On the reaction of tin dichloride and of metallic tin with hydrochloric acid in the presence of alkenes. The question of trichlorostannane(IV) or chlorostannate(II) intermediates.

Studies of the reaction of tin dichloride and of metallic tin with hydrochloric acid gas in diethyl ether are described. On the basis of spectroscopic and analytical data it is concluded that the product is not to be regarded as a tin-hydrogen bonded analog of chloroform, viz. trichlorostannane(IV), and the formation of an equilibrium mixture of hydrogen trichlorostannate(II) and dihydrogen tetrachlorostannate(II) is tentatively suggested. The complexes slowly decompose as a result of diethyl ether cleavage, yielding ethanol and ethyl chloride, together with traces of ethyltin trichloride.The mechanism of addition of the complexes to methyl acrylate is discussed in terms of a 1,4-addition involving initial protonation of oxygen. Reaction of the resulting β-carbomethoxyethyltin trichloride with tin or with zinc gives rise to mixtures of bis(β-carbomethoxyethyl)tin dichloride and tris(β-carbomethoxyethyl)tin chloride Similar reactions were observed for the first time with methyltin trichloride, the reaction with zinc being extremely fast at room temperature.     

Atomic absorption spectrometry of tin with electro-thermal atomization in a molybdenum microtube

The atomic absorption spectrometry of tin with atomization in a molybdenum microtube is described. The addition of hydrogen to the argon purge gas improves the efficiency of atomization of tin; measurements are best done at 224.61 nm. Phosphoric acid lowers the atomization temperature of tin, and depresses the interferences from diverse elements. Tin in canned foods (fruit juices and drinks) can be determined by direct atomization after dilution with phosphoric acid. Prior extraction is necessary for analysis of geological materials.     

Tin underpotential deposition on platinum and its catalytic influence on the kinetics of molecular oxygen electroreduction

The formation and dissolution of tin ad-layers on polycrystalline platinum were analysed by cyclic voltammetry in aqueous 10^–4 M tin(II)/1 M sulfuric acid in the 0.05–0.70 V versus RHE range. At this concentration level it was possible to observe that platinum sites involving (110) planes are mainly related to tin underpotential deposition. In contrast to previous results, no irreversible adsorption was found in the course of the electrodeposition. Thermodynamic adsorption parameters were calculated from the potential dependence of tin surface coverage. Catalytic properties of this new surface were studied on the basis of oxygen electroreduction as a model. Kinetic runs were performed with rotating ring-disk electrodes on bare and tin-modified platinum surfaces. Molecular oxygen reduction on tin-modified platinum takes place through the production of both water and hydrogen peroxide. This interpretation was confirmed by calculating the reaction order with respect to oxygen. Electronic Publication     

氧化锡多晶电导的氧空位控制模型

SnO_2、ZnO等金属氧化物的气敏特性通常以它们在不同气氛中电导值的变化来体现。为弄清这类多晶材料及气敏元件电导变化的基本规律,本文根据表面势垒控制模型和晶界势垒控制模型讨论了氧空位密度对SnO_2多晶材料及气敏元件电导值的重要影响,并根据SnO_2多晶电导的氧空位控制模型,讨论了在不同烧结条件下元件电导的变化规律,并用X光电子能谱(XPS)对结果进行了分析。     

The use of naphthidine as indicator in the determination of zinc in metallurgical analysis

Using naphthidine as an internal indicator in the titration of zinc with standard potassium ferrocyanide solutions, suitable procedures are recommended for the determination of zinc in various non-ferrous alloys and in rubber ashes. With aluminium alloys, aluminium bronzes and white metals the zinc is separated from interfering elements by hydrogen sulphide procedures, whereas with tin bronzes the separation is best accomplished by an 8-hydroxyquinoline procedure. After the solution of rubber ashes in hydrochloric acid, the major interfering elements are removed from the zinc by filtration after making the solution ammoniacal. With samples giving large precipitates with ammonia, it is necessary to redissolve them and determine the entrained traces of zinc.     

Investigations for the determination of tin by flow injection hydride generation atomic-absorption spectrometry

It could be shown that the pre- or double peaks which are frequently observed in the determination of tin by hydride generation atomic-absorption spectrometry are not due to reagent contamination or memory effects. Rather they originate from the silica material used to make the quartz tube atomizer. At elevated temperatures the tin diffuses to the surface and it can be volatilized and atomized only in the presence of hydrogen. The height of the pre-peak depends, among other things, on the time for which the quartz tube atomizer has been at a high temperature without hydrogen. The pre-peaks disappear when argon with 10% (v/v) hydrogen is used as the purge gas. In flow injection the pre-peaks can be separated in time from the analytical signal by using a program in which hydrogen is generated by reaction of sodium tetrahydroborate reluctant solution with the acid carrier prior to the injection of the sample. Also investigated was the influence of the acid and sodium tetrahydroborate concentration on sensitivity and freedom from interferences. Best results were obtained when a saturated boric acid solution containing 0.1M hydrochloric acid was used for standards, samples and carrier solution, and a 0.4% (m/v) sodium tetrahydroborate solution with 0.05% (m/v) sodium hydroxide as the reluctant. Under these conditions tin could be determined accurately in the range 0.008-0.1% in low alloy steel standard reference materials, with matrix-free standard solutions for calibration.     

Entrainment of cold gas into thermal plasma jets

There is increasing evidence that the entrainment of cold gas surrounding a turbulent plasma jet is more of an engulfment type process rather than simple diffusion. A variety of diagnostic techniques have been employed to determine the development of turbulence in a plasma jet and to measure concentration and temperatures of the cold gas entrained into atmospheric-pressure argon plasma jets in ambient argon or air. The results indicate that the transition to turbulence causes a rapid drop of the axial jet velocity due to entrainment of the cold gas surrounding the plasma jet. Dissipation of the cold engulfed gas bubbles by molecular diffusion is relatively slow if molecular gases (for example air) are entrained, as indicated by conditional sampling and CARS measurements. Temperature measurements using emission spectroscopy and enthalpy probes show strong discrepancies in the jet fringes.     

Current status of membraneless water electrolysis cells

Commercial water electrolysis cells require a resistive, ion-permeable, gas-impermeable separator membrane between the electrodes to stop the hydrogen bubbles from mixing with the oxygen bubbles and vice versa. This work reviews the current status of ‘membraneless’ water electrolysis cells that safely avoid need for such a separator membrane. Three different approaches have been used to realize such cells. In the first approach, laminar flow within a microfluidic reaction chamber has been used to entrain the hydrogen and oxygen gas bubbles in separate, parallel streams that do not mix. In the second approach, closely-spaced porous electrodes have had liquid electrolyte divergently pumped through them to sweep the produced hydrogen and oxygen bubbles to different locations. In the most recent, promising approach, gas diffusion electrodes have been used to directly extract gas as it is produced, thereby avoiding discernible bubble formation and eliminating the need for a separator membrane to keep the gases separate.     

Effects of tetrabutylammonium hydrogen sulfate as an electrolyte additive on the electrochemical behavior of lead acid battery

Tetrabutyl ammonium hydrogen sulfate is an ion-paring reagent that has similar properties with ionic liquid. Ionic liquids belong to new branch of salts with unique properties that have ever increasing applications in electrochemical systems especially lithium-ion batteries. For the first time, the effects of tetrabutylammonium hydrogen sulfate (TBAHS) as an electrolyte additive in battery’s electrolyte was studied on the hydrogen and oxygen evolution overpotential and anodic layer formation on lead–antimony–tin grid alloy of lead acid battery by using cyclic voltammetry and linear sweep voltammetry in aqueous sulfuric acid solution. The grid surface morphology after cyclic redox reaction was studied by using scanning electron microscopy. The results show that, by increasing TBAHS concentration in the electrolyte, hydrogen and oxygen overpotential were increased, and so the crystalline structure of PbSO₄ layer changed. Also, cyclic voltammogram on carbon–PbO paste electrode shows that with presence of TBAHS in the electrolyte, oxidation and reduction peak current intensively increased and peak potential for oxidation and reduction of PbO were dependent on TBAHS concentration.     

Untersuchungen an katalytisch aktiven Oberflächenverbindungen. XIII. Struktur und katalytische Eigenschaften von Molybdän-oxid/SiO2-Katalysatoren

Studies on Catalytically Active Surface Compounds. XIII. Structure and Catalytic Properties of Molybdenum Oxide/SiO₂ Catalysts The catalytic properties of Mo oxide/SiO₂ catalysts in the selective oxidation of methanol to formaldehyde are described. It is shown that, independently on the preparation conditions, all catalysts showed relative high activity and selectivity values which were however, not constant during the reaction time. The high initial activity could be stabilized to a limited extent both by prereduction with methanol (but not with hydrogen) and by decreasing the oxygen concentration of the reaction gas. ESR measurements showed that in dependence on the means of reduction (methanol or hydrogen) two different coordinated Mo⁵⁺ ions were formed. Evidence was given by IR spectroscopy that prereduction in methanol caused the formation of methoxy groups stabilizing catalytically active Mo⁵⁺ ions. UV-Vis, ESCA, and electron microscopic measurements showed however, that further aggregation and formation of microcrystallites of MoO₃ took place during the catalytic reaction which caused the observed decrease of the activity.     

The surface and materials science of tin oxide

The study of tin oxide is motivated by its applications as a solid state gas sensor material, oxidation catalyst, and transparent conductor. This review describes the physical and chemical properties that make tin oxide a suitable material for these purposes. The emphasis is on surface science studies of single crystal surfaces, but selected studies on powder and polycrystalline films are also incorporated in order to provide connecting points between surface science studies with the broader field of materials science of tin oxide. The key for understanding many aspects of SnO₂ surface properties is the dual valency of Sn. The dual valency facilitates a reversible transformation of the surface composition from stoichiometric surfaces with Sn⁴⁺ surface cations into a reduced surface with Sn²⁺ surface cations depending on the oxygen chemical potential of the system. Reduction of the surface modifies the surface electronic structure by formation of Sn 5s derived surface states that lie deep within the band gap and also cause a lowering of the work function. The gas sensing mechanism appears, however, only to be indirectly influenced by the surface composition of SnO₂. Critical for triggering a gas response are not the lattice oxygen concentration but chemisorbed (or ionosorbed) oxygen and other molecules with a net electric charge. Band bending induced by charged molecules cause the increase or decrease in surface conductivity responsible for the gas response signal. In most applications tin oxide is modified by additives to either increase the charge carrier concentration by donor atoms, or to increase the gas sensitivity or the catalytic activity by metal additives. Some of the basic concepts by which additives modify the gas sensing and catalytic properties of SnO₂ are discussed and the few surface science studies of doped SnO₂ are reviewed. Epitaxial SnO₂ films may facilitate the surface science studies of doped films in the future. To this end film growth on titania, alumina, and Pt(1 1 1) is reviewed. Thin films on alumina also make promising test systems for probing gas sensing behavior. Molecular adsorption and reaction studies on SnO₂ surfaces have been hampered by the challenges of preparing well-characterized surfaces. Nevertheless some experimental and theoretical studies have been performed and are reviewed. Of particular interest in these studies was the influence of the surface composition on its chemical properties. Finally, the variety of recently synthesized tin oxide nanoscopic materials is summarized.     

Water–oxygen interplay on tin dioxide surface: Implication on gas sensing

Resistance measurements and direct spectroscopic investigations were used to monitor the surface reaction path between oxygen and water at the surface of SnO₂. The experiments were carried out at high sensor operation temperature (330 and 400 °C) and at a constant background of water vapour. We found that there is a significant interaction between adsorbed oxygen ions and water vapour, which results in formation of terminal hydroxyl groups on tin dioxide surface. This observation is an evidence of water–oxygen interaction and so brings a new insight to the mechanistic modelling of the sensing with tin dioxide based sensors.     

气相色谱-微波等离子体炬双检测器及其气相色谱的响应特性

提出并建立了气相色谱-微波等离子体炬(MPT)原子发射光谱和离子化双检测器系统. 以Ar气作为等离子体工作气体, O2气作为等离子体屏蔽气体, 同时获得了被测组分的原子发射和离子化信息, 并对不同种类有机化合物的相对响应系数及检出限进行了测定.     

The atmospheric chemistry of hydrogen peroxide: a review

This paper reviews the atmospheric chemistry of hydrogen peroxide, taking into account the formation processes of both gas-phase and aqueous H2O2, and the reactions involving hydrogen peroxide in the gas phase and in atmospheric hydrometeors. Gas-phase hydrogen peroxide mainly forms upon dismutation of the hydroperoxyl radical, a product of the reactions between atmospheric hydrocarbons, hydroxyl radicals, nitric oxide, and oxygen. Aqueous hydrogen peroxide originates from the dissolution of the gaseous one, the reduction of molecular oxygen, a series of reactions involving dissolved ozone, and the irradiation of anthraquinones, aromatic carbonyls, and semiconductor oxides. The reactions involving aqueous H2O2 are very important in the context of the chemistry of the atmosphere. They include oxidation of S(IV) to S(VI), photolysis, the Fenton reaction in the presence of Fe(II), and possibly the formation of peroxynitrous acid. Within this framework, the correlation of hydrogen peroxide with other atmospheric components and the time trends of hydrogen peroxide in the atmosphere are easily accounted for.     

Efficient Catalytic Production of Hydrogen Peroxide Using Tin-containing Zeolite Fixed Palladium Nanoparticles with Oxidation Resistance

The metal surfaces tend to be oxidized in air through dissociation of the O−O bond of oxygen to reduce the performances in various fields. Although several ligand modification routes have alleviated the oxidation of bulky metal surfaces, it is still a challenge for the oxidation resistance of small-size metal nanoparticles. Herein, we fixed the small-size Pd nanoparticles in tin-contained MFI zeolite crystals, where the tin acts as an electron donor to efficiently hinder the oxidation of Pd by weakening the adsorption of molecular oxygen and suppressing the O−O cleavage. This oxidation-resistant Pd catalyst exhibited superior performance in directly synthesizing hydrogen peroxide from hydrogen and oxygen, with the productivity of hydrogen peroxide at ≈10,170 mmol g_Pd⁻¹ h⁻¹, steadily outperforming the catalysts tested previously. This work leads to the hypothesis that tin is an electron donor to realize oxidation-resistant Pd within zeolite crystals for efficient catalysis to overcome the limitation of generally supported Pd catalysts and further motivates the use of oxidation-resistant metal nanoparticles in various fields.     

An Investigation of the Effect of Air-Oxidation on Coal Liquefaction

Experiments are performed to investigate the effects of oxidation upon coal liquefaction in a combined pre-oxidation-liquefaction process. It is found that the air-oxidation of coal preceding liquefaction is generally detrimental to liquefaction yields for both cases with or without presence of hydrogen gas in the dissolution step, and could be highly harmful to the processes which rely solely upon hydrogen donor solvents such as 1,2,3,4-tetrahydronaphthalene. The analyses of oxidized and unoxidized coals show a significant decrease in hydrogen but increase in oxygen contents of the coal with oxidation. These factors together with the possible formation of oxygen-coal bonds and the increase in —OH and/or —COOH groups in the oxidized coal are thought to account for the decreasing conversion of oxidized coal when it is subjected to liquefaction.     

Effect of H2 Flow Rate on High-Rate Etching of Si by Narrow-Gap Microwave Hydrogen Plasma

For the purpose of realizing a low-cost production process of silane (SiH₄) gas, we have proposed the high-rate etching of metallurgical-grade Si by narrow-gap microwave hydrogen plasma. In this paper, effect of hydrogen gas flow rate (0–10 L/min) on the etch rate has been investigated and correlated with the relative variation of hydrogen-atom density estimated by actinometry. By decreasing hydrogen gas flow rate, the etch rate gradually increases up to the maximum value of 11 μm/min at 2 L/min. This increase is well correlated with the increase of hydrogen-atom density due to the longer residence time of hydrogen molecules in the plasma. On the other hand, when the gas flow rate is lower than 2 L/min, the etch rate abruptly decreases with decreasing gas flow rate in spite of the increase of hydrogen-atom density. From the surface observations and Raman measurements, it is found that the decrease in etch rate in the lower flow rate range is attributed to the formation of microcrystalline Si particles due to the decomposition of generated-SiH₄ molecules in the plasma.     

Computational studies for reduced graphene oxide in hydrogen-rich environment

We employ molecular dynamic simulations to study the reduction process of graphene oxide (GO) in a chemically active environment enriched with hydrogen. We examine the concentration and pressure of hydrogen gas as a function of temperature in which abstraction of oxygen is possible with minimum damage to C-sp(2) bonds, hence preserving the integrity of the graphene sheet. Through these studies we find chemical pathways that demonstrate beneficiary mechanisms for the quality of graphene including formation of water as well as suppression of carbonyl pair holes in favor of hydroxyl and epoxide formation facilitated by hydrogen gas in the environment.     

Syntheses, crystal structures, and quadratic nonlinear optical properties in four “push-pull” diorganotin derivatives

Four “push-pull” diorganotin compounds obtained by reaction of methoxysalicylaldehyde or 4-diethylaminosalicylaldehyde, 2-amino-5-nitrophenol and dibutyltin or diphenyltin oxide are reported. The molecular structures for the diphenyl derivatives, in the solid state, show a tin in a distorted trigonal bipyramid geometry with the oxygen atoms in axial positions and the organic moieties and iminic nitrogen in equatorial ones. For the dibutyl derivative, a dimeric structure was favored due to intermolecular interactions between the tin and oxygen atoms, in this case, the tin atom shows a distorted octahedral geometry. A computational study of the diethyl derivatives constructed from the available dibutyl structure, at DFT level, revealed that the main differences between the solid and gas phases are the geometry around the tin atom and the π-conjugated organic backbone which is nearly planar in the solid state and distorted in the gas phase. The electric field induced second-harmonic (EFISH) of the nonlinear optical (NLO) response for the dibutyl derivatives revealed that the change from boron to tin increases 1.5 times the hyperpolarizabilities (β).     

Absorption and Oxidation of Nitrogen Oxide in Ionic Liquids

A new strategy for capturing nitrogen oxide, NO, from the gas phase is presented. Dilute NO gas is removed from the gas phase by ionic liquids under ambient conditions. The nitrate anion of the ionic liquid catalyzes the oxidation of NO to nitric acid by atmospheric oxygen in the presence of water. The nitric acid is absorbed in the ionic liquid up to approximately one mole HNO₃ per mole of the ionic liquid due to the formation of hydrogen bonds. The nitric acid can be desorbed by heating, thereby regenerating the ionic liquid with excellent reproducibility. Here, time‐resolved in‐situ spectroscopic investigations of the reaction and products are presented. The procedure reveals a new vision for removing the pollutant NO by absorption into a non‐volatile liquid and converting it into a useful bulk chemical, that is, HNO₃.