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Electronic states of disordered grain boundaries in graphene prepared by chemical vapor deposition
Nemes-Incze, P.,Vancso, P.,Osvath, Z.,Mark, G.I.,Jin, X.,Kim, Y.S.,Hwang, C.,Lambin, P.,Chapelier, C.,PeterBiro, L. Pergamon Press ; Elsevier Science Ltd 2013 Carbon Vol.64 No.-
Perturbations of the two dimensional carbon lattice of graphene, such as grain boundaries, have significant influence on the charge transport and mechanical properties of this material. Scanning tunneling microscopy measurements presented here show that localized states near the Dirac point dominate the local density of states of grain boundaries in graphene grown by chemical vapor deposition. Such low energy states are not reproduced by theoretical models which treat the grain boundaries as periodic dislocation-cores composed of pentagonal-heptagonal carbon rings. Using ab initio calculations, we have extended this model to include disorder, by introducing vacancies into a grain boundary consisting of periodic dislocation-cores. Within the framework of this model we were able to reproduce the measured density of states features. We present evidence that grain boundaries in graphene grown on copper incorporate a significant amount of disorder in the form of two-coordinated carbon atoms.
Moire superlattices in strained graphene-gold hybrid nanostructures
Palinkas, A.,Sule, P.,Szendro, M.,Molnar, G.,Hwang, C.,Biro, L.P.,Osvath, Z. Pergamon Press ; Elsevier Science Ltd 2016 Carbon Vol.107 No.-
<P>Graphene-metal nanoparticle hybrid materials potentially display not only the unique properties of metal nanoparticles and those of graphene, but also additional novel properties due to the interaction between graphene and nanoparticles. This study shows that gold nanoislands can be used to tailor the local electronic properties of graphene. Graphene on crystalline gold nanoislands exhibits moire superlattices, which generate secondary Dirac points in the local density of states. Conversely, the graphene covered gold regions undergo a polycrystalline -> Au (111) phase transition upon annealing. Moreover, the nanoscale coexistence of moire superlattices with different moire periodicities has also been revealed. Several of these moire periodicities are anomalously large, which cannot be explained by the standard lattice mismatch between the graphene and the topmost Au (111) layers. Density functional theory and molecular dynamics simulations show for the first time that in such cases the graphene and the interfacial metallic layer is strained, leading to distorted lattice constants, and consequently to reduced misfit. Room temperature charge localization induced by a large wavelength moire pattern is also observed by scanning tunneling spectroscopy. These findings can open a route towards the strain engineering of graphene/metal interfaces with various moire superlattices and tailored electronic properties for nanoscale information coding. (C) 2016 Elsevier Ltd. All rights reserved.</P>
Inexpensive, upscalable nanotube growth methods
Z.E. Horvath,K. Kertesz,L. Petho,A.A. Koos,L. Tapaszto,Z. Vertesy,Z. Osvath,Al. Darabont,P. Nemes-Incze,Zs. Ssrkozi,L.P. Bir? 한국물리학회 2006 Current Applied Physics Vol.6 No.2
Despite of the very promising foreseen applications, the use of carbon nanotubes in wider range is still limited by the high pro-duction costs. In this paper, our latest results concerning two inexpensive methods of carbon nanotube growth with the promise ofindustrial upscaling are presented. In case of the DC ‘‘arc in water’’ method, the eect of the angle of the two electrodes on theproduct yield was investigated. The highest nanotube yield and lowest amount of impurities were found at 90. electrode angles.zene/ferrocene solution in case of the injection CVD or ‘‘spay pyrolysis’’ method. Toluene, xylene, cyclohexane, cyclohexanone,n-hexane,n-heptane,n-octane andn-pentane were used as carbon source and cobaltocene and nickelocene as catalyst source. All thesecompounds were found to be suitable for nanotube production. The highest yield and the best quality were obtained when a mixtureof ferrocenenickelocene was used as catalyst and xylene as carbon source
Periá,ñ,ez, R.,Bezhenar, R.,Brovchenko, I.,Duffa, C.,Iosjpe, M.,Jung, K.T.,Kobayashi, T.,Lamego, F.,Maderich, V.,Min, B.I.,Nies, H.,Osvath, I.,Outola, I.,Psaltaki, M.,Suh, K.S.,de With, G. Elsevier 2016 Science of the Total Environment Vol.569 No.-
<P><B>Abstract</B></P> <P>State-of-the art dispersion models were applied to simulate <SUP>137</SUP>Cs dispersion from Chernobyl nuclear power plant disaster fallout in the Baltic Sea and from Fukushima Daiichi nuclear plant releases in the Pacific Ocean after the 2011 tsunami. Models were of different nature, from box to full three-dimensional models, and included water/sediment interactions. Agreement between models was very good in the Baltic. In the case of Fukushima, results from models could be considered to be in acceptable agreement only after a model harmonization process consisting of using exactly the same forcing (water circulation and parameters) in all models. It was found that the dynamics of the considered system (magnitude and variability of currents) was essential in obtaining a good agreement between models. The difficulties in developing operative models for decision-making support in these dynamic environments were highlighted. Three stages which should be considered after an emergency, each of them requiring specific modelling approaches, have been defined. They are the emergency, the post-emergency and the long-term phases.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Models applied to simulate <SUP>137</SUP>Cs marine dispersion after nuclear accidents. </LI> <LI> Not good agreement initially found in highly dynamic environments. </LI> <LI> Difficulties in developing models for decision making after emergencies highlighted. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>