High-yield production of graphene by liquid-phase exfoliation of graphite

Article (PDF Available)inNature Nanotechnology 3(9):563-8 · October 2008with1,332 Reads
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.
    • "Before performing the LPE process , the powder-like BP is dispersed in 100 mL of CHP (Sigma Aldrich, boiling point: 284 @BULLET C) and dispersed by using an ultrasonic bath for 6 h. The ultra-sonicated BP in CHP solution is then centrifuged at ∼560g in a Sigma 3–16KL centrifuge for 180 min, exploiting the sedimentation-based separation (SBS) pro- cess [11,56,61,[65][66][67]68], to separate thick and/or un-exfoliated BP flakes from the thinner ones. "
    [Show abstract] [Hide abstract] ABSTRACT: Recently, the re-discovered black phosphorus (BP) has been extensively investigated for both electronic and photonic applications. However, the intrinsic instability of BP caused by moisture or oxygen reaction in ambient atmosphere has overshadowed its practical applications. Here, we present a liquid phase exfoliation-based approach for the production of few-layer BP (FL-BP) and the subsequent mixing with polycarbonate (PC) for the fabrication of a composite, which significantly reduces BP degradation by PC passivation. Experimentally, the functionalized PC few-layer BP (PC/FL-BP) composite shows environmental stability if compared with mechanically exfoliated BP flakes. We then use the PC/FL-BP composite as saturable absorber to study the nonlinear absorption property in a fibre laser at the 1.55 μm telecommunication wavelength. A Q-switched laser with pulse energy up to 25.2 nJ and pulse duration down to 1.65 μs is obtained at a low pump power of 71.7 mW. Our results can boost further research and scalable photonic applications, where environmentally stable few-layer BP based devices are needed.
    Full-text · Article · Sep 2016 · Sensors
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    Article · Aug 2016
    Rui-Tao LiuRui-Tao LiuLu-Qi TaoLu-Qi TaoBo LiuBo Liu+1more author...[...]
    • "Chemical exfoliation of graphene using Hummers' method is attractive for producing solution-processed graphene oxide (GO), but subsequent chemical or thermal treatments can only partially remove its oxygen content so that electrical properties cannot be fully restored [9][8]. Numerous other synthesis techniques have been developed to overcome these limitations, including solvent-assisted Liquid-Phase Exfoliation (LPE) [10][8] or the formation of graphite intercalation compounds [11], but extensive sonication processes are required that limit the size and yield of thin graphene flakes [4]. Furthermore, due to its low solubility, the exfoliated graphene is usually dispersed in high-boiling-point solvents, which creates difficulties for subsequent film preparation. "
    [Show abstract] [Hide abstract] ABSTRACT: INTRODUCTION Graphene, a two-dimensional honeycomb sp 2 carbon lattice has received enormous attention because of the potential for various applications such as the electrodes of photovoltaic devices and batteries, next generation flexible electronics and even antibacterial coatings [1][2]. Interest in the application of graphene is mainly due to its high electrical conductivity, flexibility and huge tuneability of the properties of graphene-based materials [3][4]. For example, the semi-metal character of pristine graphene can be changed to semiconducting [5], insulating [6] or superconducting [7] by control of size or chemical functionalization. To utilize graphene's unique properties and potential adaptability, several graphene synthesis methods have been developed. Mechanical exfoliation is the earliest technique to isolate monolayer graphene, but the yields are limited. Chemical Vapour Deposition (CVD) epitaxial growth exploits catalytic metal substrates such as Ni or Cu and can produce large area and high-quality graphene directly on the substrate, but the requirements of high temperature and the multi-step transferral process are major difficulties for cheap, industrial-scale production [4][8]. Chemical exfoliation of graphene using Hummers' method is attractive for producing solution-processed graphene oxide (GO), but subsequent chemical or thermal treatments can only partially remove its oxygen content so that electrical properties cannot be fully restored [9][8]. Numerous other synthesis techniques have been developed to overcome these limitations, including solvent-assisted Liquid-Phase Exfoliation (LPE) [10][8] or the formation of graphite intercalation compounds [11], but extensive sonication processes are required that limit the size and yield of thin graphene flakes [4]. Furthermore, due to its low solubility, the exfoliated graphene is usually dispersed in high-boiling-point solvents, which creates difficulties for subsequent film preparation. Therefore a low-cost, solution-processable method that can lead to high-quality graphene film is desirable [4]. In this work, we intend to compare the properties of graphene flakes manufactured from Liquid Phase Exfoliation (LPE) and electrochemical exfoliation (ECE) of graphite. The electrochemical exfoliation of graphite is performed in dilute sulphuric acid, the resulting electrochemically exfoliated graphene flakes (EG) were characterized by Raman spectroscopy, Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM) and Selective Area Electron Diffraction (SAED), and compared with the raw material and also with Liquid Phase Exfoliated (LPE) graphene. The results reveal that high-quality graphene flakes can be obtained from this and simple, fast and cost-effective electrochemical exfoliation approach.
    Full-text · Conference Paper · Jul 2016 · Sensors
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