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Since 2004 and the experimental rise of monolayer graphite as graphene, 1 there has been a need for a synthesis of large quantities of graphene, for large scale applications. 2 Several up-to-date reviews have appeared recently on graphene3–5 and chemical routes to graphene. 6–8 The ultimate goal of ‘‘chemical’’graphene or solution route graphene is to obtain large quantities of liquid formulations of graphene for composite formulation, surface patterning with graphene flakes, for sensors, transparent electrodes, self-standing films, etc. The most explored route has been the chemical reduction of graphite oxide. 8, 9 An alternative approach consists in dispersing graphite itself by sonication-induced dispersion in organic solvents, 10–15 or in water with surfactants, 16, 17 or π-stacking pyrenic molecules. 18 Oleum-19 and ClF3-intercalated20 graphite have also been dispersed using sonication. It was shown recently that the ternary GIC K (THF) C24 leads to solutions of graphene in N-methyl pyrrolidone (NMP). 21 We now report that more concentrated and chemically simpler solutions can be obtained by mild, spontaneous, dissolution of the parent GIC KC8 22 in NMP. The solutions only contain negatively charged graphene sheets and K+ ions. A rationale in terms of negative free energy of dissolution is provided. Stage 1 GICs, such as KC8, are made up of negatively charged graphene layers, separated by layers of ordered countercations. 23 KC8 was prepared according to literature procedures (cf. ESIw). Exposure to dry, freshly distilled NMP leads to spontaneous dissolution, ie true solubilization, rather than energy-aided metastable …
Publication date: 
1 Jan 2011

Luca Ortolani, Vittorio Morandi, Massimo Marcaccio, Francesco Paolucci

Biblio References: 
Volume: 47 Pages: 5470-5472
Chem. Commun