Self-folding and self-scrolling mechanisms of edge-deformed graphene sheets: a molecular dynamics study

Graphene-based nanofolds (GNFs) are edge-connected 2D stacked monolayers that originate from single-layer graphene. Graphene-based nanoscrolls (GNSs) are nanomaterials with geometry resembling graphene layers rolled up into a spiral (papyrus-like) form. Both GNS and GNF structures induce significant changes in the mechanical and optoelectronic properties of single-layer graphene, aggregating new functionalities in carbon-based applications. Here, we carried out fully atomistic reactive (ReaxFF) molecular dynamics simulations to study the self-folding and self-scrolling mechanisms of edge-deformed graphene sheets. We adopted initial armchair edge-scrolled graphene (AESG(φ, θ)) structures with similar (or different) twist angles (φ, θ) in each edge, mimicking the initial configuration that was experimentally developed to form biscrolled sheets. The results showed that AESG(0, 2π) and AESG(2π, 2π) evolved to single-folded and two-folded fully stacked morphologies, respectively. As a general trend, for twist angles higher than 2π, the self-deformation process of AESG morphologies yields GNSs. Edge twist angles lower than π are not enough for triggering the self-deformation processes. In the AESG(0, 3π) and AESG(3π, 3π) cases, after a relaxation period, their morphology transition towards GNSs occurred rapidly. In the AESG(3π, 3π) dynamics, a metastable biscroll was formed by the interplay between the left- and right-sided partial scrolling while forming a unique GNS. At high-temperature perturbations, the edge folding and scrolling transitions to GNFs and GNSs occurred within an ultrafast time-period. Remarkably, the AESG(2π, 3π) evolved to a dual state that combines folded and scrolled structures in a temperature-independent process.