Dynamic nuclear polarization and chemically induced hyperpolarization: Progress, mechanisms, and opportunities

Nuclear magnetic resonance (NMR) spectroscopy is a powerful and broadly used spectroscopic technique for characterizing molecular structures and dynamics. Yet the power of NMR is restricted by its inherently low sensitivity due to the weak polarization of nuclear spins under conventional experiment conditions. Dynamic nuclear polarization (DNP) and chemically induced dynamic nuclear polarization (CIDNP) have been emerging as powerful in-situ hyperpolarization methods to boost NMR sensitivity. This review provides a brief overview of DNP mechanisms in the context of both solid-state and liquid-state. We delve into the molecular features of different polarizing agents and their impacts on DNP applications, which are now steadily progressing towards modern NMR magnetic field strengths and ambient temperatures. Furthermore, the progress of CIDNP, particularly photo-CIDNP as a potential alternative hyperpolarization technique of DNP, in studying protein dynamics and chemical reaction mechanisms, will be covered. This review also highlights the chemical diversity and experimental strategies crucial for these hyperpolarization techniques, showcasing their transformative role in NMR spectroscopy.