Dynamic Nuclear Polarisation Enhanced NMR of Low Abundance, Low Gamma and Difficult to Observe Nuclei



Brownbill, N
(2018) Dynamic Nuclear Polarisation Enhanced NMR of Low Abundance, Low Gamma and Difficult to Observe Nuclei. PhD thesis, University of Liverpool.

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Abstract

Nuclear magnetic resonance is one of the most powerful spectroscopic techniques available for probing molecular structure and nuclear interactions. The technique suffers from low sensitivity, reducing its application in many cases, or leading to very long experimental times. Over the last two decades, a signal enhancement technique known as dynamic nuclear polarisation (DNP) has provided a remarkable opportunity to improve the signal of NMR, particularly in the solid state. Three common sensitivity related challenges in solid-state NMR are the low natural abundance of NMR active species of certain elements, nuclei with low gyromagnetic ratios and the difficulty in assigning and quantifying disordered systems. It is shown that despite the benefit of DNP typically being expected to decrease with magnetic field, that this technique can enable natural abundance 17O spectra to be recorded at 18.8 T allowing well resolved, time efficient NMR spectra to be obtained. Direct DNP of low gyromagnetic ratio 89Y facilitates cross effect DNP with narrow line radical trityl-OX063, allowing observation and assignment of surface signals of yttrium oxide in minutes. For amorphous polymers, where high magnetic field is not beneficial, large enhancements can facilitate natural abundance carbon correlation spectra in less than a day, which coupled with a quantitative indirect NMR approach can allow for previously uncharacterised systems to be well understood.

Item Type: Thesis (PhD)
Divisions: Fac of Science & Engineering > School of Chemistry
Depositing User: Symplectic Admin
Date Deposited: 20 Aug 2019 15:25
Last Modified: 29 Sep 2020 08:52
DOI: 10.17638/03030301
Supervisors:
URI: http://livrepository.liverpool.ac.uk/id/eprint/3030301