Secrets of DNP-Juice

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Dynamic Nuclear Polarisation (DNP) can help to overcome the intrinsically low sensitivity of NMR spectroscopy. This technique involves the saturation of the electron spin transitions of a free radical by microwave irradiation which eventually leads to hyperpolarization of nearby protons. Here we focus on nitroxide radicals such as TEMPOL. We performed DNP experiments at different temperatures between 1.2 and 4 K in a 6.7 T magnetic field. Understanding the details of nitroxide based DNP processes is essential to optimize experimental protocols. By fitting the dependence of the experimentally observed proton NMR profile on the microwave frequency to the formalism developed by Abragam and Goldman for thermal mixing DNP, we find that the agreement between experimental data and theoretical predictions can be improved by taking into account the anisotropy of the electron spin longitudinal relaxation T1e and the hyperfine interactions with the surrounding protons. Combining DNP studies with EPR relaxation time measurements and data on local radical coordination, we can shed light on the heterogeneity of the sample on a nanoscopic scale.

 

UPMC - room 22-23-401

Mardi 12 Septembre 2017 12:30
Dr. WEBER Emmanuelle
Séminaire Thématique
Unité de rattachement: 
UMR 7203
Equipe de rattachement 7203: 
Equipe 3