Structure and thermodynamics of 2-dimensional water: a neutron pair distribution function study

Confined water is ubiquitous and of central importance for a series of phenomena in condensed matter, materials science, biology, chemistry, and nanotechnology. Recent investigations show the properties of water confined at ångström and nanoscale strongly deviating from the bulk. However, it remains unclear which structural factors drive such anomalous behaviour while the phases are formed. Several theoretical studies on the water phases confined in 1- and 2D nanospace are found, nonetheless, experimental data to probe and validate the simulation results are still lacking. Our previous investigations, using our pioneering method of fabricating ångström channels down to a single molecular layer, also show intriguing deviations from the bulk such as ballistic flow and near-zero dielectric constant. Although still obscure, these and other evidence from the recent literature converge to the hypothesis that the physics governing the hydrogen bonding network may hold the key to unveil these phenomena at the quantum level. Herein, we propose that by stripping off one dimension, a much clearer understanding of this system can be achieved using neutron diffraction. The enhanced scattering signal of hydrogen and deuterium will, for the first time, build a much more resolved picture of the structure of 2-dimensional water and its transitions. Moreover, detectable diffuse scattering events will provide an exclusive and rich correlation with inelastic scattering data from other proposals.