Friday, July 26, 2013

DNP enhanced NMR using a high-power 94 GHz microwave source: a study of the TEMPOL radical in toluene

This paper was already published in 2010 but I just came across it recently. Please let me know if there are any papers you would like to see posted here, or that I missed. 



Kryukov, E.V., et al., DNP enhanced NMR using a high-power 94 GHz microwave source: a study of the TEMPOL radical in toluene. Phys Chem Chem Phys, 2010. 12(22): p. 5757-65.


DNP enhanced (1)H NMR at 143 MHz in toluene is investigated using an NMR spectrometer coupled with a modified EPR spectrometer operating at 94 GHz and TEMPOL as the polarisation agent. A 100 W microwave amplifier was incorporated into the output stage of the EPR instrument so that high microwave powers could be delivered to the probe in either CW or pulsed mode. The maximum enhancement for the ring protons increases from approximately -16 for a 5 mM TEMPOL solution to approximately -50 for a 20 mM solution at a microwave power of approximately 480 mW. The temperature dependence of the enhancement, the NMR relaxation rates and the ESR spectrum of TEMPOL were also studied in an effort to obtain information on the dynamics of the system.