Inducing energy gaps in graphene monolayer and bilayer
  In this paper we propose a mechanism for the induction of energy gaps in the spectrum of graphene and its bilayer, when both these materials are covered with water and ammonia molecules. The energy gaps obtained are within the range 20-30 meV, values compatible to those found in experimental studies of graphene bilayer. We further show that the binding energies are large enough for the adsorption of the molecules to be maintained even at room temperature. 
R. M. Ribeiro, N. M. R. Peres, J. Coutinho, and P. R. Briddon