Hydrothermal exfoliation of graphite to produce few-layer graphene

This poster describes an easy exfoliation of graphite in surfactant-water solution. Here, we report that pristine graphite heat-treated (pre-treatment) in an autoclave for 15 hours at 180 ºC with a surfactantwater solution improves the process of sonication. The cationic surfactant hexadecyltrimethylammonium Bromide (CTAB) used in this work can be exploited both as dispersant and stabilizer, for pretreatment and direct exfoliation of graphite, without the continuous addition of surfactant, without a polymer stabilizer and without extensive sonication periods. Scanning Electron Microscope shows: (i) the distance between the layers increases in the pre-treatment of graphite without significant damage to the crystal structure, and (ii) thin and semitransparent films about 3 to 10 µm after the sonication process were observed. The absorption spectrum of graphene in the surfactant-water solution shows a peak around 268 nm characteristic of the ? --> ?* interactions, it remarks that graphene absorption spectrum is flat and featureless. Raman spectroscopy allows to observe a D peak, can be attributed to the surfactant/graphene interaction, and not to a disorder in the structure, also a 2D peak is observed comparable to previous reports <5 layers. The graphene suspended was stable for several months without a substantial sedimentation and it can be vacuum filtered to make thin conductive films and put onto surfaces as individual flakes, maintaining its electronic properties, which can be used in a wide range of applications. This work opens the possibility of improving the heat-treated of graphite with other surfactants.