DNP without microwave radiation? A very interesting approach.
Liu, G., et al., Photo-induced radical polarization and liquid-state dynamic nuclear polarization with fullerene nitroxide derivatives. Phys. Chem. Chem. Phys., 2017.
We report on radical polarization and optically-driven liquid DNP with nitroxide radicals functionalized by photoexcitable fullerene derivatives. Pulse laser excitation of the fullerene moiety leads to a transient nitroxide radical polarization that is one order of magnitude larger than at Boltzmann equilibrium. Life time of radical polarization increases with size of the fullerene derivative and correlates with the electronic spin lattice relaxation time T1e. Overhauser NMR signal enhancements of toluene solvent protons were observed under steady-state illumination, which replaced microwave irradiation.