Ferrite magnetic nanoparticles (MNPs) were functionalized with a variety of silanes bearing different functional endgroups to render them stable with respect to aggregation and keep them well-dispersed in aqueous media. The MNPs were prepared by the thermal decomposition method, widely used for the synthesis of monodisperse nanoparticles with controllable size. This method makes use of a hydrophobic surfactant to passivate the surface, which results in nanoparticles that are solely dispersible in nonpolar solvents. For use in biological applications, these nanoparticles need to be made water-dispersible. Therefore, a new procedure was developed on the basis of the exchange of the hydrophobic surface ligands with silanes bearing different endgroups to decorate ferrite magnetic nanoparticles with diverse functionalities. By this means, we could easily determine the influence of the endgroup on the nanoparticle stability and water-dispersibility. Amino-, carboxylic acid-and poly(ethylene glycol)-terminated silanes were found to render the MNPs highly stable and water-dispersible because of electrostatic and/or steric repulsion. The silane molecules were also found to form a protective layer against mild acid and alkaline environments. The ligand exchange on the nanoparticle surface was thoroughly characterized using SQUID, TEM, XPS, DLS, TGA, FTIR, UV-vis, and zeta potential measurements. The presented approach provides a generic strategy to functionalize magnetic ferrite nanoparticles and to form stable dispersions in aqueous media, which facilitates the use of these magnetic nanoparticles in biological applications.

Poly(lactic acid) is at present the most promising and commercially available bio‐based and biocompostable (bio)plastic. The properties of PLA, however, are rather poor, notably its low glass transition temperature Tg of ∼55 °C, its intrinsic low crystallization rate and the limited barrier properties with respect to water, oxygen and carbon dioxide in comparison with to oil‐based counterparts, notably polyesters (PET). In this manuscript we address the question of what could ultimately be achieved in terms of barrier properties when PLA is crystallized fully. In fact, this question is rather academic in view of the long crystallization/annealing times needed to obtain maximum crystallinity but serves the purpose of better understanding current limits and notably a better understanding of the role of crystallinity on the barrier properties. A correlation is made between crystallization, various morphological parameters and the barrier properties of PLA. Crystallization of PLA causes a decrease of the oxygen permeability, but not in linear proportion with the decrease in amorphous volume. We explain this in terms of influence of the space filling and the inner crystalline structure on gas transport properties. Furthermore we suggest that the presence of a rigid amorphous fraction with lower density can have strong impact on PLA gas permeability, in particular on the gas solubility coefficient of PLA. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2247–2258, 2009

A homogeneous distribution of luminescent lanthanide(III) 2-thenoyltrifluoroacetonate complexes (Ln ) Pr, Nd, Sm, Eu, Dy, Ho, Er, Tm, Yb) in an organic-inorganic hybrid material was obtained by grafting the complexes to the solid matrix via 2-substituted imidazo[4,5-f]-1,10-phenanthroline moieties. Thin films of the silica hybrid material were prepared by the sol-gel method and by spin-coating of the gelating solution on glass slides or on oxidized silicon wafers. The thickness of the thin films was determined by scanning electron microscopy (SEM). High-resolution luminescence spectra of the lanthanide complexes were recorded, and the luminescence decay times were measured. The luminescence quantum yields of europium(III)-doped thin films exposed to different drying conditions were determined by using an integrating sphere.

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