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In this paper, we evaluate the role played by the polyether type and chain length on the complexation of Eu3+ by the urea group of siloxane-polyether organic-inorganic hybrid materials based on polyethylene oxide (U-PEO, mw = 1900 g mol−1) and polypropylene oxide (U-PPO, mw = 230, 2000, and 4000 g mol−1). Investigation was made of the effect of the photooxidation of the PEO and PPO chains, induced by artificially accelerated ultraviolet aging (λ ≥ 300 nm), with the decomplexation of Eu3+ from the urea-polyether array. Fourier transform infrared (FTIR) and photoluminescence (PL) spectra evidenced loss of the ligand-to-metal charge transfer (LMCT) when the Eu3+ cations were unable to disrupt the strong hydrogen-bonded urea/urea aggregates formed using shorter U-PPO chains (230 g mol−1) or semicrystalline U-PEO (1900 g mol−1). FTIR analysis showed that formate was the main photoproduct formed continuously during the artificial ultraviolet aging of U-PEO (1900 g mol−1) and U-PPO (2000 g mol−1), with concomitant decreases of Eu3+ complexed to urea bridges, spatially correlated siloxane nodes, and the Judd-Ofelt parameter Ω 2 (R). The kinetics of all these parameters were described by exponential laws with comparable time constants, evidencing the sensitivity of the Eu3+ photoluminescence to the elimination/formation of the hydrogen-bonded urea-polyether array during the photooxidation of PPO chains. In the case of U-PEO:Eu3+, different time constant values were observed, indicating the existence of a faster process governed by the facilitated transport of the oxidative species through the amorphous moieties of the semicrystalline U-PEO. This sensitivity of structural and PL properties arising from the photoinduced degradation of ureasil-polyether films can be exploited in the fabrication of new transparent, flexible, and biocompatible UV dosimeters and sensors. Organic-Inorganic Hybrid (OIH) materials photoluminescence properties of lanthanide dopants combined with structural modifications induced by artificial ultraviolet aging. Image 1 • Main photoproduct from ultraviolet aging of ureasil-polyether is formate. • Structural features and PL properties are sensitive to photoinduced degradation. • Properties can be useful to produce transparent, flexible and biocompatible UV sensors. [ABSTRACT FROM AUTHOR]

In the biotechnology field, nanoparticles with a strong magnetic moment can bring attractive and novel potentialities. They are detectable, manipulable, stimulable by a magnetic field and they could be applied as nano-tracers for medical imaging and nano-vectors for transporting therapeutic agents to a target. For our part, we applied Fe3O4 nanoparticles to immobilize bacteria of Moroccan strains in order to develop bacterial bioreactor. For this aim, we got through the synthesis and characterization of magnetite Fe3O4 nanoparticles by co-precipitation in basic medium. The obtained nanoparticles were encapsulated in silica by sol-gel process. The results of this step allowed us to use Fe3O4@SiO2 nanoparticles to immobilize Bacillus licheniformis by adsorption and separate it magnetically. The principle of this system gives us the opportunity to develop a bacterial bioreactor for industrial applications. [ABSTRACT FROM AUTHOR]

In the present study, we report a new process for modifying cellulosic fabrics by using ionic liquids. To this aim, 1-methylimidazolium chloride propyltriethoxysilane and 1-pyridinium chloride propyltriethoxysilane salts were synthesised. Then, the cotton fabrics were treated with sols containing these salts by the pad-dry-cure process. Finally, the treated fabrics were impregnated in a diluted solution of HPF to perform the metathesis reaction. The morphology and chemical composition of treated and untreated fabrics were analysed by scanning electron microscopy, elemental analysis and infrared spectroscopy. The droplet shape analysis confirmed that the water repellency of the fabrics was significant after surface modification. The flame retardancy was also enhanced by using the PF anion. Thermogravimetric analysis was used to assess the thermal stability of these treated fabrics in air. [ABSTRACT FROM AUTHOR]

Transparent BaTiO3:Eu3+ films were prepared via a sol-gel method and dip-coating technique, using barium acetate, titanium butoxide, and polyvinylpyrrolidone (PVP) as modifier viscosity. BaTiO3:Eu3+ films ~500 nm thick, crystallized after thermal treatment at 700 °C. The powders revealed spherical and rod shape morphology. The optical quality of films showed a predominant band at 615 nm under 250 nm excitation. A preliminary luminescent test provided the properties of the Eu3+ doped BaTiO3. [ABSTRACT FROM AUTHOR]

Abstract: Sol–gel synthesis of isostructural LiGdF4:Eu3+ and LiYF4:Er3+ crystallized powders is reported. Furthermore, LiGdF4:Eu3+ coatings were also prepared by dip- and spin-coating methods. In all cases, X-rays diffraction measurements were performed to check materials crystalline purity while infrared spectroscopy analyses showed that the organic groups are removed after annealing treatments at 550°C in F2 atmosphere. This result was emphasized by long radiative decay time of Er3+ ions in LiYF4 (τ =10.5ms) attributed to the absence of both organic residues and hydroxide ions. Laser induced emission spectra of LiGdF4:Eu3+ were recorded upon excitation in both 5D2 and 6P5/2 high lying levels of respectively Eu3+ and Gd3+ ions. Eventually fluorescence decays of rare earth ions were measured and compared in both cases. [Copyright &y& Elsevier]

Abstract: Sol–gel route has been successfully used to obtain pure LiYF4:Eu3+ powders for the first time to our best knowledge. Fluorine ions were introduced through trifluoroacetic acid as reacting agent which is decomposed under heating treatment and as a result leads to the formation of fluorides. Sintering under F2 reactive atmosphere was performed to prevent any oxidation and insure residual hydroxide elimination. The materials structure was analyzed by means of X-ray diffraction (XRD) while infrared spectroscopy (IR) was carried out to examine the presence of residual organic groups. Laser induced luminescence spectra as well as fluorescence decays of Eu3+ ions were recorded and compared to those of LiYF4:Eu3+ prepared by conventional solid state reaction. In both cases, the results are undoubtedly typical of Eu3+ emitting center embedded in a unique site of D2d symmetry. Nevertheless, the sol–gel derived samples exhibit 5D0 luminescence decays characterized by longer rise times upon 5D2 excitation as well as a larger 5D1/5D0 branching ratio at room temperature or 100K. [Copyright &y& Elsevier]

Sol–gel route has been successfully used to obtain pure Y3Al5O12 and Y3Al5O12:Eu3+ powders. The formation process, the structure as well as the microstructure of the materials were analyzed by means of X-ray diffraction (XRD), thermal analysis (TG–TDA), infrared spectroscopy (IR) and scanning electron microscopy (SEM). It has been shown that sol–gel derived YAG powders crystallize around 900 °C whereas a temperature much higher is necessary to obtain this compound by solid state synthesis (≈1500 °C). Laser induced luminescence spectra, as well as luminescence decays of Eu3+ ions show undoubtedly the spectral features of a Eu3+ emitting center embedded in a unique site of D2 symmetry. [Copyright &y& Elsevier]

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]