Dynamics of water in confined space (porous alumina): QENS study

Dynamics of water contained in the pores of alumina gel as studied using a combination of the high and medium resolution quasi-elastic neutron scattering (QENS) technique at room temperature and extending to the supercooled region is reported. In the single particle picture of the dynamics of water molecules in confined geometry (Volino-Dianoux model), two types of water are found to be present in the pores of alumina gel. Some water molecules are attached to the surfaces (localized) and others undergo diffusion within the otherwise available space in the pores. The localization radius and diffusion constant (D_loc) characterizing the local dynamics and also the diffusion constant (D_t) and residence time (τ₀) of the water molecules diffusing inside the alumina gel pores are obtained at different temperatures. Water molecules are found to undergo restricted diffusion in the pores at higher temperatures, which approach the bulk-like behaviour in the supercooled region.