Kubicki, D.J. and L. Emsley, Improving Sensitivity of Solid-state NMR Spectroscopy by Rational Design of Polarizing Agents for Dynamic Nuclear Polarization. Chimia (Aarau), 2017. 71(4): p. 190-194.
We review our recent efforts to optimize the efficiency of polarizing agents for Dynamic Nuclear Polarization (DNP) in solid-state MAS NMR spectroscopy. We elucidate the links between DNP performance, molecular structure and electronic relaxation properties of dinitroxide biradicals. We show that deuteration and increased bulkiness lead to slower electronic relaxation and in turn to higher DNP enhancements. We also show that the incorporation of solid dielectric particles into the sample is a general method of amplifying DNP enhancements by about a factor of two.