Unexpected change in the electronic properties of the Au-graphene interface caused by toluene

Density-functional theory is used to show that isolated Au atoms on graphene do not lead to substantial charge transfer or doping but this is altered if a second layer of graphene or toluene is present. Thus intercalating Au into a sandwich of graphene-toluene leads to n-type doping of graphene. The effect is attributed to a confinement of the $6s$ level of Au by toluene or the second graphene layer. It is also shown that K atoms dope graphene with the transfer of around one electron. The binding energies and electronic structure of Au, Cr, and Ti on graphene are also reported.