Phase, Structure, and Dynamics of the Hydration Layer Probed by Atomic Force Microscopy
L Bai and Z Zhang and J Jang, JOURNAL OF PHYSICAL CHEMISTRY C, 123, 21528-21537 (2019).
Using the molecular dynamics method we simulate the hydration layer probed by an atomic force microscope (AFM) tip. We investigate how the AFM tip affects the phase, structure, and dynamics of the intrinsic hydration layer formed on a hydrophobic carbon plate. Without the AFM tip the molecular packing and orientation of the hydration layer are ordered up to the second molecular layer. With approaching the tip, the hydration layer is perturbed and eventually evaporates. The force- distance curve in AFM lacks an oscillation typically found for the hydration layer formed on a hydrophilic surface. The molecular diffusions parallel and perpendicular to the plate are, respectively, enhanced and restricted by the tip. The molecular reorientation is significantly slowed down by the tip and plate, which disrupt the hydrogen-bond network present in the bulk water.
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