Dynamic nuclear polarization of organic compound doped with free radicals

For those organic compounds which lack free radicals, a doping approach named melting-liquid-nitrogen-quench was developed in order to perform dynamic nuclear polarization(DNP)-nuclear magnetic resonance experiments. By using this method, the H-1, C-13, N-15 DNP enhancements were observed with free-radical-doped dibenzofuran and benzamide. The enhancement mechanism and relation between the concentration of unpaired electrons and the maximum DNP enhancement are discussed.