Broadband finite-pulse radio-frequency-driven recoupling (fp-RFDR) with (XY8)41 super-cycling for homo-nuclear correlations in very high magnetic fields at fast and ultra-fast MAS frequencies

Shen, Ming; Hu, Bingwen; Lafon, Olivier; Trébosc, Julien; Chen, Qun; Amoureux, Jean‐Paul

doi:10.1016/j.jmr.2012.07.013

Cited by 41 publications

(37 citation statements)

References 78 publications

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“…Typical distances probed by fp-RFDR for non-quadrupolar nuclei (spin-1/2) are < 1 nm, and we expect similar sub-nanometer length scales to be probed between the weakly quadrupolar 7 Li nuclei (spin-3/2). For example, Shen et al 24 demonstrate both theoretically and experimentally that fp-RFDR with a (XY-8) 4 1 phase super-cycle can facilitate either direct or relayed dipolar transfer of magnetization among 13 C nuclei separated by distances of <5 Å. Note that in LiVPO 4 F crystal structure, the next-nearest lithium neighbor from a given lithium ion is 3.8 Å away, while within a 5 Å coordination sphere, 4 other lithium ions are expected.…”

Section: Resultsmentioning

confidence: 99%

“…23 7 Li T 1 and T 2 NMR relaxation measurements were acquired using the saturation recovery and Hahn spin-echo pulse sequences, respectively. 1 super cycle, 24 where the ratio of the π pulse duration (2.5 us) to the rotor period (15.625 µs) was 0.16. All 2D NMR experiments were conducted using a rotor-synchronized parametric time increment t 1 of 15.625 µs for a total acquisition time of 3.125 ms in the indirect dimension.…”

Section: Methodsmentioning

confidence: 99%

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Revealing Defects in Crystalline Lithium-Ion Battery Electrodes by Solid-State NMR: Applications to LiVPO₄F

et al. 2015

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Identifying and characterizing defects in crystalline solids is a challenging problem, particularly for lithium-ion intercalation materials, which often exhibit multiple stable oxidation and spin states as well as local ordering of lithium and charges. Here, we reveal the existence of characteristic lithium defect environments in the crystalline lithium-ion battery electrode LiVPO 4 F and establish the relative sub-nanometer-scale proximities between them. Well-crystallized LiVPO 4 F samples were synthesized with the expected tavorite-like structure, as established by X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM) measurements. Solidstate 7 Li nuclear magnetic resonance (NMR) spectra reveal unexpected paramagnetic 7 Li environments that can account for up to 20% of the total lithium content. Multi-dimensional and site-selective solid-state 7 Li NMR experiments using finite-pulse radio-frequency-driven recoupling (fp-RFDR) establish unambiguously that the unexpected lithium environments are associated with defects within the LiVPO 4 F crystal structure, revealing the existence of dipole-dipole-coupled defect pairs. The lithium defects exhibit local electronic environments that are distinct from lithium ions in the crystallographic LiVPO 4 F site, which result from altered oxidation and/or spin states of nearby paramagnetic vanadium atoms. The results provide a general strategy for identifying and characterizing lithium defect environments in crystalline solids, including paramagnetic materials with short 7

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Revealing Defects in Crystalline Lithium-Ion Battery Electrodes by Solid-State NMR: Applications to LiVPO₄F

et al. 2015

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“…In addition to the spinning speed and the 180° pulse width, the dipolar recoupling efficiency of fp-RFDR depends on chemical shift offset, RF field inhomogeneity, and the interference of chemical shift anisotropy (CSA) and heteronuclear dipolar couplings that are especially significant for low-γ (for example, 13 C) nuclei [41]. XY-based phase cycling for the 180° pulse has been shown to overcome these limitations of the fp-RFDR sequence [41, 47]. A recent study demonstrated that, for 2D 13 C/ 13 C chemical shift correlation experiments, the best performance of fp-RFDR under fast MAS could be achieved by a super phase cycle XY8 1 4 [47].…”

Section: Introductionmentioning

confidence: 99%

Phase cycling schemes for finite-pulse-RFDR MAS solid state NMR experiments

Zhang

Nishiyama

Sun

et al. 2015

Journal of Magnetic Resonance

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The finite-pulse radio frequency driven dipolar recoupling (fp-RFDR) pulse sequence is used in 2D homonuclear chemical shift correlation experiments under magic angle spinning (MAS). A recent study demonstrated the advantages of using a short phase cycle, XY4, and its super-cycle, XY414, for the fp-RFDR pulse sequence employed in 2D 1H/1H single-quantum/single-quantum correlation experiments under ultrafast MAS conditions. In this study, we report a comprehensive analysis on the dipolar recoupling efficiencies of XY4, XY412, XY413, XY414, and XY814 phase cycles under different spinning speeds ranging from 10 to 100 kHz. The theoretical calculations reveal the presence of second-order terms (T10T2,±2, T1,±1T2,±1, etc.) in the recoupled homonuclear dipolar coupling Hamiltonian only when the basic XY4 phase cycle is utilized, making it advantageous for proton-proton magnetization transfer under ultrafast MAS conditions. It is also found that the recoupling efficiency of fp-RFDR is quite dependent on the duty factor (τ180/τR) as well as on the strength of homonuclear dipolar couplings. The rate of longitudinal magnetization transfer increases linearly with the duty factor of fp-RFDR for all the XY-based phase cycles investigated in this study. Examination of the performances of different phase cycles against chemical shift offset and RF field in homogeneity effects revealed that XY414 is the most tolerant phase cycle, while the shortest phase cycle XY4 suppressed the RF field inhomogeneity effects most efficiently under slow spinning speeds. Our results suggest that the difference in the fp-RFDR recoupling efficiencies decreases with the increasing MAS speed, while ultrafast (>60 kHz) spinning speed is advantageous as it recouples a large amount of homonuclear dipolar couplings and therefore enable fast magnetization exchange. The effects of higher-order terms and cross terms between various interactions in the effective Hamiltonian of fp-RFDR are also analyzed using numerical simulations for various phase cycles. Results obtained via numerical simulations are in excellent agreement with ultrafast MAS experimental results from the powder samples of glycine and L-alanine.

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“…Previous studies have demonstrated the effectiveness of XY-based phase cycling to overcome the limitations of fp-RFDR. Among various phase cycling schemes reported in the literature (Figure 1), a recent study reported the best performance of fp-RFDR using XY8 1 4 phase cycling[12]. The idea behind XY-based phase cycling for the fp-RFDR pulse sequence can be explained by the symmetry based sequence [11, 13] and its super-cycle.…”

Section: Introductionmentioning

confidence: 99%

Finite-pulse radio frequency driven recoupling with phase cycling for 2D 1H/1H correlation at ultrafast MAS frequencies

Nishiyama¹,

Zhang²,

Ramamoorthy³

2014

Journal of Magnetic Resonance

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The first-order recoupling sequence radio frequency driven dipolar recoupling (RFDR) is commonly used in single-quantum/single-quantum homonuclear correlation 2D experiments under magic angle spinning (MAS) to determine homonuclear proximities. From previously reported analysis of the use of XY-based super-cycling schemes to enhance the efficiency of the finite-pulse-RFDR (fp-RFDR) pulse sequence, XY814 phase cycling was found to provide the optimum performance for 2D correlation experiments on low-γ nuclei. In this study, we analyze the efficiency of different phase cycling schemes for proton-based fp-RFDR experiments. We demonstrate the advantages of using a short phase cycle, XY4, and its super-cycle XY414 that only recouples the zero-quantum homonuclear dipolar coupling, for the fp-RFDR sequence in 2D 1H/1H correlation experiments at ultrafast MAS frequencies. The dipolar recoupling efficiencies of XY4, XY414 and XY814 phase cycling schemes are compared based on results obtained from 2D 1H/1H correlation experiments, utilizing the fp-RFDR pulse sequence, on powder samples of U-13C,15N-L-alanine, N-acetyl-15N-L-valyl-15N-L-leucine, and glycine. Experimental results and spin dynamics simulations show that XY414 performs the best when a high RF power is used for the 180° pulse, whereas XY4 renders the best performance when a low RF power is used. The effects of RF field inhomogeneity and chemical shift offsets are also examined. Overall, our results suggest that a combination of fp-RFDR-XY414 employed in the recycle delay with a large RF-field to decrease the recycle delay, and fp-RFDR-XY4 in the mixing period with a moderate RF-field, is a robust and efficient method for 2D single-quantum/single-quantum 1H/1H correlation experiments at ultrafast MAS frequencies.

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Broadband finite-pulse radio-frequency-driven recoupling (fp-RFDR) with (XY8)41 super-cycling for homo-nuclear correlations in very high magnetic fields at fast and ultra-fast MAS frequencies

Cited by 41 publications

References 78 publications

Revealing Defects in Crystalline Lithium-Ion Battery Electrodes by Solid-State NMR: Applications to LiVPO₄F

Revealing Defects in Crystalline Lithium-Ion Battery Electrodes by Solid-State NMR: Applications to LiVPO₄F

Phase cycling schemes for finite-pulse-RFDR MAS solid state NMR experiments

Finite-pulse radio frequency driven recoupling with phase cycling for 2D 1H/1H correlation at ultrafast MAS frequencies

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Broadband finite-pulse radio-frequency-driven recoupling (fp-RFDR) with (XY8)41 super-cycling for homo-nuclear correlations in very high magnetic fields at fast and ultra-fast MAS frequencies

Cited by 41 publications

References 78 publications

Revealing Defects in Crystalline Lithium-Ion Battery Electrodes by Solid-State NMR: Applications to LiVPO4F

Revealing Defects in Crystalline Lithium-Ion Battery Electrodes by Solid-State NMR: Applications to LiVPO4F

Phase cycling schemes for finite-pulse-RFDR MAS solid state NMR experiments

Finite-pulse radio frequency driven recoupling with phase cycling for 2D 1H/1H correlation at ultrafast MAS frequencies

Contact Info

Product

Resources

About

Revealing Defects in Crystalline Lithium-Ion Battery Electrodes by Solid-State NMR: Applications to LiVPO₄F

Revealing Defects in Crystalline Lithium-Ion Battery Electrodes by Solid-State NMR: Applications to LiVPO₄F