Chodankar S, Perret E, Nygard K, Bunk O, Satapathy DK, Marzal RME, Balmer TE, Heuberger M, van der Veen JF (2012), Density profile of water in nanoslit, in EPL
, 99(2), 26001-p1-26001-p5.
Extreme confinement of water affects its viscosity, transport properties and wetting behaviour. We address the following questions. How does water change its structure and ordering behaviour under confinement? Can these structural rearrangements explain the property changes? The aim of the proposed research is to experimentally determine the structure of water in a model confinement system: a nanometre-sized slit consisting of two opposing, atomically smooth mica membranes at sub-nanometre distance. The average density profile of water along the confinement direction will be investigated with the use of specular X-ray reflectivity. If extended to non-specular diffraction, our method will enable a full (3D) determination of the position of the molecules relative to the outermost atoms of the single-crystal mica surfaces. The confining mica surfaces will be prepared in different chemical and charged states, e.g., hydrophilic or hydrophobic, and their effects on the water density profile will be investigated. Of interest are also salt solutions, where confinement may induce an ordering of the hydrated ions. The confinement-induced ordering phenomena may shed light on phenomena as diverse as swelling of clay, frost heave, weathering phenomena, and ion transport through channels.