Water diffusion in nanoporous glass: an NMR study at different hydration levels.
By pulsed field gradient nuclear magnetic resonance measurements, we investigated the translational diffusion of water confined in the 200 A diameter pores of a sol-gel silica glass. The experiments, performed as a function of the hydration level, showed an enhancement of the self-diffusion coefficient when the water content corresponds to one or fewer monolayers. An explanation for this occurrence has been given in terms of a two-phase process involving a fast molecular exchange between the liquid and the vapor phase. Moreover, in partially filled pores, the surface water diffusion coefficient was measured, and was 4 times lower than the diffusion of liquid confined water in saturated spaces.
Majolino
Domenico
D
Department of Physics, University of Messina, C.da Papardo, S.ta Sperone 31, P.O. Box 55, 98166 S. Agata, Messina, Italy. majolino@unime.it
Corsaro
Carmelo
C
Crupi
Vincenza
V
Venuti
Valentina
V
Wanderlingh
Ulderico
U
D004058:Diffusion; D005898:Glass / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D049329:Nanostructures / Q000737:chemistry*; D016062:Porosity; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties; D014867:Water / Q000737:chemistry*
D014867:Water; D012822:Silicon Dioxide