Structure of Graphite Oxide Revisited
13 May 1998-Journal of Physical Chemistry B (American Chemical Society)-Vol. 102, Iss: 23, pp 4477-4482
TL;DR: In this paper, the authors used 13C and 1H NMR spectra of graphite oxide derivatives to confirm the assignment of the 70 ppm line to C−OH groups and allow them to propose a new structural model for graphite oxides.
Abstract: Graphite oxide (GO) and its derivatives have been studied using 13C and 1H NMR. NMR spectra of GO derivatives confirm the assignment of the 70 ppm line to C−OH groups and allow us to propose a new structural model for GO. Thus we assign the 60 ppm line to epoxide groups (1,2-ethers) and not to 1,3-ethers, as suggested earlier, and the 130 ppm line to aromatic entities and conjugated double bonds. GO contains two kinds of regions: aromatic regions with unoxidized benzene rings and regions with aliphatic six-membered rings. The relative size of the two regions depends on the degree of oxidation. The carbon grid is nearly flat; only the carbons attached to OH groups have a slightly distorted tetrahedral configuration, resulting in some wrinkling of the layers. The formation of phenol (or aromatic diol) groups during deoxygenation indicates that the epoxide and the C−OH groups are very close to one another. The distribution of functional groups in every oxidized aromatic ring need not be identical, and both ...
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TL;DR: In this paper, a colloidal suspension of exfoliated graphene oxide sheets in water with hydrazine hydrate results in their aggregation and subsequent formation of a high surface area carbon material which consists of thin graphene-based sheets.
12,756 citations
Cites background from "Structure of Graphite Oxide Revisit..."
...Although GO is thermally unstable and starts to lose mass upon heating even below 100 C, the major mass loss occurs at 200 C, presumably due to pyrolysis of the labile oxygen-containing functional groups, yielding CO, CO2, and steam [27,44]....
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TL;DR: The bottom-up chemical approach of tuning the graphene sheet properties provides a path to a broad new class of graphene-based materials and their use in a variety of applications.
Abstract: The remarkable mechanical properties of carbon nanotubes arise from the exceptional strength and stiffness of the atomically thin carbon sheets (graphene) from which they are formed. In contrast, bulk graphite, a polycrystalline material, has low fracture strength and tends to suffer failure either by delamination of graphene sheets or at grain boundaries between the crystals. Now Stankovich et al. have produced an inexpensive polymer-matrix composite by separating graphene sheets from graphite and chemically tuning them. The material contains dispersed graphene sheets and offers access to a broad range of useful thermal, electrical and mechanical properties. Individual sheets of graphene can be readily incorporated into a polymer matrix, giving rise to composite materials having potentially useful electronic properties. Graphene sheets—one-atom-thick two-dimensional layers of sp2-bonded carbon—are predicted to have a range of unusual properties. Their thermal conductivity and mechanical stiffness may rival the remarkable in-plane values for graphite (∼3,000 W m-1 K-1 and 1,060 GPa, respectively); their fracture strength should be comparable to that of carbon nanotubes for similar types of defects1,2,3; and recent studies have shown that individual graphene sheets have extraordinary electronic transport properties4,5,6,7,8. One possible route to harnessing these properties for applications would be to incorporate graphene sheets in a composite material. The manufacturing of such composites requires not only that graphene sheets be produced on a sufficient scale but that they also be incorporated, and homogeneously distributed, into various matrices. Graphite, inexpensive and available in large quantity, unfortunately does not readily exfoliate to yield individual graphene sheets. Here we present a general approach for the preparation of graphene-polymer composites via complete exfoliation of graphite9 and molecular-level dispersion of individual, chemically modified graphene sheets within polymer hosts. A polystyrene–graphene composite formed by this route exhibits a percolation threshold10 of ∼0.1 volume per cent for room-temperature electrical conductivity, the lowest reported value for any carbon-based composite except for those involving carbon nanotubes11; at only 1 volume per cent, this composite has a conductivity of ∼0.1 S m-1, sufficient for many electrical applications12. Our bottom-up chemical approach of tuning the graphene sheet properties provides a path to a broad new class of graphene-based materials and their use in a variety of applications.
11,866 citations
TL;DR: This review will be of value to synthetic chemists interested in this emerging field of materials science, as well as those investigating applications of graphene who would find a more thorough treatment of the chemistry of graphene oxide useful in understanding the scope and limitations of current approaches which utilize this material.
Abstract: The chemistry of graphene oxide is discussed in this critical review Particular emphasis is directed toward the synthesis of graphene oxide, as well as its structure Graphene oxide as a substrate for a variety of chemical transformations, including its reduction to graphene-like materials, is also discussed This review will be of value to synthetic chemists interested in this emerging field of materials science, as well as those investigating applications of graphene who would find a more thorough treatment of the chemistry of graphene oxide useful in understanding the scope and limitations of current approaches which utilize this material (91 references)
10,126 citations
TL;DR: An improved method for the preparation of graphene oxide (GO) is described, finding that excluding the NaNO(3), increasing the amount of KMnO(4), and performing the reaction in a 9:1 mixture of H(2)SO(4)/H(3)PO(4) improves the efficiency of the oxidation process.
Abstract: An improved method for the preparation of graphene oxide (GO) is described. Currently, Hummers’ method (KMnO4, NaNO3, H2SO4) is the most common method used for preparing graphene oxide. We have found that excluding the NaNO3, increasing the amount of KMnO4, and performing the reaction in a 9:1 mixture of H2SO4/H3PO4 improves the efficiency of the oxidation process. This improved method provides a greater amount of hydrophilic oxidized graphene material as compared to Hummers’ method or Hummers’ method with additional KMnO4. Moreover, even though the GO produced by our method is more oxidized than that prepared by Hummers’ method, when both are reduced in the same chamber with hydrazine, chemically converted graphene (CCG) produced from this new method is equivalent in its electrical conductivity. In contrast to Hummers’ method, the new method does not generate toxic gas and the temperature is easily controlled. This improved synthesis of GO may be important for large-scale production of GO as well as the ...
9,812 citations
TL;DR: It is reported that chemically converted graphene sheets obtained from graphite can readily form stable aqueous colloids through electrostatic stabilization, making it possible to process graphene materials using low-cost solution processing techniques, opening up enormous opportunities to use this unique carbon nanostructure for many technological applications.
Abstract: Graphene sheets offer extraordinary electronic, thermal and mechanical properties and are expected to find a variety of applications. A prerequisite for exploiting most proposed applications for graphene is the availability of processable graphene sheets in large quantities. The direct dispersion of hydrophobic graphite or graphene sheets in water without the assistance of dispersing agents has generally been considered to be an insurmountable challenge. Here we report that chemically converted graphene sheets obtained from graphite can readily form stable aqueous colloids through electrostatic stabilization. This discovery has enabled us to develop a facile approach to large-scale production of aqueous graphene dispersions without the need for polymeric or surfactant stabilizers. Our findings make it possible to process graphene materials using low-cost solution processing techniques, opening up enormous opportunities to use this unique carbon nanostructure for many technological applications.
8,534 citations
Cites background from "Structure of Graphite Oxide Revisit..."
...2 a), apparently as a result of ionization of the carboxylic acid and phenolic hydroxyl groups that are known to exist on the GO sheet...
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References
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26,456 citations
1,635 citations
01 Jan 2005
TL;DR: In this paper, the authors describe a method for infuhrung in the Schwingungsspektroskopie (IR) in the Uber-blick.
Abstract: Spektroskopische Methoden im Uberblick 3-9 Einfuhrung in die Schwingungsspektroskopie (IR) 10-19 Mechanismen der Schwingungsanregung 20-23 Prinzip der Raman-Spektroskopie 24-30 Schwingungsfrequenz 31-39 Grundschwingungen und Schwingungen hoherer Ordnung 40-44 Spektreninterpretation 45-62 Molekulsymmetrie und Schwingungsaktivitat 63-81
930 citations
TL;DR: In this paper, the 13C NMR lines at 60, 70, and 130 ppm were assigned to C−OH, C−O−C, and >CC CC< double bonds.
Abstract: Graphite oxide (GO) and its derivatives have been studied using 13C and 1H NMR. The 13C NMR lines at 60, 70, and 130 ppm are assigned to C−OH, C−O−C, and >CC CC< double bonds are relatively stable, while C−OH groups may condense to form C−O−C (ether) linkages. There are at least two magnetically inequivalent C−OH sites, and the structure does not necessarily possess long-range order. Water molecules interact very strongly with the structure. The results reveal a number of new structural features.
408 citations