Improvement of the cycle life of composite xerogel V<Subscript>2</Subscript>O<Subscript>5</Subscript>/C in aqueous LiNO<Subscript>3</Subscript> solution by addition of vinylene carbonate

The xerogel V₂O₅/C composite was synthesized by a sol-gel method, using the suspension of carbon black in the solution of crystalline V₂O₅ in hydrogen peroxide as the precursor solution. The Li⁺ intercalation/deintercalation reactions of the xerogel V₂O₅/C composite, used as an anode material of a two-electrode cell with an aqueous LiNO₃ solution as the electrolyte, was studied before and after the addition of vinylene carbonate (VC). Upon addition of vinylene carbonate in an amount of only l wt %, the coulombic capacity during galvanostatic cycling, instead of commonly observed permanent fade, displayed an initial increase and then a stable plateau.     

Oxidative desulfurization of thiophene derivatives with H<Subscript>2</Subscript>O<Subscript>2</Subscript> in the presence of catalysts based on MoO<Subscript>3</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> under mild conditions

The catalysts based on MoO₃/Al₂O₃ were synthesized and tested using aqueous hydrogen peroxide as the oxidant in the oxidative desulfurization of thiophene, benzothiophene (BT) and dibenzothiophene (DBT) into the corresponding sulfones. Among catalysts tested, 15%(MoO₃–WO₃)/Al₂O₃ prepared by a conventional impregnation method was considerably active for the oxidation of thiophene, BT and DBT, which could achieve higher than 99.2% conversions at lower reaction temperature (≤338 K). The use of hexadecyltrimethyl ammonium bromide as the phase-transfer reagent in small amounts could promote the reaction efficiently.     

Direct synthesis of hydrogen peroxide from hydrogen and oxygen over Pd-supported HNb<Subscript>3</Subscript>O<Subscript>8</Subscript> metal oxide nanosheet catalyst

A two-dimensional layered niobium oxide and its exfoliated nanosheet were examined as potential solid acid supports for direct synthesis of hydrogen peroxide from hydrogen and oxygen under intrinsically safe and noncorrosive reaction conditions. The catalytic performance strongly depended on the acid strength of the support material. The Pd-supported protonated niobium oxide nanosheet catalyst (Pd/HNb₃O₈-NS) with remarkably enhanced acidity was superior to layered Pd/KNb₃O₈ or Pd/HNb₃O₈ to promote the reaction. Hydrogen peroxide decomposition testing revealed that, although HNb₃O₈ was comparable to its exfoliated counterpart, HNb₃O₈-NS, in suppressing hydrogen peroxide decomposition without hydrogen, HNb₃O₈ was virtually ineffective in preventing hydrogen peroxide hydrogenation in the presence of hydrogen. However, compared with HNb₃O₈, HNb₃O₈-NS was found to be still effective at suppressing hydrogen peroxide hydrogenation. The different efficiency observed between HNb₃O₈ and HNb₃O₈-NS in the prevention of hydrogen peroxide hydrogenation implies that use of a highly acidic support is advantageous to effectively suppress faster and therefore more unfavorable hydrogen peroxide hydrogenation compared with decomposition. This result clearly demonstrates that the highly acidic HNb₃O₈ nanosheet can serve as an efficient solid acid support for direct synthesis of hydrogen peroxide from hydrogen and oxygen.     

Preparation of Dodecyl Dimethyl Benzyl Ammonium Bromide-Doped Cubic CaCO<Subscript>3</Subscript> with Antibacterial Properties

CaCl₂ encapsulated was placed in the hydrothermal reactor of an aqueous solution of Na₂CO₃ and dodecyl dimethyl benzyl ammonium bromide for synthesis of two samples of calcium carbonate by an improved hydrothermal method and one-pot method. Their crystal structure, morphology, chemical composition, and thermal stability of the synthesized samples of calcium carbonate were investigated by XRD, FTIR, SEM, EDS and TGDSC. The sterilization activity of the as-prepared samples was evaluated by killing of Sarcina lutea bacteria. The results indicated that the regular cube capsule-assisted calcium carbonate prepared by hydrothermal process was doped with dodecyl dimethyl benzyl ammonium bromide. Under the same condition, the spindle-shaped calcium carbonate synthesized the one-pot method was not doped with dodecyl dimethyl benzyl ammonium bromide. Among the samples of calcium carbonate, capsule-assisted calcium carbonate had shown better antibacterial effect for Sarcina lutea: in 48 h after its inhibition a zone diameter was 12.3 mm.     

The monooxidation of ethylene with hydrogen peroxide on the per-FTPhPFe<Superscript>3+</Superscript>OH/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> biomimetic

The gas-phase monooxidation of ethylene by hydrogen peroxide on a biomimetic heterogeneous catalyst (per-FTPhPFe³⁺OH/Al₂O₃) was studied under comparatively mild conditions. The biomimetic oxidation of ethylene with hydrogen peroxide was shown to be coherently synchronized with the decomposition of H₂O₂. Depending on reaction medium conditions, one of two desired products was formed, either ethanol or acetaldehyde. The kinetics and probable mechanism of ethylene transformation were studied.     

Kinetics and mechanism of decomposition of peroxide compounds in the liquid phase of the KOH-H<Subscript>2</Subscript>O<Subscript>2</Subscript>-H<Subscript>2</Subscript>O system in vessels made of various materials

Decomposition kinetics of peroxide compounds in the liquid phase of the system KOH-H₂O₂-H₂O at an initial hydrogen peroxide concentration of about 14.5 M and pH 12.7 in vessels made of Pyrex glass, polyethylene terephthalate, and 12Kh18N10T steel was studied in the temperature range from ?10 to +50°C. The main kinetic parameters of the processes under study were determined. The influence exerted by the material of the reaction vessel on the kinetics and mechanism of decomposition of peroxide compounds in the liquid phase of the system under study were determined.     

Ag nanoparticles decorated Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/chitosan nanocomposite: synthesis,characterization and application toward electrochemical sensing of hydrogen peroxide

We studied a rapid, sensitive and selective amperometric sensor for determination of hydrogen peroxide by electrodeposited Ag NPs on a modified glassy carbon electrode (GCE). The modified GCE was constructed through a step by step modification of magnetic chitosan functional composite (Fe₃O₄–CH) and high-dispersed silver nanoparticles on the surface. The resulted Ag@Fe₃O₄–CH was characterized by various analytical methods including Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy and cyclic voltammetry. The proposed sensor employed Ag@Fe₃O₄–CH/GCE as the working electrode with a linear current response to the hydrogen peroxide concentration in a wide range from 0.01 to 400 µM with a low limit of detection (LOD = 0.0038 µM, S/N = 3). The proposed sensor showed superior reproductivity, sensitivity and selectivity for the detection of hydrogen peroxide in environmental and clinical samples.     

On the stability of Al<Subscript>13</Subscript> Keggin cation in aqueous hydrogen peroxide solutions

We report the first attempt to study the behavior of the [AlO₄Al1₂(OH)₂₅(H₂O)₁₁]⁶⁺ (Al₁₃) Keggin cation (KC) in water–peroxide solutions. Addition of hydrogen peroxide into an aqueous solution containing the Al₁₃ KC reduces pH due to the acidity of hydrogen peroxide. According to the ²⁷Al NMR studies of water–peroxide solutions prepared just before the NMR experiment, with their pH adjusted to the initial value of 5.5 with aqueous NaOH, the Al₁₃ KC concentration decreases immediately once hydrogen peroxide is added to the initial system. Addition of 18.2 wt % hydrogen peroxide to the initial 0.88 mM Al₁₃ solution gives rise to a fourfold decline in Al₁₃ polyoxo cation concentration to 0.22 mM. Then, the KC concentration in the test system remains unchanged for 1 week. Large hydrogen peroxide amounts (27.9 wt % or higher) added to the initial system almost completely degrade the KC. Sodium sulfate added to the initial water–peroxide solution of Al₁₃ chloride where the hydrogen peroxide concentration is 5.5 wt % precipitates the earlier described Al₁₃ sulfate [AlO₄Al₁₂(OH)₂₅(H₂O)₁₁](SO₄)₃ · 16H₂O, where the aluminum polyoxo cation does not contain coordinated hydrogen peroxide molecules, peroxo or hydroperoxo groups as shown by X-ray diffraction.     

Catalytic decomposition of H<Subscript>2</Subscript>O<Subscript>2</Subscript> in hydrophilic solvents: The kinetic aspect

Decomposition of hydrogen peroxide in organic hydrophilic solvents, catalyzed by cobalt(II) palmitate [Co(palm)₂], was studied by the method of inhibitors.     

Kinetic study of uranium residue dissolution in ammonium carbonate media

The purpose of this study was to determine the kinetics of the dissolution of a uranium residue in ammonium carbonate media. The residue is generated in the production of medical isotopes. The effects of parameters, such as varying peroxide and carbonate concentrations, dissolution time as well as temperature on the extraction rate have been separately studied. Results indicate complete dissolution of the residue at 60 °C, after 30 min, in ammonium carbonate solution enriched with hydrogen peroxide. The yield and rate of uranium extraction were found to increase as a function of both temperature, in the range of 25–60 °C, and hydrogen peroxide concentration. The extraction process was governed by chemical reaction as the activation energy was found to be 45.5 kJ/mol. The order of reaction with respect to uranium concentration was found to be approximately first order.     

Oxidation of Diethyl Sulfide in Aqueous Solutions by Peroxynitrite and the H<Subscript>2</Subscript>O<Subscript>2</Subscript>-NO<Stack><Subscript>2</Subscript><Superscript>−</Superscript></Stack> System

It was found that nitrite anions are effective activators of hydrogen peroxide in the reaction with diethyl sulfide. The observed kinetics are consistent with the proposed intermediate formation of peroxynitrous acid (ONOOH). The rate constants for the reaction of diethyl sulfide Et₂S with the acid ONOOH (k₀ = 1.8⋅10³ L/mol⋅s) and with the anion ONOO⁻ (k₋ = 6⋅10⁻² L/mol⋅s) are respectively 10⁵ and three times higher than with hydrogen peroxide. __________ Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 41, No. 5, pp. 290–295, September–October, 2005.     

Synthesis of K<Subscript>2</Subscript>[VO(O-O)<Subscript>2</Subscript>F] and solubility and bactericidal activity of its aqueous solutions

Low-expenditure method for synthesis of K₂[VO(O-O)₂F] was developed. The solubility of this compound in water and the stability of its aqueous solutions were determined and its bactericidal activity, exceeding that of hydrogen peroxide by a factor of 1.5, was analyzed.     

WO<Subscript>3</Subscript> thin film coating from H<Subscript>2</Subscript>O-controlled peroxotungstic acid and its electrochromic properties

We prepared PTA coating solution by hot plate evaporation, N₂ bubbling evaporation, and rotary evaporation. N₂ bubbling and rotary evaporation are very efficient way to synthesize PTA which reduces the synthesis process time to 1/5, compared to hot plate evaporation method. Another strong point is that N₂ bubbling and rotary evaporation make it possible to control excess hydrogen peroxide and water contents in PTA. The PTA formula were WO₃·0.13H₂O₂·10.0H₂O for hot plate method, WO₃·0.16H₂O₂·7.1H₂O for N₂ bubbling method, and WO₃·0.15H₂O₂·3.00H₂O for rotary evaporation method. Thermal analysis and mass spectroscopy analysis show that water is evaporated at around 100 °C and hydrogen peroxide is dissociated at the range of 150 and 250 °C. Amorphous phase of WO₃ thin film prepared from rotary evaporated PTA solution has the best electrochromic property, light transmission difference from 91% at its bleached state and 5.5% colored state, and charge density of 22 mC/cm². It is thought that the control of excess hydrogen peroxide and water contents in PTA is very important to enhance the electrochromic properties of WO₃ thin film.     

Synthesis and characterization of <Emphasis Type="Italic">N</Emphasis>-hydroxyphthalimide immobilized on SiO<Subscript>2</Subscript>-coated Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles as magnetic catalyst for oxidation of benzyl alcohols and hydrocarbons

In this study, N-hydroxyphthalimide (NHPI) was successfully attached on functionalized SiO₂-coated Fe₃O₄ nanoparticles through amid bond. The sustained nanomagnetite-immobilized NHPI as a new magnetically recoverable catalyst was characterized by FT-IR, XRD, TGA, VSM, TEM and SEM techniques. The prepared catalyst exhibited high selectivity for oxidation of various benzyl alcohols and hydrocarbons in the presence of hydrogen peroxide as oxidant. The catalyst can be readily separated from the reaction mixture using an external magnet and reused several times without significant loss of its catalytic activity.     

Optimization of the preparation conditions of radioiodoepidepride: A dopamine D<Subscript>2</Subscript>receptor antagonist radioligand

Summary [¹²⁵I]iodepidepride, (s)-(-)-[(1-ethyl-2-pyrrolidinyl)methyl]-5-[¹²⁵I]-iodo-2,3-dimethoxybenzamide is the iodine substituted analogue of isoremoxipride, both of which are very potent dopamine D₂-antagonists. Epidepride was radioiodinated using different oxidizing agents such as chloramine-T, iodogen, iodogen glass frit and hydrogen peroxide. Chloramine-T is a powerful oxidizing agent compared to both iodogen and hydrogen peroxide so that the side products, especially the chlorinated epidepride, decreases the radiochemical yield. This chlorinated epidepride is minimized in the case of iodogen and iodogen glass frit and are not observed in case of the non-chlorinated oxidizing agent hydrogen peroxide. TLC and HPLC were used to analyze the reaction components and to estimate both the radiochemical yield and purity. The reaction parameters such as reaction time, pH, epidepride and oxidizing agent concentrations and the stabilty of the final product were studied to optimize the radiochemical yield and purity. The optimized radiochemical yield was about 90% and the radiochemical purity of the final product was 99.9%.     

Ammonium and caesium carbonate peroxosolvates: supramolecular networks formed by hydrogen bonds

Diammonium carbonate hydrogen peroxide monosolvate, 2NH₄⁺·CO₃²⁻·H₂O₂, (I), and dicaesium carbonate hydrogen peroxide trisolvate, 2Cs⁺·CO₃²⁻·3H₂O₂, (II), were crystallized from 98% hydrogen peroxide. In (I), the carbonate anions and peroxide solvent molecules are arranged on twofold axes. The peroxide molecules act as donors in only two hydrogen bonds with carbonate groups, forming chains along the a and c axes. In the structure of (II), there are three independent Cs⁺ ions, two of them residing on twofold axes, as are two of the four peroxide molecules, one of which is disordered. Both structures comprise complicated three‐dimensional hydrogen‐bonded networks.     

Microwave assisted low temperature synthesis of sodium zirconium phosphate (NaZr<Subscript>2</Subscript>P<Subscript>3</Subscript>O<Subscript>12</Subscript>)

Sodium zirconium phosphate [NaZr₂P₃O₁₂], a potential ceramic matrix for fixation of high level nuclear waste, was synthesized by heating the mixture of sodium carbonate [Na₂CO₃], zirconyl nitrate hydrate [ZrO(NO₃)₂·5H₂O] and ammonium dihydrogen phosphate [NH₄H₂PO₄] in air, in a resistance heated furnace and a microwave heating system respectively in the temperature range 450 to 650°C. The mixture heated for 1 h in a resistance furnace at 450°C yielded a poorly crystalline NaZr₂P₃O₁₂ [NZP]. Increasing the temperature to 650°C produced a highly crystalline product. The same mixture heated in a microwave oven at 450°C for 1 h however, yielded the most crystalline NZP.In an alternate method, the mixture of sodium dihydrogen phosphate (NaH₂PO₄), zirconium dioxide (ZrO₂) and diammonium hydrogen phosphate [(NH₄)₂HPO₄] heated in resistance furnace at 650°C for the same period did not react in air. It also did not yield the pure product at 450°C when heated in microwave assembly for 1 h.The authors thank the Board of Research in Nuclear Sciences (BRNS) of the Department of Atomic Energy (DAE) for the financial support for this work under the project No. 2000/37/19/BRNS/1959 dtd09-02-02.     

Electrocatalytic activity of hemoglobin in sodium alginate/SiO<Subscript>2</Subscript> nanoparticle/ionic liquid BMIMPF<Subscript>6</Subscript> composite film

A novel biocompatible composite film containing sodium alginate (SA), room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF₆), SiO₂ nanoparticle, and hemoglobin (Hb) was fabricated and covered on the surface of a traditional carbon paste elecrode (CPE). The immobilized Hb on the electrode surface showed good direct electrochemical behaviors, and a pair of quasi-reversible redox peaks of Hb was obtained, which indicated that the direct electron transfer of Hb with the electrode surface had been achieved. The SA/nano-SiO₂/BMIMPF₆/Hb/CPE showed dramatically electrocatalytic activity to the reduction of trichloroacetic acid, hydrogen peroxide (H₂O₂), and oxygen (O₂). The kinetic parameters for the electrocatalytic reactions were evaluated. The composite film showed the potential to the biosensor and biocatalysis.     

Nucleophilic oxidizing systems based on hydrogen peroxide for decomposition of ecotoxicants

The kinetics of oxidation of methylsulfanylbenzene and nucleophilic decomposition of diethyl 4-nitrophenyl phosphate with hydrogen peroxide in the presence of ammonium hydrogen carbonate or boric acid in aqueous, aqueous-alcoholic, micellar, and microemulsion media were studied. Quantitative parameters of the examined processes were determined, and the possibility of using hydrogen peroxide for the design of oxidative nucleophilic decontaminating systems was demonstrated.     

Takiyama法制备均分散碳酸钡粒子

Ｔａｋｉｙａｍａ法制备均分散碳酸钡粒子王世权，王泽新，伍世英，陈宗淇（青岛化工学院应用化学系，青岛，２６６０４２）关键词均分散料子，碳酸钡，Ｔａｋｉｙａｍａ法均分散体系的制备是近年来胶体化学领域中深受重视的研究课题，由于均分散体系的粒子形状相同、尺寸...