Dynamic Nuclear Polarization Enhanced Natural Abundance ¹⁷O Spectroscopy

Abstract

We show that natural abundance oxygen-17 NMR of solids could be obtained in minutes at a moderate magnetic field strength by using dynamic nuclear polarization (DNP). Electron spin polarization could be transferred either directly to ¹⁷O spins or indirectly via ¹H spins in inorganic oxides and hydroxides using an oxygen-free solution containing a biradical polarization agent (bTbK). The results open up a powerful method for rapidly acquiring high signal-to-noise ratio solid-state NMR spectra of ¹⁷O nuclear spins and to probe sites on or near the surface, without the need for isotope labeling