Synthesis and characterization of a new monophosphate (C<Subscript>6</Subscript>H<Subscript>16</Subscript>N<Subscript>2</Subscript>)(H<Subscript>2</Subscript>PO<Subscript>4</Subscript>)<Subscript>2</Subscript>

Chemical preparation, crystal structure, and NMR spectroscopy of a new trans-2,5-dimethylpiperazinium monophosphate are given. This new compound crystallizes in the triclinic system, with the space group P-1 and the following parameters: a = 6.5033(3), b = 7.6942(4), c = 8.1473(5) Å, α = 114.997(3), β = 92.341(3), γ = 113.136(3), V = 329.14(3) ų, Z = 1, and D_x = 1.565 g cm^?3. The crystal structure has been determined and refined to R = 0.030 and R _w(F ²) = 0.032 using 1558 independent reflections. The structure can be described as infinite [H₂PO₄] _n ^n? chains with (C₆H₁₆N₂)²⁺ organic cations anchored between adjacent polyanions to form columns of anions and cations running along the b axis. This compound has also been investigated by IR, thermal, and solid-state, ¹³C and ³¹P MAS NMR spectroscopies and Ab initio calculations.     

New organic metal β-(DOET)<Subscript>2</Subscript>FSO<Subscript>3</Subscript> · H<Subscript>2</Subscript>O: Synthesis and crystal structure

An organic metal β-(DOET)₂FSO₃ · H₂O based on a novel donor DOET (DOET is (1,4-dioxane-2,3-diyldithio)ethylenedithiotetrathiafulvalene) was synthesized and structurally characterized. Single crystals were prepared by electrochemical oxidation of DOET in the d.c. mode. The salt has a layered structure with the DOET^1/2+ radical cation layers parallel to the ab plane. The FSO ₃ ⁻ anion is equiprobably disordered over two positions relative to the center of symmetry (1/2, 0, 0). The temperature behavior of conductivity is characteristic of metals in the temperature range from 293 down to 96 K; below 96 K, an increase in resistance is observed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2387–2389, October, 2005.     

Hydrogen generation from H<Subscript>2</Subscript>O/H<Subscript>2</Subscript>O<Subscript>2</Subscript>/MnWO<Subscript>4</Subscript> system

Hydrogen gas as a clear energy resource was found to be largely bubbled from a H₂O/H₂O₂/MnWO₄ system. MnWO₄ powder was fabricated by an aqueous reaction method. The powder was characterized with X-ray diffraction (XRD), transmission electron microscope (TEM), and X-ray photoelectron spectrometry (XPS). The efficiency of the hydrogen generation increases with an increase in initial pH in the appropriate range, H₂O₂ proportion, MnWO₄ proportion, and intensity of light resource. Calcining at 400 °C for 1 h can make the MnWO₄ powder synthesized by an aqueous reaction more effective for H₂ generation and more stable in higher initial pH. The MnWO₄ catalyst shows a long-term stability for photocatalytic H₂ generation. A mechanism was suggested for the hydrogen generation from the H₂O/H₂O₂/MnWO₄ system together with XPS analysis.     

Electrochemical deposition of Bi<Subscript>2</Subscript>Te<Subscript>3</Subscript> for thermoelectric microdevices

The electrolyses of solutions of bismuth oxide and tellurium oxide in nitric acid with molar ratios of Bi:Te=3:3–4:3 lead to cathodic deposits of films of bismuth telluride (Bi₂Te₃), an n-type semiconductor. Current densities of 2–5 mA/cm² were applied. Voltammetric investigations showed that Bi₂Te₃ deposition occurred at potentials more negative than −0.125 V (Ag/AgCl, 3 M KCl). The deposit was identified as bismuth telluride (γ-phase) by X-ray analysis. Hall-effect measurements verified the n-type semiconducting behaviour. The films can be deposited in microstructures for thermoelectric microdevices like thermoelectric batteries or thermoelectric sensors.     

A review on nanomaterial-based electrochemical sensors for H<Subscript>2</Subscript>O<Subscript>2</Subscript>, H<Subscript>2</Subscript>S and NO inside cells or released by cells

The incorporation of nanomaterials into electrochemical sensors is an attractive approach towards the improvement of the sensitivity of amperometry and also can provide improved sensor selectivity and stability. This review (with 137 references) details the current state of the art and new trends in nanomaterial-based electrochemical sensing of hydrogen peroxide (H₂O₂), hydrogen sulfide (H₂S) and nitric oxide (NO) in cells or released by cells. The article starts with a discussion of the significance of the three analytes, and this is followed by three sections that summarize the electrochemical detection schemes for H₂O₂, H₂S and NO. Each section first summarizes the respective physiological roles, and then reviews electrochemical sensors based on the use of carbon nanomaterials, noble metal nanomaterials, metal oxide nanomaterials, and layered doubled hydroxides. The materials are compiled in three tables along with figures of merit for the various sensors.

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Graphical abstract Nanomaterial-based electrochemical sensors for Reactive oxygen species (H₂O₂), Reactive nitrogen species (NO) and Reactive hydrogen sulfide species (H₂S) inside cells or released by cells.

     

Second Dissociation Constant of H<Subscript>2</Subscript>Te and the Absorption Spectra of HTe<Superscript>–</Superscript>, Te<Superscript>2–</Superscript> and Te<Subscript>2</Subscript><Superscript>2–</Superscript> in Aqueous Solution

We have measured the second acid dissociation constant, K _2a , at several ionic strengths for hydrogen telluride (H₂Te) using the Charge Transfer to Solvent (CTTS) uv spectra of its anions HTe⁻ and Te²⁻. Since it is produced in our solutions, we have also determined the spectra of Te₂ ²⁻ both in the uv and in the visible regions. At 25 ^∘C, K _2a = (1.28 ± 0.02) × 10⁻¹² by extrapolation to zero ionic strength. Its value at an ionic strength equal to 0.5 mol.dm^-3 was estimated to be (8.7 ± 0.2) × 10⁻¹². The solution thermodynamics of these species are also discussed and comparisons are made to related acids.     

Study on chemisorption of H<Subscript>2</Subscript>, O<Subscript>2</Subscript>, CO and C<Subscript>2</Subscript>H<Subscript>4</Subscript>on Pt-Ag/SiO<Subscript>2</Subscript>catalysts by microcalorimetry and FTIR

Adsorption microcalorimetry has been employed to study the interaction of ethylene with the reduced and oxidized Pt-Ag/SiO₂catalysts with different Ag contents to elucidate the modified effect of Ag towards the hydrocarbon processing on platinum catalysts. In addition, microcalorimetric adsorption of H₂, O₂, CO and FTIR of CO adsorption were conducted to investigate the influence of Ag on the surface structure of Pt catalyst. It is found from the microcalorimetric results of H₂and O₂adsorption that the addition of Ag to Pt/SiO₂leads to the enrichment of Ag on the catalyst surface which decreases the size of Pt surface ensembles of Pt-Ag/SiO₂catalysts. The microcalorimetry and FTIR of CO adsorption indicates that there still exist sites for linear and bridged CO adsorption on the surface of platinum catalysts simultaneously although Ag was incorporated into Pt/SiO₂. The ethylene microcalorimetric results show that the decrease of ensemble size of Pt surface sites suppresses the formation of dissociative species (ethylidyne) upon the chemisorption of C₂H₄on Pt-Ag/SiO₂. The differential heat vs. uptake plots for C₂H₄adsorption on the oxygen-preadsorbed Pt/SiO₂and Pt-Ag/SiO₂catalysts suggest that the incorporation of Ag to Pt/SiO₂could decrease the ability for the oxidation of C₂H₄.     

Transition metal salts of H<Subscript>4</Subscript>PMo<Subscript>11</Subscript>VO<Subscript>40</Subscript> for efficient H<Subscript>2</Subscript>S removal in the liquid redox process

Several transition metal (Cu²⁺, Fe³⁺, Zn²⁺, Mn⁴⁺, and Cr⁶⁺) salts of H₄PMo₁₁VO₄₀ were prepared and their solutions were used initially for H₂S removal in the liquid redox process. H₂S removal tests were performed by dynamic absorption experiments. Among these polyoxometalates, that with the Cu²⁺ cation was found to have pronounced H₂S removal performance with the removal efficiency of up to 98%. The relevant oxidative desulfurization mechanism and the role of Cu²⁺ were studied.     

Electrochemical Behavior of Cobalt-Dimethylglyoxime Complex Co(DMG)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript> in the Carbon Dioxide Reduction Process

The electrochemical behavior of a complex of cobalt with dimethylglyoxime Co(DMG)₂(H₂O)₂ is studied by cyclic voltametry. Peaks corresponding to redox transitions Co(III)/Co(II) and Co(II)/Co(I) are observed in the potential region 0.4 to ?1.8 V (Ag/AgCl). The product of reduction of the initial complex interacts with carbon dioxide to form a stable compound, probably an intermediate product of electrocatalytic reduction of CO₂ to CO in the presence of N₄-macrocyclic complexes of cobalt.     

Structure and some properties of [UO<Subscript>2</Subscript>(SeO<Subscript>4</Subscript>)(C<Subscript>5</Subscript>H<Subscript>12</Subscript>N<Subscript>2</Subscript>O)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)]

The complex [UO₂(SeO₄)(C₅H₁₂N₂O)₂(H₂O)] (I) was synthesized and studied by thermal analysis, IR spectroscopy, and X-ray crystallography. The crystals are orthorhombic: a = 13.1661(3) Å, b = 16.4420(5) Å, c = 17.4548(6) Å, Pbca, Z = 8, R = 0.0423. The structural units of crystal I are chains with the composition coinciding with that of the compounds of the AB₂M ₃ ¹ crystal chemical group of the uranyl complexes (A = UO ₂ ²⁺ , B² = SeO ₄ ^2? , M¹ = C₅H₁₂N₂O and H₂O).     

PdCl<Subscript>2</Subscript>/DABCO-catalyzed direct arylation of 2-hydroxybenzaldehydes in H<Subscript>2</Subscript>O

In this paper the successful application of DABCO both as base and as ligand for efficient coupling reactions of aryl iodides and bromides with 2-hydroxybenzaldehydes in the presence of catalytic amounts of PdCl₂ in water as solvent was introduced.     

Electrochemical Methods for Studying Transport Properties and the Type of Ionic Conduction in Solid Electrolytes Based on CaPr<Subscript>2</Subscript>S<Subscript>4</Subscript> and Ca(Ba)Sm<Subscript>2</Subscript>S<Subscript>4</Subscript>

The theoretical feasibility of sulfide ion transport in phases based on MeLn₂S₄ (Me = Ca, Ba; Ln = Sm, Pr) is considered. Regions of solid solutions on the basis of ternary compounds are determined. A systematic investigation of phases is performed with the application of a variety of electrochemical methods, specifically, the conductimetry, emf in chemical concentration cells with and without transport, and Tubandt methods.__________Translated from Elektrokhimiya, Vol. 41, No. 6, 2005, pp. 707–713.Original Russian Text Copyright © 2005 by Ushakova, Kalinina, Fominykh, Yurlov, Murin.Published on the basis of a report delivered at the VII Meeting on Fundamental Problems in Solid-State Ionics (Chernogolovka-2004).     

Kinetic method for acetylsalicylic acid determination based on its inhibitory effect upon the catalytic decomposition of H<Subscript>2</Subscript>O<Subscript>2</Subscript>

The catalytic reaction of catalase was investigated, by means of a Clark oxygen sensor, in the presence of various concentrations of acetylsalicylic acid. Michaelis-Menten kinetic parameters were determined from Lineweaver-Burk plots, obtained in the absence and in the presence of the inhibitor. The inhibition pattern, suggested by the Lineweave-Burk plots, corresponds to a fully mixed inhibition mechanism. A kinetic method, based on the indicator reaction: , was developed for the quantitative determination of acetylsalicylic acid. Calibration graphs of the reciprocal value of first-order rate constant versus acetylsalicylic concentration covered the concentration range (2.99–19.98)×10^–4 mol/L, while the detection limit was 4.12×10^–4 mol/L acetylsalicylic acid with a standard deviation of 2.1×10^–5 mol/L.     

Kinetics of processes occurring at a H<Subscript>3</Subscript>PW<Subscript>12</Subscript>O<Subscript>40</Subscript>/Pt,H<Subscript>2</Subscript> interface depending on the platinum content on the electrode

Kinetics of processes occurring at H⁺/solid electrolyte/Pt, H₂ three-phase interface are studied subject to the platinum content on the electrode. The study was performed with model electrochemical cells PbO₂/H₃PW₁₂O₄₀/Pt with different platinum content at the working electrode that consisted of platinum deposited onto the E-Tek LT1200-N carbon-nanotubes paper. On the basis of the obtained results, the occurring processes were practically fully separated. It is shown by the analyzing of relaxation curves that there exist at least two processes in the system: the faster one corresponds to the hydrogen reaction; the slower, to the oxygen one. The rates of both processes depend on the platinum content at the working electrode; they have an extreme at the platinum concentration of 0.5 mg/cm². Impedance data allowed revealing the processes’ limiting stages. The experimental data allowed suggesting that at low platinum content the relaxation time is determined by the electrochemical reaction rate; at higher content, by gas diffusion through the platinum dense layer.     

The use of the concept of solvation excesses for studying the mutual distribution of solution component particles in the H<Subscript>2</Subscript>O-KCl-NaCl and H<Subscript>2</Subscript>O-KNO<Subscript>3</Subscript>-NaNO<Subscript>3</Subscript> systems

The data on component activities and salt solubilities were analyzed to determine solvation excesses in the H₂O-KCl-NaCl and H₂O-KNO₃-NaNO₃ systems. Some rules governing the solvation of ions were discussed.     

Study on the cluster of floating dross before nucleating during hot-dipping process

At present, hot-dipping anticorrosion metalliccoating on the surface of steel base is the main methodto prevent atmospheric corrosion of steel. With thechange of atmospheric environment, the traditionalidea of hot-dipping pure Zn cladding already does not…     

Synthesis of nanocrystalline ZnO by the thermal decomposition of [Zn(H<Subscript>2</Subscript>O)(O<Subscript>2</Subscript>C<Subscript>5</Subscript>H<Subscript>7</Subscript>)<Subscript>2</Subscript>] in isoamyl alcohol

It was studied how the conditions of heat treatment of a [Zn(H₂O)(O₂C₅H₇)₂] solution in isoamyl alcohol at 120–140°C for 2–60 min affect the precursor decomposition mechanism and the characteristics of the obtained nanocrystalline zinc oxide. In all the cases, the product was a crystalline substance with the wurtzite structure and a size of crystallites of 14–18 nm, which was independent of the synthesis conditions. The thermal behavior and microstructure of the separated and dried nanostructured ZnO powder were investigated. It was determined how the duration and temperature of the heat treatment of the precursor solution affects the microstructure of ZnO coatings dip-coated onto glass substrates using dispersions produced at 120 and 140°C. The nanosized ZnO application procedure was shown to be promising for creating a gas-sensing layer of chemical gas sensors for detecting 1% H₂ (\(R_0 /R_{H_2 } \) was 58 ± 2 at an operating temperature of 300°C) and 4 ppm NO₂ (\(R_{NO_2 } /R_0\) were 15 ± 1 and 1.9 ± 0.1 at operating temperatures of 200 and 300°C, respectively).     

X-ray photoelectron study of the interaction of H<Subscript>2</Subscript> and H<Subscript>2</Subscript>+O<Subscript>2</Subscript> mixtures on the Pt/MoO<Subscript>3</Subscript> model catalyst

The effects of H₂ and H₂ + O₂ gas mixtures of varying composition on the state of the surface of the Pt/MoO₃ model catalyst prepared by vacuum deposition of platinum on oxidized molybdenum foil were investigated by X-ray photoelectron spectroscopy (XPS) at room temperature and a pressure of 5–150 Torr. For samples with a large Pt/Mo ratio, the XP spectrum of large platinum particles showed that the effect of hydrogen-containing mixtures on the catalyst was accompanied by the reduction of molybdenum oxide. This effect results from the activation of molecular hydrogen due to the dissociation on platinum particles and subsequent spill-over of hydrogen atoms on the support. The effect was not observed at low platinum contents in the model catalyst (i.e., for small Pt particles). It is assumed for the catalyst that the loss of its hydrogen-activating ability is a consequence of the formation of platinum hydride. Possible participation of platinum hydride as intermediate in hydrogen oxidation to H₂O₂ is discussed.     

The stability and structure of (N<Subscript>2</Subscript>)<Subscript>j</Subscript>(H<Subscript>2</Subscript>O)<Subscript>i</Subscript> and (Ar)<Subscript>j</Subscript>(H<Subscript>2</Subscript>O)<Subscript>i</Subscript> clusters

The stability and structure of water clusters absorbing nitrogen molecules or argon atoms was analyzed by molecular dynamics simulation at 233 K. The (?μ/?i)_{V, T} derivative of the chemical potential, a value characterizing the stability of a cluster with respect to its size, depends linearly on the number of molecules i. According to this criterion, the clusters under study become stable near i = 40. The average length of H-bonds increases monotonically in the growing cluster of pure water and exhibits oscillatory behavior if the growing cluster contains N₂ molecules or Ar atoms. The number of H-bonds per molecule oscillates between one and six as the cluster size changes. These oscillations are damped in pure water and sustained for clusters containing impurities, especially argon.     

Dimethyl phthalate (DMP) degradation in aqueous solution by gamma-irradiation/H<Subscript>2</Subscript>O<Subscript>2</Subscript>

This work includes the applications of radiation processing to decompose dimethyl phthalate (DMP) with gamma and gamma/H₂O₂ processes. Changes in amounts of DMP, dissolved oxygen, total acidity and formaldehyde with irradiation dose were followed. The qualitative analysis of the DMP and the intermediates were determined by using a gas chromatography combined to mass spectrometry and ion chromatography. The results indicated that degradation rate of DMP was affected by H₂O₂ concentration, irradiation dose and removal efficiency of 25 mg L^?1 DMP can reach 100% for 1.42 kGy irradiation dose in the concentration of 4.8 mM H₂O₂, respectively.