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Upconverting nanoparticles (UCNPs) were successfully dendronized for fluorescence medical imaging applications. The structural and morphological characterizations of resulting core/shell NaYF 4 :Yb,Tm@dendrons nanoparticles were performed by means of X-ray diffraction, infrared spectroscopy and transmission electron microscopy. In vitro cytotoxicity assays have evidenced their low toxicity. In vivo fluorescence imaging study was performed in mice upon IR excitation, showing promising imaging capacities at low concentrations (0.5 mg/mL) and low power (50 mW/cm 2 ). [ABSTRACT FROM AUTHOR]

Barium titanate nanocrystallites were synthesized by a hydrothermal technique from barium chloride and tetrabutyl titanate. Single-crystalline cubic perovskite BaTiO3 consisting of spherical particles with diameters ranging from 10 to 30 nm was easily achieved by this route. In order to study the influence of the synthesis process on the morphology and the optical properties, barium titanate was also prepared by a solid-state reaction. In this case, only the tetragonal phase which crystallizes above 900°was observed. High-temperature X-ray diffraction measurements were performed to investigate the crystallization temperatures as well as the particle sizes via the Scherrer formula. The lattice vibrations were evidenced by infrared spectroscopy. Eu3+ was used as a structural probe, and the luminescence properties recorded from BaTiO3:Eu3+ and elaborated by a solid-state reaction and hydrothermal process were compared. The reddish emission of the europium is increased by the nanometric particles. [ABSTRACT FROM AUTHOR]

Acetylacetone has been used as a chemical modifier for the synthesis of undoped and Tb3+-doped Y3Al5O12powders. A systematic investigation concerning its influence on the structural and morphological properties of amorphous and crystallized samples has been carried out. These properties have been comparatively studied by means of X-ray diffraction, infrared spectroscopy, SEM, XAS and SAXS. 27Al NMR and EPR experiments have been performed to complete the study. The combined results have evidenced that acetylacetone promotes organic groups departure during calcination, entailing a better structural organization at lower temperatures compared with unmodified powders. Structuration has been proven to occur at short-scale range until a 600 °C heating treatment before being extended by coalescence at higher temperatures. Finally, the presence of acac ligands on the alkoxides leads to a monomer-cluster aggregation process, and thus to a more open network. [ABSTRACT FROM AUTHOR]

Abstract: Sol–gel route has successfully been used to synthesize pure and Eu3+ doped polycrystalline samples of the GdP5O14 pentaphosphates. The as-prepared samples have structurally been characterized using X-ray diffraction. Optical properties in the vacuum ultraviolet (VUV) of Eu3+ activated GdP5O14 samples prepared either by sol–gel process or solid-state reaction were investigated at room temperature for comparison. In this GdP5O14 host matrix the P5O14 ultraphosphate groups were proved to exhibit an efficient absorption in the VUV range. The excitation spectra recorded in the VUV-UV spectral region from 120nm to 350nm have revealed the presence of Gd3+ 4f–5d interconfiguration transitions, Gd3+–O2− and Eu3+–O2− charge transfer states(CTS)in addition to intraconfiguration transitions of Gd3+ ions.Furthermore the Gd3+→Eu3+ energy transfer process was investigated and discussed in the framework of the multiphonon relaxation process. Besides, the GdP5O14:Eu3+ phosphor led to a strong red emission under 147/172nm excitation, so that it can be considered as a promising red phosphor for mercury-free lamps and plasma display panels applications. [Copyright &y& Elsevier]