| 1. |
- Olalde, I., et al.
(författare)
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The Beaker phenomenon and the genomic transformation of northwest Europe
- 2018
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 555:7695, s. 190-196
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Tidskriftsartikel (refereegranskat)abstract
- From around 2750 to 2500 bc, Bell Beaker pottery became widespread across western and central Europe, before it disappeared between 2200 and 1800 bc. The forces that propelled its expansion are a matter of long-standing debate, and there is support for both cultural diffusion and migration having a role in this process. Here we present genome-wide data from 400 Neolithic, Copper Age and Bronze Age Europeans, including 226 individuals associated with Beaker-complex artefacts. We detected limited genetic affinity between Beaker-complex-associated individuals from Iberia and central Europe, and thus exclude migration as an important mechanism of spread between these two regions. However, migration had a key role in the further dissemination of the Beaker complex. We document this phenomenon most clearly in Britain, where the spread of the Beaker complex introduced high levels of steppe-related ancestry and was associated with the replacement of approximately 90% of Britain's gene pool within a few hundred years, continuing the east-to-west expansion that had brought steppe-related ancestry into central and northern Europe over the previous centuries.
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| 2. |
- Kormányos, A., et al.
(författare)
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Controlled photocatalytic synthesis of core-shell SiC/polyaniline hybrid nanostructures
- 2016
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Ingår i: Materials. - : MDPI. - 1996-1944. ; 9:3
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid materials of electrically conducting polymers and inorganic semiconductors form an exciting class of functional materials. To fully exploit the potential synergies of the hybrid formation, however, sophisticated synthetic methods are required that allow for the fine-tuning of the nanoscale structure of the organic/inorganic interface. Here we present the photocatalytic deposition of a conducting polymer (polyaniline) on the surface of silicon carbide (SiC) nanoparticles. The polymerization is facilitated on the SiC surface, via the oxidation of the monomer molecules by ultraviolet-visible (UV-vis) light irradiation through the photogenerated holes. The synthesized core-shell nanostructures were characterized by UV-vis, Raman, and Fourier Transformed Infrared (FT-IR) Spectroscopy, thermogravimetric analysis, transmission and scanning electron microscopy, and electrochemical methods. It was found that the composition of the hybrids can be varied by simply changing the irradiation time. In addition, we proved the crucial importance of the irradiation wavelength in forming conductive polyaniline, instead of its overoxidized, insulating counterpart. Overall, we conclude that photocatalytic deposition is a promising and versatile approach for the synthesis of conducting polymers with controlled properties on semiconductor surfaces. The presented findings may trigger further studies using photocatalysis as a synthetic strategy to obtain nanoscale hybrid architectures of different semiconductors.
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| 3. |
- Bohner, B., et al.
(författare)
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Flow-driven pattern formation in the calcium-oxalate system
- 2016
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Ingår i: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 144
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Tidskriftsartikel (refereegranskat)abstract
- The precipitation reaction of calcium oxalate is studied experimentally in the presence of spatial gradients by controlled flow of calcium into oxalate solution. The density difference between the reactants leads to strong convection in the form of a gravity current that drives the spatiotemporal pattern formation. The phase diagram of the system is constructed, the evolving precipitate patterns are analyzed and quantitatively characterized by their diameters and the average height of the gravity flow. The compact structures of calcium oxalate monohydrate produced at low flow rates are replaced by the thermodynamically unstable calcium oxalate dihydrate favored in the presence of a strong gravity current.
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| 4. |
- 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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| 5. |
- 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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| 6. |
- Endrodi, Balazs, et al.
(författare)
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Incorporation of cobalt-ferrite nanoparticles into a conducting polymer in aqueous micellar medium : Strategy to get photocatalytic composites
- 2014
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Ingår i: Acta Chimica Slovenica. - 1318-0207. ; 61, s. 376-381
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Tidskriftsartikel (refereegranskat)abstract
- In this study an easy strategy for conducting polymer based nanocomposite formation is presented through the deposition of cobalt-ferrite (CoFe 2O4) containing poly(3,4-ethylenedioxythiophene) (PEDOT) thin layers. The electrochemical polymerization has been performed galvanostatically in an aqueous micellar medium in the presence of the nanoparticlesand the surface active Triton X-100. The nanoparticles have been characterized by Transmission electron microscopy (TEM), the thin layers has been studied by applying Scanning electron microscopy (SEM), and X-ray diffraction (XRD), and the basic electrochemical properties have been also determined. Moreover, electrocatalytic activity of the composite was demonstrated in the electrooxidation reaction of dopamine (DA). The enhanced sensitivity - related to the cobalt-ferritecontent - and the experienced photocatalyitic activity are promising for future application.
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| 7. |
- 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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| 8. |
- Endrodi, Balazs, et al.
(författare)
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Selective electrochemical hydrogen evolution on cerium oxide protected catalyst surfaces
- 2020
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 341
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Tidskriftsartikel (refereegranskat)abstract
- To date the only known solution to avoid the unwanted electrochemical reduction of hypochlorite and chlorate in industrial chlorate production, performed in undivided cells, is the addition of dichromate to the chlorate electrolyte. Because of the toxicity of this compound its use is restricted within the European Union to time limited authorization by REACH. Therefore, an alternative to sodium dichromate is essential to maintain, or even increase the process efficiency. The addition of cerium (III) salts to a hypochlorite solution increases the cathodic selectivity towards hydrogen evolution (HER), the preferred cathode process in industrial chlorate production. This is attributed to the deposition of a thin cerium oxide/hydroxide coating on the cathode, induced by the increased local alkalinity during electrolysis. Performing the electrodeposition of such protective coating ex situ, well-controlled coating thickness can be achieved. Optimizing the deposition conditions (time, current density), a coherent and stable coating is formed on the electrode surface. On this protected electrode surface the electrochemical reduction of hypochlorite is suppressed by ca. 90% compared to the bare Pt electrode, while the HER proceeds with high selectivity and unchanged kinetics. Interestingly, other electrochemical reactions (O-2 reduction, H2O2 reduction and oxidation) are also suppressed by the protective coating, suggesting that the deposited layer acts as an inorganic membrane on the electrode surface.
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| 9. |
- Endrodi, Balazs, et al.
(författare)
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Selective Hydrogen Evolution on Manganese Oxide Coated Electrodes : New Cathodes for Sodium Chlorate Production
- 2019
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 7:14, s. 12170-12178
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Tidskriftsartikel (refereegranskat)abstract
- The safety and feasibility of industrial electrochemical production of sodium chlorate, an important chemical in the pulp and paper industry, depend on the selectivity of the electrode processes. The cathodic reduction of anodic products is sufficiently suppressed in the current technology by the addition of chromium(VI) to the electrolyte, but due to the high toxicity of these compounds, alternative pathways are required to maintain high process efficiency. In this paper, we evaluate the electrochemical hydrogen evolution reaction kinetics and selectivity on thermally formed manganese oxide-coated titanium electrodes in hypochlorite and chlorate solutions. The morphology and phase composition of manganese oxide layers were varied via alteration of the annealing temperature during synthesis, as confirmed by scanning electron microscopy, X-ray diffraction, synchrotron radiation X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure spectroscopy measurements. As shown in mass spectroscopy coupled electrochemical measurements, the hydrogen evolution selectivity in hypochlorite and chlorate solutions is dictated by the phase composition of the coating. Importantly, a hydrogen evolution efficiency of above 95% was achieved with electrodes of optimized composition (annealing temperature, thickness) in hypochlorite solutions. Further, these electrode coatings are nontoxic and Earth-abundant, offering the possibility of a more sustainable chlorate production.
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| 10. |
- 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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