A new way of synthesis of V0.13Mo0.87O2.935 and an investigation on its structural, thermal, and anodic properties

V_0.13Mo_0.87O_2.935 powder was obtained by reducing acidified vanadate and molybdate solution at 60 °C by passing hydrogen sulfide gas through the solution. The obtained multicomponent mixed oxide was used as an anode material for the first time in the literature and tested in the solid oxide fuel cell for the temperatures of 700, 750, and 800 °C and the values of 0.38 ± 0.06 A/cm² and 0.18 ± 0.03 W were respectively obtained as current density and power at 800 °C in the cell.     

Thermal transformations of Cu–Mg (Zn)–Al(Fe) hydrotalcite-like materials into metal oxide systems and their catalytic activity in selective oxidation of ammonia to dinitrogen

Layered double hydroxides (LDHs) containing Mg²⁺, Cu²⁺ or Zn²⁺ cations in the Me^II positions and Al³⁺ and Fe³⁺ in the Me^III positions were synthesized by co-precipitation method. Detailed studies of thermal transformation of obtained LDHs into metal oxide systems were performed using high temperature X-ray diffraction in oxidising and reducing atmosphere, thermogravimetry coupled with mass spectrometry and temperature-programmed reduction. The LDH samples calcined at 600 and 900 °C were tested in the role of catalysts for selective oxidation of ammonia into nitrogen and water vapour. It was shown that all copper congaing samples presented high catalytic activity and additionally, for the Cu–Mg–Al and Cu–Mg–Fe hydrotalcite samples calcined at 600 °C relatively high stability and selectivity to dinitrogen was obtained. An increase in calcination temperature to 900 °C resulted in a decrease of their catalytic activity, possibly due to formation of well-crystallised metal oxide phases which are less catalytically active in the process of selective oxidation of ammonia.     

In vacuo reduction of silver orthophosphate with graphite for high‐precision oxygen isotope analysis

The reduction of silver phosphate with graphite under vacuum conditions was studied at final reaction temperatures varying from 430 to 915°C to determine: (i) the CO₂ extraction yield, and (ii) the oxygen isotopic composition of CO₂. The CO₂ yield and oxygen isotopic composition were determined on a calibrated dual inlet and triple collector isotope ratio mass spectrometer. We observed the following three stages of the reduction process. (1) At temperatures below 590°C only CO₂ is formed, while silver orthophosphate decays to pyrophosphate. (2) At higher temperatures, 590–830°C, predominantly CO is formed from silver pyrophosphate which decays to metaphosphate; this CO was always converted into CO₂ by the glow discharge method. (3) At temperatures above 830°C the noticeable sublimation of silver orthophosphate occurs. This observation was accompanied by the oxygen isotope analysis of the obtained CO₂. The measured δ¹⁸O value varied from ?11.93‰ (at the lowest temperature) to ?20.32‰ (at the highest temperature). The optimum reduction temperature range was found to be 780–830°C. In this temperature range the oxygen isotopic composition of CO₂ is nearly constant and the reaction efficiency is relatively high. The determined difference between the δ¹⁸O value of oxygen in silver phosphate and that in CO₂ extracted from this phosphate is +0.70‰. Copyright © 2010 John Wiley & Sons, Ltd.     

An Investigation on the Effects of Experimental Variables on Silver Nano Particles Produced by Electromagnetic Levitation Technique

In this study the effects of melt temperature and flow rate of cooling gas on the characteristics of silver nanoparticles have been studied. Transmission electron microscopy and dynamic light scattering techniques have been employed to monitor morphology and particle size of the product. Measurements reveal that higher melt temperatures and higher cooling gas flow rates can decrease particle size. Silver nanoparticles with an average particle size of 35 nm and specific surface of 18.489 m²/g have been obtained at a melt temperature of 1,130 °C with argon flow rate of 20 liters per minute.     

Kinetics and mechanism of the formation of silver nanoparticles by reduction of silver (I) with maltose in the presence of some active surfactants in aqueous medium

The kinetics and mechanism of the formation of silver nanoparticles by reduction of Ag⁺ with maltose were studied spectrophotometrically by monitoring the absorbance change at 412 nm in aqueous and micellar media at a temperature range 45–60 °C. The reaction was carried out under pseudo-first-order conditions by taking the [maltose] (>tenfold) the [Ag⁺]. A mechanism of the reaction between silver ion and maltose is proposed, and the rate equation derived from the mechanism was consistent with the experimental rate law. The effect of surfactants, namely cetyltrimethylammonium bromide (CTAB, a cationic surfactant) and sodium dodecyl sulfate (SDS, an anionic surfactant), on the reaction rate has been studied. The enthalpy and the entropy of the activation were calculated using the transition state theory equation. The particle size of silver sols was characterized by transmission electron microscopy and some physiochemical and spectroscopic tools.     

Nano silver coated patterned silica thin film by sol–gel based soft lithography technique

We report the fabrication of nano silver coated patterned silica thin film by sol–gel based soft lithography technique. Initially, silica gel film on soda lime silica glass was prepared by dipping technique from a silica sol of moderate silica concentration. A PolydimethylSiloxane elastomeric stamp containing the negative replica of the patterns of commercially available compact disc was used for embossing the film and the embossed film was cured up to 450 °C in pure oxygen atmosphere for oxide film. Finally, a precursor solution of AgNO₃ in water containing polyvinyl alcohol as an organic binder was made and used for coating on the patterned silica film by dipping technique and cured the sample up to 450 °C in reducing gas atmosphere to obtain nano silver layer. The formation of only cubic silver (~4.0 nm) and both cubic silver (~5.2 nm) and silver oxide (~3.6 nm) crystallites at 350 and 450 °C film curing temperatures respectively were confirmed by XRD measurements. The % of nano silver metal and silver oxide were 75.4 and 24.6 respectively. The nano-structured surface feature was visualized by FESEM whereas AFM revealed the high fidelity grating structure of the films. Presence of both spherical and rectangular structure (aspect ratio, 2.37) of nano silver/silver oxide was confirmed by TEM. The films were also characterized by UV–Vis spectral study. The patterned film may find application in chemical sensor devices.     

Reduction of silver ions to silver with polyaniline/poly(vinyl alcohol) cryogels and aerogels

The macroporous conducting polymer cryogels were prepared by the oxidation of aniline hydrochloride in the frozen aqueous solutions of poly(vinyl alcohol) at ? 24 °C. Corresponding polyaniline aerogels supported with poly(vinyl alcohol) have been obtained after thawing of cryogels followed by freeze-drying. Silver was deposited on the composites using the ability of polyaniline to reduce silver ions after the immersion in silver nitrate solutions. Swollen cryogels were coated only on the surface with macroscopic silver particles due to the closed-pore structure in cryogels and limited penetration of silver ions into macropores. The diffusion of silver ions to freeze-dried aerogels was better and further improved by vacuum treatment. Silver microcubes were produced in the pores, the weight fraction of silver in dry composites being typically several per cent, a maximum 13 wt%. The conductivity of the aerogels compressed to pellets depended on the processing and the highest value was 0.27 S cm^?1. The aerogels containing silver were characterized in detail with Raman spectroscopy.     

A New Amperometric Carbon Paste Enzyme Electrode for Ethanol Determination

Abstract

In this study, a new amperometric carbon paste enzyme electrode for determination of ethanol was developed. The carbon paste was prepared by mixing alcohol dehydrogenase, its coenzyme nicotinamide adenine dinucleotide (oxidized form, NAD⁺), poly(vinylferrocene) (PVF) that was used as a mediator, graphite powder and paraffin oil, then the paste was placed into cavity of a glass electrode body. Determination of ethanol was performed by oxidation of nicotinamide adenine dinucleotide (reduced form, NADH) generated enzymatically at +0.7 V. The effects of enzyme, coenzyme and PVF amounts; pH; buffer concentration and temperature were investigated. The linear working range of the enzyme electrode was 4.0×10^?4–4.5×10^?3 M, determination limit was 3.9×10^?4 M and response time was 50 s. The optimum pH, buffer concentration, temperature, and amounts of enzyme, NAD⁺ and PVF for enzyme electrode were found to be 8.5, 0.10 M, 37°C, 2.0, 6.0, and 12.0 mg, respectively. The storage stability of enzyme electrode at +4°C was 7 days. Enzyme electrode was used for determination of ethanol in two different wine samples and results were in good agreement with those obtained by gas chromatography.     

Study on dynamics characteristics of wet air oxidation of non-ionic surfactants

Wet air oxidation is an effective method to deal with highly concentrated nondegradable emulsification wastewater which contains non-ionic surfactants. This article illustrates our investigation on dynamic characteristics of wet air oxidation of typical non-ionic surfactants like polyether, phenol ether and widely used alcohol ether. The experimental results indicated that the oxidation rate of polyether, phenol ether and alcohol ether obviously ascended as the temperature rose. A good oxidation effect was available at 240℃. The TOC removal rate could reach 88.0%, 94% and 91.5%, after 125 min reaction. Alcohol ether was prone to an easier oxidation compared with polyether and phenol ether when the temperature was 220℃ or below. The oxidation rate of alcohol ether was higher than that of polyether at 160℃, while the oxidation rate of polyether was higher than that of phenol ether between 180℃ and 220℃. During the later period of the reaction at 240℃, the rate of phenol ether was higher than that of alcohol ether, which was still higher than that of polyether. Partitioned first order kinetics model analy-sis showed that the apparent activation energy of alcohol ether was lower than that of both polyether and phenol ether in the leading stage and lagging stage, and it was easy to acquire a higher oxidation rate for alcohol ether at low temperature. Three parameter general dynamics model analyses showed that the reason why the oxidation rate of polyether was lower than that of alcohol ether was that the oxidation of polyether was more apt to be converted to intermediate production than that of alcohol ether, whereas between 200℃ and 220℃, the direct oxidation rate of polyether and the oxidation rate of intermediate product were obviously lower than that of alcohol ether. The apparent activation energy of direct and indirect oxidation of polyether was 43.37 and 60.45 kJ?mol?1, respectively, while the corre-sponding apparent activation energy of alcohol was 38.74 and 58.09 kJ·mol?1, respectively.     

Pyrolysis of Eucalyptus wood in a fluidized-bed reactor

Eucalyptus wood can be utilized as a biomass feedstock for conversion to bio-oil using a pyrolysis process. Eucalyptus wood samples were initially pyrolyzed on a laboratory-scale pyrolysis system at different values in the ranges of 300–800 °C and 0.050–0.300 L min^?1 to determine the effects of operation temperature and N₂ flow rate, respectively, on the yields of products. Then, the bio-oil in the highest yield (wB = 44.37 %), which was obtained at pyrolysis final temperature (450 °C), heating rate (35 °C min^?1), particle size (850 μm), and sweeping flow rate (0.200 L min^?1), was characterized by Fourier transform infra-red spectroscopy, gas chromatography/mass spectrometry and column chromatography. Subsequently, it was shown that the operating temperature and N₂ gas flow rate parameters affected the product yields. Also, some important physico-chemical properties of the pyrolytic oil obtained in high yield were determined as a calorific value of 37.85 MJ kg^?1, an empirical formula of CH_1.651O_0.105N_0.042S_0.001, a rich chemical content containing many different chemical groups, a density of 981.48 kg m^?3, and a viscosity of 61.24 mm² s^?1. Based on the determined properties of the pyrolytic oil, it was concluded that the use of pyrolytic oil derived from Eucalyptus wood may be useful for the production of alternative liquid fuels and fine chemicals after the necessary improvements.     

Catalytic oxidation of NO over Mn–Co–Ce–Ox catalysts: effect of reaction conditions

Manganese–cobalt–cerium oxide (Mn–Co–Ce–Ox) catalysts were synthesized by the co-precipitation method and tested for activity in low-temperature catalytic oxidation of NO in the presence of excess O₂. With the best Mn–Co–Ce mixed-oxide catalyst, approximately 80 % NO conversion was achieved at 150 °C and a space velocity of 35,000 h^?1. The effect of reaction conditions (reaction temperature, volume fractions of NO and O₂, gas hourly space velocity (GHSV), and catalyst stability) was investigated. The optimum reaction temperature was 150 °C. Increasing the O₂ content above 3 % results in almost no improvement of NO oxidation. This catalyst enables highly effective removal of NO within a wide range of GHSV. Furthermore, the stability of the Me–Co–Ce–Ox catalyst was excellent; no noticeable decrease of NO conversion was observed in 40 h.     

Controlled growth of ZnO nanorod templates and TiO<Subscript>2</Subscript> nanotube arrays by using porous TiO<Subscript>2</Subscript> film as mask

Silver nanoparticles well dispersed in a spherical Poly(vinylpyrollidone)(PVP) matrix were simply prepared by spray pyrolysis of aqueous solutions of AgNO₃ and PVP without any reducing agent. Highly monodisperse silver particles were obtained above the initial mass ratio of PVP/AgNO₃ ∼ 1 and in a certain narrow temperature range. Below the critical mass ratio the silver particles grew to larger ones polydispersely. As the ratio increased above it, they became smaller maintaining their monodispersity. The use of PVP considerably decreased the reduction temperature of the silver nitrate from 450 °C to 250 °C under the same pyrolysis conditions, due to its reducing nature. As the pyrolysis temperature increased above the decomposition temperature of PVP, the silver particles in the matrix grew to merge to a single particle while their crystallite size did not increase as much. The spherical assemblies of the silver nanoparticles were hardly disengaged even after severe washing off the matrix materials. The mechanism of the nanoparticle growth was also discussed.     

The preparation of conducting polyaniline–silver and poly(p-phenylenediamine)–silver nanocomposites in liquid and frozen reaction mixtures

The oxidation of aniline with silver nitrate in 1 mol L⁻¹ acetic acid at 20 °C yielded a composite of two conducting components, polyaniline and silver; the acceleration with 1 mol% of p-phenylenediamine is needed for efficient synthesis. The yield and molecular weight increased when aniline was copolymerized with 10 mol% p-phenylenediamine. Such product displayed metallic conductivity below 180 K and semiconductor type above this temperature. As the result, the conductivity was the same at 100 and 300 K. The oxidation of p-phenylenediamine alone with silver nitrate also produced a conducting composite having the conductivity of 1,750 S cm⁻¹ despite the assumed nonconductivity of poly(p-phenylenediamine). The present study demonstrates that all oxidations proceeded also in frozen reaction mixtures at −24 °C, i.e., in the solid state. In most cases, molecular weights of polymer component increased, the conductivity of composites with silver improved, to 2,990 S cm⁻¹ for poly(p-phenylenediamine)–silver, and remained high after deprotonation with 1 mol L⁻¹ ammonium hydroxide.

     

High-Efficiency Liquid Chromatography Using Sub-2?��m Columns at Elevated Temperature for the Analysis of Sulfonamides in Wastewater

Efficiency in HPLC can be enhanced by increasing the column length and/or decreasing the particle size. The use of high temperature in HPLC has emerged as a valuable tool to overcome the increase in column backpressure when using small packing particles, as it allows for reduction in mobile phase viscosity. In this study, high plate count was obtained by coupling sub-2 ??m columns at elevated temperature to reduce the viscosity of the mobile phase, thus reducing the column backpressure. At 80 °C, up to three columns of 15 cm × 4.6 mm I.D. packed with 1.8 ??m particles could be coupled generating ~84,000 theoretical plates for the last eluting compound. The number of theoretical plates was increased on average by a factor of ~3.6 when three columns were coupled at 80 °C compared with one column at 30 °C. The relationships between separation efficiency and column length were examined using Van Deemter plots constructed at 30 °C and 80 °C for different column lengths. The advantages of using coupled columns in combination with elevated temperature for the environmental analysis were illustrated using test mixtures comprised of eight sulfonamides separated on one column at 30 °C and three coupled columns at 80 °C by isocratic elution. Sample clean up was carried out by employing solid-phase extraction (SPE) using Oasis HLB cartridges. The method developed was validated based on parameters such as linearity, precision, accuracy, detection and quantification limits. Recoveries generally ranged from 71.7 to 99% (with the exception of sulfanilamide), with standard deviations not higher than 4.7%. The detection limits of the method ranged from 0.6?C2 ??g L^?1, while limits of quantification were in the range 2?C6.7 ??g L^?1 with UV detection.     

Regularities of the formation of silver nanoparticles with oligostyrylmonocarboxylate ligands in ED-20 oligomer

Regularities of the formation of silver nanoparticles according to the reduction reaction of silver oligostyrylmonocarboxylate with ED-20 resin in the absence of hardening agent were studied at 60–75°C by UV/Vis spectroscopy and IR spectroscopy, transmission electron microscopy, and viscosimetry. Spherical silver nanoparticles with oligostyrylcarboxylate ligands characterized by diameter equal to 1.8 ± 0.2 nm and tendency toward ordered disposition in space were obtained. The process of formation of nanoparticles includes consecutive formation of diphilic complexes of silver carboxylate with epoxy resin, Ag⁺ → Ag⁰ reduction, and formation of (Ag⁰) _n nuclei at the ends of the diexpoxy component and/or along the oligomer chain. The activation energy values of formation of nanoparticles during the “inductive period” and at the stage of accumulation as well as the activation energy of viscous flow of ED-20 were measured. The threshold temperature of formation of narrow-size silver nanoparticles in epoxy oligomer ED-20 equals 75°C.     

Analysis of thermolabile residual solvents in a spray dried dispersion using static headspace gas chromatography

In this study, we discuss the development of a static headspace gas chromatography method for the analysis of residual acetone as well as its enriched impurities including mesityl oxide and diacetone alcohol, in a spray dried dispersion. The major challenges include the instability of mesityl oxide and diacetone alcohol at high temperature and peak tailing of diacetone alcohol. It was found that the headspace oven temperature has to be controlled to 150°C or below to prevent degradation beyond an acceptable level (< 1%). The peak tailing of diacetone alcohol was attributed to the “Phase Soaking” effect due to excessive diluent, which may condense and temporarily modify the stationary phase. The peak shape of diacetone alcohol is dependent on the column loading capacity and the peak area of N‐methyl pyrrolidone, the solvent that elutes after diacetone alcohol. The headspace oven temperature was set at 140°C, where the highest response ratio of diacetone alcohol/N‐methyl pyrrolidone at 1.46 and thus the best sensitivity was obtained. The calculated quantitation limits were 1 ppm for acetone, 3 ppm for mesityl oxide and 31 ppm for diacetone alcohol. The method successfully passed validation criteria for specificity, linearity, accuracy, and precision.     

Purification and Characterization of Hyaluronate Lyase from <Emphasis Type="Italic">Arthrobacter globiformis</Emphasis> A152

A hyaluronate lyase was obtained by cultivating Arthrobacter globiformis strain A152. The enzyme was purified to homogeneity from the supernatant by ammonium sulfate fractionation, Q Sepharose Fast Flow, and Sephadex G-100 chromatography. The purification resulted in a 32.78-fold increase in hyaluronate lyase activity with specific activity of 297.2 U/mg. The molecular weight of the enzyme determined by SDS-PAGE was approximately 73.7 kDa. Using hyaluronic acid (HA) as a substrate, the maximal reaction rate (V_max) and the Michaelis–Menten constant (K_m) of hyaluronate lyase were found to be 4.76 μmol/min/ml and 0.11 mg/ml, respectively. The optimum pH and temperature values for hyaluronate lyase activity were pH 6.0 and 42 °C, respectively. This enzyme was stable at pH 4–10, 5–7, and 5–7 at 4, 37, and 42 °C, respectively. Investigation about temperature effects on hyaluronate lyase displayed that it was stable at 30–37 °C and also showed high activity at 37 °C. The enzymatic activity was enhanced by Ca²⁺ and was strongly inhibited by Cu²⁺ and SDS. These properties suggested that the hyaluronate lyase in this study could bring promising prospects in medical and industry applications.     

HTLC: A Viable Approach to Fast LC of Biogenic Amines in Food with Legacy Equipment

Nowadays, there is a demand for fast liquid chromatography (LC) of biogenic amines in food with the equipment available in the average laboratory. To this end, high-temperature liquid chromatography (HTLC) is presented in this study as a viable option, working on a conventional LC platform at moderately high temperatures up to 80 °C. The LC platform was adapted by including an appropriate length of stainless-steel microbore tubing as a preheater. Biogenic amines as benzoyl derivatives showed good thermostability on a thermally rugged column (150?×?4.6 mm, 5 µm). As a model application the HTLC conditions were developed for wine separation. The separation selectivity changed considerably with temperature in the range 36–84 °C, and baseline resolution was obtained only at temperatures well above ambient. At 73 °C oven temperature, the system allowed a flow rate as high as 3 mL min^?1 with the backpressure not exceeding 195 bar (2800 psi). The separation took less than 5 min, comparably fast to documented fast LC separations, and typically at least three to five times faster than a conventional separation.     

Green Synthesis and Characterization of Silver Nanoparticles Using Ascomycota Fungi Penicillium nalgiovense AJ12

A new method for green synthesis of silver nanoparticles using the cell-free filtrate of Penicillium nalgiovense AJ12 as reducing and protecting agent was described. The pathway is based on the reduction of Ag¹⁺ by protein(s). Various techniques such as UV–Vis spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier transform infrared and Zeta potential measurements were used to characterize the silver nanoparticle obtained. The results revealed synthesis of the spherical silver nanoparticles coated with protein(s). The average size of the particles obtained from TEM was 15.2 ± 2.6 nm. DLS measurements showed that the particle size was higher than that estimated from TEM measurements and was 25.2 ± 2.8 nm. Studies on the role of the cell-free filtrate proteins in the synthesis of silver nanoparticles indicated that the process is non-enzymatic but involves amino acids interactions with silver ions. It was found that the aqueous silver nanoparticles suspensions exhibited excellent stability over a wide range of ionic strength, pH and temperature.     

Deposition of La2Zr2O7 film by chemical solution deposition

La₂Zr₂O₇ (LZO) formation of bulk powders and of films by chemical solution deposition (CSD) process have been studied using propionates. The treatment involved a one step cycle in the reducing forming gas (Ar-5%H₂) to be compatible with Ni-5at%W RABITS. Large amount of residual carbon was found in LZO powders formed in these conditions (10 wt%). The volume fraction of the cube texture in LZO films on Ni-5at%W RABITS was found to be a function of the speed of the gas flown above sample. This phenomenon is discussed in considering the C deposited from the carbon-containing gases emitted during the pyrolysis of the precursor. Using proper conditions (950 °C and the speed of gas of 6.8 × 10^?2 m/s), LZO films with good surface crystallinity could be obtained on Ni-5at%W RABITS as demonstrated by X-ray diffraction, electron backscattered diffraction and RHEED. The existence of residual carbon in oxide films is a common question to films deposited by CSD processes under reducing condition.