In this talk, I will highlight the recent investigation on the frictional behavior of 2-dimensional (2D) intercalated water between the hydrophilic surfaces and more hydrophobic two-dimensional atomic layers (e.g., graphene and MoS2). We found that the water intercalated between 2D materials (e.g., graphene and MoS2) and the hydrophilic substrate increases the friction force between the AFM tip and 2D flakes deposited. Moreover, the friction on both graphene and MoS2 increased as the number of stacking water layers increased. The magnitude of friction increase was, on the other hand, reduced as following an increase of the number of covering 2D layer above intercalated water layer, and then the friction is eventually not distinguished from the multi-layer stack excluded water adsorption. Additionally, we indicate that the intercalation of deuterium oxide (D2O) leads a decrease of friction at H2O intercalated graphene on mica due to the lower vibrational frequency of D2O adsorbate, which means the low rate of frictional energy dissipation at the interface. This study provides that the intrinsic vibration modes of the water molecules play a key role in the coupling of the 2D materials modes to the phonon bath of the substrate. Finally, I will address the relationship between nanoscale friction on ultrananocrystalline diamond surface and the surrounding environment of water by using ambient pressure−atomic force microscopy. This result elucidates the role of vapor-phase water in the tribological properties of carbon-based materials.

Atomic-scale friction properties of two-dimensional intercalated water layers

ACS Spring 2022

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