Preparation of cuprous oxides with different sizes and their behaviors of adsorption,visible-light driven photocatalysis and photocorrosion

Cuprous oxide (Cu₂O) nanoparticles and microparticles have been prepared by liquid phase chemical synthesis. The samples were characterized by means of SEM, XRD, UV/DRS and XPS. It was presented that as-prepared Cu₂O nanoparticles are substantially stable in ambient atmosphere and the Cu⁺ as main state exists on the surface of Cu₂O nanoparticles. As-prepared Cu₂O microparticles can exist stably as a Cu₂O/CuO core/shell structure; and the Cu²⁺ as main state exists on the surface of Cu₂O microparticles. The behaviors of adsorption, photocatalysis and photocorrosion of Cu₂O particles with different sizes were investigated in detail. The results show that Cu₂O nanoparticles are very easy to photocorrosion during the photocatalytic reaction, which cannot be used as photocatalyst directly to degrade organic compound, although as-prepared Cu₂O nanoparticles exhibit special property of adsorption. Cu₂O microparticles have a higher photocatalytic activity than Cu₂O nanoparticles because of its slower photocorrosion rate, although Cu₂O microparticles have much lower adsorption capacity than Cu₂O nanoparticles. The mechanisms of photocatalysis and photocorrosion for Cu₂O under visible light were also discussed.     

Simultaneous Sensing of H2O,D2O and HOD through Peroxo Vibrations

Detection of HOD simultaneously in the presence of a mixture of H₂O and D₂O is still an experimental challenge. Till date, there is no literature report of simultaneous detection of H₂O, D₂O and HOD based on vibrational spectra. Herein we report simultaneous quantitative detection of H₂O, D₂O and HOD in the same reaction mixture with the help of bridged polynuclear peroxo complex in absence and presence of Au nanoparticles on the basis of a peroxide vibrational mode in resonance Raman and surface enhanced resonance Raman spectrum. We synthesize bridged polynuclear peroxo complex in different solvent mixture of H₂O and D₂O. Due to the formation of different nature of hydrogen bonding between peroxide and solvent molecules (H₂O, D₂O and HOD), vibrational frequency of peroxo bond is significantly affected. Mixtures of different H₂O and D₂O concentrations produce different HOD concentrations and that lead to different intensities of peaks positioned at 897, 823 and 867 cm⁻¹ indicating H₂O, D₂O and HOD, respectively. The lowest detection limits (LODs) were 0.028 mole fraction of D₂O in H₂O and 0.046 mole faction of H₂O in D₂O. In addition, for the first time the results revealed that the cis-peroxide forms two hydrogen bonds with solvent molecules.     

First-principles study on the effect of arsenic impurity on oxidation of pyrite surfaces

Arsenic (As) frequently exists in pyrite (FeS₂) in the form of impurities. The oxidation behavior of As in FeS₂ is important in environmental science, mineral processing, and other related fields. The adsorption behaviors of H₂O and O₂ molecules on the As-bearing pyrite (100) surface (As FeS₂(100)) are studied using the density functional theory (DFT). The results show that As prefers the S site on the pyrite (100) surface (FeS₂(100)). In the absence of O₂, an isolated H₂O molecule does not dissociate when adsorbed at an iron (Fe) site and is repelled at an As site. Furthermore, the surface area around the As atoms exhibits a hydrophobic behavior. Adsorption energy analysis reveals that the presence of As atoms is unfavorable for the adsorption of H₂O molecules on the pure FeS₂ surface, and that the adsorption of H₂O molecules on the As FeS₂(100) is physical adsorption. In the absence of H₂O, it is suggested that the O₂ molecule easily dissociates on both the pure FeS₂(100) and As FeS₂(100). The adsorption of O₂ on the As-bearing surface is weaker than that on the pure FeS₂(100). For the co-adsorption of H₂O and O₂, the adsorption energy on the As-bearing surface is more negative than that on the pure surface. This indicates that the presence of As promotes surface oxidation. Additionally, two  OH and O (AsO or SO) or  O (Fe O) species are formed on the surface of pyrite when the H₂O molecule is dissociated.     

Kinetic and mechanistic studies of the iridium(III) catalyzed oxidation of sulphanilic acid by diperiodatocuprate(III) in aqueous alkaline medium

The effect of La₂O₃, K₂O and Li₂O on the properties and catalytic performance of silica-supported nickel catalysts for the hydrogenation of m-dinitrobenzene was investigated. The catalysts promoted with La₂O₃, Li₂O and K₂O showed better catalytic performance than the catalyst without promotion, especially the ones co-promoted with La₂O₃ and K₂O or Li₂O.     

Preparation of MXene-Cu2O nanocomposite and effect on thermal decomposition of ammonium perchlorate

MXenes are novel graphene-like 2-D materials. Cu₂O is an effective additive for thermal decomposition of ammonium perchlorate (AP). We reported the synthesis of MXene (Ti₃C₂), Cu₂O and MXene-Cu₂O respectively. The samples were characterized by means of X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Results indicate that the MXene is composed of lots of nano-sheets and the thickness is 30 ± 10 nm, and Cu₂O nanoparticles nucleate and grow heterogeneously directly on the surface of MXene. The effect of these MXene, Cu₂O and MXene-Cu₂O samples on the thermal decomposition of AP were investigated using TG-DSC. The results revealed that MXene-Cu₂O have a great influence on the thermal decomposition of AP than that of pure MXene and Cu₂O.     

Modeling of density of aqueous solutions of amino acids with the statistical associating fluid theory

The density of aqueous solutions of amino acids has been modeled with the statistical associating fluid theory (SAFT) equation of state. The modeling is accomplished by extending the previously developed new method to determine the SAFT parameters for amino acids. The modeled systems include α-alanine/H₂O, β-alanine/H₂O, proline/H₂O, l-asparagine/H₂O, l-glutamine/H₂O, l-histidine/H₂O, serine/H₂O, glycine/H₂O, alanine/H₂O/sucrose, dl-valine/H₂O/sucrose, arginine/H₂O/sucrose, serine/H₂O/ethylene glycol, and glycine/H₂O/ethylene glycol. The density of binary solutions of amino acids has been correlated or predicted with a high precision. And then the density of multicomponent aqueous solutions of amino acids has been modeled based on the modeling results of binary systems, and a high accuracy of density calculations has been obtained. Finally, the water activities of dl-valine/H₂O, glycine/H₂O, and proline/H₂O have been predicted without using binary interaction parameters, and good results have been obtained.     

Mössbauer spectrometica analysis of thermal decomposition products of phosphate and oxalate coatings on steel

The deterioration of zinc, zinc—calcium and manganese phosphate coatings and oxalate coatings on steel on heating was investigated by conversion electron Mössbauer spectrometry. and the chemical change of the coatings was analysed on the basis of the thermal characteristics of Zn₃(PO₄)₂·4H₂O, Zn₂Fe(PO₄)₄·4H₂O, CaZn₂(PO₄)₂·2H₂O, Fe₃(PO₄)₂·8H₂O. (Mn, Fe)₅H₂(PO₄)₄·4H₂O and FeC₂O₄·2H₂O. The steel substrate beneath the coatings influenced the thermal decomposition and evaporation of coating materials under the various heating atmospheres. The heat resistance of these coatings and the state of the substrate were also investigated.     

Electrochemical Formation of Fe(IV)=O Derived from H2O2 on a Hematite Electrode as an Active Catalytic Site for Selective Hydrocarbon Oxidation Reactions

The high-valence iron species (Fe(IV)=O) in the cytochrome P450 enzyme superfamily is generated via the activation of O₂, and serves as the active center of selective hydrocarbon oxidation reactions. Furthermore, P450 can employ an alternate route to produce Fe(IV)=O, even from H₂O₂ without O₂ activation. Meanwhile, Fe(IV)=O has recently been revealed to be the reactive intermediate during H₂O oxidation to O₂ on hematite electrodes. Herein, we demonstrated the generation of Fe(IV)=O on hematite electrodes during the electrochemical oxidative decomposition of H₂O₂ using in situ UV-visible absorption spectra. The generation of Fe(IV)=O on hematite electrodes from H₂O₂ exhibited 100 mV lower overpotential than that from H₂O. This is because H₂O₂ serves not only as the oxygen source of Fe(IV)=O, but also as the additional oxidant. Finally, we confirmed that the Fe(IV)=O generated on hematite electrodes can serve as the catalytic site for styrene epoxidation reactions.     

The 18O signature of biogenic nitrous oxide is determined by O exchange with water

To effectively mitigate emissions of the greenhouse gas nitrous oxide (N₂O) it is essential to understand the biochemical pathways by which it is produced. The ¹⁸O signature of N₂O is increasingly used to characterize these processes. However, assumptions on the origin of the O atom and resultant isotopic composition of N₂O that are based on reaction stoichiometry may be questioned. In particular, our deficient knowledge on O exchange between H₂O and nitrogen oxides during N₂O production complicates the interpretation of the ¹⁸O signature of N₂O. Here we studied O exchange during N₂O formation in soil, using a novel combination of ¹⁸O and ¹⁵N tracing. Twelve soils were studied, covering soil and land‐use variability across Europe. All soils demonstrated the significant presence of O exchange, as incorporation of O from ¹⁸O‐enriched H₂O into N₂O exceeded their maxima achievable through reaction stoichiometry. Based on the retention of the enrichment ratio of ¹⁸O and ¹⁵N of NO into N₂O, we quantified O exchange during denitrification. Up to 97% (median 85%) of the N₂O‐O originated from H₂O instead of from the denitrification substrate NO. We conclude that in soil, the main source of atmospheric N₂O, the ¹⁸O signature of N₂O is mainly determined by H₂O due to O exchange between nitrogen oxides and H₂O. This also challenges the assumption that the O of N₂O originates from O₂ and NO, in ratios reflecting reaction stoichiometry. Copyright © 2008 John Wiley & Sons, Ltd.     

Photocatalytic activity of Cu2O nanoparticles prepared through novel synthesis method of precursor reduction in the presence of thiosulfate

A novel fabrication of Cu₂O nanoparticles was successfully achieved through the reduction of Cu²⁺ in the interlayer of montmorillonite (denoted as MT). The Cu₂O nanoparticles formed in the clay interlayer (denoted as Cu₂O/MT) had a lamellate shape of 20–100 nm in width and ca. 0.39 nm in thickness, and thus, the Cu₂O/MT exhibited a higher specific surface area than neat Cu₂O. The Cu₂O/MT was applied to a photocatalyst, and its photocatalytic activity was examined in terms of water reduction (i.e., H₂ evolution) in the presence of methanol (electron donor). The Cu₂O/MT showed a high photocatalytic activity in comparison with neat Cu₂O; moreover, the photocatalytic activity was improved by loading a Pt catalyst onto the surface of Cu₂O. Based on the dependencies of photocatalytic activity on light intensity as well as methanol concentration, it was revealed that the H₂ evolution from water on Cu₂O/MT is the rate-determining step. Thus, the active and efficient photocatalysis of Cu₂O/MT was associated with an increase in specific surface area corresponding to the number of active sites.     

Coordinate Structures of PrIII, GdIII, TmIII, and YbIII Complexes with Nitrilotriacetic Acids

The crystal and molecular structures of the [Pr^III(nta)(H₂O)₂]·H₂O (nta = nitrilotriacetic acids), K₃[Gd^III(nta)₂(H₂O)]·6H₂O, and K₃[Yb^III(nta)₂]·5H₂O complexes have been determined by single-crystal X-ray structure analyses. In [Pr^III(nta)(H₂O)₂]·H₂O, the Pr^IIINO₈ part forms a nine-coordinate pseudo-monocapped square antiprismatic structure in which one N and three O atoms are from one nta ligand in the same molecule, three O atoms from another nta ligand in the neighboring molecule and two O atoms from two coordinate water molecules. In K₃[Gd^III(nta)₂(H₂O)]·6H₂O, the [Gd^III(nta)₂(H₂O)^3- complex anion has a nine-coordinate pseudo-monocapped square antiprismatic structure in which each nta acts as a tetradentate ligand with one N atom of the amino group and three O atoms of the carboxylic groups. In K₃[Yb^III(nta)₂]·5H₂O, each nta also acts as a tetradentate ligand with one N atom of amino group and three O atoms of the carboxylic groups, but the [Yb^III(nta)₂ ^3- complex anion has an eight-coordinate structure with a distorted square antiprismatic prism. All the results including those for [Tm^III(nta)(H₂O)₂]·2H₂O confirm the inferences on the coordinate structures and coordination numbers of rare earth metal complexes with the nta ligand.     

An 17O nuclear quadrupole double resonance study of several crystal hydrates

Using the technique of double resonance with coupled multiplets (DRCM), ¹⁷O double resonance signals were detected in natural abundance from the H₂O molecule in the hydrates BeSO₄ · 4H₂O, AlCl₃ · 6H₂O, CH₃COOLi · 2H₂O, LiClO₄ · 3H₂O, Sr(OH)₂ · H₂O, Ba(OH)₂ · 8H₂O, LiBr · 2H₂O and MgSO₄ · 7H₂O.Using the DRCM technique approximate values for the HOH bond angle and the OH bond length were determined from the dipolar structure present on the ¹⁷O double resonance signals. A Townes and Dailey analysis was used to examine the small differences in the ¹⁷O quadrupole coupling constants and asymmetry parameters between these samples.     

Recent Advances in Catalytic Decomposition of N<Subscript>2</Subscript>O on Noble Metal and Metal Oxide Catalysts

Catalytic decomposition of nitrous oxide (N₂O) is one of the most efficient methods for the removal of N₂O which is of high greenhouse potential and ozone-depleting property. Recent progress in the decomposition of N₂O has been reviewed with the focus on noble meal and metal oxide catalysts. The influence factors, such as catalyst support, preparation method, alkali metal additives and the reaction conditions (including O₂, H₂O, SO₂, NO and CO₂), on the performance of deN₂O catalysts have been discussed. Finally, future research direction for the catalytic decomposition of N₂O is proposed.     

Spectral effects of the clusterization of greenhouse gases: Computer experiment

Autocorrelation functions of the total dipole moment of clusters composed of H₂O and N₂O molecules are calculated in terms of the molecular dynamics method. The IR absorption and reflection spectra of systems composed of (H₂O)_i, N₂O(H₂O)_i, and (N₂O)₂(H₂O)_i clusters (2 ≤ i ≤ 20) are obtained on the basis of these functions. Frequency-dependent dielectric permittivity of clusters increases after the absorption of N₂O molecules. The absorption coefficient of cluster systems with trapped N₂O molecules increases at low frequencies and decays at frequencies ω > 500 cm^?1. The inclusion of N₂O molecules increases also reflection coefficient R and changes the pattern of R(ω) spectra. The absorption of IR radiation increases with the number of H₂O molecules in clusters. Dielectric losses also increase with an increase in i number upon the absorption of N₂O molecules. The number of electrons interacting with an incident electromagnetic wave increases upon the capture of N₂O molecules.     

废水生物脱氮工艺中N2O排放数学模型研究进展

N_2O是一种重要的温室气体,而污水生物脱氮处理过程是N_2O的潜在产生源之一。随着污水处理量和处理程度的不断提高,N_2O的排放量也将不断增大。建立N_2O排放数学模型对污水生物脱氮系统中N_2O生成机制的深入研究和污水处理行业N_2O削减工艺技术的开发具有重大的理论及实践意义。本文归纳了生物脱氮工艺的原理,系统阐述了生物脱氮工艺中N_2O的生成机理和排放数学模型的类型、建立方法及应用情况。在此基础上,对生物脱氮工艺中N_2O排放数学模型的研究现状和研究方向进行了总结和展望,以期为N_2O排放数学模型的完善、N_2O排放量的削减、污水生物脱氮工艺的优化及污水处理行业的可持续发展提供理论基础和科学依据。     

Synthesis and application of a new copper(II) complex containing oflx and leof

Two new copper(II) complexes of [Cu(Ofloxacin)(phen)(H₂O)] · (NO₃) · 2H₂O and [Cu(Levofloxacin)(phen)(H₂O)] · (NO₃) · 2H₂O were obtained and their structures were studies. Both ligands and complexes were assayed against gram-positive and gram-negative bacteria by the in vitro doubling dilutions method. The inhibitory effect of the ligands and complexes on the leukemia HL-60 cell line were measured with the MTT assay method and the liver cancer HePG-2 cell line measured by the SRB method. The results indicated that the complexes have stronger inhibitory effect on HL-60 than on HePG-2. The complex [Cu(Levofloxacin)(phen)(H₂O)] · (NO₃) · 2H₂O (I) has stronger effect on HL-60 than the complex (Cu(Ofloxacin)(phen)(H₂O)] · (NO₃) · 2H₂O (II). The text was submitted by the authors in English.     

Water vapor pressure and thermodynamics of dehydration of Group 2 perchlorate hydrates

The limits of existence for Group 2 perchlorate hydrates are defined. The water vapor pressure is measured over the crystal hydrates Mg(ClO₄)₂·2H₂O, Ca(ClO_{4 2}·4H₂O, Sr(ClO₄)₂·3H₂O, Sr(ClO₄)₂·2H₂O, Sr(ClO₄)₂·H₂O, Ba(ClO₄)₂·3H₂O, and Ba(ClO₄)₂·H₂O. The water vapor pressure and thermodynamics constants of dehydration depend directly on the electron-acceptor strength of the cation.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1467–1473, July, 1990.     

Importance of Pd and Pt excited states in N2O capture and activation: A comparative study with Rh and Au atoms

Nitrous oxide (N₂O) is an intermediate compound formed during catalysis occurring in automobile exhaust pipes. In this work, the N₂O capture and activation by Pt and Pd atoms in the ground and excited states of many multiplicities are studied. Pt and Pd + N₂O reactions are studied at multireference second‐order perturbation level of theory using C_s symmetry. The PtN₂O (¹A′, ⁵A′, and ⁵A″) species are spontaneously created from excited states. Only the ⁵A′ and ⁵A″ states exhibit N₂O activation reaction paths when N₂O approaches Pt end‐on by the N or O atoms side or side‐on yielding NO or N₂ as products, respectively. Pt⁺ cations ground and excited states, capture N₂O, although only Pt⁺ (⁶A′ and ⁶A″) states show N₂O activation yielding O and N₂ as products. In the Pd atom case, PdN₂O (¹A′ and ⁵A″) species are also spontaneously created from excited states. The ⁵A″ state exhibits N₂O activation yielding N₂ + O as products. Pd⁺ cations in both ground and excited states capture N₂O; however, only the [PdN₂O]⁺ (⁴A′, ⁴A″, ⁶A′, and ⁶A″) states in side‐on approaches and (⁶A′) in end‐on approach activate the N₂O and yield the N₂ bounded to the metal and O as product. The results obtained in this work are discussed and compared with previous calculations of Rh and Au atoms. The reaction paths show a metal–gas dative covalent bonding character. Löwdin charge population analyses for Pt and Pd active states show a binding done through charge donation and retrodonation between the metals and N₂O. © 2013 Wiley Periodicals, Inc.     

A study of N2O decomposition rate constant at high temperature: Application to the reduction of nitrous oxide by hydrogen

Atomic resonance absorption spectroscopy has been used to investigate the thermal decomposition of N₂O by monitoring the formation of O atoms behind reflected shock waves in the temperature range 1490–2490 K and at total pressures from 58 to 347 kPa, by using the mixtures of N₂O highly diluted in Ar. For the chosen experimental conditions, the rate coefficient k_1,0 for the reaction N₂O + Ar → N₂ + O + Ar had the greatest effect on the O atom concentration increase, so this reaction rate constant could be deduced by comparison between experiment and computed simulation. In the actual temperature range, we found k_1,0 (cm³ mol^?1s^?1) = 7.2 × 10¹⁴ exp(?28878/T(K)), with an overall uncertainty evaluated to be less than 20%, by considering all the parameters, which contributed to uncertainties in the rate constant determination. The possible absorption at the O triplet emission line of N₂O has been investigated. The absorption cross section of N₂O at the O line has been estimated and taken into account for the determination of k_1,0 at high concentrations of N₂O and at temperatures lower than 1850 K. The effect of the presence of impurities like H₂O on rate constant determination has been examined and was found to be negligible. The choice of the rate coefficient for the consumption of O atoms by reaction with N₂O and that of the high‐pressure limiting rate coefficients k_1,∞ were also discussed. The rate constant reported in the present study was compared with the literature values and was found to be overall higher than those determined experimentally by other teams in the last decade. Finally, the effect of the modified constant value on reaction rate of diluted Ar–N₂O mixtures and H₂–N₂O–Ar systems was investigated. In the temperature range 1500–2500 K, the use of the rate constant deduced from this study has led to a better prediction of N₂O decomposition and N₂O reduction by H₂ than with lower rate constants proposed in the literature. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 357–375, 2009     

Synthesis,isomerization, and polymerization of mixed phosphoranimines

A series of phosphites were prepared bearing various combinations of phenoxy, methoxy, and trifluoroethoxy substituents. (PhO)₃P, (CF₃CH₂O)(PhO)₂P, (CF₃CH₂O)₂(PhO)P, and (CH₃OCH₂CH₂O)(PhO)₂P were polymerized during the course of the Staudinger reaction with azidotrimethylsilane to form low molecular weight polyphosphazenes. Similar reactions with (CH₃O)(CF₃CH₂O)₂P, (CH₃O)(PhO)₂P, (CH₃O)₂(CF₃CH₂O)P, (CH₃O)₂(PhO)P, and (CH₃O)₃P produced the desired phosphoranimine as well as the corresponding phosphoramidate isomer. Studies were performed on these systems in order to understand the nature of this isomerization. (CH₃O)(PhO)₂P (DOUBLE BOND) N (SINGLE BOND) Si(CH₃)₃ and (CH₃O)₂(PhO)P (DOUBLE BOND) N (SINGLE BOND) Si(CH₃)₃ polymerize at temperatures above 150°C. © 1996 John Wiley & Sons, Inc.