Raman spectrum of graphene and graphene layers.
TL;DR: This work shows that graphene's electronic structure is captured in its Raman spectrum that clearly evolves with the number of layers, and allows unambiguous, high-throughput, nondestructive identification of graphene layers, which is critically lacking in this emerging research area.
Abstract: Graphene is the two-dimensional building block for carbon allotropes of every other dimensionality We show that its electronic structure is captured in its Raman spectrum that clearly evolves with the number of layers The D peak second order changes in shape, width, and position for an increasing number of layers, reflecting the change in the electron bands via a double resonant Raman process The G peak slightly down-shifts This allows unambiguous, high-throughput, nondestructive identification of graphene layers, which is critically lacking in this emerging research area
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TL;DR: The enhanced performance results from its unique features: excellent electronic conductivity associated with the N-doped graphene, short transportation length for lithium ions related to ultrathin nanosheets, and improved charge transfer due to the anchoring of the VO2(B) flowers to N- doped graphene.
Abstract: Recently, we have shown that the graphene–VO2(B) nanotube hybrid is a promising lithium ion battery cathode material (Nethravathi et al. Carbon, 2012, 50, 4839–4846). Though the observed capacity of this material was quite satisfactory, the rate capability was not. To improve the rate capability we wanted to prepare a graphene–VO2(B) hybrid in which the VO2(B) would be built on 2D nanosheets that would enable better electrode–electrolyte contact. Such a material, a N-doped graphene–VO2(B) nanosheet-built 3D flower hybrid, is fabricated by a single-step hydrothermal reaction within a mixture of ammonium vanadate and colloidal dispersion of graphite oxide. The 3D VO2(B) flowers which are uniformly distributed on N-doped graphene are composed of ultrathin 2D nanosheets. When used in lithium ion batteries, this material exhibits a large capacity, high rate capability, and excellent cycling stability. The enhanced performance results from its unique features: excellent electronic conductivity associated with t...
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TL;DR: Graphene from two different preparative routes was successfully functionalized with 4-propargyloxybenzenediazonium tetrafluoroborate in order to study a subsequent attachment by click chemistry of a short chain polyethylene glycol with terminal carboxylic end group (PEG-COOH) as discussed by the authors.
Abstract: Graphene from two different preparative routes was successfully functionalized with 4-propargyloxybenzenediazonium tetrafluoroborate in order to study a subsequent attachment by click chemistry (1,3-dipolar azide–alkyne cycloaddition) of a short chain polyethylene glycol with terminal carboxylic end group (PEG-COOH). The reaction steps were studied by FTIR and Raman spectroscopies, as well as zeta-potential and surface tension measurements. In the first route, pristine graphene was surfactant dispersed from a stage controlled expanded graphite before reaction, resulting in colloidally stable dispersions after dialysis removal of the surfactant following the two functionalization steps. The chemistry was shown to increase the zeta-potential from −45.3 to −54.6 mV and increase the surface tension from 48.5 to 63.0 mN/m compared to those of the precursor solution. The magnitudes of the zeta-potential and the resulting solution concentration were shown to increase with grafting density up to 14.2 μg/mL. A col...
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TL;DR: This work reports the successful growth of quasicrystalline 30° twisted bilayer graphene (30°-tBLG), which is stabilized by the Pt(111) substrate, and reveals its electronic structure, thereby extending band structure engineering to incommensurate superstructures.
Abstract: The interlayer coupling can be used to engineer the electronic structure of van der Waals heterostructures (superlattices) to obtain properties that are not possible in a single material. So far research in heterostructures has been focused on commensurate superlattices with a long-ranged Moire period. Incommensurate heterostructures with rotational symmetry but not translational symmetry (in analogy to quasicrystals) are not only rare in nature, but also the interlayer interaction has often been assumed to be negligible due to the lack of phase coherence. Here we report the successful growth of quasicrystalline 30° twisted bilayer graphene (30°-tBLG), which is stabilized by the Pt(111) substrate, and reveal its electronic structure. The 30°-tBLG is confirmed by low energy electron diffraction and the intervalley double-resonance Raman mode at 1383 cm-1 Moreover, the emergence of mirrored Dirac cones inside the Brillouin zone of each graphene layer and a gap opening at the zone boundary suggest that these two graphene layers are coupled via a generalized Umklapp scattering mechanism-that is, scattering of a Dirac cone in one graphene layer by the reciprocal lattice vector of the other graphene layer. Our work highlights the important role of interlayer coupling in incommensurate quasicrystalline superlattices, thereby extending band structure engineering to incommensurate superstructures.
172 citations
Cites background or methods from "Raman spectrum of graphene and grap..."
...Raman spectroscopy is a powerful tool for characterizing the vibrational mode in graphene (23) and can provide direct information about the sample thickness and stacking....
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...The peak at 1353 cm−1 is the D mode of graphene which is caused by the limited size or defects (23)....
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...The spectra for both regions show characteristic features of monolayer graphene (23), in which the 2D mode shows a single Lorentzian peak with stronger intensity than the G mode....
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TL;DR: A dispersion of graphene in ethanol was achieved using solvent exchange from N-methyl-2-pyrrolidone (NMP) that enables broader application of dispersed graphene.
172 citations
TL;DR: In this article, the Raman spectroscopy was used to monitor the quality of graphene films transferred onto SiO 2 /Si substrates and the dependence of the sensing response with the operating temperature was studied.
Abstract: Ammonia gas sensing behavior of graphene synthesized by CVD on copper substrate using a methane and hydrogen gas mixture was investigated. The Raman spectroscopy was used to monitor the quality of graphene films transferred onto SiO 2 /Si substrates. The sensitivity and the recovery time of the device were enhanced by the deposition of gold nanoparticles on the surface of graphene films. The dependence of the sensing response with the operating temperature was studied. The adsorption and desorption curves were analyzed using Langmuir kinetic theory and Freundlich isotherm for the adsorption of ammonia gas. The activation energy and the heat of adsorption were estimated to be around 38 and 41 meV, respectively for NH 3 gas concentration of 58 ppm at room temperature.
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28 Jul 2005
TL;DR: PfPMP1）与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。
18,940 citations