MQMAS NMR: Experimental Strategies and Applications

Amoureux, Jean‐Paul; Pruski, Marek

doi:10.1002/9780470034590.emrstm0319.pub2

Cited by 16 publications

(12 citation statements)

References 133 publications

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“…The details of MQMAS theory and its fundamentals are described explicitly in the literature [17,18,57,58,60], but we described here a few empirical trends in the appearance of the lineshapes in i-sheared MQMAS spectroscopy, in order to point out typical connections between the spectroscopic features and the changes to the NMR parameters. Similar trends have been previously illustrated by Amoureux and Pruski [61]. The diagonal, or the chemical shift line, which is drawn in each spectrum in Figure 7, provides the most important guidance for addressing the identity of each resonance.…”

Section: Disorder Observed By Mqmas Spectroscopysupporting

confidence: 77%

A Practical Review of NMR Lineshapes for Spin-1/2 and Quadrupolar Nuclei in Disordered Materials

Chen

2020

IJMS

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NMR is a powerful spectroscopic method that can provide information on the structural disorder in solids, complementing scattering and diffraction techniques. The structural disorder in solids can generate a dispersion of local magnetic and electric fields, resulting in a distribution of isotropic chemical shift δiso and quadrupolar coupling CQ. For spin-1/2 nuclei, the NMR linewidth and shape under high-resolution magic-angle spinning (MAS) reflects the distributions of isotropic chemical shift, providing a rich source of disorder information. For quadrupolar nuclei, the second-order quadrupolar broadening remains present even under MAS. In addition to isotropic chemical shift, structural disorder can impact the electric field gradient (EFG) and consequently the quadrupolar NMR parameters. The distributions of quadrupolar coupling and isotropic chemical shift are superimposed with the second-order quadrupolar broadening, but can be potentially characterized by MQMAS (multiple-quantum magic-angle spinning) spectroscopy. We review analyses of NMR lineshapes in 2D DQ–SQ (double-quantum single-quantum) and MQMAS spectroscopies, to provide a guide for more general lineshape analysis. In addition, methods to enhance the spectral resolution and sensitivity for quadrupolar nuclei are discussed, including NMR pulse techniques and the application of high magnetic fields. The role of magnetic field strength and its impact on the strategy of determining optimum NMR methods for disorder characterization are also discussed.

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Section: Disorder Observed By Mqmas Spectroscopysupporting

confidence: 77%

A Practical Review of NMR Lineshapes for Spin-1/2 and Quadrupolar Nuclei in Disordered Materials

Chen

2020

IJMS

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“…A more popular approach, using only conventional hardware, is the multiple-quantum (MQ) MAS experiment, 21,24 where manipulation of the nuclear spins and sample rotation are combined to remove the second-order quadrupolar broadening. MQMAS is a two-dimensional experiment where different transitions within the multi-level nuclear spin systems are correlated in two different time periods in the pulse sequence.…”

Section: Experimental Solid-state Nmr Spectroscopymentioning

confidence: 99%

Combining solid-state NMR spectroscopy with first-principles calculations – a guide to NMR crystallography

2016

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Recent advances in the application of first-principles calculations of NMR parameters to periodic systems have resulted in widespread interest in their use to support experimental measurement. Such calculations often play an important role in the emerging field of "NMR crystallography", where NMR spectroscopy is combined with techniques such as diffraction, to aid structure determination. Here, we discuss the current state-of-the-art for combining experiment and calculation in NMR spectroscopy, considering the basic theory behind the computational approaches and their practical application. We consider the issues associated with geometry optimisation and how the effects of temperature may be included in the calculation. The automated prediction of structural candidates and the treatment of disordered and dynamic solids are discussed. Finally, we consider the areas where further development is needed in this field and its potential future impact.

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“…The T2 relaxation data was achieved using a 30 mm 23 Na MRI resonator, using a spin-echo sequence with a 10 kHz (25 µs, π/2) excitation pulse and a 5 kHz (50 µs, π) refocusing pulse, with a variable delay between the pulses. All data was processed using the Bruker Dynamics Centre and Topspin (Billerica, MA) software, and simulated using the DMFit [12].…”

Section: Nmrmentioning

confidence: 99%

“…Therefore, significant resolution enhancement is needed to deconvolute the NMR resonances and to accurately determine the number of sodium environments in the glasses. Two-dimensional 3QMAS experiments separate the anisotropic quadrupole broadening (x-axis, F2) experienced by spin >1/2 nuclei, such as sodium, and the isotropic chemical shift information (y-axis, F1), allowing greater resolution to be achieved and overlapping sites to be deconvoluted [12]. However, the MAS technique is destructive as the sample needs to rotate at 12-13 kHz (720,000 to 780,000 rpm, to reduce anisotropic dipolar interactions between spins) and is not routinely applied to ancient artefacts.…”

Section: Introductionmentioning

confidence: 99%

Structural and chemical heterogeneity in ancient glass probed using gas overcondensation, X-ray tomography, and solid-state NMR

Rigby

Stevens

Meersmann

et al. 2020

Materials Characterization

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Rare ancient glasses have complex, multi-scale structures requiring more sophisticated and non-destructive pore characterisation techniques than usual. Homotattic patch models for nitrogen adsorption gave better fits to the isotherm data, more accurate void space descriptors, and also greater understanding of the underlying physical factors affecting adsorption, than standard BET. These homotattic patch models revealed the critical role of iron impurities in determining adsorption behaviour. Non-destructive sodium-23 NMR relaxometry validated the homotattic patch model for some natron glasses, and, in turn, was validated using multiple quantum magic-angle spinning (MQMAS) 23 Na NMR. X-ray tomography images of the glasses showed the presence of large macroporous bubbles, while FEG-SEM revealed nanopores within the glass matrix. A newly-developed, gas overcondensation technique, suitable for small amounts of low porosity material, assessed the inter-relationship between the disparate levels in this hierarchical porosity. This technique demonstrated that the nanoporosity did not form a 'corona' around the bubbles, due to leaching from the glass, as initially supposed from tomography data, but was completely disconnected, and, thus, is probably associated with glass alkalinity. Gas overcondensation is demonstrated as a non-destructive alternative to mercury porosimetry for probing multi-scale porosity in rare artefacts.

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MQMAS NMR: Experimental Strategies and Applications

Cited by 16 publications

References 133 publications

A Practical Review of NMR Lineshapes for Spin-1/2 and Quadrupolar Nuclei in Disordered Materials

A Practical Review of NMR Lineshapes for Spin-1/2 and Quadrupolar Nuclei in Disordered Materials

Combining solid-state NMR spectroscopy with first-principles calculations – a guide to NMR crystallography

Structural and chemical heterogeneity in ancient glass probed using gas overcondensation, X-ray tomography, and solid-state NMR

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