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Solid State Nuclear Magnetic Resonance

Marko Bertmer
Solid-state NMR (SSNMR) experiments are mainly performed on diamagnetic materials. However, the study of paramagnetic materials offers access to additional information in combination with the unpaired electron. This article discusses the experimental complications arising when considering paramagnetic materials such as large shift effects and large linewidths. A look at the theoretical description as well as experimental methods are shown and accompanied by techniques for signal assignment, also with the help of quantum-chemical calculations...
November 9, 2016: Solid State Nuclear Magnetic Resonance
S Greiser, M Hunger, C Jäger
(29)Si{(27)Al} TRAPDOR MAS NMR was applied to two faujasite-type zeolites with Si/Al ratios of 1.3 (Na-X) and 2.7 (Na-Y). The aim of this test study is to show that different Q(4)(mAl) sites (m =4, 3, 2, 1) can be distinguished by differently strong TRAPDOR effects (ΔS/S0). Indeed, it was found that the TRAPDOR effect depends on the number m of AlO4 units connected to the Q(4) silicon tetrahedrons. For Na-X, the measured ΔS/S0 values are 1 : 0.81 : 0.56 for Q(4)(4Al), Q(4)(3Al) and Q(4)(2Al), respectively (normalized to Q(4)(4Al))...
October 8, 2016: Solid State Nuclear Magnetic Resonance
Ryan J McCarty, Jonathan F Stebbins
This paper demonstrates the approach of using paramagnetic effects observed in NMR spectra to investigate the distribution of lanthanide dopant cations in YAG (yttrium aluminum garnet, Y3Al5O12) optical materials, as a complimentary technique to optical spectroscopy and other standard methods of characterization. We investigate the effects of Ce(3+), Nd(3+), Yb(3+), Tm(3+), and Tm(3+)-Cr(3+) on (27)Al and (89)Y NMR spectra. We note shifted resonances for both AlO4 and AlO6 sites. In some cases, multiple shifted peaks are observable, and some of these can be empirically assigned to dopant cations in known configurations to the observed nuclides...
October 6, 2016: Solid State Nuclear Magnetic Resonance
Brendan W Wilson, Arlo A Parker, Terry Gullion
The measurement of the dipolar interaction between two spins provides the distance between nuclei. A better structural picture emerges when the distance is combined with the orientation of the internuclear vector in the principal axis system of the chemical shift anisotropy tensor. The SEDOR experiment is used on a static sample of alanine to show that the orientation of the vector connecting the nitrogen and carboxylate carbon nuclei can be accurately determined in the CSA PAS of the (13)C carboxylate spin...
September 20, 2016: Solid State Nuclear Magnetic Resonance
Colan E Hughes, Kenneth D M Harris
Two new methods for calculating lineshapes in solid-state NMR spectra are described. The first method, which we refer to as semi-analytical, allows the rapid calculation of quadrupolar central-transition lineshapes in both static and magic-angle spinning cases. The second method, which is fully numerical, allows the calculation of lineshapes resulting from any combination of interactions, including quadrupolar, dipolar and chemical shift anisotropy, and is not restricted to cases in which the principal axis systems for the different interactions are aligned...
November 2016: Solid State Nuclear Magnetic Resonance
J W Zwanziger
The assumptions underlying the popular projector-augmented wave (PAW) method of computing electronic structure in solids are examined, with primary attention to the computation of NMR observables. In particular, the assumption of non-overlapping PAW spheres is studied, and it is shown that when the spheres do overlap, the errors may be significant and furthermore are of unpredictable sign. Examples are provided by comparing PAW-based calculations with and without overlapping spheres, with the highly accurate all-electron linear augmented wave method...
November 2016: Solid State Nuclear Magnetic Resonance
Lei Zhou, Shenhui Li, Guodong Qi, Yongchao Su, Jing Li, Anmin Zheng, Xianfeng Yi, Qiang Wang, Feng Deng
The carbonylation of methanol with carbon monoxide to generate methyl acetate over Cu-H-MOR and H-MOR zeolites is studied using solid-state NMR spectroscopy. It is found that the catalytic activity of Cu-H-MOR zeolite is much higher than that of H-MOR zeolite. The presence of Cu(+) species enables the stabilization of dimethyl ether, which efficiently suppresses the hydrocarbon formation during carbonylation process over Cu-H-MOR zeolite. In addition, the carbon monoxide adsorbed on Cu(+) site is not an active species to produce either methyl acetate or acetic acid...
November 2016: Solid State Nuclear Magnetic Resonance
Tuo Wang, Pyae Phyo, Mei Hong
Plant biomass has become an important source of bio-renewable energy in modern society. The molecular structure of plant cell walls is difficult to characterize by most atomic-resolution techniques due to the insoluble and disordered nature of the cell wall. Solid-state NMR (SSNMR) spectroscopy is uniquely suited for studying native hydrated plant cell walls at the molecular level with chemical resolution. Significant progress has been made in the last five years to elucidate the molecular structures and interactions of cellulose and matrix polysaccharides in plant cell walls...
September 2016: Solid State Nuclear Magnetic Resonance
Marco Tassi, Gunter Reekmans, Robert Carleer, Peter Adriaensens
For the first time, an absolute quantification of hybrid materials obtained from the reaction of phenylphosphonic acid (PPA) with TiO2 nanoparticles under different reaction conditions is reported. Next to the amount of PPA involved in grafting to the TiO2 nanoparticles, also the PPA included in titaniumphenylphosphonate crystallites is described quantitatively. The quantitative analysis is based on solid state (31)P MAS NMR and is further applied to evaluate the stability of the resulting hybrid materials towards hydrolysis and organic solvent exposure...
September 2016: Solid State Nuclear Magnetic Resonance
N Ya Sinyavsky, I G Mershiev, G S Kupriyanova
The article describes the results of the experimental study of the molecular crystal of paradichlorobenzene in α- and β-phases by means of NQR-relaxometry with the inversion of Laplace transformation. The anisotropy effect of the pore space of wood on the distribution of times of the spin-lattice relaxation of p-C6H4Cl2 in the pores of pre-impregnated with the molten sample is shown. It was established that the increase in the T1 spin-lattice relaxation time of (35)Cl nucleus in the wood pores (channels) is observed in the case when the radio frequency field B1 is parallel to the tracheid's of wood...
September 2016: Solid State Nuclear Magnetic Resonance
E M Levin, J-F Cui, K Schmidt-Rohr
(125)Te NMR spectra and spin-lattice relaxation times, T1, have been measured for several GeTe-based materials with Te excess. The spectra show inhomogeneous broadening by several thousand ppm and a systematic variation in T1 relaxation time with resonance frequency. The quadratic dependence of the spin-lattice relaxation rate, 1/T1, on the Knight shift in the Korringa relation is found to be valid over a wide range of Knight shifts. This result confirms that T1 relaxation in GeTe-based materials is mostly dominated by hyperfine interaction between nuclei and free charge carriers...
September 2016: Solid State Nuclear Magnetic Resonance
Simone Sturniolo, Timothy F G Green, Robert M Hanson, Miri Zilka, Keith Refson, Paul Hodgkinson, Steven P Brown, Jonathan R Yates
We introduce two open source tools to aid the processing and visualisation of ab-initio computed solid-state NMR parameters. The Magres file format for computed NMR parameters (as implemented in CASTEP v8.0 and QuantumEspresso v5.0.0) is implemented. MagresView is built upon the widely used Jmol crystal viewer, and provides an intuitive environment to display computed NMR parameters. It can provide simple pictorial representation of one- and two-dimensional NMR spectra as well as output a selected spin-system for exact simulations with dedicated spin-dynamics software...
September 2016: Solid State Nuclear Magnetic Resonance
Holger Kirchhain, Julian Holzinger, Adrian Mainka, Andreas Spörhase, Sabarinathan Venkatachalam, Achim Wixforth, Leo van Wüllen
A low cost version to enable high temperature MAS NMR experiments at temperatures of up to 700°C and spinning speeds of up to 10kHz is presented. The method relies on inductive heating using a metal coated rotor insert. The metal coating is accomplished via a two step process involving physical vapor deposition and galvanization.
September 2016: Solid State Nuclear Magnetic Resonance
Yusuke Nishiyama
In spite of tremendous progress made in pulse sequence designs and sophisticated hardware developments, methods to improve sensitivity and resolution in solid-state NMR (ssNMR) are still emerging. The rate at which sample is spun at magic angle determines the extent to which sensitivity and resolution of NMR spectra are improved. To this end, the prime objective of this article is to give a comprehensive theoretical and experimental framework of fast magic angle spinning (MAS) technique. The engineering design of fast MAS rotors based on spinning rate, sample volume, and sensitivity is presented in detail...
September 2016: Solid State Nuclear Magnetic Resonance
Alan Gregorovič, Tomaž Apih, Janez Seliger
Here we describe a method for the extraction of (14)N quadrupole parameters from a (1)H-(14)N cross-relaxation spectrum by fitting the lineshapes of the (14)N quadrupole transitions. The procedures used typically to fit quadrupole lineshapes are not directly applicable to fit the (1)H-(14)N cross-relaxation spectrum, because the presence of proton homonuclear dipolar interaction broadens the lineshapes considerably and prevents a reliable determination of Cq and η from a single lineshape. Instead, one must fit two or even three lineshapes originating from the same nitrogen site simultaneously...
September 2016: Solid State Nuclear Magnetic Resonance
Nicholai Daugaard Jensen, Morten Bjerring, Ulla Gro Nielsen
Para-amino salicylate (PAS), a tuberculosis drug, was intercalated in three different layered double hydroxides (MgAl, ZnAl, and CaAl-LDH) and the samples were studied by multi-nuclear ((1)H, (13)C, and (27)Al) solid state NMR (SSNMR) spectroscopy in combination with powder X-ray diffraction (PXRD), elemental analysis and IR-spectroscopy to gain insight into the bulk and atomic level structure of these LDHs especially with a view to the purity of the LDH-PAS materials and the concentration of impurities. The intercalations of PAS in MgAl-, ZnAl-, and CaAl-LDH's were confirmed by (13)C SSNMR and PXRD...
September 2016: Solid State Nuclear Magnetic Resonance
Ming Shen, Qun Chen, Jean-Paul Amoureux, Bingwen Hu
We show here that composite pulses allow broad-band excitation of nitrogen-14 overtone frequencies in proton detected D-HMQC experiments (referred to (1)H-{NOTDQ14} D-HMQC). Experimental verifications have been performed on glycine, L-histidine and N-acetyl-valine (NAV) samples. Composite pulses enable symmetric excitations of (14)N sites with large shift differences. Therefore, this approach is promising for recording high resolution (1)H-{NOTDQ14} D-HMQC spectra of most amino-acids, pharmaceutical samples and peptides...
September 2016: Solid State Nuclear Magnetic Resonance
Bo Peng, Ming Shen, Jean-Paul Amoureux, Bingwen Hu
The WURST-CPMG pulse sequence enables: (i) observing very broad spectra due to WURST excitation, and (ii) increasing the S/N ratio due to CPMG acquisition. However, strong baseline distortions may be observed, which make the extraction of the tensor information difficult. We propose a slight modification of the sequence, WURST-CPMGM, in which we skip the first M echoes and we only acquire the following ones. This simple treatment mostly eliminates the strong background signal and the ring down effects, leading to a flat baseline...
September 2016: Solid State Nuclear Magnetic Resonance
Ryan C Nieuwendaal
We discuss the precision of 1D chemical-shift-based (1)H spin diffusion NMR experiments as well as straightforward experimental protocols for reducing errors. The (1)H spin diffusion NMR experiments described herein are useful for samples that contain components with significant spectral overlap in the (1)H NMR spectrum and also for samples of small mass (<1mg). We show that even in samples that display little spectral contrast, domain sizes can be determined to a relatively high degree of certainty if common experimental variability is accounted for and known...
June 2016: Solid State Nuclear Magnetic Resonance
A M Panich, N A Sergeev, M Paczwa, M Olszewski
Behavior of water molecules entrapped in nanochannels of zeolite mordenite has been investigated by (1)H NMR technique. The (1)H spectra and spin-lattice relaxation times in the laboratory and rotating frames, T1 and T1ρ, respectively, as well as the dipolar relaxation time T1D have been measured in the temperature range from 96 to 351K. Diffusion of water molecules along the channels was observed above ~200K. While in bulk liquid the dipolar ordered state of nuclear spins is not formed owing to complete motional average of dipolar interactions, we show that such a state is observed for mobile molecules confined in a restricted geometry...
June 2016: Solid State Nuclear Magnetic Resonance
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