Eco-friendly exfoliation of graphite into pristine graphene with little defect by a facile physical treatment

The superior properties of graphene in applications ranging from electronic devices to composites have been extensively reported. So far, no mass production of defect-free few-layer graphene has been attained. The authors of this study have demonstrated a high-yield method to produce defect-free few-layer graphene by exfoliation of graphite in a degradable water-soluble polymer (I) with cholamine modification, and the obtained intercalated (D-I) chemical structure was confirmed by Fourier transform infrared spectroscopy. The electron donor forms π–π stacking interactions with the graphene sheets during sonication, which prevents the exfoliated graphene from restacking. The method is environment-friendly compared with other liquid exfoliation methods, and the aqueous and ethanolic solutions of graphene are stable for long durations. The authors also confirmed the presence of gossamer graphene sheets, which have typical wrinkled and folded structures, by using high resolution transmission electron microscopy. Atomic force microscopy images revealed that graphene sheets with a thickness of approximately 1 nm were uniformly distributed.