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, a 3D carbon nanostructure comprising few-layer graphene (FLG) sheets inherently connected with CNTs through sp2 carbons, resembling plant leaves (FLGs) growing on stems (CNTs).
Abstract: Hybrid nanomaterials composed of carbon nanotubes (CNTs) and graphene could potentially display outstanding properties that are superior to either CNTs or graphene alone. However, the inherent CNT–graphene loose junctions present in the CNT–graphene composites synthesized by existing methods significantly hinder the realization of the full potential held by CNT–graphene hybrids. In this letter, we report on a brand-new, three-dimensional (3D) carbon nanostructure comprising few-layer graphene (FLG) sheets inherently connected with CNTs through sp2 carbons, resembling plant leaves (FLGs) growing on stems (CNTs). The resulting hybrid nanostructures were characterized using scanning electron microscopy, transmission electron microscopy (TEM), Raman spectroscopy, and X-ray photoelectron spectroscopy. The evolution of FLG sheets on CNTs was tracked by high-resolution TEM. Distinct from a random mixture of CNTs and graphene sheets (CNT+G) suffering from poor CNT–graphene contacts, our CNT–FLG structure has intr...
183 citations
TL;DR: This work demonstrates the growth of large-area sulfur (S)-doped graphene sheets on copper substrate via the chemical vapor deposition technique by using liquid organics (hexane in the presence of S) as the precursor, and found that S could be doped into graphene's lattice and mainly formed linear nanodomains.
Abstract: Doping is a common and effective approach to tailor semiconductor properties. Here, we demonstrate the growth of large-area sulfur (S)-doped graphene sheets on copper substrate via the chemical vapor deposition technique by using liquid organics (hexane in the presence of S) as the precursor. We found that S could be doped into graphene's lattice and mainly formed linear nanodomains, which was proved by elemental analysis, high resolution transmission microscopy and Raman spectra. Measurements on S-doped graphene field-effect transistors (G-FETs) revealed that S-doped graphene exhibited lower conductivity and distinctive p-type semiconductor properties compared with those of pristine graphene. Our approach has produced a new member in the family of graphene based materials and is promising for producing graphene based devices for multiple applications.
183 citations
TL;DR: The authors develop a method to test a large area of graphene and show that even with edge defects it displays near-ideal mechanical performance, as well as resilience and mechanical robustness that allows for flexible electronics and mechatronics applications.
Abstract: The sp2 nature of graphene endows the hexagonal lattice with very high theoretical stiffness, strength and resilience, all well-documented. However, the ultimate stretchability of graphene has not yet been demonstrated due to the difficulties in experimental design. Here, directly performing in situ tensile tests in a scanning electron microscope after developing a protocol for sample transfer, shaping and straining, we report the elastic properties and stretchability of free-standing single-crystalline monolayer graphene grown by chemical vapor deposition. The measured Young’s modulus is close to 1 TPa, aligning well with the theoretical value, while the representative engineering tensile strength reaches ~50-60 GPa with sample-wide elastic strain up to ~6%. Our findings demonstrate that single-crystalline monolayer graphene can indeed display near ideal mechanical performance, even in a large area with edge defects, as well as resilience and mechanical robustness that allows for flexible electronics and mechatronics applications. The extraordinary mechanical properties of graphene are usually measured on very small or supported samples. Here, the authors develop a method to test a large area of graphene and show that even with edge defects it displays near-ideal mechanical performance.
183 citations
27 Jan 2020
TL;DR: The synthesis of high-quality graphene nanosheets obtained by electrochemical exfoliation of biomass-derived from corn cob is reported, opening the possibility of direct electrochemical analysis of analyte without any sample preparation.
Abstract: The demand for high-quality graphene for electronic applications is increasing due to its high carrier mobility and electrical conductivity. In this connection, printing technology is a reliable method towards the fabrication of conductive, disposable graphene-based electrode for low-cost sensor application. Herein, we aimed to report the synthesis of high-quality graphene nanosheets obtained by electrochemical exfoliation of biomass-derived from corn cob. The conductive ink was prepared from this exfoliated graphene and was utilized for the preparation of paper-based graphene electrode towards double stranded DNA (dsDNA) sensor application. This paper, based graphene electrode opens the possibility of direct electrochemical analysis of analyte without any sample preparation. In this study, two irreversible oxide peaks were obtained from paper-based printed graphene electrode, corresponds to oxidation of guanine (G) and adenine (A) of dsDNA in the linear range of 0.2 pg mL−1 to 5 pg mL−1 with the detection limit of 0.68 pg mL−1 and the sensitivity of 0.00656 mA pg−1 cm−2. Further, a small-scale printable circuit is fabricated using this graphene shows good conductivity of 1.145x103(S/m).
183 citations
TL;DR: This investigation of the growth mechanism and temperature dependent Raman spectroscopy of chemical vapor deposited large area monolayer of MoS2, MoSe2, WS2 and WSe2 nanosheets shows that softening of Raman modes as temperature increases is due to the negative temperature coefficient and anharmonicity.
Abstract: We investigate the growth mechanism and temperature dependent Raman spectroscopy of chemical vapor deposited large area monolayer of MoS2, MoSe2, WS2 and WSe2 nanosheets up to 70 μm in lateral size. Further, our temperature dependent Raman spectroscopy investigation shows that softening of Raman modes as temperature increases from 80 K to 593 K is due to the negative temperature coefficient and anharmonicity. The temperature dependent softening modes of chemical vapor deposited monolayers of all TMDCs were explained on the basis of a double resonance phonon process which is more active in an atomically thin sample. This process can also be fundamentally pertinent in other emerging two-dimensional layered and heterostructured materials.
183 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