Liquid-Phase Exfoliation of Graphite Towards Solubilized Graphenes

摘要

Following the astonishing discoveries of fullerenes and carbon nanotubes in earlier decades, the rise of graphene has recently triggered an exciting new area in the field of carbon nanoscience with continuously growing academic and technological impetus.[1,2] Currently, several methods have been proposed to prepare graphenes, such as micromechanical cleavage,[1,2] thermal annealing of SiC,[3] chemical reduction of graphite oxide,[4–6] intercalative expansion of graphite,[7,8] bottom-up growth,[9] chemical vapor deposition,[10] and liquid-phase exfoliation.[11] Especially this latter top-down approach is very appealing from a chemist’s point of view for the following reasons: i) it is direct, simple, and benign producing graphenes just by solvent treatment of graphite powders, and ii) the as-obtained sheets form colloidal dispersions in the solvents used for the exfoliation, thereby enabling their manipulation into various processes, like mixing, blending, casting, impregnation, spin-coating, or functionalization.[11–13] The key parameter for suitable solvents is that the solvent–graphene interactions must be at least comparable to those existing between the stacked graphenes in graphite. To that end, Coleman and coworkers have successfully demonstrated this concept using N-methylpyrrolidone, N,N-dimethylacetamide, g-butyrolactone, 1,3-dimethyl-2-imidazolidinone, and benzyl benzoate as solvents.[11a] Undoubtedly, the exploration of additional solvents in this context is highly recommended in order to strengthen the universal character of this genuine approach by providing more choices.