Dieter Freude, Institut für Experimentelle Physik I der Universität Leipzig Regional Annual Fundamental Science Seminar 2008, 28 May 2008

Spectroscopy, Diffusometry and Imaging of Spectroscopy, Diffusometry and Imaging of Confined Systems Confined Systems

Performed by Nuclear Magnetic ResonancePerformed by Nuclear Magnetic Resonance

Spectroscopy, Diffusometry and Imaging of Spectroscopy, Diffusometry and Imaging of Confined Systems Confined Systems

Performed by Nuclear Magnetic ResonancePerformed by Nuclear Magnetic Resonance

SpectroscopySpectroscopySpectroscopySpectroscopy

In 1882 Arthur Schuster first used the term spectroscopy during a

lecture at the Royal Institution. This word has both a Latin and Greek root (Greek skopein = to look).

In the year 1666 at Cambridge, Isaac Newton procured a triangular glass prism and let a ray of sunlight from a small round hole in the window illuminate it. He observed the image created thereby on a paper screen. The white light from the window dispersed into red, yellow, green, blue, and violet. He called the colors, invisible in the white sunlight, the “spectrum” (lat. spectrum = image in the soul).

I. Newton: handwriting from 6. 2. 1672 at the Royal Society. In an accompanying letter is the discovery of the dispersion of sunlight dated 1666.

A. Schuster in Encyclopedia Britannica (1911 ed.).

SpectroscopySpectroscopySpectroscopySpectroscopy

The physicist, astronomer and optician Carl August von Steinheil manufactured the used spectroscope.

This was the begin for the wide application of spectroscopy in science and technology.

In the year 1861 the physicist Gustav Robert Kirchhoff (left) and the chemist Robert Wilhelm Bunsen (right) published a paper “Chemical Analysis through Spectral Observations”.

G. Kirchhoff und R. Bunsen, Poggendorff's Ann. der Physik und Chemie 60 (1860) 161 und 63 (1861) 337.

NMR spectroscopyNMR spectroscopyNMR spectroscopyNMR spectroscopy

In the year 1945 nuclear magnetic resonance (NMR) was introduced almost simultaneously in Boston by Edward Mills Purcell (at left) and in Stanford by Felix Bloch (at right).

Right hand side, a spectrum measured in the current century with a cryogenic probe : Two dimensional spectrum of a natural pharmaceutical. Cross peaks in the 13C-1H spectrum show connectivities in the material.

Figure 6 from E. M. Purcell: Research in Nuclear Magnetism, Nobel Lecture, December 11, 1952

and

figure at right: www.bruker-biospin.com/natural_products.html

NMR diffusometryNMR diffusometryNMR diffusometryNMR diffusometry

NMR provides a simple and direct method for measuring self-diffusion coefficients down to about 10–14 m2s1.

The species under study is likely to be a molecule or ion.

NMR diffusometry does not require labeling and is effectively non-invasive.

For literature see: www.diffusion-fundamentals.org

Note that NMR diffusometry is fewer applied than NMR spectroscopy.Google counts 1 650 000 records for the latter, but only 2 560 for NMR diffusometry.

tDtr 62

Einstein‘s relation

Propagator description

dxxtxPtx 22 ),()(

)()0,( xxc

)4/exp()4(),( 22/1 tDxtDtxP

tDtx 2)(2

Hahn echoHahn echoHahn echoHahn echo B0

M

x

y

z 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

/2 pulse FID, pulsearound the dephasing around the rephasing echo y-axis x-magnetization x-axis x-magnetization

(r,t) = (r)·t (r,t) = (r,) + (r)·(t )

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

That means chemical shift anisotropy,dipolar interactions,first-order quadrupole interactions, and inhomogeneities of the magnetic susceptibility.

It results an enhancement in spectral resolution by line narrowing also for soft matter studies.

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

2

1cos3 2

rotor with samplein the rf coil zr

rot

θ

gradient coils forMAS PFG NMR

B0

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

om 54.7

3

1cosarcθ

rotor with samplein the rf coil zr

g gradient pulses

rot

θm

gradient coil

B0

3

4exp/

2

0g

DSS

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

rf pulses

g pulses

FID

g

Gz

r. f.

T

ecd

Δδ 1.0 2.0 / ppm

CH3 (n-but)

CH3 (iso)

CH2 (n-but) CH (iso)

Δδ = 0.4 ppm

gradient strength

Magnetic resonance imagingMagnetic resonance imagingMagnetic resonance imagingMagnetic resonance imaging

SIEMENS 7-Tesla-Scanner

Grand Opening for 7 T MRI Laboratory, 18-19 January 2008

The Max Planck Institute for Human Cognitive and Brain Sciences Leipzig celebrated the Opening of the new Seven Tesla Magnetic Resonance Imaging Laboratory.

The now achievable spatial resolution of 0.4 mm, allows researchers to traces brain changes over time – such as those during music training – much more precisely.

Note that whole body scanners with a magnetic field strength of 7 T or above are not certified as a medical device for human use. Therefore, it is for probands, not for patients.

Imaging by pulsed gradientsImaging by pulsed gradientsImaging by pulsed gradientsImaging by pulsed gradients

rf pulses

Gz

Gx

Gy

25 ms

25 ms

t

t

t

t

t

/2

Gz = 2 mT/m

Gy = (n/128) 0,2 mT/m 128 n128

Gx = 0,5 mT/m

gradient pulses

NMR signal

E

N

kx

ky

E describes in the figure above the development, in which Gx was chosen to be negative and Gy positive. N is the detection path, in which Gy = 0 and Gx is positive.

rf pulses, gradient pulses and the time signal are shown in the figure at left.

Blood oxygenation level dependent (BOLD)Blood oxygenation level dependent (BOLD)contrast in fMRI studiescontrast in fMRI studies

Blood oxygenation level dependent (BOLD)Blood oxygenation level dependent (BOLD)contrast in fMRI studiescontrast in fMRI studies

Thies H. Jochimsen and Harald E. Möller: Increasing specificity in functional magnetic resonance imaging by estimation of vessel size based on changes in blood oxygenation, NeuroImage 40 (2008) 228–236

Functional magnetic resonance imaging (fMRI) of the human brain is usually based on measuring local changes in blood oxygenation. Hemoglobin is diamagnetic when oxygenated but paramagnetic when deoxygenated. The blood oxygenation level dependent (BOLD) contrast is a consequence of neuronal activation in the brain. The paramagnetic deoxyhemoglobin causes changes in magnetic susceptibility of blood. It is closely related to oxygen delivery and consumption and expected to correlate with neuronal activity. The BOLD contrast reflects the imbalance between the local oxygen demand and delivery.

But BOLD contrast can be problematic since the contrast reflects changes in blood oxygenation which can be distant from the activated site, e.g. in the presence of large veins. In the work cited below, a novel approach is presented to increase specificity, i.e. to confine the origin of the BOLD contrast to the microvasculature, by predicting the average venous vessel radius in activated voxels, and to filter out those voxels whose contrast is dominated by large veins.

Filtering out voxels whose contrast is dominated Filtering out voxels whose contrast is dominated by large veinsby large veins

Filtering out voxels whose contrast is dominated Filtering out voxels whose contrast is dominated by large veinsby large veins

Maps of the average blood vessel radius of activated voxels (volumetric pixel) overlaid on T1-weighted images. Values are color-coded by the logarithm of the average vessel size, ranging from 1 to 100 μm. The top map shows the activation pattern with all voxels included. In the bottom map, all activated voxels withr > 30 μm are removed from the pattern.

Thies H. Jochimsen and Harald E. Möller: NeuroImage 40 (2008) 228–236

http://dericbownds.net/uploaded_images/aron.pdf

Adam R. Aron, Tim E. Behrens, Steve Smith, Michael J. Frank, and Russell A. Poldrack: Triangulating a Cognitive Control Network Using Diffusion-Weighted Magnetic Resonance Imaging (MRI) and Functional MRI, The Journal of Neuroscience, April 4, 2007 • 27(14):3743–3752 • 3743

Diffusion-weighted tractography results. A, 3-D rendering of the tracts between the right IFC, the right preSMA, and the right STN region. B, Triangulation method for determining the third point in a network from the other two. Tracts originating in one brain area are overlaid on tracts originating from another. The overlap is superimposed on a gray matter mask in standard space.

preSMA: presupplementary motor area

IFC: inferior frontal cortex

STN: subthalamic nucleus

Diffusion-weighted imaging (DWI) Diffusion-weighted imaging (DWI) and functional magnetic resonance imaging (fMRI)and functional magnetic resonance imaging (fMRI)

Diffusion-weighted imaging (DWI) Diffusion-weighted imaging (DWI) and functional magnetic resonance imaging (fMRI)and functional magnetic resonance imaging (fMRI)

MAS PFG NMR studies of the self-diffusion MAS PFG NMR studies of the self-diffusion of acetone-alkane mixtures in nanoporous silica gelof acetone-alkane mixtures in nanoporous silica gel

MAS PFG NMR studies of the self-diffusion MAS PFG NMR studies of the self-diffusion of acetone-alkane mixtures in nanoporous silica gelof acetone-alkane mixtures in nanoporous silica gel

The self-diffusion coefficients of mixtures of acetone with several alkanes were studied by means of magic-angle spinning pulsed field gradient nuclear magnetic resonance (MAS PFG NMR). Silica gels with different nanopore sizes at ca. 4 and 10 nm and a pore surface modified with trimethylsilyl groups were provided by Takahashi et al. (1). The silica gel was loaded with acetone –alkane mixtures (1:10). The self-diffusion coefficients of acetone in the small pores (4 nm) shows a zigzag effect depending on odd or even numbers of carbon atoms of the alkane solvent.

Moises Fernandez, André Pampel, Ryoji Takahashi, Satoshi Sato, Dieter Freude, Jörg Kärger ;Phys. Chem. Chem. Phys., in print

Fig. 3. Pore size distribution of the specimens of nanoporous silica gel Nm () and B1m () used in the diffusion measurements.

0 5 10 15

0

0.2

0.4

Pore diameter d / nm

11

3p

gnm

cm/dd

--

dV

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

0,1

1 = 600 ms = 2 ms

Em / acetone + alkane (C6,C

7,C

8,C

9)

S /

S0

g 2 / T 2m-2

nonane C9

octane C8

heptane C7

hexane C6

Semi-logarithmic plot of the decay of the CH3 signal of ketone in binary mixture with acetone at 298 K. The diffusion time is = 600 ms and a gradient pulse length is = 2 ms:

/ ppm0.40.81.

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 Em material as function of increasing pulsed gradient strength for a diffusion time = 600 ms:

6 7 8 9 10

8,0x10-12

1,0x10-11

1,2x10-11

1,4x10-11

Acetone diffusivity in alkane mixture

D /

m2 s-1

Carbon number of alkane solvent

% ( = 600 ms) % ( = 800 ms) % ( = 1200 ms) The diffusivities of acetone dissolved in odd-carbon

number n-alkanes exceed those of acetone dissolved in even-carbon number n‑alkanes by about 50%.This finding shows the odd-even zig-zag effect and suggests the formation of acetone – n‑alkane complex-like assemblages in the narrow-pore silica gel.

In situ monitoring of catalytic conversion of In situ monitoring of catalytic conversion of molecules in zeolites by molecules in zeolites by 11H, H, 22H and H and 1313C MAS NMRC MAS NMR

In situ monitoring of catalytic conversion of In situ monitoring of catalytic conversion of molecules in zeolites by molecules in zeolites by 11H, H, 22H and H and 1313C MAS NMRC MAS NMR

Kinetics of a double-bond-shift reaction, hydrogen exchange and 13C-label scrambling of n-butene in H-ferrierite

6 4 2 0 / ppm

–CH= 5.6

CH3– 1.7

65 min

4 min

1H MAS NMR spectra of n-but-1-ene-d8 adsorbed on H-FER2 (T=360K). Hydrogen transfer occurs from the acidic hydroxyl groups of the zeolite to the deuterated butene molecules. Both methyl and methene groups of but-2-ene are involved in the H/D exchange. The ratio between the intensities of the CH3 and CH groups in the final spectrum is 3:1.

*

**

*

**

*

126

200 160 120 80 40 0 / ppm

17

13

*

17 min at 323 K

20 h at 323 K

*

**

*

**

*

126

200 160 120 80 40 0 / ppm

17

13

*

17 min at 323 K

20 h at 323 K

13C CP/MAS NMR spectra of [2-13C]-n-but-1-ene adsorption on H-FER in dependence on reaction time. Asterisks denote spinning side-bands. The appearance of the signals at 13 and 17 ppm and decreasing intensity of the signal at 126 ppm show the label scrambling.

1.7

5.0 2.0

0 2 4 6 / ppm

1.0

5.9

5 min

18.5 h

2H MAS NMR spectra of n-but-1-ene-d8 adsorbed on H‑FER (T = 333K). n-But-1-ene undergoes readily a double-bond-shift reaction, when it is adsorbed on ferrierite. The reaction becomes slow enough to observe the kinetics , if the catalyst contains only a very small concentration of Brønsted acid sites.

A.G. Stepanov, S.S. Arzumanov, M. V. Luzkin, H. Ernst, D. Freude: In situ monitoring of n-butene conversion on H-ferrierite by 1H, 2H and 13C MAS NMR, J. Catal. 229 (2005) 243-251.

I acknowledge support from

Ministry of Science, Technology and Innovationin the frame of the Brain Gain Malaysia Programme

Academy of Sciences Malaysia

Ibnu Sina Institute for Fundamental Science Studiesat Universiti Teknologi Malaysia

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