molecules and the electrode was observed in the presence of H 2 O 2 at potentials lower than 600 mV (vs. Hg/Hg 2 Cl 2 /3.5 M KCl). For the HRP-TiNT-modified electrodes polarized at 0 mV, a linear dependence of the bioelectrocatalytic current on the concentration of H 2 O 2 was observed up to the concentration of H 2 O 2 equal to 10 μM, with the sensitivity of (1.10 ± 0.01) AM -1 cm -2 and the detection limit of 35 nM.

  11. A Facile Synthesis of a Palladium-Doped Polyaniline-Modified Carbon Nanotube Composites for Supercapacitors

    Science.gov (United States)

    Giri, Soumen; Ghosh, Debasis; Malas, Asish; Das, Chapal Kumar

    2013-08-01

    Supercapacitors have evolved as the premier choice of the era for storing huge amounts of charge in the field of energy storage devices, but it is still necessary to enhance their performance to meet the increasing requirements of future systems. This could be achieved either through advancing the interfaces of the material at the nanoscale or by using novel material compositions. We report a high-performance material composition prepared by combining a transition metal (palladium)-doped conductive polymer with multiwalled carbon nanotubes (MWCNTs). MWCNTs/palladium-doped polyaniline (MWCNTs/Pd/PANI) composites and multiwalled carbon nanotube/polyaniline (MWCNTs/PANI) composites (for comparison) were prepared via in situ oxidative polymerization of aniline monomer. The reported composites were characterized by Fourier-transform infrared (FTIR), x-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) studies. FESEM and TEM studies indicated the narrow size distribution of the π-conjugated polymer-protected palladium nanoparticles on the surface of the carbon nanotubes. All the electrochemical characterizations were executed using a three-electrode system in 1 M H2SO4 electrolyte. Cyclic voltammetry (CV) analysis was performed to observe the capacitive performance and redox behavior of the composites. The ion transfer behavior and cyclic stability of the composites were investigated by electrochemical impedance spectroscopy (EIS) analysis and cyclic charge-discharge (CCD) testing, respectively. The MWCNTs/Pd/PANI composite was found to exhibit an especially high specific capacitance value of 920 F/g at scan rate of 2 mV/s.

  12. Electrocatalytic behahiour of cobalt tetraamino-phthalocyanine in the presence of a composite of reduced graphene nanosheets and of multi-walled carbon nanotubes

    International Nuclear Information System (INIS)

    Nyoni, Stephen; Nyokong, Tebello

    2014-01-01

    Graphical abstract: A composite of multi-walled carbon nanotubes, reduced graphene nanosheets and cobalt tetraamino phthalocyanine was used for electrode modification, resulting in a rough surface as judged by scanning electrochemical microscopy. - Highlights: • Conjugates of multi-walled carbon nanotubes and reduced graphene nanosheets were used to modify glassy carbon electrode. • The electrode was further modified with cobalt tetraamino phthalocyanine. • The modified electrode was employed for the detection of paraquat. • A mechanism for paraquat detection using the composite electrodes is proposed. - Abstract: A composite of multi-walled carbon nanotubes (MWCNT) with reduced graphene nanosheets (rGNS-2) was developed in order to minimize the restacking of the latter. The composite was used to modify a glassy carbon electrode (GCE). GCE was further modified with cobalt tetraamino phthalocyanine (CoTAPc). The modified electrode is represented as rGNS-2-MWCNT-CoTAPc-GCE. X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electrochemical microscopy and Raman spectroscopy were used to explore into surface functionalities, morphology and topography of the nanocomposite. The rGNS-2-MWCNT-CoTAPc-GCE had a low limit of detection of 3.32 × 10 −8 M towards the detection of paraguat as a test analyte. A mechanism for paraquat detection using an rGNS-2-MWCNT-CoTAPc-GCE is also proposed in this work

  13. Interaction between Palladium Nanoparticles and Surface-Modified Carbon Nanotubes: Role of Surface Functionalities

    DEFF Research Database (Denmark)

    Zhang, Bingsen; Shao, Lidong; Zhang, Wei

    2014-01-01

    degrees C. We focus on probing the effects of oxygen and nitrogen-containing functional groups on supported palladium nanoparticles (NPs) in the model catalytic system. The stability of palladium NPs supported on CNTs depends strongly on the surface properties of CNTs. Moreover, the oxygen...... feature, instability, and subtle response of the components upon application of an external field. Herein, we use insitu TEM, electron energy loss spectroscopy, and X-ray photoelectron spectroscopy techniques to record the interaction in palladium on carbon nanotubes (CNTs) from room temperature to 600...

  14. Synergistic effect of plasma-modified halloysite nanotubes and carbon black in natural rubber-butadiene rubber blend

    NARCIS (Netherlands)

    Poikelispaa, Minna; Das, Amit; Dierkes, Wilma K.; Vuorinen, Jyrki

    2013-01-01

    Halloysite nanotubes (HNTs) were investigated concerning their suitability for rubber reinforcement. As they have geometrical similarity with carbon nanotubes, they were expected to impart a significant reinforcement effect on the rubber compounds but the dispersion of the nanofillers is difficult.

  15. Nanotube cathodes.

    Energy Technology Data Exchange (ETDEWEB)

    Overmyer, Donald L.; Lockner, Thomas Ramsbeck; Siegal, Michael P.; Miller, Paul Albert

    2006-11-01

    had a thin coating of glassy carbon surrounding them in a sheath-like manner. This glassy carbon, or nano-crystalline graphite, is likely to be a poor conductor due to phonon scattering, and should actually be deleterious for extracting electrons with electric fields. While we did not achieve the field emission reported for single-wall carbon nanotubes that spurred the idea for this project, at the year's very end, we had a breakthrough in materials growth and learned to control the growth of very-small diameter nanotubes ranging from 1.4 to 7 nm. The 1.4-nm nanotubes are single-walled and grow at only 530 C. This is the lowest temperature known to result in single-wall carbon nanotubes, and may be very important for many applications that where certain substrates could not be used due to the high temperatures commonly used for CNT growth. Critically important for field emission, these small diameter nanotubes, consisting of only a few concentric graphene cylindrical walls, do not show the presence of a poorly-conductive sheath material. Therefore, these nanotubes will almost definitely have superior field emission properties to those we already measured, and it is possible that they could provide the necessary field emission to make this project successful. Controlled spacing and lengths of these single-wall nanotubes have yet to be explored, along with correlating their structures to their improved field emission. Unfortunately, we did not discover the methods to grow these highly-crystalline and small diameter CNTs until late in the year. Since we did not achieve the necessary emission properties by mid-year, the project was ''prematurely'' terminated prior to the start of the second year. However, it should be noted that with the late developments, this work has not hit the proverbial ''brick wall''. Clearly the potential still exists to reproduce and even exceed the high emission results reported for randomly

  16. Nanotube cathodes

    International Nuclear Information System (INIS)

    Overmyer, Donald L.; Lockner, Thomas Ramsbeck; Siegal, Michael P.; Miller, Paul Albert

    2006-01-01

    had a thin coating of glassy carbon surrounding them in a sheath-like manner. This glassy carbon, or nano-crystalline graphite, is likely to be a poor conductor due to phonon scattering, and should actually be deleterious for extracting electrons with electric fields. While we did not achieve the field emission reported for single-wall carbon nanotubes that spurred the idea for this project, at the year's very end, we had a breakthrough in materials growth and learned to control the growth of very-small diameter nanotubes ranging from 1.4 to 7 nm. The 1.4-nm nanotubes are single-walled and grow at only 530 C. This is the lowest temperature known to result in single-wall carbon nanotubes, and may be very important for many applications that where certain substrates could not be used due to the high temperatures commonly used for CNT growth. Critically important for field emission, these small diameter nanotubes, consisting of only a few concentric graphene cylindrical walls, do not show the presence of a poorly-conductive sheath material. Therefore, these nanotubes will almost definitely have superior field emission properties to those we already measured, and it is possible that they could provide the necessary field emission to make this project successful. Controlled spacing and lengths of these single-wall nanotubes have yet to be explored, along with correlating their structures to their improved field emission. Unfortunately, we did not discover the methods to grow these highly-crystalline and small diameter CNTs until late in the year. Since we did not achieve the necessary emission properties by mid-year, the project was ''prematurely'' terminated prior to the start of the second year. However, it should be noted that with the late developments, this work has not hit the proverbial ''brick wall''. Clearly the potential still exists to reproduce and even exceed the high emission results reported for randomly-oriented and curly single-wall carbon nanotubes, both

  17. Fabrication of β-cyclodextrin-coated poly (diallyldimethylammonium chloride)-functionalized graphene composite film modified glassy carbon-rotating disk electrode and its application for simultaneous electrochemical determination colorants of sunset yellow and tartrazine

    International Nuclear Information System (INIS)

    Ye, Xiaoliang; Du, Yongling; Lu, Daban; Wang, Chunming

    2013-01-01

    Graphical abstract: -- Highlights: •A green and facile approach for synthesis of β-CD-PDDA-Gr at room temperature. •We present the β-CD-PDDA-Gr modified GC-RDE for simultaneous detection of SY and TT. •SY and TT's electrooxidations are both the one-electron-one-proton-transfer process. •Diffusion coefficients and standard rate constants of SY and TT were discussed. -- Abstract: We proposed a green and facile approach for the synthesis of β-cyclodextrin-coated poly(diallyldimethylammonium chloride)-functionalized graphene composite film (β-CD-PDDA-Gr) by using L-ascorbic acid (L-AA) as the reducing agent at room temperature. The β-CD-PDDA-Gr composite film modified glassy carbon-rotating disk electrode (GC-RDE) was then developed for the sensitive simultaneous determination of two synthetic food colorants: sunset yellow (SY) and tartrazine (TT). By cyclic voltammetry (CV), the peak currents of SY and TT increased obviously on the developed electrochemical sensor. The kinetic parameters, such as diffusion coefficient D and standard heterogeneous rate constant k b , were estimated by linear sweep voltammetry (LSV). Under the optimal conditions, the differential pulse voltammetry (DPV) signals of SY and TT on the β-CD-PDDA-Gr modified GC-RDE were significantly enhanced. The enhanced anodic peak currents represented the excellent analytical performance of simultaneous detection of SY and TT in the range of 5.0 × 10 −8 to 2.0 × 10 −5 mol L −1 , with a low limit of detection (LOD) of 1.25 × 10 −8 mol L −1 for SY and 1.43 × 10 −8 mol L −1 for TT (S N −1 = 3). This proposed method displayed outstanding selectivity, good stability and acceptable repeatability and reproducibility, and also has been used to simultaneously determine SY and TT in some commercial soft drinks with satisfactory results. The obtained results were compared to HPLC of analysis for those two colorants and no significant differences were found. By the treatment of the

  18. Fabrication of β-cyclodextrin-coated poly (diallyldimethylammonium chloride)-functionalized graphene composite film modified glassy carbon-rotating disk electrode and its application for simultaneous electrochemical determination colorants of sunset yellow and tartrazine

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Xiaoliang; Du, Yongling; Lu, Daban; Wang, Chunming, E-mail: wangcm@lzu.edu.cn

    2013-05-24

    Graphical abstract: -- Highlights: •A green and facile approach for synthesis of β-CD-PDDA-Gr at room temperature. •We present the β-CD-PDDA-Gr modified GC-RDE for simultaneous detection of SY and TT. •SY and TT's electrooxidations are both the one-electron-one-proton-transfer process. •Diffusion coefficients and standard rate constants of SY and TT were discussed. -- Abstract: We proposed a green and facile approach for the synthesis of β-cyclodextrin-coated poly(diallyldimethylammonium chloride)-functionalized graphene composite film (β-CD-PDDA-Gr) by using L-ascorbic acid (L-AA) as the reducing agent at room temperature. The β-CD-PDDA-Gr composite film modified glassy carbon-rotating disk electrode (GC-RDE) was then developed for the sensitive simultaneous determination of two synthetic food colorants: sunset yellow (SY) and tartrazine (TT). By cyclic voltammetry (CV), the peak currents of SY and TT increased obviously on the developed electrochemical sensor. The kinetic parameters, such as diffusion coefficient D and standard heterogeneous rate constant k{sub b}, were estimated by linear sweep voltammetry (LSV). Under the optimal conditions, the differential pulse voltammetry (DPV) signals of SY and TT on the β-CD-PDDA-Gr modified GC-RDE were significantly enhanced. The enhanced anodic peak currents represented the excellent analytical performance of simultaneous detection of SY and TT in the range of 5.0 × 10{sup −8} to 2.0 × 10{sup −5} mol L{sup −1}, with a low limit of detection (LOD) of 1.25 × 10{sup −8} mol L{sup −1} for SY and 1.43 × 10{sup −8} mol L{sup −1} for TT (S N{sup −1} = 3). This proposed method displayed outstanding selectivity, good stability and acceptable repeatability and reproducibility, and also has been used to simultaneously determine SY and TT in some commercial soft drinks with satisfactory results. The obtained results were compared to HPLC of analysis for those two colorants and no significant

  19. Combination Carbon Nanotubes with Graphene Modified Natural Graphite and Its Electrochemical Performance

    Directory of Open Access Journals (Sweden)

    DENG Ling-feng

    2017-04-01

    Full Text Available The CNTs/rGO/NG composite lithiumion battery anode material was synthesized by thermal reducing, using graphene oxide (GO and carbon nanotubes (CNTs as precursors for a 5 ∶ 3 proportion. The morphology, structure, and electrochemical performance of the composite were characterized by scanning electron microscopy(SEM, X-ray diffractometry(XRD, Fourier transform infrared spectra (FTIR and electrochemical measurements. The results show that reduced graphene oxide and carbon nanotubes form a perfect three-dimensional network structure on the surface of natural graphite. CNTs/rGO/NG composite has good rate performance and cycle life,compared with pure natural graphite.The initial discharge capacity of designed anode is 479mAh/g at 0.1C, the reversible capacity up to 473mAh/g after 100 cycles,the capacity is still 439.5mAh/g, the capacity retention rate is 92%,and the capacity is 457, 433, 394mAh/g at 0.5, 1, 5C, respectively.

  20. Carbon Nanotube Modified Screen Printed Electrodes: Pyranose Oxidase Immobilization Platform for Amperometric Enzyme Sensors

    Directory of Open Access Journals (Sweden)

    Dilek ODACI DEMIRKOL

    2017-03-01

    Full Text Available Here, a novel enzymatic biosensor was developed using multiwalled carbon nanotube including screen printed electrodes (MWCNT-SPE. Pyranose oxidase (PyOx was immobilized on the electrode surface by way of gelatin membrane and then cross-linked using glutaraldehyde. Glucose was detected at -0.7 V (vs. Ag/AgCl by watching consumed oxygen in enzymatic reaction after addition substrate. After optimization of pH and enzyme loading, the linearity was found in the range of 0.1–1.0 mM of glucose. After that, the effect of MCNT on the current was tested. Also the enzymatic biosensor including glucose oxidase instead of pyranose oxidase was prepared and the biosensor response followed for glucose. Furthermore, this system was tested for glucose analysis in soft drinks.

  1. Antibacterial and microstructure properties of titanium surfaces modified with Ag-incorporated nanotube arrays

    Energy Technology Data Exchange (ETDEWEB)

    Li, Guangzhong; Cheng, Li [State Key Laboratory of Porous Metal Materials, Northwest Institute for Nonferrous Metal Research (China); Yang, Hui-lin [Department of Orthopaedics, Wuxi People' s Hospital, Nanjing Medical University, Jiangsu Province (China); Zhao, Quan-ming, E-mail: abc8385@163.com [Department of Orthopaedics, The First Affiliated Hospital of Soochow University, Suzhou (China)

    2016-07-15

    Although titanium (Ti) and its alloys have been widely used as implants in clinical settings, failures still occur mainly due to poor bioactivity and implant-associated infections. Here, we coated Ti implants with TiO{sub 2} nanotubes (TNTs) incorporated with the antibacterial agent Ag to produce Ag-TNTs, through anodization in AgNO{sub 3} and xenon light irradiation. We characterized surface morphology and composition of the coating with scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. We investigated surface topography of the coatings by atomic force microscopy (AFM) operated in the tapping mode. The results indicate that Ag was successfully doped onto the TNTs, and that the nanoparticles were mainly distributed on the surface of TNTs. Finally, our antibacterial experiments reveal that Ag-TNTs on Ti implants exhibit excellent antibacterial activities, which promises to have significant clinical applications as implants. (author)

  2. Determination of serotonin on platinum electrode modified with carbon nanotubes/polypyrrole/silver nanoparticles nanohybrid.

    Science.gov (United States)

    Cesarino, Ivana; Galesco, Heloisa V; Machado, Sergio A S

    2014-07-01

    A new sensor has been developed by a simple electrodeposition of multi-walled carbon nanotubes (MWCNT), polypyrrole (PPy) and colloidal silver nanoparticles on the platinum (Pt) electrode surface. The Pt/MWCNT/PPy/AgNPs electrode was applied to the detection of serotonin in plasmatic serum samples using differential pulse voltammetry (DPV). The synergistic effect of MWCNT/PPy/AgNPs nanohybrid formed yielded a LOD of 0.15 μmol L(-1) (26.4 μg L(-1)). Reproducibility and repeatability values of 2.2% and 1.7%, respectively, were obtained compared to the conventional procedure. The proposed electrode can be an effective material to be used in biological analysis. Copyright © 2014 Elsevier B.V. All rights reserved.

  3. Sliding friction at poly(vinyl alcohol)-modified carbon nanotube interfaces

    Science.gov (United States)

    Zhang, Xiaohua

    2018-01-01

    The sliding friction between adjacent carbon nanotubes (CNTs) determines greatly the mechanical property of CNT assembly materials. In order to enhance the intertube friction, polymer molecules are often