Chemically Derived, Ultrasmooth Graphene Nanoribbon Semiconductors

Li, Xiaolin; Wang, Xinran; Zhang, Li; Lee, Sang‐Won; Dai, Hongjie

doi:10.1126/science.1150878

Cited by 4,578 publications

(3,744 citation statements)

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“…Amongst the plethora of organic semiconductors available, polycyclic aromatic hydrocarbons (PAHs) have attracted increasing attention 1, 2, 3, 4, 5, 6. With respect to infinite graphene, PAHs show nonzero tunable bandgaps and are thus of use as chromophores in antennae7, 8, 9, 10, 11, 12 or emissive molecular architectures13, 14, 15, 16, 17, 18, 19 and in general in all optoelectronic applications requiring a tunable semiconducting material 6, 20.…”

Section: Introductionmentioning

confidence: 99%

Tailoring Colors by O Annulation of Polycyclic Aromatic Hydrocarbons

Miletić

Fermi

Orfanos

et al. 2017

Chemistry A European J

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The synthesis of O‐doped polyaromatic hydro‐ carbons in which two polycyclic aromatic hydrocarbon sub units are bridged through one or two O atoms has been achieved. This includes high‐yield ring‐closure key steps that, depending on the reaction conditions, result in the formation of furanyl or pyranopyranyl linkages through intramolecular C−O bond formation. Comprehensive photophysical measurements in solution showed that these compounds have exceptionally high emission yields and tunable absorption properties throughout the UV/Vis spectral region. Electrochemical investigations showed that in all cases O annulation increases the electron‐donor capabilities by raising the HOMO energy level, whereas the LUMO energy level is less affected. Moreover, third‐order nonlinear optical (NLO) measurements on solutions or thin films containing the dyes showed very good values of the second hyperpolarizability. Importantly, poly(methyl methacrylate) films containing the pyranopyranyl derivatives exhibited weak linear absorption and NLO absorption compared to the nonlinearity and NLO refraction, respectively, and thus revealed them to be exceptional organic materials for photonic devices.

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Section: Introductionmentioning

confidence: 99%

Tailoring Colors by O Annulation of Polycyclic Aromatic Hydrocarbons

Miletić

Fermi

Orfanos

et al. 2017

Chemistry A European J

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“…This work builds upon over fifty years of study into chemical exfoliation of graphite 16 . Previously, intercalated graphite could be partially exfoliated by reactions involving the intercalant 17 , through thermal shock 18 or by acid treatment of expandable graphite 19 . However, thus far, such methods give thin graphite sheets or graphene fragments 19 rather than large scale graphene mono-layers.…”

mentioning

confidence: 99%

“…Previously, intercalated graphite could be partially exfoliated by reactions involving the intercalant 17 , through thermal shock 18 or by acid treatment of expandable graphite 19 . However, thus far, such methods give thin graphite sheets or graphene fragments 19 rather than large scale graphene mono-layers. The standard response to this problem has been the compromise of complete exfoliation of chemically modified forms of graphene such as graphene oxide or functionalised graphene 12,14,20 .…”

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confidence: 99%

High-yield production of graphene by liquid-phase exfoliation of graphite

et al. 2008

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Graphene is at the centre of nanotechnology research. In order to fully exploit its outstanding properties, a mass production method is necessary. Two main routes are possible: large-scale growth or large-scale exfoliation. Here, we demonstrate graphene dispersions with concentrations up to ~0.01 mg/ml by dispersion and exfoliation of graphite in organic solvents such as N-methylpyrrolidone. This occurs because the energy required to exfoliate graphene is balanced by the solvent-graphene interaction for solvents whose surface energy matches that of graphene. We confirm the presence of individual graphene sheets with yields of up to 12% by mass, using absorption spectroscopy, transmission electron microscopy and electron diffraction. The absence of defects or oxides is confirmed by X-ray photoelectron, infra-red and Raman spectroscopies. We can produce conductive, semi-transparent films and conductive composites. Solution processing of graphene opens up a whole range of potential large-scale applications from device or sensor fabrication to liquid phase chemistry. Hernandez et al 2Graphene is one of the most exciting nano-materials due to the cascade of unique physical properties that have recently been demonstrated. For example, due to the details of its electronic structure, charge carriers in graphene behave as massless Dirac fermions 1 . Furthermore, novel effects such as an ambipolar field effect 2 , room temperature quantum Hall effect 3 , breakdown of the Born-Oppenheimer approximation 4 are observed. However, as was the case in the early days of nanotube and nanowire research, graphene at present still suffers from one problem, critical for its mass-scale exploitation: it cannot yet be made with high yield. The standard procedure used to make graphene is micromechanical cleavage 5 . This yields the best samples to date, with mobilities up to 200,000 cm 2 /Vs. 6 However, single layers are a negligible fraction amongst large quantities of thin graphite flakes. Furthermore, it is difficult to see how to scale up this process to mass production. Alternatively, growth of graphene is also commonly achieved by annealing SiC substrates, but these samples are in fact composed of a multitude of domains, most of them sub-micrometer, and not spatially uniform in number, or in size over larger length scales 7 . A number of works have also reported graphene growth on metal substrates 8,9 , but this would require the sample transfer to insulating substrates in order to make useful devices, either via mechanical transfer or, via solution processing.Recently, a large number of papers have described the dispersion and exfoliation of graphene oxide (GO) [10][11][12][13] . This material consists of graphene-like sheets, chemically functionalised with compounds such as hydroxyls and epoxides, which stabilise the sheets in water 14 . However, this functionalisation results in considerable disruption of the electronic structure of the graphene. In fact GO is an insulator 15 rather than a semi-metal and is conceptually differen...

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“…However, the application of graphene in logic6circuit6based devices such as transistors is so far limited because pure graphene is an excellent conductor or a zero6band6gap semiconductor, which effectively means such devices cannot be switched off. 11,12 Several approaches have been proposed to open a band gap in graphene, including the restriction of its physical dimensions into ribbons [13][14][15] and the introduction of defects or dopants. 15,16 More specifically the introduction of nitrogen or boron atoms in the graphene lattice is predicted to have a drastic effect on graphene's band structure and to lead to the opening of a band gap, thus resulting in n6 type 17,18 or p6type doping, 19,20 respectively, with carrier concentrations allowing practical transistor applications.…”

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confidence: 99%

Electronic Structure Modification of Ion Implanted Graphene: The Spectroscopic Signatures of p- and n-Type Doping

et al. 2015

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A combination of scanning transmission electron microscopy, electron energy loss spectroscopy, and ab initio calculations is used to describe the electronic structure modifications incurred by free6standing graphene through two types of single6atom doping. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 dopant atom shows an unusual broad asymmetric peak which is the result of delocalised π * states away from the B dopant. The asymmetry of the B K towards higher energies is attributed to highly6localised σ* anti6bonding states. These experimental observations are then interpreted as direct fingerprints of the expected p6 and n6type behaviour of graphene doped in this fashion, through careful comparison with density functional theory calculations. graphene, doping, electronic structure, STEM, EELS, ab5initio calculations, DFT

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Chemically Derived, Ultrasmooth Graphene Nanoribbon Semiconductors

Cited by 4,578 publications

References 26 publications

Tailoring Colors by O Annulation of Polycyclic Aromatic Hydrocarbons

Tailoring Colors by O Annulation of Polycyclic Aromatic Hydrocarbons

High-yield production of graphene by liquid-phase exfoliation of graphite

Electronic Structure Modification of Ion Implanted Graphene: The Spectroscopic Signatures of p- and n-Type Doping

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