Satellite-transition Magic Angle Spinning Research Articles

Half-integer-spin quadrupolar nuclei in magic-angle spinning paramagnetic NMR: The case of NaMnO2

A combination of solid-state NMR methods for the extraction of 23Na shift and quadrupolar parameters in the as-synthesized, structurally complex NaMnO2 Na-ion cathode material, under magic-angle spinning (MAS) is presented. We show that the integration of the Magic-Angle Turning experiment with Rotor-Assisted Population transfer (RAPT) can be used both to identify shifts and to extract a range of magnitudes for their quadrupolar couplings. We also demonstrate the applicability of the two-dimensional one pulse (TOP) based double-sheared Satellite Transition Magic-Angle Spinning (TOP-STMAS) showing how it can yield a spectrum with separated shift and second-order quadrupolar anisotropies, which in turn can be used to analyze a quadrupolar lineshape free of anisotropic bulk magnetic susceptibility (ABMS) induced shift dispersion and determine both isotropic shift and quadrupolar products. Combining all these experiments, the shift and quadrupolar parameters for all observed Na environments were extracted and yielded excellent agreement with the density functional theory (DFT) based models that were reported in previous literature. We expect these methods to open the door for new possibilities for solid-state NMR to probe half-integer quadrupolar nuclei in paramagnetic materials and other systems exhibiting large shift dispersion.

Separation of quadrupolar and paramagnetic shift interactions with TOP-STMAS/MQMAS in solid-state lighting phosphors.

A new approach for processing satellite-transition magic-angle spinning (STMAS) and multiple-quantum magic-angle spinning (MQMAS) data, based on the two-dimensional one-pulse (TOP) method, which separates the second-rank quadrupolar anisotropy and paramagnetic shift interactions via a double shearing transformation, is described. This method is particularly relevant in paramagnetic systems, where substantial inhomogeneous broadening may broaden the lineshapes. Furthermore, it possesses an advantage over the conventional processing of MQMAS and STMAS spectra because it overcomes the limitation on the spectral width in the indirect dimension imposed by rotor synchronization of the sampling interval. This method was applied experimentally to the Al solid-state nuclear magnetic resonance of a series of yttrium aluminum garnets (YAGs) doped with different lanthanide ions, from which the quadrupolar parameters of paramagnetically shifted and bulk unshifted sites were extracted. These parameters were then compared with density functional theory calculations, which permitted a better understanding of the local structure of Ln substituent ions in the YAG lattice.

71Ga-77Se connectivities and proximities in gallium selenide crystal and glass probed by solid-state NMR

We introduce two-dimensional (2D) 71Ga-77Se through-bond and through-space correlation experiments. Such correlations are achieved using (i) the J-mediated Refocused Insensitive Nuclei Enhanced by Polarization Transfer (J-RINEPT) method with 71Ga excitation and 77Se Carr-Purcell-Meiboon-Gill (CPMG) detection, as well as (ii) the J- or dipolar-mediated Hetero-nuclear Multiple-Quantum Correlation (J- or D-HMQC) schemes with 71Ga excitation and quadrupolar CPMG (QCPMG) detection. These methods are applied to the crystalline β-Ga2Se3 and the 0.2Ga2Se3-0.8GeSe2 glass. Such glass leads to a homogeneous and reproducible glass–ceramic, which is a good alternative to single-crystalline Ge and polycrystalline ZnSe materials for making lenses transparent in the IR range for thermal imaging applications. We show that 2D 71Ga-77Se correlation experiments allow resolving the 77Se signals of molecular units, which are not resolved in the 1D 77Se CPMG spectrum. Additionally, the build-up curves of the J-RINEPT and the J-HMQC experiments allow the estimate of the 71Ga-77Se J-couplings via one and three-bonds in the three-dimensional network of β-Ga2Se3. Furthermore, these build-up curves show that the one-bond 1J71Ga-77Se couplings in the 0.2Ga2Se3-0.8GeSe2 glass are similar to those measured for β-Ga2Se3. We also report 2D 71Ga Satellite Transition Magic-Angle Spinning (STMAS) spectrum of β-Ga2Se3 using QCPMG detection at high magnetic field and high Magic-Angle Spinning frequency using large radio frequency field. Such spectrum allows separating the signal of β-Ga2Se3 and that of an impurity.

A high-resolution natural abundance 33S MAS NMR study of the cementitious mineral ettringite.

Despite the widespread occurrence of sulfur in both natural and man-made materials, the 33S nucleus has only rarely been utilised in solid-state NMR spectroscopy on account of its very low natural abundance (0.76%), low NMR frequency (ν0 = 30.7 MHz at B0 = 9.4 T), and significant nuclear quadrupole moment (spin I = 3/2, Q = -69.4 mb). Satellite-transition magic angle spinning (STMAS) is an NMR method for obtaining high-resolution spectra of half-integer quadrupolar nuclei (spin I > 1/2) in solids and is notable for its intrinsic sensitivity advantage over the similar multiple-quantum (MQMAS) method, especially for nuclei with low NMR frequencies. In this work we demonstrate the feasibility of natural abundance 33S STMAS NMR experiments at B0 = 9.4 T and 20.0 T using a model sulfate sample (Na2SO4 + K2SO4 in a 1 : 1 molar ratio). Furthermore, we undertake a natural abundance 33S STMAS NMR study of the cement-forming mineral ettringite (Ca6Al2(SO4)3(OH)12·26H2O) at B0 = 9.4 T and 20.0 T, resolving a discrepancy in the literature between two previous conventional 33S MAS NMR studies and obtaining an alternative set of 33S NMR parameters that is simultaneously consistent with the MAS and STMAS data at both field strengths.

Analyses of Aluminum Structures in a Chinese Coal Ash and Its Slag by STMAS NMR

Double-quantum filter satellite-transition magic-angle spinning experiments were tentatively carried out by one high magnetic field solid-state nuclear magnetic resonance (800 MHz for 1H Larmor frequency) to analyze the local 27Al structure in minerals of coal ash and slag. A high magnetic field offered higher sensitivity and resolution; hereby, the inconspicuous resonances of satellite-transition magic-angle spinning were obtained successfully at less stringent conditions. An obvious single 6-coordinate 27Al resonance was detected in the low-temperature ash; structures in pre-molten ashes (as prepared at 815 and 1,000°C) located relatively integral and symmetric, while Al resonances in the ash prepared at 1,600°C after once completely molten demonstrated discrete and asymmetric distribution. Moreover, the detailed spatial correlations among various aluminum species in rapid quenching slag exhibited dispersive T-O-T structures with lower signal-to-noise ratio of resonances.

MAS, STMAS and DQMAS NMR Studies of the Thermal Transformation of Kaolinite

Thermal transformations of kaolinite at different temperatures were monitored using X-ray diffraction (XRD), high-resolution solid-state nuclear magnetic resonance (800 MHz for 1H Larmor frequency) with single-pulse magic-angle spinning, double-quantum filter satellite-transition magic-angle spinning, and double-quantum homo-nuclear correlation under magic-angle spinning experiments. Results show that combined experiments clearly manifest the transitions of silicon and aluminum structures at different thermal treatment stages; and moreover, high magnetic field offers higher sensitivity and resolution, hereby the slim resonances are obtained successfully at less stringent conditions. The dehydroxylation process of kaolinite causes the presence of short-range order in metakaolinite, which is absence of XRD reflections. Particularly, the features of metakaolinite with high concentration of defects are found with dispersive aluminum coordinations; and further, the distorted tetrahedral aluminum is detected in kaolinite-derived mullite because of the locally disorganized structure. The framework structure of kaolinite-derived mullite is considered to be primarily formed by the tetrahedral aluminum bonding with octahedral aluminum. In addition, except for the primary limitation caused by potentially long relaxation time of sample, such approaches are applicable to obtain detailedly structural characteristics of aluminosilicate.

Analysis of Atomic Scale Chemical Environments of Boron in Coal by 11B Solid State NMR

Atomic scale chemical environments of boron in coal has been studied by solid state NMR spectroscopy including magic angle spinning (MAS), satellite transition magic angle spinning (STMAS), and cross-polarization magic angle spinning (CPMAS). The (11)B NMR spectra can be briefly classified according to the degree of coalification. On the (11)B NMR spectra of lignite, bituminous, and sub-bituminous coals (carbon content of 70-90mass%), three sites assigned to four-coordinate boron ([4])B with small quadrupolar coupling constants (≤0.9 MHz) are observed. Two of the ([4])B sites in downfield are considered organoboron complexes with aromatic ligands, while the other in the most upper field is considered inorganic tetragonal boron (BO(4)). By contrast, on the (11)B NMR spectra of blind coal (carbon content >90mass%), the ([4])B which substitutes tetrahedral silicon of Illite is observed as a representative species. It has been considered that the organoboron is decomposed and released from the parent phase with the advance of coal maturation, and then the released boron reacts with the inorganic phase to substitute an element of inorganic minerals. Otherwise boron contained originally in inorganic minerals might remain preserved even under the high temperature condition that is generated during coalification.

Chemical state of boron in coal fly ash investigated by focused-ion-beam time-of-flight secondary ion mass spectrometry (FIB-TOF-SIMS) and satellite-transition magic angle spinning nuclear magnetic resonance (STMAS NMR)

The chemical states of boron in coal fly ash, which may control its leaching into the environment, were investigated by focused-ion-beam time-of-flight secondary ion mass spectrometry (FIB-TOF-SIMS) and satellite-transition magic angle spinning nuclear magnetic resonance (STMAS NMR) spectroscopy. The distribution of boron on the surface and in the interior of micron-sized fly ash particles was directly observed by FIB-TOF-SIMS. Coordination numbers of boron and its bonding with different atoms from particles of bulk samples were investigated by STMAS NMR. Boron in coal fly ash with relatively poor leaching characteristics appears as trigonal BO3 and coexists with Ca and Fe at the outer layer of every particle and inside CaO–MgO particles. In contrast, boron in coal fly ash with better leaching characteristics appears as CaO- or MgO-trigonal BO3 and tetragonal BO4, and it is distributed only on the outer surface of each ash particle without showing any correlation with a particular element.

Q-shear transformation for MQMAS and STMAS NMR spectra

The multiple-quantum magic-angle spinning (MQMAS) and satellite-transition magic-angle spinning (STMAS) experiments refocus second-order quadrupolar broadening of half-integer quadrupolar spins in the form of two-dimensional experiments. Isotropic shearing is usually applied along the indirect dimension of the 2D spectra such that an isotropic projection free of anisotropic quadrupolar broadening can be obtained. An alternative shear transformation by a factor equal to the coherence level (quantum number) selected during the evolution period is proposed. Such a transformation eliminates chemical shift along the indirect dimension leaving only the second-order quadrupolar-induced shift and anisotropic broadening, and is expected to be particularly useful for disordered systems. This transformation, dubbed Q-shearing, can help avoid aliasing problems due to large chemical shift ranges and spinning sidebands. It can also be used as an intermediate step to the isotropic representation for expanding the spectral window of rotor-synchronized experiments.

First High-Resolution 11B Nuclear Magnetic Resonance (NMR) Spectra of Coal Fly Ash by Satellite-Transition Magic Angle Spinning (STMAS) NMR

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationFirst High-Resolution 11B Nuclear Magnetic Resonance (NMR) Spectra of Coal Fly Ash by Satellite-Transition Magic Angle Spinning (STMAS) NMRTakafumi Takahashi*†, Shunsuke Kashiwakura‡, Koji Kanehashi†, and Tetsuya Nagasaka‡View Author Information Advanced Technology Research Laboratories, Nippon Steel Corporation, 20-1 Shintomi, Futtsu 293-8511 Japan, and Graduate School of Environmental Studies, Tohoku University, Sendai 980-8579, Japan* To whom correspondence should be addressed. Fax: +81-439-80-2746. E-mail: [email protected]†Nippon Steel Corporation.‡Tohoku University.Cite this: Energy Fuels 2009, 23, 3, 1778–1780Publication Date (Web):February 19, 2009Publication History Received14 October 2008Revised30 January 2009Published online19 February 2009Published inissue 19 March 2009https://doi.org/10.1021/ef800886nCopyright © 2009 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views401Altmetric-Citations7LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (170 KB) Get e-AlertsSUBJECTS:Boron,Chemical structure,Coal,Iron,Leaching Get e-Alerts

Combining STMAS and CRAMPS NMR spectroscopy: High-resolution HETCOR NMR spectra of quadrupolar and 1H nuclei in solids

High-resolution two-dimensional (2D) heteronuclear correlation spectra between half-integer quadrupolar and 1H nuclei have been obtained combining Satellite Transition Magic-Angle Spinning (STMAS) and wPMLG3 CRAMPS methods. The experiments use split-t 1 versions of DQ/DQF-STMAS adapted to 3/2 and 5/2 spins to obtain a 23Na and 27Al isotropic dimension, respectively. Transfer of magnetization from quadrupolar nuclei to protons has been achieved by cross-polarization, and high-resolution 1H spectra have been recorded using the wPMLG3 decoupling during the t 2 evolution period. The performance of the pulse sequences have been tested on the templated microporous aluminophosphate IST-1 and trisodium citrate employing a B 0 field of 9.4 T.

Solid-State 17O NMR Spectroscopy of Hydrous Magnesium Silicates: Evidence for Proton Dynamics

First-principles calculations of O-17 quadrupolar and chemical shift NMR parameters were performed using CASTEP, a density functional theory (I)FT) code, to try and interpret high-resolution O-17 NMR spectra of the humite group minerals hydroxyl-chondrodite (2Mg(2)SiO(4)center dot Mg(OH)(2)) and hydroxyl-clinohumite (4Mg(2)SiO(4)center dot Mg(OH)(2)), which are models for the incorporation of water within the Earth's upper mantle. The structures of these humite minerals contain two possible crystallographically inequivalent H sites with 50% occupancy. Isotropic O-17 multiple-quantum magic angle spinning (MQMAS) spectra were therefore simulated using the calculated O-17 NMR parameters and assuming either a static or dynamic model for the positional disorder of the H atoms. Only the dynamic disorder model provided simulated spectra that agree with experimental O-17 MQMAS spectra of hydroxyl-chondrodite and hydroxyl-clinohumite. Previously published O-17 satellite-transition magic angle spinning (STMAS) spectra of these minerals showed significant dynamic line-broadenings in the isotropic frequency dimension. We were able to reproduce these line-broadenings with at least qualitative accuracy using a combination of the same dynamic model for the positional H disorder, calculated values for the change in O-17 quadrupolar NMR parameters upon H exchange, and a simple analytical model for dynamic line-broadening in MAS NMR experiments. Overall, this study shows that a combination of state-of-the-art NMR methodology and first-principles calculations of NMR parameters is able to provide information on dynamic processes in solids with atomic-scale resolution that is unobtainable by any other method.

17O and29Si NMR Parameters of MgSiO3Phases from High-Resolution Solid-State NMR Spectroscopy and First-Principles Calculations

The 29Si and 17O NMR parameters of six polymorphs of MgSiO3 were determined through a combination of high-resolution solid-state NMR and first-principles gauge including projector augmented wave (GIPAW) formalism calculations using periodic boundary conditions. MgSiO3 is an important component of the Earth's mantle that undergoes structural changes as a function of pressure and temperature. For the lower pressure polymorphs (ortho-, clino-, and protoenstatite), all oxygen species in the 17O high-resolution triple-quantum magic angle spinning (MAS) NMR spectra were resolved and assigned. These assignments differ from those tentatively suggested in previous work on the basis of empirical experimental correlations. The higher pressure polymorphs of MgSiO3 (majorite, akimotoite, and perovskite) are stabilized at pressures corresponding to the Earth's transition zone and lower mantle, with perovskite being the major constituent at depths >660 km. We present the first 17O NMR data for these materials and confirm previous 29Si work in the literature. The use of high-resolution multiple-quantum MAS (MQMAS) and satellite-transition MAS (STMAS) experiments allows us to resolve distinct oxygen species, and full assignments are suggested. The six polymorphs exhibit a wide variety of structure types, providing an ideal opportunity to consider the variation of NMR parameters (both shielding and quadrupolar) with local structure, including changes in coordination number, local geometry (bond distances and angles), and bonding. For example, we find that, although there is a general correlation of increasing 17O chemical shift with increasing Si-O bond length, the shift observed also depends upon the exact coordination environment.

Dynamics on the Microsecond Timescale in Microporous Aluminophosphate AlPO-14 as Evidenced by 27Al MQMAS and STMAS NMR Spectroscopy

Multiple-quantum magic angle spinning (MQMAS) and satellite-transition magic angle spinning (STMAS) are two well-known techniques for obtaining high-resolution, or "isotropic", NMR spectra of quadrupolar nuclei. It has recently been shown that dynamics-driven modulation of the quadrupolar interaction on the microsecond timescale results in linewidths in isotropic STMAS spectra that are strongly broadened, while, in contrast, the isotropic MQMAS linewidths remain narrow. Here, we use this novel methodology in an 27Al (I = 5/2) NMR study of the calcined-dehydrated aluminophosphate AlPO-14 and two forms of as-synthesized AlPO-14, one prepared with isopropylamine (C3H7NH2) as the template molecule and one with piperidine (C5H10NH). For completeness, the 31P and 13C (both I = 1/2) MAS NMR spectra are also presented. A comparison of the 27Al MQMAS and STMAS NMR results show that, although calcined AlPO-14 appears to have a rigid framework structure, the extent of motion in the two as-synthesized forms is significant, with clear evidence for dynamics on the microsecond timescale in the immediate environments of all four Al sites in each material. Variable-temperature 27Al STMAS NMR studies of the two as-synthesized AlPO forms reveal the dynamics to be complex, with the motions of both the guest water molecules and organic template molecules shown to be contributing. The sensitivity of the STMAS NMR experiment to the presence of microsecond timescale dynamics is such that it seems likely that this methodology will prove useful in NMR studies of host-guest interactions in a wide variety of framework materials.

Satellite-Transition MAS NMR of Low-γ Nuclei at Natural Abundance: Sensitivity, Practical Implementation, and Application to 39K (I = 3/2) and 25Mg (I = 5/2)

Satellite-transition magic angle spinning (STMAS) is a recently introduced technique for recording high-resolution NMR spectra of quadrupolar nuclei in solids. We present numerical calculations of STMAS signal intensity as a function of radio frequency field strength (v(1)) and spinning rate (v(R)) and show that the sensitivity advantage of STMAS over the older multiple-quantum technique (MQMAS) is greatest for low v(1) field strengths and high v(R) rates, making STMAS particularly suitable for the study of low-gamma nuclei. The practical implementation of STMAS in NMR of low-y nuclei is discussed and several experimental examples of high-resolution K-39 (I = 3/2) and Mg-25 (I = 5/2) NMR spectra are presented, including Mg-25 spectra of brucite (Mg(OH)(2)), diopside (CaMgSi2O6), and talc (Mg3Si4O10(OH)(2)) recorded at the natural Mg-25 abundance of 10%.

Spin-locking of half-integer quadrupolar nuclei in nuclear magnetic resonance of solids: creation and evolution of coherences.

Spin-locking of half-integer quadrupolar nuclei, such as 23Na (I=3/2) and 27Al (I=5/2), is of renewed interest owing to the development of variants of the multiple-quantum and satellite-transition magic angle spinning (MAS) nuclear magnetic resonance experiments that either utilize spin-locking directly or offer the possibility that spin-locked states may arise. However, the large magnitude and, under MAS, the time dependence of the quadrupolar interaction often result in complex spin-locking phenomena that are not widely understood. Here we show that, following the application of a spin-locking pulse, a variety of coherence transfer processes occur on a time scale of approximately 1/omegaQ before the spin system settles down into a spin-locked state which may itself be time dependent if MAS is performed. We show theoretically for both spin I=3/2 and 5/2 nuclei that the spin-locked state created by this initial rapid dephasing typically consists of a variety of single- and multiple-quantum coherences and nonequilibrium population states and we discuss the subsequent evolution of these under MAS. In contrast to previous work, we consider spin-locking using a wide range of radio frequency field strengths, i.e., a range that covers both the "strong-field" (omega1 >> omegaQPAS and "weak-field" (omega1 << omegaQPAS limits. Single- and multiple-quantum filtered spin-locking experiments on NaNO2, NaNO3, and Al(acac)3, under both static and MAS conditions, are used to illustrate and confirm the results of the theoretical discussion.

Double-quantum filtered STMAS

Double-quantum and double-quantum-filtered satellite-transition magic-angle spinning (STMAS) experiments are proposed. The experiments efficiently convert satellite-transition coherence from single- to double-quantum with a central-transition selective π-pulse. The conversion allows the selection of double-quantum coherence transfer pathways with phase cycling that completely filters out unwanted diagonal and outer satellite-transition peaks. Both experiments are demonstrated with RbNO 3 and AlPO 4-berlinite as model compounds for obtaining clean STMAS spectra of spins 3/2 and 5/2, respectively.

Third-order effect in solid-state NMR of quadrupolar nuclei

The theory and experimental observation of the third-order effect in solid-state NMR of quadrupolar nuclei are presented. The third-order effect consists of spherical harmonic terms up to rank l=6 and shifts NMR frequencies between two spin states that are not symmetric such as satellite transitions. Two-dimensional satellite transition magic-angle spinning experiment averages both the first and the second-order quadrupolar interactions making the quantitative measurement of the third-order effect possible. The third-order quadrupolar effect in andalusite has been measured at 11.7 T and its powder patterns are fitted with numerical simulations.

High-resolution NMR spectroscopy of quadrupolar nuclei in solids: satellite-transition MAS with self-compensation for magic-angle misset.

Several methods are available for obtaining high-resolution NMR spectra of half-integer spin quadrupolar nuclei, such as (11)B, (23)Na (I = (3)/(2)) and (17)O, (27)Al (I = (5)/(2)), in powdered solids. Satellite-transition magic-angle spinning (STMAS) uses only conventional magic-angle spinning (MAS) hardware and, it has been claimed, improves significantly upon the signal-to-noise ratio obtained with the widely adopted multiple-quantum MAS (MQMAS) experiment. The STMAS technique, however, requires that the sample rotation axis be set to the magic angle (cos(-1)(1/ radical 3) = 54.736 degrees ) with respect to the magnetic field B(0) with an accuracy of better than +/-0.004 degrees, and this stringent requirement has severely limited the use of the method. Here, we propose a novel version of STMAS that self-compensates for magic-angle missets of up to +/-1.0 degrees and yet retains a sensitivity comparable with MQMAS. This SCAM-STMAS experiment is demonstrated on RbNO(3) using (87)Rb (I = (3)/(2)) NMR and on kyanite (Al(2)SiO(5)) using (27)Al (I = (5)/(2)) NMR.

Optimizing STMAS

The 2D satellite transition magic angle spinning (STMAS) experiment generates efficiently high-resolution isotropic NMR spectra of half-integer quadrupolar nuclei. The experiment involves excitation and coherence transfer of satellite transitions into the central transition. It requires efficient refocusing of satellite transitions and sample spinning at a very accurate magic angle to cancel the first-order quadrupolar interaction effect. A review of all parameters relevant to optimizing the STMAS experiment is presented, including pulse sequence calibration, regulating spinning speed, magic angle adjustment, optimization of satellite transition excitation, and coherence transfer for both I=3/2 and I≥5/2 nuclei.