| 1. |
- Otrokhov, Grigory, et al.
(författare)
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Enzymatic synthesis of polyaniline/multi-walled carbon nanotube composite with core shell structure and its electrochemical characterization for supercapacitor application
- 2014
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Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 123, s. 151-157
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Tidskriftsartikel (refereegranskat)abstract
- A new method involving laccase-mediator system has been developed for environmentally friendly synthesis of polyaniline/multi-walled carbon nanotubes (PANI/MWCNT) composite. Fungal laccase, potassium octocyanomolibdate (4+) and atmospheric oxygen served as catalyst, redox-mediator and terminal oxidant, respectively. The structure, morphology and electrical conductivity of composites with different PANI content were investigated. The energy storage of enzymatically obtained composite consists of an electrical double layer capacitance as well as pseudocapacitance of conducting polymer. The obtained PANI/MWCNT composite with PANI content ca. 49 wt.% had high specific capacitance and cycle stability during doping/dedoping. The specific capacitance of this composite measured by cyclic voltammetry technique with potential scan rate of 5 mV/s was ca. 440 F/g. The specific capacitance of the composite decreased by less than 7% of its maximum value after 1000 scan cycles between -0.1 and 0.7 V. Supercapacitor (SC) shell was made from flexible adhesive tape (regular Scotch tape) and current collector was formed after its separation from the surface of graphite foil. The ethanol dispersion of PANI/MWCNT composite was deposited on the current collector surface. The gel polymer electrolyte (polyvinyl alcohol in 1 M phosphoric acid) was employed as both electrolyte medium and separator. The energy and power densities under an operating window of 0.7 V were ca. 7.03 Wh/kg and 5.2 kW/kg, respectively. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.
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| 2. |
- Pankratov, Dmitry, et al.
(författare)
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A comparative study of biocathodes based on multiwall carbon nanotube buckypapers modified with three different multicopper oxidases
- 2013
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Ingår i: Electroanalysis. - : Wiley-VCH Verlagsgesellschaft. - 1040-0397 .- 1521-4109. ; 25:5, s. 1143-1149
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Tidskriftsartikel (refereegranskat)abstract
- 14 Single- and multi-walled carbon nanotubes from different sources were characterized in detail, and the characteristics obtained were carefully analyzed. The carbon material with the highest capacitance, and also other superior properties ("Taunit-M" from "NanoTechCenter", Russia), was chosen for further modification and fabrication of buckypaper based electrodes. These electrodes were biomodified with plant and fungal laccases, as well as fungal bilirubin oxidase. The designed biocathodes were studied in simple buffers and also in a complex physiol. fluid (human serum). Biocathodes based on immobilized fungal laccase were bioelectrocatalytically inactive in chloride contg. media at neutral pH. In spite of the quite high current densities realized using biodevices based on plant laccase and fungal bilirubin oxidase, the limited thermal stability of the enzymes renders the biocathodes inadequate for practical applications in implanted situations.
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| 3. |
- Shleev, Sergey, et al.
(författare)
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Interaction of fungal laccases and laccase-mediator systems with lignin
- 2006
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Ingår i: Enzyme and Microbial Technology. - : Elsevier BV. - 0141-0229 .- 1879-0909. ; 39:4, s. 841-847
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Tidskriftsartikel (refereegranskat)abstract
- The interaction between fungal laccases from Trametes basidiomycetes and different lignins has been studied using electrochemical and chromatographic methods. The kinetic parameters for the oxidation reaction of hydroquinone and for Kraft lignin by molecular oxygen catalysed by Trametes hirsuta laccase have been investigated. Polymerisation of lignin by laccase was shown. The process was independent on the source of lignin as well as on the origin and purity of the enzymes. A complex pattern of interaction between the laccase-mediator system (LMS) and lignin was shown. Along with the polymerisation of lignin, the ability to degrade lignin using the LMS was observed. Data generated by combining size exclusion chromatographic separation of lignin with the use of a laccase modified electrode as post column detector, strongly suggest that laccase can oxidise natural lignin by a long-range electron transfer mechanism. The influence of the origin of lignin as well as source of the enzyme on this process was also shown. (c) 2006 Elsevier Inc. All rights reserved.
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| 4. |
- Shleev, Sergey, et al.
(författare)
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Laccase-based biosensors for monitoring lignin
- 2006
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Ingår i: Enzyme and Microbial Technology. - : Elsevier BV. - 0141-0229. ; 39:4, s. 835-840
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Tidskriftsartikel (refereegranskat)abstract
- Four different ways to detect Kraft and soluble pine lignin using either soluble or immobilised Trametes hirsuta laccase have been investigated. In the first, the concentration of lignin was measured using laccase in homogeneous medium with a Clark electrode. In the second, laccase immobilised onto aminated porous glass beads was used in a reactor submerged into the lignin containing solution and the reaction was followed with a Clark electrode. The third and fourth techniques involved lignin detection using laccase modified spectrographic graphite electrodes, either used in flow injection mode or in batch mode, where lignin solutions were injected into an electrochemical cell. It was shown that the use of laccase modified graphite electrodes in conjunction with flow injection for amperometric lignin detection is an attractive perspective and our data form the basis for designing laccase-based biosensors to be applied for measuring lignin and its model compounds in waste water, e.g. from the pulp and paper industry. (c) 2006 Elsevier Inc. All rights reserved.
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| 5. |
- Shleev, Sergey, et al.
(författare)
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Stable floating air diffusion biocathode based on direct electron transfer reactions between carbon particles and high redox potential laccase
- 2010
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Ingår i: Fuel Cells. - : Wiley-VCH Verlag GmbH & Co. KGaA. - 1615-6846 .- 1615-6854. ; 10:4, s. 726-733
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Tidskriftsartikel (refereegranskat)abstract
- We report on the assembly and characterisation of a high potential, stable, mediator-less and cofactor free biocathode based on a fungal laccase (Lc), adsorbed on highly dispersed carbonaceous materials. First, the stability and activity of Trametes hirsuta Lc immobilised on different carbon particles were studied and compared to the solubilised enzyme. Based on the experimental results and a literature analysis, the carbonaceous material BM-4 was chosen to design efficient and stable biocatalysts for the production of a ‘floating’ air diffusion Lc-based biocathode. Voltammetric characteristics and operational stability of the biocathode were investigated. The current density of oxygen reduction at the motionless biocathode in a quiet, air saturated citrate buffer (100 mM, pH 4.5, 23 °C) reached values as high as 0.3 mA cm–2 already at 0.7 V versus NHE. The operational stability of the biocathode depended on the current density of the device. For example, at low current density (20 lA cm–2), the biocathode lost only 5× of its initial power after 1 month of continuous operation. However, when the device was polarised at 150 mV it lost more than 32× of its initial power in just 10 min. We also found that co-immobilisation of Lc and peroxidase on highly dispersed carbon materials could protect the biocatalyst from rapid inactivation by hydrogen peroxide produced during electrocatalytic reactions at high-current densities.
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