| 1. |
- Bencsik, G., et al.
(författare)
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Conducting polymer based multifunctional composite electrodes
- 2009
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Ingår i: Reaction Kinetics and Catalysis Letters. - : Springer. - 0133-1736 .- 1588-2837. ; 96, s. 421-428
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we report a novel pattern of composite electrocatalysts. PPy/iron-oxalate films exhibit photo-electrochemical activity. The PPy/B12 composite electrode on stainless steal (SS) support shows high catalytic activity in the electrochemical reduction of methylviologen. Thin polymer layers filled with magnetite particles can be applicable in magneto-selective electrochemical reactions.In this paper, we report a novel pattern of composite electrocatalysts. PPy/iron-oxalate films exhibit photo-electrochemical activity. The PPy/B12 composite electrode on stainless steal (SS) support shows high catalytic activity in the electrochemical reduction of methylviologen. Thin polymer layers filled with magnetite particles can be applicable in magneto-selective electrochemical reactions.
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| 2. |
- Endrődi, Balázs, 1987-, et al.
(författare)
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Electrochemical synthesis and characterization of poly(3-hexylthiophene)/single-walled carbon nanotube array hybrid materials
- 2016
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Ingår i: Journal of Solid State Electrochemistry. - : Springer. - 1432-8488 .- 1433-0768. ; 20:11, s. 3179-3187
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we demonstrate that by directly employing single-walled carbon nanotube arrays (SWCNT-arrays)-grown on conductive substrates-as working electrodes, selective and uniform electrodeposition of a conducting polymer, namely poly(3-hexylthiophene), can be achieved on the surface of the nanotubes. The overall kinetic pattern of the electrodeposition was studied by separating the deposition charge from the one related to the redox transformation of the polymer film deposited during the precedent cycles. Both the structure and the electrochemical properties of the hybrid materials were studied as a function of the electrodeposition cycles, thus the amount of the formed polymer. The hybrids were characterized by electron microscopic (SEM, TEM) and vibrational spectroscopic (Raman spectroscopy) means. The obtained results were compared and contrasted with those gathered on macroscopic-sized multi-walled carbon nanotube array-based composites in our group recently. Overall, we conclude that electrochemical polymerization is an attractive tool to synthesize conducting polymer/SWCNT hybrid materials with controlled composition and morphology.
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| 3. |
- Endrődi, Balázs, 1987-, et al.
(författare)
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Fixation of laccase enzyme into polypyrrole, assisted by chemical interaction with modified magnetite nanoparticles : A facile route to synthesize stable electroactive bionanocomposite catalysts
- 2014
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Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 122, s. 282-288
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Tidskriftsartikel (refereegranskat)abstract
- Effective bio-electrocatalysts require stable immobilization of sufficient amounts of the bioactive component. In this study, a novel and efficient method for specific binding of laccase enzyme onto magnetite nanoparticles (NPs) is presented. The interaction between the chemically modified magnetite NPs and the enzyme was evidenced by both infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). Subsequently, the enzyme-coated magnetite NPs were successfully incorporated into polypyrrole (PPy) matrix during galvanostatic electropolymerization. The encapsulation of laccase covered NPs was proved by EQCN, TEM, and FT-IR spectroscopy; whereas the electrochemical behaviour of the formed bionanocomposite was characterized by cyclic voltammetiy. In oxygen saturated solution a cathodic charge surplus was observed, related to the electrochemical reduction of oxygen. This surplus was two times higher in the case of the laccase containing layer compared to its only magnetite containing counterpart. Kinetic aspects of the oxygen reduction reaction (ORR) on the laccase containing films were investigated by hydrodynamic voltammetry, and the four-electron route was found to be exclusive, which is promising from the fuel cell perspective. Such synergistic combination of inorganic NPs and enzymes may open new avenues in the application of these bio-nanocomposite materials.
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| 4. |
- Endrődi, Balázs, 1987-, et al.
(författare)
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Layer by layer growth of electroactive conducting polymer/magnetite hybrid assemblies
- 2013
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Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 171, s. 62-68
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Tidskriftsartikel (refereegranskat)abstract
- Poly(thiophene-acetic-acid)/magnetite nanocomposite electrodes were fabricated from aqueous solutions on PDADMA (polydiallyldimethylammonium chloride) pre-treated ITO covered glass electrodes, employing layer by layer (LBL) technique. This approach was selected on the ground of the interaction between the surface OH-groups of the magnetite and the carboxylic group of the thiophene derivative. The gradual development of the hybrid assembly was followed by UV-vis spectroscopy, and was found to be continuous up to 30 bilayers. Moreover, the absorbance increase at the characteristic wavelengths was linear in the whole examined region. Importantly, the LBL-prepared composites proved to be electroactive, in aqueous phosphate buffer the Fe3+/Fe2+ redox transformation was observed. The electrocatalytic activity of the modified electrodes was demonstrated for electrooxidation of dopamine (DA), and the role of both components as well as their synergistic contribution was elucidated. Preliminary results indicate possible utilization of such hybrid assemblies in the amperometric detection of this analyte.
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| 5. |
- Endrodi, Balazs, et al.
(författare)
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Molecular and supramolecular parameters dictating the thermoelectric performance of conducting polymers: A case study using poly(3-alkylthiophene)s
- 2015
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 119, s. 8472-8479
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we investigated the impact of molecular and supramolecular structure of conducting polymers (CPs) on their thermoelectric properties. As a model system, poly(3-alkylthiophene)s (P3ATs) with different side-chain lengths were prepared through oxidative chemical polymerization and were recrystallized to a well-ordered lamellar structure, resulting in one-dimensional self-assembled nanofibers (evidenced by transmission electron microscopy, X-ray diffraction, and UV-vis spectroscopic measurements). Thermoelectric characterization was performed at different doping levels (precisely tuned by doping in the redox reaction with Ag+ and Fe3+ cations), and the highly doped samples exhibited the best performance for all studied polymers. By varying the length of the alkyl side chain, the supramolecular structure and consequently the electronic properties were varied. The highest electrical conductivity was measured for poly(3-butylthiophene), rooted in its densely packed structure. The established structure-property relationships, concerning the monotonous decrease of the electrical conductivity with the alkyl side chain length, highlight the importance of the supramolecular structure (interchain distance in this case). These findings may contribute to the rational design of organic thermoelectric materials.
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| 6. |
- Endrodi, Balazs, et al.
(författare)
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Reasons behind the improved thermoelectric properties of poly(3-hexylthiophene) nanofiber networks
- 2014
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Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 4:98, s. 55328-55333
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Tidskriftsartikel (refereegranskat)abstract
- Enhanced thermoelectric properties of poly(3-hexylthiophene) nanofiber networks, doped in their reaction with silver cations, are presented. The role of charge carrier concentration and mobility (influenced by the supramolecular structure and nanoscale morphology) is discussed. The nanonet structure leads to a six fold increase in the ZT value compared to the bulk polymer counterpart.
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| 7. |
- Janáky, C., et al.
(författare)
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Chemical synthesis of poly(3-thiophene-acetic-acid)/magnetite nanocomposites with tunable magnetic behaviour
- 2010
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Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 160:1-2, s. 65-71
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Tidskriftsartikel (refereegranskat)abstract
- Conducting polymer-based magnetic composites with controlled magnetic behaviour have been synthesized by chemical polymerization in nanoparticle containing organic media. Poly(3-thiophene-acetic-acid)–Fe3O4 hybrids have been prepared with five different iron-oxide contents, up to 20 m/m%, according to the results obtained by thermogravimetric analysis (TGA) and inductively coupled plasma atomic emission spectroscopic (ICP-AES) measurements. X-ray diffraction (XRD) and Mössbauer spectroscopic results gave direct evidences for the incorporation of both maghemite and magnetite. Photoacoustic Fourier transform infrared spectroscopic (PAS-FT-IR) measurements showed a chemical interaction between the polymer and the iron-oxide particles. SQUID investigations indicated a typical superparamagnetic behaviour for all samples, where saturation magnetization values proved to be tunable by the Fe3O4 content. After coating them onto electrode surfaces, basic electrochemical activity of the composite samples was demonstrated by cyclic voltammetry.
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| 8. |
- Janaky, C., et al.
(författare)
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Synthesis and characterization of polypyrrole-magnetite-vitamin B12 hybrid composite electrodes
- 2010
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Ingår i: Journal of Solid State Electrochemistry. - : Springer. - 1432-8488 .- 1433-0768. ; 14, s. 339-346
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Tidskriftsartikel (refereegranskat)abstract
- In this study vitamin B12 covered magnetite nanoparticles have been incorporated into a conducting polypyrrole. This polymer was electrochemically synthesized in the presence of the B12-coated magnetite. The adsorption of B12 was demonstrated by the decrease in absorbance of the vitamin in the supernatant liquid after B12 has been in contact with magnetite sol overnight. The composition of the layers was studied by the electrochemical quartz crystal microbalance technique during the polymerization. The slope of the mass change–charge curves indicate the incorporation of 27 m/m% magnetite and 15 m/m% B12. The redox transformation of the film in monomer- and nanoparticle-free solutions was also investigated by this method and the difference in the virtual molar masses of the moving species was evidenced. The morphology and the composition of the layers were characterized by scanning electron microscopy combined with energy dispersive X-ray microanalysis measurements, which latter proved the successful incorporation of the magnetic and bio-active components. The electrochemical behavior of the films unambiguously showed the complex redox activity of the composites and the current surplus were quantified by the redox capacity of the layers. These data show the doubling of the redox capacity in case of the hybrid material compared to the neat polymer. The successful enrichment of B12 can be exploited in the recently evidenced redox mediation process performed by a PPy/B12 film.
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| 9. |
- Janáky, C., et al.
(författare)
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Visible-light-enhanced electrocatalytic activity of a polypyrrole/magnetite hybrid electrode toward the reduction of dissolved dioxygen
- 2010
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 114, s. 19338-19344
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Tidskriftsartikel (refereegranskat)abstract
- Conducting polymers are getting more and more interest as both supporting matrixes and electrocatalysts in the oxygen reduction reaction (ORR). A polypyrrole-magnetite nanocomposite layer has been synthesized by using potassium tetraoxalate as the conducting electrolyte. FT-IR measurements proved that chemical modification of the iron oxide by a reaction between the nanoparticles and the salt-leading to an iron oxalate layer on their surface-endows a negative charge to the particles, which leads to their penetration into the polymeric film as a part of the charge compensation. The new hybrid material showed significant photoelectrocatalytic behavior in the ORR. The ratio observed between the stabilized stationary currents under and without illumination is 2.0 for this hybrid. Separate studies on the electrochemical decomposition of H(2)O(2) also indicated an enhanced catalytic activity of the polypyrrole/magnetite hybrid compared with the neat polymer. The results may open new opportunities in the next generation of solar fuel cell applications.
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| 10. |
- Tóth, P. S., et al.
(författare)
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Development of polymer-dopant interactions during electropolymerization, a key factor in determining the redox behaviour of conducting polymers
- 2015
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Ingår i: Journal of Solid State Electrochemistry. - : Springer-Verlag New York. - 1432-8488 .- 1433-0768. ; 19:9, s. 2891-2896
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Tidskriftsartikel (refereegranskat)abstract
- Investigation of ionic motion in connection with the redox transformation of conjugated polymers (CP) has always been at the leading edge of research. Motivated by recent proofs for the chemical bond formation between chloride ion and alpha-positioned carbon in poly (3,4-ethylenedioxythiophene) (PEDOT), comprehensive studies have been extended to another strongly electronegative halide (F-) and to another CP, polypyrrole (PPy). As the electrochemical quartz crystal nanobalance (EQCN) results proved, the movement of the bulky Bu4N+ cations has been exclusively experienced during the redox processes of both systems. Moreover, the decisive role of the anions being present in the polymerization solution in determining the redox capacity and, consequently, the maximum doping level of the films was evidenced. On the grounds of the systematic experiments, the strong and permanent chemical interaction of highly electronegative anions and the polymer has been demonstrated as a general phenomenon. Importantly, this observation requires the necessary reconsideration of specific polymer-dopant interactions and calls attention to the necessity of careful design of the polymerization procedure.
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