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: In this article, the time-dependent structural modifications in single-crystal graphene due to laser irradiation even at moderate power levels of 1 mW in a diffraction-limited spot were characterized by in situ scanning confocal Raman spectroscopy.
Abstract: We report about investigations of time-dependent structural modifications in single-crystal graphene due to laser irradiation even at moderate power levels of 1 mW in a diffraction-limited spot. The modifications have been characterized by in situ scanning confocal Raman spectroscopy, atomic force height microscopy, and transport studies. The time evolution of the Raman spectrum reveals two different effects: on a short-time scale, dopants, initially present on the flake, are removed. The longer time scale behavior points to a laser induced gradual local decomposition of single-crystal graphene into a network of interconnected nanocrystallites with a characteristic length scale of approximately 10 nm due to bond breaking. The broken bonds offer additional docking sites for adsorbates as confirmed in transport and AFM height studies. These controlled structural modifications may for instance be valuable for enhancing the local reactivity, trimming graphene based gas sensors and generating spatially varying doping patterns.
223 citations
TL;DR: Graphene is a fundamentally new type of electronic material whose electrons are strictly confined to a two-dimensional plane and exhibit properties akin to those of ultrarelativistic particles.
Abstract: Graphene, a single atom-thick plane of carbon atoms arranged in a honeycomb lattice, has captivated the attention of physicists, materials scientists, and engineers alike over the five years following its experimental isolation. Graphene is a fundamentally new type of electronic material whose electrons are strictly confined to a two-dimensional plane and exhibit properties akin to those of ultrarelativistic particles. Graphene's two-dimensional form suggests compatibility with conventional wafer processing technology. Extraordinary physical properties, including exceedingly high charge carrier mobility, current-carrying capacity, mechanical strength, and thermal conductivity, make it an enticing candidate for new electronic technologies both within and beyond complementary metal oxide semiconductors (CMOS). Immediate graphene applications include high-speed analog electronics and highly conductive, flexible, transparent thin films for displays and optoelectronics. Currently, much graphene research is focused on generating and tuning a bandgap and on novel device structures that exploit graphene's extraordinary electrical, optical, and mechanical properties.
223 citations
TL;DR: A ∼50% amplitude modulation of THz waves with gated single-layer graphene is demonstrated by the use of extraordinary transmission through metallic ring apertures placed right above the graphene layer, promising complementary metal-oxide-semiconductor compatible THz modulators with tailored operation frequencies, large on/off ratios, and high speeds.
Abstract: Gate-controllable transmission of terahertz (THz) radiation makes graphene a promising material for making high-speed THz wave modulators. However, to date, graphene-based THz modulators have exhibited only small on/off ratios due to small THz absorption in single-layer graphene. Here we demonstrate a ∼50% amplitude modulation of THz waves with gated single-layer graphene by the use of extraordinary transmission through metallic ring apertures placed right above the graphene layer. The extraordinary transmission induced ∼7 times near-filed enhancement of THz absorption in graphene. These results promise complementary metal–oxide–semiconductor compatible THz modulators with tailored operation frequencies, large on/off ratios, and high speeds, ideal for applications in THz communications, imaging, and sensing.
222 citations
TL;DR: In this article, a 3D graphene/MnO2 aerogel was fabricated via self-assembly and reduction of graphene oxide, followed by in situ solution-phase deposition of ultrathin birnessite MnO2 nanosheets.
Abstract: Novel three-dimensional (3D) graphene/δ-MnO2 aerogels were fabricated via self-assembly and reduction of graphene oxide, followed by in situ solution-phase deposition of ultrathin δ-MnO2 nanosheets. The resultant graphene/δ-MnO2 architectures showed an interconnected 3D network microstructure, in which a large number of ultrathin birnessite MnO2 nanosheets were homogenously deposited on the graphene framework. Due to their unique structural characteristics, the resulting 3D aerogels exhibited a fast adsorption kinetic rate and superior adsorption capacity toward heavy metal ions. The saturated adsorption capacities of graphene/δ-MnO2 aerogels were as large as 643.62 mg g−1 for Pb2+, 250.31 mg g−1 for Cd2+ and 228.46 mg g−1 for Cu2+ calculated by the Langmuir isotherm model, exceeding largely the corresponding pristine 3D graphene and δ-MnO2 nanosheets. It was noted that the heavy metal ions could not only adsorb on the surface of graphene/δ-MnO2, but also intercalate into the interlayer gaps of birnessite MnO2, which reveals the synergistic effect of the static electrical attraction, surface complexation and ion exchange between heavy metal ions and pre-intercalated K+, supported by the expansion of the basic crystal structure of layered MnO2 after adsorption. Furthermore, it is interesting that the regenerated aerogels after the initial HCl and subsequent KOH treatment still maintain their original shape and can be repeatedly used for more than eight cycles without obvious degradation of performance, which achieved the sustainability of the absorbents. More importantly, the hybrid aerogels can be easily separated and do not generate secondary contaminants. High removal efficiency, fast adsorption kinetics, excellent regeneration and reusability, and ease of separation operation make these hybrid aerogels ideal candidates for heavy metal ion decontamination in practical application.
222 citations
TL;DR: Insight into preparation strategies and approaches of MGO's utilization for the removal of pollutants for sustainable water purification and some research challenges to accelerate the synthesized MGOs as adsorbents for the treatment of water pollutants such as toxic and radioactive metal ions and organic and agricultural pollutants are provided.
222 citations
Cites background from "Raman spectrum of graphene and grap..."
...Hence, water is one of the major routes through which heavy metals and radionuclides may enter the human body upon consumption of potable water (Förstner and Wittmann, 1981; Ihsanullah et al., 2016)....
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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