Ordering of hydrogen bonds in high-pressure low-temperature H2O

The near K-edge structure of oxygen in liquid water and ices III, II, and IX at 0.25 GPa and several low temperatures down to 4 K has been studied using inelastic x-ray scattering at 9884.7 eV with a total energy resolution of 305 and 175 meV. A marked decrease of the preedge intensity from the liquid phase and ice III to ices II and IX is attributed to ordering of the hydrogen bonds in the proton-ordered lattice of the latter phases. Density functional theory calculations including the influence of the Madelung potential of the ice IX crystal correctly account for the remaining preedge feature. Furthermore, we obtain spectroscopic evidence suggesting a possible new phase of ice at temperatures between 4 and 50 K.     

Optical investigation of A-plane ZnO/ZnMgO multiple quantum wells grown by pulsed laser deposition

In this study, we present the optical characteristics of A-plane ZnO/ZnMgO multiple quantum wells (MQWs) with different well widths grown on R-plane sapphire substrates by pulsed laser deposition (PLD). The energy gaps of ZnO and ZnMgO have been observed by photoluminescence (PL) and absorption spectra. The electrons confined in the ZnO wells transit from the electron ground sub-band to the heavy-hole ground sub-band (noted as 11H) located at 3.40 and 3.57 eV for the ZnO/ZnMgO MQWs samples with well widths of 5.6 and 1.2 nm, respectively. The strong anisotropic polarization characteristic has been studied by polarization-dependent PL measurements. For comparison, we also calculated the transition energies of different well thicknesses varying from 1 to 6 nm. The theoretical results match quite well with the experimental values and revealing the suitable conduction band offset Q_c=0.6. The temperature dependence of PL spectra is being investigated, in the temperature range between 10 and 300 K.     

Retine Part I. Purification and Partial Characterization of Retine from Pig Liver

A modified method has been developed to purify retine from pig liver. The crude extract of retine can be separated into five fractions by paper chromatography, each of them having been tested for the effect on the proliferation of protozoal Tetrahymena Pyriformis. One of the fractions, G₃, has the strongest effect. The present results show that G₃ fraction showed positive reactions toward 2,4-dinitro-phenyl hydrazine, ethylene diamine, and ninhydrin. Other properties of the fraction has also been studied.     

Curing and pyrolysis of epoxy resins containing 2-(6-oxido-6<Emphasis Type="Italic">H</Emphasis>-dibenz(<Emphasis Type="Italic">c</Emphasis>,<Emphasis Type="Italic">e</Emphasis>)(1,2)oxaphosphorin-6-yl)-1,4-naphthalenediol or bisphenol S

This work examines the curing kinetics, thermal properties, and decomposition kinetics of diglycidyl ether of bisphenol A (DGEBA) epoxies with three different curing agents, 2-(6-oxido-6H-dibenz(c,e)(1,2)oxaphosphorin-6-yl)-1,4-naphthalenediol (ODOPN), bisphenol A (BPA), and bisphenol S (BPS). The differential scanning calorimetry curing study reveals that the curing kinetics of the DGEBA/ODOPN epoxy is first order, independent of the scan rate. The ODOPN-containing epoxy, unlike the conventional BPA one, includes a phosphorus-containing bulky pendant aromatic group and results in an increase in the glass-transition temperature of 83 K, the char yield increases by a factor of 3, and the limiting oxygen index values increase from 23 to 27. For the BPS system, the glass-transition temperature increased slightly, and both the char yield and the limiting oxygen index value increased insignificantly when the test was conducted in air. Finally, the thermogravimetric analysis decomposition study in N₂ from Ozawa's analysis demonstrates that the DGEBA/BPS epoxy has the highest activation energy, followed by the regular DGEBA/BPA system, and lastly the DGEBA/ODOPN has the lowest activation energy. The low activation energy for the ODOPN system is attributed to the initial decomposition of the phosphorus compound in the formation of an insulating layer.     

Electrochemical and structural investigations of oxide films anodically formed on ruthenium-plated titanium electrodes in sulfuric acid

The electrochemical characteristics of ruthenium oxides, formed on Ru-plated Ti electrodes in 0.5 M H₂SO₄ by potential cycling with different CV upper potential limits (E _SU), were systematically compared. The repeated potential cycling between 0.2 and 0.75 V activated the formation/reduction of surface Ru oxides with hysteretic behavior. This application of repeated CVs also modified the ability of Ru deposits for hydrogen adsorption/desorption. An irreducible Ru oxide accumulated on the electrode at potentials more positive than ca. 0.95 V, whose capacitive characteristics are applicable for electrochemical supercapacitors. This irreducible oxide was composed of an aggregate consisting of Ru in various oxidation states, bridged oxygen, OH and water in a 3D-like structure with a relatively ordered and compact nature, from the X-ray photoelectron spectroscopic and voltammetric results. The surface reconstruction of the Ru deposits induced by the repeated potential cycling with E _SU≥0.75 V was clearly observed from the SEM photographs. From the X-ray diffraction patterns, all the anodically formed Ru oxides showed an amorphous nature.     

Novel vanadium(V) compounds with a layer structure: synthesis,crystal structures,and solid state NMR spectroscopy of [(VO(2))(2)(4,4'-bpy)(0.5)(4,4'-Hbpy)(XO(4))] x H(2)O (X = P and As)

A novel vanadium(V) phosphate and the arsenate analogue, [(VO(2))(2)(4,4'-bpy)(0.5)(4,4'-Hbpy)(XO(4))].H(2)O (X = P, As; bpy = bipyridine), have been synthesized under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction. They are the first structurally characterized compounds in the vanadium(V)/4,4'-bpy/phosphate (or arsenate) systems. The two compounds are isostructural and crystallize in the triclinic space group P macro (No. 2) with a = 7.9063(3) A, b = 10.2201(4) A, c = 12.1336(5) A, alpha = 113.4652(7) degrees, beta = 95.7231(7) degrees, gamma = 94.4447(7) degrees, and Z = 2 for the phosphate, and a = 7.8843(6) A, b = 10.3686(7) A, c = 12.2606(9) A, alpha = 113.464(1) degrees, beta = 95.560(1) degrees, gamma = 94.585(1) degrees, and Z = 2 for the arsenate. The structure consists of phosphate-bridged vanadium(V) double chains linked through 4,4'-bpy ligands to form a sheet with the monoprotonated 4,4'-Hbpy(+) ligand being coordinated to the metal atom as a pendent group. The (1)H MAS NMR spectrum exhibits four resonances at 14.2, 9.5, 7.2, and 3.7 ppm with an intensity ratio close to 1:6:6:2, corresponding to three different types of protons in 4,4'-bpy and 4,4'-Hbpy(+) and one type of protons in H(2)O. The peak at 14.2 ppm can be assigned to the proton bonded to the pyridine nitrogen atom, which confirms the presence of 4,4'-Hbpy(+).     

Iron-Catalyzed Cleavage Reaction of Keto Acids with Aliphatic Aldehydes for the Synthesis of Ketones and Ketone Esters

The radical–radical coupling reaction is an important synthetic strategy. In this study, the iron-catalyzed radical–radical cross-coupling reaction based on the decarboxylation of keto acids and decarbonylation of aliphatic aldehydes to obtain valuable aryl ketones is reported for the first time. Remarkably, when tertiary aldehydes were used as carbonyl sources, ketone esters were selectively obtained instead of ketones. The gram-scale preparation of aryl ketone through this strategy was easily achieved by using only 3 mol % of the iron catalyst. As a proof-of-concept, the bioactive molecule flurprimidol was synthesized in two steps by using this strategy.     

Synthesis of selenium-containing biindolyls and their Diels–Alder reaction toward the synthesis of heteroannulated [a]- and [c]-carbazoles

We reported the first syntheses of 2- and 3-(2-(benzo[b]selenophen-2-yl)-indoles and their Diels–Alder reactions to furnish six unique annulated benzoselenphene carbazoles. This facile route can be used to synthesize selenium-containing biindolyl derivatives that possessed potential pharmaceutical activities.