Atomic-scale mapping of hydrophobic layers on graphene and few-layer MoS 2 and WSe 2 in water

• Published in: Nature communications 2019-06, Vol.10 (1), p.2606
• Main Authors: Uhlig, Manuel R, Martin-Jimenez, Daniel, Garcia, Ricardo
• Format: Article
• Language: English
• ISSN: 2041-1723

The structure and the role of the interfacial water in mediating the interactions of extended hydrophobic surfaces are not well understood. Two-dimensional materials provide a variety of large and atomically flat hydrophobic surfaces to facilitate our understanding of hydrophobic interactions. The angstrom resolution capabilities of three-dimensional AFM are exploited to image the interfacial water organization on graphene, few-layer MoS and few-layer WSe . Those interfaces are characterized by the existence of a 2 nm thick region above the solid surface where the liquid density oscillates. The distances between adjacent layers for graphene, few-layer MoS and WSe are ~0.50 nm. This value is larger than the one predicted and measured for water density oscillations (~0.30 nm). The experiments indicate that on extended hydrophobic surfaces water molecules are expelled from the vicinity of the surface and replaced by several molecular-size hydrophobic layers.