Jeremy Titman, Walter Köckenberger and Boyan Bonev from the Schools of Chemistry, Physics and Life Sciences have recently obtained £3M of funding to establish a DNP-enhanced solid-state NMR Facility at Nottingham. The instrumentation was delivered at the beginning of October, and installation, which will take at least one month, is currently underway.
Solid-state nuclear magnetic resonance (NMR) is a powerful method for studying the molecular structure and dynamics of a broad range of systems from heterogeneous materials to biological molecules. However, solid-state NMR suffers from low sensitivity, because of the small nuclear spin polarizations involved even with high magnetic fields, and so long acquisition times or large sample volumes are required. The problem of sensitivity becomes overwhelming for dilute species, so that measurements of adsorbates on surfaces, molecules at interfaces or isotopes with low natural abundance are often impossible.
Weak NMR signals can be enhanced by dynamic nuclear polarization (DNP), which involves transfer of electron spin polarization from radicals implanted in the sample to nearby nuclei. This process requires the saturation of the electronic Zeeman transitions and until recently has been limited to low magnetic fields because of the lack of high-frequency, high-power microwave sources. However, recent developments in the design of gyrotrons have made DNP spectrometers operating at 1H NMR frequencies up to 800 MHz possible. The substantial enhancements (up to 300-fold) obtained with DNP make NMR studies of dilute species feasible for the first time and have already prompted new NMR applications to surfaces and materials which are porous or particulate on the micro- to nanoscale. In the future DNP-enhanced experiments will dramatically transform solid-state NMR studies of a broad range of technologically useful materials with applications in gas storage and sequestration, drug delivery, heterogeneous catalysis, and tissue engineering.
Posted on Wednesday 14th October 2015