Interaction of sodium bisulfate with mono- and bi-layer graphene

The interaction of sodium bisulfate molecules with one and two graphene layers is studied using density functional theory calculations. Equilibrium configurations, electron transfers, binding energies, and densities of states are presented for two different concentrations and for both (cis and trans) molecule isomers. The adsorption of sodium bisulfate on monolayer graphene does not alter its unusual electrical conducting properties (it is a zero-band-gap semiconductor) when the concentration is low but when the concentration increases the system becomes a very weak conductor. The intercalation of sodium bisulfate inside bilayer graphene decouples the electronic behavior of the two graphene sheets and when the concentration of sodium bisulfate is high the system becomes a zero-band-gap semiconductor like monolayer graphene. Besides the intercalation of the molecules separates the two layers, reducing the interaction between them and making easier their separation. This fact explains the surfactant effect of molecules containing a sulfuric head with a sodium atom on carbon nanostructures, which helps to exfoliate graphene layers from graphite and to separate the nanotubes in a bundle.