Fast-field-cycling relaxometry enhanced by Dynamic Nuclear Polarization

Abstract

Fast-field-cycling (FFC) NMR relaxometry experiments enhanced by in-situ Dynamic Nuclear Polarization (DNP) were performed for 1H and 13C nuclear spins with a setup based on a commercial electronically switching FFC relaxometer and a recently-built Alderman–Grant type microwave resonator for 2GHz. DNP-enhanced 1H relaxation dispersion profiles were compared to reference measurements and literature data in order to prove the reliability of DNP-enhanced relaxometry data. The method was then used to investigate the paramagnetic nuclear spin relaxation of 13C in a benzene-13C6,D6 solution of nitroxide radicals. Dispersion profiles of good quality were obtained within 2h of measurement time from a comparatively small sample of 60μl. As a prospect for future applications, DNP experiments with a high-molecular weight Poly(butadiene-1,4) melt and BDPA radical were carried out at 2GHz and 9.7GHz microwave frequency, showing solid effect DNP enhancements. In-situ hyperpolarization by DNP may provide extended possibilities for FFC relaxometry, e.g. by allowing enhanced detection of dilute or insensitive nuclear spins, additional selectivity or faster measurements of small samples.