High resolution solid-state NMR on the desktop

Ke Xu; Fettah Aldudak; Oliver Pecher; Marco Braun; Andreas Neuberger; Holger Foysi; Jörn Schmedt Auf der Günne

doi:10.1016/j.ssnmr.2023.101884

High resolution solid-state NMR on the desktop

Solid State Nucl Magn Reson. 2023 Aug:126:101884. doi: 10.1016/j.ssnmr.2023.101884. Epub 2023 Jul 3.

Authors

Ke Xu¹, Fettah Aldudak², Oliver Pecher³, Marco Braun³, Andreas Neuberger¹, Holger Foysi², Jörn Schmedt Auf der Günne⁴

Affiliations

¹ University of Siegen, Faculty IV: School of Science and Technology, Department of Chemistry and Biology, Inorganic Materials Chemistry, Adolf-Reichwein-Str. 2, 57076, Siegen, Germany.
² University of Siegen, Faculty IV: School of Science and Technology, Department of Mechanical Engineering, Institute of Fluid and Thermodynamics, Paul-Bonatz-Str. 9-11, 57078, Siegen, Germany.
³ NMR Service GmbH, Blumenstr. 70 Haus 3, 99092, Erfurt, Germany.
⁴ University of Siegen, Faculty IV: School of Science and Technology, Department of Chemistry and Biology, Inorganic Materials Chemistry, Adolf-Reichwein-Str. 2, 57076, Siegen, Germany. Electronic address: gunnej@chemie.uni-siegen.de.

PMID: 37419044
DOI: 10.1016/j.ssnmr.2023.101884

Abstract

High-resolution low-field nuclear magnetic resonance (NMR) spectroscopy has found wide application for characterization of liquid compounds because of the low maintenance cost of modern permanent magnets. Solid-state NMR so far is limited to low-resolution measurements of static powders, because of the limited space available in this type of magnet. Magic-angle sample spinning and low-magnetic fields are an attractive combination to achieve high spectral resolution especially for paramagnetic solids. Here we show that magic angle spinning modules can be miniaturized using 3D printing techniques so that high-resolution solid-state NMR in permanent magnets becomes possible. The suggested conical rotor design was developed using finite element calculations and provides sample spinning frequencies higher than 20 kHz. The setup was tested on various diamagnetic and paramagnetic compounds including paramagnetic battery materials. The only comparable experiments in low-cost magnets known so far, had been done in the early times of magic angle spinning using electromagnets at much lower sample spinning frequency. Our results demonstrate that high-resolution low-field magic-angle-spinning NMR does not require expensive superconducting magnets and that high-resolution solid-state NMR spectra of paramagnetic compounds are feasible. Generally, this could introduce low-field solid-state NMR for abundant nuclei standard as a routine analytical tool.

Keywords: 3D printing; Magic-angle-spinning; NMR; Solid-state.