Ultrasound-assisted direct exfoliation using supercritical carbon dioxide as a novel method of graphene flake production

In the present study, a new method involving ultrasound-assisted direct exfoliation with supercritical carbon dioxide is reported for graphene flake production. The influence of the starting material type – graphite (natural and expanded graphite) and duration of ultrasound treatment on the quality of the produced graphene-based material was assessed. By conducting scanning electron microscopy and Raman spectroscopy, it was found that the use of expanded graphite combined with 5 h of sonication in supercritical carbon dioxide yielded graphene nanoplatelets.