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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Available from: Yenny Hernandez,
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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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    ABSTRACT: This chapter summarizes the graphene synthesis processes, including mechanical, chemical, and epitaxial growth process together with the detailed discussion of process parameters and their feasibility. Chemical synthesis of graphene is a top-down indirect synthesis method of graphene and, more preciously, first ever method that demonstrated the graphene synthesis by chemical route. The chapter introduces a bottom-up approach of chemical synthesis of graphene, named as solvothermal method. Epitaxial thermal synthesis process of graphene on single-crystalline silicon carbide (SiC) surface is one of the most renowned synthesis processes. The chapter summarizes the characterization methods based on various microscopic and spectroscopic techniques, which are basically used to evaluate graphene fingerprints. Despite the presence of noninvasive techniques such as optical and Raman spectroscopy, high resolution transmission electron microscopy (HRTEM) is one of the very powerful, frequently used, reliable characterization techniques for graphene's structural characterizations.
    2015 edited by Wen Lu, Jong-Beom Baek andLiming Dai, 10/2015; Wiley., ISBN: 9781118580783
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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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    • "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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    ABSTRACT: A B S T R A C T Oxidation of dopamine (DA) at classical electrodes is suggested to go through three steps and then form melanin-like compounds, which would inhibit electron transfer and result in the fouling of electrode. In addition, the selective oxidation of DA in the presence of ascorbate (VC) should also be considered for the design of electrode. Here, graphenes modified with different surface groups are used to investigate the oxidation behaviour of DA. Compared with classical electrodes, negatively charged few-layer graphene (AA-GN) shows a good performance in selective oxidation of DA and can also control the oxidation of DA in the first step, which would further prevent the fouling of electrode. The rate constant and number of electron transfer are calculated to be about 7.38 s À1 and 2, respectively, which further indicates that the oxidation of DA was controlled in the first step. Furthermore, AA-GN-modified electrode is used to selectively detect DA with a detection limit of 10 nM in the prescence of excess VC. At last, AA-GN-modified macro-electrode is used to monitor DA release from living cells for the first time.
    Electrochimica Acta 09/2015; 180. DOI:10.1016/j.electacta.2015.08.075 · 4.50 Impact Factor
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