Triplet-DNP in magnetically oriented microcrystal arrays

Akinori Kagawa; Ryosuke Kusumi; Rintarou Nagase; Yuki Morishita; Koichiro Miyanishi; Kazuyuki Takeda; Masahiro Kitagawa; Makoto Negoro

doi:10.1016/j.jmr.2023.107439

Triplet-DNP in magnetically oriented microcrystal arrays

J Magn Reson. 2023 Jun:351:107439. doi: 10.1016/j.jmr.2023.107439. Epub 2023 Apr 13.

Authors

Akinori Kagawa¹, Ryosuke Kusumi², Rintarou Nagase³, Yuki Morishita³, Koichiro Miyanishi⁴, Kazuyuki Takeda⁵, Masahiro Kitagawa⁴, Makoto Negoro⁶

Affiliations

¹ Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan; Center for Quantum Information and Quantum Biology, Osaka University, Japan. Electronic address: kagawa@ee.es.osaka-u.ac.jp.
² Department of Forest Resource Chemistry, Forestry and Forest Products Research Institute, Forest Research and Management Organization, Tsukuba 305-8687, Japan; Department of Forest Resource Chemistry, Forestry and Forest Products Research Institute, Forest Research and Management Organization, Tsukuba 305-8687, Japan. Electronic address: rkusumi@ffpri.affrc.go.jp.
³ Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
⁴ Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan; Center for Quantum Information and Quantum Biology, Osaka University, Japan.
⁵ Division of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
⁶ Center for Quantum Information and Quantum Biology, Osaka University, Japan; Institute for Quantum Life Science (iQLS), National Institutes for Quantum and Radiological Science and Technology (QST), Chiba 263-8555, Japan.

PMID: 37084519
DOI: 10.1016/j.jmr.2023.107439

Abstract

We explore dynamic nuclear polarization using electron spins in the photo-excited triplet state (Triplet-DNP) in magnetically oriented microcrystal arrays (MOMAs) of pentacene-doped p-terphenyl, in which the individual crystallites are magnetically aligned and UV-cured. In contrast to the conventional approach to Triplet-DNP in powder, which suffers from reduced nuclear polarization due to the averaged electron polarization and the broadening of electron-spin resonance, Triplet-DNP of the MOMAs offers as high dynamic polarization as that attainable in single-crystals. In the case of pentacene-doped p-terphenyl, the enhanced ¹H polarization in the one-dimensional MOMA, prepared simply by leaving the suspension in a stationary magnetic field before UV curation, can be higher than that attainable in the powder sample by an order of magnitude and comparable to that in single crystals and in the three-dimensional MOMA made using a modulational rotating field. Triplet-DNP of the MOMAs may find potential applications, such as the polarization of the co-doped target molecules and dissolution experiments.

Keywords: Dynamic nuclear polarization (DNP); Magnetically oriented microcrystal array (MOMA); Photo-excited triplet state; Triplet-DNP.