Effects of the Wettability of a Probing Tip on the Hydration Layer Imaged in Atomic Force Microscopy

ZQ Zhang and LY Bai and S Chung and J Jang, JOURNAL OF PHYSICAL CHEMISTRY C, 125, 11197-11205 (2021).

DOI: 10.1021/acs.jpcc.1c02022

Utilizing a fully atomistic molecular dynamics simulation, we uncovered the molecular structure of a hydration layer formed on a hydrophobic carbon sample. By varying the wettability of a probe tip, we investigated how the hydration layer manifests as an image (force) measured in atomic force microscopy. With approaching a tip within 1 nm, the intrinsic hydration layer was significantly perturbed. A hydrophobic tip eventually evaporated the hydration layer at a closer distance, giving an attractive force characteristic of a hydrophobic force. With a hydrophilic tip, the hydration layer persisted with some compression, giving an oscillating force with a period close to the molecular diameter of water.

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