Gaining unique insights into the atomic-level structure of materials using ultra-high-field NMR and DNP

Solid-state NMR spectroscopy can provide unique insights into the atomic-level structure of defects in materials, which have a major influence on their optoelectronic and chemical properties. Nevertheless, major limitations of this technique remain its lack of resolution and sensitivity for quadrupolar nuclei with spin I ≥ 1, which represent over 74% of NMR-active isotopes [1].

 We show how recent instrumental and methodological developments open new avenues for the observation of these quadrupolar isotopes. In particular, we have leveraged the gain in resolution provided by 1.2 GHz NMR spectrometer (B₀ = 28.2 T) to obtain novel insights into the local environments of quadrupolar nuclei, such as ¹⁷O, ²⁷Al, ⁶³Cu or ⁶⁷Zn, in solids. This approach has been applied to shed light on the mechanisms operating in the mechanosynthesis of organometallic complexes. We have also developed advanced NMR experiments to improve further resolution and sensitivity for the detection of quadrupolar nuclei at 28.2 T. We have especially introduced techniques for the indirect detection via protons of spin-3/2 nuclei, such as ²³Na, ¹¹B and ³⁵Cl, under high resolution [2]. We have also explored how the signals of nearby distinct quadrupolar isotopes, such as ²⁷Al and ¹¹B, can be correlated in 2D spectra using continuous wave recoupling (see Fig. 1).

We have also leveraged the sensitivity gain provided by indirect DNP relayed by protons to detect half-integer quadrupolar nuclei near surfaces of inorganic materials with high resolution and sensitivity [3, 4]. This technique has notably been applied to observe oxygen vacancies near the surface of ZnO nanoparticles used in optoelectronics and active sites of heterogeneous catalysts for the oxidative dehydrogenation of propane.

REFERENCES:

[1] A. Nadol, et al. Chem. Sci., 2025, 16, 69. [2] J. Trébosc, et al. Solid State Nucl. Magn. Reson. 2024, 134, 101971. [3] H. Nagashima, et al. J. Phys. Chem. Lett. 2024, 15, 4858. [4] H. Nagashima, et al. J. Magn. Reson. Open 2024, 21, 100177.