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 thermodynamic parameters indicated that the adsorption of methylene blue onto graphene was an endothermic and spontaneous process and graphene is a good adsorbent for the adsOrption of MB.
634 citations
TL;DR: By considering both the connectivity and mobility of the nanosheets, a quantitative model is developed that completely describes the electromechanical properties of graphene, allowing the manufacture of strain sensors that can detect respiration and the footsteps of spiders.
Abstract: Despite its widespread use in nanocomposites, the effect of embedding graphene in highly viscoelastic polymer matrices is not well understood. We added graphene to a lightly cross-linked polysilicone, often encountered as Silly Putty, changing its electromechanical properties substantially. The resulting nanocomposites display unusual electromechanical behavior, such as postdeformation temporal relaxation of electrical resistance and nonmonotonic changes in resistivity with strain. These phenomena are associated with the mobility of the nanosheets in the low-viscosity polymer matrix. By considering both the connectivity and mobility of the nanosheets, we developed a quantitative model that completely describes the electromechanical properties. These nanocomposites are sensitive electromechanical sensors with gauge factors >500 that can measure pulse, blood pressure, and even the impact associated with the footsteps of a small spider.
631 citations
TL;DR: The results present essential knowledge for more efficient and innocuous applications of graphene sheets and particularly nanoplatelets in upcoming nanotechnology-based tissue engineering as, e.g., drug transporter and scaffolds.
629 citations
Cites background from "Raman spectrum of graphene and grap..."
...Raman spectra of graphene-based materials also present a 2D band (explained by the adopted double resonant model [46,47]) sensitive to stacking of graphene layers [48]....
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TL;DR: Polarized Raman spectra of optical phonons in graphene monolayers under tunable uniaxial tensile stress constitutes a purely optical method for the determination of the crystallographic orientation of graphene.
Abstract: We present a systematic study of the Raman spectra of optical phonons in graphene monolayers under tunable uniaxial tensile stress. Both the G and 2D bands exhibit significant red shifts. The G band splits into 2 distinct subbands (G+, G−) because of the strain-induced symmetry breaking. Raman scattering from the G+ and G− bands shows a distinctive polarization dependence that reflects the angle between the axis of the stress and the underlying graphene crystal axes. Polarized Raman spectroscopy therefore constitutes a purely optical method for the determination of the crystallographic orientation of graphene.
625 citations
Cites background from "Raman spectrum of graphene and grap..."
...Monolayer flakes, deposited on Si wafers with a 290-nm SiO2 epilayer, were initially identified by optical microscopy and their nature was confirmed by Raman spectroscopy (8)....
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...Raman spectroscopy has emerged as a key diagnostic tool to identify single-layer graphene sheets (8) and probe their physical properties (9, 10)....
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TL;DR: The combined experiment and modelling verify the applicability of the classic Griffith theory of brittle fracture to graphene and quantifies the essential fracture properties of graphene and provides mechanistic insights into the mechanical failure of graphene.
Abstract: While the intrinsic strength of graphene has previously been demonstrated to be high, the fracture toughness remains unknown. Here, the authors perform in situ testing of graphene in a scanning electron microscope and report a critical stress intensity factor of ~4.0 MPa√m.
624 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