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| Titel: |
Vibrational and diffusional dynamics of water in Mg50-A zeolites by spectroscopic investigation |
| Auteur: |
Crupi, V. Majolino, D. Migliardo, P. Venuti, V. Mizota, T. |
| Verschenen in: |
Molecular physics |
| Paginering: | Jaargang 102 (2004) nr. 18 pagina's 1943-1957 |
| Jaar: |
2004-09-20 |
| Inhoud: |
The spectral substructure of the O-H stretching mode of water confined in Mg50-A zeolites is demonstrated, in full hydration conditions and in the temperature range 20-80°C, using Fourier transform Infrared (FT-IR) spectroscopy. Band shapes have been fitted to individual components, according to the actual theories for associated liquids, and three major constituent peaks were derived, at 3230 cm-1 (ω1), 3460 cm-1 (ω2), and 3600 cm-1 (ω3). They have been related, respectively, to an ice-like molecular environment and other hydrogen-bonding configurations. A detailed quantitative analysis of their centre frequencies and relative intensities, traced over the full temperature range investigated, has led to the conclusion that these subbands show direct evidence, under confinement, of bifurcated hydrogen bonds (BHB) among three water molecules as a main feature of the structure of liquid water. The most interesting result comes from the observation, at all temperatures, of the tetrahedral connectivity typical of bulk water. In this sense, we attributed to the zeolitic surface a 'structure-maker' role on physisorbed water. This role becomes particularly relevant at the lowest temperature, where the ice-like contribution appears to be the favoured one even under confinement. Furthermore, preliminary results are presented of an incoherent quasi-elastic neutron scattering (IQENS) investigation of the diffusional dynamics of water in the same system, at T=20°C, analysed in the framework of the Confined Diffusion Model (CDM). |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
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