  We analyse the interaction between charges and graphene layers. The electric
polarisability of graphene induces a force, that can be described by an image
charge. The analysis shows that graphene can be described as an imperfect
conductor with a finite dielectric constant, $\epsilon_r$, for weak coupling,
and it behaves as a metal for strong fields. As a consequence, the interaction
between polar molecules and graphene layer(s) tends to align the molecular
dipole along the direction normal to the graphene, and quantitative estimates
of the energy gain are given The strength of this interaction can be sufficient
to overcome thermal effects when the molecule is close to the layer, even at
room temperature. Hence, boundary effects play a significant role in
determining the structure of systems such as water confined in atomically
narrow van der Waals heterostructures.
