Solid-state double-resonance NMR experiments involving quadrupolar and spin 1/2 nuclei

Fyfe, C. A.; Mueller, Klaus A.; Grondey, H.; Wong-Moon, K. C.

doi:10.1021/j100153a012

Cited by 131 publications

(112 citation statements)

References 18 publications

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“…The TEDOR pulse sequence is useful for transferring polarization from one type of nucleus to another type via relatively weak dipolar couplings [43,44]. The two-dimensional version, which has been developed and applied to polarization transfer from quadrupolar nuclei to spin-1/2 nuclei [45][46][47][48][49], yields a 2D spectrum showing correlated signal intensity from spatially-proximate nuclear spin pairs that are dipole-dipole coupled. In our case the result is a 2D contour plot with 71 Ga and 15 N shift axes, and a 1D projection spectrum for 15 N. The relative intensity at each 15 N shift position reflects the number of 15 N nuclei at a given 15 N shift that are dipolecoupled (through space, <1 nm) to 71 Ga nuclei having the range of 71 Ga shifts depicted in the 2D contour plot.…”

Section: Oretical Line From Eq(3) Similar Distributions Ofmentioning

confidence: 99%

Spatially correlated distributions of local metallic properties in bulk and nanocrystalline GaN

et al. 2017

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We compare local electronic structure at different atom types of a metallic semiconductor in bulk and nanocrystalline form. Multinuclear magic-angle-spinning nuclear magnetic resonance (MAS NMR) establishes that GaN synthesized as an intentionally-doped bulk powder or as annealed nanocrystalline particles exhibits metallic behavior and a wide distribution of differing electronic environments in both forms. Bulk polycrystalline wurtzite GaN doped with 0.13% Ge as a shallow donor exhibits a temperature-independent distribution of 71 Ga Knight shifts over the temperature range 123-473 K. Each Knight shift frequency in the inhomogeneously-broadened spectrum is characterized by a 71 Ga spin-lattice relaxation time T 1 that is in good agreement with the value predicted by the Knight-Korringa relation across the broad range of temperatures. The14 N spectrum shows a slightly smaller Knight shift distribution with spin-lattice relaxation time T 1 values at 295 K across the distribution also in good agreement with the Knight-Korringa relation. Similarly, annealed nanocrystalline wurtzite GaN (50-100 nm, and without Ge) exhibits a 71 Ga Knight shift distribution and T 1values (at 295 K) that follow the same Knight-Korringa behavior. Thus, both bulk and nanocrystalline forms of GaN are n-type and well above the metal-insulator transition (MIT), the nanocrystals most likely as a result of incorporation of shallow donor oxygen atoms during synthesis. Carriers in both forms of sample exhibit the near-ideal characteristics of a degenerate Fermi gas of non-interacting spins. The observation of NMR signals from both atom types, Ga and N, allows for the direct spatial correlation of the local electronic structure at the two sites in the lattice, specifically the s-orbital character of the electronic wavefunction of conduction band electrons at the Fermi edge. The relative values of these carrier wavefunction probabilities (nearly twice as great for the N atom as for the Ga) are in line with theoretical predictions. Analyses of 71 Ga, 14 N, and 15 N NMR results, including double-resonance 2D 15 N{ 71 Ga} measurements, reveal electronic disorder in the form of broad distributions of local metallic properties (Knight shifts) that are shown to be spatially correlated on a sub-nanometer scale.

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Section: Oretical Line From Eq(3) Similar Distributions Ofmentioning

confidence: 99%

Spatially correlated distributions of local metallic properties in bulk and nanocrystalline GaN

et al. 2017

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“…See text for further details. (b, c) Two-dimensional 87 Rb (130.9 MHz) STMAS NMR spectra of RbNO 3 , recorded using a split-t 1 experiment (25). In (c), the magic angle is misset by 0.03°, severely compromising the sensitivity and resolution.…”

Section: Satellite-transition Magic-angle Spinning (Stmas)mentioning

confidence: 99%

“…As shown in Fig. 2.3(c), an 87 Rb (130.9 MHz) STMAS spectrum of RbNO 3 where the magic angle is misset by only 0.03°, this severely compromises the sensitivity and resolution of STMAS (25). It can be estimated that the magic angle must be set with an accuracy of ϳ0.002°or better if good high-resolution spectra are to be achieved.…”

Section: Concepts In Magnetic Resonancementioning

confidence: 99%

Structural information from quadrupolar nuclei in solid state NMR

Ashbrook

Duer

2006

Concepts Magnetic Resonance

146

262

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Solid-state NMR has become the method of choice for determining details of molecular-level structure in heterogeneous systems. Though spin-1/2 nuclei still form the core of most such studies, quadrupolar nuclei are increasingly being used. This review assesses what is currently possible, from achieving high-resolution spectra for quadrupolar nuclei (a prerequisite for most structure determination work), to forming correlation spectra which give qualitative details of spatial proximity of nuclei and the determination of internuclear distances, between quadrupolar spins and quadrupolar and spin-1/2 nuclei. Examples are given of each method discussed, and the advantages and disadvantages of the various experiments for different possible applications are assessed.

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“…58 Obviously, this approach will not work in the case of a disordered zeolite surface where a broad distribution of internuclear distances always prevails. 51,52 A certain success has been achieved recently by Grey et al 62 -65 in the study of Lewis acidity of dealuminated zeolite HY with a TRAPDOR technique. 62 This technique is specifically designed to measure QCC values and to estimate internuclear distances by observing a signal from spin- 1 2 nuclei coupled to quadrupolar nuclei ( 27 Al) by heteronuclear dipolar interaction.…”

Section: Sample Preparation and Experimental Strategymentioning

confidence: 99%

Characterization of Brønsted and Lewis acidity in zeolites by solid-state NMR and the recent progress in the REDOR technique

Blumenfeld

Fripiat

1999

Magn. Reson. Chem.

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Solid-state double-resonance NMR experiments involving quadrupolar and spin 1/2 nuclei

Cited by 131 publications

References 18 publications

Spatially correlated distributions of local metallic properties in bulk and nanocrystalline GaN

Spatially correlated distributions of local metallic properties in bulk and nanocrystalline GaN

Structural information from quadrupolar nuclei in solid state NMR

Characterization of Brønsted and Lewis acidity in zeolites by solid-state NMR and the recent progress in the REDOR technique

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