Report to the 21. DMG Shortcourse "Applications of Solid State NMR Spectroscopy in the mineralogical and geoscientific research "
in Bochum from 21. May - 24. May 2024
This year, the short course "Anwendungen der Festkörper NMR Spektroskopie in der mineralogischen und geowissenschaftlichen Forschung" offered by the DMG and DGK took place again from May 21st to 24th, now for the 21st time. The course was conducted under the direction of Dr. Michael Fechtelkord at the Ruhr-University Bochum and offered participants from various disciplines the opportunity to receive an introduction to the basics of NMR spectroscopy as well as to learn about its diverse applications. In the morning of each course day, theoretical basics were discussed. This was followed by the practical part, in which samples were prepared and measurements were carried out on the device. In the afternoon, the measurements were evaluated.
On the first day, there was a theoretical introduction to NMR spectroscopy. Its strengths and weaknesses, its areas of application, the physical principles and how it works were discussed, as well as the device structure and historical development. Knowledge of 1H spin-lattice relaxation was then imparted, which was illustrated using measurements (using the Topspin program) of tetramethylammonium iodide. The dependence of the recorded spectra on the measurement temperature was also shown. The activation energies and correlation times for the signals could be determined when evaluating them on paper. The day ended with a relaxed atmosphere with food and drinks in the "Filou" pub on Buscheyplatz.
The second day dealt with the interactions of magnetic dipolar coupling and chemical shift. The Magic Angle Spinning (MAS) method was also presented, which makes it possible to remove anisotropy effects. This technique was also used to measure 29Si, 19F, and 1H spectra of synthetic phlogopite. After an introduction to the DmFit2021 program using a few exercises, namely simple Lorentz and Gaussian line shapes, integration of sidebands and the adaptation of line shapes with anisotropy of the chemical shift, the recorded MAS NMR spectra were evaluated with this software.
The third day of the short course focused on the possible applications of multipulse techniques with the Hahn echo and the basics of the cross-polarization experiment (CP). The practical part included a contact time-dependent CPMAS experiment on kaolinite, in which the atomic distances between Si and H nuclei were determined. This was done using the Excel spreadsheet program.
During the previous days, samples with a nuclear spin of I = ½ were examined, but on the last day the focus was on quadrupole nuclei (spin quantum number I > 0.5). In the theoretical part, various NMR methods such as "Double Rotation" (DOR), "Multi-Quantum Magic Angle Spinning" (MQMAS) and "Satellite Transition Spectroscopy" (SATRAS) were presented. In practice, the quadrupole coupling constants of 23Na in Glauber's salt and 27Al in corundum were investigated using MAS and SATRAS techniques and the spectra were then evaluated.
The four days of the course were certainly not enough to fully cover the entire range of NMR solid-state spectroscopy, but thanks to comprehensive explanations we were able to develop a good idea of what information the method can provide about a material and it will help us to better assess the potential application for future projects. We would therefore like to thank Dr. Michael Fechtelkord for the successful short course and the knowledge we gained.
Martina Paetsch (MPI Stuttgart) and Florian Rafalski (FAU Erlangen-Nuremberg)
