Spontaneous high-concentration dispersions and liquid crystals of graphene

Abstract

Graphene combines unique electronic properties and surprising quantum effects with outstanding thermal and mechanical properties. Many potential applications, including electronics and nanocomposites, require that graphene be dispersed and processed in a fluid phase. Here, we show that graphite spontaneously exfoliates into single-layer graphene in chlorosulphonic acid, and dissolves at isotropic concentrations as high as approximately 2 mg ml(-1), which is an order of magnitude higher than previously reported values. This occurs without the need for covalent functionalization, surfactant stabilization, or sonication, which can compromise the properties of graphene or reduce flake size. We also report spontaneous formation of liquid-crystalline phases at high concentrations ( approximately 20-30 mg ml(-1)). Transparent, conducting films are produced from these dispersions at 1,000 Omega square(-1) and approximately 80% transparency. High-concentration solutions, both isotropic and liquid crystalline, could be particularly useful for making flexible electronics as well as multifunctional fibres.

Nanotomy-based production of transferable and dispersible graphene nanostructures of controlled shape and size

“…3h). This is consistent with the earlier results reported for graphene dispersions in superacid 20 , organic and inorganic solvents 24,31 . The quality of the as-produced GNRs was also investigated using Raman spectroscopy (514.5 nm; < 5 mW) 32 .…”

“…The vials were subsequently placed in a shaker (inside the glove box) for ~8 h at room temperature and the exfoliation process was allowed to run to completion, inferred by dark black colour of the suspension phase with no solid residue. For characterization purposes, the GNR suspension was quenched in DI water (1:200) as per the procedure described by Behabtu et al 20 .…”

“…For GQDs, the GNBs were cleaved via a two-step process to control the width, length and angles, corresponding to the desired shape and size. All GNBs were subsequently exfoliated in superacid 20 and diluted in aqueous solution to produce a stable suspension of pristine GNs ( Fig. 1d,e; Supplementary Fig.…”

pH dependent isotropic to nematic phase transitions in graphene oxide dispersions reveal droplet liquid crystalline phases

“…Although significant progress has been made in the solid-state synthesis of graphene, liquid-phase graphene possess opportunities for large-scale synthesis and novel mesophases that may lead to ordered macroscopic structures such as thin films and fibers with enhanced electrical, mechanical and optical properties. 2,3 Graphene solvated in chlorosulfonic acid 2 and stabilized by surfactant 4 exhibit liquid crystalline behavior, as well as their composites with discotic molecules. 5 Chemically oxidized graphene sheets or graphene-oxide (GO) suspensions in water, the most accessible precursor to graphene-based materials, not surprisingly demonstrate I-N phase transitions, too.…”

Modeling and Simulation of Graphene Based Polymer Nanocomposites: Advances in the Last Decade

“…E.g., super-acids can dissolve graphene in large quantities [133]. In principle, the dispersion of graphene in polymer matrix can be controlled during the production route at two different stages.…”