# Hydrophobic Ice Confined between Graphene and MoS2

## TL;DR

This study investigates the structure of water confined between hydrophobic graphene and MoS2, revealing the formation of unique 2D crystalline ice layers with potential biological relevance.

## Contribution

It provides experimental evidence of 2D crystalline ice between hydrophobic surfaces, supporting recent theories on non-tetrahedral water structures.

## Key findings

- Formation of two-layer 2D crystalline ice
- Water does not wet these planar ice films
- Additional water leads to lateral expansion or droplets

## 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.