Ce:LYSO, from scintillator to solid-state lighting as a blue luminescent concentrator.

Cerium-doped lutetium-yttrium oxyorthosilicate (Ce:LYSO) is a well-known single crystal scintillator used in medical imaging and security scanners. Recent development of high power UV LED, matching its absorption band, questions the possibility to use Ce:LYSO in a new way: as LED-pumped solid-state light source. Since Ce:LYSO is available in large size crystals, we investigate its potential as a luminescent concentrator. This paper reports an extensive study of the performance in close relation to the spectroscopic properties of this crystal. It gives the reasons why the Ce:LYSO crystal tested in this study is less efficient than Ce:YAG for luminescent concentration: limited quantum efficiency and high losses coming from self-absorption and from excited-state absorption are playing key roles. However, we demonstrate that a Ce:LYSO luminescent concentrator is an innovative source for solid-state lighting. Pumped by a peak power of 3400 W in quasi-continuous wave regime (40 µs, 10 Hz), a rectangular (1 × 22 × 105 mm3) Ce:LYSO crystal delivers a broadband spectrum (60 nm FWHM) centered at 430 nm. At full output aperture (20 × 1 mm2), it emits a peak power of 116 W. On a squared output surface (1 × 1 mm2) it emits 16 W corresponding to a brightness of 509 W cm-2 sr-1. This combination of spectrum power and brightness is higher than blue LEDs and opens perspectives for Ce:LYSO in the field of illumination namely for imaging.

Synthesis and in vitro preliminary evaluation of prostate-specific membrane antigen targeted upconversion nanoparticles as a first step towards radio/fluorescence-guided surgery of prostate cancer.

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 groups 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.

Investigation of the Incorporation of Cerium Ions in MCVD-Silica Glass Preforms for Remote Optical Fiber Radiation Dosimetry.

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.

Encapsulation of Upconversion Nanoparticles in Periodic Mesoporous Organosilicas.

(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.

Towards rare-earth-free white light-emitting diode devices based on the combination of dicyanomethylene and pyranine as organic dyes supported on zinc single-layered hydroxide.

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.

Coupling Photoluminescence and Ionic Conduction Properties Using the Different Coordination Sites of Ureasil-Polyether Hybrid Materials.

In this article, we demonstrate that each functional group of ureasil organic-inorganic hybrid (OIH) materials can act as a specific coordination site for a given active guest species, hence allowing the possibility of combining different functional properties. To illustrate this concept, the sol-gel process was used to produce diurea cross-linked siloxane-polyethylene oxide (U-PEO) and siloxane-polypropylene oxide (U-PPO) hybrid host frameworks with similar molecular weights (1900 and 2000 g mol-1 for PEO and PPO, respectively), with Li+ and Eu3+ as active guest ions providing ionic conduction and photoluminescence (PL) properties, respectively. Comparison of Fourier transform infrared spectra and small-angle X-ray scattering results for single-doped (using Li+ or Eu3+) and co-doped (using Li+ and Eu3+) U-PEO and U-PPO hosts showed that in every case, there was specific coordination of Eu3+ by the carbonyl group of the urea bridge and of Li+ by ether-type oxygen of the PEO and PPO chains. Optical analyses demonstrated that loading with Li+ did not affect the luminescence properties of the Eu3+-loaded OIH. Although loading with Eu3+ had a small effect on ionic transport, co-doping with Li+ ions ensured macroscopic ion-conduction of the transparent and luminescent hybrid material. The results suggested that the combination of both properties in a transparent elastomeric material could be useful for the development of multifunctional devices. The results suggested that the combination of both properties in a transparent elastomeric material could be useful for the development of multifunctional polyelectrolytes applied in the field of dual luminescent devices such as photoelectrochromic smart windows.

Three zinc(II) and cadmium(II) complexes containing 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole and polynitrile ligands: synthesis, molecular and supramolecular structures, and photoluminescence properties.

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-κ2N1,N5]bis(dicyanamido-κN1)zinc(II), [Zn(C12H10N6)2(C2N3)2], (I), bis[4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole-κ2N1,N5]bis(dicyanamido-κN1)cadmium(II), [Cd(C12H10N6)2(C2N3)2], (II), and bis[4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole-κ2N1,N5]bis(tricyanomethanido-κN1)cadmium(II), [Cd(C12H10N6)2(C4N3)2], (III), all crystallize in the space group P-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.

Preparation of core/shell NaYF4:Yb,Tm@dendrons nanoparticles with enhanced upconversion luminescence for in vivo imaging.

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 (0.5mg/mL) and low power (50mW/cm2).

Ce-doped YAG nanophosphor and red emitting CuInS2/ZnS core/shell quantum dots for warm white light-emitting diode with high color rendering index.

In this work, we report the solvothermal synthesis of Ce-doped YAG (YAG:Ce) nanoparticles (NPs) and their association with a free-Cd CuInS2/ZnS (CIS/ZnS) core/shell QDs for application into white light emitting diode (WLED). 1500 °C-annealed YAG:Ce NPs and CIS/ZnS core/shell QDs exhibited intense yellow and red emissions band with maxima at 545 and 667 nm, respectively. Both YAG:Ce nanophosphor and CIS/ZnS QDs showed high photoluminescence quantum yield (PL QY) of about 50% upon 460 nm excitation. YAG:Ce nanophosphor layer and bilayered YAG:Ce nanophosphor-CIS/ZnS QDs were applied on blue InGaN chip as converter wavelength to achieve WLED. While YAG:Ce nanophosphor converter layer showed low color rendering index (CRI) and cold white light, bilayered YAG:Ce nanophosphor-CIS/ZnS QDs displayed higher CRI of about 84 and warm white light with a correlated color temperature (CCT) of 2784 K. WLED characteristics were measured as a function of forward current from 20 to 1200 mA. The white light stability of bilayered nanophosphor-QDs-based WLED operated at 200 mA was also studied as a function of operating time up to 40 h. Interestingly, CRI and CCT of such device tend to remain constant after 7 h of operating time suggesting that layer-by-layer structure of YAG:Ce phosphor and red-emitting CIS/ZnS QDs could be a good solution to achieve stable warm WLED, especially when high current density is applied.

Investigation on combustion derived BaMgAl10O17:Eu2+ phosphor powder and its corresponding PVP/BaMgAl10O17:Eu2+ nanocomposite.

This work focuses on the study of BaMgAl10O17:Eu(2+) (BAM:Eu) nanophosphors prepared by a microwave-assisted combustion procedure and more especially on the polymer/BAM:Eu nanocomposite film suitable for optical devices such as solid-state-lighting. Powder presented a specific nanomorphology, highly friable and thus easily ground into fine particles. They were then homogeneously dispersed into a polymer solution (poly(N-vinylpyrrolidone) or PVP) to elaborate a polymer phosphor nanocomposite. The structural, morphological and optical features of the nanocomposite film have been studied and compared to those of a pristine PVP film and BAM:Eu powder. All the characterizations (XRD, SEM, SAXS, etc.) proved that the blue phosphor nanoparticles are well incorporated into the polymer nanocomposite film which exhibited the characteristic blue emission of Eu(2+) under UV light excitation. Furthermore, the photostability of the polymer/phosphor nanocomposite film has been studied after exposure to accelerated artificial photoageing at wavelengths above 300 nm.

Monodisperse silica nanoparticles doped with dipicolinic acid-based luminescent lanthanide(iii) complexes for bio-labelling.

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.

Luminescent nanocomposites made of finely dispersed Y3Ga5O12:Tb powder in a polymer matrix: promising candidates for optical devices.

This paper reports the initial results of an original and simple method to elaborate flexible, self-standing, and thick luminescent films suitable for optical devices. PVP/Y(3)Ga(5)O(12):Tb(3+) nanocomposite films have been successfully achieved from a sol-gel derived Y(3)Ga(5)O(12):Tb(3+) powder and an alcoholic solution of poly-N-vinylpyrrolidone (PVP). The structural, morphological, and optical properties of these nanocomposite films have been studied and compared to those of a pristine PVP film and Y(3)Ga(5)O(12):Tb(3+) powder. The nanocomposite films were characterized by infrared and Raman spectroscopies as well as scanning and transmission electron microscopies (SEM and TEM) and demonstrated good dispersion of the phosphor particles within the polymer matrix via an alveolar mesostructure. The optical properties of these nanocomposites were fully characterized, and both their excitation and emission spectra and decay curves were recorded. Furthermore, photostability of the nanocomposite films and of the luminescent raw powder has been studied after exposure to an accelerated artificial photoageing at wavelengths higher than 300 nm. The elaboration process used is both tunable and applicable to a large variety of powders and polymers because it does not require any additive to form homogeneous and easily shapeable phosphor/polymer nanocomposites applicable in a large variety of optical devices such as solid-state-lighting.

Modifications involved by acetylacetone in properties of sol-gel derived Y(3)Al(5)O(12):Tb(3+)- II: optical features.

Tb(3+)-doped Y(3)Al(5)O(12) powders have been synthesized from alkoxide precursors using, or not using, acetylacetone as a chemical modifier. The terbium oxidation state and local environment of amorphous and crystallized powders have been comparatively investigated by means of X-ray absorption near-edge structures (XANES) and extended X-ray absorption fine structure (EXAFS) while laser-induced luminescence was used to study their optical properties. Excitation and emission spectra have been recorded and a relative luminescence yield has been assessed upon 277 nm excitation. Whatever the sample, the terbium oxidation state remains +III and, for a similar heating treatment until 900 degrees C, its local environment appears to be better organized in powders modified by acetylacetone. Structural parameters obtained during XAS study are consistent with the YAG structure in which Tb atoms are in solid solution with Y ones. Besides, Tb(3+) characteristic green luminescence has been recorded for all samples, even those amorphous. It has been evidenced that the use of acetylacetone leads to more efficient luminescent materials for calcination temperatures ranging from 400 degrees C to 900 degrees C upon 277 nm excitation. Discrepancies between optical properties will be discussed with regards to the terbium local environment and expected luminescence features.

Modifications induced by acetylacetone in properties of sol-gel derived Y(3)Al(5)O(12) : Tb(3+)- I: structural and morphological organizations.

Acetylacetone has been used as a chemical modifier for the synthesis of undoped and Tb(3+)-doped Y(3)Al(5)O(12) powders. 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. (27)Al 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 degrees 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.

Clicked dipicolinic antennae for lanthanide luminescent probes.

4-Triazolyl-dipicolinic acids, prepared efficiently by CuAAC, proved to act as efficient antennae for optical lanthanide probes containing Eu(3+) or Tb(3+), under linear and non linear excitations (one, two and three photons provided by laser induced luminescence). The versatility offered by the substitution of the triazole subunit is, in addition, useful for covalent linkage to slide glass providing luminescent films.

Luminescence dynamics in Tb(3+)-doped CaWO(4) and CaMoO(4) crystals.

Single crystals of CaWO(4) and CaMoO(4) doped with Tb(3+) have been grown by the flux growth method. Their luminescence properties have been investigated in the 10-600 K temperature range under different experimental conditions. In spite of very similar spectra at low temperature upon excitation at 365 nm, the crystals show a very different behavior as the temperature is raised or the excitation wavelength is changed. These differences have been accounted for on the basis of models that take into consideration the position of the energy levels of the rare earth relative to the bandgap of the host material.

Metal-NHC complexes: a survey of anti-cancer properties.

New weapons to fight cancer are constantly needed. Among chemotherapeutics, anti-cancer metal-drugs have enjoyed a long and successful history since the discovery of the benchmark cisplatin. Advances in metal-drug discovery have motivated chemists to build plethora of complex structures. Among them, a novel area is emerging. This article presents a survey of the metal-N-Heterocyclic Carbenes (Ag(I), Au(I), Pd(II) and Cu(I)-NHCs) as potential anti-cancer agents. Most of the metal-NHCs considered display higher cytotoxicities than the reference metallo-drug cisplatin. Some of them are even selective for particular cell lines. Their mechanisms of action at the cellular level are further discussed, showing that the nature of the metal is of great importance. All these promising results demonstrate that this approach deserves more attention and work.