Influence of Hydrophilic Surface Specificity on the Structural Properties of Confined Water

Abstract

The influence of chemical specificity of hydrophilic surfaces on the structure of confined water in the subnanometer regime is investigated using grand canonical Monte Carlo simulations. The structural variations for water confined between hydroxylated silica surfaces are contrasted with water confined between mica surfaces. Although both surfaces are hydrophilic, our study shows that hydration of potassium ions on the mica surface has a strong influence on the water structure and solvation force response of confined water. In contrast to the disrupted hydrogen bond network observed for water confined between mica surfaces, water between silica surfaces retains its hydrogen bond network displaying bulklike structural features down to surface separations as small as 0.45 nm. Hydrogen bonding of an invariant contact water layer with the surface silanol groups aids in maintaining a constant number of hydrogen bonds per water molecule for the silica surfaces. As a consequence, water depletion and rearrangement upon decreasing confinement is a strong function of the hydrophilic surface specificity, particularly at smaller separations. An oscillatory solvation force response is only observed for water confined between silica surfaces, and bulklike features are observed for both surfaces above a surface separation of about 1.2 nm. We evaluate and contrast the water density, dipole moment distributions, pair correlation functions, and solvation forces as a function of the surface separation.

Energy dissipation of nanoconfined hydration layer: Long-range hydration on the hydrophilic solid surface

“…Experiments under various relative humidity (RH) show that HWL consists of about 6 layers of water molecules on the hydrophilic solid surface. This is thicker than the results of both computer simulation2728 and experiments performed by the AFM-based sharp tip252629, where the results indicate the hydration layer effect on the solid surface disappears at about 3 layers.…”

Monte Carlo Study on the Water Meniscus Condensation and Capillary Force in Atomic Force Microscopy

“…This range of force is longer than that of the force between silica or mica plates immersed in liquid water (= 12 Å). 49 Interestingly, F z shows a damped oscillation with respect to d: F z is slightly repulsive at the shortest d and reaches a minimum at d = 6 Å at RHs of both 10% and 40% (see below for discussion on why the force is minimal at this d value). This d value at the minimal F z agrees with those found in the GCMC and the density functional theory studies adopting the lattice gas model.…”

Dynamics of confined water reconstructed from inelastic x-ray scattering measurements of bulk response functions

“…However, similar measurements have shown that the shear viscosity increases by orders of magnitude [12][13][14][15], and simulations have indicated an increase in the translational and rotational correlation lifetimes [16,26]. Computational models of water demonstrate a rich phase behavior consistent with solidification [17][18][19] and dynamical phenomena like shear thinning [10,20] and shear melting and freezing [16].…”