Quaternary Wurtzitic Nitrides in the System ZnGeN₂–GaN: Powder Synthesis, Characterization, and Potentiality as a Photocatalyst

We developed a new quaternary wurtzitic nitride system by formation of the solid solution between ZnGeN₂ and GaN. Near stoichiometric and monophasic powder samples in the composition Zn_1–<i>x</i>Ge_1–<i>x</i>Ga_2<i>x</i>N₂ (<i>x</i> ≤ 0.50) were obtained by the reduction–nitridation synthesis conducted at 900 °C. The results of crystal structure refinement clearly revealed that the cation ordering in the structure of ZnGeN₂ (<i>Pna</i>2₁) tends to disappear by introducing Ga into the lattice, and the structure transforms to a simple wurtzite phase (<i>P</i>6₃<i>mc</i>) with the composition of <i>x</i> ≥ 0.33. The observed structural evolution was further confirmed by the results of ⁷¹Ga solid-state nuclear magnetic resonance (NMR) spectroscopy, showing an unsplit single peak observed for <i>x</i> ≥ 0.33. The dissolution of GaN into ZnGeN₂ also resulted in a marked narrowing of the band gap, from the ultraviolet region of 3.42 eV to the visible-light range of 3.02–3.05 eV, depending scarcely on the value of <i>x</i>. The results of photocatalytic test reactions for water splitting showed that the synthesized Zn_1–<i>x</i>Ge_1–<i>x</i>Ga_2<i>x</i>N₂ solid solution possessed the H₂ evolution rate of 2.8–3.6 μmol/h and the relatively high O₂ evolution rate of 100.4–126.6 μmol/h, as well as the capability for overall water splitting under the visible-light irradiation of λ > 400 nm

Electron Localization of Polyoxomolybdates with ε‑Keggin Structure Studied by Solid-State ⁹⁵Mo NMR and DFT Calculation

We report electron localization of polyoxomolybdates with ε-Keggin structure investigated by solid-state ⁹⁵Mo NMR and DFT calculation. The polyoxomolybdates studied are the basic ε-Keggin crystals of [Me₃NH]₆[H₂Mo₁₂O₂₈(OH)₁₂{MoO₃}₄]·2H₂O (<b>1</b>), the crystals suggested to have a disordered {ε-Mo₁₂} core of [PMo₁₂O₃₆(OH)₄{La­(H₂O)_2.75Cl_1.25}₄]·27H₂O (<b>2</b>), and the paramagnetic Keggin crystals of [H₂Mo₁₂O₃₀(OH)₁₀{Ni­(H₂O)₃}₄]·14H₂O (<b>3</b>). The spectra of ⁹⁵Mo static NMR of these samples were measured under moderate (9.4 and 11.7 T) and ultrahigh magnetic fields (21.8 T). From spectral simulation and quantum chemical calculation, the NMR parameters of the chemical shift and quadrupole interactions for ⁹⁵Mo were estimated. By the analysis based on the result for <b>1</b>, it was found for <b>2</b> that although the {ε-Mo₁₂} core is disordered, the eight d¹ electrons in it are not completely localized on four Mo–Mo bonds. Furthermore, it was shown for <b>3</b> that the d¹ electrons are localized to make the Mo–Mo bonds, while the unpaired electrons are also almost localized on the paramagnetic Ni^II ions

NMR, ESR, and Luminescence Characterization of Bismuth Embedded Zeolites Y

Thermal treatment of bismuth-embedded zeolite Y yields luminescent Bi⁺ substructures without the formation of metallic nanoparticles. The structural and photophysical features of the resulting zeolite Y have been thoroughly characterized by using extensive experimental techniques including nuclear magnetic resonance (NMR), electron spin resonance (ESR), 2-dimentional excitation–emission and absorption spectra. NMR and ESR results indicate that some Al and oxygen are expelled from the zeolite Y framework after undergoing thermal treatment. The detailed analyses of luminescence and absorption spectra, coupled with TDDFT calculations, suggest that all Bi⁺ substructures (i.e., Bi₄⁴⁺, Bi₃³⁺, Bi₂²⁺, and Bi⁺) are optically active in the near-infrared (NIR) spectral range. It is found that Bi⁺, Bi₂²⁺, Bi₃³⁺, and Bi₄⁴⁺ units result in NIR emissions peaking at ca. 1050, 1135, 1145, and 1240/1285 nm, respectively. The emission lineshapes under diverse excitation wavelengths greatly depend on the Bi concentration and annealing temperature, as a result of the change in the relative concentration and the spatial distribution, as well as local structural features of Bi active species. Specifically, the above analyses imply that the reducing agents for Bi³⁺ are water molecules as well as framework oxygen. These findings represent an important contribution to the understanding of the processes involved in the formation of Bi⁺ and of the luminescence mechanisms of Bi⁺ substructures in zeolite Y frameworks, which are not only helpful for the in-depth understanding of experimentally observed photophysical properties in other Bi-doped materials but also important for the development of novel photonic material systems activated by other p-block elements

Indolylmaleimide Derivative IM-17 Shows Cardioprotective Effects in Ischemia-Reperfusion Injury

We previously developed <b>IM-54</b> as a novel type of inhibitor of hydrogen-peroxide-induced necrotic cell death. Here, we examined its cell death inhibition profile. <b>IM-54</b> was found to selectively inhibit oxidative stress-induced necrosis, but it did not inhibit apoptosis induced by various anticancer drugs or Fas ligand, or necroptosis. <b>IM-17</b>, an IM derivative having improved water-solubility and metabolic stability, was developed and confirmed to retain necrosis-inhibitory activity. <b>IM-17</b> showed cardioprotective effects in an isolated rat heart model and an <i>in vivo</i> arrhythmia model, suggesting that IM derivatives may have therapeutic potential

Ce-Doped La₃Si_6.5Al_1.5N_9.5O_5.5, a Rare Highly Efficient Blue-Emitting Phosphor at Short Wavelength toward High Color Rendering White LED Application

Phase pure nondoped and Ce doped La₃Si_6.5Al_1.5N_9.5O_5.5 (Al containing La N-phase) samples have been obtained by solid-state reaction synthesis for the first time. 1% Ce-doped La₃Si_6.5Al_1.5N_9.5O_5.5 phosphor displays a broad excitation band ranging from UV to 410 nm, with a maximum at 355 nm. UV light excitation results in a narrow Ce³⁺ 5d-4f emission band (fwhm = 68 nm) centered at 418 nm. The emission can be tuned from 417 nm at 0.5% Ce to 450 nm at 50% Ce. A high internal quantum efficiency up to 84% is achieved for a 1% Ce doped sample, which has CIE chromaticity coordinates of <i>x</i> = 0.157 and <i>y</i> = 0.069, close to the NTSC blue standard (<i>x</i> = 0.155; <i>y</i> = 0.070). Compared to La₃Si₈O₄N₁₁:Ce phosphor, the quantum efficiency and thermal stability have been enhanced for La₃Si_6.5Al_1.5N_9.5O_5.5:Ce phosphor without shifting the emission peak wavelength. La₃Si_6.5Al_1.5N_9.5O_5.5:Ce shows less thermal quenching than La₃Si₈O₄N₁₁:Ce and no shift or change in the shape of emission spectra with increasing the temperature from 4 to 573 K. These results show that La₃Si_6.5Al_1.5N_9.5O_5.5:Ce is more efficient than any other (oxy-)­nitride phosphor with an emission in the short wavelength blue region (400–450 nm). A white LED was fabricated using the La₃Si_6.5Al_1.5N_9.5O_5.5:5Î as a blue phosphor. The high color rendering index (Ra = 93.2, R9 = 91.4, and R12 = 89.5) obtained shows that the phosphor is a very promising conversion phosphor for white LEDs

Dynamic Breathing of CO₂ by Hydrotalcite

The carbon cycle of carbonate solids (e.g., limestone) involves weathering and metamorphic events, which usually occur over millions of years. Here we show that carbonate anion intercalated layered double hydroxide (LDH), a class of hydrotalcite, undergoes an ultrarapid carbon cycle with uptake of atmospheric CO₂ under ambient conditions. The use of ¹³C-labeling enabled monitoring by IR spectroscopy of the dynamic exchange between initially intercalated ¹³C-labeled carbonate anions and carbonate anions derived from atmospheric CO₂. Exchange is promoted by conditions of low humidity with a half-life of exchange of ∼24 h. Since hydrotalcite-like clay minerals exist in Nature, our finding implies that the global carbon cycle involving exchange between lithosphere and atmosphere is much more dynamic than previously thought

Naked-Eye Discrimination of Methanol from Ethanol Using Composite Film of Oxoporphyrinogen and Layered Double Hydroxide

Methanol is a highly toxic substance, but it is unfortunately very difficult to differentiate from other alcohols (especially ethanol) without performing chemical analyses. Here we report that a composite film prepared from oxoporphyrinogen (OxP) and a layered double hydroxide (LDH) undergoes a visible color change (from magenta to purple) when exposed to methanol, a change that does not occur upon exposure to ethanol. Interestingly, methanol-induced color variation of the OxP-LDH composite film is retained even after removal of methanol under reduced pressure, a condition that does not occur in the case of conventional solvatochromic dyes. The original state of the OxP-LDH composite film could be recovered by rinsing it with tetrahydrofuran (THF), enabling repeated usage of the composite film. The mechanism of color variation, based on solid-state ¹³C–CP/MAS NMR and solution-state ¹³C NMR studies, is proposed to be anion transfer from LDH to OxP triggered by methanol exposure