Solution Properties of Graphite and Graphene

Niyogi, Sandip; Bekyarova, Elena; Itkis, Mikhail E.; Mcwilliams, Jared L.; Hamon, Mark A.; Haddon, Robert C.

doi:10.1021/ja060680r

Cited by 1,232 publications

(722 citation statements)

References 27 publications

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“…The significant loss in intensity and shift of the C=O vibration from 1718 cm -1 in the starting methoxyphenyl azido formate to 1734 cm -1 in the bound molecule is consistent with covalent bonding. 10,11 Thus, the presence of the molecular signature of the MPC molecule along with additional bonding features strongly supports the assertion of covalent nitrene addition to the h-BN lattice. H-NMR was also used to characterize the MPCfunctionalized h-BN.…”

Section: Figure 2 Ftir Spectra Of A) Pristine H-bn B) Methoxybenzylsupporting

confidence: 54%

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Covalently Functionalized Hexagonal Boron Nitride Nanosheets by Nitrene Addition

Sainsbury

Satti

May

et al. 2012

Chemistry A European J

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Exfoliated h-BN nanosheets were covalently functionalized via a one-step nitrene addition using azide precursor molecules. Functionalized h-BN nanosheets were found to exhibit markedly enhanced dispersability relative to pristine h-BN in a range of organic solvents. Extension of the functionalization methodology allowed the covalent attachment of polymer chains to the surface of h-BN nanosheets. Polymer nanocomposites were prepared using the molecularly-functionalized h-BN nanosheets within a polycarbonate (PC) matrix, while h-BN nanosheets functionalized with poly(bisphenol A-co-epichlorohydrin) (PBCE) chains were employed within a PBCE matrix. In both cases the mechanical properties were studied. Significant increases in moduli, strength and ductility of the functionalized h-BN nanocomposites indicated enhanced reinforcement of the functionalized h-BN filler materials over pristine h-BN. The implications of tuning the surface chemistry of exfoliated nanosheets exactly to the chemistry of a host polymer matrix are considered.Due to its exciting electrical, thermal and mechanical properties, 1 the last few years have seen a surge of interest in the exfoliation of graphene. 2,3 More recently, attention has shifted to other layered compounds, notably hexagonal boron nitride (h-BN) and the transition metal dichalcogenides. [4][5][6]

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Section: Figure 2 Ftir Spectra Of A) Pristine H-bn B) Methoxybenzylsupporting

confidence: 54%

“…In contrast, a number of groups have described the covalent modification of graphene. 10,11 This is important as such modification can impart chemical functionality and facilitate integration of the exfoliated material within polymer systems. Due to the high intrinsic strength of h-BN, 12 such systems could be the basis of future high performance composites.…”

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confidence: 99%

Covalently Functionalized Hexagonal Boron Nitride Nanosheets by Nitrene Addition

Sainsbury

Satti

May

et al. 2012

Chemistry A European J

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“…The most common technique has been the oxidisation and subsequent exfoliation of graphite to give graphene oxide. [3][4][5][6][7] However, this technique suffers from one significant disadvantage; the oxidisation process results in the formation of structural defects as evidenced by Raman spectroscopy 3,6 . These defects alter the electronic structure of graphene so much as to render it semiconducting 8 .…”

Section: Introductionmentioning

confidence: 99%

Liquid Phase Production of Graphene by Exfoliation of Graphite in Surfactant/Water Solutions

et al. 2009

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We have demonstrated a method to disperse and exfoliate graphite to give graphene suspended in water-surfactant solutions. Optical characterisation of these suspensions allowed the partial optimisation of the dispersion process. Transmission electron microscopy showed the dispersed phase to consist of small graphitic flakes. More than 40% of these flakes had <5 layers with ~3% of flakes consisting of monolayers. These flakes are stabilised against reaggregation by Coulomb repulsion due to the adsorbed surfactant. However, the larger flakes tend to sediment out over ~6 weeks, leaving only small flakes dispersed. It is possible to form thin films by vacuum filtration of these dispersions. Raman and IR spectroscopic analysis of these films suggests the flakes to be largely free of defects and oxides. The deposited films are reasonably conductive and are semi-transparent. Further improvements may result in the development of cheap transparent conductors.

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“…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 . However such materials are not graphene as they are insulators containing numerous structural defects 14,20 , which cannot, so far, be fully removed by chemical treatment 14 .…”

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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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Solution Properties of Graphite and Graphene

Cited by 1,232 publications

References 27 publications

Covalently Functionalized Hexagonal Boron Nitride Nanosheets by Nitrene Addition

Covalently Functionalized Hexagonal Boron Nitride Nanosheets by Nitrene Addition

Liquid Phase Production of Graphene by Exfoliation of Graphite in Surfactant/Water Solutions

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

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