Electronic and Vibrational Properties of Episulfide-Graphene Materials

Our group has investigated the stability of sulfur adatoms on graphene obtained by a direct reaction of highly oriented pyrolytic graphite (HOPG) with elemental sulfur. With the help of density functional theory (DFT) calculations, we have developed different models of the structure and evaluated the electronic and vibrational properties of synthesized graphene-sulfur (GS) materials. Our structural models are based on sulfur atoms covalently attached to graphene. The DFT electronic structure calculations support the formation of a strong and stable sulfur bonding to graphene and give a chemical composition in good agreement with the experimental proportion of sulfur to carbon. In addition, ab-initio molecular dynamics simulations allow us to confirm the stability on S-G bonds. The vibrational modes calculated with DFT support the vibrational signatures of the GS materials observed using Raman spectroscopy.