DNP sensitivity of F-19-NMR signals in hexafluorobenzene depending on polarizing agent type

Abstract

Low field dynamic nuclear polarization or low field magnetic double resonance technique enables enhanced nuclear magnetic resonance signals to be detected without increasing the strength of the polarizing field. The study reports that the dynamic nuclear polarization of F-19 nuclei in hexafluorobenzene solutions doped with nitroxide, BDPA, MC800 asphaltene and MC30 asphaltene free radicals at 15 G. The F-19 nuclei in all solutions gave positive DNP enhancements changing between 3.42 and 189.54, corresponding to predominantly scalar interactions with the unpaired electrons in the radicals. DNP sensitivity of F-19 nuclei in hexafluorobenzene was observed to be changed significantly depending on the radical type. Nitroxide was found to have the best DNP performance among the polarizing agents.