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 structural and vibrational properties of two-dimensional hexagonal silicon (silicene) and germanium (germanene) are investigated by means of first-principles calculations as mentioned in this paper.
Abstract: The structural and vibrational properties of two-dimensional hexagonal silicon (silicene) and germanium (germanene) are investigated by means of first-principles calculations. It is predict that the silicene (germanene) structure with a small buckling of 0.44 A (0.7 A) and bond lengths of 2.28 A (2.44 A) is energetically the most favorable, and it does not exhibit imaginary phonon mode. The calculated non-resonance Raman spectra of silicene is characterized by a main peak at about 575 cm−1, namely the G-like peak. For germanene, the highest peak is at about 290 cm−1. Extensive calculations on armchair silicene nanoribbons and armchair germanene nanoribbons are also performed, with and without hydrogenation of the edges. The studies reveal other Raman peaks mainly distributed at lower frequencies than the G-like peak which could be attributed to the defects at the edges of the ribbons, thus not present in the Raman spectra of non-defective silicene and germanene. Particularly the Raman peak corresponding to the D mode is found to be located at around 515 cm−1 for silicene and 270 cm−1 for germanene. The calculated G-like and the D peaks are likely the fingerprints of the Raman spectra of the low-buckled structures of silicene and germanene.
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164 citations
TL;DR: In this paper, a well-dispersed Pd nanoparticles supported on low-defect graphene (LDG) sheets are successfully prepared by a soft chemical method, which can efficiently avoid damaging the graphene framework in the composite because it does not require cumbersome oxidation of graphite in advance and needs no subsequent reduction of the LDG sheets due to the lower oxidation degree.
Abstract: Well-dispersed Pd nanoparticles supported on low-defect graphene (LDG) sheets are successfully prepared by a soft chemical method. Our approach can efficiently avoid damaging the graphene framework in the composite because it does not require cumbersome oxidation of graphite in advance and needs no subsequent reduction of the LDG sheets due to the lower oxidation degree. Morphology observations show that the Pd nanoparticles with diameters ranging from 1 to 5 nm are evenly deposited on graphene sheets. Raman spectroscopic analysis results reveals that there is only a very small amount of graphene defects in the hybrid. No matter whether it is for a direct formic acid fuel cell (DFAFC) or direct methanol fuel cell (DMFC), the LDG-supported Pd catalyst has very large electrochemically active surface area (ECSA) values, more than twice as large as that for the reduced graphene oxide, or five times the commercial XC-72 carbon. The forward peak current measurements show similar results. The excellent catalytic performance of LDG/Pd can be attributed to the preserved pristine graphene structure, which not only provides a lot of surface area for the deposition of nanoparticles, but also allows for electrical conductivity and stability in the composite.
164 citations
TL;DR: Besides being eco-friendly, this mushroom based approach is easily scalable and demonstrates remarkable RGO stability and biocompatibility, even without any form of functionalization.
Abstract: Purpose: A simple, one-pot strategy was used to synthesize reduced graphene oxide (RGO) nanosheets by utilizing an easily available over-the-counter medicinal and edible mushroom, Ganoderma lucidum. Methods: The mushroom was boiled in hot water to liberate the polysaccharides, the extract of which was then used directly for the reduction of graphene oxide. The abundance of polysaccharides present in the mushroom serves as a good reducing agent. The proposed strategy evades the use of harmful and expensive chemicals and avoids the typical tedious reaction methods. Results: More importantly, the mushroom extract can be easily separated from the product without generating any residual byproducts and can be reused at least three times with good conversion efficiency (75%). It was readily dispersible in water without the need of ultrasonica tion or any surfactants; whereas 5 minutes of ultrasonication with various solvents produced RGO which was stable for the tested period of 1 year. Based on electrochemical measurements, the followed method did not jeopardize RGO’s electrical conductivity. Moreover, the obtained RGO was highly biocompatible to not only colon (HT-29) and brain (U87MG) cancer cells, but was also viable towards normal cells (MRC-5). Conclusion: Besides being eco-friendly, this mushroom based approach is easily scalable and demonstrates remarkable RGO stability and biocompatibility, even without any form of
164 citations
Cites background from "Raman spectrum of graphene and grap..."
...After reduction, this peak has marginally broadened and shifted to 2,769 cm-1 suggesting the presence of three-layered graphene sheets.(67) The cooperation between D and G peaks gives the D plus G combination band which indicates the presence of highly disordered and randomly arranged graphene sheets....
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TL;DR: In this article, high-quality graphene nanosheets have been synthesized by radio-frequency plasma-enhanced chemical vapor deposition on nickel-foam current collectors and that have been used as substrates for cathodic electrodeposition of cobalt hydroxide nano-electrode in Co(NO3)2 aqueous solution.
164 citations
Cites background from "Raman spectrum of graphene and grap..."
...1 e (a) SEM image, (b) TEM image, (c) Raman spectroscopy, an which can further confirm the nanosheet structure of the graphene [40,41]....
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...[41] Ferrari AC, Meyer JC, Scardaci V, Casiraghi C, Lazzeri M, Mauri F, et al....
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TL;DR: The exploitation of GRMs in the form of dispersions and inks opens the way for scalable large-area production, advancing the possible commercialization of PSCs.
Abstract: Interface engineering is performed by the addition of graphene and related 2 D materials (GRMs) into perovskite solar cells (PSCs), leading to improvements in the power conversion efficiency (PCE). By doping the mesoporous TiO2 layer with graphene flakes (mTiO2+G), produced by liquid-phase exfoliation of pristine graphite, and by inserting graphene oxide (GO) as an interlayer between the perovskite and hole-transport layers, using a two-step deposition procedure in air, we achieved a PCE of 18.2 %. The obtained PCE value mainly results from improved charge-carrier injection/collection with respect to conventional PSCs. Although the addition of GRMs does not influence the shelf life, it is beneficial for the stability of PSCs under several aging conditions. In particular, mTiO2+G PSCs retain more than 88 % of the initial PCE after 16 h of prolonged 1 sun illumination at the maximum power point. Moreover, when subjected to prolonged heating at 60 °C, the GO-based structures show enhanced stability with respect to mTiO2+G PSCs, as a result of thermally induced modification at the mTiO2+G/perovskite interface. The exploitation of GRMs in the form of dispersions and inks opens the way for scalable large-area production, advancing the possible commercialization of PSCs.
164 citations
References
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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