Tunable Wettability and Conductivity of the Graphene Oxide Surface with Insights from Density Functional Theory and Molecular Dynamics Investigations

The current study focuses on the investigation of changes in chemical, wetting, and electrical transport properties of a graphene oxide film irradiated by low-energy (5 keV) nitrogen ions at different fluences. At this energy, there is no apparent change in surface topography. However, a strong change in surface chemistry is noticeable through a Raman scattering study, an X-ray diffraction study, and X-ray photoelectron spectroscopy. Such a change has significant effects on its surface wetting property and electrical conductivity. The initial hydrophilic surface becomes hydrophobic after irradiation. Furthermore, the electrical conductivity increases with the ion fluence. Calculations based on density functional theory and molecular dynamics simulations predict that these observed changes are primarily due to the partial removal of oxygen-containing groups, leading to the increased availability of C p(z) electrons and their consequent in-plane delocalization leading to pi conjugation, which is known to be central to structural stability, resulting in the ease of electron transport in networks of three coordinated carbon atoms. The current study further enlightens a path of synthesizing reduced graphene oxide and graphene from graphene oxide using a low-energy ion beam irradiation technique.