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International audience; Over the last decade, upconversion nanoparticles (UCNP) have been widely investigated in nanomedicine due to their high potential as imaging agents in the near-infrared (NIR) optical window of biological tissues. Here, we successfully develop active targeted UCNP as potential probes for dual NIR-NIR fluorescence and radioactive-guided surgery of prostate-specific membrane antigen (PSMA)(+) prostate cancers. We designed a one-pot thermolysis synthesis method to obtain oleic acid-coated spherical NaYF4:Yb,Tm@NaYF4 core/shell UCNP with narrow particle size distribution (30.0 ± 0.1 nm, as estimated by SAXS analysis) and efficient upconversion luminescence. Polyethylene glycol (PEG) ligands bearing different anchoring groups (phosphate, bis- and tetra-phosphonate-based) were synthesized and used to hydrophilize the UCNP. DLS studies led to the selection of a tetra-phosphonate PEG(2000) ligand affording water-dispersible UCNP with sustained colloidal stability in several aqueous media. PSMA-targeting ligands (i.e., glutamate-urea-lysine derivatives called KuEs) and fluorescent or radiolabelled prosthetic group were grafted onto the UCNP surface by strain-promoted azide-alkyne cycloaddition (SPAAC). These UCNP, coated with 10 or 100% surface density of KuE ligands, did not induce cytotoxicity over 24 h incubation in LNCaP-Luc or PC3-Luc prostate cancer cell lines or in human fibroblasts for any of the concentrations evaluated. Competitive binding assays and flow cytometry demonstrated the excellent affinity of UCNP@KuE for PSMA-positive LNCaP-Luc cells compared with non-targeted UCNP@CO2H. Furthermore, the binding of UCNP@KuE to prostate tumour cells was positively correlated with the surface density of PSMA-targeting ligands and maintained after 125I-radiolabelling. Finally, a preliminary biodistribution study in LNCaP-Luc-bearing mice demonstrated the radiochemical stability of non-targeted [125I]UCNP paving the way for future in vivo assessments.

International audience; Improving phosphor photoluminescence efficiency is a key parameter to boost the performances of many optical devices. In this work, colloidal silver nanocubes, homogeneously spread on a luminescent surface, have proved to help both injecting and extracting light in and out of the photoluminescent layer and hence contributed significantly to the enhancement of the fluorescence. This approach has been applied to two materials: the well-known Y3Al5O12:Ce yellow phosphor and an optical quartz. The emission efficiency, for sol–gel derived YAG:Ce layers, has increased 80% in the presence of an optimal nanoparticle density, whereas for quartz, a weakly fluorescent material, the photoluminescence signal can be enhanced by a 200-fold factor. A physical analysis based on simulations shows that the disorder is an important factor and that the surface density of Ag nanoparticles is a crucial parameter.

International audience; The optical properties of sulforhodamine B (SRB) hosted in surfactant-modified layered double hydroxide (LDH) are explored using quantum yield efficiencies and temporal variations in luminescence. The effect of the spacer, known to provide a suitable SRB dilution in the solid state, is studied in-depth with respect to its relative content and its alkyl chain length. Counter-intuitively, considering the nature of such a “passive” spacer, the study reports the effect on the luminescence of the optically active molecules for a large series of surfactants. Spacer intercalation enables the distance between adjacent LDH sheets to be adjusted to the size of the luminescent molecule guest, as exemplified here using a series of surfactant molecules: (CH3)(CH2)nSO4Na with odd values 7 ≤ n ≤ 17 and a fixed amount of SRB at 0.05% of the total anion content in the surfactant and SRB. The effect of the surfactant on the optical properties of SRB is investigated, and the best performance is obtained for n = 11, corresponding to the powder LDH–DS/SRB-5. A computational approach evaluating the packing and structural arrangement present in the series of interleaved surfactants helps to interpret the effect of the length of the alkyl chain on the distribution of the SRB within the LDH interlayer. Silicon composite films were elaborated with different LDH loadings, and the composite film with a loading of 40 wt% of LDH–DS/SRB-5 exhibited the maximum absolute photo-luminescence quantum yield (PL QYabs), as high as 60.0 ± 3.0%, being recorded at 570 nm. Furthermore, an in-depth study of fluorescence lifetimes enables us to highlight a rarely-observed phenomenon of delayed fluorescence, and to distinguish for the first time between the location of SRB, either on or inside the LDH platelets.

International audience; A series of LixNa1-xY(PO3)4: 10% Eu3+ samples (x = 0; 0.25; 0.5; 0.75; 1) were synthesized by a solid state reaction method. They were characterized at room temperature using X-ray diffraction and luminescence spectroscopy. The obtained powders crystallize in monoclinic systems with space groups C2/c and P21/n respectively for x = 1 and x = 0. However, according to XRD data, the LixNa1-x(PO3)4: Eu3+ material seems to be a mixture of the Li and Na homologues when x = 0.5. This situation has been considered as an option to broaden the VUV absorption instead of mixing of both Li and Na based compositions which has been considered as representative of the discrimination between the two extremes. The VUV excitation and emission spectra of as-synthesized compounds were measured. The broad bands near 200 nm in VUV excitation spectra are attributed to both contribution of overlapped O2− -Y3+ and O2− -Eu3+ absorption charge transfer states while the host absorption band is estimated at 150 nm. The emission spectra are dominated by three bands characteristics of the radiative de-excitation connecting the first excited state 5D0 of Eu3+ to the main 7F1, 7F2 and 7F4 manifolds of the ground state. Based on Judd–Ofelt (J–O) theory, the intensity parameters (Ω2 and Ω4) have been evaluated from the emission spectra.

Single crystal of CdF2 codoped with the couple Ho3+/Yb3+ with good optical quality were grown by a Bridgman technique after purification of the starting materials. Emission spectra are recorded at room temperature under UV and NIR excitation. The kinetics of the green and red emissions arising from both (5F4, 5S2) and 5F5 excited states of Ho3+ ions are analyzed in the frame of Ho3+→Ho3+ and Yb3+↔Ho3+ energy transfers. The luminescence decays are parametrized using Inokuti-Hirayama model considering dipole-dipole interaction, in the case of UV excitation and also NIR excitation for the green emission, leading to a R0 critical transfer distance of 9–11 A. The kinetics of the 5F5→5I8 red upconverted emission is analyzed and discussed using a rate equation model.

The incorporation of Ce3+ ions in silicate glasses is a crucial issue for luminescence-based sensing applications. In this article, we report on silica glass preforms doped with cerium ions fabricated by modified chemical vapor deposition (MCVD) under different atmospheres in order to favor the Ce3+ oxidation state. Structural analysis and photophysical investigations are performed on the obtained glass rods. The preform fabricated under reducing atmosphere presents the highest photoluminescence (PL) quantum yield (QY). This preform drawn into a 125 µm-optical fiber, with a Ce-doped core diameter of about 40 µm, is characterized to confirm the presence of Ce3+ ions inside this optical fiber core. The fiber is then tested in an all-fibered X-ray dosimeter configuration. We demonstrate that this fiber allows the remote monitoring of the X-ray dose rate (flux) through a radioluminescence (RL) signal generated around 460 nm. The response dependence of RL versus dose rate exhibits a linear behavior over five decades, at least from 330 µGy(SiO2)/s up to 22.6 Gy(SiO2)/s. These results attest the potentialities of the MCVD-made Ce-doped material, obtained under reducing atmosphere, for real-time remote ionizing radiation dosimetry.

International audience; The structural, morphological and optical properties of pure and Ca-doped zinc sulfide (ZnS:Ca) nanoparticles (NPs) prepared by hydrothermal method at different percentages of Ca are reported herein. The resulting NPs were characterized by X-ray diffraction analysis (XRD), Raman scattering, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. The XRD patterns confirmed the crystalline nature of all pure and doped NPs showing a single phase cubic blende structure, whereas the SEM micrographs showed sphere-shaped NPs. The sizes of the as-prepared NPs estimated by TEM were found to be in the range 44–147 nm. The PL emission spectra of ZnS:Ca nanocrystals excited at 400 nm consist of a broad band (420 nm–640 nm) characterized by two main contributions peaking at 484 and 533 nm. The overall maximum emission intensity is found for ZnS:3% Ca with internal quantum yield of 8.4%.

International audience; Cubic α-NaYF4 nanometer-sized crystals doped with Eu3+, Tb3+, Yb3+-Eu3+ or Yb3+-Tb3+ were synthesized by an original coprecipitation route. The obtained nanoparticles exhibited primary particles showing cubic shape with sizes ranging between 35 and 65 nm. The singly- or co-doped nanophosphors exhibited strong red (Eu3+) or green (Tb3+) fluorescence upon ultraviolet (UV) or near infrared (NIR) excitation, which resulted respectively from down- or up-conversion processes occurring in their structure. Spectroscopic properties were investigated on the basis of emission spectra as well as luminescence decays. From the emission spectra of Eu3+ doped samples, the Ω2 and Ω4 Judd-Ofelt intensity parameters were calculated. The concentration quenching of the Eu3+ or Tb3+ ion emissions in singly-doped or Yb3+ co-doped α-NaYF4 were ascribed to resonant cross-relaxations. The main derived interaction between the active ions was evidenced as an electric dipole-dipole one through fitting the decays curves with the Inokuti-Hirayama model. The critical distances and energy transfer microparameters for the transfer processes were given showing very short range interaction. The dependence of integral up-conversion intensity on the NIR energy of the beam power was measured. The results indicated a two-photon process based on a cooperative energy transfer.

International audience; Pure hexagonal β-NaGdF 4 and Eu 3+ or Pr 3+-doped β-NaGdF 4 nanocrystals in shape of nanorods of ∼140 nm of length have been synthesized using a simple and rapid coprecipitation method. XRD analysis evidenced pure single phases exhibiting characteristic luminescence of Eu 3+ or Pr 3+ ions when excited under UV or blue radiations. Samples gave rise to intense orange-red emission and quite white emission in the case of respectively Eu 3+ or Pr 3+ doped samples. Optical properties are discussed in the frame of Judd-Ofelt theory and considering that an energy transfer occurs between active ions. Notably it was found that the quantum-cutting by a two-step energy transfer from Gd 3+ to Eu 3+ can improve the red emission of Eu 3+ ions under near-VUV excitation. Such quantum-cutting mechanism has been also considered in the case of Pr 3+ doped β-NaGdF 4. However, the efficiency of both processes in comparison with literature suggest that only one part of the energy in the excited states within Gd 3+ can be transferred to Eu 3+ for its red emission. In the case of Pr 3+ ions, the energy is more probably released through the self-trapped exciton emission certainly due to the lack of resonant VUV excitation.

The facile synthesis of functionalized luminescent nanoparticles from LnL3 lanthanide complexes is described. The luminescence properties of the lanthanide chelates and of the corresponding nanohybrids are reported and compared. For a further application in bioimaging, the cytotoxicity of the nano-objects was investigated.

Ce-doped sol-gel silica glasses were prepared for real-time X-ray dose or dose rate monitoring using radioluminescence ( RL ) and optically stimulated luminescence (OSL). A small piece of this glass scintillator was connected to two optical fibers, allowing a remote measurement of the ionizing radiation dose through RL and OSL signals. By using this Ce-doped material, we particularly demonstrated that the RL signal shows a linear behavior at least up to dose rates of 1.2 Gy/s. Furthermore, the linear dose response of the OSL signal can be extended up to 500 Gy, independently of the used dose rate.

Two series of phosphate glasses belonging to the (65-x) P2O5–35CaO–xRE2O3 system (RE = Eu or Tb; 0 ≤ x ≤ 6 mol%) were prepared by the melt-quenching technique. All compositions were successfully drawn as continuous monofilaments fibers. The effect of Eu3+ and Tb3+ ions concentration on their mechanical, structural, and photoluminescence properties was investigated. The results revealed that the highest tensile strength was 1031 ± 34 MPa for fibers doped with 6 mol% of Eu2O3 and 1014 ± 65 MPa for fibers doped with 6 mol% of Tb2O3. The addition of RE2O3 showed an increase in density and Tg. A structural investigation was carried out using FTIR spectroscopy. The photoluminescence properties in terms of excitation and emission spectra were investigated in detail. The most intense emission band at 611 nm corresponds to the 5D0 → 7F2 transition of Eu3+ ions under 392 nm excitation was observed for fibers doped with 6 mol% of Eu2O3. The most intense emission band at 543 nm corresponds to the 5D4 → 7F5 transition of Tb3+ ions under 374 nm excitation was observed for fibers doped with 6 mol% of Tb2O3. These two compositions exhibited the highest absolute quantum yield, reaching 20.25% and 4.81%, respectively.

International audience; Light extraction is a key parameter to improve the performances of optical devices. Nanopatterned Y3Al5O12:Tb3+ luminescent coatings usable in such devices have been elaborated and have shown enhanced emission efficiency compared to their unpatterned counterparts. These nanostructured films were obtained by using the colloidal lithography combined with the Langmuir-Blodgett technique. It is the first time to our knowledge that this patterning technique is directly applied on YAG matrix. Resulting nanostructuring is a hexagonal network capable of modifying the light travelling path within the substrate. Conventional and angular-resolved photoluminescence were investigated on both unpatterned and patterned samples. Due to the nanostructuring, the extraction efficiency is improved by 26% and 131% depending on the crystallinity of the sample. Noticeably, nanostructuring is found to have an influence on the angular distribution of photoluminescence whose intensity has been evaluated to its maximum normal to the film surface.

International audience; Nano-sized Eu 3+-doped GdBO 3 vaterite type nanophosphors have been synthesized successfully via acetylacetone assisted aqueous sol-gel route. Systematic investigation of the influence of Eu 3+ ion content and pH value of the suspension of precursors on structural, morphological and luminescence spectroscopic properties has been performed. X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, field emission-scanning electron microscopy (FE-SEM), Thermogravimetric and differential thermal gravimetry (TG/DTA), room temperature steady and time resolved photoluminescence (PL) spectroscopy techniques were employed to characterize the obtained powder samples. It has been found that the Eu 3+ ion content and pH value precursors suspension have important effect on the structural, morphology and emission properties. The XRD analysis reveals that GdBO 3 : 10% mol Eu 3+ synthesized at pH = 2 and pH = 10 exhibit the quasipurest P6 3 /mmc vaterite structure. The vibrational absorption of (BO 3) 3group is assigned to the GdBO 3 with calcite type or other vaterite structure namely triclinic and monoclinic. The morphologies of GdBO 3 particles size increases with increasing of pH value. All sample present only the orange-red colors emission from 5 D 0 levels to the 7 F J levels (J = 0-3) of Eu 3+ ion. Furthermore, it was found that 10% concentration of Eu 3+ presents the quenching of emission in GdBO 3. Also, it was that the emission intensity was affected by the pH value and sample with pH = 10 exhibits the highest emission intensity. The asymmetry ratio parameter R between red and orange emission intensities in function of Eu 3+ content and pH value is determinate and discussed.

The luminescence of Fluorescein, an inexpensive dye, ought to be interesting for lighting application devices such as commercial LEDs. However, the molecule suffers from severe instability, making it inappropriate for such applications. As previously studied, fluorescein molecules may be hosted in a layered double hydroxide (LDH), and the role of such an inorganic material in stabilizing the dye has been underlined. However, a deep understanding of the resulting optical properties is still required. Using extremely small amounts of fluorescein, it is demonstrated here that Zn2Al cation-based LDH tethering acts as a «solid solvent » for the dye, enabling its luminescence even in powder form, whereas fluorescein molecules on their own emit no luminescence at all in the solid state. However, aggregations of the dye occur in the interlamellar space, leading to non-radiative emission. Emission and excitation spectra, as well as fluorescence decays, are studied to explain the difference between the hybrid LDH-Fluorescein material and an aqueous solution of fluorescein. Additionally, LDH platelets are found to help the dispersion of the intercalated fluorescein in silicone to obtain a homogeneous composite film, which exhibits luminescent properties. Finally, an accelerated photoaging study demonstrates that the LDH-fluorescein filler has a pro-degradant effect on polymer aging under UV radiation.

1) Background: Nanomedicine has recently emerged as a promising field, particularly for cancer theranostics. In this context, nanoparticles designed for imaging and therapeutic applications are of interest. We, therefore, studied the encapsulation of upconverting nanoparticles in mesoporous organosilica nanoparticles. Indeed, mesoporous organosilica nanoparticles have been shown to be very efficient for drug delivery, and upconverting nanoparticles are interesting for near-infrared and X-ray computed tomography imaging, depending on the matrix used. (2) Methods: Two different upconverting-based nanoparticles were synthesized with Yb3+-Er3+ as the upconverting system and NaYF4 or BaLuF5 as the matrix. The encapsulation of these nanoparticles was studied through the sol-gel procedure with bis(triethoxysilyl)ethylene and bis(triethoxysilyl)ethane in the presence of CTAB. (3) Results: with bis(triethoxysilyl)ethylene, BaLuF5: Yb3+-Er3+, nanoparticles were not encapsulated, but anchored on the surface of the obtained mesoporous nanorods BaLuF5: Yb3+-Er3+@Ethylene. With bis(triethoxysilyl)ethane, BaLuF5: Yb3+-Er3+ and NaYF4: Yb3+-Er3+nanoparticles were encapsulated in the mesoporous cubic structure leading to BaLuF5: Yb3+-Er3+@Ethane and NaYF4: Yb3+-Er3+@Ethane, respectively. (4) Conclusions: upconversion nanoparticles were located on the surface of mesoporous nanorods obtained by hydrolysis polycondensation of bis(triethoxysilyl)ethylene, whereas encapsulation occurred with bis(triethoxysilyl)ethane. The later nanoparticles NaYF4: Yb3+-Er3+@Ethane or BaLuF5: Yb3+-Er3+@Ethane were promising for applications with cancer cell imaging or X-ray-computed tomography respectively., This research was funded by ANR NanoptPDT. SR thanks the Erasmus Mundus program for a grant. This work has been supported by the Spanish Ministry of Science, Innovation and Universities (RTI2018-094426-B-I00).

Made available in DSpace on 2019-10-06T17:11:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-08-26 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) 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 Ω2 (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. Chemistry Institute of São Paulo State University – UNESP, Araraquara Université Clermont Auvergne CNRS SIGMA Clermont Institut de Chimie de Clermont-Ferrand Chemistry Institute of São Paulo State University – UNESP, Araraquara CNPq: 142495/2013-1 CNPq: 168263/2017-0 CNPq: 203031/2015-6 CNPq: 401679/2013-6

International audience; NaPO3-ZnF2 binary fluorophosphate glasses doped with trivalent erbium and monovalent copper were synthesized by the conventional melting and casting method using ErF3 and CuCl as starting materials. The samples were systematically investigated using X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis. X-ray powder diffraction patterns confirmed that the as-prepared compounds were all amorphous. The glass transition temperature (Tg) was observed around 230 °C by DSC analysis, while the thermal stability range (ΔT) was estimated to be between 90 and 140 °C. The measured value of the refractive index (n) was measured as 1.502 at a wavelength of 632.8 nm. Thermal annealing of the samples was performed at different temperatures above Tg for various heat-treatment times. During these steps, monovalent copper and sodium ions were expected to be reduced, forming metallic nanoparticles. This transformation lead to coloration changes, depending on the annealing time and temperature, with respect to the transparency of the glasses. These spectroscopic changes are related to the plasmonic effects induced by the presence of both Cu and Na metallic nanoparticles, which promote red shift due to absorption. The VIS-NIR absorption spectra of the prepared glasses were investigated in the frame work of standard Judd-Ofelt (J-O) theory, which was used to determine the J-O intensity parameters, radiative transition probabilities and branching ratios for Er3+ ions embedded in the glasses. The calculated intensity parameters () were compared to those obtained for Er3+ in several other glasses.

Stoichiometric phosphors Li (x) Na (1−x) Sm(PO 3 ) 4 (x = 0, 0.5, 1) were prepared in the solid state and were characterized at room temperature using X-ray diffraction, infrared and Raman spectroscopy. The obtained LiSm(PO 3 ) 4 and NaSm(PO 3 ) 4 polycrystalline samples are single-phased and have centrosymmetric monoclinic structure. The observed results show the presence of characteristic bands due to (PO2) − terminal and P−O−P bridging groups. However, the Li 0.5 Na 0.5 Sm(PO 3 ) 4 material seems to be a mixture of the Li and Na homologues. The VUV excitation and emission spectra of as-synthesized compounds were measured. It was found that the Sm 3+ ions show an orange-red emission which corresponds to the group transitions 4 G 5/2 → 6 H J (J = 5/2, 7/2, 9/2, 11/2), with the strongest transition ( 4 G 5/2 → 6 H 7/2) peaking at around 597 nm. The decay curves were pure exponential. The derived time constants are comprise between 14 μs and 31 μs, the lowest value is for NaSm(PO 3 ) 4 . The decays were modeled in the frame of fast diffusion model with a rough estimation of fast cross-relaxation mechanism which returns a cross-relaxation rate of 3–7 × 10 4 s −1 and diffusion constant of 1–2 × 10 −9 cm 2 s −1 .

International audience; Upconverting nanoparticles (UCNPs) were successfully dendronized for fluorescence medical imaging applications. The structural and morphological characterizations of resulting core/shell NaYF4: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/cm2).

International audience; In this work, we report the effects of Li doping concentration (5, 10 and 15 at.%) on structural, morphological, electrical and optical properties of Li doped ZnO films. We used X-ray diffraction (XRD), scanning electronic microscopy (SEM), Hall-Effect measurements, UV–Vis–NIR and photoluminescence (PL) spectroscopies. XRD patterns showed that the deposited films had a hexagonal-wurtzite crystal structure with preferred orientation along the c-axis. SEM micrographs indicated that grain dispersion in the films were homogeneous. Hall-effect measurements revealed that ZnO thin films doped with 5, 10 and 15 at.% of Li have p-type conduction. The UV–Vis–NIR spectroscopy analyses demonstrated that all thin films were highly transparent in the visible region and the optical transmittance was dependent on the Li doping content. Room temperature PL spectra put into evidence that all Li-doped ZnO thin films emitted a UV-blue light and the emission intensities were found to be affected by Li concentration.

We report the first synthesis of highly homogenous Ce-doped YAG/ZnO core/shell nanoparticles (YAG:Ce/ZnO CSN) based on the hydrolysis/condensation of Zn(OAc)2 on the surface of YAG:Ce nanoparticles (NPs). Results show that YAG:Ce NPs of about 100 nm diameter are homogenously surrounded by a multilayer of highly crystallized ZnO nanocrystals (ZnO NCs) of 10–15 nm diameter with a core/shell structure. The as-prepared nanostructures have been used in the photocatalytic degradation of sulfathiazole (STZ), which is a molecule widely used as antibiotic, under UV-vis and visible light. The effect of YAG:Ce/ZnO weight ratio and YAG:Ce particle size on the photocatalytic efficiency of YAG:Ce/ZnO core/shell structures has been studied. The YAG:Ce/ZnO weight ratio of 1/1 was found to yield the optimal photocatalytic activity. Results also showed that YAG:Ce/ZnO CSN with 100 nm core size exhibited much higher photocatalytic activity compared to YAG:Ce/ZnO CSN with micro-sized YAG;Ce core. The recyclability of YAG:Ce/ZnO CSN photocatalyst was also demonstrated over at least 10 photocatalytic degradation cycles.

International audience; A new luminescent composite film resulting from the dispersion of luminescent organic dyes in a single-layered hydroxide (SLH)-type inorganic matrix has been developed. Two fluorescent organic dyes emitting visible light upon blue LED excitation were investigated in this study: dicyanomethylene (DCM) and pyranine (HPTS). These dyes exhibit broad emission bands that cover a large part of the visible spectrum. The concept developed in our work consisted in keeping SLH in its wet form to ensure a good dispersion of the fluorescent dyes prior to immobilizing the hybrid materials in a silicone polymer to achieve luminescent composite films. We demonstrate that these coatings stacked upon each other and placed above a blue LED lead to white-light emission with suitable photometric parameters for applications in lighting or display devices: colour temperature of 5409 K and colour rendering index (CRI) of 81.

International audience; Luminescent materials become one of interesting issues for white LED-based lighting devices (WLEDs) due to their high performances for converting the monochromatic light from UV/blue LED chips into white light. Nevertheless, the availability of rare earth materials, the low color rendering index (CRI) and too-cold color temperature of the white LEDs remain some drawbacks to penetrate into the general LED lighting markets. Herein, we report the development of rare-earth-free luminescent nanocomposites combined with a UV/blue LED chip in order to provide white light. Gradient alloyed cadmium selenide/zinc sulfide (CdSe)x(ZnS)1–x and copper indium sulfide/zinc sulfide (CuInS2)x(ZnS)1–x quantum dots have been used to achieve the luminescent nanocomposite films in silicone as polymer matrix. The optical performances were investigated upon LED excitation. The photometric parameters of systems consisting of luminescent nanocomposites and LEDs including color rendering index (CRI), correlated color temperature (CCT), Commission Internationale de l’Eclairage (CIE) chromaticity coordinates, and luminous efficacy can be tuned by controlling the compositions and thickness of nanocomposite films. Furthermore, the thermal stability and the reliability of these luminescent nanocomposite films were investigated.

International audience; Undoped and Au-doped ZnO thin films were prepared on glass substrates by sol-gel process and dip-coating technique. The effects of Au concentration (10–30 at%) on structural, morphological and optical properties of the ZnO films were studied using X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), UV–Vis–NIR spectrometry, Hall-effect measurements and photoluminescence (PL) spectroscopy. XRD results show that all films crystallized in a hexagonal wurtzite structure and are highly c-axis oriented. The crystal quality of the films is found to decrease with the increase in Au doping. A weak diffraction peak related to Au cubic phase is also observed at Au concentration higher than 10 at%. The Raman studies confirmed that the film's crystallinity degraded with increasing Au content. FE-SEM micrographs and AFM images show that both morphology and surface roughness are affected by the Au doping concentration. UV–Vis–NIR optical spectra reveal that increasing Au doping into ZnO films enhances their transparency. Photoluminescence measurements at room temperature put into evidence the presence of two intense bands at 373.6 and 385 nm in the UV spectra and four very weak emission bands in the visible spectral range. All the visible emissions are found to increase with Au content. The emission at 373.6 is maximal for the film doped at 20 at%, whereas the one at 385 nm reaches its maximum intensity in the film doped at 10 at%.

Invité; International audience

International audience; The crystal structure of the new triphosphate K2Na3P3O10: 5% Eu3+ (monoclinic, space group C2/c, unit cell parameters: a = 9.8695(3) Å; b = 5.6171(2) Å; c = 18.6404(6) Å; β = 96.0947(2) °) has been solved from single crystal data. The structure is closely related to that of the undoped material K2Na3P3O10 and indicates the presence of rare earth ions in all alkaline crystallographic sites. Eu3+ doped K2Na3P3O10 triphosphates were synthesized as polycrystalline samples by solid state reaction and characterized by powder X-ray diffraction and infrared spectroscopy. The optical properties were recorded in the VUV-visible range. Broad and intense bands are observed in the 150–250 nm range, corresponding to the absorption by the host matrix and Eu-O charge transfer state (CTS). The numbering of the Eu3+5D0 → 7FJ (J = 0–4) emission transitions observed in the visible domain is in good agreement with the crystal structure data and is discussed according to the symmetry of the different sites occupied by the lanthanide ions in the triphosphate lattice.

International audience; Nominally undoped and Eu3+ or Eu3+–Dy3+ doped SrAl2O4 powders are prepared using source chemicals of standard grade (99–99.99%) by solid state and sol–gel procedures, in order to vary the proportions of monoclinic (P21) and hexagonal (P63 and P6322) polymorphs in the compounds. Electron spin resonance reveals systematic contamination of the compounds by transition metal ions. The emission properties of the materials are investigated at 77 K upon UV and blue excitations. The optical features are ascribed, for the essential, to Mn4+ ions. The spectroscopy of this ion in conjunction with X-ray diffraction data and theoretical considerations is used to individuate P6322, P63 and P21 phases in the doped and undoped SrAl2O4 powders.

International audience; Several phosphors without rare-earth elements were synthesized by a simple and practical method. Depending on their wavelength emitting range upon UV excitation, i.e. blue, green or red, they were classified in three groups. The phosphors exhibiting the best performances in optical properties were selected to be incorporated in free-standing silicon films and combined with a 365 nm LED. The thermal quenching of phosphors as well as the photometric parameters of the luminescent composite films were investigated. This white emission of the combination between the rare-earth-free phosphors based silicon film and LED shows a CRI >75 and CCT around 4000 K which can fulfil the requirements for indoor domestic lighting source.

International audience; Orthoborate nanopowder phosphor, with formulation Gd0.90Eu0.1BO3 has been synthesized by aqueous sol-gel method, and then annealed at 1000, 1100 and 1200 °C. The crystal structure and the morphology of the as prepared materials were cheeked using several techniques such as: IR, XRD, and SEM. The experimental results show that the synthesized nanoparticles have a primary average diameter of approximately 150–250 nm. The samples crystallize mainly in the vaterite structure. Despite that the signature of triangular borate group BO33- more characteristics of the calcite form is observed in the FTIR spectra indicating that some Eu3+ ions are embedded in parasitic phase such as calcite form. The VUV excitation spectra of the samples were recorded at room temperature and lead to selectivity for the VUV excited emission confirming that the overall emission come from the Eu3+ ions embedded in at least two crystallographic structures. However, the contribution from Eu3+ ions embedded in parasitic phase contribute weakly to the overall emission. The luminescence properties of the prepared phosphors were characterized also by its kinetic decay. The results show that luminescence decaying correlated the observations made for both excitation and emission spectra.

International audience; In this work, ZnO NPs were successfully synthesized by the sol–gel method without any organic additives or post annealing. The effect of the preparation process on the structural and optical properties of the resulting NPs was investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. The structural characterization demonstrated clearly that the NPs crystallize in pure ZnO würtzite structure without any other secondary phases. Furthermore, we show that it is possible to perform the control of the crystalline growth orientation of ZnO NPs, which is a key parameter when seeking to develop ZnO NPs with piezoelectric properties for nano-transducer applications. In fact, TEM observations show that the reduction of the NaOH flow changes the NPs shape from hexagonal NPS to short nanorods grown along the c-axis. The PL spectra of the obtained NPs excited at 280 nm, present an UV emission centered at approximately 380 nm with a slight shift when varying the synthesis temperature and/or the NaOH flow. Moreover, as the visible region (from 400 to 650 nm) is concerned, it was shown that the increasing of the synthesis temperature affects strongly the kind of interstitial defects (Oi, Zni and VoZni) formed in ZnO nanostructures. However, the excitation at 320 nm revealed a broad deep-level emission for all the samples that can be deconvoluted into two Gaussian peaks centered at 514 nm (P1) and 581 nm (P2). These last results have been discussed in the light of a physical mechanism based on the Schottky barrier.

International audience; This paper addresses the formulae-related enhancement of the GdxY1-xPO4:Tb3+ nanopowders when submitted to (VUV) vacuum ultraviolet. Structural characterizations of GdxY1-xPO4:Tb3+ nanocrystals were conducted by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). In particular, for the first time, in this work, the photoluminescence upon VUV excitation of GdxY1-xPO4:Tb3+ powders synthesized by the solvothermal method, is reported, and the optical study reveals that the photoluminescent properties of nanophosphors are strongly dependent on their crystalline structures, as well as on gadolinium-yttrium composition. The highest emission intensity upon 160 nm radiation was observed for the Gd0.5Y0.5PO4:Tb3+ powders which exhibited a two-fold increase in luminescence intensity comparing with YPO4:Tb3+.

Three photoluminescent complexes containing either ZnII or CdII have been synthesized and their structures determined. Bis[4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole-κ2 N 1,N 5]bis(dicyanamido-κN 1)zinc(II), [Zn(C12H10N6)2(C2N3)2], (I), bis[4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole-κ2 N 1,N 5]bis(dicyanamido-κN 1)cadmium(II), [Cd(C12H10N6)2(C2N3)2], (II), and bis[4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole-κ2 N 1,N 5]bis(tricyanomethanido-κN 1)cadmium(II), [Cd(C12H10N6)2(C4N3)2], (III), all crystallize in the space group P\overline{1}, with the metal centres lying on centres of inversion, but neither analogues (I) and (II) nor CdII complexes (II) and (III) are isomorphous. A combination of N—H...N and C—H...N hydrogen bonds and π–π stacking interactions generates three-dimensional framework structures in (I) and (II), and a sheet structure in (III). The photoluminescence spectra of (I)–(III) indicate that the energies of the π–π* transitions in the coordinated triazole ligand are modified by minor changes of the ligand geometry associated with coordination to the metal centres.

Several complexes and silica-based nanohybrids of rare-earth ions (Eu3+, Gd3+) have been synthesized from dimethyl 4-azidopyridine-2,6-dicarboxylate (4) following the Click chemistry approach. A complete spectroscopic study indicates that such compounds exhibit strong sensitization by the antenna effect from both UV and NIR excitations. The Gd3+-based materials show phosphorescence under ambient conditions, which originates from the lowest-energy intra-ligand triplets. Fine analysis of the NIR excitation spectra using time resolved photoluminescence spectroscopy (TRS) indicates that the spectral repartition of the triplet T1 state differs notably between the complexes and the NPs embedding the complexes. Moreover the dependence of Eu3+ luminescence vs. incident beam power in the NIR region diverges from pure quadratic dependence expected in the framework of the two-photon absorption process. The results are discussed considering the occurrence of a direct singlet-to-triplet optical absorption transition (S0[RIGHTWARDS ARROW]T1) upon NIR excitation.

International audience; 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 120 nm to 350 nm 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 147/172 nm excitation, so that it can be considered as a promising red phosphor for mercury-free lamps and plasma display panels applications.

This work aims at achieving homogeneous luminescent films from Ce-doped yttrium aluminium garnet (YAG:Ce) phosphors dispersed in aqueous suspensions. Colloidal luminescent suspensions of YAG:Ce nanoparticles have been successfully prepared by a solvothermal process. Powder resulting from the dried as-synthesized suspension was submitted to different thermal treatments and a thorough study of nanoparticles aqueous suspensions has been carried out, for each thermal treatment. The influence of these treatments on the structural, morphological and optical properties of YAG:Ce nanopowders were studied by means of X-ray diffraction, infrared spectroscopy and transmission electron microscopy. Besides, particles size distribution and zeta potential of YAG:Ce aqueous suspensions in different pH conditions were investigated by dynamic light and electrophoretic light scatterings, respectively, in order to characterize suspensions stability. This study enabled us to optimize heat treatment and redispersion parameters in order to achieve very homogeneous luminescent films which can be used for display or mood lighting.

International audience; In this work we report on the sol–gel deposition of Na doped ZnO thin films on quartz substrates. The effects of Na doping concentrations (0, 3, 6 and 9 at.%) on structural, morphological, electrical and optical properties of the synthesized films were systematically investigated by X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), Hall-effect measurements, UV–Vis–NIR spectrophotometry and photoluminescence (PL) spectroscopy. XRD patterns showed that the prepared films were highly c-axis oriented exhibiting hexagonal wurtzite structure of ZnO. Raman spectra of All the ZnO films exhibited similar scattering peaks corresponding to the Raman active modes of ZnO wurtzite hexagonal structure. AFM images indicated that grain size and surface roughness of the films were affected by Na doping. From the Hall-effect measurements, it was found that carrier type is dependent on Na content. The UV–Vis–NIR spectroscopy analyses revealed that all the films were highly transparent in the visible region. Room temperature PL spectra demonstrated that UV emission of the Na-doped ZnO thin films depends on the Na concentration. In particular, the undoped sample shows the highest emission intensity, while the p-type Na doped ZnO film at 3 at.% exhibits the lowest one.

International audience; This work describes the preparation of red luminescent composites based on an ethylene/vinyl acetate (EVA) copolymer filled with a Y3BO6:Eu3+ phosphor powder. Luminescent powders were synthesized using a method derived from the Pechini synthesis method. The powders were then homogeneously dispersed in an EVA copolymer solution to achieve luminescent composite films. The structural, morphological and optical properties of the red luminescent composite films were investigated. The dispersion of phosphor particles in an EVA copolymer did not globally modify their optical features. However, the presence of an Eu3+–O2− charge transfer excitation band was observed and attributed to the effect of the refractive index of the EVA copolymer. Finally, the optical studies of these films evidenced their compatibility with commercial ultra-violet light emitting diodes (LEDs).

International audience; Red, green, and blue emissions through up conversion and energy transfer processes were investigated in triply doped YP5O14: Yb3+, Er3+, Tm3+ ultraphosphates upon excitation at 980 nm as a function of the Yb3+, Er3+ and Tm3+ concentrations. Highly crystalline tri-doped samples showing a monoclinic form with C2/c space group symmetry were synthesized by a flux method leading to the elaboration of single crystals which were crushed for physical-chemical mainly by X-ray powder diffraction and optical up conversion characterization.The blue, green and red emissions intensity can be adjusted by the Yb3+, Er3+ and Tm3+ amounts. The Er3+ red and green up conversion emissions were examined in the case of the Yb3+/Er3+ co-doped YP5O14 materials. Two- and three-photons processes are observed for the red and green emissions of Er3+ respectively. Three visible red, green and blue up conversion emissions corresponding to Er3+4F9/2→4I15/2 (red), Tm3+1G4→3F4; 3F2,3→3H6 (red), Er3+2H11/2, 4S3/2 →4I15/2 (green) and Tm3+1G4 → 3H6 (blue) emission bands were simultaneously observed in triply doped YP5O14: Yb3+, Er3+, Tm3+ ultraphosphates due to Yb–Er and Yb–Tm up conversion mechanisms. Moreover, a three-photon process is observed for the red emission in the tri-doped materials instead of a 2-photons mechanism observed for samples without Tm, due to a Er3+→ Tm3+ energy transfer involving the Er3+4F9/2 and the Tm3+3F2,3 states.Despite the presence of large phonons energy due to the phosphate material, around 1200 cm−1, Er3+ and Tm3+ visible emissions due to up conversion phenomena can be subsequently combined in order to obtain a white light and find new applications in display devices.

International audience; Blue-emitting BaMgAl 10 O 17 :Eu 2þ (BAM:Eu), suitable for applications in a next generation of Hg-free lamps based on UV LEDs, was prepared by a microwave induced solution combustion synthesis, using urea as combustion fuel and nitrates as oxidizers. Purity control of the as-synthesized blue phosphor was undertaken by a washing step followed by a reduction one. Structural and morphological properties of the outcoming phosphors have been considered. Synthesis process allows producing a well-crystallized and nanostructured BAM phase within only few minutes. The influence of reduction treatment on the relative amounts of Eu 2þ /Eu 3þ in our samples has been investigated through an original study by magnetization and M€ ossbauer spectroscopy. Furthermore, a complete optical study has been carried out and allowed us to determine the europium localization in the three possible sites in BAM matrix. The percentage of Eu 2þ increased twofold after the reduction treatment, entailing an increase in the lumi-nescence efficiency upon UV excitation. Finally, temperature-dependent luminescence of combustion-derived powders has been studied till 170 C and compared to that of commercial BAM:Eu. MISCS-derived phosphors present a higher thermal stability than commercial one: whereas the emission efficiency of this last was reduced by 64%, the one of combustion-derived BAM:Eu experienced an only 12% decline. Furthermore, while commercial BAM suffered from a severe blue-shift with increasing temperature , our phosphors keep its color quality with a good stability of the photometric parameters.

The luminescence properties of YPO4 phosphors activated with 2% Sm3+ and variable concentrations of Bi3+ (from 0 to 5%) have been investigated. Steady state emission and decay time measurements clearly evidence an increment of the emission performance as the Bi3+ content increases up to 2.5%. Quantum yield measurements provide quantitative confirmation of the experimental observations. This behavior has been associated to the effect of the Bi3+ ions on the optical properties of the host lattice.

Three 2-phenyl-naphth[2,3-d]oxazole derivatives, one of them being unsubstituted (1) and the two others bearing a methyl (2) and a tert-butyl group (3) in the para position of the phenyl ring, were prepared. In the crystalline state, all compounds adopted a crossed-stacking mode that favors fluorescence emission. They emitted in the blue region and their photoluminescence quantum yield ranged between 25 and 59 %. The preparation of micro/nanoparticles by simple methods was optimized. By using a solvent-exchange method, the compounds readily gave microcrystals, the size and shape of which closely depend on the nature of the substituent, as well as nanocrystals that measured around 200 nm. The proportion of micro- and nanocrystals was modulated by the experimental conditions and the two populations could be separated by filtration for subsequent use. For unsubstituted compound 1, drop-casting from a solution in tetrahydrofuran spontaneously generated an array of parallel and almost perpendicularly oriented nanofibers that exhibited efficient waveguiding properties. Owing to their robustness, good solid-state optical properties, and to the simplicity of particle preparation, these naphthoxazole derivatives appear as promising candidates for the fabrication of blue-emitting tracers and nanofibers.