We investigated the vibrational dynamics and the structural relaxation of water nanoconfined in porous silica samples with pore size of 4 nm at different levels of hydration and temperature. We used as spectroscopic technique the time-resolved optical Kerr effect, which enables to investigate the ultrafast water dynamics in a wide time (0.1-10 picosecond) or frequency (10-0.1 THz) window. At low levels of hydration, corresponding to two complete superficial water layers, no freezing occurs and the water remains mobile at all the investigated temperatures, while at the fully hydration we witness to a partial ice formation at about 248 K that coexists with the part of surface water remaining in the supercooled state. At low hydration, both structural and vibrational dynamics show significant modifications compared to the bulk liquid water due to the strong interaction of the water molecules with silica surfaces. Inner water, instead, reveals relaxation dynamics very similar to the bulk one.
THz Dynamics of Nanoconfined Water by Ultrafast Optical Spectroscopy / Taschin, A; Bartolini, P; Torre, R. - STAMPA. - (2016), pp. 255-265. (Intervento presentato al convegno isema 2016- 11th International Conference on Electromagnetic Wave Interaction with Water and Moist Substances tenutosi a FIRENZE nel MAY 23-27 2016).
THz Dynamics of Nanoconfined Water by Ultrafast Optical Spectroscopy
TASCHIN, ANDREA;BARTOLINI, PAOLO;TORRE, RENATO
2016
Abstract
We investigated the vibrational dynamics and the structural relaxation of water nanoconfined in porous silica samples with pore size of 4 nm at different levels of hydration and temperature. We used as spectroscopic technique the time-resolved optical Kerr effect, which enables to investigate the ultrafast water dynamics in a wide time (0.1-10 picosecond) or frequency (10-0.1 THz) window. At low levels of hydration, corresponding to two complete superficial water layers, no freezing occurs and the water remains mobile at all the investigated temperatures, while at the fully hydration we witness to a partial ice formation at about 248 K that coexists with the part of surface water remaining in the supercooled state. At low hydration, both structural and vibrational dynamics show significant modifications compared to the bulk liquid water due to the strong interaction of the water molecules with silica surfaces. Inner water, instead, reveals relaxation dynamics very similar to the bulk one.File | Dimensione | Formato | |
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