H-1 Hyperpolarization of Solutions by Overhauser Dynamic Nuclear Polarization with C-13-H-1 Polarization Transfer

Dynamic nuclear polarization (DNP) is a method that can significantly increase the sensitivity of nuclear magnetic resonance. The only effective DNP mechanism for in situ hyperpolarization in solution is Overhauser DNP, which is inefficient for H-1 at high magnetic fields. Here we demonstrate the possibility of generating significant H-1 hyperpolarization in solution at room temperature. To counter the poor direct H-1 Overhauser DNP, we implement steady-state C-13 Overhauser DNP in solutions and then transfer the C-13 hyperpolarization to H-1 via a reverse insensitive nuclei enhanced by polarization transfer scheme. We demonstrate this approach using a 400 MHz gyrotron-equipped 3.2 mm magic angle spinning DNP system to obtain H-1 DNP enhancement factors of 48, 8, and 6 for chloroform, tetrachloroethane, and phenylacetylene, respectively, at room temperature.