Solution and solid-state 33 S NMR studies of 33 S-labeled taurine.

Sulfur-33(33 S) stable-isotope labeled taurine, 2-aminoethanesulfonic acid, has been synthesized, and a series of solution and solid-state 33 S nuclear magnetic resonance (NMR) experiments at 14.1 and 18.8 T, respectively, have been carried out at room temperature. The single peak of a solution 33 S NMR spectrum in 0.1-mM [33 S]-taurine in D2 O can be observed with the signal-to-noise (S/N) ratio of 9 in 40,000 scans, which paves the way toward in vivo analysis of pharmacokinetics and metabolism of 33 S-labeled taurine. Undistorted magic-angle-spinning (MAS) and static 33 S NMR spectra of polycrystalline [33 S]-taurine are observed with sufficient S/N ratios for analysis, and the magnitudes of 33 S EFG and CS tensors can be obtained.

Hidden chemical order in disordered Ba7Nb4MoO20 revealed by resonant X-ray diffraction and solid-state NMR.

The chemical order and disorder of solids have a decisive influence on the material properties. There are numerous materials exhibiting chemical order/disorder of atoms with similar X-ray atomic scattering factors and similar neutron scattering lengths. It is difficult to investigate such order/disorder hidden in the data obtained from conventional diffraction methods. Herein, we quantitatively determined the Mo/Nb order in the high ion conductor Ba7Nb4MoO20 by a technique combining resonant X-ray diffraction, solid-state nuclear magnetic resonance (NMR) and first-principle calculations. NMR provided direct evidence that Mo atoms occupy only the M2 site near the intrinsically oxygen-deficient ion-conducting layer. Resonant X-ray diffraction determined the occupancy factors of Mo atoms at the M2 and other sites to be 0.50 and 0.00, respectively. These findings provide a basis for the development of ion conductors. This combined technique would open a new avenue for in-depth investigation of the hidden chemical order/disorder in materials.

Disposable Nitric Oxide Generator Based on a Structurally Deformed Nitrite-Type Layered Double Hydroxide.

The inhalation of nitric oxide (NO), which acts as a selective vasodilator of pulmonary blood vessels, is an established medical treatment. However, its wide adoption has been limited by the lack of a convenient delivery technique of this unstable gas. Here we report that a solid mixture of FeIISO4·7H2O and a layered double hydroxide (LDH) containing nitrite (NO2-) in the interlayer spaces (NLDH) stably generates NO at a therapeutic level (∼40 ppm over 12 h from freshly mixed solids; ∼80 ppm for 5-10 h from premixed solids) under air flow (0.25 L min-1) if the NLDH has been prepared by using a reconstruction method. Mg/Al-type LDH was calcined at 550 °C to remove interlayer CO32- and then treated with NaNO2 in water to reconstruct the NLDH. This one-pot, organic solvent-free process can be performed at large scales and is suitable for mass production. Humid air promotes anion exchange between NO2- and SO42- in the solid mixture, resulting in persistent interactions of NO2- and Fe2+, generating NO. In contrast to the previously reported NLDH prepared using an anion-exchange method, the reconstructed NLDH exhibits stable and persistent generation of NO because of partial deformation of the layered structures (e.g., particle aggregation, reduced crystallinity, and enhanced basicity). Degradation of the solid mixture is suppressed under dry conditions, so that a portable cartridge column that is readily available as an NO source for emergency situations can be prepared. This work demonstrates that the interlayer nanospace of LDH serves as a reaction mediator for excellent controllability of solid-state reactions. This inexpensive and disposable NO generator will facilitate NO inhalation therapy in developing countries and nonhospital locations.

High-Temperature Pulsed-Field-Gradient 7Li-NMR Measurements of Li2CO3 over 700 K.

Understanding the transport property of Li ions is crucial for improving the performance of Li-ion batteries. To investigate the ion diffusion at high temperatures, we constructed a high-temperature pulsed-field-gradient (PFG) nuclear magnetic resonance (NMR) probe capable of measurements at temperatures >700 K. The accuracy of the sample temperature was confirmed via 79Br NMR measurements of KBr. 7Li PFG-NMR measurements of Li2CO3 were performed at temperatures up to 724 K using the probe. The apparent diffusion coefficient of Li ions in Li2CO3 was obtained experimentally.

A statistical approach for analyzing the development of 1H multiple-quantum coherence in solids.

A novel statistical approach for analyzing (1)H multiple-quantum (MQ) spin dynamics in so-called spin-counting solid-state NMR experiments is presented. The statistical approach is based on the percolation theory with Monte Carlo methods and is examined by applying it to the experimental results of three solid samples having unique hydrogen arrangement for 1-3 dimensions: the n-alkane/d-urea inclusion complex as a one-dimensional (1D) system, whose (1)H nuclei align approximately in 1D, and magnesium hydroxide and adamantane as a two-dimensional (2D) and a three-dimensional (3D) system, respectively. Four lattice models, linear, honeycomb, square and cubic, are used to represent the (1)H arrangement of the three samples. It is shown that the MQ dynamics in adamantane is consistent with that calculated using the cubic lattice and that in Mg(OH)2 with that calculated using the honeycomb and the square lattices. For n-C20H42/d-urea, these 4 lattice models fail to express its result. It is shown that a more realistic model representing the (1)H arrangement of n-C20H42/d-urea can describe the result. The present approach can thus be used to determine (1)H arrangement in solids.

An oxyhydride of BaTiO3 exhibiting hydride exchange and electronic conductivity.

In oxides, the substitution of non-oxide anions (F(-),S(2-),N(3-) and so on) for oxide introduces many properties, but the least commonly encountered substitution is where the hydride anion (H(-)) replaces oxygen to form an oxyhydride. Only a handful of oxyhydrides have been reported, mainly with electropositive main group elements or as layered cobalt oxides with unusually low oxidation states. Here, we present an oxyhydride of the perhaps most well-known perovskite, BaTiO(3), as an O(2-)/H(-) solid solution with hydride concentrations up to 20% of the anion sites. BaTiO(3-x)H(x) is electronically conducting, and stable in air and water at ambient conditions. Furthermore, the hydride species is exchangeable with hydrogen gas at 400 °C. Such an exchange implies diffusion of hydride, and interesting diffusion mechanisms specific to hydrogen may be at play. Moreover, such a labile anion in an oxide framework should be useful in further expanding the mixed-anion chemistry of the solid state.