Terms Of Reaction Kinetics Research Articles

Ex-situ tracking solid oxide cell electrode microstructural evolution in a redox cycle by high resolution ptychographic nanotomography

For solid oxide fuel and electrolysis cells, precise tracking of 3D microstructural change in the electrodes during operation is considered critical to understand the complex relationship between electrode microstructure and performance. Here, for the first time, we report a significant step towards this aim by visualizing a complete redox cycle in a solid oxide cell (SOC) electrode. The experiment demonstrates synchrotron-based ptychography as a method of imaging SOC electrodes, providing an unprecedented combination of 3D image quality and spatial resolution among non-destructive imaging techniques. Spatially registered 3D reconstructions of the same location in the electrode clearly show the evolution of the microstructure from the pristine state to the oxidized state and to the reduced state. A complete mechanical destruction of the zirconia backbone is observed via grain boundary fracture, the nickel and pore networks undergo major reorganization and the formation of internal voids is observed in the nickel-oxide particles after the oxidation. These observations are discussed in terms of reaction kinetics, electrode mechanical stress and the consequences of redox cycling on electrode performance.

Investigation of ozonation kinetics and transformation products of sucralose

Sucralose is one of widely used artificial sweeteners, which has been ubiquitously detected in various water sources, such as wastewater and randomly in reservoir water. It is also reported to be persistent to various water treatment techniques. Although there are some studies on removal of sucralose by advanced oxidation process, limited information, in terms of reaction kinetics, transformation products and degradation pathway etc., was reported in its ozonation process. In this study, the reaction kinetics, removal efficiency, influence of pH, humic acid and carbonate on sucralose degradation by ozone, have been studied systematically. The results demonstrated that ozonation of sucralose was initiated by the formation of OH radical. Sucralose could be completely removed with excess O3 at neutral and basic conditions in ultrapure water. The rate of degradation decreased significantly in acidic condition and in the presence of carbonate and OH radical scavenger (e.g. tert-butanol). The acidity was the key factor affecting the degradation of sucralose. The rate constant was about 500 times higher at pH7 than that at pH4. Transformation products study indicated that the ozonation of sucralose were more complex than that in photolysis reaction. Although ozonation of sucralose was initiated by OH radical, both OH radical and O3 might be involved in the formation of transformation products and total organic carbon (TOC) removal. Various transformation products, such as aldehydes, carboxylic acids and probable chloride containing products, were identified and characterized in details. An ozonation degradation pathway of sucralose was proposed as well.

Application of the Initial Rate Method in Anaerobic Digestion of Kitchen Waste.

This article proposes a methane production approach through sequenced anaerobic digestion of kitchen waste, determines the hydrolysis constants and reaction orders at both low total solid (TS) concentrations and high TS concentrations using the initial rate method, and examines the population growth model and first-order hydrolysis model. The findings indicate that the first-order hydrolysis model better reflects the kinetic process of gas production. During the experiment, all the influential factors of anaerobic fermentation retained their optimal values. The hydrolysis constants and reaction orders at low TS concentrations are then employed to demonstrate that the first-order gas production model can describe the kinetics of the gas production process. At low TS concentrations, the hydrolysis constants and reaction orders demonstrated opposite trends, with both stabilizing after 24 days at 0.99 and 1.1252, respectively. At high TS concentrations, the hydrolysis constants and the reaction orders stabilized at 0.98 (after 18 days) and 0.3507 (after 14 days), respectively. Given sufficient reaction time, the hydrolysis involved in anaerobic fermentation of kitchen waste can be regarded as a first-order reaction in terms of reaction kinetics. This study serves as a good reference for future studies regarding the kinetics of anaerobic digestion of kitchen waste.

Quantitative Study of Electrochemical Reduction of Ag+ to Ag Nanoparticles in Aqueous Solutions by a Plasma Cathode

Replacing the solid metal cathode in an electrolytic cell with a plasma (gas discharge) allows the reduction of metal salt solutions to metal nanoparticles. Here, we apply gravimetric analysis to quantify the charge transfer (faradaic) efficiency of this reduction process and understand reaction pathways at the plasma-liquid interface. Silver powder synthesized from aqueous solutions of silver nitrate is collected and the weight is compared to the theoretical amount of silver obtained by applying Faraday's law of electrolysis. We find that the faradaic efficiencies are near 100% when the initial silver nitrate concentration is large (>100 mM), but are much less than 100% at low salt concentrations (<15 mM) or at high applied currents (>6 mA). These results are explained in terms of reaction kinetics involving solvated electrons and two important reactions: the reduction of silver ions (Ag+) and the second order recombination of solvated electrons which releases hydrogen gas.

High-pressure advantages in stoichiometric hydrogenation of carbon dioxide to methanol

Interplay between three important reaction parameters (pressure, temperature, and space velocity) in stoichiometric hydrogenation of carbon dioxide (CO2:H2=1:3) was systematically investigated using a commercial Cu/ZnO/Al2O3 catalyst. Their impacts on reaction performance and important ranges of process conditions toward full one-pass conversion of CO2 to methanol at high yield were rationalized based on the kinetics and thermodynamics of the reaction. Under high-pressure condition above a threshold temperature, the reaction overcomes kinetic control, entering thermodynamically controlled regime. Ca. 90% CO2 conversion and >95% methanol selectivity were achieved with a very good yield (0.9–2.4gMeOHgcat−1h−1) at 442bar. Such high-pressure condition induces the formation of highly dense phase and consequent mass transfer limitation. When this limitation is overcome, the advantage of high-pressure conditions can be fully exploited and weight time yield as high as 15.3gMeOHgcat−1h−1 could be achieved at 442bar. Remarkable advantages of high-pressure conditions in terms of reaction kinetics, thermodynamics, and phase behavior in the aim to achieve better methanol yield are discussed.

Development of a rapid recombinase polymerase amplification assay for the detection of Streptococcus pneumoniae in whole blood.

BackgroundStreptococcus pneumoniae is an important cause of microbial disease in humans. The introduction of multivalent vaccines has coincided with a dramatic decrease in the number of pneumococcal-related deaths. In spite of this, at a global level, pneumococcal infection remains an important cause of death among children under 5 years of age and in adults 65 years of age or older. In order to properly manage patients and control the spread of infection, a rapid and highly sensitive diagnostic method is needed for routine implementation, especially in resource-limited regions where pneumococcal disease is most prevalent.MethodsUsing the gene encoding leader peptidase A as a molecular diagnostics target, a real-time RPA assay was designed and optimised for the detection of S. pneumoniae in whole blood. The performance of the assay was compared to real-time PCR in terms of its analytical limit of detection and specificity. The inhibitory effect of human genomic DNA on amplification was investigated. The potential clinical utility of the assay was investigated using a small number of clinical samples.ResultsThe RPA assay has a limit of detection equivalent to PCR (4.0 and 5.1 genome equivalents per reaction, respectively) and was capable of detecting the equivalent of <1 colony forming unit of S. pneumoniae when spiked into human whole blood. The RPA assay was 100 % inclusive (38/38 laboratory reference strains and 19/19 invasive clinical isolates) and 100 % exclusive; differentiating strains of S. pneumoniae species from other viridans group streptococci, including S. pseudopneumoniae. When applied to the analysis of a small number (n = 11) of clinical samples (blood culture positive for S. pneumoniae), the RPA assay was demonstrated to be both rapid and sensitive.ConclusionsThe RPA assay developed in this work is shown to be as sensitive and as specific as PCR. In terms of reaction kinetics, the RPA assay is shown to exceed those of the PCR, with the RPA running to completion in 20 minutes and capable generating a positive signal in as little as 6 minutes. This work represents a potentially suitable assay for application in point-of-care settings.

Electrochemical Characterization of Li4Ti5O12 By Single Particle Measurements Using a Particle - Current Collector Integrated Microelectrode

A single particle measurement is known as a characterization method of electrode material [1]. In a conventional single particle measurement, electrical contact between a microelectrode and an electrode particle is made while observing with an optical microscope. Although the conventional single particle measurement can be electrochemically performed under an optical microscope by contacting the single active material particle with a Pt microfilament, the applicability of this technique is limited with respect to the size and shape of particles. Recently, we overcame the problem by using “a particle - current collector integrated microelectrode” , in which the single active material particle was directly-bonded on the tip of the microelectrode [2]. In this study, new measurement systems were constructed using the integrated microelectrode embedded in a three-electrode flange cell and a constant temperature bath in order to evaluate the electrochemical properties of Li4Ti5O12 (LTO) single particle, which includes the temperature dependency of the electrode kinetics. Particle - current collector integrated microelectrodes were prepared as follows using a focused ion beam process unit (FIB): After attaching a tungsten probe coated with fluorinated resin to a manipulator in the FIB, the tip of the probe was cut off to expose the inner conductive probe. An ionic beam of platinum was positioned and deposited on contact between the top of the cut probe and a single LTO particle. The particle - current collector integrated microelectrode as the working electrode was assembled in a three-electrode flange cell with Li metals as the counter and reference electrodes. The electrolyte employed was 1mol/L Li(TFSI)/EC+PC(1:1 v/v%). Electrochemical measurements of the LTO single particle were carried out at 10 oC -40 oC. Cyclic voltammograms of LTO single particle exhibited the well-defined reversible redox peaks at around 1.55V vs. Li/Li+ when the scan was initiated from reduction direction. The obtained phenomenon, higher anodic peak current than cathodic peak current, is indicative of faster reaction during Li+ extraction (i.e. discharge) than Li+ insertion (i.e. charge). At 40 oC, single LTO particle was found to deliver its 95% capacity upon discharge at 1000C. On the contrary, the capacity retention upon charge at 1000C retained only 37%. These tendencies in charge/discharge were also confirmed at all temperatures tested. In this presentation, the peculiar reaction behavior mentioned above will be discussed in terms of reaction kinetics of LTO with lithium, through electrochemical impedance spectroscopies at various temperatures.

Stress reduction mechanisms during photopolymerization of functionally graded polymer nanocomposite coatings

From the experimental analysis of the photocuring process in terms of reaction kinetics as well as modulus and shrinkage build-up, the residual stresses arising during the photopolymerization of functionally graded composite coatings based on an acrylate matrix and Fe3O4@SiO2 core@shell nanoparticles are evaluated through a Finite Element Modeling approach. Owing to the monotonous variation of volume fraction of the constituent phases that influences the local conversion of the polymeric matrix, these coatings are able to decrease the residual stresseS at the coating/substrate interface by as much as approximate to 25% compared to those encountered in composites with homogeneous compositions, and by as much as approximate to 40% compared to those arising in the pure polymer. The influence of substrate stiffness, nanoparticle stiffness and conversion degree of the polymer matrix was also analyzed, providing further information for the optimization of the stress reduction mechanism in graded nanocomposite coatings. (C) 2015 Elsevier B.V. All rights reserved.

Digestibility and structural parameters of spray-dried casein clusters under simulated gastric conditions

The digestibility of casein clusters prepared from sodium caseinate solution (plain or pH-adjusted (pH=6.0)) was studied. The prepared solutions were spray-dried at different inlet air temperatures (150°C and 180°C), and the properties (i.e. encapsulation efficiency, surface hydrophobicity, and digestibility) of the resultant powders were investigated. The specimens obtained from the pH-adjusted solution had higher encapsulation efficiencies than the specimens obtained from the plain solution. A higher spray-drying temperature resulted in lower encapsulation efficiencies and higher surface hydrophobicities. Simulated gastric digestion tests were carried out to study the digestibility of the obtained casein clusters, which was analyzed in terms of reaction kinetics and structural changes during digestion. The effects of drying temperature and pH on the amount of casein digested were not significant; that is, approximately 30% of casein was digested in 120min for all specimens. Small-angle and ultra-small-angle X-ray scattering measurements were used to analyze the structure of the obtained clusters and their changes during digestion. The results suggested that all the obtained casein clusters, with an average size of approximately 428nm, had a rough, fractal-structured surface with many dense primary clusters. These structures changed during digestion; specifically, the cluster size increased both in the overall diameter and on the primary structure scale. The fractal characteristics changed from surface to mass fractals, and simultaneously, the cluster density decreased. The drying temperature affected the cluster size during digestion, and the trends were different in the specimens obtained from the plain and pH-adjusted solutions. These results could be useful in the design of protein-based encapsulation systems with desirable digestibility and bioavailability.

Comparison of preparation methods for iron–alumina oxygen carrier and its reduction kinetics with hydrogen in chemical looping combustion

ABSTRACTSeven preparation methods, namely sol‐gel, co‐precipitation, hydrothermal synthesis, low heating solid‐state reaction, freeze granulation, combustion synthesis, and mechanical mixing, were used to synthesize Fe2O3/Al2O3 oxygen carrier for chemical looping combustion. A comprehensive physicochemical characterization (i.e. productivity, crushing strength, crystalline characteristics, microstructure, and chemical reactivity with hydrogen) was carried out, and the effects of preparation methods and processes on the oxygen carrier performance were explored. Taking into consideration various physicochemical indices, the sol‐gel method and the freeze granulation method were preferred for oxygen carrier preparation. Following that, a critical chemical reaction in in situ gasification chemical looping combustion, the reduction reaction between oxygen carrier and hydrogen, was clarified in terms of reaction kinetics through the non‐isothermal kinetics analysis and the double extrapolation method. Temperature programmed reduction experiments of the sol‐gel‐derived Fe2O3/Al2O3 particle and hydrogen were performed using a chemisorption analyzer. The reduction mechanisms and kinetics parameters for the two‐stage reaction (reduced from Fe2O3 to Fe3O4 and then from Fe3O4 to FeAl2O4) were determined. In the first stage, the reduction reaction is described by the surface reaction model with an order of 2; on the other hand, the conversion from Fe3O4 to FeAl2O4 is dominated by the nucleation and nuclei growth process. © 2014 Curtin University of Technology and John Wiley &amp; Sons, Ltd.

Kinetic Modeling of the Influence of NO on the Combustion Phasing of Gasoline Surrogate Fuels in an HCCI Engine

In this work, a chemical kinetic model describing the nitric oxide (NO) sensitization effect for the oxidation of toluene reference fuels has been developed. The influence of NO on combustion phasing in a homogeneous charge compression ignition (HCCI) engine has then been studied by kinetic modeling and compared to experiments. An iso-octane/n-heptane blend, a toluene/n-heptane mixture, and a full boiling range gasoline using a three-component surrogate fuel consisting of 55% iso-octane, 23% toluene, and 22% n-heptane by liquid volume have been simulated under two different operating conditions with NO concentrations from 4 up to 476 ppm. All three fuels have the same research octane number of 84. The first operating condition has a high intake pressure (2 bar absolute) and low intake temperature (40 °C). The other operating condition has a high intake temperature (100 °C) and atmospheric intake pressure. The model predicts in accordance with experimental observations that, at high intake pressure in the primary reference fuels (PRF) case, the ignition delay is retarded beyond the baseline case (absence of NO in intake) for a high concentration of NO, while for toluene reference fuels (TRF) and the full boiling range gasoline, the combustion phasing is advanced with an increasing NO concentration. The reason for the differences between TRF and PRF fuels is that the promoting effect of toluene is stronger than the one for iso-octane when the NO concentration is increased. This is further explained in terms of reaction kinetics. For PRF, there is a net production of HONO (nitrous acid), which is chain-terminating, whereas for TRF, there is a net consumption of HONO, which is chain-branching. Calculations of fuel sensitivity on the ignition delay time for a gasoline surrogate fuel indicate that it is possible to control the combustion phasing in a gasoline HCCI engine by simultaneously varying the amount of NO (EGR) and the fraction of aromatics and iso-paraffins.

A review of nitrate reduction using inorganic materials

In a biological denitrification system for water and wastewater treatment, an external carbon source (electron donor) is usually needed to generate dedicated microbial communities if intrinsic organic substances are insufficient. Alternative sources of electron donors, especially inorganic donors, are becoming more and more attractive in order to replace or reduce carbon use. In this article, inorganic electron donors, i.e. zero-valent iron, ferrous ion, sulphur and hydrogen are reviewed. While carbon dioxide (greenhouse gas) is produced when organic electron donors are used, inorganic electron donors have the potential advantages to reduce a plant's carbon footprint, and prevent carbon eluting out of the system, as occurs with heterotrophic processes. While sulphur and hydrogen are promising for nitrate removal in terms of reaction kinetics and economical feasibility, zero-valent iron and ferrous ion show potential to be utilized as a supplement to heterotrophic denitrification, where it is anticipated that synergistic effects would occur with autotrophic and heterotrophic denitrification, and thus external carbon consumption can be reduced.

In-depth study on aminolysis of poly(ɛ-caprolactone): Back to the fundamentals

The aminolysis can effectively introduce primary amine (−NH2) groups onto polyester materials, enabling a variety of subsequent surface biofunctionalization reactions. However, less attention has been paid to the basic knowledge of aminolysis reaction in terms of reaction kinetics and its influences on materials properties. In this study, taking the widely used poly(ɛ-caprolactone) (PCL) as a typical example, the influences of diamines and solvent property on the surface −NH2 density are firstly assessed by using X-ray photoelectron spectroscopy (XPS) and colorimetric analysis. Results show that smaller diamine molecules and nonpolar alcohols could accelerate the reaction. The reaction kinetics with 1,6-hexanediamine is further investigated as a function of temperature, reaction time, and diamine concentration. During the initial stage, the reaction shows a 1st order kinetics with the diamine concentration and has an activation energy of 54.5 kJ/mol. Ionization state of the −NH2 groups on the PCL surface is determined, revealing that the pKa of −NH3+ (<5) is much lower than that of the corresponding diamine molecules in solution. After aminolysis, surface hydrophilicity of PCL membrane is significantly enhanced, while surface elastic modulus and average molecular weight are decreased to some extent, and others such as weight, surface morphology and bulk mechanical strength are not apparently changed. The introduced −NH2 groups are found to be largely lost at 37 °C, but can be mostly maintained at low temperature.

Nickel-Layer Protected, Carbon-Coated Sulfur Electrode for Lithium Battery

In this paper we report the characterization of a nickel-layer protected carbon-coated sulfur as positive electrode for lithium battery. The electrode is prepared by annealing sulfur and pitch-carbon in argon atmosphere followed by mechanical treatment. The electrode is further covered by a thin layer of nickel metal by using electron beam physical vapor deposition (EBPVD). The structure and the morphology of the electrode are first characterized by scanning electron microscopy (SEM) and by X-ray diffraction (XRD), while the electrochemical characteristics are studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic cycling in lithium cells. The results demonstrated that the synthesis procedure greatly enhances the S-C cathode electrochemical properties in both terms of reaction kinetics and capacity retention. These improvements are attributed to the increasing of the electrode conductivity and to the reduction of the polysulfides dissolution. In this paper we propose a new approach to make the sulfur electrode a valid candidate cathode for high energy density lithium batteries.

Waste Heat Recovery System through Methanol Steam Reforming with Absorption Heat Pump

Through the methanol steam reforming (MSR), the energy of low temperature waste heat (100-150°C) can be recovered into that of hydrogen. However, actual MSR requires over 200°C to enable the high conversion of methanol into hydrogen in terms of reaction kinetics. Thus, in this research, a waste heat recovery system through MSR with absorption heat pump (AHP) was proposed. The role of the AHP is to enhance the temperature level of the waste steam up to 230°C, which is used for the MSR. The endothermic reaction of the MSR decreases the temperature of the MSR reactor. Therefore, high temperature steam should be used not only for the MSR reaction but also for heating the MSR reactor. To evaluate the performances of the system, "enthalpy enhancement factor" was defined. As a result, the recovered enthalpy of the waste heat was almost 4.5 times as much as the required work for the AHP when the waste heat temperature was 150°C and S/C ratio was 4.0.

CO and O2 Binding to Pseudo-tetradentate Ligand−Copper(I) Complexes with a Variable N-Donor Moiety: Kinetic/Thermodynamic Investigation Reveals Ligand-Induced Changes in Reaction Mechanism

The kinetics, thermodynamics, and coordination dynamics are reported for O(2) and CO 1:1 binding to a series of pseudo-tetradentate ligand-copper(I) complexes ((D)LCu(I)) to give Cu(I)/O(2) and Cu(I)/CO product species. Members of the (D)LCu(I) series possess an identical tridentate core structure where the cuprous ion binds to the bispicolylamine (L) fragment. (D)L also contains a fourth variable N-donor moiety {D = benzyl (Bz); pyridyl (Py); imidazolyl (Im); dimethylamino (NMe(2)); (tert-butylphenyl)pyridyl (TBP); quinolyl (Q)}. The structural characteristics of (D)LCu(I)-CO and (D)LCu(I) are detailed, with X-ray crystal structures reported for (TBP)LCu(I)-CO, (Bz)LCu(I)-CO, and (Q)LCu(I). Infrared studies (solution and solid-state) confirm that (D)LCu(I)-CO possess the same four-coordinate core structure in solution with the variable D moiety "dangling", i.e., not coordinated to the copper(I) ion. Other trends observed for the present series appear to derive from the degree to which the D-group interacts with the cuprous ion center. Electrochemical studies reveal close similarities of behavior for (Im)LCu(I) and (NMe(2))LCu(I) (as well as for (TBP)LCu(I) and (Q)LCu(I)), which relate to the O(2) binding kinetics and thermodynamics. Equilibrium CO binding data (K(CO), ΔH°, ΔS°) were obtained by conducting UV-visible spectrophotometric CO titrations, while CO binding kinetics and thermodynamics (k(CO), ΔH(double dagger), ΔS(double dagger)) were measured through variable-temperature (193-293 K) transient absorbance laser flash photolysis experiments, λ(ex) = 355 nm. Carbon monoxide dissociation rate constants (k(-CO)) and corresponding activation parameters (ΔH(double dagger), ΔS(double dagger)) have also been obtained. CO binding to (D)LCu(I) follows an associative mechanism, with the increased donation from D leading to higher k(CO) values. Unlike observations from previous work, the K(CO) values increased as the k(CO) and k(-CO) values declined; the latter decreased at a faster rate. By using the "flash-and-trap" method (λ(ex) = 355 nm, 188-218 K), the kinetics and thermodynamics (k(O(2)), ΔH(double dagger), ΔS(double dagger)) for O(2) binding to (NMe(2))LCu(I) and (Im)LCu(I) were measured and compared to those for (Py)LCu(I). A surprising change in the O(2) binding mechanism was deduced from the thermodynamic ΔS(double dagger) values observed, associative for (Py)LCu(I) but dissociative for (NMe(2))LCu(I) and (Im)LCu(I); these results are interpreted as arising from a difference in the timing of electron transfer from copper(I) to O(2) as this molecule coordinates and a tetrahydrofuran (THF) solvent molecule dissociates. The change in mechanism was not simply related to alterations in (D)LCu(II/I) geometries or the order in which O(2) and THF coordinate. The equilibrium O(2) binding constant (K(O(2)), ΔH°, ΔS°) and O(2) dissociation rate constants (k(-O(2)), ΔH(double dagger), ΔS(double dagger)) were also determined. Overall the results demonstrate that subtle changes in the coordination environment, as occur over time through evolution in nature or through controlled ligand design in synthetic systems, dictate to a critically detailed level the observed chemistry in terms of reaction kinetics, structure, and reactivity, and thus function. Results reported here are also compared to relevant copper and/or iron biological systems and analogous synthetic ligand-copper systems.

Investigation of the influence of pressure on the combustion of Alpagut lignite

This research presents the combustion behavior of lignite under different reaction pressures. Lignite from Alpagut, Corum of Turkey was combusted in its run off mine (ROM) condition under three different pressure levels of 172, 345, 517 kPa (25, 50, 75 psi). Experiments were done in a fully controlled temperature regime in an isolated combustion tube that operated in coordination with a continuous gas analyzer. Combustion behavior of lignite under different pressures was characterized by effluent gas analysis method. The changes in the amounts of consumed oxygen, evolved carbon oxides as well as variations in the temperature were assessed. The combustion efficiency and effectiveness of lignite was evaluated in terms of thermal features, from the viewpoint of reaction kinetics and by the computation of instantaneous fuel consumption at critical points. It was seen that combustion of lignite tended to turn from a steady profile to a considerably rapid one with increase in pressure, proving to be highly sensitive to the applied pressure level. Also, different levels of pressure resulted in distinctive combustion behavior not only from the view of thermal characteristics, but also in terms of reaction kinetics.

Synthesis and reactivity of copper(i) complexes with an ethylene-bridged bis(imidazolin-2-imine) ligand

A series of copper(I) complexes with a sterically hindered, bidentate ligand, BL iPr, derived from an N-heterocyclic carbene precursor have been isolated, characterized and their reactivity studied. The ethylene-bridged bis(imidazolin-2-imine) ligand (BL iPr) provides strongly donating N-donor atoms for the stabilization of a copper(I) metal center, priming it for reactivity. The complexes [(BL iPr)Cu(XyNC)]PF6 (4) and [(BL iPr)CuCl] (5) were characterized by X-ray crystallography and exhibit trigonal coordination at the copper centers. The reactivity of [(BL iPr)Cu]SbF6 toward dioxygen was studied at low temperature, indicating formation of a thermally sensitive intermediate with intense UV/Vis features and an isotope-sensitive vibration at 625 cm(-1) (599 cm(-1) with 18 O2). The intermediate is assigned as containing the bis(mu-oxo)dicopper(III) core, [2](PF6)2, and the related, stable hydroxo form was crystallized as [{(BL iPr)Cu}2(mu-OH)2](PF6)2, [3](PF6)2. The reactivity of 5 as a catalyst for the ATR polymerization of styrene was assessed in terms of reaction kinetics and polymer properties, with low PDI values achieved for polymers with molecular weights up to 30 000 g mol(-1).

SIMS analysis of intentional in situ arsenic doping in CdS/CdTe solar cells

A series of CdTe/CdS devices with different tris(dimethylamino)arsine (TDMAAs) partial pressures were grown by metal organic chemical vapour deposition (MOCVD) to investigate the incorporation of arsenic into the bulk. Characterization of the growth layers using secondary ion mass spectrometry (SIMS) showed arsenic concentrations ranging from 1 × 1016 to 1 × 1019 atoms cm−3. A square law dependence of arsenic concentration on the TDMAAs vapour concentration was observed. A reaction mechanism for the decomposition of TDMAAs precursor via dimerization is presented and discussed in terms of reaction kinetics.

Effect of Heavy Metals on Dechlorination of Carbon Tetrachloride by Iron Nanoparticles

Effects of heavy metals on the dechlorination of carbon tetrachloride by iron nanoparticles were investigated in terms of reaction kinetics and product distribution using batch systems. Removal of heavy metals and the interaction between heavy metals and iron nanoparticles at the iron surface were also examined. It was found that Cu(II) enhanced the carbon tetrachloride dechlorination by iron nanoparticles and led to produce more benign products (i.e., CH4). Pb(II) may increase reduction rate slightly but also increase the production of more toxic intermediates such as dichloromethane. In comparison to the iron reduction system without heavy metals, effects of As(V) were negligible while Cr(VI) decreased the dechlorination rate by a factor of 2. Removal of As(V) by iron nanoparticles behaved pseudo-first-order reaction kinetics but a fast initial removal followed by a slow subsequent process was found in the cases of Cu(II) and Pb(II). Scanning electron microscopy-energy dispersive X-ray (SEM-EDX) analysis indicated the deposition of heavy metals onto the iron surface. X-ray diffraction (XRD) analysis showed Cu(II) was reduced to metallic copper and cuprite (Cu2O) at the iron surface while no reduced lead species was observed from the Pb(II)-treated iron nanoparticles. Limited data suggested an oxidized lead species formed. The enhanced dechlorination by Cu(II) can be attributed to the deposition of metallic copper and cuprite at the iron surface. This study suggests that implementation of iron nanoparticles rather than engineered bimetallic iron nanoparticles for remediation of mixed contamination with both chlorinated organics and heavy metals is sufficient.