Electron Transfer in the Cs⊂{Mn4Fe4} Cubic Switch: A Soluble Molecular Model of the MnFe Prussian-Blue Analogues

A mixed-valence {Mn^II₃Mn^IIIFe^II₂Fe^III₂} cyanide-bridged molecular cube hosting a caesium cation, Cs⊂{Mn₄Fe₄}, was synthesized and structurally characterized by X-ray diffraction. Cyclic-voltammetry measurements show that its electronic state can be switched between five different redox states, which results in a remarkable electrochromic effect. Magnetic measurements on fresh samples point to the occurrence of a spin-state change near room temperature, which could be ascribed to a metal-to-metal electron transfer converting the {Fe^II−CN−Mn^III} pair into a {Fe^III−CN−Mn^II} pair. This feature was only previously observed in the polymeric MnFe Prussian-blue analogues (PBAs). Moreover, this novel switchable molecule proved to be soluble and stable in organic solvents, paving the way for its integration into advanced materials.     

Properties of cerium-zirconium mixed oxides partially substituted by neodymium: Comparison with Zr-Ce-Pr-O ternary oxides

CeO₂ doped with praseodymium, neodymium and/or zirconium atoms were prepared by coprecipitation and by the sol-gel method. Structural properties were investigated by in situ XRD and Raman spectroscopy while oxygen storage capacity (OSC) was measured by transient CO oxidation. All the compounds, except pure Nd₂O₃, have a fluorite-type structure as well as a Raman band at 560 cm⁻¹ characteristic of the oxygen vacancies involving non-stoichiometric oxides. The lattice parameter under hydrogen, being dependent on the temperature, revealed two reduction mechanisms: one at a low temperature at the surface and another at a high temperature in the bulk. Ce-Nd binary oxides show a strong tendency towards crystallite aggregation, which reduces accessibility to gases and OSC properties. Zirconium improves the thermal resistance to sintering of both Ce-Nd and Ce-Pr oxides. The Zr-Ce-Pr-O followed by Zr-Ce-Nd-O compounds displaying high oxygen mobility at a low temperature, appear to be very promising for practical applications such as OSC materials.     

Ultra-performance liquid chromatography-tandem mass spectrometry: a novel challenge in multiresidue pesticide analysis in food

Potential of ultra-performance liquid chromatography (UPLC) separation strategy coupled with tandem (in space) mass spectrometric detection (MS/MS) in multiresidue pesticide analysis was critically assessed. Performance parameters such as number of theoretical plates, height of theoretical plate, peak symmetry and peak capacity were measured/calculated on the basis of data generated by analysis of apple extracts containing 17 (semi)polar pesticides representing various classes of active ingredients of widely used crop protective preparations. Ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) procedure provided improved chromatographic parameters resulting in significantly increased sample throughput including lower solvent consumption and lower limits of quantitation (LOQs) for most of target analytes compared to common method employing conventional high-performance liquid chromatography (HPLC) separation.     

Structure and mechanical properties of poly(l-lactide)/layered silicate nanocomposites

Poly(ε-caprolactone) (PCL) masterbatches with the intercalated and the exfoliated morphology were prepared by ring opening polymerization of ε-caprolactone in the presence of organomodified montmorillonite (MMT) Cloisite 30B. Poly(l-lactide) (PLLA) nanocomposites with Cloisite 30B or PCL masterbatches were prepared by melt blending. The effects of the silicate type, MMT content and the nanocomposite morphology on thermal and mechanical properties of PLLA nanocomposites were examined. The montmorillonite particles in PLLA/Cloisite 30B and PLLA/intercalated masterbatch nanocomposites were intercalated. In contrary to expectations, the exfoliated silicate layers of exfoliated masterbatch were not transferred into the PLLA matrix. Due to a low miscibility of PCL and PLLA, MMT remained in the phase-separated masterbatch domains. The stress-strain characteristics of PLLA nanocomposites, Young modulus E, yield stress σ_y and yield strain ε_y, decreased with increasing MMT concentration, which is associated with the increase in PCL content. The expected stiffening effect of MMT was low due to a low aspect ratio of its particles and was obscured by both plastifying effects of PCL and low PLLA crystallinity. Interestingly, in contrast to the neat PLLA, ductility was enhanced in all PLLA/Cloisite 30B materials and in PLLA/masterbatch nanocomposites with low MMT concentrations.     

Synthesis of functionalized analogs of pyochelin, a siderophore of Pseudomonas aeruginosa and Burkholderia cepacia

Using an improved synthesis of pyochelin, a siderophore common to several pathogenic Pseudomonas species, three functionalized pyochelin analogs were efficiently synthesized starting from appropriate 2-hydroxybenzonitriles.     

Radioisotope x-ray fluorescence analysis of ancient pottery from Tel Kouzama site in Damascus, Syria

The radioisotope X-ray fluorescence method has been utilized in the analysis of thirty nine archaeological pottery fragment samples from Tel Kouzama site, Damascus city, Syria. The samples were irradiated by a 109Cd radioisotope source (-9 10(8) Bq) for 1000 s. 17 chemical elements were determined. These elemental concentrations have been processed using two multivariate statistical methods, cluster and factor analysis in order to determine similarities and correlation between the various samples. Factor analysis confirms that samples were correctly classified by cluster analysis. These two methods suggest that samples can be considered to be manufactured using four different sources of raw material.     

Lipid diffusion in giant unilamellar vesicles is more than 2 times faster than in supported phospholipid bilayers under identical conditions

The lateral diffusion coefficients of a BODIPY tail-labeled lipid in two model systems, namely, free-standing giant unilamellar vesicles (GUVs) and supported phospholipid bilayers (SPBs), were determined by fluorescence correlation spectroscopy (FCS) using the Z-scan approach. For the first time, the performed measurements on 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) bilayers maintain exactly the same experimental conditions for both systems, which allows for a quantitative comparison of lipid diffusion in these two commonly used model membranes. The results obtained revealed that the lipid mobility in free-standing bilayers (D=7.8+/-0.8 microm2 s-1) is significantly higher than in the bilayer created on the solid support (mica) (D=3.1+/-0.3 microm2 s-1).     

Studies on the molecular interaction of Erythrosine ‘B’ with surfactants

The spectroscopic investigation on anionic dye, Erythrosine ‘B’(EB) with three different types of surfactants such as CTAB (cationic), sodium lauryl sulphate (SLS; anionic) and Triton X-100 (TX-100),Tween-20, 40, 60 and 80 (nonionic) in aqueous media shows that EB forms a 1:1 molecular complex with TX-100, Tweens and CTAB. No interaction is observed between EB and SLS. The thermodynamic and spectrophotometric properties of these complexes suggest that EB forms a strong charge transfer (CT) complex with TX-100 and Tweens whereas the interaction of EB with CTAB is coulombic in nature. Photogalvanic and photoconductometric studies also support the above interactions. In addition to this, the electron-donating ability among the nonionic surfactants, i.e. TX-100 and Tweens towards dye, role of surface in CT interaction, the site of CT interaction and the intensity and stability of CT interaction between EB and nonionic surfactants have been pointed out.     

HPLC analysis of a syrup containing nimesulide and its hydrolytic degradation product

The present paper deals with the evaluation of nimesulide, 2-phenoxy-4-nitroaniline, the main hydrolytic degradation product of nimesulide, of methylparaben and propylparaben, and eventually of 4-hydroxybenzoic acid by HPLC with UV detection at 254 nm in syrup as a pharmaceutical formulation. HPLC analysis was employed on the reversed phase C18 with methanol and 0.01 M dibasic ammonium phosphate (ρ _r = 60: 40, pH 4.0). Validation was performed using standards and a pharmaceutical preparation containing the compounds described above.     

TPR investigations on the reducibility of Cu supported on Al2O3, zeolite Y and SAPO-5

Reducibility of Cu supported on Al₂O₃, zeolite Y and silicoaluminophosphate SAPO-5 has been investigated in dependence on the Cu content using a method combining conventional temperature programmed reduction (TPR) by hydrogen with reoxidation in N₂O followed by a second the so-called surface-TPR (s-TPR). The method enables discrimination and a quantitative estimation of the Cu oxidation states +2, +1 and 0. The quantitative results show that the initial oxidation state of Cu after calcination in air at 400 °C, independent on the nature of the support, is predominantly +2. Cu²⁺ supported on Al₂O₃ is quantitatively reduced by hydrogen to metallic Cu⁰. Comparing the TPR of the samples calcined in air and that of samples additionally pre-treated in argon reveals that in zeolite Y and SAPO-5 Cu²⁺ cations are stabilized as weakly and strongly forms. In both systems, strongly stabilized Cu²⁺ ions are not auto-reduced by pre-treatment in argon at 650 °C, but are reduced in hydrogen to form Cu⁺. The weakly stabilized Cu²⁺ ions, in contrast, may be auto-reduced by pre-treatment in argon at 650 °C forming Cu⁺ but are reduced in hydrogen to metallic Cu⁰.