Freezing of Water Confined at the Nanoscale

Abstract

Freezing of water in hydrophilic nanopores (D=1.2 nm) is probed at the microscopic scale using x-ray diffraction, Raman spectroscopy, and molecular simulation. A freezing scenario, which has not been observed previously, is reported; while the pore surface induces orientational order of water in contact with it, water does not crystallize at temperatures as low as 173 K. Crystallization at the surface is suppressed as the number of hydrogen bonds formed is insufficient (even when including hydrogen bonds with the surface), while crystallization in the pore center is hindered as the curvature prevents the formation of a network of tetrahedrally coordinated molecules. This sheds light on the concept of an ubiquitous unfreezable water layer by showing that the latter has a rigid (i.e., glassy) liquidlike structure, but can exhibit orientational order.

Translational diffusion of water inside hydrophobic carbon micropores studied by neutron spectroscopy and molecular dynamics simulation

“…Crystallization, if present, would be observed as an abrupt change in I(T ), which is not seen here at any Q. This suggests that the adsorbed water does not solidify and remains mobile down to at least 150 K, consistent with previous studies [29]. It is worth noting however that the temperature range ( K) at which the water dynamics were subsequently simulated and measured, was always above the melting point of water [30,31].…”

Reduction of Acetonitrile by Hydrated Magnesium Cations Mg+(H2O)n (n≈20–60) in the Gas Phase

“…[4] In other systems, water activation results in elimination of atomic or molecular hydrogen and oxidation of the metal to the metal hydroxide. [6][7][8][9][10][11][12][13][14] Ion-molecule reactions provide insight into the subtle chemistry of these species.…”

“…[1] Exchange experiments with D 2 O [2] indicate that hydrated alkali-metal ions [3] as well as most transition-metal ions M + (H 2 O) n , M= Cr, Fe, Co, Ni, Cu, and Zn, [4] consist of a singly charged metal center embedded in a hydrogenbonded network of intact H 2 O molecules, whereas room-temperature black-body infrared radiative dissociation (BIRD) [5] activates an insertion reaction in Mn + (H 2 O) n , which for n % 8-20 are converted into HMnOH + (H 2 O) nÀ1 . [4] In other systems, water activation results in elimination of atomic or molecular hydrogen and oxidation of the metal to the metal hydroxide.…”

Skin Supersolidity of Water and Ice

“…The air gap between the water and the hydrophobic substrate [16] makes the contacting skin more like free. However, water confined in hydrophilic nanopores [50,51] or wetting with hydrophilic topologic configurations [52] exhibits supercooling effect, or melts at lower temperature than usual because of the lacking of broken bonds.…”