title: Water confinement in faujasite cages: a deuteron NMR investigation in a wide temperature range. 2. Spectra and relaxation at high temperature.
abstract: Deuteron NMR spectra and spin-lattice relaxation were measured for D2O confined in NaX, NaY, and DY faujasites with various loadings at temperatures ranging from 200 to 310 K with the aim to study molecular mobility of confined water. Hysteresis of spin-lattice relaxation was observed for both DY and NaY(2.4) samples at 500% loading (280 water molecules per unit cell) in a heating-cooling cycle between 264.5 and 277.7 K. The hysteresis is most likely reflecting formation and decomposition of water clusters at different temperature. Spin-lattice relaxation rates obtained from the experiment are consistent with a picture of the fast magnetization exchange between two dynamically different deuteron populations. The observed relaxation behavior as a function of temperature and loading is most likely an effect of interplay between translational and rotational diffusion. Translational diffusion of water molecules is found to be related to the strength of the electrostatic interaction of water oxygen atoms to faujasite sodium cations, whereas water molecule reorientations seem to depend on the strength of hydrogen bonding to faujasite oxygen atoms and the strength of hydrogen bonds between water molecules, at outer and inner positions in water clusters, respectively.
authors: University of Agriculture , 31-120 Kraków, Poland.
authors: A M
authors: AM
authors: Szymocha
authors: Z T
authors: ZT
authors: Lalowicz
authors: A
authors: A
authors: Birczyński
authors: M
authors: M
authors: Krzystyniak
authors: G
authors: G
authors: Stoch
authors: K
authors: K
authors: Góra-Marek
mesh_terms: D003903:Deuterium / Q000737:chemistry*; D004058:Diffusion; D009682:Magnetic Resonance Spectroscopy; D056004:Molecular Dynamics Simulation; D011789:Quantum Theory; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D003903:Deuterium