Abstract
The 1H nuclear magnetic resonance (NMR) spectra and the dipolar spin–lattice relaxation time T1D for 1H in the natural natrolite (Na2Al2Si3O10·2H2O) have been measured in the temperature range of 190–390 K. From the temperature transformations of 1H NMR spectra, it follows that at T > 300 K, the diffusion of water molecules along the nano-channels is observed. From experimental T1D data, it follows that the 180° flip motion of the water molecules takes place in natrolite. At low temperature (T < 250 K), the dipolar interaction with paramagnetic impurities as a relaxation mechanism of 1H nuclei becomes significant.
Highlights
Physical properties of materials entrapped in nano-sized cavities of significant interest for both fundamental science and application of nano-porous compounds
We have investigated the mobility of the water molecules in nanochannels of natrolite by the 1H nuclear magnetic resonance (NMR) pulse method, measuring the temperature dependences of 1H spectra and the spin–lattice dipolar relaxation time T1D
The 1H NMR spectra and spin– lattice relaxation times were measured at m0 = 400.13 MHz frequency in 9.4 T magnetic field using a Bruker Avance-400 NMR spectrometer
Summary
Physical properties of materials entrapped in nano-sized cavities of significant interest for both fundamental science and application of nano-porous compounds. The mineral natrolite is a typical porous compound (zeolite) with the narrow nanochannels [1]. The natrolite structure careful refinements carried out by X-ray and neutron diffraction [2,3,4,5]. The natrolite unit cell is orthorhombic with space group Fdd and contains eight formula units Na2Al2Si3O10Á2H2O. The natrolite framework consists of tetrahedra of alumina (AlO4) and silica (SiO4) chains linked together via common oxygen atoms. The natrolite structure contains channels running parallel to the c-axis (Fig. 1a) and channels connected among themselves by oxygen windows (Fig. 1b). These oxygen rings create a system of channels,
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