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by Dieter Freude and Jörg Kärger, Institut für Experimentelle Physik der Universität Leipzig MAS PFG NMR, MAS PFG NMR, Magic-Angle Spinning Pulsed Field Gradient Nuclear Magnetic Magic-Angle Spinning Pulsed Field Gradient Nuclear Magnetic Resonance, Resonance, a New a New Tool for Diffusometry of Interface Tool for Diffusometry of Interface Materials Materials rotor with sample in the rf coil z r rot 10 kHz θ gradient coils for pulsed field gradients, B 0 = 9 21 T

By Dieter Freude and Jörg Kärger, Institut für Experimentelle Physik der Universität Leipzig MAS PFG NMR, Magic-Angle Spinning Pulsed Field Gradient Nuclear

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Page 1: By Dieter Freude and Jörg Kärger, Institut für Experimentelle Physik der Universität Leipzig MAS PFG NMR, Magic-Angle Spinning Pulsed Field Gradient Nuclear

by Dieter Freude and Jörg Kärger, Institut für Experimentelle Physik der Universität Leipzig

MAS PFG NMR, MAS PFG NMR, Magic-Angle Spinning Pulsed Field Gradient Nuclear Magnetic Resonance,Magic-Angle Spinning Pulsed Field Gradient Nuclear Magnetic Resonance, a New a New Tool for Diffusometry of Interface MaterialsTool for Diffusometry of Interface Materials

MAS PFG NMR, MAS PFG NMR, Magic-Angle Spinning Pulsed Field Gradient Nuclear Magnetic Resonance,Magic-Angle Spinning Pulsed Field Gradient Nuclear Magnetic Resonance, a New a New Tool for Diffusometry of Interface MaterialsTool for Diffusometry of Interface Materials

rotor with samplein the rf coil zr

rot 10 kHz

θ

gradient coils forpulsed field gradients,

maximum 1 T / m

B0 = 9 21 T

Page 2: By Dieter Freude and Jörg Kärger, Institut für Experimentelle Physik der Universität Leipzig MAS PFG NMR, Magic-Angle Spinning Pulsed Field Gradient Nuclear

Introduction to pulsed field gradient NMRIntroduction to pulsed field gradient NMRIntroduction to pulsed field gradient NMRIntroduction to pulsed field gradient NMR

r.f. pulse t

/2

gradient pulse tgmax = 25 T / m

magnetization

t

free induction Hahn echo

B0

M x

y

z B0

x

y

z

5 4

1 2

3

B0

x

y

z

1 2

5 4

3

B0

M x

y

z

Spin recovery by Hahn echo without diffusion of nuclei:

Page 3: By Dieter Freude and Jörg Kärger, Institut für Experimentelle Physik der Universität Leipzig MAS PFG NMR, Magic-Angle Spinning Pulsed Field Gradient Nuclear

Pulsed field gradient NMR diffusion measurements base on NMR pulse sequences generating a spin echo, like the Hahn echo (two pulses) or the stimulated spin echo (three pulses). At right, the 13-intervall sequence for alternating gradients consisting of 7 rf pulses, 4 gradient pulses of duration , intensity g, observation time and 2 eddy current quench pulses is described.

PFG NMR, signal decay by diffusion of the nucleiPFG NMR, signal decay by diffusion of the nucleiPFG NMR, signal decay by diffusion of the nucleiPFG NMR, signal decay by diffusion of the nuclei

free induction decay

rf pulses

gradient pulses

g

ecd

kDSpg

DSS

exp

2

4exp 0

2

0

The self-diffusion coefficient D of molecules in bulk phases, in confined geometries and in biologic materials is obtained from the amplitude S of the free induction decay in dependence on the field gradient intensity g by the equation

Page 4: By Dieter Freude and Jörg Kärger, Institut für Experimentelle Physik der Universität Leipzig MAS PFG NMR, Magic-Angle Spinning Pulsed Field Gradient Nuclear

Fast rotation (160 kHz) of the sample about an axis oriented at 54.7° (magic-angle) with respect to the static magnetic field removes all broadening effects with an angular dependency of

o7.543

1cosarc

Chemical shift anisotropy,internuclear dipolar interactions,first-order quadrupole interactions, and inhomogeneities of the magnetic susceptibilityare averaged out.

It results an enhancement in spectral resolution by line narrowing for solids and for soft matter.The transverse relaxation time is prolonged.

High-resolution solid-state MAS NMRHigh-resolution solid-state MAS NMRHigh-resolution solid-state MAS NMRHigh-resolution solid-state MAS NMR

.2

1cos3 2 rot

zr

θ

B0

Page 5: By Dieter Freude and Jörg Kärger, Institut für Experimentelle Physik der Universität Leipzig MAS PFG NMR, Magic-Angle Spinning Pulsed Field Gradient Nuclear

MAS PFG NMR for NMR diffusometryMAS PFG NMR for NMR diffusometryMAS PFG NMR for NMR diffusometryMAS PFG NMR for NMR diffusometry

zr

θm

B0

0.51.01.52.0

δ = 0.02 ppm

ppm

-2024ppm

* * ****

ωr = 0 kHzωr = 1 kHz

ωr = 10 kHz

FAU Na-X , n-butane + isobutane Δδ 1.0 2.0 / ppm

CH3 (n-but)

CH3 (iso)

CH2 (n-but) CH (iso)

Δδ = 0.4 ppm

gradient strength

Application of MAS technique in addition to PFG improves drastically the spectral resolution.

This allows the study of multi-component diffusion in confined geometry or soft matter.

Page 6: By Dieter Freude and Jörg Kärger, Institut für Experimentelle Physik der Universität Leipzig MAS PFG NMR, Magic-Angle Spinning Pulsed Field Gradient Nuclear

Mixture diffusion in zeolite silicalite-1 Mixture diffusion in zeolite silicalite-1 Mixture diffusion in zeolite silicalite-1 Mixture diffusion in zeolite silicalite-1 The self-diffusion coefficient of n-butane, isobutane, and mixtures of both adsorbed in silicalite-1 were measured. It was shown that the diffusion coefficient of n-butane mixed with isobutane in silicalite-1 decreases with increasing amount of isobutane.

1.02.0 / ppm

gradient

strength

CH3 (n-butane)

CH3 (isobutane)

CH2 (n-butane)

CH (isobutane)

0.0 0.2 0.4 0.6 0.8 1.010

10

10

10

D / m2s1

n-butane molecules per intersection

mixtures

isobutane

n-butane

M. Fernandéz, J. Kärger, D. Freude, A. Pampel, J. M. van Baten, R. Krishna, Mixture diffusion in zeolites studied by MAS PFG NMR and molecular simulation, Microporous and Mesoporous Materials 105 (2007) 124-131.

The figure presents a discontinuity at 0.6 n-butane molecule per channel intersection due to the blocking effect of isobutane molecules in interchannel sites.

Page 7: By Dieter Freude and Jörg Kärger, Institut für Experimentelle Physik der Universität Leipzig MAS PFG NMR, Magic-Angle Spinning Pulsed Field Gradient Nuclear

MAS PFG NMR studies of the self-diffusion MAS PFG NMR studies of the self-diffusion of acetone-alkane mixtures in nanoporous glassof acetone-alkane mixtures in nanoporous glass

MAS PFG NMR studies of the self-diffusion MAS PFG NMR studies of the self-diffusion of acetone-alkane mixtures in nanoporous glassof acetone-alkane mixtures in nanoporous glass

The self-diffusion coefficients of mixtures of acetone with several alkanes were studied by MAS PFG NMR. Glasses with different nanopore sizes of 4 and 10 nm and a pore surface modified with trimethylsilyl groups were loaded with acetone –alkane mixtures (1:10).

(ppm)0.40.81.21.62.02.42.8

CH3

CH3

CH2

acetone

octane

gradient

strength

Stack plot of the 1H MAS PFG NMR spectra at 10 kHz of the 1:10 acetone and octane mixture absorbed in 4-nm-glass as function of increasing pulsed gradient strength for a diffusion time = 600 ms.

Semi-logarithmic plot of the decay of the acetone CH3 signal in binary mixtures with alkane in 4-nm-glass at 298 K. The diffusion time is = 600 ms and the gradient pulse length is = 2 ms.

0,00 0,05 0,10 0,15 0,20 0,250,01

0,1

1

S /

S0

g 2 / T

2m

-2

nonane C9

octane C 8

heptane C 7 hexane C

6

Page 8: By Dieter Freude and Jörg Kärger, Institut für Experimentelle Physik der Universität Leipzig MAS PFG NMR, Magic-Angle Spinning Pulsed Field Gradient Nuclear

Diffusion coefficient of acetone in mixture within 4-nm-glass in dependence on the number of carbons in the alkane solvent. The measurements were carried out with diffusion time = 600 ms, = 800 ms and = 1200 ms and the gradient pulse length = 2 ms.

The self-diffusion coefficients of acetone shows a zigzag effect depending on odd or even numbers of carbon atoms of the alkane solvent in the small pores (4 nm), but not in the larger pores (10 nm).

Zigzag effect of the self-diffusion of acetoneZigzag effect of the self-diffusion of acetonein 4-nm-nanoporous glassin 4-nm-nanoporous glass

Zigzag effect of the self-diffusion of acetoneZigzag effect of the self-diffusion of acetonein 4-nm-nanoporous glassin 4-nm-nanoporous glass

6 7 8 9 10

8,0x10-12

1,0x10-11

1,2x10-11

1,4x10-11

D /

m2s

-1

Carbon number of alkane solvent

% ( = 600 ms)

% ( = 800 ms)

% ( = 1200 ms)

M. Fernandez, A. Pampel, R. Takahashi, S. Sato, D. Freude, J. Kärger, Revealing complex formation in acetone-nalkane mixtures by MAS PFG NMR diffusion measurement in nanoporous hosts, Phys. Chem. Chem. Phys. 10 (2008) 4165.

Page 9: By Dieter Freude and Jörg Kärger, Institut für Experimentelle Physik der Universität Leipzig MAS PFG NMR, Magic-Angle Spinning Pulsed Field Gradient Nuclear

Studies of free and confined liquid crystalsStudies of free and confined liquid crystalsStudies of free and confined liquid crystalsStudies of free and confined liquid crystals

b

T = 324 K

1 7 / ppm

c

T = 299 K

a

HH

HH

HH

HH

(CH2)4CH3NC

1 2 2 3

4 – 6 7

1

2

3

4 5

6 7

0,016 ppm

0,25 ppm

The chemical structure of 5CB (a). 1H MAS NMR spectra of 5CB confined in Bioran glasses with a pore diameter of 200 nm above (b) and below (c) the isotropization temperature Tc.

Tc = 308,5 K

crystalline nematic isotrop

T = 297,2 K

Temperature dependence of the 1H MAWS NMR linewidth fwhm for bulk 5CB () and for 5CB confined in Bioran glasses with a pore diameter of 30 nm () and 200 nm (). Empty symbols correspond to the isotropic phase and full symbols correspond to the nematic / crystalline phase.

T / K

280 290 300 310 320 330 340 0

50

100

150

200

250

300

fwh

m /

Hz

E. E. Romanova, F. Grinberg, A. Pampel, J. Kärger, D. Freude, Diffusion studies in confined nematic liquid crystals by MAS PFG NMR, J. Magn. Reson. 196 (2009) 110-114.

Page 10: By Dieter Freude and Jörg Kärger, Institut für Experimentelle Physik der Universität Leipzig MAS PFG NMR, Magic-Angle Spinning Pulsed Field Gradient Nuclear

Diffusion of free and confined liquid crystalsDiffusion of free and confined liquid crystalsDiffusion of free and confined liquid crystalsDiffusion of free and confined liquid crystals

0 11010 21010 31010 41010 51010

0.1

1

T = 334 K, 200-nm-BioranT = 299 K, 200-nm-BioranT = 334 K, 30-nm-BioranT = 299 K, 30-nm-Bioran

k / sm-2

S / S0

3.0 3.1 3.2 3.3 3.4

0.1

1

T 1 103 / K1

D / 10 -10 m2 s1

T / K334 319 299 294

1H MAS PFG NMR spin echo attenuation Temperature dependence of the diffusion coefficient D of bulk 5CB () and of 5CB confined in Bioran glasses with pore diameter of 30 nm () and 200 nm ().The diffusivities were measured at 10 kHz rotation frequency, except three values for Bioran-200-nm, which were measured at 5 kHz () and without rotation (). Empty symbols correspond to the isotropic phase and full symbols correspond to the crystalline phase.

It is found that the confinement of the liquid crystal 5CB in porous glasses with mean pore diameters of 30 and 200 nm does not notably change its self-diffusion behavior in comparison with the bulk state.

D for T = 334 K isotropic phase

D for T = 299 K nematic phase

bulk phase 5.5 1011 m2s1 2.9 1011 m2s1

200 - nm- Bioran 4.8 1011 m2s1 2.0 1011 m2s1

30-nm-Bioran 4.2 1011 m2s1 2.7 1011 m2s1

Page 11: By Dieter Freude and Jörg Kärger, Institut für Experimentelle Physik der Universität Leipzig MAS PFG NMR, Magic-Angle Spinning Pulsed Field Gradient Nuclear

Jörg Kärger and Dieter Freude acknowledge contributions from

Dr. Moisés Fernández

Dr. Farida Grinberg

Dr. André Pampel

Dr. Ekaterina Romanova

For request of reprints of the presentation and the three publications send E-mail to [email protected].

Page 12: By Dieter Freude and Jörg Kärger, Institut für Experimentelle Physik der Universität Leipzig MAS PFG NMR, Magic-Angle Spinning Pulsed Field Gradient Nuclear

Diffusion Fundamentals III

Basic Principles of Theory, Experiment and ApplicationAugust 23rd - 26th, 2009

Athens, Greece

In the biennial series of meetings devoted to the basic principles of diffusion theory, experiment and application, researchers from the interdisciplinary fields of diffusion are invited to exchange the most recent results of research, which are of general interest to the whole community. All presentations are scheduled to address a broad, interdisciplinary audience avoiding parallel sessions. Contributions will be presented at the web-site diffusion-fundamentals.org, especially in the Diffusion Fundamentals Online Journal.

Page 13: By Dieter Freude and Jörg Kärger, Institut für Experimentelle Physik der Universität Leipzig MAS PFG NMR, Magic-Angle Spinning Pulsed Field Gradient Nuclear

ReferencesReferencesReferencesReferences

Refererences to the first combined application of PFG NMR with MAS are:

H. C. Gaede, K. Gawrisch, Multi-dimensional pulsed field gradient magic angle spinning NMR experiments on membranes, Magnetic Resonance in Chemistry 42 (2004) 115-122.

P. Rousselot-Pailley, D. Maux, J. M. Wieruszeski, J. L. Aubagnac, J. Martinez, G. Lippens, Impurity detection in solid-phase organic chemistry: Scope and limits of HR MAS NMR, Tetrahedron 56 (2000) 5163-5167.

H. Schröder, High resolution magic angle spinning NMR for analyzing small molecules attached to solid support, J. Comb. Chem. 6 (2003) 741-753.

S. Viel, F. Ziarelli, S. Caldarelli, Enhanced diffusion-edited NMR spectroscopy of mixtures using chromatographic stationary phases, Proceedings of the National Academy of Sciences of the United States of America 100 (2003) 9696-9698.

A. Pampel, M. Fernandez, D. Freude, J. Kärger, New options for measuring molecular diffusion in zeolites by MAS PFG NMR, Chem. Phys. Lett. 407 (2005) 53-57.

A. Pampel, F. Engelke, P. Galvosas, C. Krause, F. Stallmach, D. Michel, J. Kärger, Selective multi-component diffusion measurement in zeolites by pulsed field gradient NMR, Microporous Mesoporous Mater. 90 (2006) 271-277.

Refrences to the three studies summarized in the present contribution are:

M. Fernandez, J. Kärger, D. Freude, A. Pampel, J. M. van Baten, R. Krishna, Mixture diffusion in zeolites studied by MAS PFG NMR and molecular simulation, Microporous and Mesoporous Materials 105 (2007) 124-131.

M. Fernandez, A. Pampel, R. Takahashi, S. Sato, D. Freude, J. Kärger, Revealing complex formation in acetone-nalkane mixtures by MAS PFG NMR diffusion measurement in nanoporous hosts, Phys. Chem. Chem. Phys. 10 (2008) 4165-4171.

E. E. Romanova, F. Grinberg, A. Pampel, J. Kärger, D. Freude, Diffusion studies in confined nematic liquid crystals by MAS PFG NMR, J. Magn. Reson. 196 (2009) 110-114.