Electrochemical characterization of core@shell CoFe2O4/Au composite

Quantum dots (QDs) have received considerable attention due to their unique optical and electrical properties. Although substantial research has focused on the potential applications and toxicological impacts of QDs, far less effort has been directed toward understanding their fate and transport in the environment. In this work, the effect of four coatings, polyethylene glycol functionalized polymer (PEGP), carboxyl derivatized polymer (COOHP), linoleic acid (LA), and polyacrylic acid-octylamine (PAA-OA), on the transport and retention of QDs in porous media were evaluated under environmentally relevant conditions. Aqueous QD suspensions (ca. 10 nM) were introduced into water-saturated columns packed with 40–50 mesh Ottawa sand at a pore-water velocity of 7.6 m/day. At an ionic strength (IS) of 3 mM and pH of 7, PEGP-coated QDs were completely retained within the column, while more than 60 % of COOHP-coated QDs were transported through a column run under identical conditions. When PAA-OA and LA were used as coatings, effluent QD recoveries increased to more than 65 and 89 % of the injected mass, respectively. Additionally, a decrease in pH from 9.5 to 5.0, or an increase of IS from 0 to 30 mM reduced the eluted mass of PAA-OA-coated QDs by more than 2 and 15 times, respectively. The relative mobility of coated QDs (LA > PAA-OA > COOHP > PEGP) was consistent with total interaction energy profiles between QDs and sand surfaces calculated based on Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. At an IS of 3 mM (NaCl) and pH 7, a linear correlation was obtained between the fraction of eluted QDs and the magnitude of the primary interaction energy barrier. These findings demonstrate the strong dependence of QD transport on coating type and indicate that interaction energies based on DLVO theory can be used to predict the relative mobility of QDs in porous media.     

Pyrrole-Annulated Heterocyclic Systems. Synthesis of 2H-Pyrrolo[3,4-b][1,5]benzothiazepine 4,4-Dioxide Derivatives

Condensation of 2-nitrothiophenol with ethyl propiolate afforded 3-(2-nitrophenylthio)propenoate. Oxidation of sulfur atom to sulfone group gave ethyl 3-(2-nitrophenylsulfonyl)propenoate, which underwent condensation with tosyl methylisocyanide (TosMIC) to yield ethyl 4-(2-nitrophenylsulfonyl)pyrrole-3-carboxylate. Reduction of nitro group afforded ethyl 4-(2-aminophenylsulfonyl)-1H-pyrrole-3-carboxylate, which was cyclized to 2H-pyrrolo[3,4-b][1,5] benzothiazepin-10(9H)-one 4,4-dioxide. Similar procedure was used for the synthesis of 9,10-dihydro-10-methyl-2H-pyrrolo[3,4-b][1,5]benzothiazepine 4,4-dioxide.     

Microwave-assisted oxidation of silibinin: a simple and preparative method for the synthesis of improved radical scavengers

A new and preparative oxidation of silibinin has been developed to give access to two different silibinin derivatives known for their enhanced antioxidant properties. Conventional heating methods were compared with results obtained from microwave (MW) heating. The base-catalysed oxidation of silibinin under MW heating is a very efficient method for the preparation of 2,3-dehydrosilybin and a related silybin rearrangement product. This latter compound shows enhanced radical scavenging properties. Optimised conditions were used to prepare 2,3-dehydrosilybins A and B from optically pure silybins A and B. An efficient, preparative purification method was also developed to enable isolation of different products in high purity.     

Majolica ware in the New Spain: an evaluation through NAA

The results of a study about Majolica ceramics recovered from three sites located in Mexico City are here presented. The set of 83 samples includes several local ceramic-types dating from the Colonial Period, the nineteenth century and the present day, plus some foreign specimens and clay samples from the Puebla area. Fourteen chemical elements present in the samples were analyzed and measured by means of neutron activation, and statistically the following groups were established: two groups that were presumably manufactured in Mexico City, two from Puebla, one from outside the Mexican boundaries, most probably Sevilla-Triana pottery, plus three more groups from unidentified origins. It was also found out that botijas were both imported and produced domestically. These results are discussed against the relevant literature on known provenance, chronology and manufacture standards of this kind of pottery.     

Application of an innovative matrix solid-phase dispersion–solid-phase extraction–liquid chromatography–tandem mass spectrometry analytical methodology to the study of the metabolism of the estrogenic mycotoxin zearalenone in rainbow trout liver and muscular tissue

The metabolic fate of the estrogenic mycotoxin zearalenone in rainbow trout is presently unknown. In this study, the tissue concentration of zearalenone and its principal metabolites (α-zearalenol and β-zearalenol) was determined. A known amount of zearalenone was administered as a single bolus to ten fish, and the biological tissue concentration was determined at various times following administration. The analytes were extracted from liver and muscular tissue using an on-line matrix solid-phase dispersion–solid-phase extraction sample preparation protocol, and their concentration determined by HPLC–Turboionspray–tandem mass spectrometry. The results showed that zearalenone is mainly metabolized into α-zearalenol in both liver and muscular tissues. The maximum concentrations of each analyte found in liver were 76.1, 211.2 and 63.7?ng/g respectively for zearalenone, α-zearalenol and β-zearalenol, while in muscular tissue they were 10.7, 8.2 and 6.5?ng/g. These values were reached after 2?h in liver tissue and 12?h in muscular tissue. Moreover the data obtained showed that the elimination rate in liver is quite fast since 48?h after the exposure less than 7% of the maximum concentration found is still present. In muscular tissue, however, about one-third of the maximum concentration found is still present after 48?h.     

Interaction between ions and substituted buckybowls: A comprehensive computational study

Complexes formed by substituted buckybowls derived from corannulene and sumanene with sodium cation or chloride anion have been computationally studied by using a variety of methods. Best results have been obtained with the SCS‐MP2 method extrapolated to basis set limit, which reproduces the highest‐level values obtained with the MP2.X method. All bowls form stable complexes with chloride anion, with stabilities ranging from ?6 kcal/mol in the methylated corannulene derivative to ?45 kcal/mol in the CN‐substituted sumanene. The opposite trend is observed in sodium complexes, going from deeply attractive complexes with the methylated derivatives (?36 kcal/mol with sumanene derivative) to slightly repulsive ones in the CN‐substituted bowls (2 kcal/mol in the corannulene derivative). Anion complexes are stabilized by large electrostatic interactions combined with smaller though significant dispersion and induction contributions. Conversely, cation complexes are stabilized by large induction contributions capable of holding together the bowl and the cation even in cases where the electrostatic interaction is repulsive. The effect of substitution is mainly reflected on changes in the molecular electrostatic potential of the bowl and, thus, in the electrostatic contribution to the interaction. Therefore, the variations in the stability of the complexes on substitution could be roughly predicted just considering the changes in the electrostatic interaction. However, other contributions also register changes mainly as a consequence of displacements on the position of the ion at the minimum, so the accurate prediction of the stability of this kind of complexes requires going further than the electrostatic approach. © 2014 Wiley Periodicals, Inc.     

Water-Assisted Concerted Proton-Electron Transfer at Co(II)-Aquo Sites in Polyoxotungstates With Photogenerated RuIII(bpy)33+ Oxidant

The cobalt substituted polyoxotungstate [Co₆(H₂O)₂(α-B-PW₉O₃₄)₂(PW₆O₂₆)]¹⁷⁻ ( Co6 ) displays fast electron transfer (ET) kinetics to photogenerated Ru^III(bpy)₃³⁺, 4 to 5 orders of magnitude faster than the corresponding ET observed for cobalt oxide nanoparticles. Mechanistic evidence has been acquired indicating that: (i) the one-electron oxidation of Co6 involves Co(II) aquo or Co(II) hydroxo groups (abbreviated as Co6(II) −OH ₂ and Co6(II) −OH, respectively, whose speciation in aqueous solution is associated to a pK_a of 7.6), and generates a Co(III)−OH moiety ( Co6(III) −OH), as proven by transient absorption spectroscopy; (ii) at pH>pK_a, the Co6(II) −OH→Ru^III(bpy)₃³⁺ ET occurs via bimolecular kinetics, with a rate constant k close to the diffusion limit and dependent on the ionic strength of the medium, consistent with reaction between charged species; (iii) at pH <pK_a, the process involves Co6(II) − OH₂ → Co6(III)−OH transformation and proceeds via a multiple-site, concerted proton electron transfer (CPET) where water assists the transfer of the proton, as proven by the absence of effect of buffer base concentrations on the rate of the ET and by a H/D kinetic isotope in a range of 1.2–1.4. The reactivity of water is ascribed to its organization on the surface of the polyanionic scaffold through hydrogen bond networking involving the Co(II)−OH₂ group.     

A Review on Coordination Properties of Al(III) and Fe(III) toward Natural Antioxidant Molecules: Experimental and Theoretical Insights

This review focuses on the ability of some natural antioxidant molecules (i.e., hydroxycinnamic acids, coumarin-3-carboxylic acid, quercetin, luteolin and curcumin) to form Al(III)- and Fe(III)-complexes with the aim of evaluating the coordination properties from a combined experimental and theoretical point of view. Despite the contributions of previous studies on the chemical properties and biological activity of these metal complexes involving such natural antioxidants, further detailed relationships between the structure and properties are still required. In this context, the investigation on the coordination properties of Al(III) and Fe(III) toward these natural antioxidant molecules might deserve high interest to design water soluble molecule-based metal carriers that can improve the metal’s intake and/or its removal in living organisms.