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

Baum, Markus, Rébiscoul, Diane, Juranyi, Fanni, Rieutord, Francois
Journal of physical chemistry 2018 v.122 no.34 pp. 19857-19868
barium, calcium, infrared spectroscopy, ions, magnesium, neutron diffraction, physical chemistry, porous media, silica, sorption isotherms, thermogravimetry
The structural and dynamical properties of water confined in highly ordered mesoporous silica (SBA-15) in the presence of ions having various kosmotropic properties (XCl₂ with 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.