Tateishi, K., et al., Dynamic nuclear polarization with photoexcited triplet electrons in a glassy matrix. Angew Chem Int Ed Engl, 2013. 52(50): p. 13307-10.
NMR spectroscopy and MRI are powerful methods for the non-destructive analysis of microscopic structures inside bulk materials and human bodies. As a method to enhance their sensitivities, dynamic nuclear polarization (DNP) has attracted great attention. The intensity of a signal from nuclear spins is proportional to the spin polarization. In magnetic fields conventionally used for NMR spectroscopy and MRI, thermal polarization of nuclear spins at room temperature is in the order of 105 or less. DNP is a means of transferring spin polarization from electrons to nuclei. The thermal polarization of electron spins is 660 times larger than that of 1H spins, and therefore, DNP can enhance the 1H spin polarization (hence the sensitivity) by a factor of at most 660.