Liquid exfoliation of defect-free graphene.

By Jonathan N. Coleman. Accounts of Chemical Research, 2013

914 citations recorded by the source corpus.

Due to its unprecedented physical properties, graphene has generated huge interest over the last 7 years. Graphene is generally fabricated in one of two ways: as very high quality sheets produced in limited quantities by micromechanical cleavage or vapor growth or as a rather defective, graphene-like material, graphene oxide, produced in large quantities. However, a growing number of applications would profit from the availability of a method to produce high-quality graphene in large quantities. This Account describes recent work to develop such a processing route inspired by previous theoretical and experimental studies on the solvent dispersion of carbon nanotubes. That work had shown that nanotubes could be effectively dispersed in solvents whose surface energy matched that of the nanotubes. We describe the application of the same approach to the exfoliation of graphite to give graphene in a range of solvents. When graphite powder is exposed to ultrasonication in the presence of a suitable solvent, the powder fragments into nanosheets, which are stabilized against aggregation by the solvent. The enthalpy of mixing is minimized for solvents with surface energies close to that of graphene (∼68 mJ/m(2)). The exfoliated nanosheets are free of defects and oxides and can be produced in large quantities. Once solvent exfoliation is possible, the process can be optimized and the nanosheets can be separated by size. The use of surfactants can also stabilize exfoliated graphene in water, where the ζ potential of the surfactant-coated graphene nanosheets controls the dispersed concentration. Liquid exfoliated graphene can be used for a range of applications: graphene dispersions as optical limiters, films of graphene flakes as transparent conductors or sensors, and exfoliated graphene as a mechanical reinforcement for polymer-based composites. Finally, we have extended this process to exfoliate other layered compounds such as BN and MoS(2). Such materials will be important in a range of applications from thermoelectrics to battery electrodes. This liquid exfoliation technique can be applied to a wide range of materials and has the potential to be scaled up into an industrial process. We believe the coming decade will see an explosion in the applications involving liquid exfoliated two-dimensional materials.

Subfields: Electrical and Electronic Engineering, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/0d0c98816b8b32109ef188b7388b2d4a4894d9bd

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Citations in the corpus

Guidelines for Exfoliation, Characterization and Processing of Layered Materials Produced by Liquid Exfoliation (2017, background): “In each case, interactions at the liquid - nanosheet interface reduce the net exfoliation energy and stabilize the nanosheets against aggregation.(19) The resultant dispersions are quite stable and can be produced at concentrations(20) exceeding 1 gL.”
A manufacturing perspective on graphene dispersions (2015, background): “The theoretical surface area ofmonolayer graphene is ~2590m(2) g [12]; consequently there are a limited range of conditions under which it can be dispersed typically involving sonication and polar aprotic solvents [13].”
Determination of ascorbic acid, dopamine, and uric acid by a novel electrochemical sensor based on pristine graphene (2015, methodology): “To date, there are three basic methods to prepare graphene: mechanical cleavage method [1], Hummers method [2], and liquid phase exfoliation method [3,4].”