title: No confinement needed: observation of a metastable hydrophobic wetting two-layer ice on graphene.
abstract: The structure of water at interfaces is crucial for processes ranging from photocatalysis to protein folding. Here, we investigate the structure and lattice dynamics of two-layer crystalline ice films grown on a hydrophobic substrate, graphene on Pt(111), with low energy electron diffraction, reflection-absorption infrared spectroscopy, rare-gas adsorption/desorption, and ab initio molecular dynamics. Unlike hexagonal ice, which consists of stacks of puckered hexagonal "bilayers", this new ice polymorph consists of two flat hexagonal sheets of water molecules in which the hexagons in each sheet are stacked directly on top of each other. Such two-layer ices have been predicted for water confined between hydrophobic walls, but not previously observed experimentally. Our results show that the two-layer ice forms even at zero pressure at a single hydrophobic interface by maximizing the number of hydrogen bonds at the expense of adopting a nontetrahedral geometry with weakened hydrogen bonds.
authors: Chemical and Materials Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, USA. gregory.kimmel@pnl.gov
authors: Greg A
authors: GA
authors: Kimmel
authors: Jesper
authors: J
authors: Matthiesen
authors: Marcel
authors: M
authors: Baer
authors: Christopher J
authors: CJ
authors: Mundy
authors: Nikolay G
authors: NG
authors: Petrik
authors: R Scott
authors: RS
authors: Smith
authors: Zdenek
authors: Z
authors: Dohnálek
authors: Bruce D
authors: BD
authors: Kay
mesh_terms: D000327:Adsorption; D002244:Carbon / Q000737:chemistry*; D004583:Electrons; D057927:Hydrophobic and Hydrophilic Interactions; D007053:Ice; D007700:Kinetics; D013499:Surface Properties; D013696:Temperature
chemical_list: D007053:Ice; D002244:Carbon