https://doi.org/10.1140/epje/i2004-10101-6
Original Article
The dynamics of water in nanoporous silica studied by dielectric spectroscopy
1
Laboratoire de Physique, Ecole Normale Supérieure de Lyon, 46 Allée d’Italie, 69364, Lyon, France
2
Department of Applied Mathematics and Physics, National Technical University of Athens, Iroon Politechniou 9, 15780, Zografou, Greece
3
Laboratoire de Chimie, Ecole Normale Supérieure de Lyon, 46 Allée d’Italie, 69364, Lyon, France
* e-mail: michel.peyrard@ens-lyon.fr
Received:
12
August
2004
Accepted:
7
February
2005
Published online:
8
March
2005
Broad-band dielectric spectroscopy is used to investigate the dynamics of hydration water on the surface of the cylindrical pores of a nanostructured silica material (MCM-41, with pore diameter of 3.2 nm) at various hydrations, in the temperature range 250-150 K. We focus our attention on orientational relaxations that shift from 0.5 MHz at 250 K to less than 1 Hz at 150 K. The measurements distinguish the relaxation of the hydroxyl groups at the surface of silica from the orientational dynamics of hydration water which strongly depends on the degree of hydration. Although it is significantly faster than the dynamics of water in ice, the orientational relaxation of “non-freezing” water has an activation energy comparable to that in ice when the hydration layer is complete and approximately two-molecule thick.
PACS: 77.22.-d Dielectric properties of solids and liquids – / 82.75.Mj Measurements and simulation of properties (optical, structural) of molecules in zeolites –
© EDP Sciences, Società Italiana di Fisica and Springer-Verlag, 2005
