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Since the commercialization of white light-emitting diodes (WLEDs) in 1996, they are rapidly replacing conventional lighting sources and have become an essential commodity for day-to-day human life. At present, most of the WLEDs existing in the market are rare-earth based, which are very limited, expensive and often not available due to monopolistic supply conditions. Hence, there is a serious demand for novel rare-earth free phosphors to achieve cost-effective and energy-efficient WLEDs with excellent luminous efficacy for general illumination. Herein we report on highly efficient rare-earth free Cs(1−x)RbxVO3 phosphors as a single emitting compound for near UV-based WLEDs manufactured by the citrate sol–gel method for the first time. Rietveld refinement is performed for the X-ray diffraction patterns of the CsVO3 host and CsVO3:0.25Rb phosphors to reveal their orthorhombic pyroxene structure. The difference in the ionic radii of Rb+ and Cs+ ions led to a more distorted VO43− tetrahedron with a broken Td symmetry, which allows spin forbidden transitions for CsVO3:0.25Rb phosphors, resulting in enhanced internal and external quantum efficiencies of 94.7% and 84.5% along with superior luminescence properties compared to the CsVO3 host. When varying the input current from 20 to 200 mA, the fabricated WLED exhibited a good color rendering index of 69.7–81.5 and an extremely high luminous efficacy of 94.8–58.7 lm W−1, which are among the highest values for the same host lattice. These rare-earth free CsVO3:0.25Rb phosphors with a single emitting center may emerge as a new class of advanced inorganic phosphors for near UV-based WLEDs in the lighting industries. [ABSTRACT FROM AUTHOR]

We report a facile and large-scale synthesis of size-tunable and nontoxic mesoporous silica-coated Gd2O3:Eu3+ (Gd@mSi) core–shell nanostructures using a TPAOH assisted modified UHP technique. The role of TPAOH in controlling the particle size was evaluated. The potentiality of these Gd@mSi core–shell nanoparticles before and after folic acid conjugation was established by in vitro fluorescence microscopy of the U2OS cell lines for cancer imaging and therapy. [ABSTRACT FROM AUTHOR]

Nanostructured inorganic materials are potential building blocks for advanced materials and devices with desired functions. Latent fingerprint technology requires cost-effective and high-quality luminescent nanomaterials to identify an individual with sufficient information. We report the synthesis and growth mechanism of novel nanostructured CaGd2ZnO3(CO3)2·H2O and CaGd2ZnO5 materials through a urea- and EDTA-mediated hydrothermal process. The conversion from the carbonate to the oxide form is explained using physicochemical measurements. Furthermore, when doped with Eu3+ ions, CaGd2ZnO5 nanostructures exhibit superior luminescent properties to replace conventional red phosphors for latent fingerprint technology. In contrast to previously reported individual fluorescent nanoparticles, CaGd2ZnO5:5Eu3+ nanostructures provide three levels of identification with high-quality imaging on various hydrophilic and hydrophobic substrates. These properties demonstrate that CaGd2ZnO5:Eu3+ nanorod bundles are a promising luminescent material for solid-state lighting and latent fingerprint technologies. [ABSTRACT FROM AUTHOR]

Single, double and triple trivalent rare-earth (RE3+ = Dy3+, Tm3+, Tm3+/Dy3+ and Tm3+/Dy3+/Eu3+) ions activated Sr2Gd8(SiO4)6O2 (SGSO) phosphors were synthesized by a sol–gel process. X-ray diffraction profiles confirmed their oxyapatite structure after annealing at 1450 °C for 12 h. Morphological studies were performed by taking scanning and transmission electron microscopy images, which displayed rod-like shapes. SGSO phosphors exhibited good photoluminescence (PL) properties in the respective regions when doped with Dy3+ and Tm3+ ions. Dy3+ co-activated SGSO:Tm3+ phosphors revealed tunable emissions from cool white light to warm white light towards the yellow region based on the co-activator concentration. However, Eu3+ ions co-doped SGSO:Tm3+/Dy3+ phosphors tuned the emissions towards the red region. The energy transfers from Tm3+ to Dy3+ ions and Tm3+/Dy3+ to Eu3+ ions were established based on the energy level diagram. The cathodoluminescence properties of these phosphors showed excellent emission behavior when the single, double or triple trivalent RE ions were doped into the SGSO host lattice. Unlike the case of the PL, the energy transfer process was observed to take place. The calculated Commission Internationale de l'Eclairage chromaticity coordinates of Tm3+ and Dy3+ individual ion doped SGSO phosphors confirmed the blue and white emissions, while the co-doped samples exhibited tunable emissions. [ABSTRACT FROM AUTHOR]

A series of Eu3+ ions activated Ba4La6(SiO4)6O (BLSO:Eu3+) phosphors were synthesized by a modified citrate sol–gel process. The structural properties of these phosphors were explored by means of X-ray diffraction (XRD) and Fourier transform infrared spectroscopy. The XRD patterns confirmed their oxyapatite structure with the space group of P63/m after annealing at 1400 °C. The scanning electron microscope image exhibited the irregular morphology of BLSO:Eu3+ particles and the elemental mapping confirmed that the Eu3+ ions were distributed homogeneously on the La3+ ion sites. Photoluminescence (PL) excitation spectra of BLSO:Eu3+ exhibited the charge transfer band (CTB) and intense f–f transitions of Eu3+ ions in the violet and blue wavelength regions. The CTB intensity decreased and the f–f transition of Eu3+ ions increased with increasing the Eu3+ ion concentration due to the presence of defects in the 4f and 6h sites of the BLSO host lattice. This feature facilitates the strong absorption in the near-ultraviolet (NUV) region, which is useful for high color rendering index NUV based white light-emitting diodes for display and lighting applications. The PL spectra displayed intense red emission (5D0→7F2) along with considerable orange emission (5D0→7F1) with good asymmetry ratios and chromaticity coordinates, and exhibited better emission performance than that of commercial Y2O3:Eu3+ phosphors. The three-dimensional PL spectra revealed their strong emission characteristics under UV, NUV and visible excitation wavelengths. The cathodoluminescence properties were also similar to the PL results, confirming that the BLSO:Eu3+ phosphors emit stable red emission under different excitation sources as compared to the commercial Y2O3:Eu3+ phosphors. [ABSTRACT FROM AUTHOR]

Oriented attachment assisted self-assembled three-dimensional (3D) flower-like La(OH)3:Eu3+ nanorod bundles were successfully synthesized by a facile wet-chemical method. Hexamethylenetetramine played an important role in the formation of the hexagonal phase of La(OH)3:Eu3+ with respect to the reaction time and its concentration. No other surfactants or capping agents were used. The calcination temperature did not show any influence on the morphological texture, and the La2O3:Eu3+ phase was obtained by a subsequent annealing process. The phase formation and morphological properties were confirmed by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The photoluminescence properties were studied for both the synthesized La(OH)3:Eu3+ and La2O3:Eu3+ samples, and also compared with that of the solid-state reaction based La2O3:Eu3+ phosphor. The 3D flower-like La2O3:Eu3+ nanorod bundles showed an intense red emission due to the hypersensitive 5D0→7F2 transition with good asymmetric ratio and chromaticity coordinates. Likewise, a systematic study of the cathodoluminescence (CL) properties was carried out in detail. Furthermore, to estimate the CL potentiality, the La2O3:Eu3+ phosphor was compared with a commercially available Y2O3:Eu3+ red phosphor. [ABSTRACT FROM AUTHOR]