Spin Echo NMR Diffusion Studies

Stallmach, Frank; Galvosas, Petrik

doi:10.1016/s0066-4103(07)61102-8

Cited by 130 publications

(123 citation statements)

References 153 publications

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“…By the application of appropriately constructed sequences of rf pulses and gradient pulses (see bottom left of Fig. 4 and further examples in [47]) an NMR signal (the "spin echo") may be generated which is sensitive to the differences in the locations which each individual molecule has assumed during the two gradient pulses. Hence, with the Einstein relation, Eq.…”

Section: Recording Guest Diffusion During Transient Sorption Experimentsmentioning

confidence: 99%

A new view of diffusion in nanoporous materials

Kärger

Chmelik

Heinke

et al. 2010

Chemie Ingenieur Technik

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Diffusion is among the rate-controlling processes in the technological application of nanoporous materials, including separation and conversion processes. Over decades, the different techniques of diffusion measurements yielded controversial results. The benefit of novel measuring techniques which, by immediate visual evidence, exemplify the self-consistency of the resulting diffusivities is shown. Furthermore, by quantifying the permeabilities through the particle surfaces and by correlating the rate of molecular uptake and release with the molecular mobilities, these techniques are able to identify and to explore additional transport resistances which so far, though being rate-limiting in numerous cases, were outside the range of direct experimental observation.

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Section: Recording Guest Diffusion During Transient Sorption Experimentsmentioning

confidence: 99%

A new view of diffusion in nanoporous materials

Kärger

Chmelik

Heinke

et al. 2010

Chemie Ingenieur Technik

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“…The aim of this contribution is to investigate the concentration and temperature dependence of self-diffusion of benzene in MOF-5 by the PFG NMR spin echo technique [22] and by diffusion-relaxation correlation spectroscopy (DRCOSY) [24,25]. In recent work, we found an agreement between the results of PFG NMR [26] and MD simulations [13] at 298 K at a relatively low loading of six benzene molecules per unit cell of MOF-5.…”

Section: Introductionmentioning

confidence: 67%

“…For both methods the relation to the self-diffusion coefficient is provided by the Einstein relation (3-dimensional case) [30,31], using the primary and the stimulated spin echo sequences [32], the NMR spin echo signal intensity is sensitive to the mean squared displacement r 2 (∆) during the time between the pair of pulsed field gradients (t = ∆, see Figure 2 and Equation 2). The spin echo intensity M (b) is measured as function of the socalled b-value, which depends on the gradient settings of the pulse sequence [22]. The b-value for a pair of rectangular gradient pulses is given by [22,30] …”

Section: Mof-5 Framework and Self-diffusionmentioning

confidence: 99%

“…The spin echo intensity M (b) is measured as function of the socalled b-value, which depends on the gradient settings of the pulse sequence [22]. The b-value for a pair of rectangular gradient pulses is given by [22,30] …”

Section: Mof-5 Framework and Self-diffusionmentioning

confidence: 99%

“…Meanwhile there exist a large number of computer simulations (see for example refs. [12][13][14][15]) and a few experimental techniques, such as interference and infrared microscopy [16][17][18], quasi elastic neutron scattering (QENS) [19][20][21] and pulsed field gradient (PFG) NMR [22,23], which allow one to determine guest diffusion in MOFs under non-equilibrium and equilibrium conditions, respectively.…”

Section: Introductionmentioning

confidence: 99%

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NMR studies of benzene mobility in metal-organic framework MOF-5

Hertel

Wehring

Amirjalayer

et al. 2011

Eur. Phys. J. Appl. Phys.

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Abstract. The concentration and temperature dependence of the self-diffusion of benzene adsorbed in the metal-organic framework MOF-5 (IRMOF-1) is studied by pulsed field gradient (PFG) NMR spectroscopy.When increasing the loading from 10 to 20 molecules per unit cell of MOF-5, the experimental diffusion data drop by a factor of about three while current molecular dynamic (MD) simulations predict slightly increasing diffusion coefficients for this range of loadings. The observation is rationalized using the recently predicted clustering of adsorbate molecules in microporous systems for temperatures well below the adsorbate critical temperature. Necessary improvements of molecular simulation models for predicting diffusivities under such conditions are discussed.

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In situ determination of surface relaxivities for unconsolidated sediments

Duschl

Galvosas

Brox

et al. 2015

Water Resources Research

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NMR relaxometry has developed into a method for rapid pore-size determination of natural porous media. Nevertheless, it is prone to uncertainties because of unknown surface relaxivities which depend mainly on the chemical composition of the pore walls as well as on the interfacial dynamics of the pore fluid. The classical approach for the determination of surface relaxivities is the scaling of NMR relaxation times by surface to volume ratios measured by gas adsorption or mercury intrusion. However, it is preferable that a method for the determination of average pore sizes uses the same substance, water, as probe molecule for both relaxometry and surface to volume measurements. One should also ensure that in both experiments the dynamics of the probe molecule takes place on similar length scales, which are in the order of some microns. Therefore, we employed NMR diffusion measurements with different observation times using bipolar pulsed field gradients and applied them to unconsolidated sediments (two purified sands, two natural sands, and one soil). The evaluation by Mitra's short-time model for diffusion in restricted environments yielded information about the surface to volume ratios which is independent of relaxation mechanisms. We point out that methods based on NMR diffusometry yield pore dimensions and surface relaxivities consistent with a pore space as sampled by native pore fluids via the diffusion process. This opens a way to calibrate NMR relaxation measurements with other NMR techniques, providing information about the pore-size distribution of natural porous media directly from relaxometry.

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Spin Echo NMR Diffusion Studies

Cited by 130 publications

References 153 publications

A new view of diffusion in nanoporous materials

A new view of diffusion in nanoporous materials

NMR studies of benzene mobility in metal-organic framework MOF-5

In situ determination of surface relaxivities for unconsolidated sediments

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