Intrinsic Wettability in Pristine Graphene.

The wettability of graphene remains controversial owing to its high sensitivity to the surroundings, which is reflected by the wide range of reported water contact angle (WCA). Specifically, the surface contamination and underlying substrate would strongly alter the intrinsic wettability of graphene. Here, we investigate the intrinsic wettability of graphene by measuring WCA on suspended, superclean graphene membrane using environmental scanning electron microscope. An extremely low WCA with an average value ∼ 30o was observed, confirming the hydrophilic nature of pristine graphene. This high hydrophilicity originates from the charge transfer between graphene and water molecules through H-π interaction. Our work provides a deep understanding of the water-graphene interaction and opens up a new way for measuring the surface properties of 2D materials. This article is protected by copyright. All rights reserved.