Effect of Hydrogen Bonds on the Dielectric Properties of Interfacial Water

Abstract

The dielectric constant for water is reduced under confinement. Although this phenomenon is well known, the underlying physical mechanism for the reduction is still in debate. In this work, we investigate the effect of the orientation of hydrogen bonds on the dielectric properties of confined water using molecular dynamics simulations. We find a reduced rotational diffusion coefficient for water molecules close to the solid surface. The reduced rotational diffusion arises due to the hindered rotation away from the plane parallel to the channel walls. The suppressed rotation in turn affects the orientational polarization of water, leading to a low value for the dielectric constant at the interface. We attribute the constrained out-of-plane rotation to originate from a higher density of planar hydrogen bonds formed by the interfacial water molecules.

Water as a tuneable solvent: a perspective

“…37 Water confined in reverse micelles, in cellulose nanocrystals, near surfaces or in the hydration sphere of the hydrophobic headgroups of tetramethylurea experiences a "stiffening" of its hydrogen bond network compared to bulk liquid water. [38][39][40][41][42][43][44][45] Reduction of the number and length of hydrogen bonds in confined water, initially detected by neutron scattering and confirmed by theoretical predictions, 42,[44][45][46][47] causes the dielectric constant of water to decrease, as shown by dielectric imaging. 35 These alterations are manifested even at relatively large length scales.…”

Revisiting the π → π* transition of the nitrite ion at the air/water interface: A combined experimental and theoretical study

“…In X-ray absorption spectra of bulk sodium nitrite solutions measured by the Saykally group, no appreciable ion pairing was observed [32]. We note, however, that the lower dielectric constant at the air/water interface [33,34] will increase the propensity for ion pair formation. Simulations by Venkateshwaran et al have shown that ion pairing near the interface can be enthalpically and entropically favorable for oppositely charged ions, as it releases some hydrating waters to the bulk and reduces pinning of capillary waves [35].…”

Origin and control of ionic hydration patterns in nanopores

“…The method can also be used to define the demarcation interface between the pore and the protein in continuous theories of ion transport such as the Poisson-Nernst-Planck (PNP) theory [68]. The method can thus provide fundamental insights into the electrostatics and dynamics of ions in sub-nanopores, where the dielectric properties on the nanoscale remain a challenging unsolved problem and a subject of intensive research [35,36,69,70].…”