Solid state NMR

CP dynamics including Inversion Recovery Cross Polarization (IRCP) is an invaluable tool of investigation for the detailed study of local dynamics (Chem. Mater. 1996, 8, 1415-1428) including unexpected molecular reorientation « at the Magic Angle » in some silsesquioxanes (J. Chem. Soc. Dalton Trans. 1997, 1617-1626; J. Am. Chem. Soc. 1998, 120, 8380-8391) and distance measurements in multiple-spin systems (Solid State NMR 2005, 28, 50-56). Halogen NMR such as ³⁵Cl at various (high) magnetic fields is a useful spectroscopic probe for OH…Cl hydrogen bond in static and (moderate) MAS modes (Solid State NMR 2003, 23, 14-27). 

Solid state NMR methodology is developed in the framework of J-derived techniques under fast MAS in connection with the first principles calculations of J couplings by GIPAW (Inorg. Chem. 2007, 46, 1379‑1387; Accounts Chem. Res. 2007, 40, 738-746), exotic non sensitive nuclei such as ⁴³Ca and ⁸⁷Sr (J. Am. Chem. Soc. 2009, 131, 13430-13440; J. Am. Chem. Soc. 2012, 134, 12611-12628), ultra-broad spectra (Chemistry Select 2016, 4509-4519) and ultra-high magnetic field: 35.1 T, 1.5 GHz (Chem. Commun. 2018, 69, 9591-9594). To the best of our knowledge, the experiments presented in Chem. Commun. 2018, 69, 9591-9594 show the highest resolution in ⁴³Ca solid state NMR ever obtained.

Since 2017, my colleague D. Laurencin (Montpellier, France) and her collaborators develop an extremely ingenious way of ¹⁷O labeling using mechanochemistry (Angew. Chem. 2017, 55, 6803-6807). This led to the characterization of broad families of oxides by various ¹⁷O solid state NMR techniques (Inorg. Chem. 2020, 59, 13050-13066). Most importantly, and thanks to high ¹⁷O labeling, the first direct insight into the local environment and dynamics of water molecules in the whewellite mineral phase, CaC₂O₄.H₂O was achieved (J. Phys. Chem. C 2022, 126, 12044-12059). This mineral phase is of particular importance in the field of pathological calcifications – or kidney stones, see below. Oxalate binding modes in materials were fully characterized (Inorg. Chem. 2024, 63, 10179-10193).

For a mini-review on this topic, see Faraday Discussions 2023, 241, 250-265.

DNP (Dynamic Nuclear Polarization)

DNP has revolutionalized the description of carbonated hydroxyapatite (Analytical Chem. 2017, 89, 10201-10207). In this case, ¹H-¹H spin diffusion is quasi one-dimensional along the OH^– columns (parallel to the c-axis). Local order and clustering of the carbonate anions were clearly demonstrated by ¹³C-¹³C homonuclear correlation MAS DNP experiments. The clusters of carbonates are located in zig-zag chains along the c-axis of the structure. The DNP enhancement is sufficient to implement ¹H-⁴³Ca HETCOR experiments in natural abundance which is an extraordinary challenge for this particular nucleus (0.14% and low gamma) (Nature Commun. 2017, 8, 14104).

Instrumentation

Sensitivity remains the main drawback of NMR. Following Sakellariou et al., MACS (Magic Angle Coil Spinning) is a perfect alternative for samples characterized by a low mass (such as biological samples). The solenoid geometry for the micro-coil is among the most versatile ones, and is suitable for microfabrication (PLOS ONE 2012, 7, e42848) reaching an enhancement of 5-10. Recently, monolithic MACS microresonators were developed for high resolution NMR keeping intact the intrinsic cylindrical symmetry of the set-up and allowing for fast MAS (J. Magn .Reson. 2016, 271, 46-51).

Signal processing

Major improvement has been obtained in the denoising of time-domain signal by using Singular Value Decomposition (SVD) accelarated by Graphics Processing Units (GPU) (Solid State NMR 2014, 61-62, 28-34; J. Magn .Reson. 2016, 271, 46-51). SVD limits have been deeply investigated (Appl. Spectr. Rev. 2019, 54, 602-630). A 100 gain in time was achieved by combining divide and conquer algorithm, Intel Math Kernel Library (MKL), SSE3 (Streaming SIMD Extensions) hardware instructions and single precision. In such case, the CPU can outperform the GPU driven by CUDA technology (Appl. Spectr. Rev. 2020, 55, 173-196).

First principles calculations of NMR parameters, NMR crystallography

Following the pionneering work of Pickard and Mauri (2001), first principles calculations of NMR parameters were systematically implemented in the case of inorganic (Magn. Res .Chem. 2004, 42, 445-452; J. Am. Chem. Soc. 2010, 132, 4653-4668; J. Am. Chem. Soc. 2012, 134, 12611-12628) and organic solids (J. Phys. Chem. A 2005, 109, 6960-6969), biocompatible materials (App. Magn. Res. 2007, 32, 435-457; CrystEngComm 2013, 15, 8840-8847; Acta Biomater. 2016, 31, 348-357), molecular dynamics (Phys. Chem. Chem. Phys. 2009, 11, 6953-6961) and non-crystalline solids (J. Am. Chem. Soc. 2012, 134, 12611-12628; Chem. Commun. 2018, 54, 9591-9594). Carbonate substituted hydroxyapatite derived structures were characterized by extensive modeling and GIPAW calculations of NMR parameters (Chemistry Methods 2023, 3, e202300007). A combination of DFT and GIPAW calculations, Molecular Dynamics (MD), low temperature NMR and DNP experiments has been proposed for ultimate characterization of octacalcium phospate – including local water dynamics (Faraday Discussions 2025, 255, 451-482).

For review articles see: Chem. Reviews 2012, 112, 5733-5779 (631 citations in April 2026) and Chapter 17 – Disorder in Inorganic Materials, in Modern NMR Crystallography: Concepts and Applications RSC, 2025.

Advanced NMR applications in materials science

We focus here on our latest interest in soft-chemistry applied to the systhesis of amorphous calcium ortho/pyrophosphate biomaterials of tunable composition (Acta Biomater. 2020, 103, 333-345) and more generally to advanced NMR methods applied to the characterization of biocompatible materials (Solid State NMR, 2020, 107:101663). A particular focus was put: on alpha-canaphite (CrystEngComm. 2020, 22, 3130-3143); hybrid derivatives of octacalcium phosphates (Mag. Res. Chem. 2021, 940-950); pyrophosphate stabilized amorphous calcium carbonate derived materials for bone substitution (CrystEngComm. 2022, 24, 8011-8026); amorphous calcium pyrophosphate bone cements without any crystallization – in vitro biological studies (J. Mater. Chem. B 2026, DOI: 10.1039 d5tb02873f); th extreme diversity of calcium oxalate structure (Acta Cryst A – Foundations and advances 2023, C390); metabolic acids in shaping bone-like apatitic structures (Chem. Mater. 2026, DOI: 10.1021/acs.chemmater.5c02593). Collaborations with Pr C. Combes (Toulouse), M. Duer (Cambridge).

The latest methodological developments in NMR (ultra-high magnetic field up to 35.2 T, ¹⁷O isotopic labeling, high resolution multinuclear experiments, DFT modeling, GIPAW calculations) were applied to extract extremely fine information on MOFs materials, in strong collaboration with Pr Y. Huang – Western Ontario (J. Am. Chem. Soc. 2020, 142, 14877-14889; Magn. Res. Chem. 2021, 940-950; Chem. Mater. 2023, 35, 3555-3569).

Precipitation in confined media

We focus here on the specific precipitation of calcium oxalates in micro-fluidic environments and NMR (DNP) characterization of pathologial calcifications (or kidney stones). Calcium oxalates are the most prominent mineral phases found in human kidney stones. We proposed first a biomimetic prototype involving laminar microfluidics regime to characterize calcium oxalates precipitation (Lab on a Chip 2016, 16, 1157-1160). The impact of the presence/absence of polyphenols in relation with nephrolithiasis was investigated as well (Crystal Growth & Design 2020, 20, 7683-7693). Most importantly, we have used a carbonated apatite-coated microfluidic channel in order to better understand the role of the Randall’s plaque in kidney stone formation (Lab on a Chip 2024, 24, 2017-2024). A complete NMR methodology applied to studies of the hybrid (organic-inorganic) character of kidney stones is fully described in: Magn. Resonance, 2021, 2, 653-671. Collaborations with Pr A. Abou Hassan (Sorbonne University), Dr M. Daudon, Pr E. Letavernier (hôpital Tenon, Paris).

Quantum mechanics and Path-Sum, Ultra-fast numerical methods

In very strong collaboration with P.-L. Giscard (Calais, France), we have applied the Path-Sum concept to NMR for the first time solving analytically the Bloch-Siegert effect at all order (avoiding perturbative treatments), spin diffusion in an organometallic molecule exhibiting 42 protons and giving entirely new insight in Coherent Destruction of Tuneling, CDT (ENC 2019, Asilomar, USA; Phys. Rev. Res. 2020, 2, 023081). Path-Sum relies on graph theory and more specifically on resummation techniques of walks on graphs. We solved the Bloch equations in their most general form by combining for the first time Path-Sum, ★-product and ★-algebra concepts and divided-difference exponentials (collaboration with F. Neto and M. Warnock). The solution relies on a finite number of fully explicit standard operations. We have also demonstrated that bi-tri… frame transformations in physical systems leads to a dramatic increase in accuracy for numerical approaches (arXiv:2510.04598 2025). In a very strong collaboration with S. Pozza (Prague, CR), our goal is to provide ultra-fast codes for differential equations implied in Optimal Control in NMR and MRI (arXiv:2311.0414 2023).