Chakrabrty Tanmoy, Goldin Nir, Feintuch Akiva, Houben Lothar, and Leskes Michal. “Paramagnetic Metal Ion Dopants as Polarization Agents for DNP NMR Spectroscopy in Inorganic Solids.” ChemPhysChem 0, no. ja (May 17, 2018).
Dynamic nuclear polarization (DNP), a technique in which the high electron spin polarization is transferred to surrounding nuclei via microwaves irradiation, equips solid state NMR spectroscopy with unprecedented sensitivity. The most commonly used polarization agents for DNP are nitroxide radicals. However, their applicability to inorganic materials is mostly limited to surface detection. Paramagnetic metal ions were recently introduced as alternatives for nitroxides. Doping inorganic solids with paramagnetic ions can be used to tune material properties and introduces endogenous DNP agents that can potentially provide sensitivity in the particles\’ bulk and surface. Here we demonstrate the approach by doping Li4Ti5O12 (LTO), an anode material for lithium ion batteries, with paramagnetic ions. By incorporating Gd(III) and Mn(II) in LTO we gain up to 14 fold increase in signal intensity in static 7Li DNP?NMR experiments. These results suggest that doping with paramagnetic ions provides an efficient route for sensitivity enhancement in the bulk of micron size particles.