Title: Hydrophobic Ice Confined between Graphene and MoS2,
Abstract: The structure and nature of water confined between hydrophobic molybdenum
disulfide (MoS2) and graphene (Gr) are investigated at room temperature by
means of atomic force microscopy. We find the formation of two-dimensional (2D)
crystalline ice layers. In contrast to the hexagonal ice 'bilayers' of bulk
ice, these 2D crystalline ice phases consist of two planar hexagonal layers.
Additional water condensation leads to either lateral expansion of the ice
layers or to the formation of three-dimensional water droplets on top or at the
edges of the two-layer ice, indicating that water does not wet these planar ice
films. The results presented here are in line with a recent theory suggesting
that water confined between hydrophobic walls forms 2D crystalline two-layer
ice with a nontetrahedral geometry and intrahydrogen bonding. The lack of
dangling bonds on either surface of the ice film gives rise to a hydrophobic
character. The unusual geometry of these ice films is of great potential
importance in biological systems with water in direct contact with hydrophobic
surfaces.