Dynamical properties of liquids in restricted geometries

Raman scattering and Fourier-transform infrared (FT-IR) absorption results on confined water are presented. The aim is to characterize different porous materials, studying the vibrational properties of water inserted in their porous structure, and determining the relationship between these two aspects. Confinement has been realized by using a sol-gel silica glass, GelSil, with 26 Å diameter pores of huge hydrophilic inner surface, and NaA type zeolites, with 10 Å diameter pores in which 27 H2O molecules can be located. The O-H stretching spectral range (2800-3800 cm−1), as a function of temperature and for different water contents, has been explored. From a comparison of the data in these two cases, we put into evidence the structure breaker role of GelSil, as revealed by the slowing down of the collective contribution to the polarized O-H stretching band, indicating that the tetrabonded H2O network is destroyed. On the other side, NaA zeolites will be proofed to play a structure breaker effect on physisorbed water, since the contribution to the O-H stretching band linked to the tetrahedral ice-like arrangement is present even at the lowest hydration conditions.