Regensburg 2019 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 20: Wetting, Fluidics and Liquids at Interfaces and Surfaces (joint session CPP/DY)

CPP 20.1: Vortrag

Dienstag, 2. April 2019, 09:30–09:45, H13

Non-monotonous wetting of graphene-mica and MoS2-mica interfaces with a molecular layer of water — •Abdul Rauf, Andre Schilo, Nikolai Severin, Igor M. Sokolov, and Jürgen P. Rabe — Department of Physics & IRIS Adlershof, Humboldt-Universität zu Berlin, Germany

Hydration of interfaces with a layer of water is a ubiquitous phenomenon. Nevertheless, the understanding of the wetting process is still limited, since it is experimentally difficult to follow. Here, graphene and monolayers of MoS2 deposited on dry mica are used to investigate wetting of the 2D material-mica interfaces with a molecularly thin layer of water employing scanning force microscopy in different modes. Wetting starts at relative humidities (RH) of 10-17% for graphenes and 8-9% for MoS2, and it concludes with a homogeneous layer at 25-30% and 15-20%, respectively. Wetting occurs non-monotonously in time and space for both types of interfaces. Initially a highly compliant and unstable layer of water spreads, which subsequently stabilizes by developing labyrinthine nanostructures. These nanostructures exhibit distinct mechanical deformability and dissipation, which is ascribed to different densities of the confined water layer. The laterally structured morphology is explained by the interplay of counteracting long-range dipole-dipole repulsion and short-range line tension, associated with the mechanical deformation of the 2D material. The proposed origins of the interactions are common for thin layers of polar molecules at interfaces, implying that the lateral structuring of thin wetting layers may also be a quite general phenomenon.

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