Dynamic Nuclear Polarization Efficiency Increased by Very Fast Magic Angle Spinning

Sachin R. Chaudhari (1) , Dorothea Wisser (1) , Arthur C. Pinon (2) , Pierrick Berruyer (1) , David Gajan (1) , Paul Tordo (3) , Olivier Ouari (3) , Christian Reiter (4) , Frank Engelke (4) , Christophe Copéret (5) , Moreno Lelli (6) , Anne Lesage (1) , Lyndon Emsley (2)

1 Solid-State NMR Methods for Materials - Méthodes de RMN à l'état solide pour les matériaux
2 ISIC - Institut des sciences et ingénierie chimiques
3 ICR - Institut de Chimie Radicalaire
4 Bruker BioSpin GmbH
5 ETH Zürich - Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich]
6 Center for Magnetic Resonance

Dynamic Nuclear Polarization has recently emerged as a tool to enhance the sensitivity of solid-state NMR experiments. However, so far high enhancements (>100) are limited to relatively low magnetic fields, and DNP at fields higher than 9.4 T significantly drops in efficiency. Here we report solid-state Overhauser effect DNP enhancements of over 100 at 18.8 T. This is achieved through the unexpected discovery that enhancements increase rapidly with increasing magic angle spinning rates. The measurements are made using 1,3-bisdiphenylene-2-phenylallyl (BDPA) dissolved in ortho-terphenyl (OTP) at 40 kHz MAS. We introduce a source-sink diffusion model for polarization transfer which is capable of explaining the experimental observations. The advantage of this approach is demonstrated on mesoporous alumina with the acquisition of well-resolved DNP surface enhanced 27Al CP spectra.

Domaines: Chimie analytique

Sachin R. Chaudhari, Dorothea Wisser, Arthur C. Pinon, Pierrick Berruyer, David Gajan, et al.. Dynamic Nuclear Polarization Efficiency Increased by Very Fast Magic Angle Spinning. Journal of the American Chemical Society, 2017, 139 (31), pp.10609-10612. ⟨10.1021/jacs.7b05194⟩. ⟨hal-01576023⟩