High-Resolution 17O Solid-State NMR as a Unique Probe for Investigating Oxalate Binding Modes in Materials: The Case Study of Calcium Oxalate Biominerals

Oxalate ligands are found in many classes of materials, including energy storage materials and biominerals. Determining their local environments at the atomic scale is thus paramount to establishing the structure and properties of numerous phases. Here, we show that high-resolution 17O solid-state NMR is a valuable asset for investigating the structure of crystalline oxalate systems. First, an efficient 17O-enrichment procedure of oxalate ligands is demonstrated using mechanochemistry. Then, 17O-enriched oxalates were used for the synthesis of the biologically relevant calcium oxalate monohydrate (COM) phase, enabling the analysis of its structure and heat-induced phase transitions by high-resolution 17O NMR. Studies of the low-temperature COM form (LT-COM), using magnetic fields from 9.4 to 35.2 T, as well as 13C-17O MQ/D-RINEPT and 17O{1H} MQ/REDOR experiments, enabled the 8 inequivalent oxygen sites of the oxalates to be resolved, and tentatively assigned. The structural changes upon heat treatment of COM were also followed by high-resolution 17O NMR, providing new insight into the structures of the high-temperature form (HT-COM) and anhydrous calcium oxalate α-phase (α-COA), including the presence of structural disorder in the latter case. Overall, this work highlights the ease associated with 17O-enrichment of oxalate oxygens, and how it enables high-resolution solid-state NMR, for "NMR crystallography" investigations.

An adult Drosophila glioma model to highlight metabolic dysfunctions and evaluate the role of the serotonin 5-HT7 receptor as a potential therapeutic target

Gliomas account for 50% of brain cancers and are therefore the most common brain tumors. Molecular alterations involved in adult gliomas have been identified and mainly affect tyrosine kinase receptors with amplification and/or mutation of the epidermal growth factor receptor (EGFR) and its associated signaling pathways. Several targeted therapies have been developed, but current treatments remain ineffective for glioblastomas, the most severe forms. Thus, it is a priority to identify new pharmacological targets. Drosophila glioma models established in larvae and adults are useful to identify new genes and signaling pathways involved in glioma progression. Here, we used a Drosophila glioma model in adults, to characterize metabolic disturbances associated with glioma and assess the consequences of 5-HT7 R expression on glioma development. First, by using in vivo magnetic resonance imaging, we have shown that expression of the constitutively active forms of EGFR and PI3K in adult glial cells induces brain enlargement. Then, we explored altered cellular metabolism by using high-resolution magic angle spinning NMR and 1 H-13 C heteronuclear single quantum coherence solution states. Discriminant metabolites identified highlight the rewiring of metabolic pathways in glioma and associated cachexia phenotypes. Finally, the expression of 5-HT7 R in this adult model attenuates phenotypes associated with glioma development. Collectively, this whole-animal approach in Drosophila allowed us to provide several rapid and robust phenotype readouts, such as enlarged brain volume and glioma-associated cachexia, as well as to determine the metabolic pathways involved in glioma genesis and finally to confirm the interest of the 5-HT7 R in the treatment of glioma.

Structural Modeling of O/F Correlated Disorder in TaOF3 and NbOF3-x(OH)x by Coupling Solid-State NMR and DFT Calculations

The structure of MOF3 (M = Nb, Ta) compounds was precisely modeled by combining powder X-ray diffraction, solid-state NMR spectroscopy, and semiempirical dispersion-corrected DFT calculations. It consists of stacked ∞(MOF3) layers along the c⃗ direction formed by heteroleptic corner-connected MX6 (X = O, F) octahedra. 19F NMR resonance assignments and occupancy rates of the anionic crystallographic sites have been revised. The bridging site is shared equally by the anions, and the terminal site is occupied by F only. An O/F correlated disorder is expected since cis-MO2F4 octahedra are favored, resulting in one-dimensional -F-M-O-M- strings along the <100> and <010> directions. Ten different 2 × 2 × 1 supercells per compound, fulfilling these characteristics, were built. Using DFT calculations and the GIPAW approach, the supercells were relaxed and the 19F isotropic chemical shift values were determined. The agreement between the experimental and calculated 19F spectra is excellent for TaOF3. The 1H and 19F experimental NMR spectra revealed that some of the bridging F atoms are substituted by OH groups, especially in NbOF3. New supercells involving OH groups were generated. Remarkably, the best agreement is obtained for the supercells with the composition closest to that estimated from the 19F NMR spectra, i.e., NbOF2.85(OH)0.15.

Operando nuclear magnetic resonance spectroscopy: Detection of the onset of metallic lithium deposition on graphite at low temperature and fast charge in a full Li-ion battery

Lithium-ion batteries are at the core of the democratisation of electric transportation and portative electronic devices. However, fast and/or low temperature charge induce performance loss, mainly through lithium plating, a degrading mechanism. In this report, 7Li operando Nuclear Magnetic Resonance spectroscopy is used to detect the onset of metastable lithium deposits in an NMC622/graphite cell at 0 °C and fast charge. An operando setup, compatible with low temperatures, was developed with special attention to the pressure applied on the electrodes/separator stack and noise reduction to enable early detection and good time-resolution. Direct detection of metallic lithium enables drawing correlations between lithium plating and electrochemical data.

Long-Term Fate and Efficacy of a Biomimetic (Sr)-Apatite-Coated Carbon Patch Used for Bone Reconstruction

Critical bone defect repair remains a major medical challenge. Developing biocompatible materials with bone-healing ability is a key field of research, and calcium-deficient apatites (CDA) are appealing bioactive candidates. We previously described a method to cover activated carbon cloths (ACC) with CDA or strontium-doped CDA coatings to generate bone patches. Our previous study in rats revealed that apposition of ACC or ACC/CDA patches on cortical bone defects accelerated bone repair in the short term. This study aimed to analyze in the medium term the reconstruction of cortical bone in the presence of ACC/CDA or ACC/10Sr-CDA patches corresponding to 6 at.% of strontium substitution. It also aimed to examine the behavior of these cloths in the medium and long term, in situ and at distance. Our results at day 26 confirm the particular efficacy of strontium-doped patches on bone reconstruction, leading to new thick bone with high bone quality as quantified by Raman microspectroscopy. At 6 months the biocompatibility and complete osteointegration of these carbon cloths and the absence of micrometric carbon debris, either out of the implantation site or within peripheral organs, was confirmed. These results demonstrate that these composite carbon patches are promising biomaterials to accelerate bone reconstruction.

Impact of Mineralizing Agents on Aluminum Distribution and Acidity of ZSM-5 Zeolites

Intensive research on improving the catalytic properties of zeolites is focused on modulating their acidity and the distribution of associated Al sites. Herein, by studying a series of ZSM-5 zeolites over a broad range of Al content, we demonstrate how the nature of the mineralizing agent (F^- or OH^- ) used in hydrothermal syntheses directly impacts Al sites distribution. The proportions of Al sites, probed by ²⁷ Al NMR, depend on the Si/Al ratio for F^- , but remain identical for OH^- (from Si/Al=30 to 760). This leads to contrasting variations in weak and strong acidities. Such opposite effect of mineralizers is explained by the spatial location of negative charges and the resulting balance between short- and long-range electrostatic interactions. This understanding paves the way for additional and simple opportunities to control zeolites' acidity.

Expression of the Human Serotonin 5-HT7 Receptor Rescues Phenotype Profile and Restores Dysregulated Biomarkers in a Drosophila melanogaster Glioma Model

Gliomas are the most common primary brain tumors in adults. Significant progress has been made in recent years in identifying the molecular alterations involved in gliomas. Among them, an amplification/overexpression of the EGFR (Epidermal Growth Factor Receptor) proto-oncogene and its associated signaling pathways have been widely described. However, current treatments remain ineffective for glioblastomas, the most severe forms. Thus, the identification of other pharmacological targets could open new therapeutic avenues. We used a glioma model in Drosophila melanogaster that results from the overexpression of constitutively active forms of EGFR and PI3K specifically in glial cells. We observed hyperproliferation of glial cells that leads to an increase in brain size and lethality at the third instar larval stage. After expression of the human serotonin 5-HT7 receptor in this glioma model, we observed a decrease in larval lethality associated with the presence of surviving adults and a return to a normal morphology of brain for some Drosophila. Those phenotypic changes are accompanied by the normalization of certain metabolic biomarkers measured by High-Resolution Magic Angle Spinning NMR (HR-MAS NMR). The 5-HT7R expression in glioma also restores some epigenetic modifications and characteristic markers of the signaling pathways associated with tumor growth. This study demonstrates the role of the serotonin 5-HT7 receptor as a tumor suppressor gene which is in agreement with transcriptomic analysis obtained on human glioblastomas.

In vivo effectiveness of carbonated calcium-deficient hydroxyapatite-coated activated carbon fiber cloth on bone regeneration

We have previously shown that activated carbon fiber cloth (ACC) either uncoated or coated with carbonated calcium-deficient hydroxyapatite (CDA), namely ACC and ACC/CDA, were biocompatible in vitro with human osteoblasts. Here we hypothesized that ACC and ACC/CDA could be used as tissue patches in vivo to accelerate wounded bone healing. In a model of rat femoral defect, we have compared spontaneous cortical bone regeneration with regeneration in the presence of ACC and ACC/CDA patches. At Day 7, 14, and 21, bone formation was evaluated using microcomputed tomography, magnetic resonance imaging, and histological analysis. Our results demonstrate first that these ACC tissues are highly biocompatible in vivo, and second that ACC/CDA patches apposition results in the acceleration of bone reconstruction due to a guiding action of the ACC fibers and an osteogenic effect of the CDA phase. We guess that this approach may represent a valuable strategy to accelerate bone regeneration in human.

Probing 29Si-17O connectivities and proximities by solid-state NMR

The measurement of dipolar and J- couplings between ²⁹Si and ¹⁷O isotopes is challenging owing to (i) the low abundance of both isotopes and (ii) their close Larmor frequencies, which only differ by 19%. These issues are circumvented here by the use of isotopic enrichment and dedicated triple-resonance magic-angle spinning NMR probe. The surface of ²⁹Si-enriched silica was labelled with ¹⁷O isotope and heated at 80 and 200 °C. ²⁹Si-¹⁷O connectivities and proximities were probed using two-dimensional (2D) through-bond and through-space heteronuclear multiple-quantum coherences (J- and D-HMQC) experiments between ¹⁷O and ²⁹Si nuclei. The simulation of the build-up of the J- and D-HMQC signals allowed the first experimental measurement of J- and dipolar coupling constants between ¹⁷O and ²⁹Si nuclei. These HMQC experiments allow distinguishing two distinct siloxane (SiOSi) oxygen sites: (i) those covalently bonded to Q³ and Q⁴ groups, having a hydroxyl group as a second neighbour and (ii) those covalently bonded to two Q⁴ groups. The measured J- and dipolar coupling constants of siloxane ¹⁷O nucleus with Q^{4 29}Si nuclei differ from those with Q^{3 29}Si nuclei. These results indicate that the ²⁹Si-¹⁷O one-bond J-coupling and Si-O bond length depend on the second neighbours of the Si atoms.

Complementary Nuclear Magnetic Resonance-Based Metabolomics Approaches for Glioma Biomarker Identification in a Drosophila melanogaster Model

Human malignant gliomas are the most common type of primary brain tumor. Composed of glial cells and their precursors, they are aggressive and highly invasive, leading to a poor prognosis. Due to the difficulty of surgically removing tumors and their resistance to treatments, novel therapeutic approaches are needed to improve patient life expectancy and comfort. Drosophila melanogaster is a compelling genetic model to better understanding human neurological diseases owing to its high conservation in signaling pathways and cellular content of the brain. Here, glioma has been induced in Drosophila by co-activating the epidermal growth factor receptor and the phosphatidyl-inositol-3 kinase signaling pathways. Complementary nuclear magnetic resonance (NMR) techniques were used to obtain metabolic profiles in the third instar larvae brains. Fresh organs were directly studied by ¹H high resolution-magic angle spinning (HR-MAS) NMR, and brain extracts were analyzed by solution-state ¹H-NMR. Statistical analyses revealed differential metabolic signatures, impacted metabolic pathways, and glioma biomarkers. Each method was efficient to determine biomarkers. The highlighted metabolites including glucose, myo-inositol, sarcosine, glycine, alanine, and pyruvate for solution-state NMR and proline, myo-inositol, acetate, and glucose for HR-MAS show very good performances in discriminating samples according to their nature with data mining based on receiver operating characteristic curves. Combining results allows for a more complete view of induced disturbances and opens the possibility of deciphering the biochemical mechanisms of these tumors. The identified biomarkers provide a means to rebalance specific pathways through targeted metabolic therapy and to study the effects of pharmacological treatments using Drosophila as a model organism.

Dual Electroactivity in a Covalent Organic Network with Mechanically Interlocked Pillar[5]arenes

The synthesis and characterization of a polyrotaxanated covalent organic network (CON) based on the association between the viologen and pillar[5]arene (P[5]OH) units are reported. The mechanical bond allows for the irreversible insertion of n-type redox centers (P[5]OH macrocycles) within a pristine structure based on p-type viologen redox centers. Both redox units are active on a narrow potential range and, in water, the presence of P[5]OH greatly increases the electroactivity of the material.

Iterative baseline correction algorithm for dead time truncated one-dimensional solid-state MAS NMR spectra

We present an algorithm suitable for automatically correcting rolling baseline coming from time-domain truncation induced by the dead time in pulse-acquire one-dimensional MAS NMR spectra. It relies on an iterative estimation of the baseline restricted in the time-domain by the dead time duration combined with a histogram filter allowing adaptive selection of the baseline points. This method does not make any assumption regarding the NMR resonances line shapes or widths and does not modify the acquired free induction decay points. This makes it suitable for accurate deconvolution and quantification of single-pulse MAS NMR spectra. The baseline correction accuracy is evaluated on synthetic solid-state spectra of ¹⁹F, ⁷¹Ga, and ²³Na by comparing the fitted baseline to the theoretical one. The versatility of the algorithm is also exemplified on three additional solid-state spectra of ²³Na and ⁷¹Ga. The algorithm is made available to the community through a user-friendly standalone Matlab® application.

Magic-angle-spinning-induced local ordering in polymer electrolytes and its effects on solid-state diffusion and relaxation NMR measurements

Magic-angle-spinning (MAS) enhances sensitivity and resolution in solid-state nuclear magnetic resonance (NMR) measurements. MAS is obtained by aerodynamic levitation and drive of a rotor, which results in large centrifugal forces that may affect the physical state of soft materials, such as polymers, and subsequent solid-state NMR measurements. Here, we investigate the effects of MAS on the solid-state NMR measurements of a polymer electrolyte for lithium-ion battery applications, poly(ethylene oxide) (PEO) doped with the lithium salt LiTFSI. We show that MAS induces local chain ordering, which manifests itself as characteristic lineshapes with doublet-like splittings in subsequent solid-state ¹ H, ⁷ Li, and ¹⁹ F static NMR spectra characterizing the PEO chains and solvated ions. MAS results in distributions of stresses and hence local chain orientations within the rotor, yielding distributions in the local magnetic susceptibility tensor that give rise to the observed NMR anisotropy and lineshapes. The effects of MAS were investigated on solid-state ⁷ Li and ¹⁹ F pulsed-field-gradient (PFG) diffusion and ⁷ Li longitudinal relaxation NMR measurements. Activation energies for ion diffusion were affected modestly by MAS. ⁷ Li longitudinal relaxation rates, which are sensitive to lithium-ion dynamics in the nanosecond regime, were essentially unchanged by MAS. We recommend that NMR researchers studying soft polymeric materials use only the spin rates necessary to achieve the desired enhancements in sensitivity and resolution, as well as acquire static NMR spectra after MAS experiments to reveal any signs of stress-induced local ordering.

Atomic Insights into Aluminium-Ion Insertion in Defective Anatase for Batteries

Aluminium batteries constitute a safe and sustainable high-energy-density electrochemical energy-storage solution. Viable Al-ion batteries require suitable electrode materials that can readily intercalate high-charge Al³⁺ ions. Here, we investigate the Al³⁺ intercalation chemistry of anatase TiO₂ and how chemical modifications influence the accommodation of Al³⁺ ions. We use fluoride- and hydroxide-doping to generate high concentrations of titanium vacancies. The coexistence of these hetero-anions and titanium vacancies leads to a complex insertion mechanism, attributed to three distinct types of host sites: native interstitial sites, single vacancy sites, and paired vacancy sites. We demonstrate that Al³⁺ induces a strong local distortion within the modified TiO₂ structure, which affects the insertion properties of the neighbouring host sites. Overall, specific structural features induced by the intercalation of highly polarising Al³⁺ ions should be considered when designing new electrode materials for polyvalent batteries.

Strontium incorporation into biomimetic carbonated calcium-deficient hydroxyapatite coated carbon cloth: Biocompatibility with human primary osteoblasts

It has already been shown that sono-electrodeposition can be used to coat activated carbon fiber cloth (ACC) with calcium phosphates (CaP) and we recently demonstrated that cathodic polarization at -1 V/Hg/Hg₂SO₄ was the best parameter to obtain a carbonated calcium deficient hydroxyapatite (CDA) coating with optimal uniformity and homogeneity. In the present study, we investigated whether this technique was suitable to dope this carbonated CDA coating by partial substitution with another bivalent cation such as strontium. We show here that a strontium-substituted carbonated CDA coating can be produced and quantitatively controlled up to at least 10 at.%. In this range we demonstrate that the presence of strontium does not modify either the textural or the structural properties of the carbonated CDA. Owing to the well-known effect of both carbonated CDA and strontium in bone formation, the biocompatibility of ACC coated or not with carbonated CDA or with strontium substituted carbonated CDA was tested using primary human osteoblasts. Our data revealed a positive and dose-dependent effect of strontium addition on osteoblast activity and proliferation. In conclusion, we show here that electrodeposition at -1 V is a suitable and easy process to incorporate cations of biological interest into CaP coating.

Spatially-resolved metabolic profiling of living Drosophila in neurodegenerative conditions using 1H magic angle spinning NMR

Drosophila flies are versatile animal models for the study of gene mutations in neuronal pathologies. Their small size allows performing in vivo Magic Angle Spinning (MAS) experiments to obtain high-resolution 1H nuclear magnetic resonance (NMR) spectra. Here, we use spatially-resolved 1H high-resolution MAS NMR to investigate in vivo metabolite contents in different segments of the fly body. A comparative study of metabolic changes was performed for three neurodegenerative disorders: two cell-specific neuronal and glial models of Huntington disease (HD) and a model of glutamate excitotoxicity. It is shown that these pathologies are characterized by specific and sometimes anatomically localized variations in metabolite concentrations. In two cases, the modifications of 1H MAS NMR spectra localized in fly heads were significant enough to allow the creation of a predictive model.

X-ray Diffraction, NMR Studies, and DFT Calculations of the Room and High Temperature Structures of Rubidium Cryolite, Rb3AlF6

A crystallographic approach incorporating multinuclear high field solid state NMR (SSNMR), X-ray structure determinations, TEM observation, and density functional theory (DFT) was used to characterize two polymorphs of rubidium cryolite, Rb₃AlF₆. The room temperature phase was found to be ordered and crystallizes in the Fddd (no. 70) space group with a = 37.26491(1) Å, b = 12.45405(4) Å, and c = 17.68341(6) Å. Comparison of NMR measurements and computational results revealed the dynamic rotations of the AlF₆ octahedra. Using in situ variable temperature MAS NMR measurements, the chemical exchange between rubidium sites was observed. The β-phase, i.e., high temperature polymorph, adopts the ideal cubic double-perovskite structure, space group Fm3m, with a = 8.9930(2) Å at 600 °C. Additionally, a series of polymorphs of K₃AlF₆ has been further characterized by high field high temperature SSNMR and DFT computation.

Highly Transparent Fluorotellurite Glass-Ceramics: Structural Investigations and Luminescence Properties

Crystallization from glass can lead to the stabilization of metastable crystalline phases, which offers an interesting way to unveil novel compounds and control the optical properties of resulting glass-ceramics. Here, we report on a crystallization study of the ZrF₄-TeO₂ glass system and show that under specific synthesis conditions, a previously unreported Te_0.47Zr_0.53O_xF_y zirconium oxyfluorotellurite antiglass phase can be selectively crystallized at the nanometric scale within the 65TeO₂-35ZrF₄ amorphous matrix. This leads to highly transparent glass-ceramics in both the visible and near-infrared ranges. Under longer heat treatment, the stable cubic ZrTe₃O₈ phase crystallizes in addition to the previous unreported antiglass phase. The structure, microstructure, and optical properties of 65TeO₂-35ZrF₄Tm³⁺-doped glass-ceramics, were investigated in detail by means of X-ray diffraction, scanning and transmission electron microscopies, and ¹⁹F, ⁹¹Zr, and ¹²⁵Te NMR, Raman, and photoluminescence spectroscopies. The crystal chemistry study of several single crystals samples by X-ray diffraction evidence that the novel phase, derived from α-UO₃ type, corresponds in terms of long-range ordering inside this basic hexagonal/trigonal disordered phase (antiglass) to a complex series of modulated microphases rather than a stoichiometric compound with various superstructures analogous to those observed in the UO₃-U₃O₈ subsystem. These results highlight the peculiar disorder-order phenomenon occurring in tellurite materials.

In Situ Magnetic Resonance Imaging of a Complete Supercapacitor Giving Additional Insight on the Role of Nanopores

Nuclear magnetic resonance is one of the rare techniques able to probe selectively the ions inside the nanoporous network in supercapacitor devices. With a magnetic resonance imaging method able to detect all ions (adsorbed and nonadsorbed), we record one-dimensional concentration profiles of the active ions in supercapacitors with an electrode configuration close to that used in industry. Larger anionic concentration changes are probed upon charge and discharge in a carbide-derived carbon (CDC) with micropores smaller than 1 nm compared to a conventional nanoporous carbon (CC) with a larger distribution of pore sizes, up to 2 nm. They highlight the increased interaction of the anions with CDC and provide a better understanding of the enhanced capacitance in CDC-based supercapacitors.

Structure and dynamics of high-temperature strontium aluminosilicate melts

We report the study of high-temperature melts (1600-2300 °C) and related glasses in the SrO-Al2O3-SiO2 phase diagram considering three series: (i) depolymerized ([SrO]/[Al2O3] = 3); (ii) fully polymerized ([SrO]/[Al2O3] = 1); and (iii) per-aluminous ([SrO]/[Al2O3] < 1). By considering the results from high-temperature 27Al NMR and high-temperature neutron diffraction, we demonstrate that the structure of the polymerized melts is controlled by a close-to-random distribution of Al and Si in the tetrahedral sites, while the depolymerized melts show smaller rings with a possible loss of non-bridging oxygens on AlO4 units during cooling for high-silica compositions. A few five-fold coordinated VAl sites are present in all compositions, except per-aluminous ones where high amounts of high-coordinated aluminium are found in glasses and melts with complex temperature dependence. In high-temperature melts, strontium has a coordination number of 8 or less, i.e. less than in the corresponding glasses. The dynamics of high-temperature melts were studied from 27Al NMR relaxation and compared to macroscopic shear viscosity data. These methods provide correlation times in close agreement. At very high temperatures, the NMR correlation times can be related to the oxygen self-diffusion coefficient, and we show a decrease of the latter with increasing Si/(Al + Si) ratios for polymerized melts with no compositional dependence for depolymerized ones. The dominant parameter controlling the temperature dependence of the aluminum environment of all melts is the distribution of Al-(OSi)p(OAl)(4-p) units.

Restricted lithium ion dynamics in PEO-based block copolymer electrolytes measured by high-field nuclear magnetic resonance relaxation

The intrinsic ionic conductivity of polyethylene oxide (PEO)-based block copolymer electrolytes is often assumed to be identical to the conductivity of the PEO homopolymer. Here, we use high-field ⁷Li nuclear magnetic resonance (NMR) relaxation and pulsed-field-gradient (PFG) NMR diffusion measurements to probe lithium ion dynamics over nanosecond and millisecond time scales in PEO and polystyrene (PS)-b-PEO-b-PS electrolytes containing the lithium salt LiTFSI. Variable-temperature longitudinal (T₁) and transverse (T₂) ⁷Li NMR relaxation rates were acquired at three magnetic field strengths and quantitatively analyzed for the first time at such fields, enabling us to distinguish two characteristic time scales that describe fluctuations of the ⁷Li nuclear electric quadrupolar interaction. Fast lithium motions [up to O(ns)] are essentially identical between the two polymer electrolytes, including sub-nanosecond vibrations and local fluctuations of the coordination polyhedra between lithium and nearby oxygen atoms. However, lithium dynamics over longer time scales [O(10 ns) and greater] are slower in the block copolymer compared to the homopolymer, as manifested experimentally by their different transverse ⁷Li NMR relaxation rates. Restricted dynamics and altered thermodynamic behavior of PEO chains anchored near PS domains likely explain these results.

ZSM-5 Zeolite: Complete Al Bond Connectivity and Implications on Structure Formation from Solid-State NMR and Quantum Chemistry Calculations

Al site distribution in the structurally complex and industrially important ZSM-5 zeolite is determined by studying the spectroscopic response of Al(OSi)₄ units and using a self-consistent combination of up-to-date solid-state NMR correlations (²⁹Si-²⁷Al and ¹H-²⁷Al D-HMQC) and quantum chemistry methods (DFT-D). To unravel the driving forces behind specific Al sitting positions, our approach focuses on ZSM-5 containing its more efficient OSDA, tetrapropylammonium.

Solid-state 31P and 1H chemical MR micro-imaging of hard tissues and biomaterials with magic angle spinning at very high magnetic field

In this work, we show that it is possible to overcome the limitations of solid-state MRI for rigid tissues due to large line broadening and short dephasing times by combining Magic Angle Spinning (MAS) with rotating pulsed field gradients. This allows recording ex vivo 31P 3D and 2D slice-selected images of rigid tissues and related biomaterials at very high magnetic field, with greatly improved signal to noise ratio and spatial resolution when compared to static conditions. Cross-polarization is employed to enhance contrast and to further depict spatially localized chemical variations in reduced experimental time. In these materials, very high magnetic field and moderate MAS spinning rate directly provide high spectral resolution and enable the use of frequency selective excitation schemes for chemically selective imaging. These new possibilities are exemplified with experiments probing selectively the 3D spatial distribution of apatitic hydroxyl protons inside a mouse tooth with attached jaw bone with a nominal isotropic resolution nearing 100 µm.

Ultrafast acquisition of 1H-1H dipolar correlation experiments in spinning elastomers

We show that two widely used 2D solid-state NMR (ssNMR) pulse sequences can be implemented in an ultrafast (UF) manner, and yield 2D spectra of elastomers in a single scan, under magic-angle spinning. UF 2D ssNMR provides an acceleration of one to several orders of magnitude for classic experiments.

Atomic scale structure of amorphous aluminum oxyhydroxide, oxide and oxycarbide films probed by very high field 27Al nuclear magnetic resonance

The atomic scale structure of aluminum in amorphous alumina films processed by direct liquid injection chemical vapor deposition from aluminum tri-isopropoxide (ATI) and dimethyl isopropoxide (DMAI) is investigated by solid-state ²⁷Al nuclear magnetic resonance at 20 T.

Following lithiation fronts in paramagnetic electrodes with in situ magnetic resonance spectroscopic imaging

Li-ion batteries are invaluable for portable electronics and vehicle electrification. A better knowledge of compositional variations within the electrodes during battery operation is, however, still needed to keep improving their performance. Although essential in the medical field, magnetic resonance imaging of solid paramagnetic battery materials is challenging due to the short lifetime of their signals. Here we develop the scanning image-selected in situ spectroscopy approach, using the strongest commercially available magnetic field gradient. We demonstrate the 7Li magnetic resonance spectroscopic image of a 5 mm-diameter operating battery with a resolution of 100 μm. The time-resolved image-spectra enable the visualization in situ of the displacement of lithiation fronts inside thick paramagnetic electrodes during battery operation. Such observations are critical to identify the key limiting parameters for high-capacity and fast-cycling batteries. This non-invasive technique also offers opportunities to study devices containing paramagnetic materials while operating.

Nuclear magnetic resonance study of sulfate reorientations in LiNaSO4

A nuclear magnetic resonance study of the sulfate ion reorientations in β-LiNaSO4 has been carried out. The influence of the SO4 reorientational jumps on the quadrupolar interactions of (7)Li nuclei was investigated by a jump reorientational model, which has not previously been applied to sulfates. The activation energy required for the SO4 reorientations was found to be 0.19 eV. It was also revealed that the SO4 reorientational disorder should be associated with a small anomaly of a heat capacity at around 600 K, which was previously observed experimentally.

Motional narrowing under diffusion of two spin sub-lattices in LiNaSO4

An expression for the dipolar correlation function characterizing the fluctuations of the Hamiltonian under uncorrelated diffusion of two cationic sub-lattices in a solid has been obtained. A corresponding formula, which can be used for fitting the two-step temperature dependencies of the NMR line width, has been deduced. We also considered the case of a distribution of correlation times and deduced a corresponding analytical fitting function. Elaborated expressions have been applied to the NMR line width analysis of LiNaSO4 in the temperature range 295-788 K.