Geometric Effects on Nanopore Creation in Graphene and on the Impact-withstanding Efficiency of Graphene Nanosheets

Single- and multilayer graphene sheets (MLGSs) are projectile-resisting materials that can be bombarded by nanoparticles to produce graphene sheets of various sizes and distributions of nanopores. These sheets are used in a variety of applications, including DNA sequencing, water desalination, and phase separation. Here, the impact-withstanding efficiency of graphene nanosheets and the primary factors affecting creation of nanopores in these sheets were studied using a molecular dynamics method. The velocity of impacting nanoparticles and resulting displacement in graphene nanosheets are not sufficient criteria for evaluating the impact resistance of sheets with more than six layers. Instead, visual inspection of the bottom side of a graphene sheet should be used. Self-healing is the most important aspect of MLGSs because it closes the paths of penetrating nanoparticles in the upper layers of the sheets. For nanosheets with few layers, self-healing is observed only at very small nanoparticle velocities; however, when the number of layers is more than six, self-healing occurs even at high nanoparticle velocities. In nanoribbon simulations, it was found that layer boundaries improve resistance against projectile impacts that create well-defined oval shapes. By increasing the distance between layers, the carbon atoms of each layer experience more collisions with the carbon atoms of other layers. Thus, increasing the interlayer distance causes the number of unwanted collisions between carbon atoms to increase and the graphene nanosheets to disintegrate. Additionally, as the circularity of nanopores increases, they become more circular and homogeneous, in turn increasing interlayer spacing, the impact-withstanding efficiency of the sheets, and the circular shape of created nanopores.