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Solid State Nuclear Magnetic Resonance

Shigenobu Hayashi, Keiko Jimura
Mechanisms of the (1)H spin-lattice relaxation in NH4H2PO4 were studied in detail by use of the effect of magic angle spinning on the relaxation. The acid and the ammonium protons have different relaxation times at the spinning rates higher than 10 kHz due to suppression of spin diffusion between the two kinds of protons. The intrinsic relaxation times not affected by the spin diffusion and the spin-diffusion assisted relaxation times were evaluated separately, taking into consideration temperature dependence...
July 8, 2017: Solid State Nuclear Magnetic Resonance
M Shen, S Wegner, J Trébosc, B Hu, O Lafon, J P Amoureux
The most utilized through-space correlation (1)H-{X} methods with proton indirect detection use two consecutive transfers, (1)H → X and then X → (1)H, with the evolution time t1 in the middle. When the X isotope is not 100% naturally abundant (NA), only the signal of the protons close to these isotopes is modulated by the (1)H-X dipolar interactions. This signal is theoretically disentangled with phase-cycling from the un-modulated one. However, this separation is never perfect and it may lead to t1-noise in case of isotopes with very small NA, such as (13)C or even worse (15)N...
June 29, 2017: Solid State Nuclear Magnetic Resonance
Takahiro Iijima, Tadashi Shimizu
We examined a simple two-dimensional (2)H nuclear magnetic resonance spectroscopy for paramagnetic solids utilizing off-magic-angle spinning (OMAS). By adding a rotor-synchronized 180° pulse to rotational echo (RE) measurement, the effect of the shift interaction was removed from the indirect dimension. The obtained pure-quadrupole spectrum could be simulated by calculating a quasi-one-dimensional NMR signal without considering the shift interaction. The sensitivity of the proposed method was compared with that of previous static NMR methods...
June 29, 2017: Solid State Nuclear Magnetic Resonance
Pedro B Groszewicz, Hergen Breitzke, Gerd Buntkowsky
The spinning sidebands envelope of satellite transitions often display an asymmetric shape, which is caused by an asymmetric response of the NMR probe circuit. In this work, we revisit the basic concepts of the RLC circuit at the heart of every NMR probe and present two approaches capable of minimizing this artifact. While the first one consists of deliberately mistuning the probe, the second one relies on measuring the probe's response function and deconvoluting its contribution from the spectra. Both approaches are validated with (23)Na NMR spectra of a lead-free relaxor ferroelectric (BNT-1BT)...
June 24, 2017: Solid State Nuclear Magnetic Resonance
Silvina C Pérez, Mariano Zuriaga
A simple model to explain the NQR lineshape in solids with orientational disorder or substitutional disorder is presented. The particular case of m-chlorobromobenzene is studied. It is based on the assumption that Bromine atoms, of m-chlorobromobenzene molecules, behave as point defects in the m-dichlorobenzene lattice that modify the crystalline Electric Field Gradient. The model is also tested successfully in solid solutions of p-dichlorobenzene-p-dibromobenzene, where Bromine atoms of p-dibromobenzene molecules are assumed to be homogeneously distributed in the p-dichlorobenzene lattice...
June 20, 2017: Solid State Nuclear Magnetic Resonance
Hiroki Nagashima, Aany Sofia Lilly Thankamony, Julien Trébosc, Frédérique Pourpoint, Olivier Lafon, Jean Paul Amoureux
We introduce novel sequences using indirect detection to correlate quadrupolar nuclei and spin-1/2 isotopes, other than (1)H and (19)F. These sequences use γ-encoded symmetry-based RNn(ν) schemes that reintroduce the space component |m| = 1 of the heteronuclear dipolar coupling. These schemes can be applied to the indirectly detected spin in Dipolar-mediated Heteronuclear Multiple-Quantum Correlation (D-HMQC) sequence or to the detected isotope in a novel sequence, named Dipolar-mediated Heteronuclear Universal-Quantum Correlation (D-HUQC)...
June 19, 2017: Solid State Nuclear Magnetic Resonance
Henri Colaux, Yusuke Nishiyama
Although very fast MAS rate (>60 kHz) paves a way to obtain a sufficient resolution in the (1)H double-quantum magic-angle spinning (DQMAS) experiments to probe (1)H proximities, the (1)H resolution still limits wider applications below its potential use. Here, the combination of the DQMAS experiment with the constant-time (CT) acquisition approach is demonstrated, giving an increased peak-separation power in the DQ dimension. The advantages and disadvantages in terms of sensitivity and resolution of the conventional and CT approaches are discussed...
June 19, 2017: Solid State Nuclear Magnetic Resonance
Olivier Lafon
No abstract text is available yet for this article.
June 16, 2017: Solid State Nuclear Magnetic Resonance
A Samila, V Khandozhko, L Politansky
The specific feature of NQR is expansion of spectral lines which is caused not only by dipole-dipole interaction of nuclei, but also by local field nonuniformity caused by the defects and deformation in crystal matrix. Considerable line expansion, which is typical of crystals, requires in pulsed NQR method the optimization of pulse shape and the reserve of transmitter power output. Parametric computer identification was used to study a dependence of parameters of the energy spectra of the output signal of pulsed NQR spectrometer transmitter on the duration of excitation pulses with sine and noise occupation...
June 8, 2017: Solid State Nuclear Magnetic Resonance
Guillaume Girard, Filipe Vasconcelos, Lionel Montagne, Laurent Delevoye
The present study has investigated the structure of four niobium phosphates compounds using (31)P MAS NMR spectroscopy. Niobium (93)Nb decoupling, applied during (31)P NMR acquisition led to a resolution enhancement by a factor of 2-3, which allowed distinguish phosphorous sites separated by 1 ppm or less. The assignment of (31)P spectra has been completed by use of first-principles calculations derived from the original XRD structures. One of the compounds, Na3.04Nb7P4O29, contains a sodium vacancy, clearly revealed in the (31)P MAS spectrum obtained with (93)Nb decoupling...
June 2, 2017: Solid State Nuclear Magnetic Resonance
Piotr Paluch, Julien Trébosc, Jean-Paul Amoureux, Marek J Potrzebowski
We present an NMR methodology which can be used to study the dynamical processes occurring in organophosphorus compounds that belong to the group of the organic ionic plastic crystals (OIPCs). As model samples we employed two phosphonium tetrafluoroborate salts; (t-Bu)3PH(+)BF4(-) (1) and (Me)3PH(+)BF4(-) (2). Both samples possess in their structures direct H-P bonds, and both undergo complex thermal processes in the solid state, forming below the melting point three or four phases, respectively. (1)H-(31)P CPVC (Cross-Polarization Variable Contact) measurements were performed under Very Fast Magic Angle Spinning with speed equal to 50 or 60 kHz, in order (i) to establish the hydrogen-phosphorus dipolar couplings, and (ii) to correlate the dipolar splitting values with molecular motions of the cation...
June 1, 2017: Solid State Nuclear Magnetic Resonance
Xiaolong Liu, Yueying Chu, Qiang Wang, Weiyu Wang, Chao Wang, Jun Xu, Feng Deng
Well-crystallized Ge-free and Ge-ITQ-13 were successfully obtained by solid state synthesis method. The Ge/Si ratio and the water content that are the two important factors in the synthesis of germanosilicate zeolites were explored for the formation of ITQ-13. The effect of the mineralizing agents (NH4F and NH4Cl) on the ITQ-13 synthesis was investigated as well. The obtained pure silica ITQ-13 and Ge-ITQ-13 were characterized by one- and two-dimensional solid- state NMR techniques. One-dimensional (1D) (19)F MAS, (1)H→(29)Si CP/MAS and (19)F→(29)Si CP/MAS NMR spectroscopy evidenced the formation of pure Si-D4R (double four ring) and Ge-D4R units, with the latter being generated by substitution of Si atom from the former units...
May 17, 2017: Solid State Nuclear Magnetic Resonance
P Lokeswara Rao, Bholanath Pahari, M Shivanand, Tukaram Shet, K V Ramanathan
This paper reports results of (23)Na and (29)Si solid-state NMR investigations carried out on sodium strontium silicate ion conductor, Sr0.55Na0.45SiO2.775 and presents the first experimental evidence to show that different synthesis conditions induce multiple devitrified phases. Along with 1-dimensional NMR, (23)Na MQMAS spectra have been used to identify the phases corresponding to polymorphs of Na2Si2O5, in addition to the crystalline SrSiO3 and the glass/amorphous Na2Si2O5 phases. The surprising observation of about an order of magnitude higher ionic conductivity achieved in devitrified samples is attributed to the growth of the crystalline δ-Na2Si2O5 phase within the amorphous Na2Si2O5 phase domains, identified using NMR...
May 12, 2017: Solid State Nuclear Magnetic Resonance
Xiaoyue Zhou, Kaipin Xu, Pei Ni, Qun Chen, Shanmin Zhang
Most of the polymers are composed of a crystal part, an amorphous part, and a transitional interfacial part. These components present disparate physical and chemical characteristics. However, it always suffers from peak overlapping in solid NMR spectrum in order to acquire polymer's crystallinity. The polyethylene oxide (PEO) sample was tested using the Torchia pulse sequence combined with the Multivariate Curve Resolution (MCR) method. A two dimensional CP/MAS spectrum containing spin-lattice relaxation time (T1) information was acquired...
September 2017: Solid State Nuclear Magnetic Resonance
Christophe Odin
In NMR, the repetition of pulse sequences with a recycle time that does not allow the spin system to completely relax back to equilibrium is a well known and often used method to increase the signal to noise ratio at given total measuring time. For isolated spins I=1/2, the steady-state of a train of strictly identical pulse sequences separated by free evolution periods of same duration is described by the well known Ernst-Anderson model, and the optimum pulse angle is given by the Ernst angle. We showed recently that equivalent formula, but with super-operators in the Liouville space, can be obtained for general spins I...
September 2017: Solid State Nuclear Magnetic Resonance
Paul Jonsen
During August 2015, the author surveyed 76 solid state NMR scientists from materials science to biology, academic to industrial, based in North America, Europe, India, China, Japan and Australia. The subject concerned barriers to the wider acceptance of solid state NMR and included the various barriers based on experimental, funding, vendor based and community aspects. This survey was confidential. However, many of the survey participants requested that at least the results of the part of the survey relevant to our community be made public...
September 2017: Solid State Nuclear Magnetic Resonance
K Seleznyova, N A Sergeev, M Olszewski, P Stępień, S V Yagupov, M B Strugatsky, J Kliava
A comparative analysis of the Czjzek's and Maurer's models of the joint distribution density of NMR quadrupole parameters has been carried out in view of their application to account for spectra broadening induced by local disorder in crystals. As an example of such an application, we have considered Magic Angle Spinning NMR of (11)B and (71)Ga isotopes in polycrystalline gallium borate. Computer simulations carried out using both models unambiguously show that in the case of low local disorder the Maurer's model, in contrast to the Czjzek's model, provides satisfactory fits to experimental NMR spectra...
September 2017: Solid State Nuclear Magnetic Resonance
Peter A Beckmann, Joseph M Bohen, Jamie Ford, William P Malachowski, Clelia W Mallory, Frank B Mallory, Andrew R McGhie, Arnold L Rheingold, Gilbert J Sloan, Steven T Szewczyk, Xianlong Wang, Kraig A Wheeler
We report a variety of experiments and calculations and their interpretations regarding methyl group (CH3) rotation in samples of pure 3-methylglutaric anhydride (1), pure 3-methylglutaric acid (2), and samples where the anhydride is slowly absorbing water from the air and converting to the acid [C6H8O3(1) + H2O → C6H10O4(2)]. The techniques are solid state (1)H nuclear magnetic resonance (NMR) spin-lattice relaxation, single-crystal X-ray diffraction, electronic structure calculations in both isolated molecules and in clusters of molecules that mimic the crystal structure, field emission scanning electron microscopy, differential scanning calorimetry, and high resolution (1)H NMR spectroscopy...
September 2017: Solid State Nuclear Magnetic Resonance
Maria Makrinich, Rupal Gupta, Tatyana Polenova, Amir Goldbourt
The ability of various pulse types, which are commonly applied for distance measurements, to saturate or invert quadrupolar spin polarization has been compared by observing their effect on magnetization recovery curves under magic-angle spinning. A selective central transition inversion pulse yields a bi-exponential recovery for a diamagnetic sample with a spin-3/2, consistent with the existence of two processes: the fluctuations of the electric field gradients with identical single (W1) and double (W2) quantum quadrupolar-driven relaxation rates, and spin exchange between the central transition of one spin and satellite transitions of a dipolar-coupled similar spin...
April 21, 2017: Solid State Nuclear Magnetic Resonance
Diego F Gauto, Audrey Hessel, Petra Rovó, Vilius Kurauskas, Rasmus Linser, Paul Schanda
Solid-state NMR spectroscopy can provide site-resolved information about protein dynamics over many time scales. Here we combine protein deuteration, fast magic-angle spinning (~45-60kHz) and proton detection to study dynamics of ubiquitin in microcrystals, and in particular a mutant in a region that undergoes microsecond motions in a β-turn region in the wild-type protein. We use (15)N R1ρ relaxation measurements as a function of the radio-frequency (RF) field strength, i.e. relaxation dispersion, to probe how the G53A mutation alters these dynamics...
April 14, 2017: Solid State Nuclear Magnetic Resonance
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