Structural and Dynamical Properties of Water Confined in Highly Ordered Mesoporous Silica in the Presence of Electrolytes

The structural and dynamical properties of water confined in highly ordered mesoporous silica (SBA-15) in the presence of ions having various kosmotropic properties (XCl2with X = Ba2+, Ca2+, and Mg2+) were characterized using thermogravimetric analysis, infrared spectroscopy, and quasi-elastic neutron scattering and were related to the surface density of ions obtained by sorption isotherms. The results highlight that the water network is perturbed by the confinement and that the dynamics of water molecules at a picosecond time scale is slowed by the presence of ions. These results are mainly explained by the presence of the interfacial layer where both the structure of the water network and the water dynamics are influenced by the surface ion excess and the kosmotropic properties of ions.