1,1,1,1,4,4,4,4‐Octacarbonyl‐2,2,3,3,5,5,6,6‐octamethyl‐cyclo‐2,3,5,6‐tetraantimony‐1,4‐dichromium

The structure of the title compound, alternatively called bis(μ‐tetramethyldistibinediyl)bis(tetracarbonylchromium), [Cr₂Sb₄(CH₃)₈(CO)₈], consists of two Me₄Sb₂ bridging units between Cr(CO)₄ complex fragments. The centre of the molecule is located on a special position of 2/m symmetry. This is the first characterized Sb₄Cr₂ heterocycle.     

Comprehensive two-dimensional gas chromatography of polybrominated diphenyl ethers

Comprehensive two-dimensional gas chromatography with micro electron-capture detection (GCxGC-muECD) was evaluated for the separation of 125 polybrominated diphenyl ethers (PBDEs). From among the six column combinations that were evaluated, DB-1x007-65HT was found to be the most suitable because of: (i) the highest number of BDE congeners separated; (ii) the least decomposition of higher brominated congeners; and (iii) the most suitable maximum operating temperature. The separation of the 125 BDE congeners from five hydroxy- and two methoxy-BDEs and nine other brominated flame retardants (polybrominated biphenyls, tetrabromobisphenol-A, methyl-tetrabromobisphenol-A and hexabromocyclododecane) was also studied. Fluorinated BDEs were found to be valuable internal standards for the determination of BDEs because of their very similar physico-chemical properties and excellent separation from the parent BDEs, mainly in the second dimension. GCxGC-time-of-flight MS and GCxGC-muECD were shown to be useful tools to identify decomposition products of nona- and deca-substituted BDEs, which are formed during the GC run. Three nona-BDEs were shown to be the major decomposition products of BDE 209.     

Necessary and Sufficient Conditions for Viability for Nonlinear Evolution Inclusions

We consider the viability problem for nonlinear evolutions inclusions of the form u′(t)?∈?Au(t)?+?F(u(t)), where A is an m-dissipative (possible nonlinear and multi-valued) operator acting in a Banach space X, K?X is a nonempty, locally closed set and $F:K{\user1{ \rightsquigarrow }}X$ is with nonempty, convex, closed and bounded values. We define the concept of A-quasi-tangent set to K at a given point ξ?∈?K and we prove a necessary condition for C ⁰-viability expressed in terms of this new tangency concept. We next show that, under various natural extra-assumptions, the necessary condition is also sufficient. We extend the results to the quasi-autonomous case, we deal with the existence of noncontinuable or even global C ⁰-solutions and, as applications, we deduce a comparison result and a sufficient condition for null controllability.     

Nucleation and fractal growth of zirconium oxo-alkoxy nanoparticles at the induction stage of sol–gel process

Monodispersed zirconium oxo-alkoxy nanoparticles are synthesized via a sol?Cgel method in a rapid micromixing reactor with in situ particle size measurements. The nucleated nanoparticles of 4.7?nm diameter are free from impurities and conserve high chemical activity. They can be associated in 1D fractals. These nanoparticles can form high optical-quality coatings on hydrophilic substrates.     

Gas chromatography–ion trap tandem mass spectrometry method for the analysis of methoxylated polybrominated diphenyl ethers in fish

Gas chromatography coupled to ion trap tandem mass spectrometry (GC–ITMS-MS) is proposed for the analysis of methoxylated polybrominated diphenyl ethers (MeO-PBDEs) in fish and shellfish. MS–MS operating parameters related to the isolation and fragmentation of the precursor ions were optimized to achieve maximum sensitivity and selectivity. This new method allows the determination of both MeO-PBDEs and PBDEs in a single run. Low limits of detection (0.4–2.5 pg injected) and high precision (RSD < 13%) were achieved. A sample treatment based on a selective pressurized liquid extraction (PLE) using Florisil as fat retainer was applied for the analysis of these compounds in fish samples. Method limits of quantification ranged from 0.11 to 0.95 ng g⁻¹ lipid weight for MeO-PBDEs and between 0.18 and 0.50 ng g⁻¹ lipid weight for PBDEs. In addition, good repeatability of the whole method was achieved (RSD < 15%). The suitability of the method was evaluated by analyzing a certified reference material (SRM 1945, whale blubber) with satisfactory results. The developed method was applied to the simultaneous analysis of MeO-PBDEs and PBDEs in fish and shellfish samples from the Mediterranean Sea.     

Temperature effect over structure and photochemical properties of nanostructured SnO<Subscript>2</Subscript> powders

We successfully synthesized tin dioxide nanoparticles with polyhedral morphology via an ethylene glycol assisted sol-gel approach. The structural characteristics of three tin dioxide samples were investigated after being thermally treated at 400°C, 600°C and 800°C. X-ray diffraction (XRD) patterns clearly show the formation of single phase tin dioxide nanoparticles, with crystallite size of 6–20 nm, in good correlation with Fourier transform infrared (FTIR) spectra. Transmission electron microscopy (TEM) analysis confirms the formation of 6nm polyhedral nanoparticles for the 400°C sample. Ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectra suggest a high concentration of oxygen vacancies. The oxygen vacancy concentration increases with temperature, due to the combined action of the formation of V_O and the energetic O compensation. X-ray photoelectron spectroscopy (XPS) analysis also confirms the formation of single phase tin dioxide and the presence of oxygen vacancies in good agreement with UV-VIS and PL data.

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Synthesis and characterization of ZnO nanostructures obtained in mixtures of ionic liquids with organic solvents

ZnO nanoparticles were synthesized in mixtures of ionic liquids based on imidazolium cation with organic solvents (dimethyl sulfoxide and ethylene glycol) by a simple, one-step solution route at low temperature. The effect of these mixtures on the morphology, size and properties of as obtained ZnO nanopowders was investigated. The obtained nanopowders have been characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), UV-Vis absorption spectroscopy (UV-Vis) and photoluminescence (PL). The effect of the ionic liquid mixture on the photocatalytic degradation of methylene blue has been analysed. The XRD studies confirmed the hexagonal wurtzite structure of the obtained ZnO powder. The UV-Vis absorption spectra present the typical shape for ZnO, with a broad band situated in the UV region, with the maximum around 360 nm. The calculated band-gap energy is in interval 3.25–3.28 eV. The synthesized ZnO nanopowders have high photocatalytic activity against methylene blue, the best results being obtained when 1-ethyl-3-methylimidazolium tetrafluoroborate was used as the solvent.

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Matrix-dependent cooperativity in spin crossover Fe(pyrazine)Pt(CN)4 nanoparticles

Anisotropic nanoparticles of the Fe(pyrazine)Pt(CN)(4) network were prepared embedded in various matrices that revealed to have a dramatic effect on the cooperative spin crossover phenomena. By a judicious choice of the nature of the matrix and the control of interparticle distances, a hysteresis of 15 K was achieved close to room temperature for such nano-objects.