Dynamic
nuclear polarization using photoexcited triplet electrons
(Triplet-DNP) is a method to significantly enhance nuclear spin polarization
even in a low magnetic field and at room temperature. Pentacene has
been practically used as an efficient polarizing agent for Triplet-DNP.
In this study, we demonstrate room temperature 1H and 13C hyperpolarization of eutectic mixtures of deuterated benzoic
acid doped with pentacene and a target molecule such as salicylic
acid, nicotinic acid, or 2-naphthoic acid. These molecules are otherwise
difficult to hyperpolarize by Triplet-DNP due to the low pentacene
dopabilities of these molecules. The highest 1H polarization
of 1.2% has been obtained for the eutectic mixture of salicylic acid
in 0.39 T. The present sample preparation is a crucial method to widen
the range of applications of Triplet-DNP to chemical and biomedical
analyses.