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

ABSTRACT 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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Available from: Yenny Hernandez, Sep 28, 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.
    European Polymer Journal 09/2015; 70. DOI:10.1016/j.eurpolymj.2015.06.016 · 3.01 Impact Factor
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    • "The graphene and FLG solution was produced following the scalable liquid-phase exfoliation (LPE) method [38] [39]. The functionalization was achieved via the recipe previously developed for CNTs used in magnetic and biomedical applications [40] [41]. "
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    ABSTRACT: We report on heat conduction properties of thermal interface materials with self-aligning "magnetic grapheme" fillers. Graphene enhanced nano-composites were synthesized by an inexpensive and scalable technique based on liquid-phase exfoliation. Functionalization of graphene and few-layer-graphene flakes with Fe3O4 nanoparticles allowed us to align the fillers in an external magnetic field during dispersion of the thermal paste to the connecting surfaces. The filler alignment results in a strong increase of the apparent thermal conductivity and thermal diffusivity through the layer of nano-composite inserted between two metallic surfaces. The self-aligning "magnetic grapheme" fillers improve heat conduction in composites with both curing and non-curing matrix materials. The thermal conductivity enhancement with the oriented fillers is a factor of two larger than that with the random fillers even at the low ~1 wt. % of graphene loading. The real-life testing with computer chips demonstrated the temperature rise decrease by as much as 10oC with use of the non-curing thermal interface material with ~1 wt. % of the oriented fillers. Our proof-of-concept experiments suggest that the thermal interface materials with functionalized graphene and few-layer-graphene fillers, which can be oriented during the composite application to the surfaces, can lead to a new method of thermal management of advanced electronics.
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    • "Different approaches have been developed for the synthesis of graphene, such as mechanical cleavage (Novoselov et al., 2004; Novoselov et al., 2005), epitaxial growth (Forbeaux et al., 1998; Cambaz et al., 2008), chemical vapour deposition (Kim et al., 2009; Li et al., 2009), electrochemical exfoliation of graphite (Wang et al., 2011; Lu et al., 2009; Qi et al., 2011; Liu et al., 2008) and reduction of GO that is derived from chemical exfoliation of graphite (Compton et al., 2011). Recently non-covalent exfoliation of graphite by sonication in liquid phase has also been reported (Hernandez et al., 2008; Xia et al., 2013). Of all these approaches, the reduction of GO is regarded as one of the most promising routes for the mass production of graphene at a low cost and with high yield, although only partially restore the properties of pristine graphene. "
    Arabian Journal of Chemistry 07/2015; DOI:10.1016/j.arabjc.2015.07.015 · 3.73 Impact Factor
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