Recent Advances in Magic Angle Spinning‐Dynamic Nuclear Polarization Methodology

Abstract

Dynamic nuclear polarization (DNP) is a method to boost the nuclear magnetic resonance (NMR) signal and thus alleviate the main limitation of NMR spectroscopy-its low sensitivity. One particularly successful methodology is the combination of DNP with magic angle spinning (MAS). MAS-DNP enables orders of magnitude signal enhancements in solid-state NMR experiments. The success of modern MAS-DNP stems from a combination of multiple developments in hardware, polarization agents design, sample preparation, theoretical understanding, and experimental methodology. Altogether these developments have allowed numerous breakthrough applications in biology and materials science. Despite its proven successes, ongoing research aims to further optimize hardware and polarization agent chemistry. Recent advances in MAS-DNP methodology that will allow unprecedented sensitivity in novel future applications are reviewed in this manuscript. Figure 3. (a) Schematic (left) and photograph (right) of the spinning module of nitrogen drive and bearing gas/helium-cooled design. (b-c) Schematics of the closed-loop helium-based DNP systems as developed (b) at the University of Grenoble Alpes and (c) at the Osaka University. Adapted from references 53, 48, 49 respectively.

Direct and Indirect Dynamic Nuclear Polarization Transfer Observed in Mesoporous Materials Impregnated with Nonionic Surfactant Solutions of Polar Polarizing Agents

“…The principle quantum mechanics behind these polarization transfer mechanisms and the continued efforts to better understand their details have been reviewed several times, and we refer the interested reader to these reviews. 14,15,31,32 It suffices to note that it has been previously shown that CE dominates for the systems and experimental conditions of this study. 15,33 Typically, the electron polarization transfers first to nearby solvent protons, which then can spread the polarization to other protons via 1 H− 1 H spin diffusion.…”

“…To date, four polarization transfer mechanisms have been intensively discussed: solid effect (SE), cross effect (CE), thermal mixing (TM), and Overhauser effect (OE). The principle quantum mechanics behind these polarization transfer mechanisms and the continued efforts to better understand their details have been reviewed several times, and we refer the interested reader to these reviews. ,,, It suffices to note that it has been previously shown that CE dominates for the systems and experimental conditions of this study. , …”

Multiscale Investigation of Sodium‐Ion Battery Anodes: Analytical Techniques and Applications

“…For accessing less-sensitive nuclei, a polarization enhancement (DNP) could be applied. [305,306] NMR analytical investigations of LIBs and SIBs mostly follow similar methodologies. However, for the observation of the charge transfer nuclei ( 6 Li, 7 Li and 23 Na) exist differences, more between the rarely measured 6 Li versus 7 Li/ 23 Na than the most common 7 Li vs. 23 Na, e.g.…”