Reductive Alkylation of Anthracite: Edge Functionalization

Sun, Yong; Kuznetsov, O. V.; Alemany, Lawrence B.; Billups, W. E.

doi:10.1021/ef200715n

Cited by 10 publications

(24 citation statements)

References 50 publications

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“…Support for assigning the relatively sharp signals at 67, 31, 57, and 18 ppm to residual tert ‐butyl alcohol and ethanol comes from combining the direct 13 C pulse experiment with dipolar dephasing (Figure ) . With a 50‐μs dephasing interval, the broad aliphatic signal essentially completely decays, but relatively sharp signals at 68, 66, 57, 36, 31, and 18 ppm remain.…”

Section: Resultsmentioning

confidence: 99%

Structural Characteristics and Properties of a New Graphitic‐Based Material

Vishnyakova

Brinson

Alemany

et al. 2016

Chemistry A European J

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The hydrogenation of commercial graphite using lithium/ammonia as the reducing agent and tert-butyl alcohol as a proton source was investigated. Characterization of the products after successive reductions of the same material by high-resolution transmission electron microscopy revealed a new material that was replete with edge and circular dislocations. Analysis by solid-state (13)C NMR spectroscopy indicates that after three reductions, the remaining aromatic rings appear to be interior benzene rings. NMR spectroscopy also offers strong evidence for the presence of small amounts of tert-butyl alcohol and ethanol (workup solvent) that could not be removed in vacuo from the samples. These compounds could be observed to move freely between the layers of the hydrographene.

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Section: Resultsmentioning

confidence: 99%

Structural Characteristics and Properties of a New Graphitic‐Based Material

Vishnyakova

Brinson

Alemany

et al. 2016

Chemistry A European J

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“…Indeed, a less dramatic shielding effect but much better resolution is observed with anthracite bearing dodecyl groups on the edges. 33 In contrast, the central methylene carbons in the methylene chains constrained to be above an aromatic ring in molecules such as [12]-paracyclophane 34 and various 1,n-dioxa[n](2,7)pyreneophanes 35 experience only a very small ring current shielding effect. The much weaker signal from the methyl carbons in the HD-GNRs is not recognizable.…”

Section: Resultsmentioning

confidence: 99%

In Situ Intercalation Replacement and Selective Functionalization of Graphene Nanoribbon Stacks

Genorio

Lü²,

Dimiev³

et al. 2012

ACS Nano

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177

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A cost-effective and potentially industrially scalable, in situ functionalization procedure for preparation of soluble graphene nanoribbon (GNRs) from commercially available carbon nanotubes is presented. The physical characteristics of the functionalized product were determined using SEM, evolved gas analysis, X-ray diffraction, solid-state (13)C NMR, Raman spectroscopy, and GC-MS analytical techniques. A relatively high preservation of electrical properties in the bulk material was observed. Moreover, replacement of intercalated potassium with haloalkanes was obtained. While carbon nanotubes can be covalently functionalized, the conversion of the sp(2)-hybridized carbon atoms to sp(3)-hybridized atoms dramatically lowers their conductivity, but edge functionalized GNRs permit their heavy functionalization while leaving the basal planes intact.

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“…The remarkable change in morphology that results upon adding hydrogen (or electrons) to graphene is evident upon inspection of the highresolution TEM images presented in Figure 4. The appearance of dislocations 58,59 is clearly visible in the exfoliated products that are formed during the Birch reductions. As the level of hydrogenation increased during the three reduction cycles, the distance between the graphitic layers in the (002) direction increased from 3.4 to 4.11 Å after the first reduction and to 4.29 Å after the third reduction.…”

Section: Reduction Of Synthetic Graphite Powdersmentioning

confidence: 99%

Structural Studies of Hydrographenes

et al. 2017

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As a result of the unique physical and electrical properties, graphene continues to attract the interest of a large segment of the scientific community. Since graphene does not occur naturally, the ability to exfoliate and isolate individual layers of graphene from graphite is an important and challenging process. The interlayer cohesive energy of graphite that results from van der Waals attractions has been determined experimentally to be 61 meV per carbon atom (61 meV/C atom). This requires the development of a method to overcome the strong attractive forces associated with graphite. The exfoliation process that we, and others, have investigated involves electron transfer into bulk graphite from intercalated lithium to yield lithium graphenide. The resulting graphenide can be reacted with various reagents to yield functionalized graphene. As a part of our interest in the functionalization of graphene, we have explored the Birch reduction as a route to hydrographenes. The addition of hydrogen transforms graphene into an insulator, leading to the prediction that important applications will emerge. This Account focuses mainly on the characterization of the hydrographenes that are obtained from different types of graphite including synthetic graphite powder, natural flake graphite, and annealed graphite powder. Analysis by solid stateC NMR spectroscopy proved to be important since it was shown that the hydrographenes are composed of interior, isolated aromatic (predominantly fully substituted benzene) rings surrounded by saturated rings. The expected clusters of benzene rings were not found. NMR spectroscopy also offers strong evidence for the presence of tert-butyl alcohol and ethanol (workup solvent) that could not be removed in vacuo from the samples. These compounds could be observed to move freely within the layers of the hydrographene. High-resolution transmission electron microscopy images revealed a remarkable change in morphology that results when hydrogen is added to the graphenide. The appearance of edge and circular dislocations and increased distances between graphitic layers are most visible in the case of the hydrographenes that are formed from annealed graphite. The repetitive hydrogenation of synthetic graphite powder leads to an increase in the distances between the graphitic layers in the (002) direction from 3.4 Å for the initial graphite to 4.11 Å after the first reduction and to 4.29 Å after a third reduction of the same material. Defect-free graphite is formed when the hydrographenes are heated. The distance between carbon layers decreases from 4.11 to 3.44 Å after heating the samples to 1200 °C. This trend toward the spacing of graphite confirms the reversibility of the functionalization process. The C-H bonds have been broken yielding hydrogen, and the exposed carbon orbitals are in close enough proximity to have reverted to graphite. This Account introduces only a narrow area of materials chemistry, and many applications of graphene and its derivatives can be expected as researchers exploi...

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Reductive Alkylation of Anthracite: Edge Functionalization

Cited by 10 publications

References 50 publications

Structural Characteristics and Properties of a New Graphitic‐Based Material

Structural Characteristics and Properties of a New Graphitic‐Based Material

In Situ Intercalation Replacement and Selective Functionalization of Graphene Nanoribbon Stacks

Structural Studies of Hydrographenes

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