Mechanism and experimental study on the photocatalytic performance of Ag/AgCl @ chiral TiO2 nanofibers photocatalyst: the impact of wastewater components

© 2014 Elsevier B.V.The effect of the water matrix components of a secondary effluent of a urban wastewater treatment plant on the photocatalytic activity of Ag/AgCl @ chiral TiO2 nanofibers and the undergoing reaction mechanisms were investigated. These effects were evaluated through the water components-induced changes on the net rate of hydroxyl radical (•OH) generation and modeled using a relative rate technique. Dissolved organic matter DOM (k=-2.8×108M-1s-1) scavenged reactive oxygen species, Cl- (k=-5.3×108M-1s-1) accelerated the transformation from Ag to AgCl (which is not photocatalytically active under visible-light irradiation), while Ca2+ at concentrations higher than 50mM (k=-1.3×109M-1s-1) induced aggregation of Ag/AgCl and thus all of them revealed inhibitory effects. In contrast, NO3- (k=6.9×108M-1s-1) and CO32- (k=3.7×108M-1s-1) improved the photocatalytic activity of Ag/AgCl slightly by improving the rate of HO• generation. Other ubiquitous secondary effluent components including SO42- (k=3.9×105M-1s-1), NH3+ (k=3.5×105M-1s-1) and Na+ (k=2.6×104M-1s-1) had negligible effects. 90% of 17-α-ethynylestradiol (EE2) spiked in the secondary effluent was removed within 12min, while the structure and size of Ag/AgCl @ chiral TiO2 nanofibers remained stable. This work may be helpful not only to uncover the photocatalytic mechanism of Ag/AgCl based photocatalyst but also to elucidate the transformation and transportation of Ag and AgCl in natural water

MRX776316_Supplemental_Material - Male Migration and Female Labor Market Attachment: New Evidence From the Mexican Family Life Survey¹

<p>MRX776316_Supplemental_Material for Male Migration and Female Labor Market Attachment: New Evidence From the Mexican Family Life Survey¹ by Qing Wang in International Migration Review</p

PbS Quantum Dots Capped with Amorphous ZnS for Bulk Heterojunction Solar Cells: The Solvent Effect

In this study, two distinct structures of PbS quantum dots (QDs) are produced with amorphous ZnS as the capping material by successive ionic layer adsorption and reaction. With methanolic solution, spherical PbS QDs (∼5 nm) are embedded in the ZnS matrix (i.e., embedding structure), exhibiting relatively large distance between the QDs. With aqueous solution, irregularly shaped PbS QDs (<3 nm) blend intimately with the ZnS medium (i.e., blending structure), showing indiscernible QD spacing. This is attributed to a relatively low reactivity of Pb²⁺ ions in water, suppressing quantum dot growth in the mesopores. Bulk heterojunction of mesoporous TiO₂ substrate filled up with the blending configuration shows superior photovoltaic performance to the embedding architecture, because of the small QD size and close distance between the QDs

Ionic Liquid Facilitates the Conjugative Transfer of Antibiotic Resistance Genes Mediated by Plasmid RP4

The dissemination and propagation of antibiotic resistance genes (ARGs) is an emerging global health concern. In our previous study, the ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm]­[PF6]) had been proven to facilitate the dissemination of ARGs via horizontal gene transfer. In this study, we further confirm that this compound facilitates the horizontal transfer of plasmid RP4 through a conjugation mechanism and not by natural transformation. The mechanisms for [BMIm]­[PF6] promoting conjugative transfer are attributable to enhancing the mRNA expression levels of conjugative and global regulatory genes, as well as by inhibiting the genes that are responsible for the vertical transfer of cell growth. [BMIm]­[PF6] significantly enhanced the expression of the outer membrane porin proteins (OMPs) OmpC and OmpA and the corresponding mRNA expression levels of <i>omp</i>C and <i>omp</i>A genes in recipient bacteria, which contributed to pore formation and increased cell membrane permeability. The increased expression of pilin and pili allowed the donor pilus to attach to and access the recipient cells, thereby assisting cell-to-cell contact to facilitate the conjugative transfer of plasmid RP4. To the best of our knowledge, this is the first insightful exploration of [BMIm]­[PF6] facilitating the conjugative transfer of ARGs mediated by plasmid RP4 and of several other ILs with different cations or anions that are capable of promoting plasmid transfer. It is therefore suggested that the application of some ILs in industrial processes should be carefully evaluated before their bulk emission into the environment

Preparation, Evaluation and Application of a Novel Reversed-Phase/Zwitterionic/Hydrophilic Interaction Liquid Chromatographic Mixed-Mode Stationary Phase

<p>The present study described the preparation and application of a reversed-phase/zwitterionic/hydrophilic interaction liquid chromatography stationary phase, named as SIL-PS. The SIL-PS was prepared through a four-step reaction, chemical bonding, nucleophilic addition, SN1 substitution and sulfonation on the silica matrix. It was featured with C₁₂ alkyl chain, quaternary ammonium, tertiary amine and sulfonate groups. After SIL-PS was packed into the stainless column (150 mm × 2.1 mm i.d.), chromatographic parameters, including acetonitrile content, pH and ionic strength of the mobile phase, and the column temperature, were systematically investigated to study the retention mechanism. Eletrostatic adsorptive/repulsive, partition and hydrogen-bonding interactions were demonstrated to contribute to the retention. The stability of the SIL-PS was satisfactory, with relative standard deviations of retention factors of 1.93%, 2.08% and 1.90% for loxoprofen, adenosine and liquiritin, respectively. Additionally, to investigate the separation selectivity, the non-steroidal anti-inflammatory drugs, nucleobases/nucleotides and alkaloids/glycosides were separated; the HPLC fingerprinting of the <i>Cortex phellodendri</i> extract was also conducted, and the separation performance was superior to that of the C18 column in terms of peak shape, resolution and analytical time. The results revealed that the prepared SIL-PS possessed multi functionalities for multi retention and could be promising for complicated samples.</p

Kinetics of Li_<i>x</i>FePO₄ Lithiation/Delithiation by Ferrocene-Based Redox Mediators: An Electrochemical Approach

An electrochemical approach for studying the kinetics of reactions between redox mediators and Li-ion battery electrode materials has been developed. The approach is based on a simple diffusion-reaction model, similar to that used to describe the classical catalytic electrochemical–chemical (EC′) reaction mechanism. Using this approach it is possible to determine the diffusion length of redox mediators in a porous film made from a Li-ion battery electrode material. The rate constant for reaction between redox species and the porous electrode may then be calculated. The approach is applied to determine rate constants for the disappearance of ferrocene and dibromoferrocenium due to reaction with excess pristine and carbon-coated Li_<i>x</i>FePO₄ (0 ≤ <i>x</i> ≤ 1) nanoparticulate films (porosity ∼0.63, BET surface area 20–30 m² g^–1) and excess Li⁺ (0.1 M), which are of relevance to the operation of the recently introduced redox-flow Li-ion battery. Pseudo-first-order volumetric rate constants in the range 1–6 s^–1 were obtained, corresponding to apparent heterogeneous rate constants in the range 2.2 × 10^–6 – 4.4 × 10^–6 cm s^–1, which we show are fast enough not to limit the charge/discharge rate of redox flow Li-ion batteries constructed from these materials

Determination of Sensitizer Regeneration Efficiency in Dye-Sensitized Solar Cells

Regeneration of the sensitizing dye in dye-sensitized solar cells (DSCs) is frequently studied using the transient absorption (TA) technique. However, TA measurements are generally not performed using complete DSCs at the maximum power point (MPP) on the current–voltage (<i>j–V</i>) characteristic, and the electron concentration in the nanocrystalline TiO₂ films used in these devices is often not well characterized, which may lead to results that are not relevant to actual solar cell operation. Here, dye regeneration kinetics were studied at the MPP and at open circuit (where interpretation of results is simpler) in DSCs employing a “robust” nonvolatile 3-methoxypropionitrile-based electrolyte solution. Using a combination of TA, differential incident photon-to-current efficiency measurements, and impedance spectroscopy, the dependence of electron–dye recombination rate and overall sensitizer regeneration efficiency on TiO₂ electron concentration is unambiguously demonstrated. We also examine the validity of a commonly used approach for determining regeneration efficiency in which the electron–dye recombination rate constant is estimated from TA decays of cells employing a redox-inactive electrolyte solution. We find evidence that this widespread practice may be unsuitable for accurate determination of the regeneration rate constant or efficiency. We go on to show that, despite near-quantitative regeneration at short circuit or low photovoltage, power conversion efficiency is limited by inefficient regeneration in stable DSCs with practically relevant electrolyte solutions

The TBEs are required for the synergistic activation of ANF promoter by myocardin and Tbx5.

<p>(<b>A</b>) COS-7 cells were transfected with myocardin and Tbx5 expression plasmids and the indicated ANF promoter luciferase reporters in which the CArG boxes and the T-box factor-Binding Elements (TBEs) were indicated, and luciferase activity measured. (<b>B</b>) COS-7 cells were transfected with an ANF promoter luciferase reporter (ANF115) or a mutant reporter in which the TBE was mutated (ANF155m) together with myocardin and Tbx5 expression plasmids and luciferase activity measured. (<b>C</b>) COS-7 cells were transfected with an ANF promoter luciferase reporter (ANF115) (left three lanes) or a mutant reporter in which the CArG box was mutated (right three lanes) together with myocardin and Tbx5 expression plasmids and luciferase activity measured. (<b>D</b>) COS-7 cells were transfected with an ANF promoter luciferase reporter (ANF638) (left three lanes) or a mutant reporter in which both CArG boxes were mutated (ANF638m) (right three lanes) together with myocardin and Tbx5 expression plasmids and luciferase activity measured. (<b>E</b>) A luciferase reporter controlled by four tandemly repeats of a consensus Tbx binding elements (TBE) was transfected into COS-7 cells with myocardin and/or Tbx5 expression plasmids and luciferase activity measured. In all the experiments, the luciferase activity was determined 48 hr after transfection and was presented as relative luciferase activity in which the control was assigned a value of 1. Data represent the mean ± s.d. from at least three independent experiments in duplicate. *P<0.05.</p

Tbx5 and myocardin do not form a stable ternary complex on CArG-box or TBE.

<p>Myc-tagged Tbx5 and Flag-tagged myocardin proteins were expressed by <i>in vitro</i> transcription and translation and incubated with radiolabeled probes. (<b>A</b>) Electrophoresis mobility shift assays were performed with a ³²P-labeled TBE probe for Myc-tagged Tbx5 in the presence and absence of increasing amount of Flag-myocardin. Anti-Myc antibodies were applied for supershift. The Tbx5/TBE complexes and the supershift complex were indicated. (<b>B</b>) Electrophoresis mobility shift assays were performed with a ³²P-labeled CArG probe for Flag-myocardin in the presence and absence of SRF, or in the presence and absence of Myc-Tbx5. Anti-SRF antibodies were applied for supershift. The SRF/CArG complexes (SRF), the Myocd/SRF/CArG ternary complexes (SRF+Myocd) and supershift complex (Supershift) were indicated.</p

Mapping of the myocardin and Tbx5 interaction domains.

<p>(<b>A</b>) COS-7 cells were transfected with expression plasmids encoding Myc-tagged Tbx5 and a collection of Flag-tagged myocardin deletion mutants. Tbx5 was immunoprecipitated (IP) by anti-Myc antibodies, and anti-Flay antibodies were used to detect the presence of myocardin in the immunoprecipitates by immunoblot analysis (IB) (upper panel). One-fifteenth of cell extracts were directly immunoblotted (IB) to detect the presence of myocardin and Tbx5 proteins by anti-Flag or anti-Myc antibodies, respectively (middle and lower panels, respectively). (<b>B</b>) A schematic summary of myocardin and Tbx5 protein interaction domains. Myocardin domains abbreviated as follows: B, basic domain; Q, a stretch of glutamine residues; SAP, <u>S</u>AF A/B, <u>A</u>cinus, <u>P</u>IAS domain; TAD, transactivation domain. (<b>C</b>) COS-7 cells were transfected with expression plasmids encoding Flag-tagged myocardin and a collection of Myc-tagged Tbx5 deletion mutants. Myocardin was immunoprecipitated (IP) by anti-Flag antibodies, and anti-Myc antibodies were used to detect the presence of Tbx5 in the immunoprecipitates by immunoblot (IB) analysis (upper panel). One-fifteenth of cell extracts were directly immunoblotted (IB) to detect the presence of Tbx5 and myocardin proteins by anti-Myc or anti-Flag antibodies, respectively (middle and lower panels, respectively). (<b>D</b>) A schematic summary of myocardin and Tbx5 protein interaction domains.</p