Title:
Structured and viscous water in subnanometer gaps
Structured and viscous water in subnanometer gaps
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Author(s)
Li, Tai-De
Gao, Jianping
Szoszkiewicz, Robert
Landman, Uzi
Riedo, Elisa
Gao, Jianping
Szoszkiewicz, Robert
Landman, Uzi
Riedo, Elisa
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Abstract
Direct and simultaneous measurements of the normal and lateral forces encountered by a nanosize spherical silicon tip approaching a solid surface in purified water are reported. For tip-surface distances, 0±0.03 nm<d<2 nm, experiments and grand canonical molecular-dynamics simulations find oscillatory solvation forces for hydrophilic surfaces, mica and glass, and less pronounced oscillations for a hydrophobic surface, graphite. The simulations reveal layering of the confined water density and the development of hexagonal order in layers proximal to a quartz surface. For subnanometer hydrophilic confinement, the lateral force measurements show orders of magnitude increase of the viscosity with respect to bulk water, agreeing with a simulated sharp decrease in the diffusion constant. No viscosity increase is observed for hydrophobic surfaces.
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2007-03
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Article