Tuning Adsorption of Methylamine and Methanethiol on Twisted-Bilayer Graphene

The influence of a second graphene layer on the adsorption of methanethiol and methylamine is studied using density functional theory. Exploring different adsorption sites, we compare adsorption energies of both molecules on the monolayer, A-B stacked bilayer, and three different twisted-bilayer graphene systems. Results show that both molecules are physisorbed with energies larger than room temperature on determined sites, where methylamine is stronger adsorbed than methanethiol. In A-B stacking, adsorption energies are always smaller than those found in the monolayer. However, at some relative angles between the top and bottom graphene layers, the adsorption energy increases suggesting a molecular-adsorption tuning effect. Although the electronic charge at the interlayer and vacuum regions suffer a rearrangement, there is no charge transfer between molecules and graphene layers. It is expected that these results motivate further studies of molecule adsorption using as additional parameter the relative angle in twisted-bilayer graphene.