Hyperpolarization transfer pathways in inorganic materials

Snædís Björgvinsdóttir; Pinelopi Moutzouri; Brennan J Walder; Nicolas Matthey; Lyndon Emsley

doi:10.1016/j.jmr.2020.106888

Hyperpolarization transfer pathways in inorganic materials

J Magn Reson. 2021 Feb:323:106888. doi: 10.1016/j.jmr.2020.106888. Epub 2020 Dec 5.

Authors

Snædís Björgvinsdóttir¹, Pinelopi Moutzouri¹, Brennan J Walder¹, Nicolas Matthey¹, Lyndon Emsley¹

Affiliation

¹ Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.

PMID: 33359903
DOI: 10.1016/j.jmr.2020.106888

Abstract

Dynamic nuclear polarization can be used to hyperpolarize the bulk of proton-free inorganic materials in magic angle spinning NMR experiments. The hyperpolarization is generated on the surface of the material with incipient wetness impregnation and from there it is propagated towards the bulk through homonuclear spin diffusion between weakly magnetic nuclei. This method can provide significant gains in sensitivity for MAS NMR spectra of bulk inorganic compounds, but the pathways of the magnetization transfer into the material have not previously been elucidated. Here we show how two-dimensional experiments can be used to study spin diffusion from the surface of a material towards the bulk. We find that hyperpolarization can be efficiently relayed from surface sites to multiple bulk sites simultaneously, and that the bulk sites also engage in rapid polarization exchange between themselves. We also show evidence that the surface peaks can exchange polarization between different sites in cases of disorder.

Keywords: Dynamic nuclear polarization; Solid-state NMR; Spin diffusion.