Formation of Carbon Nanoscrolls During Wedge-Based Mechanical Exfoliation of HOPG

Carbon nanoscrolls (CNS) of various forms are observed when highly ordered pyrolytic graphite (HOPG) is mechanically exfoliated using a wedge. We present two hypothesis of how such scrolls form. The first hypothesis is based on microscopy evidence of pre-existing folds in layer edges of the HOPG. The second hypothesis is based on the literature evidence that graphene sheets when subject to deformation can result in defects on the torn edges. The sample preparation process can induce such defects in the HOPG layers. We show using molecular simulations that the interaction of the moving wedge with certain fold geometries can trigger scroll formation, confirming the first hypothesis. To test the second hypothesis, we show using molecular simulations, that layers with edge defects, upon interacting with the moving wedge, can also form scrolls. In reality, both these factors could simultaneously cause scrolls to form. Opportunities exist in fine-tuning this wedge-based mechanical exfoliation process to synthesize CNS for use in potential applications.