Article pubs.acs.org/JPCC
Lipid Enhanced Exfoliation for Production of Graphene Nanosheets ̌ rǒ vá,† Karolína Machalová Šišková,† Petr Jurečka,† Athanasios B. Bourlinos,‡ Martin Pykal,† Klára Safá † Radek Zbořil, and Michal Otyepka†,* †
Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacký University Olomouc, 17. Listopadu 12, 771 46 Olomouc, Czech Republic ‡ Physics Department, University of Ioannina, 45110 Ioannina, Greece S Supporting Information *
ABSTRACT: Liquid-phase exfoliation of graphite is a widely used method to obtain graphene nanosheets, and therefore the development of a simple and efficient exfoliation procedure remains challenging. Here, we present a one-step method of graphene exfoliation in lecithin/chloroform solution. The graphene nanosheets produced by the lecithin assisted exfoliation method were analyzed by microscopy techniques, including statistical analysis of atomic force microscopy (AFM) images and Raman spectroscopy, which both indicate the presence of few-layer graphene nanosheets, including substantial content of three-layer sheets. Molecular dynamics simulations on the time scale of 0.5+ μs suggested that stability of the obtained colloid may originate from formation of lecithin reverse hemimicelles and micelles, which prevents the aggregation of exfoliated graphene flakes by entropic repulsion of the lipid hydrophobic chains.
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INTRODUCTION Defect-free graphene nanosheets have great potential in nanoelectronics, solar cells, and mechanical reinforcement of polymers.1,2 In particular, the AB-stacked bilayer and trilayer graphene is believed to have great potential for future nanoelectronic devices.3−6 The liquid-phase exfoliation of graphite in a solvent under mild sonication presents a widespread technique for the efficient production of solventprocessable, high quality graphene nanosheets.7,8 Interestingly, solvent extraction may be further assisted by the presence of exfoliants dissolved in the liquid-phase and having strong affinity to the graphene surface through noncovalent interactions, like certain surfactant or polymer additives.9,10 Generally, these additives improve the exfoliation yield and help to split the thick graphite plates into the thinnest possible flakes (
