期刊
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
卷 8, 期 13, 页码 3008-3014出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpclett.7b00987
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资金
- NSF [CHE-1363008, CHE-1416268]
- ACS-Petroleum Research Fund [55835-ND6]
- NIH [1R21EB018014, U01 CA202229, 1R21EB020323, P41 EB015897]
- DOD CDMRP [W81XWH-15-1-0271, W81XWH-12-1-0159/BC112431]
- ExxonMobil Knowledge Build
- Direct For Mathematical & Physical Scien
- Division Of Chemistry [1363008, 1416268] Funding Source: National Science Foundation
Parahydrogen is an inexpensive and readily available source of hyperpolarization used to enhance magnetic resonance signals by up to four orders of magnitude above thermal signals obtained at similar to 10 T. A significant challenge for applications is fast signal decay after hyperpolarization. Here we use parahydrogen-based polarization transfer catalysis at microtesla fields (first introduced as SABRE SHEATH) to hyperpolarize C-13(2) spin pairs and find decay time constants of 12 s for magnetization at 0.3 mT, which are extended to 2 min at that same field, when long-lived singlet states are hyperpolarized instead. Enhancements over thermal at 8.5 T are between 30 and 170 fold (0.02 to 0.12% polarization). We control the spin dynamics of polarization transfer by choice of microtesla field, allowing for deliberate hyperpolarization of either magnetization or long-lived singlet states. Density functional theory calculations and experimental evidence identify two energetically close mechanisms for polarization transfer: First, a model that involves direct 'binding of the C-13(2) pair to the polarization transfer catalyst and, second, a model transferring polarization through auxiliary protons in substrates.
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