Magnetic resonance (Gottingen, Germany)最新文献

{"title":"Increased sensitivity in electron-nuclear double resonance spectroscopy with chirped radiofrequency pulses.","authors":"Julian Stropp, Nino Wili, Niels C Nielsen, Daniel Klose","doi":"10.5194/mr-6-33-2025","DOIUrl":"10.5194/mr-6-33-2025","url":null,"abstract":"<p><p>Electron-nuclear double resonance (ENDOR) spectroscopy is an EPR technique to detect the nuclear frequency spectra of hyperfine coupled nuclei close to paramagnetic centers, which have interactions that are not resolved in continuous wave EPR spectra and may be fast relaxing on the timescale of NMR. For the common case of non-crystalline solids, such as powders or frozen solutions of transition metal complexes, the anisotropy of the hyperfine and nuclear quadrupole interactions renders ENDOR lines often several megahertz (MHz) broad, thus diminishing intensity. With commonly used ENDOR pulse sequences, only a small fraction of the NMR/ENDOR line is excited with a typical radiofrequency (RF) pulse length of several tens of microseconds ( <math><mrow><mi>µ</mi></mrow> </math> s), and this limits the sensitivity in conventional ENDOR experiments. In this work, we show the benefit of chirped RF excitation in frequency-domain ENDOR as a simple yet effective way to significantly improve sensitivity. We demonstrate on a frozen solution of Cu(II)-tetraphenylporphyrin that the intensity of broad copper and nitrogen ENDOR lines increases up to 9-fold compared to single-frequency RF excitation, thus making the detection of metal ENDOR spectra more feasible. The tunable bandwidth of the chirp RF pulses allows the operator to optimize for sensitivity and choose a tradeoff with resolution, opening up options previously inaccessible in ENDOR spectroscopy. Also, chirp pulses help to reduce RF amplifier overtones, since lower RF powers suffice to achieve intensities matching conventional ENDOR. In 2D triple resonance experiments (TRIPLE), the signal increase exceeds 10 times for some lines, thus making chirped 2D TRIPLE experiments feasible even for broad peaks in manageable acquisition times.</p>","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":"6 1","pages":"33-42"},"PeriodicalIF":0.0,"publicationDate":"2025-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12247087/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144628061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Electron-spin decoherence in trityl radicals in the absence and presence of microwave irradiation.","authors":"Gunnar Jeschke, Nino Wili, Yufei Wu, Sergei Kuzin, Hugo Karas, Henrik Hintz, Adelheid Godt","doi":"10.5194/mr-6-15-2025","DOIUrl":"10.5194/mr-6-15-2025","url":null,"abstract":"<p><p>Trityl radicals feature prominently as polarizing agents in solid-state dynamic nuclear polarization experiments and as spin labels in distance distribution measurements by pulsed dipolar EPR spectroscopy techniques. Electron-spin coherence lifetime is a main determinant of performance in these applications. We show that protons in these radicals contribute substantially to decoherence, although the radicals were designed with the aim of reducing proton hyperfine interaction. By spin dynamics simulations, we can trace back the nearly complete Hahn echo decay for a Finland trityl radical variant within 7 <math><mrow><mi>µ</mi></mrow> </math> s to the contribution from tunnelling of the 36 methyl protons in the radical core. This contribution, as well as the contribution of methylene protons in OX063 and OX071 trityl radicals, to Hahn echo decay can be predicted rather well by the previously introduced analytical pair product approximation. In contrast, predicting decoherence of electron spins dressed by a microwave field proves to be a hard problem where correlations between more than two protons contribute substantially. Cluster correlation expansion (CCE) becomes borderline numerically unstable already at order 3 at times comparable to the decoherence time <math> <mrow><msub><mi>T</mi> <mrow><mn>2</mn> <mi>ρ</mi></mrow> </msub> </mrow> </math> and cannot be applied at order 4. We introduce partial CCE that alleviates this problem and reduces computational effort at the expense of treating only part of the correlations at a particular order. Nevertheless, dressed-spin decoherence simulations for systems with more than 100 protons remain out of reach, whereas they provide only semi-quantitative predictions for 24 to 48 protons. Our experimental and simulation results indicate that solid-state magnetic resonance experiments with trityl radicals will profit from perdeuteration of the compounds.</p>","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":"6 1","pages":"15-32"},"PeriodicalIF":0.0,"publicationDate":"2025-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12247090/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144628059","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analytical treatment of proton double-quantum NMR intensity buildup: multi-spin couplings and the flip-flop term.","authors":"Nail Fatkullin, Ivan Brekotkin, Kay Saalwächter","doi":"10.5194/mr-6-1-2025","DOIUrl":"10.5194/mr-6-1-2025","url":null,"abstract":"<p><p>A modified Anderson-Weiss approximation for describing double-quantum (DQ) NMR experiments in systems with many <math><mi>I</mi></math> <math><mo>=</mo></math> <math><mrow><mn>1</mn> <mo>/</mo> <mn>2</mn></mrow> </math> spins is proposed, taking inter-spin flip-flop processes into special consideration. In this way, an analytical result is derived for multi-spin systems for the first time. It is shown that in the initial stages of DQ intensity buildup, the probability of flip-flop processes in DQ experiments is half as large as in analogous Hahn echo or free induction decay experiments. Their influence on the experimentally observed DQ NMR signal becomes dominant at times <math><mrow><mi>t</mi> <mo>></mo> <msup> <mfenced><mrow><mn>9</mn> <mo>/</mo> <mn>2</mn></mrow> </mfenced> <mrow><mn>1</mn> <mo>/</mo> <mn>2</mn></mrow> </msup> <msubsup><mi>T</mi> <mn>2</mn> <mi>eff</mi></msubsup> <mo>≈</mo> <mn>2.12</mn> <msubsup><mi>T</mi> <mn>2</mn> <mi>eff</mi></msubsup> </mrow> </math> , where <math> <mrow><msubsup><mi>T</mi> <mn>2</mn> <mi>eff</mi></msubsup> </mrow> </math> is the effective spin-spin relaxation time measured by the Hahn echo. Calculations and a comparison with spin dynamics simulations of small spin systems of up to eight spins reveal a satisfactory agreement.</p>","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":"6 1","pages":"1-14"},"PeriodicalIF":0.0,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12558027/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145395929","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Workflow for systematic design of electrochemical in operando NMR cells by matching <i>B</i> ₀ and <i>B</i> ₁ field simulations with experiments.","authors":"Michael Schatz, Matthias Streun, Sven Jovanovic, Rüdiger-A Eichel, Josef Granwehr","doi":"10.5194/mr-5-167-2024","DOIUrl":"10.5194/mr-5-167-2024","url":null,"abstract":"<p><p>Combining electrochemistry (EC) and nuclear magnetic resonance (NMR) techniques has evolved from a challenging concept to an adaptable and versatile method for battery and electrolysis research. Continuous advancements in NMR hardware have fostered improved homogeneity of the static magnetic field, <math> <mrow><msub><mi>B</mi> <mn>0</mn></msub> </mrow> </math> , and the radio frequency field, <math> <mrow><msub><mi>B</mi> <mn>1</mn></msub> </mrow> </math> , yet fundamental challenges caused by introducing essential conductive components into the NMR sensitive volume remain. Cell designs in EC-NMR have largely been improved empirically, at times supported by magnetic field simulations. To propel systematic improvements of cell concepts, a workflow for a qualitative and semi-quantitative description of both <math> <mrow><msub><mi>B</mi> <mn>0</mn></msub> </mrow> </math> and <math> <mrow><msub><mi>B</mi> <mn>1</mn></msub> </mrow> </math> distortions is provided in this study. Three-dimensional finite element method (FEM) simulations of both <math> <mrow><msub><mi>B</mi> <mn>0</mn></msub> </mrow> </math> and <math> <mrow><msub><mi>B</mi> <mn>1</mn></msub> </mrow> </math> fields were employed to investigate cell structures with electrodes oriented perpendicular to <math> <mrow><msub><mi>B</mi> <mn>0</mn></msub> </mrow> </math> , which allow realistic EC-NMR measurements for battery and electrolysis applications. Particular attention is paid to field distributions in the immediate vicinity of electrodes, which is of prime interest for electrochemical processes. Using a cell with a small void outside the electrochemical active region, the relevance of design details and bubble formation is demonstrated. Moreover, <math> <mrow><msub><mi>B</mi> <mn>1</mn></msub> </mrow> </math> amplifications in coin cells provide an explanation for unexpectedly high sensitivity in previous EC-NMR studies, implying the potential for selective excitation of spins close to electrode surfaces. The correlation of this amplification effect with coin geometry is described by empirical expressions. The simulations were validated experimentally utilising frequency-encoded ¹H profile imaging and chemical shift imaging of ¹H, ¹³C, and ²³Na resonances of <math> <mrow><msub><mi>NaHCO</mi> <mn>3</mn></msub> </mrow> </math> electrolyte. Finally, the theoretical and experimental results are distilled into design guidelines for EC-NMR cells.</p>","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":"5 2","pages":"167-180"},"PeriodicalIF":0.0,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12178131/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144334621","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Low-power WALTZ decoupling under magic-angle spinning NMR.","authors":"Luzian Thomas, Matthias Ernst","doi":"10.5194/mr-5-153-2024","DOIUrl":"10.5194/mr-5-153-2024","url":null,"abstract":"<p><p>Heteronuclear low-power decoupling using the solution-state wideband alternating-phase low-power technique for zero-residual splitting (WALTZ) sequences has become quite popular in solid-state protein NMR and seems to work well. However, there are no systematic studies that characterize these sequences under magic-angle spinning (MAS) and give recommendations on which parameter should be used. We have studied in detail the use of WALTZ-16 and WALTZ-64 as low-power decoupling sequences under 100 kHz MAS by characterizing the resonance conditions analytically using numerical simulations and experiments on model substances. The recoupling heteronuclear resonance conditions between the modulation frequency of the sequences and the MAS frequency is the most important feature. Pulse lengths corresponding to areas with vanishing first-order heteronuclear recoupling are good candidates for efficient decoupling. We have characterized two such conditions which can be defined using the nutation frequency of the radio frequency (RF) field ( <math> <mrow><msub><mi>ν</mi> <mn>1</mn></msub> </mrow> </math> ) and the spinning frequency ( <math> <mrow><msub><mi>ν</mi> <mi>r</mi></msub> </mrow> </math> ) by <math> <mrow><msub><mi>ν</mi> <mn>1</mn></msub> <mo>=</mo> <msub><mi>ν</mi> <mi>r</mi></msub> <mo>/</mo> <mn>10</mn></mrow> </math> and <math> <mrow><msub><mi>ν</mi> <mn>1</mn></msub> <mo>=</mo> <mn>2</mn> <msub><mi>ν</mi> <mi>r</mi></msub> <mo>/</mo> <mn>5</mn></mrow> </math> , which both lead to narrow lines and are stable against RF-field variations and chemical-shift offsets. More such conditions might exist but were not investigated here.</p>","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":"5 2","pages":"153-166"},"PeriodicalIF":0.0,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12178133/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144334619","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Design and performance of an oversized-sample 35 GHz EPR resonator with an elevated <i>Q</i> value.","authors":"Jörg Wolfgang Anselm Fischer, Julian Stropp, René Tschaggelar, Oliver Oberhänsli, Nicholas Alaniva, Mariko Inoue, Kazushi Mashima, Alexander Benjamin Barnes, Gunnar Jeschke, Daniel Klose","doi":"10.5194/mr-5-143-2024","DOIUrl":"10.5194/mr-5-143-2024","url":null,"abstract":"<p><p>Continuous-wave electron paramagnetic resonance (EPR) spectroscopy at 35 GHz is an essential cornerstone in multi-frequency EPR studies and is crucial for differentiating multiple species in complex systems due to the improved <math><mi>g</mi></math> -tensor resolution compared to lower microwave frequencies. Especially for unstable and highly sensitive paramagnetic centers, the reliability of the measurements can be improved upon through the use of a single sample for EPR experiments at all frequencies. Besides the advantages, the lack of common availability of oversized-sample resonators at 35 GHz often limits scientists to lower frequencies or smaller sample geometries, and the latter may be non-trivial for sensitive materials. In this work, we present the design and performance of an oversized-sample 35 GHz EPR resonator with a high loaded <math><mi>Q</mi></math>  value, <math> <mrow><msub><mi>Q</mi> <mi>L</mi></msub> </mrow> </math> , of up to 2550, well-suited for continuous-wave EPR and pulsed single-microwave-frequency experiments. The design is driven by electromagnetic field simulations, and the microwave characteristics of manufactured prototypes were found to be in agreement with the predictions. The resonator is based on a cylindrical cavity with a TE <math><msub><mi></mi> <mn>011</mn></msub> </math> mode, allowing for 3 mm sample access. The design targets that we met include high sensitivity, robustness, and ease of manufacturing and maintenance. The resonator is compatible with commercial EPR spectrometers and with helium flow, as well as with cryogen-free cryostats, allowing for measurements at temperatures down to 1.8 K. To highlight the general applicability, the resonator was tested on metal centers, as well as on organic radicals featuring extremely narrow lines.</p>","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":"5 2","pages":"143-152"},"PeriodicalIF":0.0,"publicationDate":"2024-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12178130/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144334618","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"PRESERVE: adding variable flip-angle excitation to transverse relaxation-optimized NMR spectroscopy.","authors":"Bernhard Brutscher","doi":"10.5194/mr-5-131-2024","DOIUrl":"10.5194/mr-5-131-2024","url":null,"abstract":"<p><p>We introduce the \"Polarization Restoring Excitation SEquence foR Versatile Experiments\" (PRESERVE) pulse sequence element, allowing variable flip-angle adjustment in 2D <math><msup><mi></mi> <mn>1</mn></msup> </math> H- <math><msup><mi></mi> <mn>15</mn></msup> </math> N and <math><msup><mi></mi> <mn>1</mn></msup> </math> H- <math><msup><mi></mi> <mn>13</mn></msup> </math> C transverse-relaxation-optimized-spectroscopy (TROSY)-type correlation experiments. PRESERVE-TROSY exploits a remarkable array of up to nine orthogonal coherence-transfer pathways, showcasing the remarkable potential of spin manipulations achievable through the design and optimization of nuclear magnetic resonance (NMR) pulse sequences.</p>","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":"5 2","pages":"131-142"},"PeriodicalIF":0.0,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12178132/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144334620","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"¹H-enhanced ¹⁰³Rh NMR spectroscopy and relaxometry of ¹⁰³Rh(acac)₃ in solution.","authors":"Harry Harbor-Collins, Mohamed Sabba, Markus Leutzsch, Malcolm H Levitt","doi":"10.5194/mr-5-121-2024","DOIUrl":"10.5194/mr-5-121-2024","url":null,"abstract":"<p><p>Recently developed polarisation transfer techniques are applied to the <math> <mrow><msup><mi></mi> <mn>103</mn></msup> <mi>Rh</mi></mrow> </math> nuclear magnetic resonance (NMR) of the <math> <mrow><msup><mi></mi> <mn>103</mn></msup> <mi>Rh</mi> <mo>(</mo> <mi>acac</mi> <msub><mo>)</mo> <mn>3</mn></msub> </mrow> </math> coordination complex in solution. Four-bond <math> <mrow><msup><mi></mi> <mn>1</mn></msup> <mi>H</mi></mrow> </math> - <math> <mrow><msup><mi></mi> <mn>103</mn></msup> <mi>Rh</mi></mrow> </math> <math><mi>J</mi></math>  couplings of around 0.39 <math><mrow><mi>Hz</mi></mrow> </math> are exploited to enhance the <math> <mrow><msup><mi></mi> <mn>103</mn></msup> <mi>Rh</mi></mrow> </math> NMR signal and to estimate the <math> <mrow><msup><mi></mi> <mn>103</mn></msup> <mi>Rh</mi></mrow> </math> <math> <mrow><msub><mi>T</mi> <mn>1</mn></msub> </mrow> </math>  and <math> <mrow><msub><mi>T</mi> <mn>2</mn></msub> </mrow> </math>  relaxation times as a function of field and temperature. The <math> <mrow><msup><mi></mi> <mn>103</mn></msup> <mi>Rh</mi></mrow> </math> longitudinal <math> <mrow><msub><mi>T</mi> <mn>1</mn></msub> </mrow> </math>  relaxation in <math> <mrow><msup><mi></mi> <mn>103</mn></msup> <mi>Rh</mi> <mo>(</mo> <mi>acac</mi> <msub><mo>)</mo> <mn>3</mn></msub> </mrow> </math> is shown to be dominated by the spin-rotation mechanism, with an additional field-dependent contribution from the <math> <mrow><msup><mi></mi> <mn>103</mn></msup> <mi>Rh</mi></mrow> </math> chemical shift anisotropy.</p>","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":"5 2","pages":"121-129"},"PeriodicalIF":0.0,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12163919/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144303850","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analysis of chi angle distributions in free amino acids via multiplet fitting of proton scalar couplings.","authors":"Nabiha R Syed, Nafisa B Masud, Colin A Smith","doi":"10.5194/mr-5-103-2024","DOIUrl":"10.5194/mr-5-103-2024","url":null,"abstract":"<p><p>Scalar couplings are a fundamental aspect of nuclear magnetic resonance (NMR) experiments and provide rich information about electron-mediated interactions between nuclei. ³ <math><mrow><mi>J</mi></mrow> </math> couplings are particularly useful for determining molecular structure through the Karplus relationship, a mathematical formula used for calculating ³ <math><mrow><mi>J</mi></mrow> </math> coupling constants from dihedral angles. In small molecules, scalar couplings are often determined through analysis of one-dimensional proton spectra. Larger proteins have typically required specialized multidimensional pulse programs designed to overcome spectral crowding and multiplet complexity. Here, we present a generalized framework for fitting scalar couplings with arbitrarily complex multiplet patterns using a weak-coupling model. The method is implemented in FitNMR and applicable to one-dimensional, two-dimensional, and three-dimensional NMR spectra. To gain insight into the proton-proton coupling patterns present in protein side chains, we analyze a set of free amino acid one-dimensional spectra. We show that the weak-coupling assumption is largely sufficient for fitting the majority of resonances, although there are notable exceptions. To enable structural interpretation of all couplings, we extend generalized and self-consistent Karplus equation parameterizations to all <math><mi>χ</mi></math> angles. An enhanced model of side-chain motion incorporating rotamer statistics from the Protein Data Bank (PDB) is developed. Even without stereospecific assignments of the beta hydrogens, we find that two couplings are sufficient to exclude a single-rotamer model for all amino acids except proline. While most free amino acids show rotameric populations consistent with crystal structure statistics, beta-branched valine and isoleucine deviate substantially.</p>","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":"5 2","pages":"103-120"},"PeriodicalIF":0.0,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11570886/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142678010","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Second-harmonic electron paramagnetic resonance spectroscopy and imaging reveal metallic lithium depositions in Li-ion batteries.","authors":"Charles-E Dutoit, Hania Ahouari, Quentin Denoyelle, Simon Pondaven, Hervé Vezin","doi":"10.5194/mr-5-87-2024","DOIUrl":"10.5194/mr-5-87-2024","url":null,"abstract":"<p><p>We have investigated metallic lithium particle nucleation following lithiation and delithiation steps of the graphite electrode using X-band electron paramagnetic resonance (EPR). Metallic lithium aggregates like dendrites and/or filaments which are formed during electrochemical cycling on the graphite anode are complex structures which may lead to internal short-circuit and safety issues. Understanding and following, in real conditions, this nucleation process is necessary to improve the development of Li-ion batteries. The complexity to detect metallic lithium structures inside Li-ion batteries depends on the number of EPR lines and their linewidth. The presence of lithiated graphite phases affects the detection of micrometric Li-metal elements. Herein, we report a new approach using cw-EPR (continuous-wave EPR) spectroscopy and imaging, combining the first- and second-harmonic detection schemes to provide evidence for the metallic lithium aggregate nucleation in these negative electrodes. Although the first harmonic gives all the EPR signals present in the sample, it is found that the second-harmonic EPR signal is mainly sensitive to metallic lithium depositions.</p>","PeriodicalId":93333,"journal":{"name":"Magnetic resonance (Gottingen, Germany)","volume":"5 1","pages":"87-93"},"PeriodicalIF":0.0,"publicationDate":"2024-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12082685/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144096209","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}