Jannin, S., et al., Low-temperature cross polarization in view of enhancing dissolution Dynamic Nuclear Polarization in NMR. Chem. Phys. Lett., 2011. 517(4–6): p. 234-236.
http://dx.doi.org/10.1016/j.cplett.2011.10.042
Dynamic Nuclear Polarization (DNP) induced by saturation of ESR transitions of TEMPO at 1.2 K and 3.35 T is characterized by build-up rates that are typically 5 times faster for protons than for the carboxylic carbon-13 in acetate. We show that cross polarization from protons to carbon-13 allows one to achieve a polarization P(13C) >20% in less than 10 min, twice as much as has been previously reported, in one-fifth of the time. This should open the way to an unprecedented improvement in the efficiency of dissolution DNP.