Effect of a Finite Single-Layer Graphene Sheet on Water

Atomically flat surfaces, subject to periodic boundary conditions, have been shown to induce layering of water through molecular dynamics simulations. Experiments have confirmed layering on mesoscopic surfaces. In this work, the influence of a 41.688 Å × 41.138 Å finite single-layer graphene sheet (SLGS) on the surrounding water is examined at room temperature. We observe distinct layering of water in the immediate vicinity of the finite SLGS, exhibiting weak structural as well as orientational ordering within the layers. Changes in hydrogen bonding with respect to the bulk are found, particularly in the first layer over the SLGS. When short-range C-H interactions are switched off, broadening of the water layers can be clearly discerned, asymmetric donor and acceptor profiles are observed, a sharp reduction in donor count is seen in the first layer over SLGS, and dangling bonds seem to orient toward the interface. Interestingly, layering tendencies are noticed even near rigid SLGS of sizes as small as 12 Å × 11.5 Å. However, thermal fluctuations at room temperature are found to produce significant deformations in the SLGS, making it difficult for water to form stable layered density profiles.