Department of Chemistry, University of Southampton , Southampton SO17 1BJ, United Kingdom.
J Am Chem Soc. 2013 Apr 3;135(13):5084-8. doi: 10.1021/ja312333v. Epub 2013 Mar 25.
The strong enhancement of NMR signals achieved by hyperpolarization decays, at best, with a time constant of a few minutes. Here, we show that a combination of long-lived singlet states, molecular design, magnetic field cycling, and specific radiofrequency pulse sequences allows repeated observation of the same batch of polarized nuclei over a period of 30 min and more. We report a recycling protocol in which the enhanced nuclear polarization achieved by dissolution-DNP is observed with full intensity and then returned to singlet order. MRI experiments may be run on a portion of the available spin polarization, while the remaining is preserved and made available for a later use. An analogy is drawn with a "spin bank" or "resealable container" in which highly polarized spin order may be deposited and retrieved.
通过极化衰变实现的 NMR 信号的强增强，其最佳时间常数仅为数分钟。在这里，我们展示了长寿命单重态、分子设计、磁场循环和特定射频脉冲序列的组合，可以在 30 分钟或更长时间内重复观察同一批极化核。我们报告了一种回收方案，其中通过溶解-DNP 实现的增强核极化以全强度观察，然后返回单重态顺序。可以在可用自旋极化的一部分上运行 MRI 实验，而其余部分则被保留并可用于以后使用。这类似于“自旋库”或“可重新密封的容器”，其中可以存储和检索高度极化的自旋序。
