In this study, we characterized the structure and the dynamics at a picosecond scale of water molecules in aqueous solutions with cations having various kosmotropic properties (XCl2 where X = Ba2+, Ca2+, and Mg2+) confined in highly ordered mesoporous silica (MCM-41 and grafted MCM-41) by Fourier transform infrared spectroscopy and quasi-elastic neutron scattering. We pinpointed the critical pore size and the electrolyte concentration at which the influence of the ion nature becomes the main factor affecting the water properties. These results suggest that whatever the ions kosmotropic properties, for pore sizes ϕp < 2.6 nm and [XCl2] ≤ 1 M, the water dynamics is mainly slowed down by the size of the confinement. For pore sizes of 6.6 nm, the water dynamics depends on the concentration and kosmotropic properties of the ion more than on the confinement. The water properties within the interfacial layer were also assessed and related to the surface ion excesses obtained by sorption isotherms. We showed that, for pore sizes ϕp ≥ 2.6 nm, the surface ion excess at the pore surface is the main driver affecting the structural properties of water molecules and their dynamics within the interfacial layer.

We present an original approach for preparing silica-based nanocomposites containing Prussian blue-type nanoparticles via click chemistry. Click reaction is used to prepare a triazole-copper complex in a single step; this complex is subsequently used to anchor copper hexacyanoferrate nanoparticles within a porous silica matrix (porous glass pearls or SBA-15). This CuAAC "click reaction" was performed using a relatively large copper concentration for two reasons: First, the Cu catalyzes the triazole ring formation, then the ring acts as a chelator, immobilizing the copper inside the silica matrix. Successively adding hexacyanoferrate precursors that coordinate with the copper ions at the triazole sites led to efficient and selective nanocomposite formation; this material was developed to mitigate Cs + ion contamination. The efficiency of these asprepared nanocomposites and their selectivity for Cs + from different effluents, such as pure water, seawater, and radioactive seawater (simulating the Fukushima site), were evaluated using sorption experiments. These immobilized nanocomposites present a high Cs + selectivity while demonstrating a K d value above that of the bulk material.