Investigation of the thermal degradation of PET, zinc phosphinate, OMPOSS and their blends—Identification of the formed species

The incorporation of both OMPOSS and Exolit OP950 (zinc phosphinate) into PET leads to increased fire retarding properties and a synergistic effect has been established between the three components. Here the thermal degradation of OMPOSS, Exolit OP950, PET and blends of them is investigated via thermal degradation in pyrolytic and thermo-oxidative conditions. All species formed during the degradation of the additives or the blends are identified by solid state NMR and X-ray diffraction in the condensed phase and by GC–MS in the gas phase. The investigation shows that no chemical interaction occurs between the additives, which suggests that the synergy responsible for the improvement of fire properties of the material has a physical origin.     

The influence of numerical diffusion on the solution of the radiative transfer equations

We investigate the explicit numerical solution strategies of multi-dimensional radiative transfer equations which are commonly used, e.g., to determine the radiation emerging from astrophysical objects surrounded by absorbing and scattering matter. For explicit grid solvers, we identify numerical diffusion as a severe source of error in first-order discretization schemes, underestimated in former work about radiative transfer. Using the simple example of a beam propagating through vacuum, we illustrate the influence of the diffusion on the solution and discuss various techniques to reduce it. In view of the large required storage for implicit solvers, we propose to use second-order explicit grid techniques to solve 3D radiative transfer problems.     

Synthesis of a new tricyclic tetraazatriacetic acid as ligand for gadolinium(III)

Polyazapolycarboxylic acids are known to be efficient ligands for the development of gadolinium-based contrast agents used in magnetic resonance imaging (MRI). Given that rigidification of the ligand structure seems to be an important structural parameter to increase the relaxivity of the corresponding gadolinium complex, we have synthesized a new tricyclic tetraazatriacetate ligand from commercially available trans-2-aminocyclohexanol. In the synthetic routes described here, the 2-nitrobenzenesulfonamide chemistry was used to selectively functionalize the polyamine precursors.     

Application of antimonide diode lasers in photoacoustic spectroscopy

First investigations of photoacoustic (PA) spectroscopy (PAS) of methane using an antimonide semiconductor laser are reported. The laser fabrication is made in two steps. The structure is firstly grown by molecular beam epitaxy, then a metallic distributed-feedback (DFB) grating is processed. The laser operates at 2371.6 nm in continuous wave and at room temperature. It demonstrates single-mode emission with typical tuning coefficients of 0.04 nm mA(-1) and 0.2 nm K(-1). PA detection of methane was performed by coupling this laser into a radial PA cell. A detection limit of 20 ppm has been achieved in a preliminary configuration that was not optimised for the laser characteristics.     

Trace gas detection with antimonide-based quantum-well diode lasers

Widely tunable GaInAsSb/AlGaAsSb quantum well (QW) lasers have been grown by molecular beam epitaxy on GaSb substrates. Their emission wavelength, from 2.0 to 2.5 microm, make them suitable for the detection of many gas species in the wavelength range which corresponds to an atmospheric transmission window. Using these devices an experimental setup for open path gas detection has been developed.     

Thermo‐Raman spectroscopy of selected layered double hydroxides of formula Cu6Al2(OH)16CO3 and Zn6Al2(OH)16CO3

Raman spectroscopy using a hot stage was used to characterise layered double hydroxides (LDHs) of the formula (Cu,Zn)₆Al₂(OH)₁₆(CO₃)^·4H₂O. The spectra were used to assess the molecular assembly of the cations in the LDH structure. The sharp band at 1058 cm⁻¹for the Zn₆Al₂(OH)₁₆(CO₃)^·4H₂O is assigned to the ν₁CO₃²⁻ symmetric stretching mode. This band shifts to higher wavenumbers and is observed at 1103 cm⁻¹at 600 °C. It is proposed that metal carbonate species formed during the decomposition of the hydrotalcite structure is responsible for the increase in the band position. The Cu–Al hydrotalcite did not show the same trend. The symmetric stretching mode of carbonate is observed at around 1110 cm⁻¹, and at temperatures above 200 °C a shoulder appears at around 1210 cm⁻¹, suggested to be due to CuCO₃. Copyright © 2008 John Wiley & Sons, Ltd.     

One-Step Photochemical Green Synthesis of Water-Dispersible Ag,Au, and Au@Ag Core–Shell Nanoparticles

A simple and green synthetic protocol for the rapid and effective preparation of Ag, Au and Au@Ag core–shell nanoparticles (NPs) is reported based on the light irradiation of a biocompatible, water-soluble dextran functionalized with benzophenone (BP) in the presence of AgNO₃, HAuCl₄, or both. Photoactivation of the BP moiety produces the highly reducing ketyl radicals through fast (<50 ns) intramolecular H-abstraction from the dextran scaffold, which, in turn, ensures excellent dispersibility of the obtained metal NPs in water. The antibacterial activity of the AgNPs and the photothermal action of the Au@Ag core–shell are also shown.     

DNA-Targeted NO Release Photoregulated by Green Light

A novel molecular hybrid has been designed and synthesized in which acridine orange (AO) is covalently linked to an N-nitrosoaniline derivative through an alkyl spacer. Photoexcitation of the AO antenna with the highly biocompatible green light results in intense fluorescence emission and triggers NO detachment from the N-nitroso appendage via an intramolecular electron transfer. The presence of the AO moiety encourages the binding with DNA through both external and partially intercalative fashions, depending on the DNA:molecular hybrid molar ratio. Importantly, this dual-mode binding interaction with the biopolymer does not preclude the NO photoreleasing performances of the molecular hybrid, permitting NO to be photogenerated nearby DNA with an efficiency similar to that of the free molecule. These properties make the presented compound an intriguing candidate for fundamental and potential applicative research studies where NO delivery in the DNA proximity precisely regulated by harmless green light is required.