Heterogeneous chemistry between PbSO4 and calcite microparticles using Raman microimaging

Currently, the smelting activities of lead and zinc are the loudest sources of local pollution by emission in the troposphere of dust of micrometer size containing PbSO(4). As the particles evolve in the troposphere, their chemical and physical properties - and hence their characteristics such as toxicity - change by accumulation of atmospheric heterogeneous reactions. Calcite (CaCO(3)) represents a large part of the mineral fraction in tropospheric aerosols with aerodynamic diameters less than 10 microm. The calcite particles are expected to react with PbSO(4) particles. In an effort to model the chemical behaviour of PbSO(4) individual particles in the troposphere, we present the in situ Raman imaging results during the course of the reactions in a water droplet of PbSO(4) particles with a calcite microcrystal surface. The computer-microcontrolled XY scanning and Z focusing of confocal Raman imaging combined with multivariate curve resolution (MCR) of Raman images have resolved the severe spectral overlaps of the Raman spectra which are not resolved by the spatial resolution of the instrument ( approximately 1 microm(3)). The results pointed out the identification and the mapping of Pb(3)(CO(3))(2)(OH)(2), PbCO(3) and CaSO(4).2H(2)O (gypsum) on the calcite surface.     

Particle-particle chemistry between micrometer-sized PbSO4 and CaCO3 particles in turbulent flow initiated by liquid water

A mixture of natural and anthropogenic particles is ubiquitous in the troposphere and exerts an important influence on air quality. This work reports the study of mixing and heterogeneous chemistry of particles of natural-like mineral dust (CaCO(3)) and anthropogenic-like microparticle (PbSO(4)) in turbulent air flow under varying relative humidity. Sparse monolayers of laboratory-generated particles were collected on substrates using impaction. The grain size distribution and chemistry of micrometer-sized particles were determined as CaCO(3)-PbSO(4) internal and external mixtures by Raman imaging, scanning electron microscopy, and time-of-flight static secondary ionization mass spectrometry. The condensation of a thin water layer on mixed aggregates initiates the formation of complex internal mixtures of Pb(3)(CO(3))(2)(OH)(2), PbCO(3), CaSO(4)·2H(2)O, CaCO(3), and PbSO(4) fine particles. These heterogeneous chemistry processes which may occur in ambient air can increase dramatically the amounts of hazardous breathable particles.     

PbSO4纳米片晶的微乳法制备与自组装

采用水（溶液）／Triton X-100／环己烷／正戊醇微乳体系，制备片状PbSO4纳米晶，并利用TEM对产物进行了表征。考察并初步讨论了微乳体系中几种因素对其尺寸及形貌的影响以及PbSO4纳米晶在微也液中的生长和自组装机制。     

Fabrication of PbSO4 negative electrode of lead-acid battery with high performance

Journal of Solid State Electrochemistry - This paper reports the preparation and electrochemical properties of the PbSO4 negative electrode with polyvinyl alcohol (PVA) and sodium polystyrene...     

Electrochemical behavior of PbO2/PbSO4 electrode in the presence of surfactants in electrolyte

The electrochemical behavior of PbO₂/PbSO₄ electrode is investigated in 4.5 M H₂SO₄ in presence of three surfactants, Sodium Dodecyl Sulfate (SDS), Cetyltrimethylammonium bromide (CTAB) and Sodium tripolyphosphate (STPP), using cyclic voltametry, electrochemical spectroscopy impedance and galvanostatic discharge as techniques. The micro morphology of the surface of the modified PbO₂ electrodes is examined by scanning electron microscopy. The results show that SDS and CTAB when added in the electrolyte could refine the coating particles and change the roughness of the surface of the electrode leading to a thin film of PbO₂ with amorphous character. In addition, SDS and CTAB shift the hydrogen evolution potential towards more negative values, improve the discharge capacity of the anodic layer and accelerate the charge transfer. Under cathodic polarization, CTAB presents the lowest value of the charge transfer resistance R_ct. In the contrary, STPP shifts the oxygen evolution potential towards more positive values, passivates the surface of the electrode and inhibits completely the reaction of PbO₂ formation.     

Electrochemical and kinetic study of the coupling reaction between 4-nitroso and 4-hydroxylaminopyridine-1-oxide

The study of the reduction process of nitrosopyridine-1-oxide at platinum electrodes in aqueous solution by controlled potential coulometry is reported. The results obtained are consistent with the hypothesis that a pH dependent reaction takes place between the depolarizer and the reduction product. Such results have been confirmed by conventional kinetic experiments. The pH dependence of the rate constant can be accounted for in terms of a base catalyzed mechanism.     

The kinetics of the reversible chain reaction between 2,5-dichloroquinone and 4-hydroxydiphenylamine

The paper presents the results obtained in a study of the kinetics of the reversible chain reaction between 2,5-dichloroquinone and 4-hydroxydiphenylamine (K _eq = 3.2). We studied the dependence of the reaction rate on the concentrations of the initiator, initial reagents, and all products. The equations obtained earlier for the rate of reversible chain reactions and the method of equal concentrations suggested in this work were used to estimate the rate constants of most of the reaction mechanism elementary steps from the experimental data. The results obtained were shown to closely agree with and agument the data obtained earlier for the kinetics of the chain reaction between N-phenyl-1,4-benzoquinonemonoimine and 2,5-dichlorohydroquinone. On the whole, all the elementary steps of these two (forward and back) reversible chain reactions were characterized by rate constant values.     

Catalysis of reaction between ozone and 4-hydroxytoluene in acetic anhydride

Kinetics and products of 4-hydroxytoluene oxidation with ozone-air mixture in the presence of transition metal acetates as catalysts have been studied. Main steps of the catalytic series have been considered, and a mechanism of redox catalysis has been proposed which conforms to the experimental data and enables control over the direction, depth, and selectivity of the oxidation. Only manganese(II) acetate has been found to exhibit high catalytic activity in the presence of catalytic amounts of mineral acids. Manganese(II) acetate largely suppresses electrophilic reaction of ozone with the aromatic ring, so that the main reaction direction is oxidation of the methyl group with formation of 4-acetoxybenzyl acetate as the major product (62.6%) and 4-acetoxybenzylidene diacetate as a minor one (10.2%).     

Analysis of products of the thickening reaction between polyesters and magnesium oxide

The products of the reaction between MgO and polypropylene-glycol adipates of different acid values and water contents were analyzed for the water generated and the magnesium reacted into the resin by means of Karl Fischer titration and atomic absorption spectroscopy, respectively. The results conclusively show that both basic and neutral salts are present in the products. The ratio of the amounts of basic and neutral salts present in the mixture, r_B/N, could also be calculated from the results. It was found that as R, the moles of MgO added per mole of acid groups, is increased both the amount of oxide reacted and r_B/N increase while these are relatively unaffected by the water content of the resin. The minimum value of R at which basic salt exists in the reaction products was found to increase with decreasing acid value. It is proposed that diffusional effects account for these observations as well as those reported in literature.     

Kinetics and stoichiometry of the reaction between ozone and C70 fullerene in CCl4

The kinetics and stoichiometry of the reaction between C₇₀ fullerene and ozone have been studied. The reaction obeys a bimolecular rate law. The stoichiometric coefficients of the reaction are 1: 12 to 1: 22, depending on reaction conditions. The rate constant at 22°C is 5 × 10⁴ l mol^?1 s^?1 for the first stage of fullerene conversion and (0.8–0.6) × 10⁴ l mol^?1 s^?1 for the subsequent stages. Since the stages differ in terms of reaction rate, the original C₇₀ molecules are first involved in the reaction, whereas, at the subsequent stages, all molecules are involved with equal probabilities, irrespective of the number of preceding reaction events in which they have participated.     

Ein dreikerniger Zinkkomplex mit ZnS4‐, ZnS3O‐ und ZnS2NO‐Koordinationen

A Trinuclear Zinc Complex with ZnS₄, ZnS₃O, and ZnS₂NO Coordinations The reaction between the tris(thioimidazolyl)borate complex [Tt^tBuZn‐OClO₃] and 2‐pyridylbenzylalcohol (PBAH) yields the compound[(Tt^tBu)₃Zn₃(PBA)] (ClO₄)₂. In its trinuclear complex cation tris(thioimidazolyl)borate ligands, which adopt the umbrella conformation, bridge the zinc ions, which have the three different coordinations ZnS₄, ZnS₃O and ZnS₂NO.     

ZnS:Mn/ZnS量子点在DNA定量分析中的应用

以巯基乙酸为稳定剂,采用成核掺杂的方法在水溶液中一步制备得到具有核壳结构的ZnS:Mn/ZnS量子点.研究了荧光、室温磷光产生的机理.基于DNA对量子点发光的增强效应,以ZnS:Mn/ZnS量子点作为标记探针建立了测定DNA的荧光、室温磷光的分析方法.考察了量子点浓度、EDC/NHS用量和反应时间等条件对DNA测定的影响.结果表明,在最佳测定条件下,荧光、室温磷光两种分析方法测定小牛胸腺DNA的线性区间均为50 ～600 μg/L,检出限分别为39.6、28.5 μg/L,回收率分别为98% ～ 104%、99%～101%,25次重复测定300 μg/L ctDNA的相对标准偏差分别为3.1%、2.3%.该方法简单、安全、灵敏度高.     

Features of the Diels-Alder reaction between 9,10-diphenylanthracene and 4-phenyl-1,2,4-triazoline-3,5-dione

The Diels-Alder reaction between substituted anthracenes 1a?1j and 4-phenyl-1,2,4-triazoline-3,5 (2) is studied. In all cases except one, the reaction proceeds on the most active 9,10-atoms of substituted anthracenes. The orthogonality of the two phenyl groups at the 9,10-position of diene 1a is found to shield 9,10-reactive centers. No dienophiles with C=C bonds are shown to participate in the Diels-Alder reaction with 1a; however, the reaction 1a + 2 proceeds with the very active dienophile 2,4-phenyl-1,2,4-triazoline-3,5-dione. It is shown that attachment occurs on the less active but sterically accessible 1,4-reactive center of diene 1a. The structure of adduct 3a is proved by ¹H and ¹³C NMR spectroscopy and X-ray diffraction analysis. The following parameters are obtained for reaction 1a + 2 ? 3a in toluene at 25°C: K _eq = 2120 M^?1, ΔH _f ^≠ = 58.6 kJ/mol, ΔS _f ^≠ = ?97 J/(mol K), ΔV _f ^≠ = ?17.2 cm³/mol, ΔH _b ^≠ = 108.8 kJ/mol, ΔS _b ^≠ = 7.3 J/(mol K), ΔV _b ^≠ = ?0.8 cm³/mol, ΔH _r-n = ?50.2 kJ/mol, ΔS _r-n = ?104.3 J/(mol K), ΔV _r-n = ?15.6 cm³/mol. It is concluded that the values of equilibrium constants of the reactions 1a?1j + 2 ? 3a?3j vary within 4 × 10¹?10¹¹ M^?1.     

A DFT study of the polar Diels-Alder reaction between 4-aza-6-nitrobenzofuroxan and cyclopentadiene

The polar Diels-Alder reaction between 4-aza-6-nitrobenzofuroxan (ANBF) and cyclopentadiene has been studied using DFT procedures at the B3LYP/6-31G* level. Only one highly asynchronous transition state structure associated to the formation of the [4+2] adduct 13 is found. A further [3,3] sigmatropic shift on the [4+2] cycloadduct 13 allows its conversion into the thermodynamically more stable [2+4] cycloadduct 14. The analysis of the global and local electrophilicities of the reagents correctly explain the behaviour of ANBF as a strong electrophile in polar cycloadditions.     

Thermodynamic Stability Versus Kinetic Lability of ZnS4 Core

Density Functional Theory and post‐Hartree Fock calculations reveal an unusual energy profile for Zn? S and Zn? N bond dissociation reactions in several [Zn(SR)₄]^2? and [Zn(Im)(SR)₃]^? complexes. The Zn? S bond dissociation in tetrathiolate dianions, which is highly exothermic in the gas phase, proceeds through a late transition state which can be rationalized on the basis of an avoided crossing resulting from Coulomb repulsion between the anionic fragments and ligand‐to‐metal charge‐transfer in the [Zn(SR)₄]^2? complexes. When solvation models for water, DMSO, or acetonitrile are included, some complexes become stable while others are metastable, so this constitutes the first theoretical model which is in full agreement with the experimental data for various [Zn(SR)₄]^2?, [Zn(SR)₃]^?, and [Zn(Im)(SR)₃]^? complexes. The analysis given here indicates that the Zn(Cys)₄ and Zn(His)(Cys)₃ cores of numerous proteins are metastable with respect to Zn? S and Zn? N bond dissociation, respectively. This is consistent with the kinetic lability at the zinc‐centers and illustrates that in nature, thermodynamic stability is imparted upon the zinc cores by the protein environment.     

Proline-catalyzed diastereoselective direct aldol reaction between 4-oxoazetidine-2-carbaldehydes and ketones

The reaction of enantiopure 4-oxoazetidine-2-carbaldehydes with unmodified ketones was catalyzed by L-proline as well as by D-proline, to give the corresponding gamma-amino-beta-hydroxy ketones with good yields and diastereoselectivities. The obtained results implied that (2R,3R)-4-oxoazetidine-2-carbaldehydes and L-proline are a matched pair for diastereoselective induction.     

Study of interface diffusion and reaction between Zr3N4 and stainless steel

The effect of annealing treatment on the interface diffusion and reaction between Zr₃N₄/stainless steel was studied by AES depth profiling along with line shape analysis. The Zr₃N₄ film was deposited on stainless‐steel substrates by reactive magnetron sputtering. Scanning electron microscopy, electron diffraction, AES and UV–VIS reflection were performed to characterize the deposited film. The results indicated that the interface diffusion between Zr₃N₄ and stainless steel took place during deposition and can be promoted by annealing treatment, but no interface reaction took place before or after annealing treatment. High‐temperature and long‐time annealing treatment resulted in obvious oxidation of the Zr₃N₄ layer. The UV–VIS reflection results indicated that the absorption band of Zr₃N₄ film shifted to shorter wavelength after annealing treatment. Copyright © 2003 John Wiley & Sons, Ltd.