Elliott, Stuart J, Morgan Ceillier, Olivier Cala, Quentin Stern, Samuel F Cousin, and Sami Jannin. “Simple and Cost-Effective Cross-Polarization Experiments under Dissolution-Dynamic Nuclear Polarization Conditions with a 3D-Printed 1H-13C Background-Free Radiofrequency Coil.” Journal of Magnetic Resonance Open 10–11 (June 2022): 100033.
https://doi.org/10.1016/j.jmro.2022.100033.
The low sensitivity of conventional nuclear magnetic resonance experiments can be overcome, in suitable cases, by employing hyperpolarization methodologies. One such technique, dissolution-dynamic nuclear polarization, provides a robust means of strongly polarizing a variety of small molecules. A drawback of the dissolution-dynamic nuclear polarization approach, the excessively long polarization timescales for insensitive nuclei, has been circumvented by using cross-polarization radiofrequency pulse sequences, which in general yield quick and substantial 13C polarizations. However, the capacity to effectively perform efficient cross-polarization experiments under dissolution-dynamic nuclear polarization conditions remains challenging, and the polarization quantification can be plagued by additional complications including spurious background signals from the probe. Here we propose a background-free 1H-13C radiofrequency coil specifically designed for use in cross-polarization experiments on samples of up to 500 𝜇L in volume at liquid helium temperatures. We additionally introduce simple guidelines for the optimization and implementation of cross-polarization radiofrequency pulse sequences. Experimental demonstrations of 13C polarizations reaching ~60% are presented for the case of [1-13C]sodium acetate.