In this review, we present recent applications of nuclear magnetic resonance (NMR) for probing, at the microscopic level, new quantum states of condensed matter that emerge in strong static and pulsed magnetic fields. We focus on experiments performed in resistive magnets (up to 34 T) and hybrid magnets (max 45 T), further extended to fields beyond 60 T using pulsed magnets, which together offer broad access to these quantum states and the quantum phase transitions between them. After a brief overview of NMR observables, we discuss several topics: quantum spin systems (including spin chains, spin ladders, spin-nematic phases), and their exotic phenomena (magnetization plateaux, Bose-Einstein condensation of triplet excitations), as well as aspects of novel multiferroic systems.
Ultra-high magnetic field NMR spectrometers operating at proton frequencies approaching and exceeding 1.2 GHz are opening new opportunities for biomolecular solid-state NMR. While higher magnetic fields are expected to improve spectral resolution through increased chemical-shift dispersion, the extent to which they continue to improve proton linewidths under fast magic-angle spinning (MAS) conditions has remained unclear. Addressing this question is particularly important as increasingly fast MAS and ever higher magnetic fields become available.Here, we systematically investigate proton linewidths and coherence lifetimes across proton Larmor frequencies from 500 to 1200 MHz under fast MAS conditions. Using microcrystalline GB1 as a benchmark system, we combine bulk and site-specific analyses of proton linewidths and transverse coherence lifetimes (T2′) to characterize linewidths as a function of magnetic field strength. Increasing field strengths systematically improve proton spectral resolution and prolong proton coherence lifetimes, yielding gains that exceed those expected from increased chemical-shift dispersion alone. Linewidth analysis reveals a progressive reduction of non-refocusable broadening at high fields, consistent with suppression of coherent proton spin dynamics. The resulting benefits are particularly pronounced for aliphatic side-chain resonances and remain clearly observable in membrane proteins reconstituted in lipid bilayers, where spectral crowding often limits analysis. These results provide a systematic view of linewidth evolution in proton-detected solid-state NMR and support continuing developments toward higher magnetic fields and faster MAS frequencies for challenging biomolecular systems.
In this study, we have established an empirical 25Mg chemical shift scale for silicates based on experimentally determined isotropic shift δiso values for Mg sites in crystalline compounds spanning coordination numbers from four to eight. These data reveal a robust linear correlation between δiso and the average Mg-O bond distance in the coordination polyhedra, defining approximate δiso ranges of 50 to 30, 27 to 17, 17 to -5, and ≤ -15 ppm for MgIV, MgV, MgVI, and MgVIII environments, respectively. This scale is applied to a comprehensive slice-by-slice analysis of previously reported ultra-high field (35.2 T) 25Mg 3QMAS NMR spectra of three glasses of composition CaMgSi2O6, Na2MgSi3O8, and K2MgSi5O12, revealing a positive correlation between the quadrupolar coupling constant CQ and δiso within two structurally distinct Mg environments assignable to MgVI and MgIV. Quantitative analysis indicates that ∼70-75% of Mg is present as MgIV in all three glasses, yielding an average Mg-O coordination number of ∼4.6 for CaMgSi2O6 glass, in close agreement with the value of ∼4.4 reported in a recent isotope-substituted neutron diffraction study. The finding of the lack of any significant dependence of the Mg-O coordination number on the field strength of the second network modifying cation in these glasses is in sharp contrast with previous reports of a preference of Mg for fourfold coordination in silicate glasses containing low field strength alkali cations.
The use of a nucleus other than the nucleus of interest to establish the chemical shift scale (i.e., indirect referencing) in solid-state nuclear magnetic resonance (SSNMR) spectroscopy is discussed. While the technique is routinely applied in solution NMR studies, it is not applied as widely within the SSNMR community. The benefits of the indirect referencing approach in many SSNMR applications are discussed. In particular, the methods by which indirect methods improve efficiency, reproducibility and help avoid misassignments of chemical shifts are shown. Measurements via direct and indirect methods of a representative sampling of the NMR periodic table are presented to demonstrate the viability of the indirect approach. While any sample with a known chemical shift may be used for indirect referencing, adamantane is demonstrated to be a particularly well-suited solid sample.
Methane is a greenhouse gas with a large global warming potential that enters the marine system from seafloor methane seeps. The anaerobic oxidation of methane (AOM) in submarine areas is crucial to the dynamic equilibrium of the ocean carbon cycle. This study investigated the progression of organic and inorganic matter in the AOM products with different ages using 1H, 13C, 31P, and 1H-31P heteronuclear correlation solid-state NMR. The results reveal that carboxylic acid was formed as a result of the incomplete oxidation of methane. Both carbonate and aliphatic compounds existed in the AOM products. The accumulation of aliphatic carbon, particularly esters, increased progressively with rock age. 31P NMR results show that orthophosphate was the dominant P species in the AOM rocks. More phosphate monoester was formed in the AOM product with the oldest age of around 20,000 years. This study presents NMR as a promising tool for measuring biogeochemical developments in small quantities of authigenic carbonate material and sheds light on the characteristics of methane oxidation products at seeps, which is significant for the global carbon cycle and climate change.
Solid-state NMR faces limitations for liquid sample analysis due to the incompatibility with the magic angle spinning (MAS) method used for averaging anisotropic interactions. In this work, we introduce a simple approach to study frozen aqueous solutions through a direct insertion into an NMR probe pre-cooled at 153K. The study of aqueous sodium bicarbonate, as a model solution, evidences the quench of the fast HCO3- ↔ CO32- interconversion and leads to the observation of the distinct 13C resonances of each ion dispersed in the water frozen matrix. Moreover, pH variation allows the determination of "apparent" pKa in frozen conditions that are found similar to what is expected at room temperature, showing that the freezing process is not modifying the chemical equilibria. We also show that temperature variation from 153 to 213 K does not modify the 13C chemical shift anisotropy of CO32- and HCO3- showing that the local dynamics of the ions in the frozen water environment is not impacted in this temperature range. Extension to 1H-13C two-dimensional NMR evidences water molecules solvating the two ions, as well as the C-OH resonance from bicarbonate, proof of the effective quenching of the HCO3- ↔ CO32- interconversion. This work is the first step towards the development of freeze-quench methods to study crystallization processes from aqueous solution by solid-state NMR including, transient intermediate, chemical exchange or polymorphism.
Precise 13C NMR chemical shifts were measured for a set of reference compounds on five solid-state NMR instruments to evaluate reproducibility across different field strengths (300-1000 MHz), MAS spinning rates and spectrometer manufacturers. Reference materials comprised five compounds included in a pan-European research program BEST-CSP dealing with bringing together experimental and theoretical approaches to investigate crystalline materials. The structures included molecular solids with pharmaceutical relevance. All instruments were standardized to a common referencing protocol using internal DSS standard. The resulting 13C isotropic shifts showed excellent agreement across instruments: variations were typically within 0.2 ppm, with the largest observed discrepancy being 0.3 ppm. Statistical analysis confirmed no significant systematic dependence on magnetic field strength or MAS rate - chemical shift values at 300 MHz and 1000 MHz were virtually identical given consistent referencing. Error analysis indicates that measured shifts are robust within tenths of ppm, reinforcing the reliability of chemical shift databases aggregated from different labs. These findings highlight that, with consistent scaling, solid-state 13C NMR chemical shifts are reproducible across diverse hardware, lending confidence to multi-instrument studies and combined chemical shift compilations.
Layered boron nitride (BN) is a two-dimensional (2D) insulator that exhibits several polytypes, which differ in the stacking sequence of adjacent atomic planes. The relative shift and rotation of subsequent planes modify the crystal symmetry and thereby determine the crystal's fundamental properties. While most previous NMR-oriented studies have focused on AA'-stacked hexagonal BN (hBN), ABC-stacked rhombohedral BN (rBN) has not yet been investigated. In this study, we present the magic-angle spinning 11 B NMR spectra of rBN and compare them with those of hBN and with DFT calculations. We also measure spin-lattice relaxation of both polytypes. Our findings suggest that both phases exhibit nearly identical NMR parameters, including chemical shifts and quadrupole couplings. However, our rBN and hBN samples differ significantly in relaxation, which may be attributed to different growth methods, resulting in different concentrations of paramagnetic centers. Interestingly, we also observe extremely long spin-lattice relaxation times for terminal groups in hBN, which have rendered them unobservable in many previous studies. Experimental and computational 11 B NMR comparative study of MOVPE-grown rhombohedral and bulk hexagonal boron nitride A PREPRINT
137Ba nuclear quadrupole interactions (NQI) are measured in zero field using nuclear quadrupole resonance (NQR) for a series of compounds, (BaBr2.2H2O, BaCl2.2H2O, BaSO4, BaMoO4, BaCO3) where values of the quadrupole interaction have previously been reported using frequency stepped and/or ultra high (21.1 T) magnetic field NMR. Typically barium can show large quadrupole coupling constants (CQ > 10 MHz). In addition barium phosphate Ba3(PO4)2 has not previously been investigated experimentally by nuclear resonance. In the present work, theoretical prediction of a very large 137Ba coupling constant for one of the two Ba sites, Ba(1) (12-coordinated), in Ba3(PO4)2 shows good agreement with the NQR measurement. The small NQI 137Ba coupling constant for the Ba(2) site (10-coordinated) in Ba3(PO4)2 has been derived from the second-order perturbed NMR lineshape. The development of the observation of barium by magnetic resonance is briefly reviewed to provide some perspective on the current study. On the basis of the results presented here, the accuracy and straightforward nature of the zero field NQR approach offers advantages for potential in operando experiments that are difficult at high field.
Layered metal hydroxides can be exfoliated into functional nanosheets via solvent intercalation, yet probing the atomic-level solvation processes remains challenging. Herein, we employ 79/81Br solid-state nuclear magnetic resonance (SSNMR) spectroscopy to directly probe the local environments of interlayer anions in bromide-intercalated layered yttrium hydroxide (LYH-Br). Upon treatment with a series of solvents of varying polarity, the overall spectral lineshapes remain largely unchanged in weakly interacting systems (toluene (PhMe), acetone (ACE), isopropanol (IPA)), indicating preservation of the local structural framework. Increasing solvent polarity leads to a reduction in 79Br NMR signal intensity, particularly in the case of formamide (FM). By combining complementary characterization techniques and transverse relaxation analysis, we show that this signal attenuation originates from shortened T2 relaxation times rather than structural degradation. These results reveal that polar solvent intercalation perturbs the local dynamics and solvation environment of interlayer Br- anions. Furthermore, solvent-induced effects are largely reversible for PhMe, ACE, IPA and N, N-dimethylformamide (DMF) upon vacuum drying, whereas FM remains trapped within the interlayer spaces, illustrating stronger host-guest interactions and altered local dynamics. This work demonstrates solid-state 79/81Br NMR as a powerful tool for directly distinguishing solvation-driven intercalation mechanisms in layered materials.
This paper describes the first known detection of cobaltite (CoAsS) by 75As NQR spectroscopy. The 75As resonance was observed from a natural cobaltite sample with a peak signal at 87 MHz with a FWHM of 1.11 MHz. The T1 and T2 relaxation times were measured and found to be 29.4 ms and 343 μs respectively. This observation was aided by simulations of the unit cell using the density functional theory (DFT) program, WIEN2k [1] that simulated the peak resonance within 5%. The detection of cobaltite was motivated by the expansion on the suite of minerals that are amenable to quantification in mining applications using magnetic resonance based on-line monitoring systems.
Magic-angle spinning (MAS) NMR is predicated on the requirement that the rotor spin at the magic angle, yet in current practice, the effective rotor angle is not directly monitored during the experiment. Here we show that the use of a single-crystal sapphire spacer in a standard zirconia rotor provides a simple in situ sensor of the effective spinning angle and, remarkably, of rotor mechanical behavior as well. By monitoring the 27Al spectrum of the sapphire spacer, we show that the effective angle drifts with changes in MAS rate and temperature, and can change substantially upon rotor exchange. The same spectra further reveal otherwise hidden mechanical instabilities in a spinning rotor through features such as frequency-modulation sidebands arising from coherent whirl modes of the rotor-bearing system. Experiments on GB1 microcrystals enable us to quantify how angular offsets affect spectral resolution and transverse relaxation rates. Our results establish sapphire spacers as a practical in situ probe of magic angle alignment and as a new diagnostic for rotor stability.
We present an ultrahigh-field magic-angle spinning (MAS) solid-state NMR (ssNMR) study to characterize intact nontuberculous mycobacteria (NTM). Hydrated and dried whole-cell Mycobacterium abscessus samples were investigated by combining conventional high-field ssNMR at 750 MHz with ultrahigh-field ssNMR at 1.2 GHz and ultrafast MAS at 100 kHz. To improve sensitivity and enable multidimensional experiments, 13C/15N isotope labeling was performed after growth in synthetic cystic fibrosis medium (SCFM). We utilized 1D13C and 2D 1H-13C and 13C-13C ssNMR experiments to characterize the chemical composition, dynamics, and structural organization of the M. abscessus cell envelope. The 13C isotope-labeling efficiency was found to be non-uniform across different molecular classes, with high incorporation into polysaccharides and lower incorporation into lipid and peptide-associated signals. INEPT- and CP-based experiments selectively probed flexible and rigid fractions of the samples, revealing substantial differences in linewidth, dynamics, and sensitivity between hydrated and dried preparations. Conventional 750 MHz experiments provided high-resolution multidimensional spectra and enabled identification of distinct chemical environments associated with peptidoglycan, arabinogalactan, mycolic acids, lipids, and peptide-associated components. Ultrahigh-field ssNMR at 1.2 GHz combined with ultrafast MAS and 1H detection improved resolution and sensitivity per mg of sample. The largest improvement of 100 kHz and 1.2 GHz system is observed for the CP spectra of the dry sample, where significantly better FWHM of 1H: 250 Hz (∼0.2 ppm) and 13C: 300 Hz (∼1 ppm) is observed compared to 10 kHz and 750 MHz system with 1H: 300 Hz (∼0.4 ppm) and 13C: 600 Hz (∼3.2 ppm). This allowed the detection of new aromatic and possible nucleic-acid-associated signals. Together, these results demonstrate that ultrahigh-field and ultrafast-MAS ssNMR enables detailed characterization of intact NTM cell envelopes under near-native conditions and provides a framework for future molecular investigations of antimicrobial interactions.
Understanding Lithium-ion conduction mechanisms is key to develop new solid-state electrolytes. However, Li-ion dynamics in glassy electrolytes are intricate and remain unclear due to the challenges in understanding the local structures of glasses. In this work, we probe the Li-ion conduction mechanism in Li2S-P2S5 binary glassy system using the combination of variable-temperature 7Li and 31P NMR relaxometry. The temperature-dependent 31P NMR spin-lattice relaxation measurements show that dynamics of thiophosphate dimers are sluggish in 67Li2S-33P2S5 and 70Li2S-30P2S5 glasses while in 75Li2S-25P2S5 glass, the anionic dynamics are enhanced significantly due to the increased amounts of isolated PS43- units. The energy barrier for 31P rotation is decreased by a factor of ∼2, indicating drastic enhancement in 31P dynamics. We find that the cation and anion motion is highly cooperative in the glassy electrolyte system. The long-range Li-ion diffusion barrier decreases from 0.30 eV in 67Li2S-33P2S5 glass to 0.14 eV in 75Li2S-25P2S5 glass. It is clear that the rapid PS43- rotation can speed up Li-ion migration. Moreover, a large amount of PS43- ions break the rigid networks formed by thiophosphate dimers. This may loosen the glass matrix, expanding Li-ion percolation channels in the 75Li2S-25P2S5 glass.
Owing to their high stability, Zr-based Metal-Organic Frameworks (MOFs) are promising materials for CO2 adsorption. Nevertheless, their rational improvement for this application requires identifying the nature of chemisorbed species and their interactions with these MOFs. By combining solid-state NMR and vibrational spectroscopies, we evidence that under 1 bar of CO2, UiO-66 adsorbs CO2 via both physi- and chemi-sorption. Using conventional solid-state NMR experiments and dynamic nuclear polarization (DNP), we demonstrate the close proximity between physisorbed CO2 and the organic linkers. We also show that the chemisorbed species are bicarbonate anions formed by the reaction with hydroxyl groups of Zr clusters, while no carbamate anion and carbamic acid were detected. Both physi- and chemi-sorbed CO2 species were also detected for UiO-66 built from 2-aminoterephtalate, whereas for fumarate-based UiO-66-Fum, only physisorption was observed.
Manganese oxides (MnOx) represent an important and versatile class of electrode materials for electrochemical energy-storage technologies, particularly those based on aqueous electrolytes ranging from strongly alkaline to mildly acidic pH. The charge-storing functionality of such oxides can be further enhanced by expressing them in nanoscale forms incorporated into porous carbon substrates. Because the resulting MnOx@carbon hybrid materials are themselves structurally and compositionally complex, and charge-storage mechanisms in aqueous media may involve supporting electrolyte cations (e.g., Li+, Na+) or inevitably protons (from H2O), a wide range of characterization tools is required to understand and optimize electrochemical function. In this study, we use 1H NMR spectroscopy to probe the structural environments available to protons in such hybrids as synthesized by electroless deposition of birnessite-like MnOx onto carbon nanofoam papers (MnOx@CNFP). Two features are observed in the 1H spectrum of this material, attributed to protons located at different distances away from the MnO6 octahedral layers coating the carbon walls. We show that chemical exchange occurs between protons in these two environments in a two-step process. We also use 1H chemical shift imaging of the MnOx@CNFP electrode in a device-like configuration and verify that this technique can isolate the signal of this electrode architecture in a device with multiple components (separator, electrolyte, counter electrode). These results showcase the ability of NMR to interrogate the structural environments of protons in an architected MnOx@CNFP electrode and serve as the foundation for future in situ/operando investigations of this system.
Three-dimensional (3D) spectra are essential for resonance assignment of complex biomolecules. Here we present a CCC spectrum that correlates the three backbone carbon resonances of protein residues and is applicable for the fast magic-angle spinning regime, here 55 kHz. The corresponding pulse sequence is constructed from dipolar recoupling elements that transfer both x- and y- elements of magnetization (preservation of equivalent pathways). The sequence is proposed as a well-resolved option for assignment of CB resonances, which are particularly useful for determination of residue type. The sensitivity of this CCC spectrum is found to be surprisingly high, considering that it is a carbon detected sequence, at about 50-100 percent of the sensitivity measured in a comparable CB(CA)NH spectrum. The sequence affords high resolution intra-residue correlations for all standard amino acids, including for proline residues.
Nuclear magnetic resonance (NMR) measurements of the hyperfine parameters (quadrupolar, shifts) at the metal and boron sites are reported from an isomorphous set of eleven stable AlB2 structure-type space group 191 metal diborides, the main group metal diborides MgB2 and AlB2, and transition metal diborides ScB2, TiB2, VB2, CrB2, YB2, ZrB2, NbB2, HfB2, TaB2. Nuclear quadrupole resonance (NQR) studies were performed to locate resonances from 177Hf and 181Ta in the respective diborides. The electric field gradients, Vzz, nuclear quadrupole coupling constants, Cq, and Knight shift values, Kiso, at the both the metal and boron sites, are reported and are discussed in terms of current state-of-the-art quantum chemical first-principles calculations, as well as being correlated with electronic and cohesive properties of these materials. New experimental results and calculations are presented in addition to re-analysis of existing literature data to test hypotheses of how structure and composition can be tailored to achieve desired physical properties. This comprehensive set of experimental NMR data provides a direct link between measurable hyperfine parameters, calculated bonding parameters, and important physical properties including catalytic activity and asymptotic bulk hardness. The use of magnetic resonance for detection of critical metal diborides via their hyperfine interactions and linking these interactions to physical characteristics opens improved pathways for materials design with novel properties, as well as a method to fingerprint material signatures useful in the circular economy for resource identification, verification, recovery, and reuse.
The nuclear quadrupole coupling constant at the boron site, in a series of sixteen isomorphous metal hexaborides with the CaB6 structure, is shown to vary as a function of lattice parameter, metal ion size, and metal ion valence. The NMR data in the literature are comprehensively reviewed and some reanalysed. Electric field gradient (EFG) values derived from experiment are compared with those calculated using first principles density functional theory. Boron EFG values are used as an indicator of the metal-boron bonding and are correlated to cohesive properties, including asymptotic bulk hardness values and melting temperature, to examine the efficacy of NMR aiding materials properties optimisation.
