Dynamic Nuclear Polarization Surface Enhanced NMR Spectroscopy(DNP SENS) for the Characterization of Highly Reactive Surface Species

Dynamic Nuclear Polarization Surface Enhanced NMR Spectroscopy(DNP SENS)  for the Characterization of Highly Reactive Surface Species

High-Field Dynamic Nuclear Polarization (DNP)-enhanced NMR spectroscopy is currently emerging as a method of choice to increase the NMR signal of solid samples at low temperature and to overcome a key issue, the intrinsic low sensitivity of this spectroscopy. This method, which was initially developed for biological samples, consists of transferring the large polarization of unpaired electrons to nearby nuclear spins by saturating the EPR spectrum of the electrons with microwave irradiation. The electron source is typically a monoradical or biradical species such as TEMPO or TOTAPOL that is added to the sample of interest. Signal enhancement factors (ε) of up to ~400 (corresponding to a decrease of 160 000 in the experimental time!) have been reported. One very exciting application of DNP NMR is to the structural characterization of surface species in materials science. While NMR is commonly regarded as the gold standard to access local information in terms of structure and dynamics of complex materials, the low intrinsic density of surface entities makes NMR extremely difficult with standard approaches, even when dealing with highly porous materials and/or with isotopic labeling. The application of state-of-the-art high-field Dynamic Nuclear Polarization Surface Enhanced NMR spectroscopy (DNP SENS) technology is an emerging technique that allows access to high-sensitivity NMR spectra from surfaces.

Collaborators

  • Lyndon Emsley, Full Professor, EPFL, Switzerland

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