Substituted Fullerenes for Enhanced Optical Nuclear Hyperpolarization in Random Orientations.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41345101.
- Also identified by DOI 10.1038/s41467-025-66211-y and PMC identifier 12678411.
- Licence recorded as CC BY-NC-ND.
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Abstract
Polarized electron spins in photoexcited triplet states enable dynamic nuclear polarization (DNP) to enhance magnetic resonance imaging (MRI) sensitivity. For a practical nuclear polarization of 10%, single crystals must be precisely oriented in a magnetic field to generate narrow electron spin resonance lines, which is not appropriate for actual medical applications. Here, substituted fullerenes as triplet polarizing agents enable <sup>1</sup>H polarizations above 10%, even for random molecular orientations. While they have not been used as polarizing agents for triplet-DNP because of electron spin relaxation via pseudo-rotation, we overcome this by chemical modification of two sites on C<sub>60</sub> fullerenes. Symmetry considerations reveal fullerenes that avoided pseudo-rotations. Di-substituted fullerenes are ideal polarizing agents with sharp linewidths and long relaxation times that enabled 14.2% <sup>1</sup>H polarization in randomly oriented orientations. Optimized polarizing agents represent a promising approach for ultra-sensitive MRI medical diagnostics without the need for DNP under cryogenic temperatures and severe orientation control.