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Carbon Impurities on Graphene Synthesized by Chemical Vapor Deposition on Platinum  [PDF]
Jinglei Ping,Michael S. Fuhrer
Physics , 2013, DOI: 10.1063/1.4891200
Abstract: We report nanocrystalline carbon impurities coexisting with graphene synthesized via chemical vapor deposition (CVD) on platinum. We observe micron-size island-like impurity layers, which can easily be mistaken for second graphene layers in optical microscopy or secondary electron microscopy (SEM). The island orientation depends on the crystalline orientation of the Pt, as shown by electron backscatter diffraction(EBSD), indicating growth of amorphous carbon below graphene. Dark-field TEM indicates that in addition to uniform single-crystal graphene, our sample is decorated with nanocrystalline carbon impurities with a spatially inhomogeneous distribution. Raman spectra show a large D peak, however electrical characterization shows high mobility (~6,000 cm2/Vs), indicating a limitation for Raman spectroscopy in characterizing the electronic quality of graphene.
Reduced graphene oxide as ultra fast temperature sensor  [PDF]
Satyaprakash Sahoo,Sujit K. Barik,G. L. Sharma,Geetika Khurana,J. F. Scott,Ram S. Katiyar
Physics , 2012,
Abstract: We demonstrate the excellent temperature sensing property of a chemically synthesized reduced graphene oxide (rGO). It is found that with increase in temperature from 80 to 375K, the resistivity of reduced graphene oxide monotonically decreases. The ultra-fast temperature sensing property is demonstrated by keeping and removing a block of ice under the rGO sensor, which shows the resistance of rGO increases by 15% in 592 miliseconds and recovers in 8.92 seconds. The temperature sensing of rGO is compared with a standard platinum thermo sensor (Pt 111) and found the sensitivity is much better in rGO.
Ion Irradiation of Nanocrystalline Graphene on Quartz and Sapphire  [PDF]
Maria Edera,Alexander M. Zaitsev
Physics , 2015,
Abstract: The effects of Ga+ ion irradiation and high temperature annealing on behavior of nanocrystalline graphene directly grown on quartz and sapphire are presented. It is shown that nanocrystalline graphene stands fairly high doses of ion irradiation (up to 3e14 cm-2 of 5 to 50 keV Ga+ ions) without degradation in conductance. At higher doses, nanocrystalline graphene rapidly loses its conductance and at doses over 2e15 cm-2 becomes actually insulating. Annealing in vacuum restores conductance of the irradiated nanocrystalline graphene and, if the irradiation has not exceeded a dose of 3e15 cm-2, this restoration can be complete. Ion irradiation at high doses approaching 1e16 cm-2 results in complete ion sputtering of a few layer graphene. Along with the irradiation-induced reduction of conductance and the temperature-induced restoration of conductance, two other effects of the ion irradiation are the enhancement of adhesion of graphene to substrate and the increase in the nucleation capability of substrate for direct deposition of graphene. For 50 keV Ga+ ions, the enhancement of adhesion is observed at irradiation doses over 2e14 cm-2. The promoted graphene nucleation is observed in a broad dose range. It is shown that the above effects can be used for development of methods of patterning of graphene on insulating substrates and a method of imprint lithography of graphene.
Platinum–Vanadium Oxide Nanotube Hybrids  [cached]
Mello FilipeLS,Costa LídiaOO,Hernández EduardoPadrón,de Farias AndréaMDuarte
Nanoscale Research Letters , 2010,
Abstract: The present contribution reports on the features of platinum-based systems supported on vanadium oxide nanotubes. The synthesis of nanotubes was carried out using a commercial vanadium pentoxide via hydrothermal route. The nanostructured hybrid materials were prepared by wet impregnation using two different platinum precursors. The formation of platinum nanoparticles was evaluated by applying distinct reduction procedures. All nanostructured samples were essentially analysed by X-ray diffraction and transmission electron microscopy. After reduction, transmission electron microscopy also made it possible to estimate particle size distribution and mean diameter calculations. It could be seen that all reduction procedures did not affect the nanostructure of the supports and that the formation of metallic nanoparticles is quite efficient with an indistinct distribution along the nanotubes. Nevertheless, the reduction procedure determined the diameter, dispersion and shape of the metallic particles. It could be concluded that the use of H2PtCl6 is more suitable and that the use of hydrogen as reducing agent leads to a nanomaterial with unagglomerated round-shaped metallic particles with mean size of 6–7 nm.
Molecular theory of graphene oxide  [PDF]
Elena F. Sheka,Nadezhda A. Popova
Physics , 2012,
Abstract: Applying to graphene oxides, molecular theory of graphene is based on the oxide molecular origin when it is considered as a final product in the succession of a graphene molecule polyderivatives related to a particular oxidation reaction. The graphene oxide structure is created in due course of calculations following the algorithms that take into account the graphene molecules natural radicalization, correlation of odd electrons, an extremely strong influence of structure on properties, a sharp response of the molecule behavior on small action of external factors. Taking together, the theory facilities has allowed for getting a clear, transparent and understandable explanation of hot points of the graphene oxide chemistry and suggesting reliable models of both chemically produced and chemically reduced graphene oxides.
Nanocrystalline Cerium Oxide Films for Microelectronic Biosensor Transducers  [cached]
Maksimchuk N.
Proceedings of the International Conference Nanomaterials : Applications and Properties , 2012,
Abstract: The physical properties of thin nanocrystalline cerium oxide films have been studied with the purpose of their application as a functional material of different microelectronic transducers for biosensors: high-performance photoresistors and photodiodes for bioluminescence registration, ion-selective field-effect transistors (ISFET) and MOS-varactors indicating the pH changes as a result of biochemical processes. The effect of technological factors on the photoelectrical, optical, temperature and electrophysical properties of cerium oxide films has been studied. We established the technological conditions which allow to obtain СеОх-films with desired functional characteristics. On the basis of the synthesized nanocrystalline СеОх-films obtained by the "explosive evaporation" method we developed new types of photodetectors for registration of bioluminescent signal (photoresistors and photodiodes) with enhanced photosensitivity (310-330 mA/lm V) in the visible range. Application of cerium oxide based photoresistors in the bioluminometers instead of photomultiplier tubes and avalanche photodiodes allows to significantly reduce the cost of bioluminometer and increase its sensitivity when measuring at alternating signal. On the basis of nanocrystalline СеОх-films obtained by the "metallic mirrors oxidation" method we developed potentiometric biosensory transducers (ion-selective field-effect transistors and MOS-varactors) with CeOx as gate dielectric. It yields higher sensitivity and stability as compared to the use of the SiO2 and Si3N4 films.
Carbon Mono and Dioxide Hydrogenation over Pure and Metal Oxide Decorated Graphene Oxide Substrates: Insight from DFT  [PDF]
Danil W. Boukhvalov
Graphene (Graphene) , 2013, DOI: 10.4236/graphene.2013.23016
Abstract:

Based on first principles density functional theory calculations we explore the energetics of the conversion of carbon mono and dioxide to methane over graphene oxide surfaces. Similar to therecently discovered hydration of various organic species over this catalyst, the transfer of hydrogenatoms from hydroxyl groups of graphene oxide provide a step by step transformation hydrogenationof carbon oxides. Estimated yields of modeled reactions at room temperature are about 0.01% for thecarbon mono and dioxide. For the modeling of graphene oxide/metal oxide composites, calculationsin the presence of MO2(where M = V, Cr, Mn, Fe) have been performed. Results of these calculations demonstrate significant decreases of the energy costs and increases of reaction yields to 0.07%, which is comparable to the efficiency of these reactions over platinum and ruthenium-based photocatalysts. Increasing the temperature to the value 100°C should provide the total conversion of carbon mono and dioxides.

Self-Organized Platinum Nanoparticles on Freestanding Graphene  [PDF]
Peng Xu,Lifeng Dong,Mehdi Neek-Amal,Matthew L. Ackerman,Jianhua Yu,Steven D. Barber,James Kevin Schoelz,Dejun Qi,Fangfang Xu,Paul M. Thibado,Francois M. Peeters
Physics , 2014,
Abstract: Freestanding graphene membranes were successfully functionalized with platinum nanoparticles (Pt NPs). High-resolution transmission electron microscopy revealed a homogeneous distribution of single-crystal Pt NPs that tend to exhibit a preferred orientation. Unexpectedly, the NPs were also found to be partially exposed to the vacuum with the top Pt surface raised above the graphene substrate, as deduced from atomic-scale scanning tunneling microscopy images and detailed molecular dynamics simulations. Local strain accumulation during the growth process is thought to be the origin of the NP self-organization. These findings are expected to shape future approaches in developing Pt NP catalysts for fuel cells as well as NP-functionalized graphene based high-performance electronics.
Pt Supported on Reduced Graphite Oxide Catalysts for H2 Activation  [cached]
Dremova N.N.,Kushch S.D.,Kuyunko N.S.,Arbuzov A.A.
Proceedings of the International Conference Nanomaterials : Applications and Properties , 2013,
Abstract: Platinum catalysts of H2 activation with average size ≤2.0 nm were prepared in a base of reduction conversion of graphene oxide. A low few-layered carbon nanomaterial was prepared by thermoexpansion and annealing of graphene oxide. The uniformly dispersed Pt nanoparticles were supported on two-dimension graphene flat material by the use of pyridine or polyethyleneimine in alkaline (pH≈10) media as chelating agent modificating both metal precursor H2PtCl6 and support. Vacancies in carbon material formed as a result of thermoexpansion and annealing of graphite oxide probablly serve as anchor groups in platinum supporting.
Graphene produced by radiation-induced reduction of graphene oxide  [PDF]
Prashant Kumar,K. S. Subrahmanyam,C. N. R. Rao
Physics , 2010, DOI: 10.1142/S0219581X11008824
Abstract: Effect of irradiation on graphene oxide by sunlight, UV light and KrF excimer laser has been investigated in detail. Both sunlight and ultraviolet light reduce graphene oxide well after prolonged irradiation, but laser irradiation produces graphene with negligible oxygen functionalities within a short time. Laser irradiation is also useful for one-step synthesis of metal particle decorated graphene. Laser irradiation of graphene oxide appears to be an efficient procedure for large-scale synthesis of graphene.
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