Hydrogen sorption characteristics of magnesium-based composites with addition of Mg<Subscript>2</Subscript>Ni<Subscript>0.7</Subscript>Co<Subscript>0.3</Subscript> and graphite

Magnesium-based composites of 75 wt% Mg — (10, 15, 20) wt% Mg2Ni0.7Co0.3 — (15, 10, 5) wt% C mechanically activated for 30 min under argon in a planetary mill, were obtained. Their absorption-desorption characteristics were investigated under a pressure P = 1 MPa and temperatures of 623, 573, 473, 423 and 373 K. Desorption was carried out at 623 K and 573 K and a pressure of 0.15 MPa. All the three composites showed improved hydriding kinetics as compared to pure magnesium. However, the desorption temperature was somewhat higher than needed for practical application.      

Protolytic properties of the structurally rigid analogs of 2,6-distyrylpyridine. Widening the pH sensitivity range by the photochemical E→Z isomerisation and introduction of substituents capable to protolytic interactions

Protolytic interactions in the series of prospective fluorescent ratiometric wide-range pH indicators — structurally rigid analogs of 2,6-distyrylpyridine — (3E,5E)-3,5-dibenzylidene-8-phenyl-1,2,3,5,6,7-hexahydrodicyclopentano[b,e]pyridine — were investigated. The pyridine nitrogen atom basicity in these compounds is significantly lower in comparison with that of unsubstituted heterocycle and 2,6-distyrylpyridine. The photochemical E→Z photoisomerization and the side benzene rings substituents influence on the acid-base equilibria were studied. The complex multi-stage mechanism of the acid-base interactions of the polysubstituted compounds was elucidated. The most significant spectral effects were typical to the N,N-dialkylamino substituted compounds of the investigated series. The widest pH sensitivity interval covering nearly the full range of 0–14 units was demonstrated for compounds with both proton donor and proton acceptor substituents.      

Alkaline hydrolysis of brilliant green in mixed cationic surfactant systems

Kinetic measurements were performed for the alkaline hydrolysis of brilliant green — a triphenylmethane dye used as a model compound for probing micellar rate effects. This reaction was studied both in the presence of tetradecyltrimethylammonium bromide (TTAB) and tetradecyltriphenylphosphonium bromide (TTPPBr) and also in binary mixtures of these surfactants at different mole fractions of each. All rate surfactant profiles were analyzed using the pseudo-phase model in order to obtain the regression parameters, including binding constants and rate constants in the micellar pseudo-phase. The reaction was catalyzed by both surfactants. The catalytic factor increases from about 10 for pure TTPPBr to about 38 for pure TTAB. Binding of BG to micellar surface is greater in pure TTAB than in pure TTPPBr but significantly reduced in the surfactant mixtures than in pure components. Reduction of the binding constant becomes more significant as the mole fraction of TTAB is increased in the mixture. The kinetic data have been analyzed in terms of models of Piszkiewicz and Raghavan-Srinivasan which are in good agreement.      

Catalytic degradation of methylene blue in aqueous solutions over Ni- and Co- oxide systems

The oxidative catalytic degradation of the cationic dye methylene blue (MB) with NaOCl in aqueous solutions was studied using individual and iron modified Ni- and Co-oxide systems as catalysts. The adsorption extent and the contribution of the uncatalyzed oxidation on the overall degree of MB were determined. The results indicate that methylene blue—a representative of a class of dyestuffs resistant to biodegradation—could be successfully decolorized and degraded using nickel and cobalt oxide catalysts at room temperature. The highest catalytic activity manifests in the Co-oxide system which is consistent with the adsorption data. The oxidative degradation reaction proceeds via first-order kinetics. Temperature has a relatively small effect on the methylene blue degradation kinetics. The results obtained reveal that the catalysts investigated are suitable for oxidative destruction of methytlene blue dye in wastewaters.      

Efficient and solvent-free synthesis of 1-amidoalkyl-2-naphthols using <Emphasis Type="Italic">N,N,N’,N’</Emphasis>-tetrabromobenzene-1,3-disulfonamide

N,N,N,’N’-Tetrabromobenzene-1,3-disulfonamide [TBBDA] is found to be a reusable catalyst for efficient synthesis of various amidoalkyl naphthols from β-naphthol, aromatic aldehydes and urea in good to high yields under solvent-free conditions.      

Metathesis transformations of unsaturated derivatives of β-diketones

Selected β-diketones bearing unsaturated derivatives have been demonstrated to undergo homo-metathesis and cross-metathesis with selected olefins in the presence of Grubbs catalysts. The reactions led to respective homo- and cross-metathesis products mainly with good yields and selectivities.      

Isomers in the chemistry of mercury coordination compounds

The coordination chemistry of mercury is an extremelybroad field, as shown by a survey covering the crystallographic and structural data of over 550 examples. About 12% of those complexes exist as isomers and are summarised and classified in this review. Included are distortion (73%), polymerisation (20.6%), coordination number (3.2%) and ligand (3.2%) isomerism. These are discussed in terms of the coordination around the mercury atoms, and correlations are drawn between donor atoms, bond distances and bond angles. Distortion isomers, differing only by the degree of distortion in the Hg — L and L — Hg — L angles, are the most common. These isomers are discussed and compared with those found in the chemistry of zinc and cadmium.      

Ionic liquid promoted Diels-Alder Reaction between anthrone and maleimides

Ionic liquids (IL) are gaining importance as green solvents. Imidazolium ionic liquid [bmim]⁺[Cl]⁻, an environmentally benign solvent, was found to promote the Diels-Alder reaction between anthrone and maleimides at room temperature with excellent yields. The ionic liquid played a dual role as solvent and catalyst.      

A direct method for the decontamination of a fly ash amended wet soil,artificially polluted with dioxins

We report hereby the first method of direct treatment of a wet soil containing toxic polychloroderivatives. Using a system with metallic Ca and 5% Rh fixed on charcoal in methanol, soil samples artificially polluted with fly ash containing polychloro-dibenzodioxins (PCDDs), polychloro-dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (co-PCBs), and having 69.2% to 84.6% moisture content, were successfully treated and decontaminated. This treatment afforded excellent hydrodechlorination yields for the 29 most toxic congeners of PCDDs, PCDFs and PCBs (98.3% degradation yield based on toxic equivalent quotient — or TEQ) after a 24 h treatment, at room temperature.      

Cloud point extraction-preconcentration and flame atomic absorption spectrometric determination of low levels of zinc in water and blood serum samples

A simple, sensitive and selective flotation method is described for the preconcentration and atomic absorption spectrometric determination of zinc ion in water and blood samples. At a solution pH of 5.2, 4-(2-pyridylazo-resorcinol) and Triton X-114 were used as hydrophobic ligand and non-ionic surfactant, respectively. The chemical variables affecting the preconcentration process were optimized. Under the optimized experimental conditions, the selective preconcentration and determination of as low zinc concentration as 6.5 μg L⁻¹ can be made. The proposed method was successfully applied to the preconcentration and low-level determination of zinc in different water and blood serum samples.      

Electrospinning of the hydrophilic poly (2-hydroxyethyl methacrylate) and its copolymers with 2-ethoxyethyl methacrylate

The goal was to electrospin 2-hydroxyethyl methacrylate — based biocompatible polymers and prepare submicron fibres (nanofibers) for biomedicinal applications. Syntheses of poly(2-hydroxyethyl methacrylate) (HEMA) and its copolymer with 2-ethoxyethyl methacrylate (EOEMA), and their characterization by viscometry and molecular weight are described. Their relation to electrospinning is discussed. Electrospinning of HEMA homopolymer from water-ethanol is successful for molecular weights 6.31 × 10⁵ and 1.80 × 10⁶ g/mol. Electrospinning of HEMA/EOEMA copolymers is feasible from ethanol.      

Uncertainty of nitrate and sulphate measured by ion chromatography in wastewater samples

This paper presents an evaluation of measurement uncertainty regarding the results of anion (nitrate and sulphate) concentrations in wastewater. Anions were determined by ion chromatography (EN ISO 10304-2, 1996). The major sources of uncertainty regarding the measurements’ results were identified as contributions to linear least — square or weighted regression lines, precision, trueness, storage conditions, and sampling. Determination of anions in wastewater is very important for the purification procedure, especially the amount of nitrate in waste and potable waters. The determined expanded uncertainty was 6.1 % for nitrate anions and 8.3 % for sulphate anions. The difference between measurement uncertainties determined by the two methods, the weighted and linear least — square methods, is negligible.      

Capillary electrophoretic separation and characterizations of CdSe quantum dots

We have developed a capillary electrophoresis method to characterize the QD surface ligand interactions with various surfactant systems. The method was demonstrated with 2–5 nm CdSe nanoparticles surface-passivated with trioctylphosphine oxide (TOPO). Water solubility was accomplished by surfactant-assisted phase transfer via an oil-in-water microemulsion using either cationic, anionic, or non-ionic surfactants. Interaction between the QD surface ligand (TOPO) and the alkyl chain of the surfactant molecule produces a complex and dynamic surface coating that can be characterized through manipulation of CE separation buffer composition and capillary surface modification. Additional characterization of the QD surface ligand interactions with surfactants was accomplished by UV-VIS spectroscopy, photoluminescence, and TEM. It is anticipated that studies such as these will elucidate the dynamics of QD surface ligand modifications for use in sensors.      

Optimization study of the catalytic activity of DNAzymes based on telomeric G-quadruplexes

Optimization studies of the procedure for peroxidase activity measurements with DNAzymes based on telomeric sequences and colorimetric indicator reactions are reported. Effect of metal cation, nature and concentration of surfactant, as well as thermal treatment of G-quadruplex sample are investigated. Nature of metal cation exhibited modest influence on the system performance. Great improvement of enzymatic activity of the telomeric quadruplexes in the presence of Brij 58 surfactant was observed. Further improvement of catalytic activity of the system based on human telomeric sequence was attained by applying a thermal treatment (heating/rapid cooling) procedure to prepare G-quadruplex/hemin complexes.      

Copper (II) chloride / tetrabutylammonium bromide catalyzed oxidation of 2,6-diisopropylnaphthalene and 4,4′-diisopropylbiphenyl

The oxidation processes of 2,6-diisopropylnaphthalene and 4,4′-diisopropylbiphenyl with oxygen in the presence of a catalyst, composed of copper(II) chloride and tetrabutylammonium bromide, were investigated. It was found that, in essence, only one isopropyl group undergoes oxidation, and obtained mixtures contained mainly peroxide, alcohol, ketone and only small amounts of hydroperoxide.      

Simple determination of nonionic surfactants in highly-polluted aqueous samples

This study examined the direct spectrometric method for determining non-ionic surfactants in highly-polluted samples (i.e., soil leachates) containing high concentrations of humic acids. Meso-tetra-(3,5-dibromo-4-hydrooxyphenyl)-porphyrin served as a coloration agent. The method was tested by use of two polyethoxylate/polypropoxylate — based non-ionic surfactants: Triton CF-21 containing aromatic groups in the structure and Novanik 1047A containing only linear hydrocarbon chains. The main goal was to quantify the influence of interfering species to the results. A test for coincidence of regression lines was employed for objective evaluation of the humic acid influence on the determination. It was observed that for linear surfactant Novanik 1047 A the method provides reliable result and thus, can serve for routine analyses. Regarding Triton CF-21, an interfering effect of humic acids was observed; however, after sufficient dilution of the samples, the method can be used as well. Finally, the method can be used for simple analyses of problematic samples without complicated sample-pretreatment.      

Simultaneous displacement of a nitro group during coupling of diazotized <Emphasis Type="Italic">o</Emphasis>-nitroaniline with phenols

During the diazo-coupling reaction, nucleophilic displacement of a nitro group was also observed. This was the main reaction (1→7) when the starting amine bore either a chlorine or methoxy group at the para position (1b–c). The newly prepared compounds (7) might serve as convenient building blocks in synthesis of some heterocycles.      

Fabrication of biaxial textured NiO on Ni in a one-step process

A novel method for the preparation of biaxial textured nickel oxide on commercially available nickel via a modified surface oxidation epitaxy (SOE) process has been developed. Following studies of different heat-treatment procedures for both texturing of nickel and for the fabrication of nickel oxide the following method was found to yield the best results. Nickel was first textured under an argon — hydrogen atmosphere at 1000°C for 120 min, then the temperature was lowered to 800°C and the atmosphere was changed to argon with 3 ppm oxygen. Smooth and crack free c-axis textured and a–b aligned NiO buffer layers with an out-of-plane texture of 7.8° and an in-plane texture of 9.4° were successfully produced. Higher oxygen partial pressure and temperatures resulted in increased surface roughness and excessive grain growth.