Influence of defects and charges on the colloidal stabilization of graphene in water.

Mastering graphene preparation is an essential step to its integration into practical applications.For large-scale purposes, full graphite exfoliation appears as a suitable route for grapheneproduction. However, it requires overpowering attractive van der Waals forces demanding largeenergy input, with the risk of introducing defects in the material. This difficulty can beovercome by using graphite intercalation compounds (GIC) as starting material. The greaterinter-sheet separation in GICs (compared with graphite) allows the gentler exfoliation ofsoluble graphenide (reduced graphene) flakes. A solvent exchange strategy, accompanied bythe oxidation of graphenide to graphene, can be implemented to produce stable aqueousgraphene dispersions (Eau de graphene, EdG), which can be readily incorporated into manyprocesses or materials. In this work, we prove that electrostatic forces are responsible for thestability of fully exfoliated graphene in water, and explore the influence of the oxidation andsolvent exchange procedures on the quality and stability of the EdG. We show that the amountof defects in graphene is limited if graphenide oxidation is carried out before exposing thematerial to water, and that gas removal of water before the incorporation of pre-oxidizedgraphene is advantageous for the long-term stability of the EdG.

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