On the Use of Pulsed Field Gradients in a High-Field NMR Spectrometer to Study Restricted Diffusion in Zeolites

Kärger, Jörg; Bär, Nils-Karsten; Heink, W.; Pfeifer, H.; Seiffert, G.

doi:10.1515/zna-1995-2-310

Cited by 64 publications

(45 citation statements)

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“…The pulsed field gradient NMR self-diffusion measurements with the pulse program mentioned above were performed on a home-built spectrometer with a superconducting magnet at a proton NMR frequency of W, = 400 MHz (13). In the experiment, the field gradient g was varied (maximum value 25 T/m) at fixed pulse width 6 (between 0.3 ms and 2 ms) and diffusion time A.…”

Section: Nmr Experimentsmentioning

confidence: 99%

Pulsed field gradient NMR and nuclear magnetic relaxation studies of water mobility in hydrated collagen II

Knauss

Fleischer

Gründer

et al. 1996

Magnetic Resonance in Med

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Transverse nuclear magnetic relaxation and self-diffusion of water were measured in hydrated collagen II. Self-diffusion measurements were conducted by pulsed field gradient NMR (PFG NMR) and weighting of the different species in the signal by variable T2 relaxation in the experiment. Two fractions of water protons were detected, one with a short T2 value but high diffusivity and one with a long T2 value and low, completely restricted diffusion. The distance of the diffusion barriers was determined to be 2.3 microns. Possible reasons for the restriction in the movement of the water molecules in comparison with structural models of collagen II are discussed.

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Section: Nmr Experimentsmentioning

confidence: 99%

Pulsed field gradient NMR and nuclear magnetic relaxation studies of water mobility in hydrated collagen II

Knauss

Fleischer

Gründer

et al. 1996

Magnetic Resonance in Med

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“…diffusion, 11,12 anisotropic diffusion 13,14 and diffusion of different phases with individual diffusion coefficients. 15 Ordinary diffusion is well known and describes the behavior of isotropic systems such as bulk liquids.…”

Section: Introductionmentioning

confidence: 99%

Stray field gradient NMR reveals effects of hydrogen bonding on diffusion coefficients of pyridine in mesoporous silica

et al. 2001

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The diffusion of pyridine confined in mesoporous silica MCM-41 (d pore = 3.3 nm) was studied with stray field gradient (SFG) NMR diffusometry as a function of the filling factor of the mesopores at room temperature, employing a laboratory-built SFG setup. The translational diffusion of pyridine in MCM-41 is found to be anisotropic and the diffusion parallel to the pores' cylinder axes is much faster than that perpendicular to them. The parallel diffusion coefficient depends strongly on the filling level of the guest liquid inside the pores. For a filling level of 25%, which corresponds approximately to a monomolecular layer of pyridine molecules hydrogen bonded to surface -SiOH groups, a parallel diffusion coefficient of D jj = 1.0 × 10 −9 m 2 s −1 is found, which is slower than the diffusion coefficient of the bulk liquid (D = 1.6 × 10 −9 m 2 s −1 ). For higher filling factors the parallel diffusion coefficient increases and at a filling factor of 85% a diffusion coefficient of D jj = 6.8 × 10 −9 m 2 s −1 is reached. The perpendicular diffusion coefficient of D ? = 3.7 ± 2.0 × 10 −11 m 2 s −1 is independent of the filling factor. Employing additional 15 N MAS data for the pyridine inside the mesopores, a microscopic model of the diffusion is proposed, which depends on the exchange of the slowly diffusing hydrogen-bonded surface pyridine molecules with fast-diffusing free pyridine molecules inside the pores.

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“…The PFG NMR measurements were performed on a FEGRIS 400 laboratory-built spectrometer 11 at a proton resonance frequency of 400 MHz, using the conventional Hahn echo /2 sequence 1,3 -5 with observation times of 0.5-2 ms. Applying sufficiently large zeolite crystallites (with diameters ½30 and 100 µm for NaX, ½15 µm for NaA and ½1 mm for natural chabazite and a size ½200 ð 30 ð 30 µm 3 for ZSM-5), irrespective of the large diffusivities, the relatively short observation times ensured that the observed diffusivities were controlled by intracrystalline transport.…”

Section: Introductionmentioning

confidence: 99%

Combined quasi-elastic neutron scattering and NMR study of hydrogen diffusion in zeolites

et al. 1999

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On the Use of Pulsed Field Gradients in a High-Field NMR Spectrometer to Study Restricted Diffusion in Zeolites

Cited by 64 publications

References 0 publications

Pulsed field gradient NMR and nuclear magnetic relaxation studies of water mobility in hydrated collagen II

Pulsed field gradient NMR and nuclear magnetic relaxation studies of water mobility in hydrated collagen II

Stray field gradient NMR reveals effects of hydrogen bonding on diffusion coefficients of pyridine in mesoporous silica

Combined quasi-elastic neutron scattering and NMR study of hydrogen diffusion in zeolites

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