Isolation of Bisphenol A-Tolerating/degrading Shewanella haliotis Strain MH137742 from an Estuarine Environment

Applied Biochemistry and Biotechnology - The human exposure to bisphenol A (BPA) occurs frequently. Once, this compound was one of the highest volume chemicals produced worldwide and used as a...     

Probing the Catalytic Activity of Reduced Graphene Oxide Decorated with Au Nanoparticles Triggered by Visible Light

Hybrid materials in which reduced graphene oxide (rGO) is decorated with Au nanoparticles (rGO–Au NPs) were obtained by the in situ reduction of GO and AuCl₄^?_(aq) by ascorbic acid. On laser excitation, rGO could be oxidized as a result of the surface plasmon resonance (SPR) excitation in the Au NPs, which generates activated O₂ through the transfer of SPR‐excited hot electrons to O₂ molecules adsorbed from air. The SPR‐mediated catalytic oxidation of p‐aminothiophenol (PATP) to p,p′‐dimercaptoazobenzene (DMAB) was then employed as a model reaction to probe the effect of rGO as a support for Au NPs on their SPR‐mediated catalytic activities. The increased conversion of PATP to DMAB relative to individual Au NPs indicated that charge‐transfer processes from rGO to Au took place and contributed to improved SPR‐mediated activity. Since the transfer of electrons from Au to adsorbed O₂ molecules is the crucial step for PATP oxidation, in addition to the SPR‐excited hot electrons of Au NPs, the transfer of electrons from rGO to Au contributed to increasing the electron density of Au above the Fermi level and thus the Au‐to‐O₂ charge‐transfer process.     

Ionic relaxation in nematic liquid crystal cells

We investigate the dependence of the relaxation time of the current flowing in a nematic cell submitted to an external dc voltage on the physical properties of the substrate. We show that previously presented analyses of the same problem are not very useful for practical applications. We compare our theoretical predictions with experimental data, and show that the agreement is rather good. The influence of the adsorption-desorption phenomenon on the relaxation time is also discussed.     

Study of the reciprocal space image of the biaxial nematic phase in the plane of the amphiphilic bilayer

High resolution synchrotron X-ray measurements have been performed on the uniaxial and biaxial phases of the lyotropic mixture potassuim laurate, decanol and water. An elegant magnetic orientational procedure allows us to obtain the cut of the reciprocal space image of the biaxial phase at the plane perpendicular to the amphiphilic bilayer. The analysis of densitometric profiles of the diffracted bands indicate an anisotropic micellar correlation in the plane of the amphiphilic bilayer. It is suggested that an anisotropic distribution of decanol and potassium laurate in this plane could be responsible for this effect.     

Evidence of shear-dependent boundary slip in newtonian liquids

The European Physical Journal E - The flow of Newtonian fluids was studied by directly measuring the hydrodynamic drainage force acting on a sphere approaching a flat surface. Our force...     

Evaluation and application of bismuth as an internal standard for the determination of lead in wines by simultaneous electrothermal atomic absorption spectrometry

A method for the direct determination of Pb in wines by simultaneous multi-element atomic absorption spectrometry (SIMAAS) using a transversely heated graphite atomizer, Zeeman-effect background corrector and internal standardization is proposed. Bismuth was used as an internal standard and Pd(NO3)2 plus Mg(NO3)2 as chemical modifier to stabilize both the analyte and the internal standard. The implementation of two pyrolysis steps avoided any build-up of carbonaceous residues on the graphite platform. All diluted samples (1 + 1 v/v) in 0.2% v/v HNO3 and reference solutions (5.0-50 microg l(-1) Pb in 0.2% v/v HNO3) were spiked with 25 microg l(-1) Bi. For a 20 microl aliquot dispensed into the graphite tube, a good correlation (r = 0.9997) was obtained between the ratio of the analyte signal to the internal standard signal and the analyte concentration of the reference solutions. The electrothermal behaviour of Pb and Bi in red, white and rosé wines were compared. In addition, absorbance variations due to changes in experimental conditions, such as atomizer temperature, integration time, injected sample volume, radiation beam intensity, graphite tube surface, dilution and sample composition, were minimized by using Bi as internal standard. Relative standard deviations of measurements based on integrated absorbance varied from 0.1 to 3.4% and from 0.5 to 7.3% (n = 12) with and without internal standard correction, respectively. Good recoveries (91-104%) for Pb spikes were obtained. The characteristic mass was 45 pg Pb and the limit of detection based on integrated absorbance was 0.9 microg l(-1) Pb. Internal standardization increased the lifetime of the tube by 25%. Direct determinations of Pb in wines with and without internal standardization approaches were in agreement at the 95% confidence level. The repeatability and the tube lifetime were improved when using Bi as internal standard. The improvement in accuracy using an internal standard was only observed when the analytical results were affected by errors.     

Thermal lens spectrometric determination of hexavalent chromium

The applicability of thermal lens spectrometry (TLS) for quantification and routine determination of hexavalent chromium was investigated by using a collinear dual beam thermal lens spectrometer. In aqueous solutions the LOD of 0.1 μg l⁻¹ was obtained for Cr(VI) by using 160 mW laser power. The performance of the technique was verified by the determination of hexavalent chromium in standard reference water samples (NIST SRM 1643a and NIST SRM 1643c) and comparing the results for Cr(VI) in CCA (Cr, Cu, As)-treated timber extracts to concentrations obtained by atomic absorption spectrometry (AAS). Good agreement between the TLS results and reported values for Cr(VI) in SRMs as well as AAS results for Cr(VI) in CCA-treated timbers confirmed that TLS is a reliable and accurate analytical technique applicable for the determination of Cr(VI) in aqueous solutions at concentration levels 0.5–100 μg l⁻¹.     

Use of the internal standardization for difficult sampling by graphite furnace atomic absorption spectrometry

This work shows the potentiality of As as internal standard to compensate errors from sampling of sparkling drinking water samples in the determination of selenium by graphite furnace atomic absorption spectrometry. The mixture Pd(NO₃)₂/Mg(NO₃)₂ was used as chemical modifier. All samples and reference solutions were automatically spiked with 500 μg l⁻¹ As and 0.2% (v/v) HNO₃ by the autosampler, eliminating the need for manual dilutions. For 10 μl dispensed sample into the graphite tube, a good correlation (r=0.9996) was obtained between the ratio of analyte absorbance by the internal standard absorbance and the analyte concentrations. The relative standard deviations (R.S.D.) of measurements varied from 0.05 to 2% and from 1.9 to 5% (n=12) with and without internal standardization, respectively. The limit of detection (LD) based on integrated absorbance was 3.0 μg l⁻¹ Se. Recoveries in the 94-109% range for Se spiked samples were obtained. Internal standardization (IS) improved the repeatability of measurements and increased the lifetime of the graphite tube in ca. 15%.     

Reductive sulfur extrusion reaction of 2,1,3-benzothiadiazole compounds: a new methodology using NaBH4/CoCl2·6H2O(cat) as the reducing system

A new simple and efficient methodology for reductive sulfur extrusion from 2,1,3-benzothiadiazole compounds has been developed using NaBH₄ in the presence of catalytic amounts of CoCl₂·6H₂O (1 mol %). This method is an efficient alternative for the generation of various 1,4-disubstituted-2,3-diaminobenzene derivatives from 4,7-disubstituted-2,1,3-benzothiadiazoles. The diamines can be easily converted into 4,7-disubstituted-quinoxaline compounds by simple reaction with glyoxal-sodium bisulfite.