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This study presents the intercalation into Layered Double Hydroxides (LDHs) of two sulfonated organic molecules featuring the mesoionic triazolium scaffold. These sulfonated fluorophores exhibited excellent solubility in aqueous basic solutions, facilitating their compatibility with the synthesis of LDHs through coprecipitation methods. We applied the size-matching interlayer space (SMIS) approach by substituting a portion of a mono- or dianionic surfactant used in LDH preparation by the sulfonated fluorophore, we aimed to match the size of the luminescent interleaved guest effectively. Our investigation focused on two anion spacers: the classic monoanionic dodecyl sulfate (DS) and the dianionic phenylene dipropionate (PPA). Our results indicated that the latter spacer allowed a more efficient insertion of the fluorescent guest. Thermal resistance analysis underscored the robustness of the final hybrid materials, suggesting a promising design strategy for luminescent materials when applied in diverse applications. [ABSTRACT FROM AUTHOR]

Starting from imidazolium chlorides bearing bulky nitrogen donors, a series of four complexes, mainly [Cu (C^N)Cl]n coordination polymers were obtained directly as luminescent species by simple filtration from the aqueous reaction medium, highlighting a simple, eco-friendly, robust and reproducible synthetic procedure. Additionally, we have shown on the most efficient example that chloride could be exchanged very easily by other halides/pseudohalides (Br-, I-, NCS-, N3 -) allowing to slightly modulate the emitted colour while conserving the polymeric structure, except for azide for which a dimer was obtained. The combination of chemical analyses, of photoluminescence studies in the solid state including quantum yield measurement and X-ray diffraction on single crystals and as-synthesized microcrystalline powders highlighted that the polymeric luminescent species was indeed obtained directly by simple filtration and that no major alteration of the structure was observed upon recrystallisation. Samples of all polymeric complexes displayed remarkable stability towards air oxidation remaining unchanged upon storage for several months and partially retaining their photoluminescence properties even after a thermal treatment at 100 °C for 24 h. [ABSTRACT FROM AUTHOR]

The use of sterically hindered N,N′-diisopropylbenzene-1,2-diamine (DIBA) for aminophosphine-based InP QDs synthesis in an oleylamine (OLAm) medium is evidenced as a powerful tool to finely control their size in a reproducible way. This diamine forms in situ a P-(DIBA)-(OLAm) species accounting for the observed size-tuning effect because the QDs crystallize as tetrahedra with an edge length (3.5 to 6.6 nm) depending on the DIBA concentration (0 to 7 eq./indium). This kinetically controlled size-tuning mechanism is proposed by combining 31P NMR and UV–vis spectroscopy. A proof-of-concept is established by coating the InP cores with ZnS shells. The luminescence of the as-synthesized InP/ZnS QDs is tunable over the 480–620 nm range, with photoluminescence internal quantum efficiencies of 45 to 60% suitable for applications as phosphors in LED lighting systems and LED displays. [ABSTRACT FROM AUTHOR]

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). [ABSTRACT FROM AUTHOR]

Uniform, hydrophilic 50 nm diameter Nd3+-doped Ba0.3Lu0.7F2.7 nanospheres are synthesized at 120 °C using a singular one-pot method based on the use of ethylene glycol as solvent, in the absence of any additive. The composition and crystal structure of the undoped material are analyzed in detail using ICP and XRD, which reveals a BaF2 cubic crystal structure that is able to incorporate 70 mol% of Lu ions. This finding contrasts with the reported phase diagram of the system, where the maximum solubility is around 30 mol% Lu. XRD proves as well that the Ba0.3Lu0.7F2.7 structure is able to incorporate Nd3+ ions up to, at least 10 mol%, without altering the uniform particles morphology. The Nd-doped particles exhibit near-infrared luminescence when excited at 810 nm. The maximum emission intensity with the minimum concentration quenching effect is obtained at 1.5% Nd doping level. X-ray computed tomography experiments are carried out on powder samples of the latter composition. The sample significantly absorbs X-ray photons, thus demonstrating that the Nd3+-doped Ba0.3Lu0.7F2.7 nanospheres are good candidates as contrast agents in computed tomography. [ABSTRACT FROM AUTHOR]

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→T1) upon NIR excitation. [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]

Sol-gel based layers doped with Rhodamine B phosphors (RB) were directly microstructured to produce sub-lambda 2D gratings, using nanoimprint lithography. Such an approach enables the simplification of technological processes, since no further etching process is required, which reduces considerably the number of technological steps and thus production costs. Surface microstructuring improved fluorophore emission in the visible range. Demonstrations were performed experimentally and samples were characterized using angle-resolved fluorescence. The emissions measured on microstructured luminescent coatings were 3–4 times higher, depending on the angle of observation, than those recorded on flat surfaces. This technological approach is very promising for the next generation of low-cost, high-performance anti-counterfeiting marking processes and for the traceability of objects based on unique optical effects. [Display omitted] • Variations in photoluminescence quantum yields as a function of excitation wavelength and RB concentrations were studied • The nanoimprint lithography technique was used to produce a 2D grating on a luminescent (TEOS/MTEOS)/RB base sol-gel coating. • Surface microstructuring improved fluorophore emission in the visible range. • Angle-resolved photoluminescence was investigated on the luminescent films with and without grating. [ABSTRACT FROM AUTHOR]