Charged silsesquioxane used as a vehicle for gold nanoparticles to perform the synthesis of catalyst xerogels

The water soluble charged silsesquioxane that contains the bridged 1,4-diazoniabicyclo[2.2.2]octane chloride group, was used as stabilizing agent and size controller in the synthesis of gold nanoparticles smaller than 15?nm in aqueous medium. The gold nanoparticle dispersion was converted in solid powder form by evaporation. This powder presented organized structure imposed by the presence of charged organic group, similar to organized structure already observed for pure silsesquioxane. The gold nanoparticles in solid powder form presented high storage stability for several months, at ambient conditions, and can be completely redispersed in water again. After redispersion, the optical properties of gold nanoparticles, observed by ultra-violet and visible spectroscopy, and their morphological characteristics, investigated by transmission electron microscopy, are preserved. The gold nanoparticle aqueous dispersion was used as a vehicle of nanoparticles in the synthesis of sol?Cgel silica based hybrid material. This xerogel was characterized by N₂ adsorption?Cdesorption isotherms, showing 260?m²g^?1, and it was applied in a satisfactory way as catalyst for p-nitrophenol reduction to p-aminephenol.     

Quantification of proteins in dairy products using an optical biosensor

Two recent techniques using optical immunosensor technology were developed for the quantification of milk proteins in dairy products. The first application is the simultaneous quantification of the 3 major caseins (alpha(s1), beta, and kappa). This assay consists of a 2-step sandwich strategy, with 2 monoclonal antibodies directed against the N- and C-terminal extremities of each of the caseins, respectively. This strategy permits only intact caseins to be quantified, and not their degradation products. The technique is fast (10 min), sensitive (detection limit about 0.87 microg/mL), and has been applied successfully to raw and drinking milks. In the second application, the severity of the heat treatment sustained by a milk of unknown origin is determined by quantifying separately the native and heat-denatured forms of alpha-lactalbumin with specific monoclonal antibodies. The technique allows discrimination of the different heat treatments studied (pasteurization, direct and indirect ultra-high temperature, sterilization), is fast (4 min), repeatable, fully automated, and requires no pretreatment of the milk sample.     

Synthesis of new Cu(II), Ni(II) and Co(II) complexes with a bis-amide ligand functionalized with pyridine moieties: Spectral, magnetic and electrochemical studies

Three new copper(II), nickel(II) and cobalt (II) dinuclear complexes with a bis-amide ligand derived from tartaric acid have been prepared and characterized. For this purpose, the ligand (R,R)-(+)-di-N,N′-methylpyridino-tartramide (dmpt) was synthesized via the classical aminolysis of (R,R)-(+)-dimethyltartrate with pyridylmethylamine. The molecular structures of the complexes Na[Cu₂(dmptH₋₃)(CO₃)] · 8H₂O (1) and [Ni₂(dmptH₋₂)₂] · 9.75H₂O (2) were elucidated by X-ray diffraction, and the complex [Co₂(dmptH₋₃)(μ-OH)] · NaClO₄ · 5H₂O (3) by XAS. The crystal structure of (1) shows that the two metallic centres are in a square planar environment. Each copper(II) is bound to pyridyl and deprotonated amidic nitrogen atoms and to the oxygen atoms of hydroxyl and carbonato groups. In complex (2), both nickel atoms are in a distorted octahedral environment with an identical set of donors atoms, N₄O₂, coming from four nitrogen atoms of two pyridylmethylamido moieties and two oxygen donor atoms of alcohol groups. XAS analysis of complex (3) allows us to propose a CoN₂O₄ chromophore, with two nitrogen atoms coming from pyridyl and amidic groups and two bridged oxygen atoms from a deprotonated alcohol group and an hydroxyl group; the hexacoordination is achieved by two water molecules. The spectroscopic, electrochemical and magnetic properties of these complexes were investigated.     

Aqueous Chemistry of Zirconium(IV) in Carbonate Media

The interactions between carbonate ions and zirconium oxychloride are studied by potentiometry, dialysis, and ¹³C‐ and ¹⁷O‐NMR spectroscopy in aqueous media. The nature of the soluble carbonatohydroxo complexes depends on the proportions of hydrogencarbonate and carbonate ions in solution before the addition of zirconium oxychloride. Carbonate media lead to polynuclear entities containing no more than two complexed carbonate ions per Zr⁴⁺. The presence of hydrogencarbonate favors the formation of less condensed and more carbonated complexes such as [Zr(CO₃)₄]⁴⁻. The polycondensation degree of the species decreases when the number of carbonates linked per Zr⁴⁺ increases. In all complexes, the carbonate is bidentate, and the metal atoms are linked via hydroxo bridges. The complexation of carbonate with Zr⁴⁺ occurs for a total carbonate concentration higher than 0.1M . Consequently, in natural medium, the speciation of this metal is governed only by the formation of hydroxo complexes.     

Tandem isomerisation-metathesis catalytic processes of linear olefins in ionic liquid biphasic system

trans-3-Hexene is converted to heavier linear olefins by a tandem Ru-catalysed biphasic isomerisation/metathesis sequence. The difference in olefin metathesis and isomerisation rates is modulated by keeping the ionophilic metathesis catalyst in an ionic phase whilst the isomerisation catalyst is in another organic non-polar phase.     

Bioelectroanalytical Determination of Rutin Based on bi‐Enzymatic Sensor Containing Iridium Nanoparticles in Ionic Liquid Phase Supported in Clay

A matrix comprising iridium nanoparticles and 1‐butyl‐3‐methylimidazolium tetrafluoroborate ionic liquid (Ir‐BMI.BF₄) supported in montmorillonite (MMT) was obtained through an efficient incorporation process. This modified clay matrix (Ir‐BMI.BF₄‐MMT) was used for the immobilization of the enzymes laccase (LAC) and polyphenol oxidase (PPO) and employed in the construction of a bi‐enzymatic biosensor for determination of rutin by square‐wave voltammetry. Under optimized conditions, the analytical curve showed a linear range for rutin concentrations from 9.17×10^?8 to 3.10×10^?6 mol L^?1 with a detection limit of 3.09×10^?8 mol L^?1. The method was successfully applied to the determination of rutin content in pharmaceutical samples.     

Self‐Assembly of a Trinuclear Luminescent Europium Complex

Triangular luminescent box : Self‐assembly of a new multidentate receptor with europium cations results in the formation of trinuclear discrete complexes. X‐ray crystallography shows that nine‐coordinate cations are linked by ligands to provide a triangular complex in the solid state and in solution. Despite the coordinated solvent molecules, this topologically unusual complex exhibits remarkable luminescent properties.