Synthesis and structure of a new molecular octahedral cluster complex Mo<Subscript>6</Subscript>Se<Subscript>8</Subscript>(Ph<Subscript>3</Subscript>P)<Subscript>6</Subscript>·2H<Subscript>2</Subscript>O

Mo₆Se₈(Ph₃P)₆·2H₂O cluster complex has been synthesized and its structure has been defined. The compound is triclinic, space group P1ˉ, with unit cell parameters a = 14.3356(5) Å, b = 15.7882(4) Å, c = 25.3949(8) Å, = 95.9750(10)°, β = 91.1030(10)°, γ= 112.2570(10)°, V = 5279.8(3) ų, Z = 2, ρ_calc = 1.772 g/cm³. The complex has a molecular structure. The molybdenum atoms of the {Mo₆Se₈} cluster nucleus are coordinated by the phosphorus atoms of triphenylphosphine molecules. Original Russian Text Copyright ? 2007 by Yu. V. Mironov, Zh. S. Kozhomuratova, D. Yu. Naumov, and V. E. Fedorov __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 48, No. 2, pp. 389–393, March–April, 2007.     

Study on the structure of chemically bonded C18 phase for HPLC

Summary The use of monofunctional organosilanes for the preparation of packings with chemically bonded phases guarantees to obtain a defined monomeric structures of bonded alkylsilyl groups. The effect of hydrophobization of the surface of silica gel support modified with methyloctadecylchlorosilane in the presence of an activator has been investigated. A dense coverage of the surface (>4 μmoles/m²) with the C₁₈ groups is obtained at pK_a ≈ 8. By changing the nature and concentration of the activator packings with controlled surface density can be prepared, when the structure of the starting silica gel support are properly selected. On the basis of a simplified cylindrical model of the support’s pores and the geometrical structure of the C₁₈ molecules the maximum value of surface coverage as well as the dimensions of the chains of chemically bonded phases could be estimated.     

On the Preparation of Ni–La Supported on Silica by Sol-gel Process via Propionates

Ni–La/SiO₂ catalysts were prepared by using a new metal organic precursor M(OC₃H₇)_n, dissolved in organic solvent, hydrolysed and finally condensed to form inorganic polymers containing M–O–M or M–(μOH)–M linkages. An optimal distribution of both the active phase ‘Ni’ and the promoter ‘La₂O₃’ was ensured by addition of their corresponding salts, previously dissolved in propionic acid, to a silica solution prior to gelation. After drying under vacuum the precursor was submitted to thermal treatment in air at 600°C with a heating rate of 1°C min^–1. The precursors and the corresponding catalysts were characterised by various techniques (TG-DTA, XRD, FTIR, TEM, BET and porosimetry) and tested for methane dry reforming. This revised version was published online in August 2006 with corrections to the Cover Date.     

Study on interaction between antibiotics and Escherichia coli DH5α by microcalorimetric method

A microcalorimetric technique based on the bacterial heat output was applied to evaluate the influence of antibiotics PIP (Piperacillin Sodium) and composite preparation of PIP and SBT (Sulbactam Sodium) on the growth of E. coli DH5α. The power–time curves of the growth metabolism of E. coli DH5α were studied using a TAM Air Isothermal Microcalorimeter at 37°C. By analyzing the power–time curves, the parameters such as growth rate constants (k), inhibitory ratio (I), the maximum heat power (P _m) and the time of the maximum heat power (t _m) were obtained. The results show that different concentrations of antibiotics affect the growth metabolism of E. coli DH5α. The PIP in the concentration range of 0–0.05 μg mL^–1 has a stimulatory effect on the E. coli DH5α growth, while the PIP of higher concentrations (0.05 –0.25 μg mL^–1) can inhibit its growth. It seems that the composite preparation composed of PIP and SBT cannot improve the inhibitory effect on E. coli DH5α as compared with the PIP.     

Thermal and Spectral Behaviour of 5-chloro-2-methoxybenzoates of Heavy Lanthanides and Yttrium

5-Chloro-2-methoxybenzoates of heavy lanthanides and yttrium were obtained as di- or tetrahydrates with a metal to ligand ratio of 1:3 and general formula: Ln(C₈H₆ClO₃)₃⋅nH₂O, where n=2 for Ln=Tb, Dy, Y and n=4 for Ln=Ho, Er, Tm, Yb, Lu. The complexes were characterized by elemental analysis, IR and FIR spectra, thermogravimetric studies, X-ray diffraction and magnetic measurements. The carboxylate group appears to be a symmetrical, bidentate, chelating ligand. All complexes are polycrystalline compounds. Their thermal stabilities were determined in air and in nitrogen atmospheres. When heated they dehydrate to form anhydrous salts which next in air are decomposed to the oxides of the respective metals while in nitrogen to the mixtures of carbon and oxides or carbon and oxychlorides of respective metals. The complexes are more stable in air than in nitrogen. The solubilities of yttrium and heavy lanthanide 5-chloro-2-methoxybenzoates in water at 293 K are of the order of 10^–3 mol dm^–3 The magnetic moments of the complexes were determined over the range 77–298 K. They obey the Curie–Weiss law. The values of μ_eff calculated for all compounds are close to those obtained for Ln³⁺ by Hund and Van Vleck. The results indicate that there is no influence of the ligand field of 4f electrons on lanthanide ions and the metal ligand bonding is mainly electrostatic in nature. This revised version was published online in August 2006 with corrections to the Cover Date.     

Comparison of the cold vapor generation using NaBH4 and SnCl2 as reducing agents and atomic emission spectrometry for the determination of Hg with a microstrip microwave induced argon plasma exiting from the wafer

A 2.45 GHz low power microwave microstrip plasma (MSP) exiting the wafer and operated with Ar at atmospheric pressure was used for the optical emission spectrometric determination of Hg with the aid of a miniaturized optical fiber spectrometer with a CCD detector and the cold vapor (CV) generation technique using NaBH₄ and SnCl₂ as reductants. The experimental conditions were optimized with respect to the relative intensity of the Hg I 253.6 nm line and its signal-to-background intensity ratio (SBR). So as to understand the results of the optimization experiments, the excitation temperatures as measured from Ar I lines (T _exc) and the electron number densities (n _e) for the Ar MSP loaded with Hg vapors were determined and found to be in the range from 5500 to 6300 K and from 1.4 to 2.0 × 10¹⁴ cm⁻³, respectively. Under the optimized conditions, the detection limit for Hg of the CV-MSP-OES using SnCl₂ as the reducing agent was found to be much lower (0.11 ng mL⁻¹) than in the case where NaBH₄ was used (9 ng mL⁻¹). The linearity range was found to be up to 1 μg mL⁻¹ while the precision was of the order of 0.7–5%. The procedure with SnCl₂ as reductant was used for the determination of Hg at a concentration of 0.2 μg mL⁻¹ in synthetic water samples containing 1 to 4% (m/v) of NaCl with an accuracy of 3% as well as in a solution of the domestic sludge standard reference material (NIST SRM 2781) with a certified concentration for Hg of 3.64 ± 0.25 μg g⁻¹ for which 3.55 ± 0.41 μg g⁻¹ was found. Correspondence: J. A. C. Broekaert, Institut für Anorganische und Angewandte Chemie, Universit?t Hamburg, 20146 Hamburg, Germany     

Thermoelectric power studies on MgO-stabilized β″-alumina

A study of the temperature dependence of thermopower is known to yield auxiliary information about the electronic conductivity of a mixed conductor. In light of the above, thermoelectric power (TEP) measurements were made on MgO-stabilized β″-alumina over the temperature range from 773 to 1223 K under conditions of different sodium activities in the ambient in order to substantiate the existing information on the electronic conductivity of sodium beta alumina (SBA). A mixture of Na _x Si _m O_{2 m + x /2} and SiO₂ in an environment of fixed served as electrodes reversible to Na⁺. The heat of transport obtained using the thermopower data at higher temperatures (973–1223 K) was in fair agreement with the activation energy of electrical conduction determined by other studies like impedance measurements and molecular dynamics simulation. It could be inferred from these results that there is negligible electronic conductivity in SBA under the conditions of measurement. The average TEP for SBA was determined to be 700–800 μV/K and the partial molar entropy of Na⁺ in SBA was found to be ~98 J mol^–1 K^–1. Electronic Publication     

Solution thermolysed tungsten oxide-based electrochromic devices: thickness-dependent step potential analysis

The characterisation of electrochemical behaviour of electrochromic (EC) devices based on solution thermolysed (ST) tungsten oxide (WO₃) thin films was carried out using the step potential excitation method. The method, based on generating plots of current density (J) as a function of passed charge (ΔQ), has been applied for the characterisation of EC-WO₃ thin films in proton-containing aqueous electrolyte. EC devices have been fabricated by employing WO₃ thin films with variable thickness (T) ranging from 0.04 to 0.52 μm. The J vs time (t) responses (chronoamperometry) of these devices were recorded at a fixed applied potential (±0.7 V vs S.C.E.) and values of total passed H⁺ charges (ΔQ) into the WO₃ host lattice during the coloration process are calculated. The J-ΔQ curves corresponding to films of different thickness were plotted as a function of the passed charge volume density, ΔQ /T, and an intercalatable film thickness is calculated to be 0.13 μm. The modulation in optical transmittance after coloration and bleaching was studied in the wavelength range between 350 and 850 nm and an optical efficiency (ξ_λ) is calculated at λ=700 nm. It is found that the ξ_λ wanes with increasing intercalation. Electronic Publication     

纳米二氧化钛粉末的溶胶-凝胶法合成及晶相转化

Nanosized TiO₂ powder with anatase and rutile structures was synthesized by a sol-gel method using TiCl₄ ethanol solution as a precursor.The grain size of TiO₂ powder was about 63nm after the precursor was calcined at 600℃ for 2 hours .The experimental techniques of XRD,TEM and Particle Distribution were used to characterize the synthesized specimens. Various special effects were investigated for their contribution to crystal structure and the size of TiO₂ powder .The formation of anatase as well as the rutile phase of TiO₂ was indicted from the XRD when the reaction temperature was above 30℃ and when the sol was irradiated by infrared rays .However, an anatase TiO₂ powder formed after the heat treatment of the dried gel in a temperature range from 300℃ to 500℃.Under the vacuum drying and with the calcined time below 3hours ,the anatase phase was gained .As well as with the increase of gelatinizing time, the anatase TiO₂ powder was obtained.     

Sintering behavior and ionic conductivity of Ce<Subscript>0.8</Subscript>Gd<Subscript>0.2</Subscript>O<Subscript>1.9</Subscript> with a small amount of MnO<Subscript>2</Subscript> doping

A 20% GdO_1.5 doped ceria solid solution with a small amount of MnO₂ doping (≤5% molar ratio) was prepared via the mixed oxide method from high-purity commercial powders with grain size around 0.2–0.5 μm. X-ray diffraction analysis indicated that all the samples exhibited the fluorite structure, and no new phase was found. The data from dilatometeric measurements and scanning electron microscopy observations revealed that 1% Mn doping reduced the sintering temperature by over 150 °C, and enhanced the densification and grain growth. Mn doping has little effect on grain interior conductivity, but a marked deterioration in grain boundary behavior is observed. This leads to a lower total conductivity in comparison with the undoped Ce_0.8Gd_0.2O_2–δ. Therefore, for solid oxide fuel cells (SOFCs) with Mn-containing compounds as electrodes, optimization of electrode fabrication conditions is needed to prevent the formation of a lower conductivity layer at the electrode/electrolyte interface since Mn will diffuse from the electrode side to the electrolyte during fabrication and operation of SOFCs. Electronic Publication     

Extraction and Preconcentration of the Herbicide Glyphosate and its Metabolite AMPA Using Anion-Exchange Solid Phases

An extraction and preconcentration method has been developed for the determination of glyphosate and its degradation product, aminomethylphosphonic acid (AMPA), over a broad range of concentrations (0.1–500 μg · L⁻¹) in various aqueous matrices which differ in their ionic content. Two anion-exchange resins (the microporous Amberlite^?IRA-416 and the macroporous Amberlite^?IRA-900) and a commercial silica modified cartridge, ISOLUTE-NH₂, were evaluated and compared. The effect of flow-rate, composition and volume of the elution solution, analyte concentration, sample volume and porosity of the sorbents were investigated and the best experimental conditions were then used in the recovery of the analytes from spiked natural waters. Determination of the analytes was performed by HPLC with fluorescence detection, using FMOC-Cl as a pre-column derivatisation agent. Enrichment factors of up to 125 were achieved with the protonated ISOLUTE-NH₂ cartridge allowing the determination of glyphosate at a level of 0.1 μg · L⁻¹. Recovery rates of 99% for glyphosate and 77% for AMPA and relative standard deviations for repeatability of <10% for both analytes were determined with the Amberlite^?IRA-900 macroporous resin.     

Highly sensitive determination of trace potassium ion in serum using the resonance light scattering technique with sodium tetraphenylboron

A resonance light scattering technique has been developed in order to determine potassium ion in serum. Potassium ion was found to bind the tetraphenylboronate anion [(C₆H₅)₄B]⁻ in acetate buffer (pH 8.0) in the presence of sodium dodecyl benzene sulfonate as a stabilizer, forming the B(C₆H₅)₄-K aggregate which produces intense resonance scattering light. Effects of factors such as acidity, ionic strength and interferents on the RLS of B(C₆H₅)₄-K were investigated. The solution pH close to neutral facilitates the production of RLS, and few biologically relevant species interfere in the determination of potassium ion. The resonance scattering light intensity at the maximum peak of 567 nm was linear to the concentration of potassium ion in the range of 0.2–2.0 μg mL⁻¹ with a detection limit of 20.0 ng mL⁻¹. The method was applied to determine trace amounts of potassium ion in serum and showed high sensitivity and accuracy compared with the clinically used ion-selective electrode method.     

Indirect spectrophotometric determination of gentamicin and vancomycin antibiotics based on their oxidation by potassium permanganate

Four simple, accurate, sensitive and economical procedures (A–D) for the estimation of gentamicin sulphate and vancomycin hydrochloride, both in pure form and in pharmaceutical formulations have been developed. The methods are based on the oxidation of the studied drugs by a known excess of potassium permanganate in sulphuric acid medium and subsequent determination of unreacted oxidant by reacting it with amaranth dye (method A), acid orange II (method B), indigocarmine (method C) and methylene blue (method D), in the same acid medium at a suitable λ_max=521, 485, 610 and 664 nm, respectively. The reacted oxidant corresponds to the drug content. Regression analysis of Beer-Lambert plots showed good correlations in the concentration ranges 4–8, 3–8, 4–9 and 5–9 μg ml⁻¹ with gentamicin and 4–8, 1.5–4, 1.5–4 and 3.5–5.5 μg ml⁻¹ with vancomycin for methods A, B, C, and D, respectively. The molar absorptivity, sandell sensitivity, detection and quantification limits were calculated. The stoichiometric ratios for the cited drugs were studied. The optimum reaction conditions and other analytical parameters were evaluated. The influence of the substance commonly employed as excipients with these drugs were studied. The proposed methods were applied to the determination of these drugs in pharmaceutical formulations. The results have demonstrated that the methods are equally accurate and reproducible as the official methods.     

Synthesis and Crystal Structure of the Heteroligand Complex Tris(dipivaloylmethanato)(2,2′-bipyridyl)gadolinium(III) [Gd(Thd)<Subscript>3</Subscript>(Bipy)]

The synthesis and X-ray diffraction analysis of [Gd[Thd)₃(Bipy)] (HThd is dipivaloyl, and Bipy is 2,2′-bipyridyl) are performed. The crystals are triclinic, a = 11.095(5) Å, b = 12.263(3) Å, c = 18.357(4) Å, α = 79.43(2)°, β = 85.24(3)°, γ = 68.79(3)°, V = 2288.5(13) ų, Z = 2, space group P1ˉ, and R = 0.0364 against 9125 reflections with I > 2σ(I). The Gd atom is bonded with six oxygen atoms of three dipivaloylmethanate ligands (with average Gd-O distance 2.343(3) Å) and two nitrogen atoms of the bipyridyl molecule (with average Gd-N distance 2.618(4) Å) at vertices of a distorted square antiprism. The stacking interaction is observed between the bipyridyl molecules linked by the inversion center of the complexes (the distance between the parallel Bipy planes is 3.45 Å). __________ Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 10, 2005, pp. 763–769. Original Russian Text Copyright ? 2005 by Minacheva, Rogachev, Sergienko, Kuz'mina.     

电化学法制备高热稳定性锐钛矿型纳米TiO2

Titanium alkoxides were prepared by anodic dissolution of metallic titanium in absolute ethanol in the presence of HN(C₂H₅)₂*HCl (electro－conductive additives).The solution was directly hydrolyzed to prepare nanocrystalline of TiO₂ (about 10nm)by a sol－gel process.The precursor gels was calcined at T=450 ℃ and 720 ℃for 30 min,and nanocrystalline of TiO₂ (anatase) with high textural and thermal stability was obtained.FTIR,XRD,TEM,were used to characterize the structure of titanium alkoxides and nanocrystalline of TiO₂.The characteristics of nanocrystalline of TiO₂ was depended on the properties of titanium alkoxides.The Ti(OEt)₄ as a source of titanium yielded the best textural and thermal stability nanocrystalline of TiO₂.     

Study of Solid Phase Extraction Prior to Spectrophotometric Determination of Platinum with N-(3,5-Dimethylphenyl)-N′-(4-Aminobenzenesulfonate)-Thiourea

A highly sensitive, selective and rapid method for the determination of platinum based on the rapid reaction of platinum(IV) with N-(3,5-dimethylphenyl)-N′-(4-aminobenzenesulfonate)-thiourea (DMMPT) and the solid phase extraction of the Pt(IV)-DMMPT complex with C₁₈ membrane disks was developed. In the presence of pH = 3.8 buffer solution and cetyl trimethylammonium bromide (CTMAB) medium, DMMPT reacts with platinum to form a violet complex of a molar ratio of 1:3 (platinum to DMMPT). This complex was enriched by solid phase extraction with C₁₈ membrane disks, and an enrichment factor of 200 was obtained. The molar absorptivity of the complex is 9.51 × 10⁴ L · mol⁻¹ · cm⁻¹ at 755 nm, and Beer’s law is obeyed in the range of 0.01–3.0 μg mL⁻¹ in the measured solution. The relative standard deviation for eleven replicate samples of 0.01 μg mL⁻¹ level is 1.79%. The detection limit reaches 0.02 μg L⁻¹ in the original samples. This method was applied to the determination of platinum in water and soil samples. The relative standard deviations are 2.9–3.4%. The recoveries are 94–105%. The values of determination obtained agree with those of the ICP-MS method. The results are satisfactory.     

Amplification of bioelectrocatalytic signalling based on silver nanoparticles and DNA-derived horseradish peroxidase biosensors

Horseradish peroxidase (HRP) was immobilized onto a polyion complex membrane containing positively charged silver nanoparticles (nanosilver), double stranded DNA and poly(thionine) to fabricate highly sensitive and selective electrochemical hydrogen peroxide (H₂O₂) biosensor on a glassy carbon electrode. The presence of nanosilver provided a biocompatible microenvironment for enzyme molecules, greatly amplified the surface coverage of HRP on the electrode surface, and most importantly could act as a charge carrier. The process of the biosensor construction was characterized by scanning electron microscopy. Voltammetric and time-based amperometric techniques were employed to characterize the properties of the derived biosensor. Under optimal conditions, the biosensor has an electrocatalytic behavior towards the H₂O₂ reduction, and exhibits a linear range from 1.1 μM to 5.2 mM, with a lower detection limit of 0.2 μM. The apparent Michaelis–Menten constant of the biosensor to H₂O₂ was estimated to be 1.02 mM. Furthermore, the biosensor exhibited high sensitivity, good reproducibility, and acceptable stability. Importantly, the properties of composite film, together with the bioelectrochemical catalytic activity, could make them useful in the development of bioelectronic devices and investigation of protein electrochemistry at functional interface. Correspondence: Yan Liu, College of Chemistry, Chongqing Normal University, Chongqing 400047, P.R. China     

Evaluation of the corrosion resistance of electroless Ni-P and Ni-P composite coatings by electrochemical impedance spectroscopy

Electroless Ni-P composite coatings have gained a good deal of popularity and acceptance in recent years as they provide considerable improvement of desirable qualities such as hardness, wear, abrasion resistance, etc. The disagreement among researchers on the corrosion behaviour of these coatings warrants a thorough investigation. Among the various techniques available for the determination of corrosion resistance, electrochemical impedance spectroscopy (EIS) is considered to be superior as it provides not only an assessment of the corrosion resistance of different deposits but also enables the mechanistic pathway by which the deposits become corroded to be determined. The present investigation focuses on the evaluation of the corrosion resistance of electroless Ni-P and Ni-P-Si₃N₄, Ni-P-CeO₂ and Ni-P-TiO₂ composite coatings produced using an acidic hypophosphite-reduced electroless nickel bath, using EIS. The study makes evident that the same fundamental reaction is occurring on all the coatings of the present study but over a different effective area in each case. The charge transfer resistance of electroless Ni-P and Ni-P composite deposits are in the range 32,253–90,700 Ω cm², whereas the capacitances of these coatings are in the range 11–17 μF/cm². The improved corrosion resistance obtained for electroless Ni-P and Ni-P composite coatings is due to the enrichment of phosphorus on the electrode surface, which enables the preferential hydrolysis of phosphorus over that of nickel. The better corrosion resistance obtained for electroless Ni-P composite coatings can be ascribed to the decrease in the effective metallic area prone to corrosion. Among the three electroless Ni-P composite coatings, the corrosion resistance is in the following order: Ni-P-CeO₂=Ni-P-Si₃N₄>Ni-P-TiO₂. Electronic Publication     

Ion chromatographic and spectrometric determination of water-soluble compounds in airborne particulates, and their correlations in an industrial area in Attica, Greece

In the time period from June 2005 to May 2006 in 42 sampling campaigns 84 filter samples of airborne particulate matter, coarse (PM_10–2.5) and fine (PM_2.5), were collected using a Gent stacked filter unit in the coastal industrial area of Aspropyrgos in Attica, Greece. The average PM₁₀ (PM_10–2.5 + PM_2.5) concentration was found to be 66 μg · m⁻³, exceeding more than 1.6 times the annual limit of 40 μg · m⁻³. The samples were analysed for Cl⁻, NO₃ ⁻, SO₄ ²⁻, Ca²⁺, Mg²⁺, Na⁺, K⁺ and NH₄ ⁺ using ion chromatography. The data were compared with results obtained with other spectrometric methods, such as inductively coupled plasma-atomic emission spectrometry, atomic absorption spectrometry, energy dispersive X-ray fluorescence and reflectometry. The determined average ionic content comprised about 44% of the PM₁₀ mass. The ionic composition, as well as the possible matrix compounds in both fractions were evaluated by dividing the sampling period into summer and winter season. In the PM_10–2.5/PM_2.5 fraction in summer time the concentrations of Ca²⁺, Mg₂₊ and NO₃ ⁻ were enriched in the coarse fraction. In winter time all species were enriched in the coarse fraction, especially Ca²⁺, Cl⁻ and NO₃ ⁻. NH₄ ⁺ was constantly higher in the fine fraction in summer as well as in winter time. Factor analysis was applied to obtain correlations between cations and anions leading to matrix compounds in both fractions. From the evaluation of the results obtained, some of the local air pollution sources could be identified. Correspondence: Klaus-Michael Ochsenkühn, Laboratory for Trace Element Studies, Institute of Physical Chemistry, NCSR “Demokritos”, Aghia Paraskevi 15310, Athens, Greece     

改变枸橼酸和EDTA抗衡阳离子对草酸钙结石抑制作用的体外模拟

The effects of counterions of citric acid and EDTA on the crystallization of calcium oxalate (CaO_x) were in-vestigated in silica gel with a double diffusion technique. The ability of inhibiting the growth and aggregation of CaO_x crystal and the ability of inducing formation of COD follows： potassium citrate 》 sodium citrate >citric acid. Na₂EDTA had a stronger ability to inhibit the aggregation of CaO_x crystals than that of EDTA， but a weaker ability to inhibit nucleation and growth of CaO_x crystals. Since COM exhibits a greater degree of attachment to renal tubule cells in culture compared with COD， that is， COD is easy to be expelled from the body along with the urine. So both inducing formation of COD and inhibiting growth and aggregation of CaO_x crystal can decrease the probability of urinary stones. These results have positive significance in the prevention and cure of urinary stones clinically.