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A series of Tb3+-doped Sr2YTaO6 double perovskite phosphors (SYT:Tb3+) were synthesized using a conventional solid-state reaction method. A strong green emission was observed in the SYT:Tb3+ phosphors, and the optimal doping concentration of Tb3+ was confirmed to be 5 mol%. The electric dipole-dipole interaction was ascribed to be the main mechanism for the luminescence concentration quenching. Analysis of the concentration-dependent fluorescence decay confirmed that the self-generated quenching model holds for the dynamic process of Tb3+ decays in SYT. Furthermore, the internal quantum efficiencies, non-radiative transition rates, and energy transfer rates of the 5D4 level for the SYT:Tb3+ samples were estimated, respectively. The luminescence thermal stability of the sample was also evaluated based on the Arrhenius model. The chromaticity shift of the SYT:5 mol% Tb3+ phosphor was examined to be 0.013 when the sample temperature was increased from 303 to 483 K, thus indicating excellent chromaticity shifting resistance under high temperature conditions. Moreover, the Judd-Ofelt parameters were calculated from the emission spectra of SYT:Tb3+ to be Ω2 = 0.29 × 10-20, Ω4 = 0.45 × 10-20, and &@937;6 = 0.72 × 10-20 cm², respectively. The fluorescence branching ratios and radiative transition rates for the 5D4 level were calculated based on the obtained Judd-Ofelt parameters. Finally, a white light-emitting diode (LED) prototype was assembled using a 310 nm LED chip combined with a prepared green SYT:Tb3+ phosphor and two other commercial blue and red phosphors. The obtained warm white light exhibits good chromaticity coordinates (0.32, 0.32) and a high color rendering index of 96.1. Based on the above results, it can be known that the prepared SYT:Tb3+ phosphors have a potential application as green emitting phosphors in white LEDs. [ABSTRACT FROM AUTHOR]

We discuss the distribution properties of cardinalities of row (column) space of Boolean matrices. A stronger result than that in [4] is proved to counter a conjecture of Konieezny [3]. [ABSTRACT FROM AUTHOR]

A novel method, electrospinning, was explored to prepare europium-doped YBO 3nanocrystalline phosphors. Narrow and size-controllable YBO 3nanotubes and nanowires were obtained, varying from 40 to 500 nm. The average wall thickness of the nanotubes was only 5−10 nm. The structural properties were characterized by X-ray diffraction (XRD), Fourier-transform infrared absorption (FTIR), electron spin resonance (ESR), field emission scanning electron micrographs (FE-SEM), and high-resolution transmission electron micrographs (HR-TEM). The results indicate that theYBO 3nanotubes and nanowires were hexangular in phase and single crystals or polycrystalline in structure. Some surface dangling bonds caused by transition metal ions lead to a change of the coordination number of boron from +3 to +4. The photoluminescent properties of the YBO 3: Eu 3+nanowires and nanotubes were also characterized. It was observed that the charge-transfer excitation bands of Eu 3+in the nanowires and nanotubes blue-shifted in contrast to those in bulk, because of the variation of coordination environments. [ABSTRACT FROM AUTHOR]

La2(MoO4)3 phosphors with various Eu3+ concentrations were prepared via a facile co-precipitation process. The crystal structure and morphology of the phosphors were characterized by means of XRD and field emission scanning electron microscope. The crystal unit cell parameters a, b, and c for the monoclinic phase La2(MoO4)3 were calculated to be 16.989, 11.927, and 16.086 Å, respectively. The average size of the phosphor particles was estimated to be around 88.5 nm. The Huang-Rhys factor was derived from the phonon sideband spectra to be 0.073. The self-generated quenching process of Eu3+ was explained based on Auzel's model, and the intrinsic radiative transition lifetime for 5D0 level was confirmed to be 0.99 ms. A new approach for calculating the Judd-Ofelt parameters was developed, meanwhile the Judd-Ofelt parameters Ωλ (λ = 2, 4, 6) of Eu3+ in La2(MoO4)3 phosphors were confirmed to be 10.70 × 10-20, 1.07 × 10-20, and 0.56 × 10-20 cm2, respectively. Finally, the optimal doping concentration for achieving maximum emission intensity was confirmed to be 17 mol. % by analyzing the concentration quenching. [ABSTRACT FROM AUTHOR]

Nd3+, Er3+ single-doped and Nd3+/Er3+ codoped tellurite glasses were prepared via a melt-quenching technique, and their optical transition properties were studied in the framework of Judd-Ofelt theory. The differential excited state absorption cross section from 4I13/2 to 4I11/2 was obtained based on the McCumber theory; furthermore, the optical gain coefficient spectrum for 4I11/2-4I13/2 transition was calculated. The energy transfers 4F3/2(Nd3+)14I15/2 (Er3+)-4I9/2(Nd3+)14I9/2(Er3+) and 4I13/2(Er3+)14I9/2(Nd3+)+4I15/2(Er3+)14I15/2(Nd3+) in the codoped sample were analyzed by using Föster-Dexter theory and Inokuti-Hirayama's model, respectively; meanwhile, the energy transfer rates for both the energy transfer processes were confirmed. The results indicated that Nd3+ may be a good sensitizer for Er3+ to obtain intense midinfrared emission, and that Nd3+/Er3+ codoped tellurite glass may be a good candidate media for mid-infrared lasers. [ABSTRACT FROM AUTHOR]

Ternary terbium complexes were fully encapsulated and uniformly distributed into the channels of unmodified and modified mesoporous molecule sieves of SBA-15 and characterized by transmission electron micrographs (TEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible (UV-vis) absorption spectra, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), and elemental analysis. The luminescent properties for the encapsulated complexes were systematically studied in contrast to the pure complexes, including excitation and emission spectra, fluorescence dynamics, photostability under UV exposure, and the temperature dependence of intensity and lifetime. The results indicate that the excitation bands assigned to the - electron transition of the ligands for Tb complexes encapsulated in SBA-15 were split into different components due to decreased symmetry and disappeared at long wavelengths. Owing to suppressed vibration transitions, the outer quantum efficiency of the 5D4-7FJ(J 0-5) emissions was enhanced largely in comparison to the pure complexes. In addition, the photostability and thermostability of the emissions were also improved considerably. [ABSTRACT FROM AUTHOR]

An inorganic−organic hybrid semiconductor, ZnS/CHA (CHA cyclohexylamine) nanocomposites was successfully synthesized via a solvothermal method using CHA as solvent, which yielded uniform and ultralong nanowires with widths of 100−1000 nm and lengths of 5−20 m. Changing the reaction conditions could alter the morphology and optical properties of the nanocomposites. The periodic layer subnanometer structures were identified by high-resolution transmission electron microscopy (HR-TEM) images, with thickness of ∼2 nm. The composites exhibited a very large blue-shift in their optical absorption edge as well as an exciton excitation band due to a strong quantum confinement effect caused by the internal subnanometer-scale structures. The pure hexagonal wurtzite ZnS nanowires were also obtained by extracting the ZnS/CHA nanocomposites with dimethyl formamide (DMF). In addition, the luminescent properties of exciton and defect-related transitions in different samples of ZnS/CHA were discussed in detail. [ABSTRACT FROM AUTHOR]