  This work describes the behaviour of water molecules in
1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid under
nanoconfinement between graphene sheets. By means of molecular dynamics
simulations, an adsorption of water molecules at the graphene surface is
studied. A depletion of water molecules in the vicinity of the neutral and
negatively charged graphene surfaces and their adsorption at the positively
charged surface are observed in line with the preferential hydration of the
ionic liquid anions. The findings are appropriately described using a two-level
statistical model. The confinement effect on the structure and dynamics of the
mixtures is thoroughly analyzed using the density and the potential of mean
force profiles, as well as by the vibrational densities of states of water
molecules near the graphene surface. The orientation of water molecules and the
water-induced structural transitions in the layer closest to the graphene
surface are also discussed.

Soft Condensed Matter