Nuclear Magnetic Resonance Approach Research Articles

Enhancing permeability estimation methods in Brazilian pre-salt complex carbonate reservoirs

Carbonate pre-salt reservoirs pose formidable challenges for formation evaluation and estimation of petrophysical properties such as rock flow capacity. The high complexity of the pore system and its textural heterogeneity often lead to poor predictions when using conventional formation evaluation methods. This paper discusses and tests the applicability of two approaches to calculate the absolute permeability curves for the carbonate reservoirs of the Barra Velha Formation in the Santos Basin, proposing a fine-tuned workflow for these complex rocks. In developing our workflow, we used data from a case study well, comprising a complete well log suite and two formation tests, and routine core analysis results (RCAL) in core plugs and sidewall cores. Our workflow consists of: (1) reinterpreting the nuclear magnetic resonance (NMR) log in vugular intervals by decomposing the transversal relaxation time spectra; (2) calculating the absolute permeability by the Timur–Coates model and adjusting the coefficients with the RCAL results from representative samples; (3) applying the Flow Zone Indicator (FZI) method for rock typing to optimally define Hydraulic Flow Units (HFU); (4) checking the consistency of HFUs regarding pore geometry and lithological characteristics; (5) evaluating the performance of the models against core data and formation tests. The predicted permeability curves performed well for the NMR and FZI models when compared to the RCAL data from representative samples, with mean absolute errors for the logarithm of permeabilities equal to 0.78 and 0.87, respectively. This represents an improvement of 15% and 5% when compared to the simplistic approach that uses a power law to relate porosity to permeability from RCAL. These curves also reasonably reproduce the results from the formation tests for the top part of the reservoir, where matrix porosity dominates the flow. However, the NMR and FZI permeability curves underestimate the test results at the bottom part of the reservoir, where karstic and fracture features dominate, demonstrating limitations in these permeability estimation methods for this specific scenario. From our observations, we propose several improvements to enhance the current methods for estimating absolute permeability in pre-salt carbonate reservoirs. In the case of the NMR approach, it is essential to consider the effects of mud invasion in vugs for the correct estimation of the proportions of free and irreducible fluids. In the FZI approach, optimization in defining the quantity and limits of hydraulic flow units is important, which shows that four units are sufficient to represent the reservoir interval.

Supramolecular Arrangement and Conformational and Dynamic Properties of Chiral Smectic Liquid Crystals Obtained through Nuclear Magnetic Resonance: A Brief Review

Ferroelectric and antiferroelectric smectic liquid crystalline (LC) phases are still at the center of investigations and interests for both their fundamental properties and variety of technological applications. This review aims to report the main contributions based on different nuclear magnetic resonance (NMR) techniques to the study of chiral liquid crystalline calamitic mesogens forming smectic phases, such as the SmA, the SmC* (ferroelectric), and the SmC*A (antiferroelectric) phases. 2H NMR and 13C NMR techniques and their combination were of help in clarifying the local orientational properties (i.e., the molecular and fragments’ main orientational order parameters) at the transition between the SmA and the SmC* phases, and in the particular case of de Vries liquid crystals, NMR studies gave important clues regarding the actual models describing the molecular arrangement in these two phases formed by de Vries LCs. Moreover, this review describes how the combination of 2H NMR relaxation times’ analysis, 1H NMR relaxometry, and 1H NMR diffusometry was successfully applied to the study of chiral smectogens forming the SmC* and SmC*A phases, with the determination of relevant parameters describing both rotational molecular and internal motions, collective dynamics, and translational self-diffusion motions. Several cases will be reported concerning NMR investigations of chiral ferroelectric and antiferroelectric phases, underlining the great potential of combined NMR approaches to the study of supramolecular, conformational, and dynamic properties of liquid crystals.

Two-dimensional low-field nuclear magnetic resonance approach for the detection of metabolic syndrome in human serum

Metabolic syndrome (MetS) has become a major public health challenge in recent years. Nuclear magnetic resonance, as a nondestructive measurement, has been widely used in medical diagnosis and screening. Compared to conventional magnetic resonance imaging and nuclear magnetic spectroscopy, low-field nuclear magnetic resonance is superior in portability, simplicity, and low-cost. In this study, a novel approach based on low-field magnetic resonance analysis is proposed to detect metabolic syndrome. T1–T2 correlation relaxometry is employed to measure human serum. Combining with a classification model based on partial least squares discriminant analysis (PLS-DA), the detection of metabolic syndrome is realized. The classification models based on both T1–T2 relaxation correlation data and spectrum are compared. Additionally, classification model based on convolutional neural networks (CNNs) is also evaluated for comparison. The experimental results indicate that the PLS-DA model based on the T1–T2 spectrum achieves a better performance. Specifically, the area under curve, accuracy, F1 score, recall and precision of the classification model evaluated on testing group are 0.784, 70.91%, 75.00%, 77.42%, and 72.73%, respectively. On the other hand, the testing results of CNN model trained using T1–T2 spectrum are 0.774, 65.45%, 61.22%, 48.39%, and 83.33% for AUC, accuracy, F1 score, recall, and precision. The experimental results reveal the limitation of CNN models on small datasets. In this study, T1–T2 correlation relaxometry is employed for the analysis of MetS for the first time, and the feasibility of proposed method has been demonstrated.

Revealing the Local Structure and Dynamics of the Solid Li Ion Conductor Li3P5O14.

The development of fast Li ion-conducting materials for use as solid electrolytes that provide sufficient electrochemical stability against electrode materials is paramount for the future of all-solid-state batteries. Advances on these fast ionic materials are dependent on building structure-ionic mobility-function relationships. Here, we exploit a series of multinuclear and multidimensional nuclear magnetic resonance (NMR) approaches, including 6Li and 31P magic angle spinning (MAS), in conjunction with density functional theory (DFT) to provide a detailed understanding of the local structure of the ultraphosphate Li3P5O14, a promising candidate for an oxide-based Li ion conductor that has been shown to be a highly conductive, energetically favorable, and electrochemically stable potential solid electrolyte. We have reported a comprehensive assignment of the ultraphosphate layer and layered Li6O16 26- chains through 31P and 6Li MAS NMR, respectively, in conjunction with DFT. The chemical shift anisotropy of the eight resonances with the lowest 31P chemical shift is significantly lower than that of the 12 remaining resonances, suggesting the phosphate bonding nature of these P sites being one that bridges to three other phosphate groups. We employed a number of complementary 6,7Li NMR techniques, including MAS variable-temperature line narrowing spectra, spin-alignment echo (SAE) NMR, and relaxometry, to quantify the lithium ion dynamics in Li3P5O14. Detailed analysis of the diffusion-induced spin-lattice relaxation data allowed for experimental verification of the three-dimensional Li diffusion previously proposed computationally. The 6Li NMR relaxation rates suggest sites Li1 and Li5 (the only five-coordinate Li site) are the most mobile and are adjacent to one another, both in the a-b plane (intralayer) and on the c-axis (interlayer). As shown in the 6Li-6Li exchange spectroscopy NMR spectra, sites Li1 and Li5 likely exchange with one another both between adjacent layered Li6O16 26- chains and through the center of the P12O36 12- rings forming the three-dimensional pathway. The understanding of the Li ion mobility pathways in high-performing solid electrolytes outlines a route for further development of such materials to improve their performance.

Experimental Validation of Enhanced Information Capacity by Quantum Switch in Accordance with Thermodynamic Laws.

We experimentally probe the interplay of the quantum switch with the laws of thermodynamics. The quantum switch places two channels in a superposition of orders and may be applied to thermalizing channels. Quantum-switching thermal channels has been shown to give apparent violations of the second law. Central to these apparent violations is how quantum switching channels can increase the capacity to communicate information. We experimentally show this increase and how it is consistent with the laws of thermodynamics, demonstrating how thermodynamic resources are consumed. We use a nuclear magnetic resonance approach with coherently controlled interactions of nuclear spin qubits. We verify an analytical upper bound on the increase in capacity for channels that preserve energy and thermal states, and demonstrate that the bound can be exceeded for an energy-altering channel. We show that the switch can be used to take a thermal state to a state that is not thermal, while consuming free energy associated with the coherence of a control system. The results show how the switch can be incorporated into quantum thermodynamics experiments as an additional resource.

Time-Resolved Evaluation of L-Dopa Metabolism in Bacteria-Host Symbiotic System and the Effect on Parkinson's Molecular Pathology.

The gut microbiome influences drug metabolism and therapeutic efficacy. Still, the lack of a general label-free approach for monitoring bacterial or host metabolic contribution hampers deeper insights. Here, a 2D nuclear magnetic resonance (NMR) approach is introduced that enables real-time monitoring of the metabolism of Levodopa (L-dopa), an anti-Parkinson drug, in both live bacteria and bacteria-host (Caenorhabditis elegans) symbiotic systems. The quantitative method reveals that discrete Enterococcus faecalis substrains produce different amounts of dopamine in live hosts, even though they are a single species and all have the Tyrosine decarboxylase (TyrDC)gene involved in L-dopa metabolism. The differential bacterial metabolic activity correlates with differing Parkinson's molecular pathology concerning alpha-synuclein aggregation as well as behavioral phenotypes. The gene's existence or expression is not an indicator of metabolic activity is also shown, underscoring the significance of quantitative metabolic estimation in vivo. This simple approach is widely adaptable to any chemical drug to elucidate pharmacomicrobiomic relationships and may help rapidly screen bacterial metabolic effects in drug development.

Intact NMR Approach Quickly Reveals Synchronized Microstructural Changes in Oil-in-Water Nanoemulsion Formulations

A soft-core oil-in-water (o/w) nanoemulsion (NE) is composed of nanometer (nm) sized oil droplets, stabilized by a surfactant layer and dispersed in a continuous bulky water phase. Characterization of the o/w NE molecule arrangements non-invasively, particularly the drug phase distribution (DPD) and its correlation to oil globule size (OGS), remains a challenge. Here we demonstrated the analytical methods of intact 19F Nuclear Magnetic Resonance (NMR) and 1H diffusion ordered spectroscopy (DOSY) NMR for their specificity in measuring DPD and OGS, respectively, on three NE formulations containing the active ingredient difluprednate (DFPN) at the same concentration. The results illustrated synchronized molecular rearrangement reflected in the DPD and OGS upon alterations in formulation. Addition of surfactant resulted in a higher DPD in the surfactant layer, and concomitantly smaller OGS. Mechanic perturbation converted most of the NE globules to the smaller thermodynamically stable microemulsion (ME) globules, changing both DPD and OGS to ME phase. These microstructure changes were not observed using 1D 1H NMR; and dynamic light scattering (DLS) was only sensitive to OGS of ME globule in mechanically perturbed formulation. Collectively, the study illustrated the specificity and essential role of intact NMR methods in measuring the critical microstructure attributes of soft-core NE systems quickly, accurately, and non-invasively. Therefore, the selected NMR approach can be a unique diagnostic tool of molecular microstructure or Q3 property in o/w NE formulation development, and quality assurance after manufacture process or excipient component changes.Graphical abstract

#2985 Gut microbiome-dependent systemic alterations in experimental chronic kidney disease

Abstract Background and Aims Patients diagnosed with Chronic Kidney Disease (CKD) undergo a notable decline in both quality of life and life expectancy, primarily attributable to the heightened prevalence of cardiovascular diseases (CVD). These conditions not only contribute to the initiation of CKD but are also a consequence of inflammation associated with CKD. Despite optimal kidney replacement therapies, irreversible alterations of the CV system may persist. The responsible mechanisms in CKD leading to CVD are incompletely understood. CKD is characterized by gut microbial dysbiosis, with a significant proportion of uremic toxins suspected to have microbial origin. We hypothesize that the gut microbiota promotes inflammation and CV risk in states of impaired kidney function. Method Experimental CKD was induced in 129sv mice by 5/6 nephrectomy. Prior to nephrectomy, mice were assigned to receive either glucose (Ctrl) or a non-absorptive antibiotic cocktail (comprising Ampicillin, Metronidazole, Neomycin, and Vancomycin, Abx) via the drinking water to deplete their microbiomes throughout the 13-week study period. Ctrl and Abx-treated Sham-operated mice served as controls. Plasma, feces, and urine specimens were systematically collected at diverse time intervals, facilitating the longitudinal exploration of metabolite dynamics and CKD progression through an untargeted Nuclear Magnetic Resonance (NMR) approach. Simultaneously, echocardiography assessments were conducted at identical time points to assess cardiac function. Results Abx-treated CKD mice displayed improved kidney function, demonstrated by significantly reduced levels of plasma Cystatin C (0.2913 ± 0.1850 mg/L) compared to Ctrl (0.9133 ± 0.6616 mg/L)(p = 0.0256). Hearts from Abx-treated CKD mice exhibited significantly less remodeling, independent of their blood pressure (radiotelemetry measurements). The ratio of left ventricular (LV) mass to tibia length was 4.858 ± 0.3453 in the Abx-treated group compared to Ctrl (8.198 ± 0.3542) (p < 0.0001). Sirius red stained hearts revealed significantly less fibrosis in Abx-treated CKD mice (5.784 ± 5.465%) compared to Ctrl (11.98 ± 3.741%) (p = 0.0218). The cardiac expression of several damage-associated genes (Npbb, Ctgf, and Ngal) portrayed the same trend. To elucidate the interplay between the microbiome and the immune system underlying these observed effects, we provide a comprehensive atlas of the immune landscape in different organs (blood, spleen, heart, intestine), along with a catalogue of gut-derived metabolites, shedding light on the systemic alterations induced by microbiome-dependent mechanisms in CKD. Conclusion Our findings suggest that microbiome-dependent mechanisms drive kidney function decline and cardiac remodeling in experimental CKD. These results underscore the interplay between microbial alterations, metabolite dynamics, immune response, and cardiovascular complications in the context of CKD.

Cation Distribution and Anion Transport in the La3Ga5-xGe1+xO14+0.5x Langasite Structure.

Exploration of compositional disorder using conventional diffraction-based techniques is challenging for systems containing isoelectronic ions possessing similar coherent neutron scattering lengths. Here, we show that a multinuclear solid-state Nuclear Magnetic Resonance (NMR) approach provides compelling insight into the Ga3+/Ge4+ cation distribution and oxygen anion transport in a family of solid electrolytes with langasite structure and La3Ga5-xGe1+xO14+0.5x composition. Ultrahigh field 71Ga Magic Angle Spinning (MAS) NMR experiments acquired at 35.2 T offer striking resolution enhancement, thereby enabling clear detection of Ga sites in different coordination environments. Three-connected GaO4, four-connected GaO4 and GaO6 polyhedra are probed for the parent La3Ga5GeO14 structure, while one additional spectral feature corresponding to the key (Ga,Ge)2O8 structural unit which forms to accommodate the interstitial oxide ions is detected for the Ge4+-doped La3Ga3.5Ge2.5O14.75 phase. The complex spectral line shapes observed in the MAS NMR spectra are reproduced very accurately by the NMR parameters computed for a symmetry-adapted configurational ensemble that comprehensively models site disorder. This approach further reveals a Ga3+/Ge4+ distribution across all Ga/Ge sites that is controlled by a kinetically governed cation diffusion process. Variable temperature 17O MAS NMR experiments up to 700 °C importantly indicate that the presence of interstitial oxide ions triggers chemical exchange between all oxygen sites, thereby enabling atomic-scale understanding of the anion diffusion mechanism underpinning the transport properties of these materials.

Pore-scale physics of ice melting within unconsolidated porous media revealed by non-destructive magnetic resonance characterization

Melting of ice in porous media widely exists in energy and environment applications as well as extraterrestrial water resource utilization. In order to characterize the ice-water phase transition within complicated opaque porous media, we employ the nuclear magnetic resonance (NMR) and imaging (MRI) approaches. Transient distributions of transverse relaxation time T2 from NMR enable us to reveal the substantial role of inherent throat and pore confinements in ice melting among porous media. More importantly, the increase in minimum T2 provides new findings on how the confinement between ice crystal and particle surface evolves inside the pore. For porous media with negligible gravity effect, both the changes in NMR-determined melting rate and our theoretical analysis of melting front confirm that conduction is the dominant heat transfer mode. The evolution of mushy melting front and 3D spatial distribution of water content are directly visualized by a stack of temporal cross-section images from MRI, in consistency with the corresponding NMR results. For heterogeneous porous media like lunar regolith simulant, the T2 distribution shows two distinct pore size distributions with different pore-scale melting dynamics, and its maximum T2 keeps increasing till the end of melting process instead of reaching steady in homogeneous porous media.

From Milliseconds to Minutes: Melittin Self-Assembly from Concerted Non-Equilibrium Pressure-Jump and Equilibrium Relaxation Nuclear Magnetic Resonance.

Non-equilibrium kinetics techniques like pressure-jump nuclear magnetic resonance (NMR) are powerful in tracking changes in oligomeric populations and are not limited by relaxation rates for the time scales of exchange that can be probed. However, these techniques are less sensitive to minor, transient populations than are Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion experiments. We integrated non-equilibrium pressure-jump and equilibrium CPMG relaxation dispersion data to fully map the kinetic landscape of melittin tetramerization. While monomeric peptides weakly form dimers (Kd,D/M ≈ 26 mM) whose population never exceeds 1.6% at 288 K, dimers associate tightly to form stable tetrameric species (Kd,T/D ≈ 740 nM). Exchange between the monomer and dimer, along with exchange between the dimer and tetramer, occurs on the millisecond time scale. The NMR approach developed herein can be readily applied to studying the folding and misfolding of a wide range of oligomeric assemblies.

HPLC and LC-MS/MS-Based Quantitative Characterization of Related Substances Associated with Sotalol Hydrochloride.

In total, three related substances (RS) associated with sotalol hydrochloride (STHCl) were herein identified with a novel gradient high-performance liquid chromatography (HPLC) protocol. Further characterization of these substances was then performed via liquid chromatography-mass spectroscopy (LC-MS/MS) and nuclear magnetic resonance (NMR) approaches. For these analyses, commercial STHCl samples were used for quantitative HPLC studies and the degradation of STHCl under acidic (1M HCl), alkaline (1M NaOH), oxidative (30% H2O2), photolytic (4500 Lx), and thermal stress conditions (100 °C) was assessed. This approach revealed this drug to be resistant to acidic, alkaline, and high-temperature conditions, whereas it was susceptible to light and oxidation as confirmed through long-term experiments. The putative mechanisms governing RS formation were also explored, revealing that RS3 was derived from the manufacturing process, whereas RS2 was generated via oxidation and RS1 was generated in response to light exposure. The cytotoxicity of these RS compounds was then assessed using MTT assays and acute toxicity test. Overall, this study provides details regarding the characterization, isolation, quantification, and toxicological evaluation of STHCl and associated RS compounds together with details regarding the precise, specific, and reliable novel HPLC technique, thus providing the requisite information necessary to ensure STHCl purity and safety.

Carrier density and delocalization signatures in doped carbon nanotubes from quantitative magnetic resonance.

High-performance semiconductor materials and devices are needed to supply the growing energy and computing demand. Organic semiconductors (OSCs) are attractive options for opto-electronic devices, due to their low cost, extensive tunability, easy fabrication, and flexibility. Semiconducting single-walled carbon nanotubes (s-SWCNTs) have been extensively studied due to their high carrier mobility, stability and opto-electronic tunability. Although molecular charge transfer doping affords widely tunable carrier density and conductivity in s-SWCNTs (and OSCs in general), a pervasive challenge for such systems is reliable measurement of charge carrier density and mobility. In this work we demonstrate a direct quantification of charge carrier density, and by extension carrier mobility, in chemically doped s-SWCNTs by a nuclear magnetic resonance approach. The experimental results are verified by a phase-space filling doping model, and we suggest this approach should be broadly applicable for OSCs. Our results show that hole mobility in doped s-SWCNT networks increases with increasing charge carrier density, a finding that is contrary to that expected for mobility limited by ionized impurity scattering. We discuss the implications of this important finding for additional tunability and applicability of s-SWCNT and OSC devices.

Development of a NMR Device Adapted to Operando Analysis of Electrochemical Commercial Cells

NMR (Nuclear Magnetic Resonance) spectroscopy is a common analytical technique for analysing electrode materials. Most of these analyses are ex situ NMR measurements, a post mortem analysis of the cell. Yet, development of in situ and operando NMR considerably increased. Since the first in situ measurement reported by Gerald et al [1] in 2000, a large variety of operando NMR approaches have been developed and applied to batteries [2–5].Two levers of improvement remain for operando NMR: the battery-casing design, usually home-made, and the geometry of the NMR resonator used to detect the spectrum.Battery-casing goes from flexible cells in a clear pouch to capsule, Swagelok or coin cells. Home-made casings are usually used to avoid distortion and sensitivity loss in the NMR measurement, attributed to the conductive casings. Another way of improvement is the type of NMR resonator to fit a larger variety of cell geometries. Solenoids, saddle coil, hairpin coil or parallel plates are currently used.Electrochemistry is sensitive to cell fabrication, so home-made cells are intrinsically less reproducible than commercial cells. To increase the repeatability for a higher number of cycles and from one cell to another, we collaborate with a cell maker to get industrial pouch cells and we use commercial protocols. Nevertheless, studying such cells implies new challenges. First, strong and controlled pressure must be applied on the cell. An innovative pressure system was created to be compatible with the NMR requirements, mainly low available space and the absence of magnetic or strongly paramagnetic materials. It also involved adapting the resonator to the commercial cell geometry. The second challenge is the attenuation and distortion of the NMR signal by conductors (skin effect for radio-frequency fields).Recently, Walder [6]. arose our interest with their report on operando NMR measurement for a stainless steel coin cell. We will present measurements that quantify the influence of the components of a commercial battery (casing material, electrodes, current collector and number of stacks).This development and these measurements will lead in close future to performing operando NMR of commercial cells in fast charging conditions (for example on silicon Li-ion batteries).[1] R. E. Gerald et al., J. Power Sources 89, 237 (2000).[2] X. Liu et al., Adv Mater 33, 2005878 (2021).[3] O. Pecher et al., Chem. Mater. 29, 213 (2017).[4] K. Gotoh et al., J. Mater. Chem. A 8, 14472 (2020).[5] K. J. Sanders et al., Carbon 189, 377 (2022).[6] B. J. Walder et al., Sci. Adv. 7, eabg8298 (2021).

Novel Operando Nuclear Magnetic Resonance Approach for Tracking the Electrode State of Charge in Li/Na-Ion Batteries

Lithium and sodium-ion batteries have become the focal point of interest for the energy transition due to their promising applications for electric cars and energy grid storage. Operando characterization of batteries is critical to understand the degradation processes and increasing their electrochemical performance, especially in abusive conditions like during fast charges. Knowledge of the redox state of each electrode is essential to identify the origins of capacity loss in full batteries. Among the methods used for these investigations, operando Nuclear Magnetic Resonance (NMR) methods are promising since, without destroying the battery, they enable monitoring in real-time the electrochemical processes and the formation of short-lived metastable or reactive phases [1,2].Up to now, most operando NMR studies have focused on 7Li NMR spectroscopy to follow the lithiation and degradation processes in the solid electrodes of lithium-ion batteries. However, the large shifts and broadenings of the NMR spectra, which result from the redox-active paramagnetic ions (Ni2/3+, Co4+, Mn3/4+) or from the metallicity of the electrodes [3], complicate operando NMR spectra acquisition and interpretation for full batteries.Herein, we demonstrate that the 1H operando NMR signal of the liquid electrolyte solvent can be used to spy on the positive electrode evolution while benefitting from the high sensitivity of 1H liquid-state NMR compared to 7Li NMR. So far, operando NMR using the liquid electrolyte signal was mainly exploited to follow electrolyte decomposition [4] or to image indirectly dendrite formation [5]. Contrary to the lithium or sodium atoms composing the electrodes, hydrogen atoms in the electrolyte solvent are not a direct probe of the state of charge of the electrode. We demonstrate that the 1H NMR signal of the electrolyte molecules in the battery is, however, highly sensitive to the magnetic susceptibility (and therefore the redox state) of the neighboring particles of positive electrode active material.The state-of-charge (SOC) of the positive electrodes in the charging battery can be tracked indirectly through distortion in the spectrum of the dimethyl carbonate (DMC) solvent near the positive electrode. The effect of the other battery components such as current collectors, separators, or even negative electrodes is shown to be negligible compared to the perturbations induced by the positive electrode. We define specific descriptors to track the changes in the distorted 1H NMR spectrum of the battery and we correlate these changes with the state-of-charge of the positive electrode inside the battery as it is charged and discharged. This approach will enable measuring, operando, the redox state of positive electrodes in batteries, even when their 7Li signals cannot be detected by NMR. Exact knowledge of the redox state will contribute to a better exploitation of the electrochemical curves in full batteries.[1] Bagheri, K.; Deschamps, M.; Salager, E. Nuclear Magnetic Resonance for Interfaces in Rechargeable Batteries. Current Opinion in Colloid & Interface Science 2023, 64, 101675. https://doi.org/10.1016/j.cocis.2022.101675.[2] Liu, X.; Liang, Z.; Xiang, Y.; Lin, M.; Li, Q.; Liu, Z.; Zhong, G.; Fu, R.; Yang, Y. Solid‐State NMR and MRI Spectroscopy for Li/Na Batteries: Materials, Interface, and in Situ Characterization. Advanced Materials 2021, 33 (50), 2005878. https://doi.org/10.1002/adma.202005878.[3] Grey, C. P.; Dupré, N. NMR Studies of Cathode Materials for Lithium-Ion Rechargeable Batteries. Chemical Reviews 2004, 104 (10), 4493–4512. https://doi.org/10.1021/cr020734p.[4] Wiemers-Meyer, S.; Winter, M.; Nowak, S. NMR as a Powerful Tool to Study Lithium Ion Battery Electrolytes. Annual Reports on NMR Spectroscopy 2019, 121–162. https://doi.org/10.1016/bs.arnmr.2018.12.003.[5] Ilott, A. J.; Mohammadi, M.; Chang, H. J.; Grey, C. P.; Jerschow, A. Real-Time 3D Imaging of Microstructure Growth in Battery Cells Using Indirect MRI. Proceedings of the National Academy of Sciences 2016, 113 (39), 10779–10784. https://doi.org/10.1073/pnas.1607903113.

A reliable external calibration method for reaction monitoring with benchtop NMR.

Nuclear magnetic resonance (NMR) spectroscopy is a powerful analytical technique with the ability to acquire both quantitative and structurally insightful data for multiple components in a test sample. This makes NMR spectroscopy a desirable tool to understand, monitor, and optimize chemical transformations. While quantitative NMR (qNMR) approaches relying on internal standards are well-established, using an absolute external calibration scheme is beneficial for reaction monitoring as resonance overlap complications from an added reference material to the sample can be avoided. Particularly, this type of qNMR technique is of interest with benchtop NMR spectrometers as the likelihood of resonance overlap is only enhanced with the lower magnetic field strengths of the used permanent magnets. The included study describes a simple yet robust methodology to determine concentration conversion factors for NMR systems using single- and multi-analyte linear regression models. This approach is leveraged to investigate a pharmaceutically relevant amide coupling batch reaction. An on-line stopped-flow (i.e., interrupted-flow or paused-flow) benchtop NMR system was used to monitor both the 1,1'-carbonyldiimidazole (CDI) promoted acid activation and the amide coupling. The results highlight how quantitative measurements in benchtop NMR systems can provide valuable information and enable analysts to make decisions in real time.

Spatial evolution of pore and fracture structures in coal under unloading confining pressure: A stratified nuclear magnetic resonance approach

The inherent spatial complexity and strong heterogeneity characterise the pore and fracture structures (PFS) in coal. Understanding the spatial evolution of PFS in coal under unloading confining pressure is crucial for ensuring the safety of coal mining operations. In this study, the stratified nuclear magnetic resonance (NMR) technique and a triaxial mechanical loading system were combined to realise real-time observation of the spatial evolution of PFS in coal during the unloading confining pressure process. A conceptual model depicting the spatial evolution of PFS in coal under unloading confining pressure was formulated. Based on our experimental findings, the mesoscopic mechanical behaviour of coal subjected to unloading confining pressure was simulated using PFC 2D. Our research reveals that throughout the unloading confining pressure process, the PFS within coal samples simultaneously exhibits characteristics of both compacted and fractured states, with mutual transformation occurring in the adsorption and seepage pores. A reduction in confining pressure results in a notable escalation of observed damage within the coal samples and intensified development of PFS. Furthermore, our numerical simulation results closely align with NMR test results, providing additional validation to our findings.

Comprehensive NMR Investigation of Imidazolium-Based Ionic Liquids [BMIM][OSU] and [BMIM][Cl] Impact on Binding and Dynamics of the Anticancer Drug Doxorubicin Hydrochloride.

For the design of an efficient drug delivery system utilizing an ionic liquid (IL) as a carrier, it is prudent to gain molecular/atomistic level insights of a drug with IL in terms of binding and dynamics. In this scenario, the influence of anionic counterpart of imidazolium-based ILs, namely, 1-butyl-3-methyl-imidazolium octyl sulfate [BMIM][OSU] and 1-butyl-3-methyl-imidazolium chloride [BMIM][Cl] in their submicellar region ([IL] = 20 mM) on the model water-soluble anticancer drug doxorubicin hydrochloride (DOX) was probed by employing an arsenal of nuclear magnetic resonance (NMR) approaches. The salient feature of the present study includes the significant interaction of DOX with [BMIM][OSU], whereas the lack of such an interaction with [BMIM][Cl] is gauged by 1H NMR translation self-diffusometry and is further corroborated by 13C chemical shift perturbation. The two-step model was utilized to estimate the bound fraction (pb) and equivalent partition coefficient (K) of DOX with [BMIM][OSU]. A combination of selective and nonselective spin-lattice relaxation rates (R1SEL and R1NS, respectively) enables to gauze the significant interaction of DOX with [BMIM][OSU] over [BMIM][Cl]. Furthermore, 1D transient and truncated driven nuclear Overhauser enhancement (NOE) data analyses in the initial rate limit permits the evaluation of the cross-relaxation efficacy of DOX with the investigated ILs. An Arrhenius-type temperature dependence of the drug's self-diffusion was observed for DOX, DOX-[BMIM][OSU], and DOX-[BMIM][Cl] aqueous mixtures and the corresponding activation energies were evaluated.

Magnetic Resonance-Based Analytical Tools to Study Polyvinylpyrrolidone-Hydroxyapatite Composites.

The synthesis of biocompatible and bioresorbable composite materials, such as a "polymer matrix-mineral constituent," stimulating the natural growth of living tissues and the restoration of damaged parts of the body, is one of the challenging problems in regenerative medicine and materials science. Composite films of bioresorbable polymer of polyvinylpyrrolidone (PVP) and hydroxyapatite (HA) were obtained. HA was synthesized in situ in the polymer solution. We applied electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) approaches to study the composite films' properties. The application of EPR in two frequency ranges allowed us to derive spectroscopic parameters of the nitrogen-based light and radiation-induced paramagnetic centers in HA, PVP and PVP-HA with high accuracy. It was shown that PVP did not significantly affect the EPR spectral and relaxation parameters of the radiation-induced paramagnetic centers in HA, while light-induced centers were detected only in PVP. Magic angle spinning (MAS) 1H NMR showed the presence of two signals at 4.7 ppm and -2.15 ppm, attributed to "free" water and hydroxyl groups, while the single line was attributed to 31P. NMR relaxation measurements for 1H and 31P showed that the relaxation decays were multicomponent processes that can be described by three components of the transverse relaxation times. The obtained results demonstrated that the applied magnetic resonance methods can be used for the quality control of PVP-HA composites and, potentially, for the development of analytical tools to follow the processes of sample treatment, resorption, and degradation.

The effect of tube quality on externally calibrated quantitative nuclear magnetic resonance analysis: How bad can it be?

Externally calibrated quantitative nuclear magnetic resonance (NMR) approaches offer practical means to simultaneously evaluate chemical identity and content without the addition of calibrants to the test sample. Despite continuous advances in external calibration over the last few decades, adoption of these approaches has been slower than expected. Variations in NMR tube geometry are a commonly overlooked factor that can have a substantial effect on externally calibrated quantitation methods. In this report, we investigate the extent to which tube-to-tube volume variability can affect quantitative NMR outcomes. The results highlight the importance of considering tube quality during the development stages of externally calibrated quantitative methods. In addition, we propose a simple, yet effective volume correction strategy using the residual protonated solvent signal that, based on experiments with mixed NMR tubes of varying quality, alleviates the effect of tube-to-tube variability.