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Sample records for glassy polymeric carbon

  1. Surface treatment of Glassy Polymeric Carbon artifacts for medical applications

    SciTech Connect

    Rodrigues, M. G.; Zimmerman, R. L.; Rezende, M. C.

    1999-06-10

    Glassy Polymeric Carbon (GPC) has been used for mechanical cardiac valves. GCP valves are chemically biocompatible and durable, but less thromboresistant than biological valves. Enhanced thromboresistance of mechanical cardiac components with porous surface has been demonstrated. The endothelialized tissue blood-contacting surface adheres to the porous prosthetic component and decreases the formation of thrombus. Our experience has shown that the porosity of GPC can be increased and controlled by MeV ion bombardment. We report here that the surface roughness of heat-treated GPC bombarded with C, O, Si and Au is also enhanced. The surface roughness of the ion-bombarded samples is on a smaller scale than those roughened by sand blasting (measurements made with Perthomete S and P). The roughness decreases slightly after heat treatment, in linear proportion to the shrinkage of the test piece. Possible beneficial effects of the imbedded ions on tissue adherence and thromboresistance must be determined by in vivo animal experiments.

  2. A novel pattern transfer technique for mounting glassy carbon microelectrodes on polymeric flexible substrates

    NASA Astrophysics Data System (ADS)

    Vomero, Maria; van Niekerk, Pieter; Nguyen, Vivian; Gong, Nick; Hirabayashi, Mieko; Cinopri, Alessio; Logan, Kyle; Moghadasi, Ali; Varma, Priya; Kassegne, Sam

    2016-02-01

    We present a novel technology for transferring glassy carbon microstructures, originally fabricated on a silicon wafer through a high-temperature process, to a polymeric flexible substrate such as polyimide. This new transfer technique addresses a major barrier in Carbon-MEMS technology whose widespread use so has been hampered by the high-temperature pyrolysis process (⩾900 °C), which limits selection of substrates. In the new approach presented, patterning and pyrolysis of polymer precursor on silicon substrate is carried out first, followed by coating with a polymer layer that forms a hydrogen bond with glassy carbon and then releasing the ensuing glassy carbon structure; hence, transferring it to a flexible substrate. This enables the fabrication of a unique set of glassy carbon microstructures critical in applications that demand substrates that conform to the shape of the stimulated/actuated or sensed surface. Our findings based on Fourier transform infared spectroscopy on the complete electrode set demonstrate—for the first time—that carbonyl groups on polyimide substrate form a strong hydrogen bond with hydroxyl groups on glassy carbon resulting in carboxylic acid dimers (peaks at 2660 and 2585 cm-1). This strong bond is further confirmed by a tensile test that demonstrated an almost perfect bond between these materials that behave as an ideal composite material. Further, mechanical characterization shows that ultimate strain for such a structure is as high as 15% with yield stress of ~20 MPa. We propose that this novel technology not only offers a compelling case for the widespread use of carbon-MEMS, but also helps move the field in new and exciting directions.

  3. A Reliable Homemade Electrode Based on Glassy Polymeric Carbon

    ERIC Educational Resources Information Center

    Santos, Andre L.; Takeuchi, Regina M.; Oliviero, Herilton P.; Rodriguez, Marcello G.; Zimmerman, Robert L.

    2004-01-01

    The production of a GPC-based material by submitting a cross-linked resin precursor to control thermal conditions is discussed. The precursor material is prepolymerized at 60-degree Celsius in a mold and is carbonized in inert atmosphere by slowly raising the temperature, the rise is performed to avoid change in the shape of the carbonization…

  4. Ion Beam Optimized Mechanical Characteristics of Glassy Polymeric Carbon for Medical Applications

    NASA Astrophysics Data System (ADS)

    Rodrigues, M. G.; da Cruz, N. C.; Rangel, E. C.; Zimmerman, R. L.; Ila, D.; Poker, D. B.; Hensley, D. K.

    2003-08-01

    Glassy Polymeric Carbon (GPC) has medical applications owing to its inertness and biocompatible characteristics. Commercial GPC prosthetics include mitral, aortic and hydrocephalic valves. Surface treatment of GPC increases the adhesion of endothelic tissue on GPC and avoids the occurrence of thrombus in cardiac implant. In this work, ion beam was used to improve the mechanical characteristics of GPC surface. Hardness was measured as a function of depth in precursor and GPC samples heat treated from 300 to 2500 °C before and after bombardment with energetic ions of silicon, carbon, oxygen and gold at energies of 5, 6, 8 and 10 MeV and fluences between 1.0×1013 and 1.0×1016 ions/cm2. Comparison shows that hardness increases of the bombarded samples depend on heat treatment temperature. We verify that ion bombardment promotes carbonization due to an increased linkage between the chains of the polymeric material in lateral groups that are more numerous for samples heat treated to 700 °C.

  5. Effects of Ion Beam on Nanoindentation Characteristics of Glassy Polymeric Carbon Surface

    SciTech Connect

    Rodrigues, M. G.; Da Cruz, N. C.; Rangel, E. C.; Zimmerman, R. L.; Ila, Dr. Daryush; Poker, David B; Hensley, Dale K

    2005-01-01

    Glassy polymeric carbon (GPC) is a useful material for medical applications due to its chemical inertness and biocompatible characteristics. Mitral and aortic and hydrocephalic valves are examples of GPC prosthetic devices that have been fabricated and commercialized in Brazil. In this work, ion beam was used to improve the mechanical characteristics of GPC surface and therefore to avoid the propagation of microcracks where the cardiac valves are more fragile. A control group of phenolic resin samples heat-treated at 300, 400, 700, 1000, 1500, and 2500 C was characterized by measuring their hardness and Young's reduced elastic modulus with the depth of indentation. The control group was compared to results obtained with samples heat-treated at 700, 1000, and 1500 C and bombarded with energetic ions of silicon, carbon, oxygen, and gold at energies of 5, 6, 8, and 10 MeV, respectively, with fluences between 1.0 x 10{sup 13} and 1.0 x 10{sup 16} ions/cm{sup 2}. GPC nonbombarded samples showed that hardness depends on the heat treatment temperature (HTT), with a maximum hardness for heat treatment at 1000 C. The comparison between the control group and bombarded group also showed that hardness, after bombardment, had a greater increase for samples prepared at 700 C than for samples prepared at higher temperatures. The Young's elastic modulus presents an exponential relationship with depth. The parameters obtained by fitting depend on the HTT and on the ion used in the bombardment more than on energy and fluence. The hardness results show clearly that bombardment can promote carbonization, increase the linkage between the chains of the polymeric material, and promote recombination of broken bonds in lateral groups that are more numerous for samples heat-treated at 700 C.

  6. Immobilization of Ni-Pd/core-shell nanoparticles through thermal polymerization of acrylamide on glassy carbon electrode for highly stable and sensitive glutamate detection.

    PubMed

    Yu, Huicheng; Ma, Zhenzhen; Wu, Zhaoyang

    2015-10-01

    The preparation of a persistently stable and sensitive biosensor is highly important for practical applications. To improve the stability and sensitivity of glutamate sensors, an electrode modified with glutamate dehydrogenase (GDH)/Ni-Pd/core-shell nanoparticles was developed using the thermal polymerization of acrylamide (AM) to immobilize the synthesized Ni-Pd/core-shell nanoparticles onto a glassy carbon electrode (GCE). The modified electrode was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Electrochemical data showed that the prepared biosensor had remarkably enhanced electrocatalytic activity toward glutamate. Moreover, superior reproducibility and excellent stability were observed (relative average deviation was 2.96% after continuous use of the same sensor for 60 times, and current responses remained at 94.85% of the initial value after 60 d). The sensor also demonstrated highly sensitive amperometric detection of glutamate with a low limit of detection (0.052 μM, S/N = 3), high sensitivity (4.768 μA μM(-1) cm(-2)), and a wide, useful linear range (0.1-500 μM). No interference from potential interfering species such as l-cysteine, ascorbic acid, and l-aspartate were noted. The determination of glutamate levels in actual samples achieved good recovery percentages. PMID:26481997

  7. Approaching theoretical strength in glassy carbon nanolattices

    NASA Astrophysics Data System (ADS)

    Bauer, J.; Schroer, A.; Schwaiger, R.; Kraft, O.

    2016-04-01

    The strength of lightweight mechanical metamaterials, which aim to exploit material-strengthening size effects by their microscale lattice structure, has been limited by the resolution of three-dimensional lithography technologies and their restriction to mainly polymer resins. Here, we demonstrate that pyrolysis of polymeric microlattices can overcome these limitations and create ultra-strong glassy carbon nanolattices with single struts shorter than 1 μm and diameters as small as 200 nm. They represent the smallest lattice structures yet produced--achieved by an 80% shrinkage of the polymer during pyrolysis--and exhibit material strengths of up to 3 GPa, corresponding approximately to the theoretical strength of glassy carbon. The strength-to-density ratios of the nanolattices are six times higher than those of reported microlattices. With a honeycomb topology, effective strengths of 1.2 GPa at 0.6 g cm-3 are achieved. Diamond is the only bulk material with a notably higher strength-to-density ratio.

  8. Modeling VOC Sorption and Transport in Glassy Polymeric Membranes

    NASA Astrophysics Data System (ADS)

    De Angelis, Maria Grazia; Olivieri, Luca; Sarti, G. C.

    2010-06-01

    In this work we evaluated the sorption, diffusion and permeation of a series of volatile organic compounds (VOCs) (acetone, n-butane, n-pentane, n-hexane, ethanol, methanol, chloroform and toluene) into glassy polymers of increasing fractional free volume (FFV): Polycarbonate (PC), Amorphous Teflon AF1600 and AF2400, poly-trimethylsilyl norbornene (PTMSN) and poly[1-(trimethylsilyl)-1-propyne] (PTMSP). Based on some experimental data of sorption and diffusion, and on theoretical and empirical models for the solubility and diffusion coefficients, the permeability for vapor/N2 mixtures was evaluated. These parameters are useful for the membrane separation processes and for other applications such as chemical sensors. The ideal separation factors of glassy polymeric membranes versus mixtures of VOCs and N2 were estimated at various pressures and compositions and at 25° C. The selectivity vs. permeability maps for the mixtures considered were plotted, showing that some of these materials show potentially the same selective ability of rubbery polymeric films. In particular it is shown that, the higher the FFV, the better the vapor/gas selectivity.

  9. Polymeric Carbon Dioxide

    SciTech Connect

    Yoo, C-S.

    1999-11-02

    Synthesis of polymeric carbon dioxide has long been of interest to many chemists and materials scientists. Very recently we discovered the polymeric phase of carbon dioxide (called CO{sub 2}-V) at high pressures and temperatures. Our optical and x-ray results indicate that CO{sub 2}-V is optically non-linear, generating the second harmonic of Nd: YLF laser at 527 nm and is also likely superhard similar to cubic-boron nitride or diamond. CO{sub 2}-V is made of CO{sub 4} tetrahedra, analogous to SiO{sub 2} polymorphs, and is quenchable at ambient temperature at pressures above 1 GPa. In this paper, we describe the pressure-induced polymerization of carbon dioxide together with the stability, structure, and mechanical and optical properties of polymeric CO{sub 2}-V. We also present some implications of polymeric CO{sub 2} for high-pressure chemistry and new materials synthesis.

  10. Wafer-level microstructuring of glassy carbon

    NASA Astrophysics Data System (ADS)

    Hans, Loïc. E.; Prater, Karin; Kilchoer, Cédric; Scharf, Toralf; Herzig, Hans Peter; Hermerschmidt, Andreas

    2014-03-01

    Glassy carbon is used nowadays for a variety of applications because of its mechanical strength, thermal stability and non-sticking adhesion properties. One application is glass molding that allows to realize high resolution diffractive optical elements on large areas and at affordable price appropriate for mass production. We study glassy carbon microstructuring for future precision compression molding of low and high glass-transition temperature. For applications in optics the uniformity, surface roughness, edge definition and lateral resolution are very important parameters for a stamp and the final product. We study different methods of microstructuring of glassy carbon by etching and milling. Reactive ion etching with different protection layers such as photoresists, aluminium and titanium hard masks have been performed and will be compare with Ion beam etching. We comment on the quality of the structure definition and give process details as well as drawbacks for the different methods. In our fabrications we were able to realize optically flat diffractive structures with slope angles of 80° at typical feature sizes of 5 micron and 700 nm depth qualified for high precision glass molding.

  11. How Glassy States Affect Brown Carbon Production?

    NASA Astrophysics Data System (ADS)

    Liu, P.; Li, Y.; Wang, Y.; Bateman, A. P.; Zhang, Y.; Gong, Z.; Gilles, M. K.; Martin, S. T.

    2015-12-01

    Secondary organic material (SOM) can become light-absorbing (i.e. brown carbon) via multiphase reactions with nitrogen-containing species such as ammonia and amines. The physical states of SOM, however, potentially slow the diffusion of reactant molecules in organic matrix under conditions that semisolids or solids prevail, thus inhibiting the browning reaction pathways. In this study, the physical states and the in-particle diffusivity were investigated by measuring the evaporation kinetics of both water and organics from aromatic-derived SOMs using a quartz-crystal-microbalance (QCM). The results indicate that the SOMs derived from aromatic precursors toluene and m-xylene became solid (glassy) and the in particle diffusion was significantly impeded for sufficiently low relative humidity ( < 20% RH) at 293 K. Optical properties and the AMS spectra were measured for toluene-derived SOM after ammonia exposure at varied RHs. The results suggest that the production of light-absorbing nitrogen-containing compounds from multiphase reactions with ammonia was kinetically limited in the glassy organic matrix, which otherwise produce brown carbon. The results of this study have significant implications for production and optical properties of brown carbon in urban atmospheres that ultimately influence the climate and tropospheric photochemistry.

  12. Anodic electrosynthesis of some peroxy compounds on glassy carbon electrodes

    SciTech Connect

    Khomutov, N.E.; Zakhodyakina, N.A.; Svirida, L.V.; Nesvat, N.V.

    1987-11-10

    The authors present the results of a study of the anodic electrosynthesis of hydrogen peroxide and its derivatives on glassy carbon in solutions of sodium carbonate and sodium carbonate with sodium borate. We studied the kinetics of anodic processes on glassy carbon with the aid of polarization measurements and a method for determining the concentrations of active oxygen in the anolyte and the current efficiency. The current efficiencies with respect to active oxygen obtained on glassy carbon in the mixed solution of sodium borate and sodium carbonate are close to the current efficiencies which are observed on platinum anodes in the industrial electrosynthesis of perborates.

  13. Approaching theoretical strength in glassy carbon nanolattices.

    PubMed

    Bauer, J; Schroer, A; Schwaiger, R; Kraft, O

    2016-04-01

    The strength of lightweight mechanical metamaterials, which aim to exploit material-strengthening size effects by their microscale lattice structure, has been limited by the resolution of three-dimensional lithography technologies and their restriction to mainly polymer resins. Here, we demonstrate that pyrolysis of polymeric microlattices can overcome these limitations and create ultra-strong glassy carbon nanolattices with single struts shorter than 1 μm and diameters as small as 200 nm. They represent the smallest lattice structures yet produced--achieved by an 80% shrinkage of the polymer during pyrolysis--and exhibit material strengths of up to 3 GPa, corresponding approximately to the theoretical strength of glassy carbon. The strength-to-density ratios of the nanolattices are six times higher than those of reported microlattices. With a honeycomb topology, effective strengths of 1.2 GPa at 0.6 g cm(-3) are achieved. Diamond is the only bulk material with a notably higher strength-to-density ratio. PMID:26828314

  14. Ductile mode electrochemical oxidation assisted micromachining for glassy carbon

    NASA Astrophysics Data System (ADS)

    Nam, Eunseok; Lee, Chan-Young; Jun, Martin B. G.; Min, Byung-Kwon

    2015-04-01

    Recently, a new mechanical machining process using electrochemical oxidation was reported. Electrochemical oxidation assisted micromachining was applied to the machining of glassy carbon. The material removal process of the electrochemical oxidation assisted micromachining consists of repeated cycles of oxidation followed by removal of the oxide layer. In this paper, we experimentally investigate and compare the critical chip thickness for ductile mode cutting in mechanical machining and electrochemical oxidation assisted micromachining of glassy carbon. The theoretical critical chip thickness is calculated for mechanical machining of glassy carbon and experimentally verified. The effect of electrochemical oxidation on the critical chip thickness for ductile mode micromachining is also studied for glassy carbon. It is found that the critical chip thickness is increased for the electrochemical oxidation assisted micromachining.

  15. Lithium ion diffusion through glassy carbon plate

    SciTech Connect

    Inaba, M.; Nohmi, S.; Funabiki, A.; Abe, T.; Ogumi, Z.

    1998-07-01

    The electrochemical permeation method was applied to the determination of the diffusion coefficient of Li{sup +} ion (D{sub Li{sup +}}) in a glassy carbon (GC) plate. The cell was composed of two compartments, which were separated by the GC plate. Li{sup +} ions were inserted electrochemically from one face, and extracted from the other. The flux of the permeated Li{sup +} ions was monitored as an oxidation current at the latter face. The diffusion coefficient was determined by fitting the transient current curve with a theoretical one derived from Fick's law. When the potential was stepped between two potentials in the range of 0 to 0.5 V, transient curves were well fitted with the theoretical one, which gave D{sub Li{sup +}} values on the order of 10{sup {minus}8} cm{sup {minus}2} s{sup {minus}1}. In contrast, when the potential was stepped between two potentials across 0.5 V, significant deviation was observed. The deviation indicated the presence of trap sites as well as diffusion sites for Li{sup +} ions, the former of which is the origin of the irreversible capacity of GC.

  16. Magnetoresistance, electrical conductivity, and Hall effect of glassy carbon

    SciTech Connect

    Baker, D.F.

    1983-02-01

    These properties of glassy carbon heat treated for three hours between 1200 and 2700/sup 0/C were measured from 3 to 300/sup 0/K in magnetic fields up to 5 tesla. The magnetoresistance was generally negative and saturated with reciprocal temperature, but still increased as a function of magnetic field. The maximum negative magnetoresistance measured was 2.2% for 2700/sup 0/C material. Several models based on the negative magnetoresistance being proportional to the square of the magnetic moment were attempted; the best fit was obtained for the simplest model combining Curie and Pauli paramagnetism for heat treatments above 1600/sup 0/C. Positive magnetoresistance was found only in less than 1600/sup 0/C treated glassy carbon. The electrical conductivity, of the order of 200 (ohm-cm)/sup -1/ at room temperature, can be empirically written as sigma = A + Bexp(-CT/sup -1/4) - DT/sup -1/2. The Hall coefficient was independent of magnetic field, insensitive to temperature, but was a strong function of heat treatment temperature, crossing over from negative to positive at about 1700/sup 0/C and ranging from -0.048 to 0.126 cm/sup 3//coul. The idea of one-dimensional filaments in glassy carbon suggested by the electrical conductivity is compatible with the present consensus view of the microstructure.

  17. Evidence for a glassy state in strongly driven carbon

    SciTech Connect

    Brown, C. R. D.; Gericke, D. O.; Cammarata, M.; Cho, B. I.; Gwangju Inst. of Science and Technology, Gwangju; Inst. for Basic Science, Gwangju ; Döppner, T.; Engelhorn, K.; Förster, E.; Fortmann, C.; Fritz, D.; Galtier, E.; Glenzer, S. H.; Harmand, M.; Heimann, P.; Kugland, N. L.; Lamb, D. Q.; Lee, H. J.; Lee, R. W.; Lemke, H.; Makita, M.; Moinard, A.; Murphy, C. D.; Nagler, B.; Neumayer, P.; Plagemann, K. -U.; Redmer, R.; Riley, D.; Rosmej, F. B.; Sperling, P.; Toleikis, S.; Vinko, S. M.; Vorberger, J.; White, S.; White, T. G.; Wünsch, K.; Zastrau, U.; Zhu, D.; Tschentscher, T.; Gregori, G.

    2014-06-09

    Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers. Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions. Strong Coulomb forces are predicted to induce nucleation into a crystalline ion structure within a few picoseconds. However, we observe no evidence of such phase transition after several tens of picoseconds but strong indications for an over-correlated fluid state. The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen close to their original positions in the fluid.

  18. Use of glassy carbon as a working electrode in controlled potential coulometry.

    PubMed

    Plock, C E; Vasquez, J

    1969-11-01

    Glassy carbon has been used as the working electrode in controlled potential coulometry. The results of coulometric investigations of chromium, copper, iron, uranium and neptunium are compared with results obtained with platinum or mercury working electrodes. The accuracy of results with the glassy carbon electrode compares favourably with the results obtainable with the other electrodes, but the precision is poorer. PMID:18960665

  19. Evidence for a glassy state in strongly driven carbon

    DOE PAGESBeta

    Brown, C. R. D.; Gericke, D. O.; Cammarata, M.; Cho, B. I.; Döppner, T.; Engelhorn, K.; Förster, E.; Fortmann, C.; Fritz, D.; Galtier, E.; et al

    2014-06-09

    Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers. Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions. Strong Coulomb forces are predicted to induce nucleation into a crystalline ion structure within a few picoseconds. However, we observe no evidence of such phase transition after several tens of picoseconds but strong indications for an over-correlated fluid state. The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen closemore » to their original positions in the fluid.« less

  20. Evidence for a glassy state in strongly driven carbon.

    PubMed

    Brown, C R D; Gericke, D O; Cammarata, M; Cho, B I; Döppner, T; Engelhorn, K; Förster, E; Fortmann, C; Fritz, D; Galtier, E; Glenzer, S H; Harmand, M; Heimann, P; Kugland, N L; Lamb, D Q; Lee, H J; Lee, R W; Lemke, H; Makita, M; Moinard, A; Murphy, C D; Nagler, B; Neumayer, P; Plagemann, K-U; Redmer, R; Riley, D; Rosmej, F B; Sperling, P; Toleikis, S; Vinko, S M; Vorberger, J; White, S; White, T G; Wünsch, K; Zastrau, U; Zhu, D; Tschentscher, T; Gregori, G

    2014-01-01

    Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers. Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions. Strong Coulomb forces are predicted to induce nucleation into a crystalline ion structure within a few picoseconds. However, we observe no evidence of such phase transition after several tens of picoseconds but strong indications for an over-correlated fluid state. The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen close to their original positions in the fluid. PMID:24909903

  1. Evidence for a glassy state in strongly driven carbon

    PubMed Central

    Brown, C. R. D.; Gericke, D. O.; Cammarata, M.; Cho, B. I.; Döppner, T.; Engelhorn, K.; Förster, E.; Fortmann, C.; Fritz, D.; Galtier, E.; Glenzer, S. H.; Harmand, M.; Heimann, P.; Kugland, N. L.; Lamb, D. Q.; Lee, H. J.; Lee, R. W.; Lemke, H.; Makita, M.; Moinard, A.; Murphy, C. D.; Nagler, B.; Neumayer, P.; Plagemann, K.-U.; Redmer, R.; Riley, D.; Rosmej, F. B.; Sperling, P.; Toleikis, S.; Vinko, S. M.; Vorberger, J.; White, S.; White, T. G.; Wünsch, K.; Zastrau, U.; Zhu, D.; Tschentscher, T.; Gregori, G.

    2014-01-01

    Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers. Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions. Strong Coulomb forces are predicted to induce nucleation into a crystalline ion structure within a few picoseconds. However, we observe no evidence of such phase transition after several tens of picoseconds but strong indications for an over-correlated fluid state. The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen close to their original positions in the fluid. PMID:24909903

  2. Poly(4-vinylpyridine)-coated glassy carbon flow detectors

    SciTech Connect

    Wang, J.; Golden, T.; Tuzhi, P.

    1987-03-01

    The performance of a thin-layer flow detector with a glassy carbon electrode coated with a film of protonated poly(4-vinylpyridine) is described. Substantial improvement in the selectivity of amperometric detection for liquid chromatography and flow injection systems is observed as a result of excluding cationic species from the surface. The detector response was evaluated with respect to flow rate, solute concentration, coating scheme, film-to-film reproducibility, and other variables. Despite the increase in diffusional resistance, low detection limits of ca. 0.04 and 0.10 ng of ascorbic acid and uric acid, respectively, are maintained. Protection from organic surfactants can be coupled to the charge exclusion effect by using a bilayer coating, with a cellulose acetate film atop the poly(4-vinylpyridine) layer. Applicability to urine sample is demonstrated.

  3. Jump in the electrical conductivity of shock-compressed glassy carbon

    NASA Astrophysics Data System (ADS)

    Molodets, A. M.; Golyshev, A. A.; Emel'yanov, A. N.; Shul'ga, Yu. M.; Fortov, V. E.

    2014-04-01

    The effect of high dynamic pressures on the electrical conductivity of the amorphous conducting carbon phase (glassy carbon) has been studied. The electrical conductivity of glassy carbon samples has been measured under the condition of shock compression and subsequent release wave. The history of the shock loading of glassy carbon has been calculated with the developed semiempirical equations of state. It has been shown the electrical conductivity of glassy carbon samples in the compression phase at a pressure of 45(5) GPa decreases abruptly by two orders of magnitude. In the relief phase, partially reversible change in the electrical conductivity of an amorphous carbon sample occurs. The recorded effect has been treated as a result of a partially reversible physicochemical transformation of shock-compressed amorphous carbon.

  4. Au nanoparticles and graphene quantum dots co-modified glassy carbon electrode for catechol sensing

    NASA Astrophysics Data System (ADS)

    Zhao, Xuan; He, Dawei; Wang, Yongsheng; Hu, Yin; Fu, Chen

    2016-03-01

    In this letter, the gold nanoparticles and graphene quantum dots were applied to the modification of glassy carbon electrode for the detection of catechol. The synergist cooperation between gold nanoparticles and graphene quantum dots can increase specific surface area and enhance electronic and catalytic properties of glassy carbon electrode. The detection limit of catechol is 0.869 μmol/L, demonstrating the superior detection efficiency of the gold nanoparticles and graphene quantum dots co-modified glassy carbon electrode as a new sensing platform.

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

    PubMed

    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. PMID:23200396

  6. CO2 reduction catalyzed by mercaptopteridine on glassy carbon.

    PubMed

    Xiang, Dongmei; Magana, Donny; Dyer, R Brian

    2014-10-01

    The catalytic reduction of CO2 is of great current interest because of its role in climate change and the energy cycle. We report a pterin electrocatalyst, 6,7-dimethyl-4-hydroxy-2-mercaptopteridine (PTE), that catalyzes the reduction of CO2 and formic acid on a glassy carbon electrode. Pterins are natural cofactors for a wide range of enzymes, functioning as redox mediators and C1 carriers, but they have not been exploited as electrocatalysts. Bulk electrolysis of a saturated CO2 solution in the presence of the PTE catalyst produces methanol, as confirmed by gas chromatography and (13)C NMR spectroscopy, with a Faradaic efficiency of 10-23%. FTIR spectroelectrochemistry detected a progression of two-electron reduction products during bulk electrolysis, including formate, aqueous formaldehyde, and methanol. A transient intermediate was also detected by FTIR and tentatively assigned as a PTE carbamate. The results demonstrate that PTE catalyzes the reduction of CO2 at low overpotential and without the involvement of any metal. PMID:25259884

  7. Surface micro-structuring of glassy carbon for precision glass molding of diffractive optical elements

    NASA Astrophysics Data System (ADS)

    Prater, Karin; Dukwen, Julia; Scharf, Toralf; Herzig, Hans Peter; Hermerschmidt, Andreas

    2014-09-01

    Glassy carbon is used nowadays for a variety of applications because of its mechanical strength, thermal stability and non-sticking adhesion properties. This makes it also a suitable candidate as mold material for precision compression molding of low and high glass-transition temperature materials. To fabricate molds for diffractive optics a highresolution structuring technique is needed. We introduce a process that allows the micro-structuring of glassy carbon by reactive ion etching. Key parameters such as uniformity, surface roughness, edge definition and lateral resolution are discussed. They are the most relevant parameters for a stamp in optical applications. The use of titanium as a hard mask makes it possible to achieve a reasonable selectivity of 4:1, which has so far been one of the main problems in microstructuring of glassy carbon. We investigate the titanium surface structure with its 5-10 nm thick layer of TiO2 grains and its influence on the shape of the hard mask. In our fabrication procedure we were able to realize optically flat diffractive structures with slope angles of more than 80° at typical feature sizes of 5 μm and at 700 nm depth. The fabricated glassy carbon molds were applied to thermal imprinting onto different glasses. Glassy carbon molds with 1 mm thickness were tested with binary optical structures. Our experiments show the suitability of glassy carbon as molds for cost efficient mass production with a high quality.

  8. Structural Modifications And Mechanical Degradation Of Ion Irradiated Glassy Polymer Carbon

    NASA Astrophysics Data System (ADS)

    Abunaemeh, Malek; Seif, Mohamed; Elsamadicy, Abdalla; Muntele, Claudiu; Ila, Daryush

    2011-06-01

    The TRISO fuel has been used in some of the Generation IV nuclear reactor designs. It consists of a fuel kernel of UOx coated with several layers of materials with different functions. Pyrolytic carbon (PyC) is one of the materials in the layers. In this study we investigate the possibility of using Glassy Polymeric Carbon (GPC) as an alternative to PyC. GPC is used for artificial heart valves, heat-exchangers, and other high-tech products developed for the space and medical industries. This lightweight material can maintain dimensional and chemical stability in adverse environment and very high temperatures (up to 3000 °C). In this work, we are comparing the changes in physical and microstructure properties of GPC after exposure to irradiation fluence of 5 MeV Ag equivalent to a 1 displacement per atom (dpa) at samples prepared at 1000, 1500 and 2000 °C. The GPC material is manufactured and tested at the Center for Irradiation Materials (CIM) at Alabama A&M University. Transmission electron microscopy (TEM) and Raman spectroscopy were used for analysis.

  9. Electrochemical oxidation of butein at glassy carbon electrodes.

    PubMed

    Tesio, Alvaro Yamil; Robledo, Sebastián Noel; Fernández, Héctor; Zon, María Alicia

    2013-06-01

    The electrochemical oxidation of flavonoid butein is studied at glassy carbon electrodes in phosphate and citrate buffer solutions of different pH values, and 1M perchloric acid aqueous solutions by cyclic and square wave voltammetries. The oxidation peak corresponds to the 2e(-), 2H(+) oxidation of the 3,4-dihydroxy group in B ring of butein, given the corresponding quinone species. The overall electrode process shows a quasi-reversible behavior and an adsorption/diffusion mixed control at high butein bulk concentrations. At low butein concentrations, the electrode process shows mainly an adsorption control. Butein surface concentration values were obtained from the charge associated with the adsorbed butein oxidation peaks, which are in agreement with those values expected for the formation of a monolayer of adsorbate in the concentration range from 1 to 5μM. Square wave voltammetry was used to perform a full thermodynamic and kinetics characterization of the butein surface redox couple. Therefore, from the combination of the "quasi-reversible maximum" and the "splitting of the net square wave voltammetric peak" methods, values of (0.386±0.003) V, (0.46±0.04), and 2.7×10(2)s(-1) were calculated for the formal potential, the anodic transfer coefficient, and the formal rate constant, respectively, of the butein overall surface redox process in pH4.00 citrate buffer solutions. These results will be then used to study the interaction of butein, and other flavonoids with the deoxyribonucleic acid, in order to better understand the potential therapeutic applications of these compounds. PMID:23434740

  10. Low-Potential Stable NADH Detection at Carbon-Nanotube-Modified Glassy Carbon Electrodes

    SciTech Connect

    Musameh, Mustafa; Wang, Joseph; Merkoci, Arben; Lin, Yuehe )

    2002-11-22

    Carbon-nanotube (CNT) modified glassy-carbon electrodes exhibiting strong and stable electrocatalytic response toward NADH are described. A substantial (490 mV) decrease in the overvoltage of the NADH oxidation reaction (compared to ordinary carbon electrodes) is observed using single-wall and multi-wall carbon-nanotube coatings, with oxidation starting at ca.?0.05V (vs. Ag/AgCl; pH 7.4). Furthermore, the NADH amperometric response of the coated electrodes is extremely stable, with 96 and 90% of the initial activity remaining after 60min stirring of 2x10-4M and 5x10-3M NADH solutions, respectively (compared to 20 and 14% at the bare surface). The CNT-coated electrodes thus allow highly-sensitive, low-potential, stable amperometric sensing. Such ability of carbon-nanotubes to promote the NADH electron-transfer reaction suggests great promise for dehydrogenase-based amperometric biosensors.

  11. Sensitive Electrochemical Detection of Enzymatically-generated Thiocholine at Carbon Nanotube Modified Glassy Carbon Electrode

    SciTech Connect

    Liu, Guodong; Riechers, Shawn L.; Mellen, Maria C.; Lin, Yuehe

    2005-11-01

    A carbon nanotube modified glassy-carbon (CNT/GC) electrode was used for enhancing the sensitivity of electrochemical measurements of enzymatically-generated thiocholine. Cyclic voltammetric and amperometric characteristics of thiocholine at CNT/GC, glassy carbon, carbon paste, and gold electrodes were compared. The CNT layer leads to a greatly improved anodic detection of enzymatically generated thiocholine product including lower oxidation overpotential (0.15 V) and higher sensitivity because of its electrocatalytic activity, fast electron transfer and large surface area. The sensor performance was optimized with respect to the operating conditions. Under the optimal batch conditions, a detection limit of 5 ?10 -6 mol/L was obtained with good precision (RSD = 5.2%, n=10). Furthermore, the attractive response of thiocholine on a CNT/GC electrode has allowed it to be used for constant-potential flow injection analysis. The detection limit was greatly improved to 0.3 ?10-6 mol/L. The high sensitivity electrochemical detection of enzymatically generated thiocholine with a CNT sensing platform holds great promise to prepare an acetylcholinesterase biosensor for monitoring organophosphate pesticides and nerve agents.

  12. Impact of Carbon Nanomaterials on Actin Polymerization.

    PubMed

    Dong, Ying; Sun, Haiyan; Li, Xu; Li, Xin; Zhao, Lina

    2016-03-01

    Many nanomaterials have entered people's daily lives and impact the normal process of biological entities consequently. As one kind of the important nanomaterials, carbon based nanomaterials have invoked a lot of concerns from scientific researches because of their unique physicochemical properties. In eukaryotes, actin is the most abundantly distributed protein in both cytoplasm and cell nucleus, and closely controls the cell proliferation and mobility. Recently, many investigations have found some carbon based nanomaterials can affect actin cytoskeleton remarkably, including fullerenes derivatives, carbon nanotubes, graphene and its derivatives. However, these interaction processes are complicated and the underlying mechanism is far from being understood clearly. In this review, we discussed the different mechanisms of carbon nanomaterials impact on actin polymerization into three pathways, as triggering the signaling pathways from carbon nanomaterials outside of cells, increasing the production of reactive oxygen species from carbon nanomaterials inside of cells and direct interaction from carbon nanomaterials inside of cells. As a result, the dimension and size of carbon nanomaterials play a key role in regulation of actin cytoskeleton. Furthermore, we forecasted the possible investigation strategy for meeting the challenges of the future study on this topic. We hope the findings are helpful in understanding the molecular mechanism in carbon nanomaterials regulating actin polymerization, and provide new insight in novel nanomedicine development for inhibition tumor cell migration. PMID:27455649

  13. Polymerization initated at sidewalls of carbon nanotubes

    NASA Technical Reports Server (NTRS)

    Tour, James M. (Inventor); Hudson, Jared L. (Inventor); Krishnamoorti, Ramanan (Inventor); Yurekli, Koray (Inventor); Mitchell, Cynthia A. (Inventor)

    2011-01-01

    The present invention is directed to aryl halide (such as aryl bromide) functionalized carbon nanotubes that can be utilized in anionic polymerization processes to form polymer-carbon nanotube materials with improved dispersion ability in polymer matrices. In this process the aryl halide is reacted with an alkyllithium species or is reacted with a metal to replace the aryl-bromine bond with an aryl-lithium or aryl-metal bond, respectively. It has further been discovered that other functionalized carbon nanotubes, after deprotonation with a deprotonation agent, can similarly be utilized in anionic polymerization processes to form polymer-carbon nanotube materials. Additionally or alternatively, a ring opening polymerization process can be performed. The resultant materials can be used by themselves due to their enhanced strength and reinforcement ability when compared to their unbound polymer analogs. Additionally, these materials can also be blended with pre-formed polymers to establish compatibility and enhanced dispersion of nanotubes in otherwise hard to disperse matrices resulting in significantly improved material properties. The resultant polymer-carbon nanotube materials can also be used in drug delivery processes due to their improved dispersion ability and biodegradability, and can also be used for scaffolding to promote cellular growth of tissue.

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

    PubMed Central

    Wang, Huiying; Liu, Mingyue; Hu, Xinxi; Li, Mei; Xiong, Xingyao

    2013-01-01

    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. PMID:24287539

  15. Amperometric biosensor based on glassy carbon electrode modified with long-length carbon nanotube and enzyme

    NASA Astrophysics Data System (ADS)

    Furutaka, Hajime; Nemoto, Kentaro; Inoue, Yuki; Hidaka, Hiroki; Muguruma, Hitoshi; Inoue, Hitoshi; Ohsawa, Tatsuya

    2016-05-01

    An amperometric biosensor based on a glassy carbon electrode modified with long-length multiwalled carbon nanotubes (MWCNTs) and enzyme nicotinamide-adenine-dinucleotide-dependent glucose dehydrogenase (GDH) is presented. We demonstrate the effect of the MWCNT length on the amperometric response of the enzyme biosensor. The long length of MWCNT is 200 µm (average), whereas the normal length of MWCNT is 1 µm (average). The response of the long MWCNT–GDH electrode is 2 times more sensitive than that of the normal-length MWCNT–GDH electrode in the concentration range from 0.25–35 mM. The result of electrochemical impedance spectroscopy measurements suggest that the long-length MWCNT–GDH electrode formed a better electron transfer network than the normal-length one.

  16. Polymerization Initiated at the Sidewalls of Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Tour, James M.; Hudson, Jared L.

    2011-01-01

    A process has been developed for growing polymer chains via anionic, cationic, or radical polymerization from the side walls of functionalized carbon nanotubes, which will facilitate greater dispersion in polymer matrices, and will greatly enhance reinforcement ability in polymeric material.

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

    PubMed

    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. PMID:26838915

  18. In situ PM-IRRAS of a glassy carbon electrode/deep eutectic solvent interface.

    PubMed

    Vieira, Luciana; Schennach, Robert; Gollas, Bernhard

    2015-05-21

    The interface of a 1 : 2 molar choline chloride/ethylene glycol deep eutectic solvent with a glassy carbon electrode has been investigated by polarization modulation reflection-absorption spectroscopy (PM-IRRAS). Temporal spectral changes at open circuit potential show the experiments to be surface sensitive and indicate slow adsorption of electrolyte molecules on the electrode surface. In situ spectroelectrochemical PM-IRRAS measurements reveal characteristic potential-dependent changes of band intensities and wavenumber-shifts in the surface spectra. The potential dependent spectral changes are discussed in terms of adsorption, reduction, desorption and reorientation of choline cations at the interface. Analogies are drawn to the ionic layer structure proposed for the architecture of electrode/ionic liquid interfaces. The results show that in situ PM-IRRAS is generally applicable to glassy carbon electrodes and to electrode interfaces with deep eutectic solvents. PMID:25908481

  19. Low substrate temperature deposition of diamond coatings derived from glassy carbon

    DOEpatents

    Holcombe, Jr., Cressie E.; Seals, Roland D.

    1995-01-01

    A process for depositing a diamond coating on a substrate at temperatures less than about 550.degree. C. A powder mixture of glassy carbon and diamond particles is passed through a high velocity oxy-flame apparatus whereupon the powders are heated prior to impingement at high velocity against the substrate. The powder mixture contains between 5 and 50 powder volume percent of the diamond particles, and preferably between 5 and 15 powder volume percent. The particles have a size from about 5 to about 100 micrometers, with the diamond particles being about 5 to about 30 micrometers. The flame of the apparatus provides a velocity of about 350 to about 1000 meters per second, with the result that upon impingement upon the substrate, the glassy carbon is phase transformed to diamond as coaxed by the diamond content of the powder mixture.

  20. Low substrate temperature deposition of diamond coatings derived from glassy carbon

    DOEpatents

    Holcombe, C.E. Jr.; Seals, R.D.

    1995-09-26

    A process is disclosed for depositing a diamond coating on a substrate at temperatures less than about 550 C. A powder mixture of glassy carbon and diamond particles is passed through a high velocity oxy-flame apparatus whereupon the powders are heated prior to impingement at high velocity against the substrate. The powder mixture contains between 5 and 50 powder volume percent of the diamond particles, and preferably between 5 and 15 powder volume percent. The particles have a size from about 5 to about 100 micrometers, with the diamond particles being about 5 to about 30 micrometers. The flame of the apparatus provides a velocity of about 350 to about 1000 meters per second, with the result that upon impingement upon the substrate, the glassy carbon is phase transformed to diamond as coaxed by the diamond content of the powder mixture. 2 figs.

  1. Growth of InP single crystals by liquid encapsulated Czochralski (LEC) using glassy-carbon crucibles

    SciTech Connect

    Oliveira, C.E.M. de; Miskys, C.R.; Carvalho, M.M.G. de

    1996-12-31

    Using a high pressure puller and Glassy-Carbon crucibles, undoped InP single crystals weighing 100g and with 25 mm diameter were grown in the <100> direction. The residual carrier concentration of samples, measure by the Van der Pauw method at 300K, was about 5 {times} 10{sup 15}cm{sup {minus}3}, result as good as those obtained with Quartz crucibles with the advantage that Glassy-Carbon crucibles are fully reusable.

  2. Graphene oxide-mediated electrochemistry of glucose oxidase on glassy carbon electrodes.

    PubMed

    Castrignanò, Silvia; Valetti, Francesca; Gilardi, Gianfranco; Sadeghi, Sheila J

    2016-01-01

    Glucose oxidase (GOD) was immobilized on glassy carbon electrodes in the presence of graphene oxide (GO) as a model system for the interaction between GO and biological molecules. Lyotropic properties of didodecyldimethylammonium bromide (DDAB) were used to stabilize the enzymatic layer on the electrode surface resulting in a markedly improved electrochemical response of the immobilized GOD. Transmission electron microscopy images of the GO with DDAB confirmed the distribution of the GO in a two-dimensional manner as a foil-like material. Although it is known that glassy carbon surfaces are not ideal for hydrogen peroxide detection, successful chronoamperometric titrations of the GOD in the presence of GO with β-d-glucose were performed on glassy carbon electrodes, whereas no current response was detected upon β-d-glucose addition in the absence of GO. The GOD-DDAB-GO system displayed a high turnover efficiency and substrate affinity as a glucose biosensor. The simplicity and ease of the electrode preparation procedure of this GO/DDAB system make it a good candidate for immobilizing other biomolecules for fabrication of amperometric biosensors. PMID:25939764

  3. Voltammetric determination of adenosine and guanosine using fullerene-C(60)-modified glassy carbon electrode.

    PubMed

    Goyal, Rajendra N; Gupta, Vinod K; Oyama, Munetaka; Bachheti, Neeta

    2007-02-28

    A fullerene-C(60)-modified glassy carbon electrode (GCE) is used for the simultaneous determination of adenosine and guanosine by differential pulse voltammetry. Compared to a bare glassy carbon electrode, the modified electrode exhibits an apparent shift of the oxidation potentials in the cathodic direction and a marked enhancement in the voltammetric peak current response for both the biomolecules. Linear calibration curves are obtained over the concentration range 0.5muM-1.0mM in 0.1M phosphate buffer solution at pH 7.2 with a detection limit of 3.02x10(-7)M and 1.45x10(-7)M for individual determination of adenosine and guanosine, respectively. The interference studies showed that the fullerene-C(60)-modified glassy carbon electrode exhibited excellent selectivity in the presence of hypoxanthine, xanthine, uric acid and ascorbic acid. The proposed procedure was successfully applied to detect adenosine and guanosine in human blood plasma and urine, without any preliminary pre-treatment. PMID:19071420

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

    NASA Astrophysics Data System (ADS)

    Chang, Gang; Shu, Honghui; Ji, Kai; Oyama, Munetaka; Liu, Xiong; He, Yunbin

    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-2 mM-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.

  5. Glassy Carbon as an Absolute Intensity Calibration Standard for Small-Angle Scattering

    NASA Astrophysics Data System (ADS)

    Zhang, Fan; Ilavsky, Jan; Long, Gabrielle G.; Quintana, John P. G.; Allen, Andrew J.; Jemian, Pete R.

    2010-05-01

    Absolute calibration of small-angle scattering (SAS) intensity data (measured in terms of the differential scattering cross section per unit sample volume per unit solid angle) is essential for many important aspects of quantitative SAS analysis, such as obtaining the number density, volume fraction, and specific surface area of the scatterers. It also enables scattering data from different instruments (light, X-ray, or neutron scattering) to be combined, and it can even be useful to detect the existence of artifacts in the experimental data. Different primary or secondary calibration methods are available. In the latter case, absolute intensity calibration requires a stable artifact with the necessary scattering profile. Glassy carbon has sometimes been selected as this intensity calibration standard. Here we review the spatial homogeneity and temporal stability of one type of commercially available glassy carbon that is being used as an intensity calibration standard at a number of SAS facilities. We demonstrate that glassy carbon is sufficiently homogeneous and stable during routine use to be relied upon as a suitable standard for absolute intensity calibration of SAS data.

  6. Glassy carbon as an absolute intensity calibration standard for small-angle scattering.

    SciTech Connect

    Zhang, F.; Ilavsky, J.; Long, G.; Allen, A.; Quintana, J.; Jemian, P.; NIST

    2010-05-01

    Absolute calibration of small-angle scattering (SAS) intensity data (measured in terms of the differential scattering cross section per unit sample volume per unit solid angle) is essential for many important aspects of quantitative SAS analysis, such as obtaining the number density, volume fraction, and specific surface area of the scatterers. It also enables scattering data from different instruments (light, X-ray, or neutron scattering) to be combined, and it can even be useful to detect the existence of artifacts in the experimental data. Different primary or secondary calibration methods are available. In the latter case, absolute intensity calibration requires a stable artifact with the necessary scattering profile. Glassy carbon has sometimes been selected as this intensity calibration standard. Here we review the spatial homogeneity and temporal stability of one type of commercially available glassy carbon that is being used as an intensity calibration standard at a number of SAS facilities. We demonstrate that glassy carbon is sufficiently homogeneous and stable during routine use to be relied upon as a suitable standard for absolute intensity calibration of SAS data.

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

    PubMed

    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. PMID:26882954

  8. Flow injection catalase activity measurement based on gold nanoparticles/carbon nanotubes modified glassy carbon electrode.

    PubMed

    El Nashar, Rasha Mohamed

    2012-07-15

    Amperometric flow injection method of hydrogen peroxide analysis was developed based on catalase enzyme (CAT) immobilization on a glassy carbon electrode (GC) modified with electrochemically deposited gold nanoparticles on a multiwalled carbon nanotubes/chitosan film. The resulting biosensor was applied to detect hydrogen peroxide with a linear response range 1.0×10(-7)-2.5×10(-3)M with a correlation coefficient 0.998 and response time less than 10s. The optimum conditions of film deposition such as potential applied, deposition time and pH were tested and the flow injection conditions were optimized to be: flow rate of 3ml/min, sample volume 75μl and saline phosphate buffer of pH 6.89. Catalase enzyme activity was successfully determined in liver homogenate samples of rats, raised under controlled dietary plan, using a flow injection analysis system involving the developed biosensor simultaneously with spectrophotometric detection, which is the common method of enzymatic assay. PMID:22817944

  9. Reactive Carbon Nano-Onion Modified Glassy Carbon Surfaces as DNA Sensors for Human Papillomavirus Oncogene Detection with Enhanced Sensitivity.

    PubMed

    Bartolome, Joanne P; Echegoyen, Luis; Fragoso, Alex

    2015-07-01

    Glassy carbon electrodes were modified with small carbon nano-onions (CNOs) and activated by electrografting of diazonium salts bearing terminal carboxylic acid and maleimide groups. The CNO-modified surfaces were characterized by ESEM and AFM microscopy as well as by electrochemical techniques. The modified electrodes were used for the amperometric detection of a model DNA target sequence associated with the human papillomavirus by immobilizing short recognition sequences by amidation or thiol-maleimide reactions. The analytical parameters of the developed biosensors were compared with glassy carbon electrodes without CNOs. In both cases, the incorporation of CNOs resulted in an enhancement in sensitivity and a decrease in detection limits ascribed to a combination of large surface areas and enhanced electron transfer properties of the CNO-modified electrodes. These results offer promise for the construction of other CNO-based biomolecule detection platforms with enhanced sensitivities. PMID:26067834

  10. Cationic Polymerization of Vegetable Oils in Supercritical Carbon Dioxide

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Polymers derived from vegetable oils have been prepared in supercritical carbon dioxide (scCO2) medium by cationic polymerization. Boron trifluoride diethyl etherate BF3.O(C2H2)2 are used as initiator. Influences of polymerization temperature, initiator amount, and carbon dioxide pressure on the m...

  11. Laser micromilling of convex microfluidic channels onto glassy carbon for glass molding dies

    NASA Astrophysics Data System (ADS)

    Tseng, Shih-Feng; Chen, Ming-Fei; Hsiao, Wen-Tse; Huang, Chien-Yao; Yang, Chung-Heng; Chen, Yu-Sheng

    2014-06-01

    This study reports the fabrication of convex microfluidic channels on glassy carbon using an ultraviolet laser processing system to produce glass molding dies. The laser processing parameters, including various laser fluences and scanning speeds of galvanometers, were adjusted to mill a convex microchannel on a glassy carbon substrate to identify the effects of material removal. The machined glassy carbon substrate was then applied as a glass molding die to fabricate a glass-based microfluidic biochip. The surface morphology, milled width and depth, and surface roughness of the microchannel die after laser micromilling were examined using a three-dimensional confocal laser scanning microscope. This study also investigates the transcription rate of microchannels after the glass molding process. To produce a 180 μm high microchannel on the GC substrate, the optimal number of milled cycles, laser fluence, and scanning speed were 25, 4.9 J/cm2, and 200 mm/s, respectively. The width, height, and surface roughness of milled convex microchannels were 119.6±0.217 μm, 180.26±0.01 μm, and 0.672±0.08 μm, respectively. These measured values were close to the predicted values and suitable for a glass molding die. After the glass molding process, a typical glass-based microchannel chip was formed at a molding temperature of 660 °C and the molding force of 0.45 kN. The transcription rates of the microchannel width and depth were 100% and 99.6%, respectively. Thus, the proposed approach is suitable for performing in chemical, biochemical, or medical reactions.

  12. Plasma-polymerized carbon disulfide thin-film rechargeable batteries

    SciTech Connect

    Sadhir, R.K.; Schoch, K.F. Jr.

    1996-06-01

    This paper discusses the results on deposition conditions, rates of polymerization, and properties of carbon disulfide films prepared by two techniques, viz., plasma polymerization and argon-plasma-assisted polymerization of carbon disulfide. A higher rate of polymerization and sulfur content was obtained for carbon disulfide films prepared by the plasma-polymerization technique. A Li/LiClO{sub 4} propylene carbonate/PPCS cell was assembled using lithium foil, 2 M LiClO{sub 4}/PC electrolyte with polyolefin separator, and PPCS deposited on Pt foil. The electrode area was 1.3 cm{sup 2}. The cell cycled reversibly between 1 and 3 V and retained its capacity (5 mA h/g) well over 12 cycles. 14 refs., 11 figs., 5 tabs.

  13. Amperometric sensor based on tricobalt tetroxide nanoparticles-graphene nanocomposite film modified glassy carbon electrode for determination of tyrosine.

    PubMed

    Jiang, Lin; Gu, Shuqing; Ding, Yaping; Ye, Daixin; Zhang, Zhen; Zhang, Fenfen

    2013-07-01

    An electrochemical sensor based on tricobalt tetroxide nanoparticles-graphene nanocomposite film modified glassy carbon electrodes (GCEs) for sensitive determination of L-tyrosine (L-Tyr) was presented here. The nanoparticles were fabricated by electro-polymerization technology. Scanning electron microscopy was implemented to characterize morphology of the nanocomposite film. The electron transfer behavior of modified electrodes was investigated in 5 mM K3[Fe(CN)6]/K4[Fe(CN)6] solution using cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The electrochemical response of modified electrodes toward L-Tyr was investigated by cyclic voltammetry (CV), square wave voltammetry (SWV), amperometry in detail. The results indicated that synergistic effect of Co3O4 NPs and graphene film dramatically improved the conductivity and sensitivity of the sensor. Under optimal conditions, a wide linear relationship between the responses and L-Tyr concentrations ranging from 1.0×10(-8) to 4.0×10(-5) mol L(-1) was obtained with a comparatively low detection limit of 1.0×10(-9) mol L(-1). Furthermore, the sensor also displays excellent sensitivity and high stability. To further study the practical applicability of the fabricated sensor, it was applied to detect real samples and the received results were satisfactory. PMID:23475062

  14. Electrocatalytic oxidation of ascorbic acid using a poly(aniline-co-m-ferrocenylaniline) modified glassy carbon electrode.

    PubMed

    Chairam, Sanoe; Sriraksa, Worawit; Amatatongchai, Maliwan; Somsook, Ekasith

    2011-01-01

    A poly(aniline-co-m-ferrocenylaniline) was successfully synthesized on a glassy carbon electrode (GCE) by electrochemical copolymerization using a scan potential range from -0.3 to +0.9 V (vs. Ag/AgCl) in 0.5 M H2SO4 containing 30% acetonitrile (ACN), 0.1 M aniline (Ani) and 0.005 M m-ferrocenyaniline (m-FcAni). The field emission scanning electron microscope (FESEM) and electrochemical methods were used to characterize the poly(Ani-co-m-FcAni) modified electrode. The poly(Ani-co-m-FcAni)/GCE exhibited excellent electrocatalytic oxidation of ascorbic acid (AA) in citrate buffer solution (CBS, pH 5.0). The anodic peak potential of AA was shifted from +0.55 V at the bare GCE to +0.25 V at the poly(Ani-co-m-FcAni)/GCE with higher current responses than those seen on the bare GCE. The scan number at the 10th cycle was selected as the maximum scan cycle in electrochemical polymerization. The limit of detection (LOD) was estimated to be 2.0 μM based on the signal-to-noise ratio (S/N = 3). The amperometric responses demonstrated an excellent selectivity for AA determination over glucose (Glu) and dopamine (DA). PMID:22346636

  15. Electrocatalytic Oxidation of Ascorbic Acid Using a Poly(aniline-co-m-ferrocenylaniline) Modified Glassy Carbon Electrode

    PubMed Central

    Chairam, Sanoe; Sriraksa, Worawit; Amatatongchai, Maliwan; Somsook, Ekasith

    2011-01-01

    A poly(aniline-co-m-ferrocenylaniline) was successfully synthesized on a glassy carbon electrode (GCE) by electrochemical copolymerization using a scan potential range from −0.3 to +0.9 V (vs. Ag/AgCl) in 0.5 M H2SO4 containing 30% acetonitrile (ACN), 0.1 M aniline (Ani) and 0.005 M m-ferrocenyaniline (m-FcAni). The field emission scanning electron microscope (FESEM) and electrochemical methods were used to characterize the poly(Ani-co-m-FcAni) modified electrode. The poly(Ani-co-m-FcAni)/GCE exhibited excellent electrocatalytic oxidation of ascorbic acid (AA) in citrate buffer solution (CBS, pH 5.0). The anodic peak potential of AA was shifted from +0.55 V at the bare GCE to +0.25 V at the poly(Ani-co-m-FcAni)/GCE with higher current responses than those seen on the bare GCE. The scan number at the 10th cycle was selected as the maximum scan cycle in electrochemical polymerization. The limit of detection (LOD) was estimated to be 2.0 μM based on the signal-to-noise ratio (S/N = 3). The amperometric responses demonstrated an excellent selectivity for AA determination over glucose (Glu) and dopamine (DA). PMID:22346636

  16. Electrochemical behavior of triflusal, aspirin and their metabolites at glassy carbon and boron doped diamond electrodes.

    PubMed

    Enache, Teodor Adrian; Fatibello-Filho, Orlando; Oliveira-Brett, Ana Maria

    2010-08-01

    The electrochemical behavior of triflusal (TRF) and aspirin (ASA), before and after hydrolysis in water and in alkaline medium using two different electrode surfaces, glassy carbon and boron doped diamond, was study by differential pulse voltammetry over a wide pH range. The hydrolysis products are 2-(hydroxyl)-4-(trifluoromethyl)-benzoic acid (HTB) for triflusal and salicylic acid (SA) for aspirin, which in vivo represent their main metabolites. The hydrolysis processes were also followed by spectrophotometry. The UV results showed complete hydrolysis after one hour for TRF and after two hours for ASA in alkaline solution. The glassy carbon electrode enables only indirect determination of TRF and ASA through the electrochemical detection of their hydrolysis products HTB and SA, respectively. The oxidation processes of HTB and SA are pH dependent and involve different numbers of electrons and protons. Moreover, the difference between the oxidation peak potential of SA and HTB was equal to 100 mV in the studied pH range from 1 to 8 due to the CF3 of the aromatic ring of HTB molecule. Due to its wider oxidation potential range, the boron doped diamond electrode was used to study the direct oxidation of TRF and ASA, as well as of their respective metabolites HTB and SA. PMID:20402644

  17. Multilevel micro-structuring of glassy carbon for precision glass molding of diffractive optical elements

    NASA Astrophysics Data System (ADS)

    Prater, Karin; Dukwen, Julia; Scharf, Toralf; Herzig, Hans Peter; Plöger, Sven; Hermerschmidt, Andreas

    2015-03-01

    A consumer market for diffractive optical elements in glass can only be created if high efficient elements are available at affordable prices. In diffractive optics the efficiency and optical properties increases with the number of levels used, but in the same way the costs are multiplied by the number if fabrication steps. Replication of multilevel diffractive optical elements in glass would allow cost efficient fabrication but a suitable mold material is needed. Glassy carbon shows a high mechanical strength, thermal stability and non-sticking adhesion properties, which makes it an excellent candidate as mold material for precision compression molding of low and high glass-transition temperature materials. We introduce an 8 level micro structuring process for glassy carbon molds with standard photolithography and a Ti layer as hard mask for reactive ion etching. The molds were applied to thermal imprinting onto low and high transition temperature glass. Optical performance was tested for the molded samples with different designs for laser beamsplitters. The results show a good agreement to the design specification. Our result allow us to show limitations of our fabrication technique and we discussed the suitability of precision glass molding for cost efficient mass production with a high quality.

  18. Mediatorless solar energy conversion by covalently bonded thylakoid monolayer on the glassy carbon electrode.

    PubMed

    Lee, Jinhwan; Im, Jaekyun; Kim, Sunghyun

    2016-04-01

    Light reactions of photosynthesis that take place in thylakoid membranes found in plants or cyanobacteria are among the most effective ways of utilizing light. Unlike most researches that use photosystem I or photosystem II as conversion units for converting light to electricity, we have developed a simple method in which the thylakoid monolayer was covalently immobilized on the glassy carbon electrode surface. The activity of isolated thylakoid membrane was confirmed by measuring evolving oxygen under illumination. Glassy carbon surfaces were first modified with partial or full monolayers of carboxyphenyl groups by reductive C-C coupling using 4-aminobenzoic acid and aniline and then thylakoid membrane was bioconjugated through the peptide bond between amine residues of thylakoid and carboxyl groups on the surface. Surface properties of modified surfaces were characterized by cyclic voltammetry, contact angle measurements, and electrochemical impedance spectroscopy. Photocurrent of 230 nA cm(-2) was observed when the thylakoid monolayer was formed on the mixed monolayer of 4-carboxylpheny and benzene at applied potential of 0.4V vs. Ag/AgCl. A small photocurrent resulted when the 4-carboxyphenyl full monolayer was used. This work shows the possibility of solar energy conversion by directly employing the whole thylakoid membrane through simple surface modification. PMID:26625272

  19. Electrochemical study of functionalization on the surface of a chitin/platinum-modified glassy carbon paste electrode.

    PubMed

    Sugawara, Kazuharu; Yugami, Asako; Terui, Norifumi; Kuramitz, Hideki

    2009-11-01

    To functionalize chitin surfaces using proteins, we developed a glucose oxidase (GOD)-chitin/platinum-modified glassy carbon paste electrode (GCPE) as a model. In a weakly acidic solution, negatively charged GOD were immobilized by the protonated acetylamide groups on chitin. When the electrode was immersed in a solution containing GOD, the enzyme was readily immobilized due to the electrostatic interaction. In addition, measurements were performed using electrodes made with powders of different sizes because sensor performance depends on the particle sizes of glassy carbon powder. PMID:19907096

  20. Nucleation and growth of thin films of the organic conductor TTF-iodide over glassy carbon. Electrochemical and spectroelectrochemical study.

    PubMed

    Gómez, L; Rodríguez-Amaro, R

    2009-04-21

    On the basis of the electrochemical and spectroelectrochemical behavior of thin films of TTF over a glassy carbon electrode in iodide media, a new, more complete mechanism for the electrode processes involved is proposed. The voltammetric and chronoamperometric results for the films can be explained in light of a recently developed nucleation-growth model involving a layer-by-layer mechanism. Also, their in situ UV-vis spectral data expand the available knowledge about the overall mechanism and the nature of the compound formed over the glassy carbon electrode. PMID:19366229

  1. Polymerization of Plant Oils in Carbon Dioxide Medium

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lewis acid catalyst, boron trifluoride diethyl etherate (BF3•OEt2), catalyzed polymerization of epoxidized soybean oil (ESO) in liquid carbon dioxide was conducted in an effort to develop useful biodegradable polymers. The ring-opening polymerization was employed at mild conditions, such as at room...

  2. Electrografting of 3-Aminopropyltriethoxysilane on a Glassy Carbon Electrode for the Improved Adhesion of Vertically Oriented Mesoporous Silica Thin Films.

    PubMed

    Nasir, Tauqir; Zhang, Lin; Vilà, Neus; Herzog, Grégoire; Walcarius, Alain

    2016-05-01

    Vertically oriented mesoporous silica has proven to be of interest for applications in a variety of fields (e.g., electroanalysis, energy, and nanotechnology). Although glassy carbon is widely used as an electrode material, the adherence of silica deposits is rather poor, causing mechanical instability. A solution to improve the adhesion of mesoporous silica films onto glassy carbon electrodes without compromising the vertical orientation and the order of the mesopores will greatly contribute to the use of this kind of modified carbon electrode. We propose here the electrografting of 3-aminopropyltriethoxysilane on glassy carbon as a molecular glue to improve the mechanical stability of the silica film on the electrode surface without disturbing the vertical orientation and the order of the mesoporous silica obtained by electrochemically assisted self-assembly. These findings are supported by a series of surface chemistry techniques such as X-ray photoelectron spectroscopy, scanning and transmission electron microscopy, and cyclic voltammetry. Finally, methylviologen was used as a model redox probe to investigate the cathodic potential region of both glassy carbon and indium tin oxide electrodes modified with mesoporous silica in order to demonstrate further the interest in the approach developed here. PMID:27065214

  3. Electron transfer kinetics at a biotin/avidin patterned glassy carbon electrode.

    PubMed

    Nowall, W B; Dontha, N; Kuhr, W G

    1998-11-15

    Photolithographic techniques using a laser interference pattern were used to attach photobiotin to micron-sized stripes on the surface of a carbon electrode. Fluorophore-tagged avidin was attached to this spatially-patterned biotin with essentially no loss in spatial resolution. The kinetics of the glassy carbon surface were examined to see if electron transfer sites could indeed be segregated from the attachment sites of photobiotin-immobilized avidin. The ECL of luminol and SECM were used to verify the segregation between underivatized sites (which exhibit normal electron transfer kinetics) and extensively derivatized biotin/avidin surfaces (which presumably exhibit slow electron transfer kinetics). Both techniques were found to be capable of differentiating the protein-covered surface from bare carbon with sufficient resolution to tell whether a significant portion of the carbon surface is still active and available to detect the product of an enzyme generated analyte. These results indicate that extensive biotin/avidin derivatization of the surface does decrease the electron transfer rate of a carbon electrode, and that the photolithographic approach was able to modify specific sections of the electrode surface, while leaving other regions untouched and available for facile electron transfer. This leads to a more general protocol for the construction of enzyme-based biosensors which utilize diffusable mediators. PMID:9871979

  4. Emissivity of a multibeam electron gun with a glassy carbon field-emission cathode

    NASA Astrophysics Data System (ADS)

    Bushuev, N. A.; Glukhova, O. E.; Grigor'ev, Yu. A.; Ivanov, D. V.; Kolesnikova, A. S.; Nikolaev, A. A.; Shalaev, P. D.; Shesterkin, V. I.

    2016-02-01

    A multibeam triode electron gun with a glassy carbon field-emission cathode that is intended for an O-type microwave amplifier is studied. The electric field strength and the current density at the microtips versus the distance to the center of a cell of the cathode-grid unit are calculated. Calculation data are compared with experimental results. It is shown that about 70% of the cathode current in each cell is accounted for by microtips arranged in a circumferential ring no wider than 20 μm. The field-emission current density inside the ring exceeds 40 A/cm2, and the current per microtip equals 43.1 μA.

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

    PubMed Central

    Radi, Abd-Elgawad; Abd El-Ghany, Nadia; Wahdan, Tarek

    2016-01-01

    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. PMID:27242945

  6. Easy modification of glassy carbon electrode for simultaneous determination of ascorbic acid, dopamine and uric acid.

    PubMed

    Thiagarajan, Soundappan; Tsai, Tsung-Hsuan; Chen, Shen-Ming

    2009-04-15

    A glassy carbon electrode (GCE) has been modified by electrochemical oxidation in mild acidic media (0.1 mol l(-1) H(2)SO(4)) and could be applied for individual and simultaneous determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA). Oxidized GCE shows a single redox couple (E(0)'=-2.5 mV) which is based on the formation functional groups during the electrochemical pretreatment process. Proposed GCE successfully decreases the over potentials for the oxidation process of these species (AA, DA and UA) comparing with bare GCE. The oxidized GCE has its own simplicity, stability, high sensitivity and possesses the potential for simultaneous determination of AA, DA and UA. PMID:19162467

  7. An electrochemically aminated glassy carbon electrode for simultaneous determination of hydroquinone and catechol.

    PubMed

    Wang, Xiuyun; Xi, Min; Guo, Mengmeng; Sheng, Fangmeng; Xiao, Guang; Wu, Shuo; Uchiyama, Shunichi; Matsuura, Hiroaki

    2016-02-01

    In this contribution, a very simple and reliable strategy based on the easy modification of a glassy carbon electrode (GCE) by pre-electrolyzing GCE in ammonium carbamate aqueous solution was employed for the simultaneous determination of hydroquinone (HQ) and catechol (CC). Compared with bare GCE, the incorporation of nitrogen into the GCE surface structure improved the electrocatalytic properties of GCE towards the electro-oxidation of HQ and CC. The nitrogen-introduced GCE (N-GCE) was evaluated for the simultaneous detection of HQ and CC and the linear ranges for HQ and CC were both from 5 to 260 μM. Their detection limits were both evaluated to be 0.2 μM (S/N = 3). The present method was applied for the determination of HQ and CC in real river water samples with recoveries of 95.0-102.1%. In addition, a possible detection mechanism of HQ and CC was discussed. PMID:26613194

  8. Toward the Control of the Creation of Mixed Monolayers on Glassy Carbon Surfaces by Amine Oxidation.

    PubMed

    Groppi, Jessica; Bartlett, Philip N; Kilburn, Jeremy D

    2016-01-18

    A versatile and simple methodology for the creation of mixed monolayers on glassy carbon (GC) surfaces was developed, using an osmium-bipyridyl complex and anthraquinone as model redox probes. The work consisted in the electrochemical grafting on GC of a mixture of mono-protected diamine linkers in varying ratios which, after attachment to the surface, allowed orthogonal deprotection. After optimisation of the deprotection conditions, it was possible to remove one of the protecting groups selectively, couple a suitable osmium complex and cap the residual free amines. The removal of the second protecting group allowed the coupling of anthraquinone. The characterisation of the resulting surfaces by cyclic voltammetry showed the variation of the surface coverage of the two redox centres in relation to the initial ratio of the linking amine in solution. PMID:26637108

  9. Determination of trimebutine in pharmaceuticals by differential pulse voltammetry at a glassy carbon electrode.

    PubMed

    Adhoum, Nafaâ; Monser, Lotfi

    2005-07-15

    The differential pulse voltammetric (DPV) determination of trimebutine (TMB) was achieved at a glassy carbon electrode in acetonitrile/0.1 M LiClO4. Trimebutine gave two irreversible, diffusion controlled peaks at 740 and 1318 mV versus Ag/AgCl reference electrode, respectively. The second oxidation peak was used to determine trimebutine concentrations in the range 1-50 microg ml(-1) with a detection limit (3sigmam) of 0.3 microg ml(-1). Precision of the method (RSD, n=6) within- and between-days obtained from six determinations at 5 microg ml(-1) was found to be 0.7 and 1.1%, respectively. The method was successfully applied to the quantitation of TMB in granule dosage form (Debridat) and recoveries between 98.4 and 101% were obtained. Excipients did not interfere with the assay and the results agreed well with those determined by previously established HPLC method. PMID:15967289

  10. Voltammetric Determination of Dopamine in Human Serum with Amphiphilic Chitosan Modified Glassy Carbon Electrode

    PubMed Central

    Wang, Cheng Yin; Wang, Zhi Xian; Zhu, Ai Ping; Hu, Xiao Ya

    2006-01-01

    An improvement of selectivity for electrochemical detection of dopamine (DA) with differential pulse voltammetry is achieved by covalently modifying a glassy carbon electrode (GCE) with O-carboxymethylchitosan (OCMCS). The amphiphilic chitosan provides electrostatic accumulation of DA onto the electrode surface. In a phosphate buffer solution (pH 6.0), a pair of well-defined reversible redox waves of DA was observed at the OCMCS/GCE with a ΔEp of 52 mV. The anodic peak current obtained from the differential pulse voltammetry of dopamine was linearly dependent on its concentration in the range of 6.0 × 10-8 to 7.0 × 10-6 M, with a correlation coefficient of 0.998. The detection limit (S/N = 3) was found to be 1.5 × 10-9 M. The modified electrode had been applied to the determination of DA in human serum samples with satisfactory results.

  11. Amperometric sensing of hydrogen peroxide using glassy carbon electrode modified with copper nanoparticles

    SciTech Connect

    Sophia, J.; Muralidharan, G.

    2015-10-15

    In this paper, fabrication of glassy carbon electrode (GCE) modified with nano copper particles is discussed. The modified electrode has been tested for the non-enzymatic electrochemical detection of hydrogen peroxide (H{sub 2}O{sub 2}). The copper nanoparticles (Cu NPs) were prepared employing a simple chemical reduction method. The presence of Cu NPs was confirmed through UV–visible (UV–vis) absorption spectroscopy and X-ray diffraction (XRD) analysis. The size and morphology of the particles were investigated using transmission electron microscopy (TEM). The electrochemical properties of the fabricated sensor were studied via cyclic voltammetry (CV), chronoamperometry and electrochemical impedance spectroscopy (EIS). The electrochemical sensor displayed excellent performance features towards H{sub 2}O{sub 2} detection exhibiting wide linear range, low detection limit, swift response time, good reproducibility and stability.

  12. Multilevel micro-structuring of glassy carbon molds for precision glass molding

    NASA Astrophysics Data System (ADS)

    Prater, Karin; Dukwen, Julia; Scharf, Toralf; Herzig, Hans Peter; Plöger, Sven; Hermerschmidt, Andreas

    2015-09-01

    Replication techniques for diffractive optical elements (DOEs) in soft materials such as plastic injection molding are state of the art. For precision glass molding in glasses with high transition temperatures, molds with extreme thermal resistivity, low chemical reactivity and high mechanical strength are needed. Glassy Carbon can be operated up to 2000°C making it possible to mold almost all glasses including Fused Silica with a transition temperatures above 1060°C. For the structuring of Glassy Carbon wafers photolithography and a RIE process is used. We have developed a process using Si as a hard mask material. If the flow rates of the etching gases O2 and SF6 are chosen properly, high selectivity of GC to Si 19:1 can be achieved, which provides excellent conditions to realize high resolution elements with feature size down to 1 micron and fulfills requirements for optical applications. We fabricated several multilevel GC molds with 8 levels of structuring. Two different optical functionalities were implemented: 6x6 array beamsplitter and 1x4 linear beamsplitter. The molds were applied for precision glass molding of a low Tg glass L-BAL 42 (from Ohara) with a transition temperature of 565°C. Their optical performance was measured. A more detailed analysis of the impact of mold fabrication defects on optical performance is done. Rigorous coupled wave analysis simulations are performed, where we included fabrication constrains such as duty cycle, edge depth errors, wall verticality and misalignment errors. We will compare the results with the design specifications and discuss the influence of fabrication errors introduced during the different process steps.

  13. Effect of deposition conditions on properties of plasma polymerized carbon disulfide

    SciTech Connect

    Sadhir, R.K.; Schoch, K.F. Jr.

    1995-12-31

    This paper discusses the results on deposition conditions, rates of polymerization and properties of carbon disulfide films prepared by two techniques viz. plasma polymerization and argon-plasma-assisted polymerization of carbon disulfide. A higher rate of polymerization and sulfur content was obtained for carbon disulfide films prepared by plasma polymerization technique. The ultimate objective of this research work was to prepare thin film solid state batteries using the optimized carbon disulfide polymer films deposited by plasma techniques, as active material.

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

    PubMed

    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. PMID:26652361

  15. Facile synthesis of gradient mesoporous carbon monolith based on polymerization-induced phase separation

    NASA Astrophysics Data System (ADS)

    Xu, Shunjian; Luo, Yufeng; Zhong, Wei; Xiao, Zonghu; Luo, Yongping; Ou, Hui; Zhao, Xing-Zhong

    2014-06-01

    In this paper, a gradient mesoporous carbon (GMC) monolith derived from the mixtures of phenolic resin (PF) and ethylene glycol (EG) was prepared by a facile route based on polymerization-induced phase separation under temperature gradient (TG). A graded biphasic structure of PF-rich and EG-rich phases was first formed in preform under a TG, and then the preform was pyrolyzed to obtain the GMC monolith. The TG is mainly induced by the thermal resistance of the preferential phase separation layer at high temperature region. The pore structure of the monolith changes gradually along the TG direction. When the TG varies from 58°C to 29°C, the pore size, apparent porosity and specific surface area of the monolith range respectively from 18 nm to 83 nm, from 32% to 39% and from 140.5 m2/g to 515.3 m2/g. The gradient porous structure of the monolith is inherited from that of the preform, which depends on phase separation under TG in the resin mixtures. The pyrolysis mainly brings about the contraction of the pore size and wall thickness as well as the transformation of polymerized PF into glassy carbon.

  16. Sensitivity and selectivity determination of bisphenol A using SWCNT-CD conjugate modified glassy carbon electrode.

    PubMed

    Gao, Yong; Cao, Yu; Yang, Duanguang; Luo, Xujun; Tang, Yiming; Li, Huaming

    2012-01-15

    In this study, we demonstrated a highly sensitive electrochemical sensor for the determination of bisphenol A (BPA) in aqueous solution by using single-walled carbon nanotubes (SWCNTs)/β-cyclodextrin (β-CD) conjugate (SWCNT-CD) modified glassy carbon electrode (GCE). The cyclic voltammetry results show that the modified GCE exhibits strong catalytic activity toward the oxidation of BPA with a well-defined cyclic voltammetric peak at 0.543 V. The response current exhibits a linear range between 10.8 nM and 18.5 μM with a high sensitivity (1256 μA mM(-1)). The detection limit of BPA is 1.0 nM (S/N=3). The enhanced performance of the fabricated sensor can be attributed to the combination of the excellent electrocatalytic properties of SWCNTs and the molecular recognition ability of β-CD. The sensor was successfully applied to determine BPA leached from real plastic samples with good recovery, ranging from 95% to 103%. PMID:22100222

  17. Bucky-gel coated glassy carbon electrodes, for voltammetric detection of femtomolar leveled lead ions.

    PubMed

    Wan, Qijin; Yu, Fen; Zhu, Lina; Wang, Xiaoxia; Yang, Nianjun

    2010-10-15

    Femtomolar (fM) leveled lead ions were electrochemically detected using a bucky-gel coated glassy carbon electrode and differential pulse anodic stripping voltammetry. The bucky-gel was composed of dithizone, ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate), and multi-walled carbon nanotubes (MWCNTs). The fabrication of the bucky-gel coated electrode was optimized. The modified electrode was characterized with voltammetry, electrochemical impedance spectroscopy, and chronoamperometry. After the accumulation of lead ions into the bucky-gel modified electrode at -1.2V vs. saturated calomel electrode (SCE) for 5 min in a pH 4.4 sodium acetate-acetate acid buffer solution, differential pulse anodic stripping voltammograms of the accumulated lead show an anodic wave at -0.58 V. The anodic peak current is detectable for lead ions in the concentration range from 1.0 μM down to 500 fM. The detection limit is calculated to be 100 fM. The proposed method was successfully applied for the detection of lead ions in lake water. PMID:20875583

  18. Molecularly imprinted poly(4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid) modified glassy carbon electrode as an electrochemical theophylline sensor.

    PubMed

    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. PMID:27157734

  19. Electron photoemission from platinum and palladium microdeposits on glassy carbon into the solution

    SciTech Connect

    Yakushev, V.V.; Bagotskii, V.S.; Skundin, A.M.

    1984-08-01

    It was of interest to the authors to compare the electrocatalytic and photoemission properties of microdeposits in other systems. Platinum and palladium microdeposits on glassy carbon were selected as such systems in the present work. The procedure used in the photoemission measurements has been previously described. All measurements were conducted in 1 N KOH. A mercury-mercuric oxide electrode served as reference electrode. The true surface areas of the platinum microdeposits were measured potentiodynamically in terms of hydrogen adsorption and oxygen desorption, while that of the palladium microdeposits was measured in terms of oxygen desorption. The results of the present work yield the important conclusion that the changes which occur in the density of electronic states in the microdeposits because of their contact with the support depend on potential, i.e., on the position of the Fermi level. It is found that the enhancement of the photoemission currents is attended by an increase, and the depression of the photoemission currents is attended by a decrease in electrocatalytic activity.

  20. Au nanoparticles/poly(caffeic acid) composite modified glassy carbon electrode for voltammetric determination of acetaminophen.

    PubMed

    Li, Tianbao; Xu, Juan; Zhao, Lei; Shen, Shaofei; Yuan, Maosen; Liu, Wenming; Tu, Qin; Yu, Ruijin; Wang, Jinyi

    2016-10-01

    An Au nanoparticles/poly(caffeic acid) (AuNPs/PCA) composite modified glassy carbon (GC) electrode was prepared by successively potentiostatic technique in pH 7.4 phosphate buffer solution containing 0.02mM caffeic acid and 1.0mM HAuCl4. Electrochemical characterization of the AuNPs/PCA-GC electrode was investigated by electrochemical impedance spectroscopy and cyclic voltammetry. The electrochemical behavior of acetaminophen (AP) at the AuNPs/PCA-GC electrode was also studied by cyclic voltammetry. Compared with bare GC and poly(caffeic acid) modified GC electrode, the AuNPs/PCA-GC electrode was exhibited excellent electrocatalytic activity toward the oxidation of AP. The plot of catalytic current versus AP concentration showed two linear segments in the concentration ranges 0.2-20µM and 50-1000µM. The detection limit of 14 nM was obtained by using the first range of the calibration plot. The AuNPs/PCA-GC electrode has been successfully applied and validated by analyzing AP in blood, urine and pharmaceutical samples. PMID:27474318

  1. Pulse Laser Deposition Fabricating Gold Nanoclusters on a Glassy Carbon Surface for Nonenzymatic Glucose Sensing.

    PubMed

    Shu, Honghui; Chang, Gang; Wang, Zhiqiang; Li, Pai; Zhang, Yuting; He, Yunbin

    2015-01-01

    A One-step technique for depositing gold nanoclusters (GNCs) onto the surface of a glassy carbon (GC) plate was developed by using pulse laser deposition (PLD) with appropriate process parameters. The method is simple and clean without using any templates, surfactants, or stabilizers. The experimental factors (pulse laser number and the pressure of inert gas (Ar)) that affect the morphology and structure of GNCs, and thus affect the electrocatalytic oxidation performance towards glucose were systematically investigated by means of transmission electron microscopy (TEM) and electrochemical methods (cyclic voltammograms (CV) and chronoamperometry methods). The GC electrode modified by GNCs exhibited a rapid response time (about 2 s), a broad linear range (0.1 to 20 mM), and good stability. The sensitivity was estimated to be 31.18 μA cm(-2) mM(-1) (vs. geometric area), which is higher than that of the Au bulk electrode. It has a good resistance to the common interfering species, such as ascorbic acid (AA), uric acid (UA) and 4-acetaminophen (AP). Therefore, this work has demonstrated a simple and effective sensing platform for the nonenzymatic detection of glucose, and can be used as a new material for a novel non-enzymatic glucose sensor. PMID:26165282

  2. Graphene modified glassy carbon sensor for the determination of aspirin metabolites in human biological samples.

    PubMed

    Purushotham, Meruva; Gupta, Pankaj; Goyal, Rajendra N

    2015-10-01

    A graphene modified glassy carbon (GR/GCE) sensor has been developed for the determination of aspirin metabolites 2,3- and 2,5-dihydroxybenzoic acids (2,3- and 2,5-DHB). The modified sensor was characterized by Field Emission Scanning Electron Microscopy and Electrochemical Impedance Spectroscopy. The electrochemical behavior of 2,3- and 2,5-DHB was investigated by cyclic and square wave voltammetry. The modified sensor exhibited excellent electrocatalytic activity for the oxidation of 2,3- and 2,5-DHB, leading to a remarkable enhancement in the peak current as compared to the bare sensor. The results were attributed to the enhanced surface area and high conductivity of GR. The anodic peak currents of 2,3- and 2,5-DHB were found to be linear in the concentration range of 1-150 µM and 1-200 µM with the detection limits of 47 nM and 51 nM, respectively. The sensor was capable to determine 2,5-DHB effectively without any interference from the uric acid and other metabolites present in the urine samples. The practical utility of GR/GCE has been successfully demonstrated for the determination of 2,5-DHB in the urine samples of persons undergoing treatment with aspirin. PMID:26078167

  3. Application of low-temperature glassy carbon films in solid-phase microextraction.

    PubMed

    Giardina, M; Olesik, S V

    2001-12-15

    Low-temperature glassy carbon (LTGC) films were investigated as a sorbent coating for solid-phase microextraction because of its uniquely selective adsorptive characteristics. The selectivity of these coatings is primarily controlled by shape characteristics of the solute molecule and the final processing temperature used to form the LTGC, demonstrating unique adsorptive characteristics compared to commercial phases. The LTGC films were prepared by first coating porous silica particles with a diethylnyl oligomer precursor and then heat curing at temperatures between 300 and 1000 degrees C to form the LTGC. Then, using a sol-gel process, the LTGC-coated silica particles were immobilized onto stainless steel fibers and subsequently used for headspace and liquid extractions followed by GC-FID analysis. The selectivity of the LTGC is demonstrated by the extraction of a variety of aromatic hydrocarbons as well as the taste and odor contaminants geosmin, 2-methylisoborneol, and 2,4,6-trichloroanisole commonly found in water supplies. The data show that the LTGC coating has the highest affinity for molecules with the greatest cross-sectional surface area and polarizability and that this selective mechanism increases as a function of LTGC processing temperature. PMID:11791552

  4. Structure, texture, and properties of superconductive electrolytic niobium coatings on glassy carbon

    NASA Astrophysics Data System (ADS)

    Kolosov, V. N.; Shevyrev, A. A.

    2016-01-01

    Superconductive electrolytic niobium coatings 0.1-100 μm thick are prepared via electrochemical deposition onto SU-2000 glassy carbon substrates in (LiF + NaF + KF)eut-K2NbF7 molten salt. Their structure, texture, and residual stresses are investigated by X-ray diffraction methods. It is shown that, when depositing the coatings, the diffusion superconductive layer of niobium carbide is formed at the substrate-coating interface. The sequence of changes in the axis of the texture of niobium coating from <100> through <211> to a textureless state with an increase in their thickness is established. It is found that, in the interval 0.5-5 μm, the sign of the stress changes (compressive stresses change into tensile stresses) and it reaches its maximum value. With an increase in the coating thickness from 5 to 100 μm, tensile stresses decrease from 345 to 80 MPa. It is shown that the coatings formed can be used as the material for creating a working layer of a superconducting cryogenic gyroscope rotor.

  5. Behavior of the Ru-bda water oxidation catalyst covalently anchored on glassy carbon electrodes

    DOE PAGESBeta

    Matheu, Roc; Francàs, Laia; Chernev, Petko; Ertem, Mehmed Z.; Batista, Victor; Haumann, Michael; Sala, Xavier; Llobet, Antoni

    2015-05-07

    Electrochemical reduction of the dizaonium complex, [RuII(bda)(NO)(N–N2)2]3+, 23+ (N–N22+ is 4-(pyridin-4-yl) benzenediazonium and bda2– is [2,2'-bipyridine]-6,6'-dicarboxylate), in acetone produces the covalent grafting of this molecular complex onto glassy carbon (GC) electrodes. Multiple cycling voltammetric experiments on the GC electrode generates hybrid materials labeled as GC-4, with the corresponding Ru-aqua complex anchored on the graphite surface. GC-4 has been characterized at pH = 7.0 by electrochemical techniques and X-ray absorption spectroscopy (XAS) and has been shown to act as an active catalyst for the oxidation of water to dioxygen. This new hybrid material has a lower catalytic performance than its counterpartmore » in homogeneous phase and progressively decomposes to form RuO2 at the electrode surface. The resulting metal oxide attached at the GC electrode surface, GC-RuO2, is a very fast and rugged heterogeneous water oxidation catalyst with TOFis of 300 s–1 and TONs >45000. The observed performance is comparable to the best electrocatalysts reported so far, at neutral pH.« less

  6. Electropolymerized molecular imprinting on glassy carbon electrode for voltammetric detection of dopamine in biological samples.

    PubMed

    Kiss, Laszlo; David, Vasile; David, Iulia Gabriela; Lazăr, Paul; Mihailciuc, Constantin; Stamatin, Ioan; Ciobanu, Adela; Ştefănescu, Cristian Dragoş; Nagy, Livia; Nagy, Géza; Ciucu, Anton Alexandru

    2016-11-01

    A simple and reliable method for preparing a selective dopamine (DA) sensor based on a molecularly imprinted polymer of ethacridine was proposed. The molecularly imprinted polymer electrode was prepared through electrodepositing polyethacridine-dopamine film on the glassy carbon electrode and then removing DA from the film via chemical induced elution. The molecular imprinted sensor was tested by cyclic voltammetry as well as by differential pulse voltammetry (DPV) to verify the changes in oxidative currents of DA. In optimized DPV conditions the oxidation peak current was well-proportional to the concentration of DA in the range from 2.0×10(-8)M up to 1×10(-6)M. The limit of detection (3σ) of DA was found to be as low as 4.4nM, by the proposed sensor that could be considered a sensitive marker of DA depletion in Parkinson's disease. Good reproducibility with relative standard deviation of 1.4% and long term stability within two weeks were also observed. The modified sensor was validated for the analysis of DA in deproteinized human serum samples using differential pulse voltammetric technique. PMID:27591643

  7. Amperometric ascorbic acid sensor based on doped ferrites nanoparticles modified glassy carbon paste electrode.

    PubMed

    Dimitrijević, Teodora; Vulić, Predrag; Manojlović, Dragan; Nikolić, Aleksandar S; Stanković, Dalibor M

    2016-07-01

    In this study, a novel electrochemical sensor for quantification of ascorbic acid with amperometric detection in physiological conditions was constructed. For this purpose, cobalt and nickel ferrites were synthesized using microwave and ultrasound assistance, characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray powder diffraction (XRPD), and used for modification of glassy carbon paste electrode (GCPE). It was shown that introducing these nanoparticles to the structure of GCPE led to increasing analytical performance. Co ferrite modified GCPE (CoFeGCPE) showed better characteristics toward ascorbic acid sensing. The limit of detection (LOD) obtained by sensor was calculated to be 0.0270 mg/L, with linear range from 0.1758 to 2.6010 mg/L. This sensor was successfully applied for practical analysis, and the obtained results demonstrated that the proposed procedure could be a promising replacement for the conventional electrode materials and time-consuming and expensive separation methods. PMID:27059753

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

    PubMed Central

    Piech, Robert; Rumin, Martyna; Paczosa-Bator, Beata

    2015-01-01

    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. PMID:25741451

  9. Electrochemical investigation of methyl parathion at gold-sodium dodecylbenzene sulfonate nanoparticles modified glassy carbon electrode.

    PubMed

    Li, Chunya; Wang, Zhengguo; Zhan, Guoqin

    2011-01-01

    A gold/sodium dodecylbenzene sulfonate nanoparticles modified glassy carbon electrode (nano-Au/SDBS/GCE) was electrochemically fabricated with a constant potential at -0.4V. The obtained nano-Au/SDBS/GCE was characterized with scanning electronic microscopy, X-ray photoelectron spectroscopy and electrochemical techniques. Electrochemical behaviors of methyl parathion at the nano-Au/SDBS/GCE were thoroughly investigated. Compared to the unmodified electrode, the peak current obviously increased and the oxidation peak potential negatively shifted. These changes indicated that the composite nanoparticles possess good electrocatalytic performance on the electrochemical reaction of methyl parathion. Experimental parameters such as deposition time, pH value and accumulation conditions were optimized. Under optimum conditions, the peak current corresponding to the oxidation of the hydroxylamine group was found in a good linear relationship with the methyl parathion concentration. In addition, a calibration curve with excellent linearity was obtained in the concentration range from 5.0×10(-7)molL(-1) to 1.0×10(-4)molL(-1) with an estimated detection limit of 8.6×10(-8)molL(-1) (S/N=3). The successful determination of methyl parathion in real samples demonstrated the usefulness and potential applications of this method. PMID:20832258

  10. Electron Transfer to a Phosphomolybdate Monolayer on Glassy Carbon: Ambivalent Effect of Protonation.

    PubMed

    Rinfray, Corentin; Brasiliense, Vitor; Izzet, Guillaume; Volatron, Florence; Alves, Sandra; Combellas, Catherine; Kanoufi, Frédéric; Proust, Anna

    2016-07-18

    The polyoxomolybdate hybrid TBA3[PMo11O39{Sn(C6H4)C≡C(C6H4)N2}] K(Mo)Sn[N2(+)] was prepared through Sonogashira-type coupling between TBA4[PMo11O39{Sn(C6H4)I}] K(Mo)Sn[I] and an excess of 3,3-diethyl-1-(4-ethynylphenyl)triaz-1-ene bearing a protected diazonium function, followed by its deprotection by the addition of trifluoroacetic acid (TFA). This enlarges the family of organic-inorganic polyoxomolybdate-based hybrids, which has been far less investigated than their related polyoxotungstates. The diazonium function allows for the electrochemical grafting on glassy carbon, and the K(Mo)Sn-modified electrode was further probed by cyclic voltammetry. The PMo11Sn core was found to be highly sensitive to protonation, and five bielectronic proton-coupled electron transfer processes were detected in the presence of an excess of TFA, thus corresponding to the injection of up to 10 electrons in the potential range between 0.15 and -0.45 V/SCE. The gain observed in the thermodynamic potentials is however detrimental to the apparent kinetics of the electron transfer, which drops from 500 s(-1) in the absence of acid to 12 s(-1) in the presence of an excess of TFA. PMID:27351596

  11. Behavior of the Ru-bda water oxidation catalyst covalently anchored on glassy carbon electrodes

    SciTech Connect

    Matheu, Roc; Francàs, Laia; Chernev, Petko; Ertem, Mehmed Z.; Batista, Victor; Haumann, Michael; Sala, Xavier; Llobet, Antoni

    2015-05-07

    Electrochemical reduction of the dizaonium complex, [RuII(bda)(NO)(N–N2)2]3+, 23+ (N–N22+ is 4-(pyridin-4-yl) benzenediazonium and bda2– is [2,2'-bipyridine]-6,6'-dicarboxylate), in acetone produces the covalent grafting of this molecular complex onto glassy carbon (GC) electrodes. Multiple cycling voltammetric experiments on the GC electrode generates hybrid materials labeled as GC-4, with the corresponding Ru-aqua complex anchored on the graphite surface. GC-4 has been characterized at pH = 7.0 by electrochemical techniques and X-ray absorption spectroscopy (XAS) and has been shown to act as an active catalyst for the oxidation of water to dioxygen. This new hybrid material has a lower catalytic performance than its counterpart in homogeneous phase and progressively decomposes to form RuO2 at the electrode surface. The resulting metal oxide attached at the GC electrode surface, GC-RuO2, is a very fast and rugged heterogeneous water oxidation catalyst with TOFis of 300 s–1 and TONs >45000. The observed performance is comparable to the best electrocatalysts reported so far, at neutral pH.

  12. A sensitive DNA biosensor fabricated from gold nanoparticles and graphene oxide on a glassy carbon electrode.

    PubMed

    Hajihosseini, Saeedeh; Nasirizadeh, Navid; Hejazi, Mohammad Saeid; Yaghmaei, Parichereh

    2016-04-01

    A sensitive electrochemical DNA biosensor was developed for Helicobacter pylori (H. pylori) detection using differential pulse voltammetry. Single-stranded DNA probe was immobilized on a graphene oxide/gold nanoparticles modified glassy carbon electrode (GO/AuNPs/GCE). A hybridization reaction was conducted with the target DNA and the immobilized DNA on the electrode surface. Oracet blue (OB) was selected for the first time as a redox indicator for amplifying the electrochemical signal of DNA. Enhanced sensitivity was achieved through combining the excellent electric conductivity of GO/AuNPs and the electroactivity of the OB. The DNA biosensor displayed excellent performance to demonstrate the differences between the voltammetric signals of the OB obtained from different hybridization samples (non-complementary, mismatch and complementary DNAs). The proposed biosensor has a linear range of 60.0-600.0 pM and a detection limit of 27.0 pM for detection of H. pylori. In addition, the biosensor have responded very well in the simulated real sample evaluations, signifying its potential to be used in future clinical detection of the H. pylori bacteria. PMID:26838878

  13. Ultrasensitive DNA sensor based on gold nanoparticles/reduced graphene oxide/glassy carbon electrode.

    PubMed

    Benvidi, Ali; Firouzabadi, Afsaneh Dehghani; Moshtaghiun, Seyed Mohammad; Mazloum-Ardakani, Mohammad; Tezerjani, Marzieh Dehghan

    2015-09-01

    We have designed a simple and novel electrochemical biosensor based on glassy carbon electrode (GCE) for DNA detection. GCE was modified with reduced graphene oxide (RGO) and gold nanoparticles (AuNPs) by the electrochemical method, which is helpful for immobilization of thiolated bioreceptors. The electrode modification processes were characterized by scanning electron microscopy (SEM) and electrochemical methods. Then a single-stranded DNA (ssDNA) probe for BRCA1 5382 insC mutation detection was immobilized on the modified electrode for a specific time. The experimental conditions, such as probe immobilization time and target DNA (complementary DNA) hybridization time and temperature with probe DNA, were optimized using electrochemical methods. The electrochemical response for DNA hybridization and synthesis was measured using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) methods. The calibration graph contains two linear ranges; the first part is in the range of 3.0×10(-20) to 1.0×10(-12)M, and the second segment part is in the range of 1.0×10(-12) to 1.0×10(-7)M. The biosensor showed excellent selectivity for the detection of the complementary sequences from noncomplementary sequences, so it can be used for detection of breast cancer. PMID:25988596

  14. Impact of SO 2 poisoning of platinum nanoparticles modified glassy carbon electrode on oxygen reduction

    NASA Astrophysics Data System (ADS)

    Awad, M. I.; Saleh, M. M.; Ohsaka, T.

    An extraordinary recovery characteristic of Pt-nanoparticles from SO 2 poisoning is introduced in this study. Platinum nanoparticles (nano-Pt) modified glassy carbon electrode (nano-Pt/GC) has been compared with polycrystalline platinum (poly-Pt) electrode towards SO 2 poisoning. Two procedures of recovery of the poisoned electrodes were achieved by cycling the potential in the narrow potential range (NPR, 0-0.8 V vs. Ag/AgCl/KCl (sat.)) and wide potential range (WPR, -0.2 to 1.3 V). The extent of recovery was marked using oxygen reduction reaction (ORR) as a probing reaction. SO 2 poisoning of the electrodes changed the mechanism of the oxygen reduction from the direct reduction to water to the stepwise reduction involving the formation of H 2O 2 as an intermediate, as indicated by the rotating ring-disk voltammetry. Using the WPR recovery procedure, it was found that two potential cycles were enough to recover 100% of the activity of the ORR on the nano-Pt/GC electrode. At the poly-Pt electrode, however, four potential cycles of the WPR caused only 79% in the current recovery, while the peak potential of the ORR was 130 mV negatively shifted as compared with the fresh poly-Pt electrode. Interestingly, the NPR procedure at the nano-Pt/GC electrode was even more efficient in the recovery than the WPR procedure at the poly-Pt electrode.

  15. Polymerization of euphorbia oil in carbon dioxide media

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Boron trifluoride diethyl etherate (BF3•OEt2), Lewis acid, catalyzed ring-opening polymerization of euphorbia oil (EO), a natural epoxy oil, was conducted in carbon dioxide. The resulting polymers (RPEO) were characterized by FTIR, 1H-NMR, 13C-NMR, solid state 13C-NMR spectroscopies, differential sc...

  16. Glassy carbon/multi walled carbon nanotube/cadmium sulphide photoanode for light energy storage in vanadium photoelectrochemical cell

    NASA Astrophysics Data System (ADS)

    Peimanifard, Zahra; Rashid-Nadimi, Sahar

    2015-12-01

    The aim of this study is utilizing the artificial photosynthesis, which is an attractive and challenging theme in the photoelectrocatalytic water splitting, to charge the vanadium redox flow battery (VRFB). In this work multi walled carbon nanotube/cadmium sulphide hybrid is employed as a photoanode material to oxidize VO2+ to VO2+ for charging the positive vanadium redox flow battery's half-cell. Characterization studies are also described using the scanning electron microscopic-energy-dispersive X-ray spectroscopy (SEM-EDS), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and UV-Visible methods. The phtoelectrochemical performance is characterized by cyclic voltammetry and chronoamperometry. Applied bias photon-to-current efficiency (ABPE) is achieved for both two and three-electrode configurations. The glassy carbon/multi walled carbon nanotube/cadmium sulphide yields high maximum ABPE of 2.6% and 2.12% in three and two-electrode setups, respectively. These results provide a useful guideline in designing photoelectrochemical cells for charging the vanadium redox flow batteries by sunlight as a low cost, free and abundant energy source, which does not rely on an external power input.

  17. Glycerol electro-oxidation over glassy-carbon-supported Au nanoparticles: direct influence of the carbon support on the electrode catalytic activity.

    PubMed

    Gomes, Janaina F; Gasparotto, Luiz H S; Tremiliosi-Filho, Germano

    2013-07-01

    Glycerol is at present abundantly co-produced in the biodiesel fabrication and can be used as fuel in Direct Glycerol Fuel Cells (DGFC) for cogeneration of electricity, value-added chemicals and heat. With this motivation, in the present work, we investigated at a fundamental level the oxidation of glycerol over glassy carbon (GC) supported Au nanoparticles in alkaline medium using cyclic voltammetry. By controlling the Au deposition time, we varied the GC supported Au coverage from 0.4% to 30% maintaining a regular particle size distribution with a mean particle size of about 200 nm. An influence of the carbon support on the activity of the GC-supported Au nanoparticles was evidenced. Results from studies on the oxidation of glycerol and ethylene glycol on Au and Pt nanoparticles supported on a glassy carbon, highly ordered pyrolytic graphite and dimensionally stable anode under different pH conditions indicate that the carbon support participates actively in the oxidation of glycerol and other alcohols. We propose that active oxygenated species are gradually formed on the glassy carbon by potential cycling (up to the saturation of the carbon area) and these oxygenated species are additional oxygen suppliers for the oxidation of glycerol residues adsorbed on the Au particles, following a mechanism consisting of the synergism of two active elements: gold and carbon. PMID:23666524

  18. Acetylcholinesterase biosensor for inhibitor measurements based on glassy carbon electrode modified with carbon black and pillar[5]arene.

    PubMed

    Shamagsumova, Rezeda V; Shurpik, Dmitry N; Padnya, Pavel L; Stoikov, Ivan I; Evtugyn, Gennady A

    2015-11-01

    New acetylcholinesterase (AChE) biosensor based on unsubstituted pillar[5]arene (P[5]A) as electron mediator was developed and successfully used for highly sensitive detection of organophosphate and carbamate pesticides. The AChE from electric eel was immobilized by carbodiimide binding on carbon black (CB) placed on glassy carbon electrode. The working potential of 200mV was obtained in chronoamperometric mode with the measurement time of 180 s providing best inter-biosensors precision of the results. The AChE biosensor developed made it possible to detect 1×10(-11)-1×10(-6) M of malaoxon, 1×10(-8)-7×10(-6) M of methyl-paraoxon, 1×10(-10)-2×10(-6) M of carbofuran and 7×10(-9)-1×10(-5) M of aldicarb with 10 min incubation. The limits of detection were 4×10(-12), 5×10(-9), 2×10(-11) and 6×10(-10) M, respectively. The AChE biosensor was tested in the analysis of pesticide residuals in spiked samples of peanut and beetroot. The protecting effect of P[5]A derivative bearing quaternary ammonia groups on malaoxon inhibition was shown. PMID:26452862

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    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 Co3O4 nanoparticles, multiwall carbon nanotubes (MWCNTs) and gelatin. The introduction of MWCNTs and Co3O4 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. Determination of oleuropein using multiwalled carbon nanotube modified glassy carbon electrode by adsorptive stripping square wave voltammetry.

    PubMed

    Cittan, Mustafa; Koçak, Süleyman; Çelik, Ali; Dost, Kenan

    2016-10-01

    A multi-walled carbon nanotube modified glassy carbon electrode was used to prepare an electrochemical sensing platform for the determination of oleuropein. Results showed that, the accumulation of oleuropein on the prepared electrode takes place with the adsorption process. Electrochemical behavior of oleuropein was studied by using cyclic voltammetry. Compared to the bare GCE, the oxidation peak current of oleuropein increased about 340 times at MWCNT/GCE. Voltammetric determination of oleuropein on the surface of prepared electrode was studied using square wave voltammetry where the oxidation peak current of oleuropein was measured as an analytical signal. A calibration curve of oleuropein was performed between 0.01 and 0.70µM and a good linearity was obtained with a correlation coefficient of 0.9984. Detection and quantification limits of the method were obtained as 2.73 and 9.09nM, respectively. In addition, intra-day and inter-day precision studies indicated that the voltammetric method was sufficiently repeatable. Finally, the proposed electrochemical sensor was successfully applied to the determination of oleuropein in an olive leaf extract. Microwave-assisted extraction of oleuropein had good recovery values between 92% and 98%. The results obtained with the proposed electrochemical sensor were compared with liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. PMID:27474292

  1. Glassy carbon electrodes modified by multiwalled carbon nanotubes and poly(neutral red): a comparative study of different brands and application to electrocatalytic ascorbate determination.

    PubMed

    Carvalho, Ricardo C; Gouveia-Caridade, Carla; Brett, Christopher M A

    2010-10-01

    The electrochemical behaviour of glassy carbon electrodes coated with multiwalled carbon nanotubes (MWCNT) from three different sources and with different loadings has been compared, with a view to sensor applications. Additionally, poly(neutral red) (PNR) was electrosynthesised by potential cycling on bare glassy carbon and on MWCNT-modified glassy carbon electrodes, and characterised by cyclic voltammetry and scanning electron microscopy. Well-defined voltammetric responses were observed for hexacyanoferrate (II) oxidation with differences between the MWCNT types as well as from loading. The MWCNT and PNR/MWCNT-modified electrodes were applied to the oxidative determination of ascorbate, the electrocatalytic effects observed varying according to the type of nanotubes. Comparison was made with electrodes surface-modified by graphite powder. All modified electrode configurations with and without PNR were successfully employed for ascorbate oxidation at +0.05 V vs saturated calomel electrode with detection limits down to 4 μM; good operational stability and storage stability were also obtained. PMID:20625885

  2. Comment on " Studies on nanoporous glassy carbon as a new electrochemical capacitor material [Y. Wen, G. Cao, Y. Yang, J. Power Sources 148 (2005) 121-128

    NASA Astrophysics Data System (ADS)

    Braun, Artur

    Gas-phase activated monolithic glassy carbon was used as electrochemical double layer capacitor electrode by a research team of Siemens AG in the early 1980s [1], J. Miklos, K. Mund, W. Naschwitz, Siemens AG, Offenlegungsschrift DE 30 11 701 A1, German Patent (1980). Wen et al. [2] (Y.H. Wen, G.P. Cao, J. Cheng, Y.S. Yang, New Carbon Mater. 18(3) (2003) 219, and [3] Y.H. Wen, G.P. Cao, Y.S. Yang, J. Power Sources 148 (2005) 121, have repeatedly questioned the performance of this glassy carbon based supercapacitor electrode concept. This asks for some comments.

  3. Electrochemical investigation of photosubstitution processes at glassy-carbon electrodes coated with polymer-bound ruthenium complexes

    SciTech Connect

    Haas, O.; Kriens, M.; Vos, J.G.

    1981-03-25

    Glassy-carbon electrodes were coated with (Ru(bpy)/sub 2/Cl(poly(4-vinylpyridine)))Cl. These derivatized electrodes were photolyzed while cyclic voltammograms were recorded. The changes of redox potential observed in the cyclic voltammograms are explained in terms of ligand exchange of the coordinated Cl/sup -/ with H/sub 2/O, ClO/sub 4//sup -/ and CH/sub 3/CN. This opens an easy way to change the redox potential of a fixed ruthenium complex. The demonstrated exchange processes are irreversible. Therefore an information storage, which can be read with suitable electrochemical equipment, is possible.

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

    PubMed Central

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

    2015-01-01

    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. PMID:25621613

  5. A new kinetic-mechanistic approach to elucidate electrooxidation of doxorubicin hydrochloride in unprocessed human fluids using magnetic graphene based nanocomposite modified glassy carbon electrode.

    PubMed

    Soleymani, Jafar; Hasanzadeh, Mohammad; Shadjou, Nasrin; Khoubnasab Jafari, Maryam; Gharamaleki, Jalil Vaez; Yadollahi, Mehdi; Jouyban, Abolghasem

    2016-04-01

    A novel magnetic nanocomposite was synthesized in one step using polymerization of magnetic graph oxide grafted with chlorosulfonic acid (Fe3O4-GO-SO3H) 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/Fe3O4-GO-SO3H/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. PMID:26838892

  6. A novel electrochemical sensor for the analysis of β-agonists: the poly(acid chrome blue K)/graphene oxide-nafion/glassy carbon electrode.

    PubMed

    Lin, Xiaoyun; Ni, Yongnian; Kokot, Serge

    2013-09-15

    A novel modified electrode was constructed by the electro-polymerization of 4,5-dihydroxy-3-[(2-hydroxy-5-sulfophenyl)azo]-2,7-naphthalenedisulfonic acid trisodium salt (acid chrome blue K (ACBK)) at a graphene oxide (GO)-nafion modified glassy carbon electrode (GCE). The characterization of an electrochemically synthesized poly-ACBK/GO-nafion film was investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), atomic force microscopy (AFM) and scanning electron microscopy (SEM) techniques, and the results were interpreted and compared at each stage of the electrode construction. Electrochemical oxidation of eight β-agonists - clenbuterol, salbutamol, terbutaline, ractopamine, dopamine, dobutamine, adrenaline, and isoprenaline, was investigated by CV at the different electrodes. At the poly-ACBK/GO-nafion/GCE, the linear sweep voltammetry peak currents of the eight β-agonists increased linearly with their concentrations in the range of 1.0-36.0 ng mL(-1), respectively, and their corresponding limits of detection (LODs) were within the 0.58-1.46 ng mL(-1) range. This electrode showed satisfactory reproducibility and stability, and was used successfully for the quantitative analysis of clenbuterol in pork samples. PMID:23811373

  7. Voltammetric analysis with the use of a novel electro-polymerised graphene-nafion film modified glassy carbon electrode: simultaneous analysis of noxious nitroaniline isomers.

    PubMed

    Lin, Xiaoyun; Ni, Yongnian; Kokot, Serge

    2012-12-01

    A new modified electrode was constructed by the electro-polymerization of 7-[(2,4-dihydroxy-5-carboxybenzene)azo]-8-hydroxyquinoline-5-sulfonic acid (DHCBAQS) at a graphene-nafion modified glassy carbon electrode (GCE). The construction process was performed stepwise and at each step the electrochemical characteristics were investigated particularly with respect to the oxidation of the three noxious analytes, 2-nitroaniline (2-NA), 3-nitroaniline (3-NA), 4-nitroaniline (4-NA); the electrode treated with the fluorescence reagent DHCBAQS performed best. At this electrode, the differential pulse voltammetry peak currents of the three isomers increased linearly with their concentrations in the range of 0.05-0.60 μg mL(-1), respectively, and their corresponding limits of detection (LODs) were all about 0.022 μg mL(-1). Furthermore, satisfactory results were obtained when this electrode was applied for the simultaneous quantitative analysis of the nitroaniline isomer mixtures by Principal component regression (PCR) and Partial least squares (PLS) as calibration methods (relative prediction error (PRE(T)) - 9.04% and 9.23%) and average recoveries (101.0% and 101.7%), respectively. The above novel poly-DHCBAQS/graphene-nafion/GCE was successfully employed for the simultaneous analysis of the three noxious nitroaniline isomers in water and sewage samples. PMID:23142057

  8. A novel voltammetric sensor for sensitive detection of mercury(II) ions using glassy carbon electrode modified with graphene-based ion imprinted polymer.

    PubMed

    Ghanei-Motlagh, Masoud; Taher, Mohammad Ali; Heydari, Abolfazl; Ghanei-Motlagh, Reza; Gupta, Vinod K

    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(-1). The limit of detection (LOD) was found to be 0.02 μg L(-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. PMID:27040231

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

    PubMed Central

    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

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

    PubMed

    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

  11. Boron doped diamond and glassy carbon electrodes comparative study of the oxidation behaviour of cysteine and methionine.

    PubMed

    Enache, T A; Oliveira-Brett, A M

    2011-04-01

    The electrochemical oxidation behaviour at boron doped diamond and glassy carbon electrodes of the sulphur-containing amino acids cysteine and methionine, using cyclic and differential pulse voltammetry over a wide pH range, was compared. The oxidation reactions of these amino acids are irreversible, diffusion-controlled pH dependent processes, and occur in a complex cascade mechanism. The amino acid cysteine undergoes similar three consecutive oxidation reactions at both electrodes. The first step involves the oxidation of the sulfhydryl group with radical formation, that undergoes nucleophilic attack by water to give an intermediate species that is oxidized in the second step to cysteic acid. The oxidation of the sulfhydryl group leads to a disulfide bridge between two similar cysteine moieties forming cysteine. The subsequent oxidation of cystine occurs at a higher potential, due to the strong disulfide bridge covalent bond. The electro-oxidation of methionine at a glassy carbon electrode occurs in two steps, corresponding to the formation of sulfoxide and sulfone, involving the adsorption and protonation/deprotonation of the thiol group, followed by electrochemical oxidation. Methionine undergoes a one-step oxidation reaction at boron doped diamond electrodes due to the negligible adsorption, and the oxidation also leads to the formation of methionine sulfone. PMID:21377428

  12. Heterogeneous polymerizations in supercritical carbon dioxide continuous phases

    SciTech Connect

    DeSimone, J.M.; Maury, E.E.; Combes, J.R.; Menceloglu, Y.Z.

    1993-12-31

    Heterogeneous emulsion polymerizations are important industrial methods for the synthesis of various polymeric materials. These processes generally use water as the dispersing medium. The authors propose to utilize carbon dioxide as the dispersing medium which would make the polymer recovery easier and would circumvent the contamination of water. In CO{sub 2} - based emulsion process one can have either a hydrophilic dispersed phase (hydrophilic monomer) or a hydrophobic dispersed phase (hydrophobic monomer). The surfactant has to be designed to partition itself at the CO{sub 2} - monomer/polymer interface and the initiator has to be soluble in the dispersing medium. The design of the initiator and graft copolymer surfactants will be presented. One example of a graft copolymer is a copolymer of poly(ethylene oxide) macromonomer synthesized by living anionic polymerization and a fluoroacrylate monomer resulting in a graft copolymer having hydrophilic grafts and a {open_quotes}CO{sub 2}-philic{close_quotes} backbone (due to the fluorine chains). The phase behavior of these surfactants will be discussed at the meeting.

  13. Covalent modification of glassy carbon spheres through ball milling under solvent free conditions: A novel electrochemical interface for mercury(II) quantification.

    PubMed

    Kempegowda, Raghu G; Malingappa, Pandurangappa

    2014-08-01

    A simple and green chemistry protocol has been proposed based on the covalent anchoring of benzamide molecule on glassy carbon spheres through ball milling under solvent free condition. The modification proceeds through the formation of an amide bond between carboxylic group of glassy carbon spheres and the amino group of modifier molecule. The formation of covalent bond was ascertained using X-ray photoelectron spectroscopy. Scanning electron microscopy was used to study the surface morphology of milled glassy carbon spheres. The aqueous colloidal solution of modified glassy carbon spheres was used in the preparation of thin film electrodes and subsequently used as a novel electrochemical interface in the quantification of mercury at trace level using a differential pulse anodic stripping voltammetric technique. The modified electrode showed good sensitivity and selectivity towards mercury with a detection limit of 1nM with least interference from most of the ions. The analytical utility of the proposed electrode has been validated by determining the mercury levels in number of sample matrices. PMID:24881534

  14. Glassy carbon - A promising substrate material for pulsed laser deposition of thin Li 1+ xMn 2O 4- δ electrodes

    NASA Astrophysics Data System (ADS)

    Simmen, F.; Horisberger, M.; Seyfang, B.; Lippert, T.; Novák, P.; Döbeli, M.; Mallepell, M.; Schneider, C. W.; Wokaun, A.

    2011-04-01

    The spinel LiMn 2O 4 is a promising candidate for future battery applications. If used as a positive electrode in a battery, the charging capacity of such a battery element is limited by the formation of a solid electrolyte interphase like layer between the electrolyte and the spinel. To study the electrolyte-electrode interaction during electrochemical cycling, spinel thin films are deposited as model electrodes on glassy carbon substrates by pulsed laser ablation. The obtained polycrystalline oxide thin films show a well defined surface morphology and are electrochemical active. Adhesion of these thin films on glassy carbon is in general poor, but can be improved considerably by a surface pretreatment or adding a thin metallic coating to the substrate prior deposition. The best adhesion is obtained for films deposited on argon plasma pretreated as well as Pt coated glassy carbon substrates. During the electrochemical characterization of Li 1.06Mn 2O 3.8 thin film electrodes, no additional reactions of the substrate are observed independent of the used electrolyte. The best cycle stability is achieved for films on Pt coated glassy carbon substrates.

  15. Plasma polymerized thin coating as a protective layer of carbon nanotubes grafted on carbon fibers

    NASA Astrophysics Data System (ADS)

    Einig, A.; Rumeau, P.; Desrousseaux, S.; Magga, Y.; Bai, J. B.

    2013-04-01

    Nanoparticles addition is widely studied to improve properties of carbon fiber reinforced composites. Here, hybrid carbon fiber results from grafting of carbon nanotubes (CNT) by Chemical Vapor Deposition (CVD) on the carbon fiber for mechanical reinforcement and conductive properties. Both tows and woven fabrics made of the hybrid fibers are added to the matrix for composite processing. However handling hybrid fibers may induce unwilling health risk due to eventual CNT release and a protective layer is required. A thin coating layer is deposited homogeneously by low pressure plasma polymerization of an organic monomer without modifying the morphology and the organization of grafted CNTs. The polymeric layer effect on the electrical behavior of hybrid fiber is assessed by conductivity measurements. Its influence on the mechanical properties is also studied regarding the interface adhesion between fiber and matrix. The protective role of layer is demonstrated by means of friction constraints applied to the hybrid fiber.

  16. Glucose oxidase/colloidal gold nanoparticles immobilized in Nafion film on glassy carbon electrode: Direct electron transfer and electrocatalysis.

    PubMed

    Zhao, Shuang; Zhang, Kai; Bai, Yu; Yang, Weiwei; Sun, Changqing

    2006-10-01

    The direct electron transfer of glucose oxidase (GOD) was achieved based on the immobilization of GOD/colloidal gold nanoparticles on a glassy carbon electrode by a Nafion film. The immobilized GOD displayed a pair of well-defined and nearly reversible redox peaks with a formal potential (Eo ') of -0.434 V in 0.1 M pH 7.0 phosphate buffer solution and the response showed a surface-controlled electrode process. The dependence of Eo ' on solution pH indicated that the direct electron transfer reaction of GOD was a two-electron-transfer coupled with a two-proton-transfer reaction process. The experimental results also demonstrated that the immobilized GOD retained its electrocatalytic activity for the oxidation of glucose. So the resulting modified electrode can be used as a biosensor for detecting glucose. PMID:16556513

  17. Study of the voltammetric behavior of jatrorrhizine and its sensitive determination at electrochemical pretreatment glassy carbon electrode.

    PubMed

    Ye, Zhuo; Li, Yinfeng; Wen, Jianguo; Li, Kunjing; Ye, Baoxian

    2014-08-01

    A simple, inexpensive and highly sensitive electrochemical method for the determination of jatrorrhizine was developed using an electrochemically pretreated glassy carbon electrode (EPGCE). The electrochemical behavior of jatrorrhizine was systematically investigated in detail and some kinetic parameters were calculated for the first time. A reasonable reaction mechanism of jatrorrhizine on the EPGCE was also discussed and proposed, which could be a reference for the pharmacological action of jatrorrhizine in clinical study. And the first electroanalytical method of jatrorrhizine was established with a wide linear range from 7.0×10(-8) to 2.0×10(-5)mol L(-1) and a low detection limit of 5.0×10(-8)mol L(-1). The proposed method was successfully applied in determination of jatrorrhizine in pharmaceutical sample, Tinospora capillipes Gagnep (a traditional Chinese medicine), with satisfactory results. PMID:24881532

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

    PubMed

    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. PMID:26278169

  19. Graphene/Nafion composite film modified glassy carbon electrode for simultaneous determination of paracetamol, aspirin and caffeine in pharmaceutical formulations.

    PubMed

    Yiğit, Aydın; Yardım, Yavuz; Çelebi, Metin; Levent, Abdulkadir; Şentürk, Zühre

    2016-09-01

    A graphene-Nafion composite film was fabricated on the glassy carbon electrode (GR-NF/GCE), and used for simultaneous determination of paracetamol (PAR), aspirin (ASA) and caffeine (CAF). The electrochemical behaviors of PAR, ASA and CAF were investigated by cyclic voltammetry and square-wave adsorptive anodic stripping voltammetry. By using stripping one for simultaneous determination of PAR, ASA and CAF, their electrochemical oxidation peaks appeared at +0.64, 1.04 and 1.44V, and good linear current responses were obtained with the detection limits of 18ngmL(-1) (1.2×10(-9)M), 11.7ngmL(-1) (6.5×10(-8)M) and 7.3ngmL(-1) (3.8×10(-8)M), respectively. Finally, the proposed electrochemical sensor was successfully applied for quantifying PAR, ASA and CAF in commercial tablet formulations. PMID:27343573

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

    NASA Astrophysics Data System (ADS)

    Blacha-Grzechnik, Agata; Piwowar, Katarzyna; Krukiewicz, Katarzyna; Koscielniak, Piotr; Szuber, Jacek; Zak, Jerzy K.

    2016-05-01

    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 1O2 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.

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

    PubMed

    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. PMID:25226918

  2. Tannic acid functionalized N-doped graphene modified glassy carbon electrode for the determination of bisphenol A in food package.

    PubMed

    Jiao, Shoufeng; Jin, Jing; Wang, Lun

    2014-05-01

    A rapid, environmental friendly, and sensitive sensor for the detection of bisphenol A (BPA) was developed at glassy carbon electrode (GCE) modified with Tannic acid functionalized N-doped graphene (TA/N-G) immobilized by Nafion. Compared with other sensors, the proposed sensor greatly enhanced the response signal of BPA due to the active surface area of N-G and high absorption efficiency of TA. Under the optimal conditions, the oxidation current increased linearly with increasing the concentration of BPA in the range of 0.05-13 µM with the detection limit of 4.0 nM. The fabricated electrode showed good reproducibility, stability and anti-interference. The developed electrochemical sensor was successfully applied to determine BPA in food package. PMID:24720975

  3. Novel Signal-Amplified Fenitrothion Electrochemical Assay, Based on Glassy Carbon Electrode Modified with Dispersed Graphene Oxide

    NASA Astrophysics Data System (ADS)

    Wang, Limin; Dong, Jinbo; Wang, Yulong; Cheng, Qi; Yang, Mingming; Cai, Jia; Liu, Fengquan

    2016-03-01

    A novel signal-amplified electrochemical assay for the determination of fenitrothion was developed, based on the redox behaviour of organophosphorus pesticides on a glassy carbon working electrode. The electrode was modified using graphene oxide dispersion. The electrochemical response of fenitrothion at the modified electrode was investigated using cyclic voltammetry, current-time curves, and square-wave voltammetry. Experimental parameters, namely the accumulation conditions, pH value, and volume of dispersed material, were optimised. Under the optimum conditions, a good linear relationship was obtained between the oxidation peak current and the fenitrothion concentration. The linear range was 1–400 ng·mL‑1, with a detection limit of 0.1 ng·mL‑1 (signal-to-nose ratio = 3). The high sensitivity of the sensor was demonstrated by determining fenitrothion in pakchoi samples.

  4. A highly sensitive hydrogen peroxide sensor based on (Ag-Au NPs)/poly[o-phenylenediamine] modified glassy carbon electrode.

    PubMed

    Shamsipur, Mojtaba; Karimi, Ziba; Amouzadeh Tabrizi, Mahmoud

    2015-11-01

    Herein, the poly(o-phenylenediamine) decorated with gold-silver nanoparticle (Ag-Au NPs) nanocomposite modified glassy carbon was used for the determination of hydrogen peroxide. Electrochemical experiments indicated that the proposed sensor possesses an excellent sensitivity toward the reduction of hydrogen peroxide. The resulting sensor exhibited a good response to hydrogen peroxide over linear range from 0.2 to 60.0μM with a limit of detection of 0.08μM, good reproducibility, long-term stability and negligible interference from ascorbic acid, uric acid and dopamine. The proposed sensor was successfully applied to the determination of hydrogen peroxide in human serum sample. PMID:26249610

  5. Interaction of some cardiovascular drugs with bovine serum albumin at physiological conditions using glassy carbon electrode: A new approach.

    PubMed

    Afsharan, Hadi; Hasanzadeh, Mohammad; Shadjou, Nasrin; Jouyban, Abolghasem

    2016-08-01

    In this report, for the first time, the non-modified glassy carbon electrode was used for detection of cardiovascular drug interaction with bovine serum albumin (BSA). These interactions were tested at physiological conditions (T=37°C and pH=7.4 phosphate buffer solution) in different incubation times (0-4h) by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV). The applications of DPV for quantitative investigation of some cardiovascular drug interaction with BSA (as a model of serum albumin proteins) were discussed. The herein described approach is expected to promote the exploitation of electrochemically-based methods for the study of drug-serum albumin protein interaction which is necessary in biochemical and biosensing studies. This report may open a new window to application of electrochemical sensors towards interactions of cardiovascular drugs with BSA and human serum albumin (HAS) in the near future. PMID:27157732

  6. Novel Signal-Amplified Fenitrothion Electrochemical Assay, Based on Glassy Carbon Electrode Modified with Dispersed Graphene Oxide

    PubMed Central

    Wang, Limin; Dong, Jinbo; Wang, Yulong; Cheng, Qi; Yang, Mingming; Cai, Jia; Liu, Fengquan

    2016-01-01

    A novel signal-amplified electrochemical assay for the determination of fenitrothion was developed, based on the redox behaviour of organophosphorus pesticides on a glassy carbon working electrode. The electrode was modified using graphene oxide dispersion. The electrochemical response of fenitrothion at the modified electrode was investigated using cyclic voltammetry, current-time curves, and square-wave voltammetry. Experimental parameters, namely the accumulation conditions, pH value, and volume of dispersed material, were optimised. Under the optimum conditions, a good linear relationship was obtained between the oxidation peak current and the fenitrothion concentration. The linear range was 1–400 ng·mL−1, with a detection limit of 0.1 ng·mL−1 (signal-to-nose ratio = 3). The high sensitivity of the sensor was demonstrated by determining fenitrothion in pakchoi samples. PMID:27003798

  7. Enhancement of electrogenerated chemiluminescence of luminol by ascorbic acid at gold nanoparticle/graphene modified glassy carbon electrode.

    PubMed

    Dong, Yongping; Gao, Tingting; Zhou, Ying; Chu, Xiangfeng; Wang, Chengming

    2015-01-01

    Gold nanoparticle/graphene (GNP/GR) nanocomposite was one-pot synthesized from water soluble graphene and HAuCl₄ by hydrothermal method and characterized by TEM, Raman spectroscopy, XRD, XPS, UV-vis spectroscopy, and electrochemical impedance spectroscopy (EIS). Electrogenerated chemiluminescence (ECL) of luminol was investigated at the GNP/GR modified glassy carbon electrode (GNP/GR/GCE) and the GNP modified glassy carbon electrode (GNP/GCE) in aqueous solution respectively. The results revealed that one strong anodic ECL peak could be observed at ∼0.8 V at two modified electrodes compared with that at the bare electrode. The intensity of the anodic ECL at the GNP/GR/GCE is weaker than that at the GNP/GCE, which should be due to the synergic effect of the enhancing effect of gold nanoparticles and the inhibiting effect of graphene on anodic luminol ECL. One strong cathodic ECL peak located at ∼-0.8 V could be observed at the GNP/GR/GCE but not at the GNP/GCE, which should be result from the adsorbed oxygen at the graphene film. In the presence of ascorbic acid, the anodic ECL at the GNP/GR/GCE was enhanced more than 8-times, which is more apparent than that at the GNP/GCE. Whereas, the cathodic ECL peak was seriously inhibited at the GNP/GR/GCE. The enhanced ECL intensity at the GNP/GR/GCE varied linearly with the logarithm of ascorbic acid concentration in the range of 1.0 × 10(-8) to 1.0 × 10(-6)mol L(-1) with a detection limit of 1.0 × 10(-9) mol L(-1). The possible ECL mechanism was also discussed. PMID:25022493

  8. Enhancement of electrogenerated chemiluminescence of luminol by ascorbic acid at gold nanoparticle/graphene modified glassy carbon electrode

    NASA Astrophysics Data System (ADS)

    Dong, Yongping; Gao, Tingting; Zhou, Ying; Chu, Xiangfeng; Wang, Chengming

    2015-01-01

    Gold nanoparticle/graphene (GNP/GR) nanocomposite was one-pot synthesized from water soluble graphene and HAuCl4 by hydrothermal method and characterized by TEM, Raman spectroscopy, XRD, XPS, UV-vis spectroscopy, and electrochemical impedance spectroscopy (EIS). Electrogenerated chemiluminescence (ECL) of luminol was investigated at the GNP/GR modified glassy carbon electrode (GNP/GR/GCE) and the GNP modified glassy carbon electrode (GNP/GCE) in aqueous solution respectively. The results revealed that one strong anodic ECL peak could be observed at ∼0.8 V at two modified electrodes compared with that at the bare electrode. The intensity of the anodic ECL at the GNP/GR/GCE is weaker than that at the GNP/GCE, which should be due to the synergic effect of the enhancing effect of gold nanoparticles and the inhibiting effect of graphene on anodic luminol ECL. One strong cathodic ECL peak located at ∼-0.8 V could be observed at the GNP/GR/GCE but not at the GNP/GCE, which should be result from the adsorbed oxygen at the graphene film. In the presence of ascorbic acid, the anodic ECL at the GNP/GR/GCE was enhanced more than 8-times, which is more apparent than that at the GNP/GCE. Whereas, the cathodic ECL peak was seriously inhibited at the GNP/GR/GCE. The enhanced ECL intensity at the GNP/GR/GCE varied linearly with the logarithm of ascorbic acid concentration in the range of 1.0 × 10-8 to 1.0 × 10-6 mol L-1 with a detection limit of 1.0 × 10-9 mol L-1. The possible ECL mechanism was also discussed.

  9. Prussian blue modified glassy carbon electrodes-study on operational stability and its application as a sucrose biosensor.

    PubMed

    Haghighi, B; Varma, S; Alizadeh Sh, F M; Yigzaw, Y; Gorton, L

    2004-09-01

    Stabilisation of electrochemically deposited Prussian blue (PB) films on glassy carbon (GC) electrodes has been investigated and an enhancement in the stability of the PB films is reported if the electrodes are treated with tetrabutylammonium toluene-4-sulfonate (TTS) in the electrochemical activation step following the electrodeposition. A multi-enzyme PB based biosensor for sucrose detection was made in order to demonstrate that PB films can be coupled with an oxidase system. A tri-enzyme system, comprising glucose oxidase, mutarotase and invertase, was crosslinked with glutaraldehyde and bovine albumin serum on the PB modified glassy carbon electrode. The deposited PB operated as an electrocatalyst for electrochemical reduction of hydrogen peroxide, the final product of the enzyme reaction sequence. The electrochemical response was studied using flow injection analysis for the determination of sucrose, glucose and H(2)O(2). The optimal concentrations of the immobilisation mixture was standardised as 8U of glucose oxidase, 8U of mutarotase, 16U of invertase, 0.5% glutaraldehyde (0.025mul) and 0.5% BSA (0.025mg) in a final volume of 5mul applied at the electrode surface (0.066cm(2)). The biosensor exhibited a linear response for sucrose (4-800muM), glucose (2-800muM) and H(2)O(2) (1-800muM) and the detection limit was 4.5, 1.5 and 0.5muM for sucrose, glucose and H(2)O(2), respectively. The sample throughput was ca. 60 samples h(-1). An increase in the operational and storage stability of the sucrose biosensor was also noted when the PB modified electrodes were conditioned in phosphate buffer containing 0.05M TTS during the preparation of the PB films. PMID:18969561

  10. Determination of mutagenic amines in water and food samples by high pressure liquid chromatography with amperometric detection using a multiwall carbon nanotubes-glassy carbon electrode.

    PubMed

    Bueno, Ana María; Marín, Miguel Ángel; Contento, Ana María; Ríos, Ángel

    2016-02-01

    A chromatographic method, using amperometric detection, for the sensitive determination of six representative mutagenic amines was developed. A glassy carbon electrode (GCE), modified with multiwall carbon nanotubes (GCE-CNTs), was prepared and its response compared to a conventional glassy carbon electrode. The chromatographic method (HPLC-GCE-CNTs) allowed the separation and the determination of heterocyclic aromatic amines (HAAs) classified as mutagenic amines by the International Agency for Research of Cancer. The new electrode was systematically studied in terms of stability, sensitivity, and reproducibility. Statistical analysis of the obtained data demonstrated that the modified electrode provided better sensitivity than the conventional unmodified ones. Detection limits were in the 3.0 and 7.5 ng/mL range, whereas quantification limits ranged between 9.5 and 25.0 ng/mL were obtained. The applicability of the method was demonstrated by the determination of the amines in several types of samples (water and food samples). Recoveries indicate very good agreement between amounts added and those found for all HAAs (recoveries in the 92% and 105% range). PMID:26304357

  11. Carbon nanotubes as templates for polymerized lipid assemblies

    NASA Astrophysics Data System (ADS)

    Thauvin, Cédric; Rickling, Stéphane; Schultz, Patrick; Célia, Hervé; Meunier, Stéphane; Mioskowski, Charles

    2008-12-01

    Amphiphilic molecules-molecules that have both hydrophobic and hydrophilic properties-can self-assemble in water to form diverse structures such as micelles, vesicles and tubes, and these nanostructures can be used for delivering drugs, stabilizing membrane proteins or as nanoreactors. We have previously shown that lipids can self-organize on the surface of single-walled carbon nanotubes into regular ring-shaped assemblies. Here we show that these lipid assemblies can be polymerized and isolated from the nanotube template by application of an electric field. We also demonstrate that these assemblies are monodispersed, water-soluble, and can dissolve various hydrophobic rylene dyes, fullerenes and membrane proteins. The stability of these constructs and their diverse applications will be useful in the fields of cosmetics, medicine and material sciences.

  12. Biosensor based on tyrosinase immobilized on a single-walled carbon nanotube-modified glassy carbon electrode for detection of epinephrine

    PubMed Central

    Apetrei, Irina Mirela; Apetrei, Constantin

    2013-01-01

    A biosensor comprising tyrosinase immobilized on a single-walled carbon nanotube-modified glassy carbon electrode has been developed. The sensitive element, ie, tyrosinase, was immobilized using a drop-and-dry method followed by cross-linking. Tyrosinase maintained high bioactivity on this nanomaterial, catalyzing the oxidation of epinephrine to epinephrine-quinone, which was electrochemically reduced (−0.07 V versus Ag/AgCl) on the biosensor surface. Under optimum conditions, the biosensor showed a linear response in the range of 10–110 μM. The limit of detection was calculated to be 2.54 μM with a correlation coefficient of 0.977. The repeatability, expressed as the relative standard deviation for five consecutive determinations of 10−5 M epinephrine solution was 3.4%. A good correlation was obtained between results obtained by the biosensor and those obtained by ultraviolet spectrophotometric methods. PMID:24348034

  13. In-Vivo Characterization of Glassy Carbon Micro-Electrode Arrays for Neural Applications and Histological Analysis of the Brain Tissue

    NASA Astrophysics Data System (ADS)

    Vomero, Maria

    The aim of this work is to fabricate and characterize glassy carbon Microelectrode Arrays (MEAs) for sensing and stimulating neural activity, and conduct histological analysis of the brain tissue after the implant to determine long-term performance. Neural applications often require robust electrical and electrochemical response over a long period of time, and for those applications we propose to replace the commonly used noble metals like platinum, gold and iridium with glassy carbon. We submit that such material has the potential to improve the performances of traditional neural prostheses, thanks to better charge transfer capabilities and higher electrochemical stability. Great interest and attention is given in this work, in particular, to the investigation of tissue response after several weeks of implants in rodents' brain motor cortex and the associated materials degradation. As part of this work, a new set of devices for Electrocorticography (ECoG) has been designed and fabricated to improve durability and quality of the previous generation of devices, designed and manufactured by the same research group in 2014. In-vivo long-term impedance measurements and brain activity recordings were performed to test the functionality of the neural devices. In-vitro electrical characterization of the carbon electrodes, as well as the study of the adhesion mechanisms between glassy carbon and different substrates is also part of the research described in this book.

  14. Electrochemical and spectroelectrochemical behavior of the TCNQ(0/)(-) couple on a glassy carbon electrode. Layer-by-layer nucleation and growth.

    PubMed

    Gómez, L; Rodríguez-Amaro, R

    2006-08-15

    On the basis of the electrochemical results obtained for thin films of 7,7,8,8- tetracyanoquinodimethane (TCNQ) on a glassy carbon electrode, the reduction and oxidation of the [TCNQ](0/)(-) couple in KCl aqueous media occurs via a mechanism involving layer-by-layer nucleation and growth. In situ recorded UV-visible spectroelectrochemical data allow two different crystal structures for the oxidized form of TCNQ to be discriminated. PMID:16893249

  15. Thermal plasma process for recovering monomers and high value carbons from polymeric materials

    DOEpatents

    Knight, Richard; Grossmann, Elihu D.; Guddeti, Ravikishan R.

    2002-01-01

    The present invention relates to a method of recycling polymeric waste products into monomers and high value forms of carbon by pyrolytic conversion using an induction coupled RF plasma heated reactor.

  16. Periodic structure formation and surface morphology evolution of glassy carbon surfaces applying 35-fs-200-ps laser pulses

    NASA Astrophysics Data System (ADS)

    Csontos, J.; Toth, Z.; Pápa, Z.; Budai, J.; Kiss, B.; Börzsönyi, A.; Füle, M.

    2016-06-01

    In this work laser-induced periodic structures with lateral dimensions smaller than the central wavelength of the laser were studied on glassy carbon as a function of laser pulse duration. To generate diverse pulse durations titanium-sapphire (Ti:S) laser (center wavelength 800 nm, pulse durations: 35 fs-200 ps) and a dye-KrF excimer laser system (248 nm, pulse durations: 280 fs, 2.1 ps) were used. In the case of Ti:S laser treatment comparing the central part of the laser-treated areas a striking difference is observed between the femtoseconds and picoseconds treatments. Ripple structure generated with short pulse durations can be characterized with periodic length significantly smaller than the laser wavelength (between 120 and 165 nm). At higher pulse durations the structure has a higher periodic length (between 780 and 800 nm), which is comparable to the wavelength. In case of the excimer laser treatment the different pulse durations produced similar surface structures with different periodic length and different orientation. One of the structures was parallel with the polarization of the laser light and has a higher periodic length (~335 nm), and the other was perpendicular with smaller periodic length (~78-80 nm). The possible mechanisms of structure formation will be outlined and discussed in the frame of our experimental results.

  17. A simple electrochemical platform for detection of nitrobenzene in water samples using an alumina polished glassy carbon electrode.

    PubMed

    Thirumalraj, Balamurugan; Palanisamy, Selvakumar; Chen, Shen-Ming; Thangavelu, Kokulnathan; Periakaruppan, Prakash; Liu, Xiao-Heng

    2016-08-01

    In this work, we report a selective electrochemical sensing of nitrobenzene (NB) using an alumina (γ-Al2O3) polished glassy carbon electrode (GCE) for the first time. The scanning electron microscopy studies confirm the presence of alumina particles on the GCE surface. X-ray photoelectron spectroscopy studies reveal that the utilized alumina is γ-Al2O3. The alumina polished GCE shows an enhanced sensitivity and lower overpotential toward the reduction of NB compared to unpolished GCE. The differential pulse voltammetry response was used for the determination of NB and it shows that the reduction peak current of NB is linearly proportional to the concentrations of NB ranging from 0.5 to 145.5μM. The limit of detection is found to be 0.15μM based on 3σ. The fabricated electrode exhibits its appropriate selectivity towards NB in the presence of a range of nitro compounds and metal ions. The good practicality of the sensor in various water samples reveals that it can be a promising electrode material for practical applications. In addition, the proposed NB sensor is simple and cost effective one when compared with previously reported NB sensors in the literature. PMID:27163842

  18. Electrochemical sensor for Isoniazid based on the glassy carbon electrode modified with reduced graphene oxide-Au nanomaterials.

    PubMed

    Guo, Zhuo; Wang, Ze-Yu; Wang, Hui-Hua; Huang, Guo-Qing; Li, Meng-Meng

    2015-12-01

    A sensitive electrochemical sensor has been fabricated to detect Isoniazid (INZ) using reduced graphene oxide (RGO) and Au nanocomposites (RGO-Au). RGO-Au nanocomposites were synthesized by a solution-based approach of chemical co-reduction of Au(III) and graphene oxide (GO), and were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and Fourier transform infrared (FT-IR). The Au nanoparticles separate the RGO sheets in the precipitate and prevent RGO sheets from aggregation upon π-π stacking interactions. RGO-Au nanocomposites were used to modify the glassy carbon electrode (GCE). The electrochemical properties of RGO-Au/GCE were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), and the RGO-Au/GCE exhibited remarkably strong electrocatalytic activities towards INZ. Under the optimized conditions, there was linear relationships between the peak currents and the concentrations in the range of 1.0×10(-7)M to 1.0×10(-3)M for INZ, with the limit of detection (LOD) (based on S/N=3) of 1.0×10(-8)M for INZ. PMID:26354255

  19. Non-enzymatic detection of glucose using poly(azure A)-nickel modified glassy carbon electrode.

    PubMed

    Liu, Tong; Luo, Yiqun; Zhu, Jiaming; Kong, Liyan; Wang, Wen; Tan, Liang

    2016-08-15

    A simple, sensitive and selective non-enzymatic glucose sensor was constructed in this paper. The poly(azure A)-nickel modified glassy carbon electrode was successfully fabricated by the electropolymerization of azure A and the adsorption of Ni(2+). The Ni modified electrode, which was characterized by scanning electron microscope, cyclic voltammetry, electrochemical impedance spectra and X-ray photoelectron spectroscopy measurements, respectively, displayed well-defined current responses of the Ni(III)/Ni(II) couple and showed a good activity for electrocatalytic oxidation of glucose in alkaline medium. Under the optimized conditions, the developed sensor exhibited a broad linear calibration range of 5 μM-12mM for quantification of glucose and a low detection limit of 0.64μM (3σ). The excellent analytical performance including simple structure, fast response time, good anti-interference ability, satisfying stability and reliable reproducibility were also found from the proposed amperometric sensor. The results were satisfactory for the determination of glucose in human serum samples as comparison to those from a local hospital. PMID:27260445

  20. Square wave voltammetric detection by direct electroreduction of paranitrophenol (PNP) using an organosmectite film-modified glassy carbon electrode.

    PubMed

    Ngassa, Guy B P; Tonlé, Ignas K; Ngameni, Emmanuel

    2016-01-15

    This work describes the development of a low-cost and reliable adsorptive stripping voltammetric method for the detection of PNP in water. Organoclays were prepared by intercalation in various loading amounts of cetyltrimethylammonium ions (CTA(+)) in the interlayer space of a smectite-type clay mineral. Their structural characterization was achieved using several techniques including X-ray diffraction (XRD), N2 adsorption-desorption (BET method) and Fourier Transform Infrared spectroscopy (FTIR) that confirmed the intercalation process and the presence of the surfactant ions within the clay mineral layers. Using [Fe(CN)6](3-) and [Ru(NH3)6](3+) as redox probes, the surface charge and the permeability of the starting clay mineral and its modified counterparts were assessed by multisweep cyclic voltammetry, when these materials were coated on the surface of a glassy carbon electrode (GCE). In comparison with the bare GCE, the organoclay modified electrodes exhibited more sensitive response towards the reduction of paranitrophenol (PNP). Under optimized conditions, a calibration curve was obtained in the concentration range from 0.2 to 5.2µmolL(-1); leading to a detection limit of 3.75×10(-8)molL(-1) (S/N=3). After the study of some interfering species on the electrochemical response of PNP, the developed sensor was successfully applied to the electroanalytical quantification of the same pollutant in spring water. PMID:26592645

  1. Simultaneous determination of ethionamide and pyrazinamide using poly(l-cysteine) film-modified glassy carbon electrode.

    PubMed

    Ferraz, Bruno Regis Lyrio; Leite, Fernando Roberto Figueiredo; Malagutti, Andréa Renata

    2016-07-01

    A selective, simple and rapid square wave voltammetry method, based on electropolymerization of l-cysteine (poly(l-Cys)) on a glassy carbon electrode (GCE), was developed in this study for simultaneous determination of ethionamide and pyrazinamide. Electroanalytical and electrochemical properties of the poly(l-Cys)/GCE were investigated by cyclic voltammetry (CV), square wave voltammetry (SWV), electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM). The cyclic voltammetry studies revealed an remarkable electrocatalytic activity of poly(l-Cys)/GCE on ethionamide and pyrazinamide at pH 1.0. The best potential separation between the reduction peaks of the drugs in a mixed solution was found to be 0.14V. It was also found that pyrazinamide exhibits a reversible wave with Epc and Epa at -404mV and -347mV (versus EAg/AgCl), respectively, while ethionamide presents an irreversible reduction peak at Epc=-536mV. The optimized calibration curves for simultaneous determination of ethionamide and pyrazinamide exhibited good and high linear responses within the concentration range 2.38-248.0µmolL(-1) and 0.476-51.2µmolL(-1), respectively. The limit of detection was found to be 0.531µmolL(-1) for ethionamide and 0.113µmolL(-1) for pyrazinamide. The poly(l-Cys)/GCE-based square wave voltammetry method was successfully used to determine ethionamide and pyrazinamide in human urine and blood serum. PMID:27154666

  2. Electrochemically Modulated Separation, Concentration, and Detection of Plutonium Using an Anodized Glassy Carbon Electrode and Inductively Coupled Plasma Mass Spectrometry

    SciTech Connect

    Clark, William J.; Park, Sea H.; Bostick, Debra A.; Duckworth, Doug C.; Van Berkel, Gary J.

    2006-12-15

    Plutonium is shown to be retained on anodized glassy carbon (GC) electrodes at potentials positive of +0.7 V (vs. Ag/AgCl reference) and released upon potential shifts to values negative of +0.3 V. This phenomenon has been exploited for the separation, concentration, and detection of plutonium by the coupling an electrochemical flow cell online with an ICP-MS system. The electrochemically-controlled deposition and analysis of Pu improves detection limits by analyte preconcentration and by matrix and isobaric ion elimination. Information related to the parametric optimization of the technique and hypotheses regarding the mechanism of electrochemical accumulation of Pu are reported. The most likely accumulation scenario involves complexation of Pu (IV) species, produced under a controlled potential, with anions retained in the anodization film that develops during the activation of the GC electrode. The release mechanism is believed to result from the reduction of Pu(IV) in the anion complex to Pu (III), which has a lower tendency to form complexes.

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    A novel folic acid biosensor has been fabricated using Cu doped SnO2 nanoparticles (NPs) synthesized by a simple microwave irradiation method. Powder XRD and TEM studies confirmed that both the pure and Cu doped SnO2 (Cu: 0, 10, 20wt%) crystallized in tetragonal rutile-type structure with spherical morphology. The average crystallite size of pure SnO2 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 SnO2 respectively. XPS studies confirmed the electronic state of Sn and Cu to be 4+ and 2+ respectively. Cu (20wt%) doped SnO2 NPs are proved to be a good sensing element for the determination of folic acid (FA). Cu-SnO2 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.

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

    PubMed

    Mutyala, Sankararao; Mathiyarasu, Jayaraman

    2016-12-01

    Herein, we report a simple, facile and reproducible non-enzymatic hydrogen peroxide (H2O2) 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 H2O2. Amperometric study using ERGO/GCE showed high sensitivity (0.3μA/μM) and faster response upon the addition of H2O2 at an applied potential of -0.25V vs. Ag/AgCl. The detection limit is assessed to be 0.7μM (S/N=3) and the time to reach a stable study state current is <3s for a linear range of H2O2 concentration (1-16μM). In addition, the modified electrode exhibited good reproducibility and long-term stability. PMID:27612728

  5. Morphology-dependent NiO modified glassy carbon electrode surface for lead(II) and cadmium(II) detection

    NASA Astrophysics Data System (ADS)

    Li, Xuewu; Wen, Hao; Fu, Qiang; Peng, Dai; Yu, Jingui; Zhang, Qiaoxin; Huang, Xingjiu

    2016-02-01

    Glassy carbon electrode (GCE) surfaces have been modified with different NiO morphologies consisting of rods NiO, flakes NiO and balls NiO prepared via the hydrothermal synthesis method for Pb(II) and Cd(II) detection by using the square wave anodic stripping voltammetry (SWASV). Meanwhile, the typical cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), BET surface area and adsorption property of the modified electrode surfaces have been investigated to evaluate their electrochemical detection effect. Results show that balls NiO modified GCE can get the optimal detection ability for its highest detection sensitivity to Pb(II) (13.46 A M-1) and Cd(II) (5.10 A M-1), the lowest detection limit (DL) to Pb(II) (0.08 μM) and Cd(II) (0.07 μM) as well as the superior linear relativity. In addition, an enhanced current at redox peaks, lower electron transfer resistance, larger BET surface area and stronger adsorption capacity have been confirmed for the balls NiO modified GCE surface. Finally, excellent stability and reproducibility of balls NiO modified electrodes for Pb(II) and Cd(II) detection have also been proved via the SWASV responses.

  6. Highly sensitive nonenzymatic glucose sensor based on nickel nanoparticle-attapulgite-reduced graphene oxide-modified glassy carbon electrode.

    PubMed

    Shen, Zongxu; Gao, Wenyu; Li, Pei; Wang, Xiaofang; Zheng, Qing; Wu, Hao; Ma, Yuehui; Guan, Weijun; Wu, Songmei; Yu, Yu; Ding, Kejian

    2016-10-01

    In this article, a fast and sensitive nonenzymatic glucose sensor is reported utilizing a glassy carbon electrode modified by synthesizing nanocomposites of nickel nanoparticle-attapulgite-reduced graphene oxide (Ni NPs/ATP/RGO). A facile one-step electrochemical co-deposition approach is adopted to synthesize Ni NPs-ATP-RGO nanocomposites via electrochemical reduction of mixed precursor solution containing graphene oxide (GO), attapulgite (ATP) and nickel cations (Ni(2+)) at the cathode potentials. This strategy results in simultaneous depositions of ATP, cathodic reduction of Ni(2+) into nickel nanoparticles under acidic conditions, and in situ reduction of GO. The as-prepared NiNPs/ATP/RGO-based glucose sensor exhibits outstanding performance for enzymeless glucose sensing with sensitivity (1414.4 μAmM(-1)cm(-2)), linear range (1-710μM) and detection limit (0.37μM). What is more, the sensor has excellent stability and selectivity against common interferences in real sample. PMID:27474298

  7. Potential of glassy carbon and silicon carbide photonic structures as electromagnetic radiation shields for atmospheric re-entry.

    PubMed

    Komarevskiy, Nikolay; Shklover, Valery; Braginsky, Leonid; Hafner, Christian; Lawson, John

    2012-06-18

    During high-velocity atmospheric entries, space vehicles can be exposed to strong electromagnetic radiation from ionized gas in the shock layer. Glassy carbon (GC) and silicon carbide (SiC) are candidate thermal protection materials due to their high melting point and also their good thermal and mechanical properties. Based on data from shock tube experiments, a significant fraction of radiation at hypersonic entry conditions is in the frequency range from 215 to 415 THz. We propose and analyze SiC and GC photonic structures to increase the reflection of radiation in that range. For this purpose, we performed numerical optimizations of various structures using an evolutionary strategy. Among the considered structures are layered, porous, woodpile, inverse opal and guided-mode resonance structures. In order to estimate the impact of fabrication inaccuracies, the sensitivity of the reflectivity to structural imperfections is analyzed. We estimate that the reflectivity of GC photonic structures is limited to 38% in the aforementioned range, due to material absorption. However, GC material can be effective for photonic reflection of individual, strong spectral line. SiC on the other hand can be used to design a good reflector for the entire frequency range. PMID:22714482

  8. Electrochemically modulated separation, concentration, and detection of plutonium using an anodized glassy carbon electrode and inductively coupled plasma mass spectrometry.

    PubMed

    Clark, William J; Park, Sea H; Bostick, Debra A; Duckworth, Douglas C; Van Berkel, Gary J

    2006-12-15

    Plutonium is shown to be retained on anodized glassy carbon (GC) electrodes at potentials positive of +0.7 V (vs Ag/AgCl reference) and released upon potential shifts to values negative of +0.3 V. This phenomenon has been exploited for the separation, concentration, and detection of plutonium by the coupling an electrochemical flow cell on-line with an ICPMS system. The electrochemically controlled deposition and analysis of Pu improves detection limits by analyte preconcentration and by matrix and isobaric ion elimination. Information related to the parametric optimization of the technique and hypotheses regarding the mechanism of electrochemical accumulation of Pu are reported. The most likely accumulation scenario involves complexation of Pu(IV) species, produced under a controlled potential, with anions retained in the anodization film that develops during the activation of the GC electrode. The release mechanism is believed to result from the reduction of Pu(IV) in the anion complex to Pu(III), which has a lower tendency to form complexes. PMID:17165850

  9. Potential of Glassy Carbon and Silicon Carbide Photonic Structures as Electromagnetic Radiation Shields for Atmospheric Re-entry

    NASA Technical Reports Server (NTRS)

    Komarevskiy,Nikolay; Shklover, Valery; Braginsky, Leonid; Hafner, Christian; Lawson, John W.

    2012-01-01

    During high-velocity atmospheric entries, space vehicles can be exposed to strong electromagnetic radiation from ionized gas in the shock layer. Glassy carbon (GC) and silicon carbide (SiC) are candidate thermal protection materials due to their high melting point and also their good thermal and mechanical properties. Based on data from shock tube experiments, a significant fraction of radiation at hypersonic entry conditions is in the frequency range from 215 to 415 THz. We propose and analyze SiC and GC photonic structures to increase the reflection of radiation in that range. For this purpose, we performed numerical optimizations of various structures using an evolutionary strategy. Among the considered structures are layered, porous, woodpile, inverse opal and guided-mode resonance structures. In order to estimate the impact of fabrication inaccuracies, the sensitivity of the reflectivity to structural imperfections is analyzed. We estimate that the reflectivity of GC photonic structures is limited to 38% in the aforementioned range, due to material absorption. However, GC material can be effective for photonic reflection of individual, strong spectral line. SiC on the other hand can be used to design a good reflector for the entire frequency range.

  10. Preparation of novel mercury-doped silver nanoparticles film glassy carbon electrode and its application for electrochemical biosensor.

    PubMed

    Li, Mao-Guo; Shang, Yong-Jia; Gao, Ying-Chun; Wang, Guang-Feng; Fang, Bin

    2005-06-01

    A novel mercury-doped silver nanoparticles film glassy carbon (Ag/MFGC) electrode was prepared in this study. Electrochemical behaviors of cysteine on the Ag/MFGC electrode were investigated by electrochemical impedance spectroscopy and cyclic voltammetry (CV). The results indicated that cysteine could be strongly adsorbed on the surface of the Ag/MFGC electrode to form a thin layer. The doped electrode could catalyze the electrode reaction process of cysteine, and the cysteine displayed a pair of well-defined and nearly reversible CV peaks at the electrode in an acetate buffer solution (pH 5.0). The Ag/MFGC electrode was used for determination of cysteine by differential pulse voltammetry. The linear range was between 4.0x10(-7) and 1.3x10(-5) mol/L, with a detection limit of 1.0x10(-7) mol/L and a signal-to-noise ratio of 3. The relative standard deviation was 2.4% for seven successive determinations of 1.0x10(-5) mol/L cysteine. The determinations of cysteine in synthetic samples and urinal samples were carried out and satisfactory results were obtained. Amperometric application of the Ag/MFGC electrode as biosensors is proposed. PMID:15866527

  11. Amperometric detection of Sudan I in red chili powder samples using Ag nanoparticles decorated graphene oxide modified glassy carbon electrode.

    PubMed

    Prabakaran, E; Pandian, K

    2015-01-01

    A simple and sensitive electrochemical method was developed to determine the concentration of Sudan I in chili powder based on silver nanoparticles decorated graphene oxide modified glassy carbon electrode (AgNPs@GO/GCE). The voltammetry behaviour of Sudan I on modified GCE was investigated in phosphate buffer medium (PBS) with various pH ranges and the electron transfer properties were studied. It is found that the AgNPs@GO/GCE can catalyse the reduction of azo group, -N=N- followed by electrochemical oxidation of (-)OH group present in Sudan I dye molecule. Quantitative detection of Sudan I present in food products was carried out by amperometry method in which reduction potential was fixed at -0.77 V vs. Ag/AgCl. The amperometry method showed an excellent performance with a sensitivity of 6.83 μA mM(-1) and a detection limit of 11.4 × 10(-7)ML(-1). A linear calibration graph was constructed in the ranging 3.90 × 10(-6) to 3.19 × 10(-5)ML(-1). The method was successfully applied for the determination of Sudan I in red chili powder samples. PMID:25053046

  12. Fabrication of alpha-Fe2O3 nanopowder modified glassy carbon electrode for applications in electrochemical sensing.

    PubMed

    Goyal, Rajendra N; Pandey, Ashish K; Kaur, Davinder; Kumar, Ashvani

    2009-08-01

    In the present study, Fe2O3 nanopowder has been grown by Ultrasonic mist chemical vapor deposition (UM-CVD), which is a promising method for large area deposition at low temperatures taking in to account of its simplicity, inexpensiveness and safety. Room temperature XRD results revealed prominent hematite phase with intense (104) reflection and was also in agreement with the HR-TEM results. In situ high temperature X-ray diffraction (XRD) studies clearly indicated the change of phase from hematite to magnetite as the temperature increases above 300 degrees C. The surface morphology and particle size distribution of Fe2O3 nanopowder were characterized using field emission scanning electron microscope (FE-SEM) and high resolution transmission electron microscope (HR-TEM), which revealed that the particles were spherical in nature and distributed in range of 50-100 nm. SQUID magnetometry results indicate the ferromagnetic nature of the nanopowder with crystallite size of 6 nm as calculated from M-H curve. Transmittance of approximately 55% and estimated direct band gap of 2.5 eV was observed. Further, the nanopowder was used to modify glassy carbon electrode (GCE) and the modified electrode was found to exhibit electrocatalytic activity for the oxidation of dopamine. It is expected that the nanopowder will exhibit promising applications in the development of sensors. PMID:19928136

  13. A study on focused ion beam milling of glassy carbon molds for the thermal imprinting of quartz and borosilicate glasses

    NASA Astrophysics Data System (ADS)

    Youn, Sung Won; Takahashi, Masaharu; Goto, Hiroshi; Maeda, Ryutaro

    2006-12-01

    The need for a flexible, low-cost and high-throughput process for the fabrication of a nano/micro glass-based micro fluidic device is becoming increasingly acute as the bio-MEMS industry is expanding very fast. In this study, repetitive-pass milling with a focused ion beam (FIB) was used for maskless and resistless fabrication of glassy carbon (GC) molds, which will then be the primary elements in the mass production of nano/micro glass devices by mold replication processes. The aim of the study is to establish basic process conditions and to investigate possible problems that occur during both FIB milling of GC and thermal imprint of glasses. First, the milled depth-beam dwell time curve for GC was investigated experimentally, and the relationship between the areal ion dose and the milled depth was formulated for application to the design of mold parts using FIB milling. Then, GC molds were produced and used for imprinting glasses to make micro fluidic parts. Surface contamination due to the FIB milling could be eliminated by a vacuum heat treatment at 1400 °C for 10 min. Finally, a dimensional mismatch arising from a thermal expansion coefficient mismatch between the GC mold and the glass materials was discussed. This article was presented at the 1st Topical Meeting on Microfactories 'Desktop MEMS and Nano Factories', Tsukuba, Japan, 17-19 October 2005.

  14. Fabrication of Glassy Carbon Molds Using Hydrogen Silsequioxane Patterned by Electron Beam Lithography as O2 Dry Etching Mask

    NASA Astrophysics Data System (ADS)

    Yasui, Manabu; Sugiyama, Yoshinari; Takahashi, Masaharu; Kaneko, Satoru; Uegaki, Jun-ichi; Hirabayashi, Yasuo; Sugimoto, Koh-ichi; Maeda, Ryutaro

    2008-06-01

    Glass is a good candidate material for optical devices because of its enhanced optical properties, the technique of die machining has not been established for the hot embossing of glass. In this study, we used the glassy carbon (GC) mold for the hot embossing of glass. An inductively coupled plasma reactive ion etching (ICP-RIE) using oxygen plasma was employed for the submicron structuring of the GC mold. Hydrogen silsesquioxane (HSQ) is a negative-type electron beam (EB) resist used to be resistant to oxygen plasma. HSQ patterns drawn by electron beam lithography (EBL) were used as the O2 dry etching mask. The etching selectivity between HSQ and GC was 35. The average of the extent of side etching was 40 nm at a depth of 300 nm. The side etching functioning as the draft angle was caused mainly by oxygen radicals, because HSQ patterns remained even after GC patterns were side-etched. We confirmed that the GC mold fabricated by O2 dry etching can be used for glass hot embossing. Since the mold lubricant was not rubbed on the mold surface, GC is the appropriate mold material for Pyrex glass.

  15. Pulsed amperometric detection at glassy carbon electrodes: A new waveform for sensitive and reproducible determination of electroactive compounds.

    PubMed

    Nardiello, Donatella; Palermo, Carmen; Natale, Anna; Quinto, Maurizio; Centonze, Diego

    2015-09-24

    In this work, the application of a new pulsed amperometric detection (PAD) waveform at a glassy carbon electrode, operating in typical chromatographic mobile phases, is proposed for the sensitive and reproducible determination of arylethanolaminic and phenolic moiety based compounds (e.g. beta-agonists and polyphenols). Preliminary experiments by cyclic voltammetry were carried out to investigate the electrochemical behaviour and to select the detection and cleaning electrode potentials. The proposed potential-time profile was designed to prevent the carbon electrode fouling under repeated analyses, thus ensuring a reproducible and sensitive quantitative determination, without the need of any mechanical or chemical electrode cleaning procedure. The waveform electrochemical parameters, including detection and delay times, were optimized in terms of sensitivity, limit of detection and response stability. The optimized waveform allowed the sensitive and stable detection of model compounds, such as clenbuterol and caffeic acid, that showed detection limits of 0.1 μg L(-1) and 14 μg L(-1), quantification limits of 0.4 μg L(-1) and 46 μg L(-1), and linearity up to 100 μg L(-1) (r = 0.9993) and 10 mg L(-1) (r = 0.9998), respectively. Similar results were obtained for other compounds of the same classes, with precision values under repeatability conditions ranging from 3.0 to 5.9%. The proposed method can be then considered as an excellent alternative to the post-column detection of beta-agonists, phenols and polyphenols. PMID:26423623

  16. Glassy carbon electrode modified with gold nanoparticles for ractopamine and metaproterenol sensing

    NASA Astrophysics Data System (ADS)

    Duan, Jiahua; He, Dawei; Wang, Wenshuo; Liu, Yongchuan; Wu, Hongpeng; Wang, Yongsheng; Fu, Ming

    2013-06-01

    In this Letter, the gold nanoparticles (AuNPs) were used as an enhanced material for selective detection of ractopamine and metaproterenol with electrochemical methods. The morphology and size of gold nanoparticles were characterized by scanning electron microscopy and absorption spectrum. Meanwhile, the electrical properties of modified glass carbon electrode (GCE) were studied by electrochemical impedance spectroscopy. The electrochemical behaviors of ractopamine and metaproterenol were well explained by PM3 calculated method and cyclic voltammetry. Importantly, the ractopamine and metaproterenol were effectively detected. The detection range has been broadened to (10-9-10-5 M) and the detection time has been shortened to a few minutes.

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

    PubMed

    Shoja, Yalda; Rafati, Amir Abbas; 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--NH2 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. PMID:26478378

  18. A sensitive amperometric immunosensor for alpha-fetoprotein based on carbon nanotube/DNA/Thi/nano-Au modified glassy carbon electrode.

    PubMed

    Ran, Xiao-Qi; Yuan, Ruo; Chai, Ya-Qin; Hong, Cheng-Lin; Qian, Xiao-Qing

    2010-09-01

    A novel amperometric immunosensor for the determination of alpha-fetoprotein (AFP) was constructed using films of multi-wall carbon nanotubes/DNA/thionine/gold nanoparticles (nano-Au). Firstly, multiwall carbon nanotubes (MWCNT) dispersed in poly(diallydimethlammonium chloride) (PDDA) were immobilized on the nano-Au film which was electrochemically deposited on the surface of glassy carbon electrode. Then a negatively charged DNA film was absorbed on the positively charged PDDA. Subsequently, thionine was attached to the electrode via the electrostatic interaction between thionine and the DNA. Finally, the nano-Au was retained on the thionine film for immobilization of AFP antibody (anti-AFP). The modification process was characterized by cyclic voltammetry (CV) and scanning electron microscope (SEM). The factors possibly influenced the performance of the proposed immunosensors were studied in detail. Under optimal conditions, the proposed immunosensor exhibited good electrochemical behavior to AFP in a two concentration ranges: 0.01-10.0 and 10.0-200.0 ng/mL with a relatively low detection limit of 0.04 ng/mL at three times the background noise. Moreover, the selectivity, repeatability and stability of the proposed immunosensor were acceptable. PMID:20627666

  19. Fibre laser machining for glassy carbon master mould and soft lithography based two-step printing for Ag nanoparticle structures

    NASA Astrophysics Data System (ADS)

    Hu, Qin; Chopra, Pranav

    2011-04-01

    Traditional manufacturing techniques widely used in semiconductor industries involve many processing steps that consume both time and material and lead to high cost. Soft Lithography (SL) offers a new way to print micro/nano structures, which is a fast and low cost alternative to the conventional route, although the high processing temperature of metals, semiconductors and ceramics limits the application SL techniques. In this paper we report the use of Ag nanoparticles as building blocks to make structures by combing the merits of SL, nanotechnology and laser engineering, which provide a simple additive route with low capital investment. Glassy carbon (GC) was chosen as the material for the rigid master mould, as no release coating is needed for replicating the polydimethylsiloxane (PDMS) mould. GC moulds were machined by a nanosecond-pulsed Yb fibre laser. The machined GC moulds were further cleaned by PDMS and the same fibre laser system to remove the process debris. The master mould was further replicated by PDMS. PDMS replicas with either positive or negative features from the master mould were attainable. A two-step strategy was used to print patterns using PDMS mould and Ag nanoparticle paste. Metal patterns were formed on various substrates, and the PDMS mould was left clean and ready for reuse. The resultant printed patterns were found to be uniform over millimetre range, with negligible residual layer, and the thickness of up to several micrometres. The thermal responses of Ag nanoparticles at various sintering temperatures were investigated. The factors affecting the resolution of printed structures were discussed.

  20. Silicon and aluminum doping effects on the microstructure and properties of polymeric amorphous carbon films

    NASA Astrophysics Data System (ADS)

    Liu, Xiaoqiang; Hao, Junying; Xie, Yuntao

    2016-08-01

    Polymeric amorphous carbon films were prepared by radio frequency (R.F. 13.56 MHz) magnetron sputtering deposition. The microstructure evolution of the deposited polymeric films induced by silicon (Si) and aluminum(Al) doping were scrutinized through infrared spectroscopy, multi-wavelength Raman spectroscopy, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The comparative results show that Si doping can enhance polymerization and Al doping results in an increase in the ordered carbon clusters. Si and Al co-doping into polymeric films leads to the formation of an unusual dual nanostructure consisting of cross-linked polymer-like hydrocarbon chains and fullerene-like carbon clusters. The super-high elasticity and super-low friction coefficients (<0.002) under a high vacuum were obtained through Si and Al co-doping into the films. Unconventionally, the co-doped polymeric films exhibited a superior wear resistance even though they were very soft. The relationship between the microstructure and properties of the polymeric amorphous carbon films with different elements doping are also discussed in detail.

  1. Correlation Between Thermal Interface Conductance and Mechanical Adhesion Strength in Cu-Coated Glassy Carbon

    NASA Astrophysics Data System (ADS)

    Pelzl, J.; Kijamnajsuk, P.; Chirtoc, M.; Horny, N.; Eisenmenger-Sittner, C.

    2015-09-01

    The influence of defective areas in the interface on the correlation between the thermal interface conductance and the mechanical adhesion strength was investigated on as-prepared and heat-treated samples of copper-coated carbon flat specimens with different bonding layers between the copper film and the substrate. The thermal interface conductance was determined by frequency-domain photothermal radiometry. The mechanical adhesion strength of the film coating was deduced from pull-off experiments. The imperfect interfaces were modeled by two different values for the thermal interface conductance, G1 and G2, which co-exist at different areas on the interface and are weighted according to their areas, A1 and A2. The model parameters were determined by adjusting the frequency dependence of the normalized phases and phase differences of the PTR signals from as-prepared and heat-treated samples. The total thermal conductance of the interface was found to exhibit a correlation with the adhesion strength for most of the heat-treated samples whereas, among the as-prepared samples, considerable deviations from such a trend exist. The observations are explained by the impact of supplementary stress on the adhesion strength measurements which are due to the strain developed during the preparation process at the interface. The interfacial stress and strain are mostly released during thermal annealing. A semi-empirical formula was developed that describes the impact of the defective areas on the adhesion strength using the experimentally determined thermal model parameters.

  2. Vivid Manifestation of Nonergodicity in Glassy Propylene Carbonate at High Pressures.

    PubMed

    Danilov, Igor V; Gromnitskaya, Elena L; Brazhkin, Vadim V

    2016-08-01

    As glasses are nonergodic systems, their properties should depend not only on external macroparameters, such as P and T, but also on the time of observation and thermobaric history. In this work, comparative ultrasonic studies of two groups of molecular propylene carbonate glasses obtained by quenching from a liquid at pressures of 0.1 and 1 GPa have been performed. Although the difference in the densities of the different groups of glasses is small (3-5%), they have significantly different elastic properties: the difference in the respective bulk moduli is 10-20%, and the difference in the respective shear moduli is 35-40% (!). This is due to the "closure of nanopores" in the glass obtained at 1 GPa. The pressure and temperature derivatives of the elastic moduli for these groups of glasses are also noticeably different. The glass-transition temperatures of glasses from different groups differ by 3-4 K. The character of absorption of ultrasound waves near the glass-transition temperature also differs for different groups of glasses. The differences in the behaviors of these groups of glasses disappear gradually above the glass-transition temperature, in the region of a liquid phase. Glasses with a wide diversity of physical properties can be obtained using various paths on the (T,P) diagram. PMID:27399845

  3. Facile synthesis of β-lactoglobulin-functionalized multi-wall carbon nanotubes and gold nanoparticles on glassy carbon electrode for electrochemical sensing.

    PubMed

    Du, Xin; Miao, Zhiying; Zhang, Di; Fang, Yuxin; Ma, Min; Chen, Qiang

    2014-12-15

    A facile approach was developed for the preparation of nanocomposite based on β-lactoglobulin (BLG)-functionalized multi-wall carbon nanotubes (MWCNTs) and gold nanoparticles (GNPs) for the first time. Owing to the amphipathic nature, BLG can be adopted onto the surface of MWCNTs to form BLG-MWCNTs with uniform dispersion in water. Taking advantage of sulfhydryl groups on BLG-MWCNTs, GNPs were decorated on the BLG-MWCNTs-modified glassy carbon electrode (GCE) by electrodeposition. The nanocomposite was characterized by transmission electron microscopy, scanning electron microscopy and X-ray spectroscopy analysis. Cyclic voltammetry and chronoamperometric method were used to evaluate the electrocatalytic ability of the nanocomposite. Furthermore, a glucose biosensor was developed based on the immobilization of glucose oxidase with cross-linking in the matrix of bovine serum albumin (BSA) on the nanocomposite modified GCE. The resulting biosensor exhibited high sensitivity (3.98 μA mM(-1)), wider linear range (0.025-5.5 mM), low detection limit (1.1 μM at the signal-to-noise ratio of 3) and fast response time (within 7s) for glucose detection. PMID:24984286

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

    PubMed

    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 0.5-100.0μmolL(-1) with a detection limit of 0.09μmolL(-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. PMID:27040259

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

    PubMed

    Shahrokhian, Saeed; Azimzadeh, Mahnaz; Amini, Mohammad K

    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 pH7.0 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 (0.03-10.0μ M) 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. PMID:26042700

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

    PubMed

    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. PMID:25435239

  7. Supramolecular intermediates in the synthesis of polymeric carbon nitride from melamine cyanurate

    SciTech Connect

    Dante, Roberto C.; Sánchez-Arévalo, Francisco M.; Chamorro-Posada, Pedro; Vázquez-Cabo, José; Lartundo-Rojas, Luis; and others

    2015-03-15

    The adduct of melamine and cyanuric acid (MCA) was used in past research to produce polymeric carbon nitride and precursors. The reaction yield was considerably incremented by the addition of sulfuric acid. The polymeric carbon nitride formation occurs around 450 °C at temperatures above the sublimation of the adduct components, which occurs around 400 °C. In this report the effect of sulfuric acid on MCA was investigated. It was found that the MCA rosette supramolecular channel structures behave as a solid solvent able to host small molecules, such as sulfuric acid, inside these channels and interact with them. Therefore, the sulfuric acid effect was found to be close to that of a solute that causes a temperature increment of the “solvent sublimation” enough to allowing the formation of polymeric carbon nitride to occur. Sulfate ions are presumably hosted in the rosette channels of MCA as shown by simulations. - Graphical abstract: The blend of melamine cyanurate and sulfuric acid behaves like a solution so that melamine cyanurate decomposition is shifted to temperatures high enough to react and form polymeric carbon nitride. - Highlights: • The adduct of melamine and cyanuric acid behaves as a solid solvent. • The blend of sulfuric acid and melamine cyanurate behaves like a solution. • Melamine cyanurate decomposition is shifted to higher temperatures by sulfuric acid. • The formation of polymeric carbon nitride occurs for these higher temperatures.

  8. A label-free electrochemical DNA biosensor based on covalent immobilization of salmonella DNA sequences on the nanoporous glassy carbon electrode.

    PubMed

    Amouzadeh Tabrizi, Mahmoud; Shamsipur, Mojtaba

    2015-07-15

    Herein, an easy and cost-effective approach to the immobilization of probe was performed. The amino modified salmonella ssDNA probe sequence was covalently linked with carboxylic group on the surface of nanoporous glassy carbon electrode to prepare the DNA biosensor. The differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) techniques were used for the determination of salmonella DNA in the concentration ranges of 10-400pM and 1-400pM with limits of detection of 2.1pM and 0.15pM, respectively. PMID:25710894

  9. Energetics and structural characterization of C60 polymerization in BN and carbon nanopeapods

    NASA Astrophysics Data System (ADS)

    Trave, Andrea; Ribeiro, Filipe J.; Louie, Steven G.; Cohen, Marvin L.

    2004-11-01

    As in the case of carbon nanotubes, also boron nitride nanotubes may host arrays of C60 molecules and form a nanopeapod (NPP). The observed separation between C60 molecules in BN NPP’s is consistently shorter than in carbon NPP’s, which influences their electronic properties. Here we report on total-energy pseudopotential density functional theory (DFT) calculations for polymerized and nonpolymerized C60 chains, and optimize their atomic structures to provide a description of their energetic landscape. A fully polymerized C60 chain and a C60 dimer are found to be more stable than nonpolymerized C60 , respectively, by 0.89 and 0.38eV/C60 . The geometry and energetics of an encapsulated C60 chain is not significantly different with respect to the isolated molecule. Encapsulation energies in BN and carbon NPP’s are, respectively, 1.56 and 1.67eV/C60 , which are significantly larger than the calculated activation energy for C60 polymerization, supporting the hypothesis that encapsulated C60 ’s in NPP’s are partially polymerized. Band structure analysis show that polymerization does not affect the gap width of the C60 chain. BN NPP’s are semiconductors with a gap width determined by the C60 . The lowest unoccupied C60 states lie just above the Fermi level in metallic carbon NPP’s and charge transfert could take place, affecting the C60 geometry.

  10. Electrochemical sensor for nitroaromatic type energetic materials using gold nanoparticles/poly(o-phenylenediamine-aniline) film modified glassy carbon electrode.

    PubMed

    Sağlam, Şener; Üzer, Ayşem; Tekdemir, Yasemin; Erçağ, Erol; Apak, Reşat

    2015-07-01

    In this work, a novel electrochemical sensor was developed for the detection of nitroaromatic explosive materials, based on a gold nanoparticle-modified glassy carbon (GC) electrode coated with poly(o-phenylenediamine-aniline film) (GC/P(o-PDA-co-ANI)-Aunano electrode). Nitroaromatic compounds were detected through their π-acceptor/donor interactions with o-phenylenediamine-aniline functionalities on the modified electrode surface. The enhanced sensitivities were achieved through π-π and charge-transfer (CT) interactions between the electron-deficient nitroaromatic compounds and σ-/π-donor amine/aniline groups linked to gold nanoparticles (Au-NPs), providing increased binding and preconcentration onto the modified GC-electrodes. Selective determination of nitroaromatic type explosives in the presence of nitramines was enabled by o-PDA and reusability of the electrode achieved by Au-NPs. Calibration curves of current intensity versus concentration were linear in the range of 2.5-40mgL(-1) for 2,4,6-trinitrotoluene (TNT) with a detection limit (LOD) of 2.1mgL(-1), 2-40mgL(-1) for 2,4-dinitrotoluene (DNT) (LOD=1.28mgL(-1)), 5-100mgL(-1) for tetryl (LOD=3.8mgL(-1)) with the use of the GC/P(o-PDA-co-ANI)-Aunano electrode. For sensor measurements, coefficients of variation of intra- and inter-assay measurements were 0.6% and 1.2%, respectively (N=5), confirming the high reproducibility of the proposed assay. Deconvolution of current contributions of synthetic (TNT+DNT) mixtures at peak potentials of constituents was performed by multiple linear regression analysis to provide high sensitivity for the determination of each constituent. Determination options for all possible mixture combinations of nitroaromatic explosives are presented in this work. The proposed methods were successfully applied to the analysis of nitroaromatics in military explosives, namely comp B, octol, and tetrytol. Method validation was performed against GC-MS on real post-blast residual samples

  11. Highly Sensitive Detection of Arsenite Based on Its Affinity toward Ruthenium Nanoparticles Decorated on Glassy Carbon Electrode.

    PubMed

    Gupta, Ruma; Gamare, Jayashree S; Pandey, Ashok K; Tyagi, Deepak; Kamat, Jayshree V

    2016-02-16

    Metallic ruthenium nanoparticles (Ru NPs) are formed on the glassy carbon electrode (GC) at electrodeposition potential of -0.75 V, as observed from X-ray photoelectron spectroscopy. Thus formed Ru NPs have the arsenite selective surface and conducting core that is ideally suited for designing a highly sensitive and reproducible response generating matrix for the arsenite detection at an ultratrace concentration in aqueous matrices. Contrary to this, arsenate ions sorb via chemical interactions on the ruthenium oxide (RuO2 and RuO3) NPs formed at -0.25 V, but not on the Ru NPs. For exploring a possibility of the quantification of arsenite in the ultratrace concentration range, the Ru NPs have been deposited on the GC by a potentiostatic pulse method of electrodeposition at optimized -0.75 V for 1000 s. Arsenite preconcentrates onto the Ru surface just by dipping the RuNPs/GC into the arsenite solution as it interacts chemically with Ru NPs. Electrochemical impedance spectroscopy of As(III) loaded RuNPs/GC shows a linear increase in the charge transfer resistance with an increase in As(III) conc. Using a differential pulse voltammetric technique, arsenite is oxidized to arsenate leading to its quantitative determination without any interference of Cu(2+) ions that are normally encountered in the water systems. Thus, the use of RuNPs/GC eliminates the need for a preconcentration step in stripping voltammetry, which requires optimization of the parameters like preconcentration potential, time, stirring, inferences, and so on. The RuNPs/GC based differential pulse voltammetric (DPV) technique can determine the concentration of arsenite in a few min with a detection limit of 0.1 ppb and 5.4% reproducibility. The sensitivity of 2.38 nA ppb(-1) obtained in the present work for As(III) quantification is considerably better than that reported in the literature, with a similar detection limit and mild conditions (pH = 2). The RuNPs/GC based DPV has been evaluated for its

  12. Three-dimensional polymeric structures of single-wall carbon nanotubes

    SciTech Connect

    Lian, Chao-Sheng; Wang, Jian-Tao

    2014-05-28

    We explore by ab initio calculations the possible crystalline phases of polymerized single-wall carbon nanotubes (P-SWNTs) and determine their structural, elastic, and electronic properties. Based on direct cross-linking and intertube sliding-assisted cross-linking mechanisms, we have identified a series of stable three-dimensional polymeric structures for the zigzag nanotubes up to (10,0). Among proposed P-SWNT phases, the structures with favorable diamond-like sp{sup 3} intertube bonding configuration and small tube cross-section distortion are found to be the most energetically stable ones. These polymeric crystalline phases exhibit high bulk and shear moduli superior to SWNT bundles, and show metallic or semiconducting properties depending on the diameter of constituent tubes. We also propose by hydrostatic pressure simulations that the intertube sliding between van der Waals bonded nanotubes may be an effective route to promote the polymerization of SWNTs under pressure.

  13. Three-dimensional polymeric structures of single-wall carbon nanotubes.

    PubMed

    Lian, Chao-Sheng; Wang, Jian-Tao

    2014-05-28

    We explore by ab initio calculations the possible crystalline phases of polymerized single-wall carbon nanotubes (P-SWNTs) and determine their structural, elastic, and electronic properties. Based on direct cross-linking and intertube sliding-assisted cross-linking mechanisms, we have identified a series of stable three-dimensional polymeric structures for the zigzag nanotubes up to (10,0). Among proposed P-SWNT phases, the structures with favorable diamond-like sp(3) intertube bonding configuration and small tube cross-section distortion are found to be the most energetically stable ones. These polymeric crystalline phases exhibit high bulk and shear moduli superior to SWNT bundles, and show metallic or semiconducting properties depending on the diameter of constituent tubes. We also propose by hydrostatic pressure simulations that the intertube sliding between van der Waals bonded nanotubes may be an effective route to promote the polymerization of SWNTs under pressure. PMID:24880313

  14. Gold nanoparticles decorated poly-melamine modified glassy carbon sensor for the voltammetric estimation of domperidone in pharmaceuticals and biological fluids.

    PubMed

    Rosy; Goyal, Rajendra N

    2015-08-15

    The electrochemical response of an unmodified glassy carbon (GCE), poly-melamine/GCE and gold nanoparticle (AuNP)/poly-melamine/GCE is compared in the present protocol for the sensitive and selective determination of domperidone (DOM). The AuNPs were synthesized in the laboratory and characterized using UV-visible spectroscopy and Transmission Electron Microscopy (TEM). Melamine was electropolymerized onto the glassy carbon surface using cyclic voltammetry and was investigated using Field Emission Scanning Electron Microscopy (FE-SEM) and Electrochemical Impedance Spectroscopy (EIS). The AuNP/poly-melamine/GCE exhibited the best electrochemical response among the three electrodes for the electro-oxidation of DOM, that was inferred from the EIS, cyclic and square wave voltammetry. The modified sensor showed a sensitive, stable and linear response in the concentration range of 0.05-100µM with a detection limit of 6nM. The selectivity of the proposed sensor was assessed in the presence of high concentration of major interfering molecules as xanthine, hypoxanthine, and uric acid. The analytical application of the sensor for the quantification of DOM in pharmaceutical formulations and biological fluids as urine and serum was also investigated and the results demonstrated a recovery of >95% with R.S.D of <5%. PMID:25966380

  15. Highly selective differential pulse voltammetric determination of phenazopyridine using MgCr2O4 nanoparticles decorated MWCNTs-modified glassy carbon electrode.

    PubMed

    Ensafi, Ali A; Arashpour, B; Rezaei, B; Allafchian, Ali R

    2013-11-01

    A selective modified glassy carbon electrode based on multiwall carbon nanotubes decorated with MgCr2O4 nanoparticles was fabricated and used for the determination of phenazopyridine using differential pulse voltammetry. The electrochemical response of the modified electrode toward phenazopyridine was characterized by different electrochemical methods including differential pulse voltammetry (DPV), cyclic voltammetry (CV), and impedance spectroscopy. The prepared electrode showed an efficient synergic effect on the oxidation of phenazopyridine at pH 6.0. The oxidation peak current was proportional to the concentration of phenazopyridine from 0.05 to 7.5 μmol L(-1). The detection limit was 0.025 μmol L(-1). The applicability of the method was confirmed with satisfactory results obtained through the assay of phenazopyridine in human plasma, urine samples, and pharmaceuticals. PMID:23838192

  16. Polymerization of euphorbia oil with Lewis acid in carbon dioxide media

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Boron trifluoride diethyl etherate (BF3-OEt2) Lewis acid catalyzed ring-opening polymerization of euphorbia oil (EO), a natural epoxy oil, in liquid carbon dioxide was conducted in an effort to develop useful vegetable oil based polymers. The resulting polymers (RPEO) were characterized by FTIR, 1H-...

  17. Lewis Acid Catalyzed Ring-opening Polymerization of Epoxidized Soybean Oil in Liquid Carbon Dioxide

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ring-opening polymerization of epoxidized soybean oil (ESO) catalyzed by boron trifluoride diethyl etherate (BF3•OEt2), in liquid carbon dioxide, was conducted in an effort to develop useful biobased biodegradable polymers. The resulting polymers (RPESO) were characterized by FTIR spectroscopy, diff...

  18. Boron Trifluoride Catalized Ring-Opening Polymerization of Epoxidized Soybean Oil in Liquid Carbon Dioxide

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Boron trifluoride diethyl etherate (BF3.OEt2) catalyzed ring-opening polymerization of epoxidized soybean oil (ESO), in liquid carbon dioxide, was conducted in an effort to develop useful biobased biodegradable polymers. The resulting polymers (RPESO) were characterized by FTIR spectroscopy, differ...

  19. Organocatalytic Ring-Opening Polymerization of Trimethylene Carbonate to Yield a Biodegradable Polycarbonate

    ERIC Educational Resources Information Center

    Chan, Julian M. W.; Zhang, Xiangyi; Brennan, Megan K.; Sardon, Haritz; Engler, Amanda C.; Fox, Courtney H.; Frank, Curtis W.; Waymouth, Robert M.; Hedrick, James L.

    2015-01-01

    In this laboratory experiment, students work in pairs to synthesize a simple aliphatic polycarbonate via ring-opening polymerization of trimethylene carbonate using 1,8-diazabicyclo[5.4.0]undec-7-ene and thiourea as organocatalysts. Following polymer isolation, students cool the material in a dry ice/acetone bath to observe its glass-transition…

  20. Complementing Graphenes: 1D Interplanar Charge Transport in Polymeric Graphitic Carbon Nitrides.

    PubMed

    Merschjann, Christoph; Tschierlei, Stefanie; Tyborski, Tobias; Kailasam, Kamalakannan; Orthmann, Steven; Hollmann, Dirk; Schedel-Niedrig, Thomas; Thomas, Arne; Lochbrunner, Stefan

    2015-12-22

    Charge transport in polymeric graphitic carbon nitrides is shown to proceed via diffusive hopping of electron and hole polarons with reasonably high mobilities >10(-5) cm(2) V(-1) s(-1). The power-law behavior of the ultrafast luminescence decay exhibits that the predominant transport direction is perpendicular to the graphitic polymer sheets, thus complementing 2D materials like graphene. PMID:26543003

  1. Electrocatalytic oxidation of 2-mercaptoethanol using modified glassy carbon electrode by MWCNT in combination with unsymmetrical manganese (II) Schiff base complexes

    SciTech Connect

    Mohebbi, Sajjad Eslami, Saadat

    2015-06-15

    Highlights: • High electocatalytic efficiency and stability of modified hybrid electrode GC/MWCNTs/MnSaloph. • Direct reflection of catalytic activity of manganese complexes on electrocatalytic oxidation of 2-ME. • Decreasing overpotential and increasing catalytic peak current toward oxidation of 2-ME. • Deposition of range of novel substituted N{sub 2}O{sub 2} Saloph complexes of manganese(II) on GCE/MWCNT. • Enhancement of electrocatalytic oxidation activity upon electron donating substitutions on the Saloph. - Abstract: The performance of modified hybrid glassy carbon electrode with composite of carbon nanotubes and manganese complexes for the electrocatalytic oxidation of 2-mercaptoethanol is developed. GC electrode was modified using MWCNT and new N{sub 2}O{sub 2} unsymmetrical tetradentate Schiff base complexes of manganese namely Manganese Saloph complexes 1-5, with general formula Mn[(5-x-4-y-Sal)(5-x′-4-y′-Sal) Ph], where x, x′ = H, Br, NO{sub 2} and y, y′ = H, MeO. Direct immobilization of CNT on the surface of GCE is performed by abrasive immobilization, and then modified by manganese(II) complexes via direct deposition method. These novel modified electrodes clearly demonstrate the necessity of modifying bare carbon electrodes to endow them with the desired behavior and were identified by HRTEM. Also complexes were characterized by elemental analyses, MS, UV–vis and IR spectroscopy. Modified hybrid GC/MWCNT/MnSaloph electrode exhibits strong and stable electrocatalytic activity towards the electrooxidation of 2-mercaptoethanol molecules in comparison with bare glassy carbon electrode with advantages of very low over potential and high catalytic current. Such ability promotes the thiol’s electron transfer reaction. Also, electron withdrawing substituent on the Saloph was enhanced electrocatalytic oxidation activity.

  2. Polymeric membranes for super critical carbon dioxide separations

    NASA Astrophysics Data System (ADS)

    Kosuri, Madhava R.

    2009-12-01

    Providing an energy efficient recycle for the TeflonRTM synthesis process is of great interest due to environmental and economic reasons. This recycle step involves separating CO2 from a stream containing scCO2 and valuable monomer (C2F4). Membranes provide economical and environmental friendly separations compared to conventional methods (e.g. distillation, amine absorption). Therefore, I am investigating membrane materials that are well-suited for this important separation. Developing a robust membrane that can withstand the aggressive scCO 2 environment (˜1070 psi of CO2) is a key challenge. Supercritical CO2 swells traditional polymeric membrane materials, thereby increasing segmental mobility of the polymer chains which leads to a decrease in separation capacity. There have been no polymeric membrane materials identified in the literature which are suitable for this separation. In this work, I have identified an advanced polymer, TorlonRTM (a polyamide-imide), that solves this problem. After determining the appropriate material, it is important to choose a membrane morphology that is industrially desirable. The asymmetric hollow fiber membrane morphology provides the highest productivity compared to other membrane types. I have successfully produced defect-free asymmetric hollow fiber membranes using TorlonRTM that withstand high pressure feeds. These membranes have been shown to provide selective separations under scCO2 conditions without being plasticized. To further improve the separation performance of TorlonRTM membranes, the mixed matrix concept was explored. Zeolite 4A, which is relatively more permeable and selective compared to TorlonRTM, was chosen as the sieve material. Mixed matrix membranes from TorlonRTM and zeolite 4A were made and their separation performance was measured. Based on these experimental measurements and Maxwell modeling, challenges in making successful mixed matrix membranes were identified and feasible solutions for these

  3. Synthesis and characterization of carbon fibers functionalized with poly (glycidyl methacrylate) via atom transfer radical polymerization

    NASA Astrophysics Data System (ADS)

    Wu, Yongwei; Xiong, Lei; Qin, Xiaokang; Wang, Zhengyue; Ding, Bei; Ren, Huan; Pi, Xiaolong

    2015-07-01

    In this work, polyacrylonitrile (PAN)-based carbon fibers (CF) were chemically modified with poly (glycidyl methacrylate) (PGMA) via atom transfer radical polymerization (ATRP) to improve the interaction between the CF and polymer matrix. The FT-IR, TGA, and XPS were used to determine the chemical structure of the resulting products and the quantities of PGMA chains grafted from the CF surface. The experimental results confirm that the CF surface was functionalized and glycidyl methacrylate was graft-polymerized onto the CF, and the grafting content of polymer could reach 10.2%.

  4. Friction Behaviour of Polymeric Composite Materials Mixed with Carbon Fibers Having Different Orientations Layout

    NASA Astrophysics Data System (ADS)

    Caliman, R.

    2016-06-01

    This paper presents a study of the friction properties of polymeric composite materials reinforced with unidirectional carbon fibers having different stratified structure. So, the composites are complex and versatile materials but their behaviour in practice is not fully studied. For instance, these polymeric composite materials mixed with carbon fibers after being investigated in terms of wear, did not elucidate the effect of fiber orientation on wear properties. Is therefore necessary to investigate the effect of carbon fibers orientation on the friction-wear properties of the reinforced composite materials tested to abrasive and adhesive friction. Research work has been done with unidirectional composite materials having overlap 18 successive layers made from a polymeric resine and 60% of carbon fibers. The stratified structure was obtained by compressing multiple pre-impregnated strips, positioned manually. During this experimental work, three types of test samples were investigated: parallel, normal and anti-parallel, taking in consideration the carbon fibre orientation with respect to the sliding direction. The friction coefficient is computed function to the friction load and loading value. Also, the specific wear rate was calculated according to: the mass loss, density, the normal contact surface, the sliding distance and load rating.

  5. Method of improving adhesion of carbon fibers with a polymeric matrix

    DOEpatents

    Vautard, Frederic; Ozcan, Soydan; Paulauskas, Felix Leonard

    2016-06-14

    A functionalized carbon fiber having covalently bound on its surface a partially cured epoxy or amine-containing sizing agent, wherein at least a portion of epoxide or amine groups in the sizing agent are available as uncrosslinked epoxide or amine groups, which corresponds to a curing degree of epoxide or amine groups of no more than about 0.6. Composites comprised of these functionalized carbon fibers embedded in a polymeric matrix are also described. Methods for producing the functionalized carbon fibers and composites thereof are also described.

  6. A Highly Sensitive Oligonucleotide Hybridization Assay for Klebsiella pneumoniae Carbapenemase with the Probes on a Gold Nanoparticles Modified Glassy Carbon Electrode.

    PubMed

    Pan, Hong-zhi; Yu, Hong- Wei; Wang, Na; Zhang, Ze; Wan, Guang-Cai; Liu, Hao; Guan, Xue; Chang, Dong

    2015-01-01

    To develop a new electrochemical DNA biosensor for determination of Klebsiella pneumoniae carbapenemase, a highly sensitive and selective electrochemical biosensor for DNA detection was constructed based on a glassy carbon electrode (GCE) modified with gold nanoparticles (Au-nano). The Au-nano/GCE was characterized by scanning electromicroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The hybridization detection was measured by differential pulse voltammetry using methylene blue as the hybridization indicator. The dynamic range of detection of the sensor for the target DNA sequences was from 1 × 10(-11) to 1 × 10(-8) M, with an LOD of 1 × 10(-12) M. The DNA biosensor had excellent specificity for distinguishing complementary DNA sequence in the presence of non-complementary and mismatched DNA sequence. The Au-nano/GCE showed significant improvement in electrochemical characteristics, and this biosensor was successfully applied for determination of K. pneumoniae. PMID:26651586

  7. Sensitivity and selectivity determination of BPA in real water samples using PAMAM dendrimer and CoTe quantum dots modified glassy carbon electrode.

    PubMed

    Yin, Huanshun; Zhou, Yunlei; Ai, Shiyun; Chen, Quanpeng; Zhu, Xiangbin; Liu, Xianggang; Zhu, Lusheng

    2010-02-15

    Bisphenol A (BPA) is an environmental pollutant to disrupt endocrine system or cause cancer, thus the detection of BPA is very important. Herein, an amperometric sensor was fabricated based on immobilized CoTe quantum dots (CoTe QDs) and PAMAM dendrimer (PAMAM) onto glassy carbon electrode (GCE) surface. The cyclic voltammogram of BPA on the sensor exhibited a well-defined anodic peak at 0.490V in 0.1M pH 8.0 PBS. The determination conditions were optimized and the kinetic parameters were calculated. The linear range was 1.3 x 10(-8) to 9.89 x 10(-6)M with the correlation coefficient of 0.9999. The limit of detection was estimated to be 1 x 10(-9)M. The current reached the steady-state current within about 5s. Furthermore, the fabricated sensor was successfully applied to determine BPA in real water samples. PMID:19782469

  8. Enhanced amperometric detection of metronidazole in drug formulations and urine samples based on chitosan protected tetrasulfonated copper phthalocyanine thin-film modified glassy carbon electrode.

    PubMed

    Meenakshi, S; Pandian, K; Jayakumari, L S; Inbasekaran, S

    2016-02-01

    An enhanced electrocatalytic reduction of metronidazole antibiotic drug molecule using chitosan protected tetrasulfonated copper phthalocyanine (Chit/CuTsPc) thin-film modified glassy carbon electrode (GCE) has been developed. An irreversible reduction occurs at -0.47V (vs. Ag/AgCl) using Chit/CuTsPc modified GCE. A maximum peak current value is obtained at pH1 and the electrochemical reduction reaction is a diffusion controlled one. The detection limit is found to be 0.41nM from differential pulse voltammetry (DPV) method. This present investigation method is adopted for electrochemical detection of metronidazole in drug formulation and urine samples by using DPV method. PMID:26652358

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Electrocatalytic oxidation behavior of NADH at Pt/Fe3O4/reduced-graphene oxide nanohybrids modified glassy carbon electrode and its determination.

    PubMed

    Roushani, Mahmoud; Hoseini, S Jafar; Azadpour, Mitra; Heidari, Vahid; Bahrami, Mehrangiz; Maddahfar, Mahnaz

    2016-10-01

    We have developed Pt/Fe3O4/reduced-graphene oxide nanohybrids modified glassy carbon (Pt/Fe3O4/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/Fe3O4/RGO/GC electrode was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Due to the synergistic effect between Pt, Fe3O4 and RGO, the nanohybrid exhibited excellent performance toward dihydronicotinamide adenine dinucleotide (NADH) oxidation in 0.1M phosphate buffer solution, pH7.0, with a low detection limit of 5nM. PMID:27287119

  11. Construction of TiO2 nanosheets modified glassy carbon electrode (GCE/TiO2) for the detection of hydrazine

    NASA Astrophysics Data System (ADS)

    Ahmad, Khursheed; Mohammad, Akbar; Rajak, Richa; Mobin, Shaikh M.

    2016-07-01

    TiO2 nanosheets were synthesized via solvothermal method and characterized using powder x-ray diffraction (PXRD), UV–vis spectroscopy, scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) mapping. A binder free hydrazine sensor was fabricated by modifying the glassy carbon electrode (GCE) with TiO2 nanosheets, using simple drop casting method (GCE/TiO2). The modified GCE/TiO2 was employed for detection of hydrazine which exhibited a very high sensitivity of 70 μA mM‑1 cm‑2 with a limit of detection (LOD), 28 μM using cyclic voltammetry whereas a highest sensitivity 330 μA mM‑1 cm‑2 and LOD, 150 μM was obtained by employing square wave voltammetry.

  12. Continuum percolation of carbon nanotubes in polymeric and colloidal media

    PubMed Central

    Kyrylyuk, Andriy V.; van der Schoot, Paul

    2008-01-01

    We apply continuum connectedness percolation theory to realistic carbon nanotube systems and predict how bending flexibility, length polydispersity, and attractive interactions between them influence the percolation threshold, demonstrating that it can be used as a predictive tool for designing nanotube-based composite materials. We argue that the host matrix in which the nanotubes are dispersed controls this threshold through the interactions it induces between them during processing and through the degree of connectedness that must be set by the tunneling distance of electrons, at least in the context of conductivity percolation. This provides routes to manipulate the percolation threshold and the level of conductivity in the final product. We find that the percolation threshold of carbon nanotubes is very sensitive to the degree of connectedness, to the presence of small quantities of longer rods, and to very weak attractive interactions between them. Bending flexibility or tortuosity, on the other hand, has only a fairly weak impact on the percolation threshold. PMID:18550818

  13. Synthesis of soybean oil-based polymeric surfactants in supercritical carbon dioxide and investigation of their surface properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This paper reports the preparation of polymeric surfactants (HPSO) via a two-step synthetic procedure: polymerization of soybean oil (PSO) in supercritical carbon dioxide and followed by hydrolysis of PSO with a base. HPSO was characterized and identified by using a combination of FTIR, 1H NMR, 13C...

  14. Simultaneous determination of norepinephrine, acetaminophen and tyrosine by differential pulse voltammetry using Au-nanoparticles/poly(2-amino-2-hydroxymethyl-propane-1,3-diol) film modified glassy carbon electrode.

    PubMed

    Taei, M; Ramazani, G

    2014-11-01

    A novel Au-nanoparticles/poly-(2-amino-2-hydroxymethyl-propane-1,3-diol) film modified glassy carbon electrode (AuNPs/poly(trisamine)/GCE) was constructed for the simultaneous determination of norepinephrine (NE), acetaminophen (AC) and L-tyrosine (Tyr) by differential pulse voltammetry. Electrochemical impedance spectroscopy and scanning electron microscopy indicate that the trisamine film was successfully polymerized on the surface of GCE and the film efficiently decreased the charge transfer resistance value of electrode and improved the electron transfer kinetic between analytes and electrode. The separation of the oxidation peak potentials for NE-AC and AC-Tyr were about 160 mV and 240 mV, respectively. The calibration curves for NE, AC and Tyr were obtained in the range of 1.3-230.1 μmol L(-1), 1.90-188.0 μmol L(-1), and 3.9-61.8 μmol L(-1), respectively. The detection limits (S/N=3) were 0.07 μmol L(-1), 0.1 μmol L(-1) and 0.9 μmol L(-1), for NE, AC and Tyr, respectively. The diffusion coefficient and the catalytic rate constant for the oxidation reaction of NE at AuNPs/poly(trisamine)/GCE were calculated as 1.55 (±0.2)×10(-6) cm2 s(-1) and 2.28 (±0.17)×10(3) mol(-1) L s(-1), respectively. Finally, AuNPs/poly(trisamine)/GCE was satisfactorily used for the determination of NE, AC, and Tyr in pharmaceutical and biological samples. PMID:25240479

  15. Enhanced Polymer Grafting from Multiwalled Carbon Nanotubes through Living Anionic Surface-Initiated Polymerization.

    SciTech Connect

    Sakellariou, Georgios; Ji, Haining; Mays, Jimmy; Baskaran, Durairaj

    2008-01-01

    Anionic surface-initiated polymerization of ethylene oxide and styrene has been performed using multiwalled carbon nanotubes (MWNTs) functionalized with anionic initiators. The surface of MWNTs was modified via covalent attachment of precursor anions such as 4-hydroxyethyl benzocyclobutene (BCBEO) and 1-benzocyclobutene-1 -phenylethylene (BCB-PE) through Diels-Alder cycloaddition at 235 C. Surface-functionalized MWNTs-g-(BCB-EO)n and MWNTs-g-(BCB-PE)n with 23 and 54 wt % precursor initiators, respectively, were used for the polymerizations. Alkoxide anion on the surface of MWNTs-g-(BCB-EO)n was generated through reaction with potassium triphenylmethane for the polymerization of ethylene oxide in tetrahydrofuran and phenyl substituted alkyllithium was generated from the surface of MWNTs-g-(BCB-PE)n using sec-butyllithium for the polymerization of styrene in benzene. In both cases, the initiation was found to be very slow because of the heterogeneous reaction medium. However, the MWNTs gradually dispersed in the reaction medium during the polymerization. A pale green color was noticed in the case of ethylene oxide polymerization and the color of initiator as well as the propagating anions was not discernible visually in styrene polymerization. Polymer grafted nanocomposites, MWNTs-g-(BCB-PEO)n and MWNTs-g-(BCB-PS)n containing a very high percentage of hairy polymer with a small fraction of MWNTs (<1 wt %) were obtained. The conversion of ethylene oxide and the weight percent of PEO on the surface of the MWNTs increased with increasing reaction time indicating a controlled polymerization. The polymer-grafted MWNTs were characterized using FTIR, 1H NMR, Raman spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and transmission electron microscopy (TEM). Size exclusion chromatography of the polymer grafted MWNTs revealed broad molecular weight distributions (1.3 < Mw/Mn < 1.8) indicating the presence of different sizes of polymer nanocomposites

  16. 2D to 3D transition of polymeric carbon nitride nanosheets

    SciTech Connect

    Chamorro-Posada, Pedro; Vázquez-Cabo, José; Martín-Ramos, Pablo; Martín-Gil, Jesús; Navas-Gracia, Luis M.; Dante, Roberto C.

    2014-11-15

    The transition from a prevalent turbostratic arrangement with low planar interactions (2D) to an array of polymeric carbon nitride nanosheets with stronger interplanar interactions (3D), occurring for samples treated above 650 °C, was detected by terahertz-time domain spectroscopy (THz-TDS). The simulated 3D material made of stacks of shifted quasi planar sheets composed of zigzagged polymer ribbons, delivered a XRD simulated pattern in relatively good agreement with the experimental one. The 2D to 3D transition was also supported by the simulation of THz-TDS spectra obtained from quantum chemistry calculations, in which the same broad bands around 2 THz and 1.5 THz were found for 2D and 3D arrays, respectively. This transition was also in accordance with the tightening of the interplanar distance probably due to an interplanar π bond contribution, as evidenced also by a broad absorption around 2.6 eV in the UV–vis spectrum, which appeared in the sample treated at 650 °C, and increased in the sample treated at 700 °C. The band gap was calculated for 1D and 2D cases. The value of 3.374 eV for the 2D case is, within the model accuracy and precision, in a relative good agreement with the value of 3.055 eV obtained from the experimental results. - Graphical abstract: 2D lattice mode vibrations and structural changes correlated with the so called “2D to 3D transition”. - Highlights: • A 2D to 3D transition has been detected for polymeric carbon nitride. • THz-TDS allowed us to discover and detect the 2D to 3D transition of polymeric carbon nitride. • We propose a structure for polymeric carbon nitride confirming it with THz-TDS.

  17. A finite element method for the thermochemical decomposition of polymeric materials. II - Carbon phenolic composites

    NASA Technical Reports Server (NTRS)

    Sullivan, R. M.; Salamon, N. J.

    1992-01-01

    A previously developed formulation for modeling the thermomechanical behavior of chemically decomposing, polymeric materials is verified by simulating the response of carbon phenolic specimens during two high temperature tests: restrained thermal growth and free thermal expansion. Plane strain and plane stress models are used to simulate the specimen response, respectively. In addition, the influence of the poroelasticity constants upon the specimen response is examined through a series of parametric studies.

  18. Development of sensitive amperometric hydrogen peroxide sensor using a CuNPs/MB/MWCNT-C60-Cs-IL nanocomposite modified glassy carbon electrode.

    PubMed

    Roushani, Mahmoud; Bakyas, Kobra; Zare Dizajdizi, Behruz

    2016-07-01

    A sensitive hydrogen peroxide (H2O2) sensor was constructed based on copper nanoparticles/methylene blue/multiwall carbon nanotubes-fullerene-chitosan-ionic liquid (CuNPs/MB/MWCNTs-C60-Cs-IL) nanocomposites. The MB/MWCNTs-C60-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-C60-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 H2O2 in the range of 0.2μM to 2.0mM, and the detection limit is 55.0nM (S/N=3). In addition, the modified electrode was used to determine H2O2 concentration in human blood serum sample with satisfactory results. PMID:27127028

  19. Covalent attachment of diphosphine ligands to glassy carbon electrodes via Cu-catalyzed alkyne-azide cycloaddition. Metallation with Ni(II).

    PubMed

    Das, Atanu K; Engelhard, Mark H; Lense, Sheri; Roberts, John A S; Bullock, R Morris

    2015-07-21

    Covalent tethering of P(Ph)2N(C6H4C≡CH)2 ligands (P(Ph)2N(C6H4C≡CH)2 = 1,5-di-(4-ethynylphenyl)-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane) to planar, azide-terminated glassy carbon electrode surfaces has been accomplished using a Cu(I)-catalyzed alkyne-azide cycloaddition (CuAAC) coupling reaction, using a BH3←P protection-deprotection strategy. Deprotected, surface-confined ligands were metallated using [Ni(II)(MeCN)6](BF4)2. X-ray photoelectron spectroscopic measurements demonstrate that metallation introduced 1.3 equivalents Ni(II) per diphosphine onto the electrode surface. Exposure of the surface to a second diphosphine ligand, P(Ph)2N(Ph)2, resulted in the removal of Ni from the surface. Protection, coupling, deprotection, and metallation conditions were optimized using solution-phase model systems, with benzyl azide as a model for the azide-terminated carbon surface; these reactions generate a [Ni(II)(diphosphine)2](2+) complex. PMID:25811536

  20. Preparation of porous carbons from polymeric precursors modified with acrylated kraft lignin

    NASA Astrophysics Data System (ADS)

    Sobiesiak, M.

    2016-04-01

    The presented studies concern the preparation of porous carbons from a BPA.DA-St polymer containing acrylated kraft lignin as a monomer. The porous polymeric precursor in the form of microspheres was synthesized in suspension polymerization process. Next samples of the polymer were impregnated with acetic acid or aqueous solution of acetates (potassium or ammonia), dried and carbonised in nitrogen atmosphere at 450°C. After carbonization microspherical shape of the materials was remained, that is desired feature for potential application in chromatography or SPE technique. Chemical and textural properties of the porous carbon adsorbents were characterized using infrared spectroscopy (ATR-FTIR), thermogravimetry analyses with mass spectrometry of released gases (TG-MS) and nitrogen sorption experiments. The presented studies revealed the impregnation is useful method for development of porous structure of carbonaceous materials. The highest values of porous structure parameters were obtained when acetic acid and ammonium acetate were used as impregnating substances. On the surface of the materials oxygen functional groups are present that is important for specific interactions during sorption processes. The highest contents of functionalities were observed for carbon BPA.DA-St-LA-C-AcNH4.

  1. Ultrahigh Surface Area Three-Dimensional Porous Graphitic Carbon from Conjugated Polymeric Molecular Framework

    PubMed Central

    2015-01-01

    Porous graphitic carbon is essential for many applications such as energy storage devices, catalysts, and sorbents. However, current graphitic carbons are limited by low conductivity, low surface area, and ineffective pore structure. Here we report a scalable synthesis of porous graphitic carbons using a conjugated polymeric molecular framework as precursor. The multivalent cross-linker and rigid conjugated framework help to maintain micro- and mesoporous structures, while promoting graphitization during carbonization and chemical activation. The above unique design results in a class of highly graphitic carbons at temperature as low as 800 °C with record-high surface area (4073 m2 g–1), large pore volume (2.26 cm–3), and hierarchical pore architecture. Such carbons simultaneously exhibit electrical conductivity >3 times more than activated carbons, very high electrochemical activity at high mass loading, and high stability, as demonstrated by supercapacitors and lithium–sulfur batteries with excellent performance. Moreover, the synthesis can be readily tuned to make a broad range of graphitic carbons with desired structures and compositions for many applications. PMID:27162953

  2. Ultrahigh Surface Area Three-Dimensional Porous Graphitic Carbon from Conjugated Polymeric Molecular Framework.

    PubMed

    To, John W F; Chen, Zheng; Yao, Hongbin; He, Jiajun; Kim, Kwanpyo; Chou, Ho-Hsiu; Pan, Lijia; Wilcox, Jennifer; Cui, Yi; Bao, Zhenan

    2015-05-27

    Porous graphitic carbon is essential for many applications such as energy storage devices, catalysts, and sorbents. However, current graphitic carbons are limited by low conductivity, low surface area, and ineffective pore structure. Here we report a scalable synthesis of porous graphitic carbons using a conjugated polymeric molecular framework as precursor. The multivalent cross-linker and rigid conjugated framework help to maintain micro- and mesoporous structures, while promoting graphitization during carbonization and chemical activation. The above unique design results in a class of highly graphitic carbons at temperature as low as 800 °C with record-high surface area (4073 m(2) g(-1)), large pore volume (2.26 cm(-3)), and hierarchical pore architecture. Such carbons simultaneously exhibit electrical conductivity >3 times more than activated carbons, very high electrochemical activity at high mass loading, and high stability, as demonstrated by supercapacitors and lithium-sulfur batteries with excellent performance. Moreover, the synthesis can be readily tuned to make a broad range of graphitic carbons with desired structures and compositions for many applications. PMID:27162953

  3. Surface-initiated graft polymerization on multiwalled carbon nanotubes pretreated by corona discharge at atmospheric pressure.

    PubMed

    Xu, Lihua; Fang, Zhengping; Song, Ping'an; Peng, Mao

    2010-03-01

    Surface-initiated graft polymerization on multi-walled carbon nanotubes pretreated with a corona discharge at atmospheric pressure was explored. The mechanism of the corona-discharge-induced graft polymerization is discussed. The results indicate that MWCNTs were encapsulated by poly(glycidyl methacrylate) (PGMA), demonstrating the formation of PGMA-grafted MWCNTs (PGMA-g-MWCNTs), with a grafting ratio of about 22 wt%. The solubility of PGMA-g-MWCNTs in ethanol was dramatically improved compared to pristine MWCNTs, which could contribute to fabricating high-performance polymer/MWCNTs nanocomposites in the future. Compared with most plasma processes, which operate at low pressures, corona discharge has the merit of working at atmospheric pressure. PMID:20644821

  4. Study of the overall behavior of thin films of the 7,7,8,8-tetracyanoquinodimethane neutral/anion couple on glassy carbon electrodes in the presence of cesium ion.

    PubMed

    Gómez, L; Rodríguez-Amaro, R

    2008-10-01

    The overall electrochemistry of 7,7,8,8-tetracyanoquinodimethane thin films on glassy carbon electrodes in media containing Cs+ ions is explained in light of a layer-by-layer nucleation and growth model, and kinetic data for the processes involved are reported. Using in situ UV-vis spectroelectrochemistry allowed available mechanistic knowledge on such processes to be expanded and the presence of various intermediates in the redox reactions confirmed. PMID:18785713

  5. Dispersion of Single Wall Carbon Nanotubes by in situ Polymerization Under Sonication

    NASA Technical Reports Server (NTRS)

    Park, Cheol; Ounaies, Zoubeida; Watson, Kent A.; Crooks, Roy E.; Smith, Joseph, Jr.; Lowther, Sharon E.; Connell, John W.; Siochi, Emilie J.; Harrison, Joycelyn S.; St.Clair, Terry L.

    2002-01-01

    Single wall nanotube reinforced polyimide nanocomposites were synthesized by in situ polymerization of monomers of interest in the presence of sonication. This process enabled uniform dispersion of single wall carbon nanotube (SWNT) bundles in the polymer matrix. The resultant SWNT-polyimide nanocomposite films were electrically conductive (antistatic) and optically transparent with significant conductivity enhancement (10 orders of magnitude) at a very low loading (0.1 vol%). Mechanical properties as well as thermal stability were also improved with the incorporation of the SWNT.

  6. Conductive carbon filled polymeric electrodes: novel ion optical elements for time-of-flight mass spectrometers.

    PubMed

    Appel, Matthew F; van der Veer, Wytze E; Benter, Thorsten

    2002-10-01

    A new technique employing conductive polymeric electrodes for the generation of linear electric fields is proposed and validated. A hollow cylinder comprised of DuPont's Vespel SP-22, a polymer loaded with conductive carbon particles, is used to enhance the performance of a hybrid reflectron compared to a conventional dual stage gridless reflectron composed of discrete metal ring electrodes. Both devices have comparable physical dimensions and nearly identical ion optical properties. Instrumental resolution measurements are used to validate this novel design. PMID:12387322

  7. Synthesis of crumpled nanosheets of polymeric carbon nitride from melamine cyanurate

    SciTech Connect

    Dante, Roberto C.; Martín-Ramos, Pablo; Sánchez-Arévalo, F.M.; Huerta, L.; Bizarro, M.; Navas-Gracia, Luis M.; Martín-Gil, Jesús

    2013-05-01

    Polymeric carbon nitride was synthesized by pyrolysis in nitrogen flux at different temperatures between 450 and 700 °C using melamine cyanurate as a reagent and sulfuric acid as a catalyst. The obtained carbon nitride consisted of curled nanosheets (650 °C), and globular particles (700 °C) with formula C₆N₇NHNH₂. The reaction yield of the catalyzed reaction was around the 15% for the sample treated at 700 °C, in a tapped crucible. The optical band gap of the polymer obtained at 700 °C is around 2.9 eV. The gap to the Fermi level is around 2 eV, considerably above the half of the band gap (due to electrons trapped in the gap), indicating that the polymer is probably a n-type semiconductor. - Graphical abstract: Transition from amorphous to crystalline carbon nitride, which is composed of globular particles and is a n-type wide band semiconductor. Highlights: • We synthetized carbon nitride using melamine cyanurate. • The reaction of carbon nitride formation is catalyzed by sulfuric acid. • The carbon nitride obtained at 700 °C is composed of globular particles. • The material obtained at 700 °C is a n-type semiconductor.

  8. 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.

    PubMed

    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. PMID:25882401

  9. Differential pulse anodic stripping voltammetry for detection of As (III) by Chitosan-Fe(OH)3 modified glassy carbon electrode: A new approach towards speciation of arsenic.

    PubMed

    Saha, Suparna; Sarkar, Priyabrata

    2016-09-01

    An efficient electrochemical sensor for As(III) was developed based on adsorption of arsenic on a specially modified electrodes at some applied potential and subsequent i) stripping at a fixed potential by anodic stripping voltammetry ii) analysis by generating surface plasmon resonance (SPR). The working glassy carbon electrode was modified by Chitosan-Fe(OH)3 composite and a reducing agent L-cysteine. The composite enhanced adsorption of As(III) and subsequent reduction to As(O) moieties and measurement by anodic stripping. The surface property of modified electrode was characterized by SEM, AFM, FTIR, XPS and electrochemistry was analyzed by impedance spectroscopy (EIS). Surface Plasmon resonance (SPR) was also employed to investigate the As(III) binding capability of polymer matrix. Several optimum voltammetric parameters e.g supporting electrolyte; 0.1M acetate buffer (pH 5.2) deposition potential, -0.9V; deposition time, 100s were established for anodic stripping voltammetry (ASV). A linear correlation was obtained in the range of 2-100ppb for ASV (R(2) 0.974) with limit of detection 0.072ppb. A variety of common coexistent ions such as Mn, Zn, Pb, Cu, Cd in water samples showed no interferences on the As (III) determination. The method was applied successfully to real samples collected from arsenic affected areas of West Bengal, India. PMID:27343601

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

    PubMed

    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. PMID:27211634

  11. Determination of Silver(I) by Differential Pulse Voltammetry Using a Glassy Carbon Electrode Modified with Synthesized N-(2-Aminoethyl)-4,4′-Bipyridine

    PubMed Central

    Radulescu, Maria-Cristina; Chira, Ana; Radulescu, Medeea; Bucur, Bogdan; Bucur, Madalina Petruta; Radu, Gabriel Lucian

    2010-01-01

    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. PMID:22163530

  12. Sensitive voltammetric sensor based on isopropanol-Nafion-PSS-GR nanocomposite modified glassy carbon electrode for determination of clenbuterol in pork.

    PubMed

    Wang, Ling; Yang, Ran; Chen, Jing; Li, Jianjun; Qu, Lingbo; de B Harrington, Peter

    2014-12-01

    In the present study, poly(sodium 4-styrenesulfonate) (PSS) functionalized graphene (GR) was synthesised via a simple one-step chemical reduction of exfoliated graphite oxides in the presence of PSS. Characterisation of as-made nanocomposite using Fourier transform infrared spectroscopy (FT-IR) and ultraviolet and visible spectroscopy (UV-vis) clearly demonstrate the successful attachment of PSS to graphene sheets. A novel clenbuterol (CLB) electrochemical sensor was fabricated based on isopropanol-Nafion-PSS-GR composite film modified glassy carbon electrode. In the Britton-Robinson buffer (pH 1.2), the sensor exhibited superior electrocatalytic activity towards the oxidation of CLB. Applying linear sweep voltammetry, a good linear relationship of the oxidation peak current with respect to concentrations of CLB cross the range of 7.5 × 10(-8)-2.5 × 10(-5)mol L(-1) and a detection limit of 2.2 × 10(-8) mol L(-1) were achieved. The proposed method was successfully applied for the determination of CLB in pork. PMID:24996313

  13. Determination of guanine and adenine by high-performance liquid chromatography with a self-fabricated wall-jet/thin-layer electrochemical detector at a glassy carbon electrode.

    PubMed

    Zhou, Yaping; Yan, Hongling; Xie, Qingji; Yao, Shouzhuo

    2015-03-01

    A sensitive wall-jet/thin-layer amperometric electrochemical detector (ECD) coupled to high-performance liquid chromatography (HPLC) was developed for simultaneous determination of guanine (G) and adenine (A). The analytes were detected at a glassy carbon electrode (GCE) and the HPLC-ECD calibration curves showed good linearity (R(2)>0.997) under optimized conditions. Limits of detection for G and A are 0.6 nM and 1.4 nM (S/N=3), respectively, which are lower than those obtained with an UV-vis detector and a commercial electrochemical detector. We have successfully applied this HPLC-ECD to assess the contents of G and A in hydrochloric acid-digested calf thymus double-stranded DNA. In addition, we compared in detail the analysis of G and A by cyclic voltammetry (CV) and by the HPLC-ECD system on both bare GCE and electroreduced graphene oxide (ERGO) modified GCE. We found that the adsorption of G and A on the electrode surfaces can vary their anodic CV peaks and the competitive adsorption of G and A on the limited sites of the electrode surfaces can cause crosstalk effects on their anodic CV peak signals, but the HPLC-ECD system is insensitive to such electrode-adsorption and can give more reliable analytical results. PMID:25618679

  14. Fuel blends: Enhanced electro-oxidation of formic acid in its blend with methanol at platinum nanoparticles modified glassy carbon electrodes

    NASA Astrophysics Data System (ADS)

    El-Deab, Mohamed S.; El-Nagar, Gumaa A.; Mohammad, Ahmad M.; El-Anadouli, Bahgat E.

    2015-07-01

    The current study addresses, for the first time, the enhanced direct electro-oxidation of formic acid (FA) at platinum-nanoparticles modified glassy carbon (nano-Pt/GC) electrode in the presence of methanol (MeOH) as a blending fuel. This enhancement is probed by: (i) the increase of the direct oxidation current of FA to CO2 (Ipd, dehydrogenation pathway), (ii) suppressing the dehydration pathway (Ipind, producing the poisoning intermediate CO) and (iii) a favorable negative shift of the onset potential of Ibd with increasing the mole fraction of MeOH in the blend. Furthermore, the charge of the direct FA oxidation in 0.3 M FA + 0.3 M MeOH blend is by 14 and 21times higher than that observed for 0.3 M FA and 0.3 M MeOH, respectively. MeOH is believed to adsorb at the Pt surface sites and thus disfavor the "non-faradaic" dissociation of FA (which produces the poisoning CO intermediate), i.e., MeOH induces a high CO tolerance of the Pt catalyst. The enhanced oxidation activity indicates that FA/MeOH blend is a promising fuel system.

  15. Design and evaluation of a highly sensitive nanostructure-based surface modification of glassy carbon electrode for electrochemical studies of hydroxychloroquine in the presence of acetaminophen.

    PubMed

    Khoobi, Asma; Ghoreishi, Sayed Mehdi; Behpour, Mohsen; Shaterian, Maryam; Salavati-Niasari, Masoud

    2014-11-01

    N,N'-bis[(E)-(1-pyridyl) methylidene]-1,3-propanediamine (PMPDA) self-assembled monolayer (SAM) was covalently prepared on a glassy carbon electrode (GCE). The electrode surface modification was characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. Then GC-PMPDA SAM modified electrode was used to investigate the electrochemical behavior of hydroxychloroquine (HQ) using CV, double potential step chronocoulometry and linear sweep voltammetry (LSV) techniques. Using these techniques, the diffusion coefficient (D), electron transfer coefficient (α) and exchanging current density (j0) for HQ were calculated. Furthermore the modified electrode was applied as a high sensitive biosensor for determination of HQ in the presence of acetaminophen (AC). The GC-PMPDA SAM modified electrode provides two linear responses for HQ in the presence of AC in the concentration ranges from 0.09 to 10.21 μM and 10.21 to 98.29 μM by differential pulse voltammetry (DPV). The detection limit (three times the signal blank/slope) was 4.65 nM. Finally the modified electrode was satisfactorily used for determining of HQ in human body fluids. PMID:25456984

  16. Electrochemical DNA biosensor based on poly(2,6-pyridinedicarboxylic acid) modified glassy carbon electrode for the determination of anticancer drug gemcitabine.

    PubMed

    Tığ, Gözde Aydoğdu; Zeybek, Bülent; Pekyardımcı, Şule

    2016-07-01

    In this study, a simple methodology was used to develop a new electrochemical DNA biosensor based on poly(2,6-pyridinedicarboxylic acid) (P(PDCA)) modified glassy carbon electrode (GCE). This modified electrode was used to monitor for the electrochemical interaction between the dsDNA and gemcitabine (GEM) for the first time. A decrease in oxidation signals of guanine after the interaction of the dsDNA with the GEM was used as an indicator for the selective determination of the GEM via differential pulse voltammetry (DPV). The guanine oxidation peak currents were linearly proportional to the concentrations of the GEM in the range of 1-30mgL(‒1). Limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.276mgL(‒1) and 0.922mgL(‒1), respectively. The reproducibility, repeatability, and applicability of the analysis to pharmaceutical dosage forms and human serum samples were also examined. In addition to DPV method, UV-vis and viscosity measurements were utilized to propose the interaction mechanism between the GEM and the dsDNA. The novel DNA biosensor could serve for sensitive, accurate and rapid determination of the GEM. PMID:27154680

  17. Nano-assemblies consisting of Pd/Pt nanodendrites and poly (diallyldimethylammonium chloride)-coated reduced graphene oxide on glassy carbon electrode for hydrogen peroxide sensors.

    PubMed

    Zhang, Yanyan; Zhang, Cong; Zhang, Di; Ma, Min; Wang, Weizhen; Chen, Qiang

    2016-01-01

    Non-enzymatic hydrogen peroxide (H2O2) sensors were fabricated on the basis of glassy carbon (GC) electrode modified with palladium (Pd) core-platinum (Pt) nanodendrites (Pt-NDs) and poly (diallyldimethylammonium chloride) (PDDA)-coated reduced graphene oxide (rGO). A facile wet-chemical method was developed for preparing Pd core-Pt nanodendrites. In this approach, the growth of Pt NDs was directed by Pd nanocrystal which could be regarded as seed. The PDDA-coated rGO could form uniform film on the surface of GC electrode, which provided a support for Pd core- Pt NDs adsorption by self-assembly. The morphologies of the nanocomposites were characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction (spectrum). Electrocatalytic ability of the nanocomposites was evaluated by cyclic voltammetry and chronoamperometric methods. The sensor fabricated by Pd core-Pt NDs/PDDA-rGO/GCE exhibited high sensitivity (672.753 μA mM(-1) cm(-2)), low detection limit (0.027 μM), wider linear range (0.005-0.5mM) and rapid response time (within 5s). Besides, it also exhibited superior reproducibility, excellent anti-interference performance and long-term stability. The present work could afford a viable method and efficient platform for fabricating all kinds of amperometric sensors and biosensors. PMID:26478428

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

    NASA Astrophysics Data System (ADS)

    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.

  19. Mercury(II) trace detection by a gold nanoparticle-modified glassy carbon electrode using square-wave anodic stripping voltammetry including a chloride desorption step.

    PubMed

    Laffont, Laure; Hezard, Teddy; Gros, Pierre; Heimbürger, Lars-Eric; Sonke, Jeroen E; Behra, Philippe; Evrard, David

    2015-08-15

    Gold nanoparticles (AuNPs) were deposited on a glassy carbon (GC) substrate by constant potential electrolysis and characterized by cyclic voltammetry in H2SO4 and field emission gun scanning electron microscopy (FEG-SEM). The modified AuNPs-GC electrode was used for low Hg(II) concentration detection using a Square Wave Anodic Stripping Voltammetry (SWASV) procedure which included a chloride desorption step. The comparison of the obtained results with our previous work in which no desorption step was used showed that this latter step significantly improved the analytical performances, providing a three time higher sensitivity and a limit of detection of 80pM for 300s preconcentration, as well as a lower average standard deviation. The influence of chloride concentration on the AuNPs-GC electrode response to Hg(II) trace amounts was also studied and its optimal value confirmed to be in the 10(-2)M range. Finally, the AuNPs-GC electrode was used for the determination of Hg(II) in a natural groundwater sample from south of France. By using a preconcentration time of 3000s, a Hg(II) concentration of 19±3pM was found, which compared well with the result obtained by cold vapor atomic fluorescence spectroscopy (22±2pM). PMID:25966376

  20. Electrodeposition From Acidic Solutions of Nickel Bis(benzenedithiolate) Produces a Hydrogen-Evolving Ni-S Film on Glassy Carbon

    SciTech Connect

    Fang, Ming; Engelhard, Mark H.; Zhu, Zihua; Helm, Monte L.; Roberts, John A.

    2014-01-03

    Films electrodeposited onto glassy carbon electrodes from acidic acetonitrile solutions of [Bu4N][Ni(bdt)2] (bdt = 1,2-benzenedithiolate) are active toward electrocatalytic hydrogen production at potentials 0.2-0.4 V positive of untreated electrodes. This activity is preserved on rinsing the electrode and transfer to fresh acid solution. X-ray photoelectron spectra indicate that the deposited material contains Ni and S. Correlations between voltammetric and spectroscopic results indicate that the deposited material is active, i.e. that catalysis is heterogeneous rather than homogeneous. Control experiments establish that obtaining the observed catalytic response requires both Ni and the 1,2 benzenedithiolate ligand to be present during deposition. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy. A portion of the research was performed using EMSL, a 17 national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory.

  1. Electrochemical determination of Sudan I in food samples at graphene modified glassy carbon electrode based on the enhancement effect of sodium dodecyl sulphonate.

    PubMed

    Ma, Xinying; Chao, Mingyong; Wang, Zhaoxia

    2013-06-01

    This paper describes a novel electrochemical method for the determination of Sudan I in food samples based on the electrochemical catalytic activity of graphene modified glassy carbon electrode (GMGCE) and the enhancement effect of an anionic surfactant: sodium dodecyl sulphonate (SDS). Using pH 6.0 phosphate buffer solution (PBS) as supporting electrolyte and in the presence of 1.5 × 10(-4)mol L(-1) SDS, Sudan I yielded a well-defined and sensitive oxidation peak at a GMGCE. The oxidation peak current of Sudan I remarkably increased in the presence of SDS. The experimental parameters, such as supporting electrolyte, concentration of SDS, and accumulation time, were optimised for Sudan I determination. The oxidation peak current showed a linear relationship with the concentrations of Sudan I in the range of 7.50 × 10(-8)-7.50 × 10(-6)mol L(-1), with the detection limit of 4.0 × 10(-8)mol L(-1). This new voltammetric method was successfully used to determine Sudan I in food products such as ketchup and chili sauce with satisfactory results. PMID:23411169

  2. High performance supercapacitor based on graphene-silver nanoparticles-polypyrrole nanocomposite coated on glassy carbon electrode

    NASA Astrophysics Data System (ADS)

    Kalambate, Pramod K.; Dar, Riyaz A.; Karna, Shashi P.; Srivastava, Ashwini K.

    2015-02-01

    In the current study, we present a new hybrid material of double layer capacitive material graphene (GNS), pseudo capacitive polypyrrole (PPY) and highly conducting silver nanoparticles (AgNPs). Graphene/Silver nanoparticles/polypyrrole (GNS/AgNPs/PPY) composite has been synthesized by in situ oxidative polymerization of pyrrole in the presence of GNS and AgNPs. The different mass concentrations of AgNPs were utilized to improve the capacitive performance of supercapacitor. Characterization of the electrode material has been carried out by X-ray diffraction, Raman spectroscopy, Thermal methods, Scanning electron microscopy (SEM) and Transmission electron microscopy. SEM images showed that PPY nanoparticles uniformly coated on graphene sheets along with AgNPs. Electrochemical characterization of the electrode surface has been carried out by means of cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. Remarkably, GNS/AgNPs/PPY exhibits specific capacitance of 450 F g-1 at current density of 0.9 mA g-1, which is far better than GNS/PPY (288 F g-1), AgNPs/PPY (216 F g-1) and PPY (153 F g-1). Furthermore, GNS/AgNPs/PPY shows high charge-discharge reversibility and retaining over 92.0% of its initial value after 1000 cycles. The cyclic stability of the composite is improved due to the synergistic effect of GNS, AgNPs and PPY.

  3. Removal of a mixture tetracycline-tylosin from water based on anodic oxidation on a glassy carbon electrode coupled to activated sludge.

    PubMed

    Yahiaoui, Idris; Aissani-Benissad, Farida; Fourcade, Florence; Amrane, Abdeltif

    2015-01-01

    The purpose of this study was first to examine the electrochemical oxidation of two antibiotics, tetracycline (TC) and tylosin (Tylo), considered separately or in mixture, on a glassy carbon electrode in aqueous solutions; and then to assess the relevance of such electrochemical process as a pre-treatment prior to a biological treatment (activated sludge) for the removal of these antibiotics. The influence of the working potential and the initial concentration of TC and Tylo on the electrochemical pre-treatment process was also investigated. It was noticed that antibiotics degradation was favoured at high potential (2.4 V/ saturated calomel electrode (SCE)), achieving total degradation after 50 min for TC and 40 min for Tylo for 50 mg L(-1) initial concentration, with a higher mineralization efficiency in the case of TC. The biological oxygen demand in 5 days (BOD5)/Chemical oxygen demand (COD) ratio increased substantially, from 0.033 to 0.39 and from 0.038 to 0.50 for TC and Tylo, respectively. Regarding the mixture (TC and Tylo), the mineralization yield increased from 10.6% to 30.0% within 60 min of reaction time when the potential increased from 1.5 to 2.4 V/SCE and the BOD5/COD ratio increased substantially from 0.010 initially to 0.29 after 6 h of electrochemical pre-treatment. A biological treatment was, therefore, performed aerobically during 30 days, leading to an overall decrease of 72% of the dissolved organic carbon by means of the combined process. PMID:25650749

  4. Gamma-rays initiated cationic polymerization of epoxy resins and their carbon nanotubes composites

    NASA Astrophysics Data System (ADS)

    Przybytniak, Grażyna; Nowicki, Andrzej; Mirkowski, Krzysztof; Stobiński, Leszek

    2016-04-01

    Epoxy resins based on diglycidyl ether of bisphenol A (DGEBA) in the presence cationic initiator in the form of iodonium salt were exposed to gamma-rays in order to initiate curing process. The influence of the initiator concentration, dose rate, chemical structure of monomers and the presence of carbon nanotubes were determined on the basis of the recorded on-line thermal effects. The induction time of radiation curing increased with lowering concentration of the initiator and oxirane groups as well as with decreasing dose rates. As was confirmed by SEM images, carbon nanotubes were uniformly distributed over the matrix and closely surrounded by the macromolecules. Such a structure resulted from adsorption of the initiator on the filler surface what allowed to begin polymerization around nanoparticles and facilitated their incorporation into the matrix. As a consequence, the mechanical properties of the nanocomposites were improved.

  5. Nanosheet Graphene Composite Carbon Aerogels from Resorcinol-Formaldehyde via an Adsorption-Assembly Polymerization Method .

    PubMed

    Qiu, Jielong; Zhang, Shuting; Mai, Jiawen; Wu, Fangjun; Liu, Wei

    2015-12-01

    An adsorption-assembly sol-gel polymerization between graphene oxide (GO) sheets and resorcinol-formaldehyde aqueous solution was investigated as a method to form graphene composite carbon aerogels (GCAs) with cross-linked nanosheet structure and a surface area as high as 489 m2/g. By adjusting the amount of GO and the catalyst of hexamethylenetetramine (HMTA) in the precursor mixture, aerogels with little drying shrinkage under ambient pressure condition could be obtained. Benefiting from the attendance of graphene oxide, the obtained GCAs showed a regular nanosheets structure with countless nano-size particles on the sheet surface, which is quite different from the conventional carbon aerogels. The electrochemical performance of the GCAs were evaluated, they displayed small internal resistance and outstanding electrochemical specific capacitance (131 F/g), as well as a stable cycle performance (no capacitance loss after 5000 cycles). PMID:26682394

  6. Organic carbon aerogels from the sol-gel polymerization of phenolic-furfural mixtures

    DOEpatents

    Pekala, Richard W.

    1998-04-28

    The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes .ltoreq.1000 .ANG., and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050.degree. C. to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors.

  7. Organic carbon aerogels from the sol-gel polymerization of phenolic-furfural mixtures

    DOEpatents

    Pekala, R.W.

    1998-04-28

    The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes {<=}1000 {angstrom}, and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050 C to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors. 8 figs.

  8. A nitrite biosensor based on co-immobilization of nitrite reductase and viologen-modified chitosan on a glassy carbon electrode.

    PubMed

    Quan, De; Shin, Woonsup

    2010-01-01

    An electrochemical nitrite biosensor based on co-immobilization of copper-containing nitrite reductase (Cu-NiR, from Rhodopseudomonas sphaeroides forma sp. denitrificans) and viologen-modified chitosan (CHIT-V) on a glassy carbon electrode (GCE) is presented. Electron transfer (ET) between a conventional GCE and immobilized Cu-NiR was mediated by the co-immobilized CHIT-V. Redox-active viologen was covalently linked to a chitosan backbone, and the thus produced CHIT-V was co-immobilized with Cu-NiR on the GCE surface by drop-coating of hydrophilic polyurethane (HPU). The electrode responded to nitrite with a limit of detection (LOD) of 40 nM (S/N = 3). The sensitivity, linear response range, and response time (t(90%)) were 14.9 nA/μM, 0.04-11 μM (r(2) = 0.999) and 15 s, respectively. The corresponding Lineweaver-Burk plot showed that the apparent Michaelis-Menten constant (K(M) (app)) was 65 μM. Storage stability of the biosensor (retaining 80% of initial activity) was 65 days under ambient air and room temperature storage conditions. Reproducibility of the sensor showed a relative standard deviation (RSD) of 2.8% (n = 5) for detection of 1 μM of nitrite. An interference study showed that anions commonly found in water samples such as chlorate, chloride, sulfate and sulfite did not interfere with the nitrite detection. However, nitrate interfered with a relative sensitivity of 64% and this interference effect was due to the intrinsic character of the NiR employed in this study. PMID:22219710

  9. Flexible electrochemical capacitors based on polypyrrole/carbon fibers via chemical polymerization of pyrrole vapor

    NASA Astrophysics Data System (ADS)

    Yuan, Wei; Han, Gaoyi; Xiao, Yaoming; Chang, Yunzhen; Liu, Cuixian; Li, Miaoyu; Li, Yanping; Zhang, Ying

    2016-07-01

    Polypyrrole (PPy) has been deposited on the carbon fibers (CFs) via chemical oxidation of monomer vapor strategy, during which FeCl3·6H2O in acetonitrile adsorbed on CFs acts as oxidant to polymerize the pyrrole vapor. The morphologies and capacitive properties of the PPy deposited on CFs (PPy/CFs) are strongly influenced by the concentration of oxidant used in the process. The assembled flexible capacitors by using PPy/CFs as electrodes and LiCl/polyvinyl alcohol as gel electrolyte have been evaluated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The results show that the composites of PPy/CFs prepared by using 350 mg mL-1 FeCl3·6H2O as oxidant (PPy/CFs-350) exhibit relatively higher specific capacitance and good rate capability. Compared with PPy/CFs prepared by electrochemical deposition (retaining 5% of the initial capacitance), the PPy/CFs prepared by chemically polymerizing monomer vapor shows excellent stability (retaining 85% of initial capacitance after 5000 cycles). Furthermore, cells fabricated by PPy/CFs show a fairly good performance under various bending states, three cells of PPy/CFs-350 connected in series can light up a light emitting diode with a voltage threshold of about 2.5 V for approximate 10 min after being charged for about 3 min, revealing the potential of the cells' practical applications.

  10. Amperometric Biosensor Based on Carbon Nanotube Functionalized by Redox Plasma-Polymerized Film

    NASA Astrophysics Data System (ADS)

    Hoshino, Tatsuya; Muguruma, Hitoshi

    2011-08-01

    A novel fabrication approach for the amperometric biosensor based on multilayer films containing carbon nanotubes (CNT), a plasma-polymerized film (PPF), and enzyme glucose oxidase (GOD) is reported. The configuration of the electrochemical electrode is sequentially composed of sputtered gold, lower acetonitrile PPF, CNT, redox PPF, GOD, and upper acetonitrile PPF (denoted as PPF/GOD/Redox-PPF/CNT/PPF/Au). The lower acetonitrile PPF deposited on Au acts as a permselective membrane, and as a scaffold for CNT layer formation. The upper acetonirile PPF directly deposited on GOD acts as a matrix for enzyme immobilization. The redox PPF polymerized by a monomer of dimethlyaminomethlyferrocene (DAF) is directly deposited onto CNTs. The surface of the functionalized CNT has redox sites of ferrocene groups that shuttle electrons from CNTs to the sensing surface of the Au electrode. The synergy between the redox PPF and CNT provides benefits in terms of lowering the operational potential and enhancing the sensitivity (current). The optimized glucose biosensor revealed a sensitivity of 2.0 µA mM-1 cm-2 at +0.4 V vs Ag/AgCl, a linear dynamic range of 4.9-27 mM, and a response time of 5 s.

  11. Two photon polymerization lithography for 3D microfabrication of single wall carbon nanotube/polymer composites

    NASA Astrophysics Data System (ADS)

    Ushiba, Shota; Shoji, Satoru; Kuray, Preeya; Masui, Kyoko; Kono, Junichiro; Kawata, Satoshi

    2013-03-01

    Two photon polymerization (TPP) lithography has been established as a powerful tool to develop 3D fine structures of polymer materials, opening up a wide range applications such as micro-electromechanical systems (MEMS). TPP lithography is also promising for 3D micro fabrication of nanocomposites embedded with nanomaterials such as metal nanoparticles. Here, we make use of TPP lithography to fabricate 3D micro structural single wall carbon nanotube (SWCNT)/polymer composites. SWCNTs exhibit remarkable mechanical, electrical, thermal and optical properties, which leads to enhance performances of polymers by loading SWCNTs. SWCNTs were uniformly dispersed in an acrylate UV-curable monomer including a few amounts of photo-initiator and photo-sensitizer. A femtosecond pulsed laser emitting at 780 nm was focused onto the resin, resulting in the photo-polymerization of a nanometric volume of the resin through TPP. By scanning the focus spot three dimensionally, arbitrary 3D structures were created. The spatial resolution of the fabrication was sub-micrometer, and SWCNTs were embedded in the sub-micro sized structures. The fabrication technique enables one to fabricate 3D micro structural SWCNT/polymer composites into desired shapes, and thus the technique should open up the further applications of SWCNT/polymer composites such as micro sized photomechanical actuators.

  12. Effects of minor components in carbon dioxide capture using polymeric gas separation membranes

    SciTech Connect

    Scholes, C.; Kentish, S.; Stevens, G.

    2009-07-01

    The capture of carbon dioxide by membrane gas separation has been identified as one potential solution to reduce greenhouse gas emissions. In particular, the application of membranes to CO{sub 2} capture from both pre- and post-combustion strategies is of interest. For membrane technology to become commercially viable in CO{sub 2} capture, a number of factors need to be overcome, one being the role of minor components in the process on membrane performance. This review considers the effects of minor components in both pre- and post-combustion use of polymeric membranes for CO{sub 2} capture. In particular, gases such as SOx, NOx, CO, H{sub 2}S, NH3, as well as condensable water and hydrocarbons are reviewed in terms of their permeability through polymeric membranes relative to CO{sub 2}, as well as their plasticization and aging effects on membrane separation performance. A major conclusion of the review is that while many minor components can affect performance both through competitive sorption and plasticization, much remains unknown. This limits the selection process for membranes in this application.

  13. 2-chlorophenol sorption from aqueous solution using granular activated carbon and polymeric adsorbents

    NASA Astrophysics Data System (ADS)

    Ghatbandhe, A. S.; Jahagirdar, H. G.; Yenkie, M. K. N.; Deosarkar, S. D.

    2013-08-01

    Adsorption equilibrium and kinetics of 2-chlorophenol (2-CP) one of the chlorophenols (CPs) onto bituminous coal based Filtrasorb-400 grade granular activated carbon and three different types of polymeric adsorbents were studied in aqueous solution in a batch system. Langmuir isotherm models were applied to experimental equilibrium data of 2-CP adsorption. Equilibrium data fitted very well to the Langmuir equilibrium models of 2-CP. Adsorbent monolayer capacity Q Langmuir constant b and adsorption rate constants k a were evaluated. 2-CP adsorption using GAC is very rapid in the first hour of contact where 70-80% of the adsorbate is removed by GAC followed by a slow approach to equilibrium. Whereas in case of polymeric adsorbents 60-65% of the adsorbate is removed in the first 30 min which is then followed by a slow approach to equilibrium. The order of adsorption of 2-CP on different adsorbents used in the study is found to be in following order: F-400 > XAD-1180 > XAD-4 > XAD-7HP.

  14. A Simple and Facile Approach to Aliphatic N-Substituted Functional Eight-Membered Cyclic Carbonates and Their Organocatalytic Polymerization.

    PubMed

    Venkataraman, Shrinivas; Ng, Victor W L; Coady, Daniel J; Horn, Hans W; Jones, Gavin O; Fung, Tak Shun; Sardon, Haritz; Waymouth, Robert M; Hedrick, James L; Yang, Yi Yan

    2015-11-01

    Aliphatic N-substituted functional eight-membered cyclic carbonates were synthesized from N-substituted diethanolamines by intramolecular cyclization. On the basis of the N-substituent, three major subclasses of carbonate monomers were synthesized (N-aryl, N-alkyl and N-carbamate). Organocatalytic ring opening polymerization (ROP) of eight-membered cyclic carbonates was explored as a route to access narrowly dispersed polymers of predictable molecular weights. Polymerization kinetics was highly dependent on the substituent on the nitrogen atom and the catalyst used for the reaction. The use of triazabicyclodecene (TBD), instead of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), as the catalyst for the N-alkyl substituted monomers significantly enhanced the rate of polymerizations. Computational studies were performed to rationalize the observed trends for TBD catalyzed polymerizations. With the optimal organocatalyst all monomers could be polymerized generating well-defined polymers within a timespan of ≤2 h with relatively high monomer conversion (≥80%) and low molar-mass dispersity (Đ(M) ≤ 1.3). Both the glass transition temperatures (T(g)) and onset of degradation temperatures (T(onset)) of these polymers were found to be N-substituent dependent and were in the range of about -45 to 35 °C and 230 to 333 °C, respectively. The copolymerization of the eight membered monomers with 6-membered cyclic comonomers including commercially available l-lactide and trimethylene carbonate produced novel copolymers. The combination of inexpensive starting materials, ease of ring-closure and subsequent polymerization makes this an attractive route to functional polycarbontes. PMID:26456146

  15. A facile method to align carbon nanotubes on polymeric membrane substrate

    PubMed Central

    Zhao, Haiyang; Zhou, Zhijun; Dong, Hang; Zhang, Lin; Chen, Huanlin; Hou, Lian

    2013-01-01

    The alignment of carbon nanotubes (CNT) is the fundamental requirement to ensure their excellent functions but seems to be desolated in recent years. A facile method, hot-press combined with peel-off (HPPO), is introduced here, through which CNT can be successfully vertically aligned on the polymeric membrane substrate. Shear force and mechanical stretch are proposed to be the main forces to align the tubes perpendicular to the substrate surface during the peel-off process. The alignment of CNT keeps its orientation in a thin hybrid membrane by dip-coating cellulose acetate dope solution. It is expected that the stable alignment of CNT by HPPO would contribute to the realization of its potential applications. PMID:24326297

  16. A polymeric nanocoating on carbon nanotube arrays for developing imprinted protein sensor

    NASA Astrophysics Data System (ADS)

    Ren, L.; Zhao, H. Z.; Xu, C. J.; Yu, Y.; Wang, H. Z.; Lan, Y. C.; Wagner, D.; Naughton, M. J.; Ren, Z. F.; Chiles, T. C.; Cai, D.

    2010-03-01

    Polyphenol (PPn) was electrodeposited on carbon nanotubes (CNT) arrays at nanoscale thickness. PPn is a non-conductive polymer, so increase of sensor impedance was observed with high density CNT array, low density CNT array, and tip-polished CNT array (tCNTA), while tCNTA was determined to be the best nanosensor platform to incorporate the imprinted PPn coating due to the highest impedance increase. The PPn was characterized by transmission electron microscopy, electrochemical impedance spectroscopy and cyclic voltammetry for its thickness, uniformity, stability, resistivity and permittivity etc., as well as the protein entrapment and removal process. The density of the imprint was also evaluated by a PPn refilling experiment. Finally, ferritin was used as the template to develop a highly sensitive and selective protein nanosensor. Therefore, a novel strategy was demonstrated here to deposit and characterize polymeric nanocoating, also to evaluate imprints and detect proteins.

  17. A facile method to align carbon nanotubes on polymeric membrane substrate

    NASA Astrophysics Data System (ADS)

    Zhao, Haiyang; Zhou, Zhijun; Dong, Hang; Zhang, Lin; Chen, Huanlin; Hou, Lian

    2013-12-01

    The alignment of carbon nanotubes (CNT) is the fundamental requirement to ensure their excellent functions but seems to be desolated in recent years. A facile method, hot-press combined with peel-off (HPPO), is introduced here, through which CNT can be successfully vertically aligned on the polymeric membrane substrate. Shear force and mechanical stretch are proposed to be the main forces to align the tubes perpendicular to the substrate surface during the peel-off process. The alignment of CNT keeps its orientation in a thin hybrid membrane by dip-coating cellulose acetate dope solution. It is expected that the stable alignment of CNT by HPPO would contribute to the realization of its potential applications.

  18. Diacetylenes with Ionic-Liquid-Like Substituents: Associating a Polymerizing Cation with a Polymerizing Anion in a Single Precursor for the Synthesis of N-Doped Carbon Materials.

    PubMed

    Fahsi, Karim; Dumail, Xavier; Dutremez, Sylvain G; van der Lee, Arie; Vioux, André; Viau, Lydie

    2016-01-26

    Imidazolium- and benzimidazolium-substituted diacetylenes with bromide or nitrogen-rich dicyanamide and tricyanomethanide anions were synthesized and used as precursors for the preparation of N-doped carbon materials. On pyrolysis under argon at 800 °C both halide precursors afforded graphite-like structures with nitrogen contents of about 8.5%. When the dicyanamide and tricyanomethanide precursors were thermolyzed at the same temperature, graphite-like structures were obtained that exhibit nitrogen contents in the range 17-20 wt%; thereby, the benefit of associating a polymerizing cation with a polymerizing anion in a single precursor was demonstrated. On pyrolysis at 1100 °C the nitrogen contents of the latter pyrolysates remain high (ca. 6 wt%). Adsorption measurements with krypton at 77 K indicated that the materials are nonporous. The highest electrical conductivity was observed for a pyrolysate with one of the lowest nitrogen contents, which also has the highest degree of graphitization. Thus, the quest for N-rich carbons with high electrical conductivities should include both maximization of the nitrogen content and optimization of the degree of graphitization. Crystallographic investigation of the precursors and spectroscopic characterization of the pyrolysates prepared by heating at 220 °C indicate that construction of the final carbon framework does not involve the intermediate formation of a polydiacetylene. PMID:26695842

  19. Evidence of double layer/capacitive charging in carbon nanomaterial-based solid contact polymeric ion-selective electrodes.

    PubMed

    Cuartero, Maria; Bishop, Josiah; Walker, Raymart; Acres, Robert G; Bakker, Eric; De Marco, Roland; Crespo, Gaston A

    2016-08-11

    This paper presents the first direct spectroscopic evidence for double layer or capacitive charging of carbon nanomaterial-based solid contacts in all-solid-state polymeric ion-selective electrodes (ISEs). Here, we used synchrotron radiation-X-ray photoelectron spectroscopy (SR-XPS) and SR valence band (VB) spectroscopy in the elucidation of the charging mechanism of the SCs. PMID:27405722

  20. Lewis acid catalyzed ring-opening polymerization of natural epoxy oil (Euphorbia oil) in carbon dioxide media

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In an attempt to build up useful application of plant oil based polymers, natural epoxy oil (euphorbia oil-EuO) was polymerized in liquid carbon dioxide in the presence of Lewis acid catalyst [Boron trifluoride diethyl etherate (BF3•OEt2)]. The resulting polymers (RPEuO) were characterized by FTIR ...

  1. Pressure-induced polymerization of carbon monoxide: disproportionation and synthesis of an energetic lactonic polymer

    SciTech Connect

    Evans, W J; Lipp, M J; Yoo, C; Herberg, J L; Maxwell, R S; Nicol, M F

    2005-10-04

    We have studied pressure-induced chemical reactions in carbon monoxide using both a diamond-anvil cell and a modified large volume press. Our spectroscopic data reveal that carbon monoxide disproportionates into molecular CO{sub 2} and a solid lactone-type polymer; photochemically above 3.2 GPa, thermochemically above 5 GPa at 300K, or at 3 GPa and {approx}2000K as achieved by laser heating. The solid product can be recovered at ambient conditions with a high degree of conversion, measured to be up to 95% of the original CO. Its fundamental chemical structure includes {beta}-lactone and conjugated C=C, which can be considered a severely modified polymeric carbon suboxide with open ladders and smaller five-membered rings. The polymer is metastable at ambient conditions, spontaneously liberating CO{sub 2} gases exothermically. We find that the recovered polymer has a high energy density, 1-8 KJ/g, and is very combustible. We estimate the density of recovered CO polymer to be at least 1.65 g/cm cm{sup 3}.

  2. Polymeric forms of carbon in dense Li2C2: from zigzag chains to cubic gauche network

    SciTech Connect

    Chen, Xingqiu; Fu, Chong Long; Franchini, C.

    2010-01-01

    Although various allotropes of carbon (e.g., diamond, nanotubes, graphene, etc.) are among the best known materials, it remains challenging to stabilize carbon in the one-dimensional form because of the difficulty to suitably saturate the dangling bonds of carbon. Here, we show through first- principles calculations that ordered polymeric carbon chains can be stabilized in solid Li2C2 under pressure. This pressure-induced phase (above 5 GPa), consisting of parallel arrays of twofold zigzag carbon chains embedded in the lithium cages, is found to be metallic, as this phase is stabilized by the presence of partially occupied carbon lone-pair states in sp2 like hybrids. With the increasing stability of near-tetrahedral sp3-like hybrids at higher pressures, an insulating cubic phase with the single-bonded threefold-coordinated carbon network is formed above 215 GPa.

  3. Hydrodynamic voltammetry at tubular electrodes-III Determination of traces of bismuth by differential-pulse anodic-stripping voltammetry at a glassy-carbon tubular electrode with in situ mercury plating.

    PubMed

    Zhen, W; Qiang, C

    1987-07-01

    An equation for the current in differential-pulse anodic-stripping voltammetry at tubular electrodes is derived. Application of a glassy-carbon tubular electrode to determination of traces of bismuth in environmental water samples by differential-pulse anodic-stripping voltammetry is described. In hydrochloric acid medium, the stripping peak current is proportional to the concentration of bismuth in the range 2-100 ng/ml, with a deposition time of 3-10 min. The detection limit is 0.5 ng/ml. PMID:18964381

  4. Polymeric graphitic carbon nitride as a heterogeneous organocatalyst: from photochemistry to multipurpose catalysis to sustainable chemistry.

    PubMed

    Wang, Yong; Wang, Xinchen; Antonietti, Markus

    2012-01-01

    Polymeric graphitic carbon nitride materials (for simplicity: g-C(3)N(4)) have attracted much attention in recent years because of their similarity to graphene. They are composed of C, N, and some minor H content only. In contrast to graphenes, g-C(3)N(4) is a medium-bandgap semiconductor and in that role an effective photocatalyst and chemical catalyst for a broad variety of reactions. In this Review, we describe the "polymer chemistry" of this structure, how band positions and bandgap can be varied by doping and copolymerization, and how the organic solid can be textured to make it an effective heterogenous catalyst. g-C(3)N(4) and its modifications have a high thermal and chemical stability and can catalyze a number of "dream reactions", such as photochemical splitting of water, mild and selective oxidation reactions, and--as a coactive catalytic support--superactive hydrogenation reactions. As carbon nitride is metal-free as such, it also tolerates functional groups and is therefore suited for multipurpose applications in biomass conversion and sustainable chemistry. PMID:22109976

  5. Ring-opening graft polymerization of propylene carbonate onto xylan in an ionic liquid.

    PubMed

    Zhang, Xueqin; Chen, Mingjie; Liu, Chuanfu; Zhang, Aiping; Sun, Runcang

    2015-01-01

    The amidine organocatalyst 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) is an effective nucleophilic catalyst. Biocomposites with tuneable properties were successfully synthesized by ring-opening graft polymerization (ROGP) of propylene carbonate (PC) onto xylan using DBU as a catalyst in the ionic liquid (IL) 1-allyl-3-methylimidazolium chloride ([Amim]Cl). The effects of reaction temperature, reaction time and the molar ratio of PC to anhydroxylose units (AXU) in xylan were investigated. The physico-chemical properties of xylan-graft-poly(propylene carbonate) (xylan-g-PPC) copolymers were characterised by FT-IR, NMR, TGA/DTG, AFM and tensile analysis. The FT-IR and NMR results indicated the successful attachment of PPC onto xylan. TGA/DTG suggested the increased thermal stability of xylan after the attachment of PPC side chains. AFM analysis revealed details about the molecular aggregation of xylan-g-PPC films. The results also showed that with the increased DS of xylan-g-PPC copolymers, the tensile strength and Young's modulus of the films decreased, while the elongation at break increased. PMID:25853319

  6. 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.

    PubMed

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

    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 0.1mol/dm(3) phosphate buffer (PBS) solution of pH7.0. 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. PMID:26952453

  7. Electrochemically selective determination of dopamine in the presence of ascorbic and uric acids on the surface of the modified Nafion/single wall carbon nanotube/poly(3-methylthiophene) glassy carbon electrodes.

    PubMed

    Quan, Do Phuc; Tuyen, Do Phuc; Lam, Tran Dai; Tram, Phan Thi Ngoc; Binh, Nguyen Hai; Viet, Pham Hung

    2011-12-01

    A voltammetric method based on a combination of incorporated Nafion, single-walled carbon nanotubes and poly(3-methylthiophene) film-modified glassy carbon electrode (NF/SWCNT/PMT/GCE) has been successfully developed for selective determination of dopamine (DA) in the ternary mixture of dopamine, ascorbic acid (AA) and uric acid (UA) in 0.1M phosphate buffer solution (PBS) pH 4. It was shown that to detect DA from binary DA-AA mixture, the use of NF/PMT/GCE was sufficient, but to detect DA from ternary DA-AA-UA mixture NF/SWCNT/PMT/GCE was required. The later modified electrode exhibits superior electrocatalytic activity towards AA, DA and UA thanks to synergic effect of NF/SWCNT (combining unique properties of SWCNT such as high specific surface area, electrocatalytic and adsorptive properties, with the cation selectivity of NF). On the surface of NF/SWCNT/PMT/GCE AA, DA, UA were oxidized respectively at distinguishable potentials of 0.15, 0.37 and 0.53 V (vs. Ag/AgCl), to form well-defined and sharp peaks, making possible simultaneous determination of each compound. Also, it has several advantages, such as simple preparation method, high sensitivity, low detection limit and excellent reproducibility. Thus, the proposed NF/SWCNT/PMT/GCE could be advantageously employed for the determination of DA in real pharmaceutical formulations. PMID:21907551

  8. Indirect determination of sulfite using a polyphenol oxidase biosensor based on a glassy carbon electrode modified with multi-walled carbon nanotubes and gold nanoparticles within a poly(allylamine hydrochloride) film.

    PubMed

    Sartori, Elen Romão; Vicentini, Fernando Campanhã; Fatibello-Filho, Orlando

    2011-12-15

    The modification of a glassy carbon electrode with multi-walled carbon nanotubes and gold nanoparticles within a poly(allylamine hydrochloride) film for the development of a biosensor is proposed. This approach provides an efficient method used to immobilize polyphenol oxidase (PPO) obtained from the crude extract of sweet potato (Ipomoea batatas (L.) Lam.). The principle of the analytical method is based on the inhibitory effect of sulfite on the activity of PPO, in the reduction reaction of o-quinone to catechol and/or the reaction of o-quinone with sulfite. Under the optimum experimental conditions using the differential pulse voltammetry technique, the analytical curve obtained was linear in the concentration of sulfite in the range from 0.5 to 22 μmol L(-1) with a detection limit of 0.4 μmol L(-1). The biosensor was applied for the determination of sulfite in white and red wine samples with results in close agreement with those results obtained using a reference iodometric method (at a 95% confidence level). PMID:22099673

  9. Protein/ionic liquid/glassy carbon sensors following analyte focusing by ionic liquid micelle collapse for simultaneous determination of water soluble vitamins in plasma matrices.

    PubMed

    Abd El-Hady, D; Albishri, H M

    2015-07-01

    Two novel sensors based on human serum albumin (HSA)-ionic liquid (IL) and bovine serum albumin (BSA)-ionic liquid (IL) composites modified glassy carbon electrode (GCE) were produced for simultaneous determination of water soluble vitamins B2, B6 and C in human plasma following analytes focusing by IL micelles collapse (AFILMC). For selective and efficient extraction, vitamins were dissolved in 3.0molL(-1) micellar solution of 1-octyl-3-methyl imidazolium bromide IL. The extracted vitamins were hydrodynamically injected by 25mbar for 20s into a running buffer of 12.5mmolL(-1) phosphate at pH 6.0 followed by electrochemical detection (ECD) on protein/1-octyl-3-methyl imidazolium hexafluorophosphate IL/GC sensors. The chemical stability of proposed sensors was achieved up to 7 days without any decomposition of PF6-based IL/protein and adsorption of interfering ions. In the current work, the sensitivity enhancement factor (SEF) up to 5000-fold was achieved using the AFILMC/ECD setup compared to conventional CE/UV. Under optimal conditions, linear calibration graphs were obtained from 0.5, 0.5 and 1.0 to 1500.0µgmL(-1) of vitamins B2, B6 and C, respectively. Detection limits of analytes were ranged from 180.0 to 520.0ngmL(-1). The proposed AFILMC/ECD setup was successfully applied to the assay of trace level quantification of vitamins in human plasma samples and also their binding constants with HSA and BSA were determined. The concurrent use of IL micelles for the proposed separation and detection processes exhibited some advantages, such as, a reduction of use toxic solvents, an efficient extraction and a direct injection of samples with a short-single run. Furthermore, IL micelles, having variable possibility of interactions, facilitated the successful achievements of AFILMC/ECD setup for the quantification of vitamins in plasma matrices. PMID:25882421

  10. Condensed tannin biosynthesis and polymerization synergistically condition carbon use, defense, sink strength and growth in Populus.

    PubMed

    Harding, Scott A; Xue, Liang-Jiao; Du, Lei; Nyamdari, Batbayar; Lindroth, Richard L; Sykes, Robert; Davis, Mark F; Tsai, Chung-Jui

    2014-11-01

    The partitioning of carbon for growth, storage and constitutive chemical defenses is widely framed in terms of a hypothetical sink-source differential that varies with nutrient supply. According to this framework, phenolics accrual is passive and occurs in source leaves when normal sink growth is not sustainable due to a nutrient limitation. In assessing this framework, we present gene and metabolite evidence that condensed tannin (CT) accrual is strongest in sink leaves and sequesters carbon in a way that impinges upon foliar sink strength and upon phenolic glycoside (PG) accrual in Populus. The work was based on two Populus fremontii × angustifolia backcross lines with contrasting rates of CT accrual and growth, and equally large foliar PG reserves. However, foliar PG accrual was developmentally delayed in the high-CT, slow-growth line (SG), and nitrogen-limitation led to increased foliar PG accrual only in the low-CT, fast-growth line (FG). Metabolite profiling of developing leaves indicated comparatively carbon-limited amino acid metabolism, depletion of several Krebs cycle intermediates and reduced organ sink strength in SG. Gene profiling indicated that CT synthesis decreased as leaves expanded and PGs increased. A most striking finding was that the nitrogenous monoamine phenylethylamine accumulated only in leaves of SG plants. The potential negative impact of CT hyper-accumulation on foliar sink strength, as well as a mechanism for phenylethylamine involvement in CT polymerization in Populus are discussed. Starch accrual in source leaves and CT accrual in sink leaves of SG may both contribute to the maintenance of a slow-growth phenotype suited to survival in nutrient-poor habitats. PMID:24336515