High-yield production of graphene by liquid-phase exfoliation of graphite. Nat Nanotechnol

School of Physics, Trinity College Dublin, Dublin 2, Ireland.
Nature Nanotechnology (Impact Factor: 34.05). 10/2008; 3(9):563-8. DOI: 10.1038/nnano.2008.215
Source: PubMed


Fully exploiting the properties of graphene will require a method for the mass production of this remarkable material. Two main routes are possible: large-scale growth or large-scale exfoliation. Here, we demonstrate graphene dispersions with concentrations up to approximately 0.01 mg ml(-1), produced by dispersion and exfoliation of graphite in organic solvents such as N-methyl-pyrrolidone. This is possible because the energy required to exfoliate graphene is balanced by the solvent-graphene interaction for solvents whose surface energies match that of graphene. We confirm the presence of individual graphene sheets by Raman spectroscopy, transmission electron microscopy and electron diffraction. Our method results in a monolayer yield of approximately 1 wt%, which could potentially be improved to 7-12 wt% with further processing. The absence of defects or oxides is confirmed by X-ray photoelectron, infrared and Raman spectroscopies. We are able to produce semi-transparent conducting films and conducting composites. Solution processing of graphene opens up a range of potential large-area applications, from device and sensor fabrication to liquid-phase chemistry.

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    • "Till date, several methodologies have been demonstrated for the synthesis of graphene and graphene‐derived materials. To name a few are mechanical cleaving (exfoliation) [1], chemical exfoliation [22], chemical synthesis [23], thermal CVD synthesis [25] [27], and epitaxial growth [24] methods. Besides these, several other processes are also demonstrated such as unzipping of CNT [28] [29], electrochemical exfoliation [30], laser ablation process, and several others [31]. "
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    Full-text · Book · Oct 2015
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    • "As reported in the literature, the dispersion/exfoliation of graphite is favoured by the specific interactions occurring between the solvent – in this case the polymer – and the graphene sheets. Indeed, it was demonstrated by Hernandez et al. [24] that the exfoliation of graphite occurs for solvents whose surface energy matches that of graphene. In the case of PCL, the surface tension of the molten polymer (51 mN/m) is in the range of that of solvents, such as N-methyl-2-pyrrolidone (NMP) and dimethylformamide (DMF), characterized by a high capacity of exfoliating the graphite. "
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    ABSTRACT: In this work, novel graphite-based composites consisting of poly(l-lactide) (PLLA) and poly(ε-caprolactone) (PCL) immiscible blends are developed by means of a simple and low-environmental-impact method, which does not require the use of either solvents or graphite oxide. Indeed, the proposed approach relies on the preliminary dispersion of a high surface area graphite (HSAG) in the molten PCL by applying a sonication treatment: as a consequent of this processing, the HSAG turns out to be dispersed in the polymer matrix at a sub-micrometer level and acts as a nucleating agent for the PCL crystallization. The PCL/HSAG system (whose filler content is adjusted so as to prepare blends with final HSAG concentrations ranging from 0.1 to 0.6 wt.%) is subsequently introduced in PLLA through melt blending. SEM characterization demonstrates that the presence of HSAG modifies the morphology of the blend. In particular, at a characteristic HSAG concentration, namely 0.1 wt.%, the filler is observed to ameliorate significantly the compatibility of PLLA/PCL blends by increasing the interface adhesion between the two polymer phases.
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    • "Selected-area electron diffraction (SAED) was performed on a smooth region to determine its crystalline nature (Fig. 1a inset). The diffraction dots were fully indexed to the hexagonal graphite crystal structure, which was similar to that of single-layer graphene prepared by manual peeling off from graphite, confirming the crystalline structure of graphene-sheet [22] [23]. Some few-layer AA-GN was also observed in the sample as showed in TEM (Fig. S1a in Supporting information). "
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