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Production of ready-to-use few-layer graphene in aqueous suspensions

Nature Protocols volume 13, pages 495–506 (2018)Cite this article

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Abstract

Graphene has promising physical and chemical properties such as high strength and flexibility, coupled with high electrical and thermal conductivities. It is therefore being incorporated into polymer-based composites for use in electronics and photonics applications. A main constraint related to the graphene development is that, being of a strongly hydrophobic nature, almost all dispersions (usually required for its handling and processing toward the desired application) are prepared in poisonous organic solvents such as N-methyl pyrrolidone or N,N-dimethyl formamide. Here, we describe how to prepare exfoliated graphite using a ball mill. The graphene produced is three to four layers thick and ∼500 nm in diameter on average, as measured by electron microscopy and Raman spectroscopy; can be stored in the form of light solid; and is easily dispersed in aqueous media. Our methodology consists of four main steps: (i) the mechanochemical intercalation of organic molecules (melamine) into graphite, followed by suspension in water; (ii) the washing of suspended graphene to eliminate most of the melamine; (iii) the isolation of stable graphene sheets; and (iv) freeze–drying to obtain graphene powder. This process takes 6–7 or 9–10 d for aqueous suspensions and dry powders, respectively. The product has well-defined properties and can be used for many science and technology applications, including toxicology impact assessment and the production of innovative medical devices.

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Figure 1: Roadmap for releasing the solid mixture from the milling container by sonication in ultrapure water.
Figure 2: Images of the melamine washing process.
Figure 3: Photographs of the process of extracting stable graphene sheets in water after the sedimentation process.
Figure 4
Figure 5: Visual and spectroscopic characterization of the aqueous few-layer graphene.
Figure 6: Chemical characterization of graphene in powder form.
Figure 7: Structural and morphological characterization of graphene flakes.

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Acknowledgements

We acknowledge financial support from the Spanish Ministry of Economy and Competitiveness (MINECO; projects CTQ2014-53600-R and CTQ2016-76721-R), through the EU Graphene-based disruptive technologies Flagship project (no. 696656). J.M.G.-D. gratefully acknowledges Spanish MINECO for his research grant (Formación Postdoctoral). M.P., as the recipient of the AXA Chair, is grateful to the AXA Research Fund for financial support. M.P. was also supported by Diputación Foral de Gipuzkoa (Spain), program Red (101/16).

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Author notes

  1. Jose M González-Domínguez, Verónica León and María Isabel Lucío: These authors contributed equally to this work.

Authors and Affiliations

  1. Department of Organic Chemistry, Faculty of Chemical Science and Technology-IRICA, University of Castilla-La Mancha, Ciudad Real, Spain

    Jose M González-Domínguez, Verónica León, María Isabel Lucío & Ester Vázquez

  2. Department of Chemical and Pharmaceutical Sciences, University of Trieste, Trieste, Italy

    Maurizio Prato

  3. Carbon Nanobiotechnology Laboratory CIC BiomaGUNE, Donostia-San Sebastián, Spain

    Maurizio Prato

  4. Basque Foundation for Science (IKERBASQUE), Bilbao, Spain

    Maurizio Prato

Authors
  1. Jose M González-Domínguez
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  2. Verónica León
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  3. María Isabel Lucío
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  4. Maurizio Prato
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Contributions

J.M.G.-D., V.L., and M.I.L. contributed equally to this work. J.M.G.-D., V.L., and M.I.L. performed the experimental work and optimized the protocol. M.P. contributed to the research plan and to the writing of the manuscript. E.V. planned and supervised the research, and cowrote the paper with contributions from all the other authors. All authors discussed the results and commented the manuscript.

Corresponding authors

Correspondence to Maurizio Prato or Ester Vázquez.

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The authors declare no competing financial interests.

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González-Domínguez, J., León, V., Lucío, M. et al. Production of ready-to-use few-layer graphene in aqueous suspensions. Nat Protoc 13, 495–506 (2018). https://doi.org/10.1038/nprot.2017.142

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