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A variety of novel Dy3+/Eu3+ mono- and co-doped K 6 Bi 13 (PO 4) 15 (KBPO) luminescent materials have been fabricated by a simple solid-state method for the first time. Both experimental studies and theoretical calculations verify that the K 6 Bi 13 (PO 4) 15 crystals are suitable to be utilized as host materials for the lanthanide activator ions. The XRD, EDS, and XPS results reveal that the Dy3+ and Eu3+ have been effectively incorporated into the KBPO host matrix and do not damage the structure of KBPO. The Dy3+ or Eu3+ mono-doped phosphors display the characteristic spectral patterns of the activator ions upon UV excitation whereas an energy transfer between Dy3+ and Eu3+ occurs which helps to obtain the tunable luminescence of the KBPO:Dy3+,Eu3+ phosphors. The emission colors of the KBPO:Dy3+,Eu3+ regularly shift from green-blue, through white, and finally toward yellow and orange-red by varying the activator doping concentrations under a fixed excitation wavelength. Interestingly, the single-phase white light emitting phosphors with CIE chromaticity coordinates of (0.3122, 0.3106) and (0.3602, 0.3246) are obtained by doping appropriate concentrations of Dy3+ and Eu3+, which match well with the standard white light illuminate of (0.333, 0.333). Moreover, the annealing conditions are optimized and the luminescent mechanisms and temperature-dependent luminescence performance are systematically investigated. Finally, the WLEDs device prepared by KBPO:Dy3+,Eu3+ phosphor and UV chip displays a dazzling white light with favorable CIE (Commission Internationale de I'Eclairage 1931 chromaticity) coordinates, color rendering index (Ra), correlated color temperature (CCT), and thermal stability, which provides direct evidence that the as-prepared inorganic luminescent materials may have prospects as an eminent single-phase white light emitting materials for white light-emitting diodes (WLEDs) and optoelectronic devices. [ABSTRACT FROM AUTHOR]

A variety of Bi3+ and/or Eu3+ doped KBaYSi 2 O 7 phosphors with deep blue, cyan, orange-red, and white light multicolor emissions have been fabricated by a Pechini sol-gel (PSG) method. The KBaYSi 2 O 7 :Bi3+ phosphors exhibit an intense cyan emission or a unique narrow deep blue emission when excited by different wavelengths, which may bridge the cyan gap or act as a promising deep blue phosphor for white light-emitting diodes (WLEDs). The tunable multicolor emissions can be achieved by changing the Bi3+ doping concentrations. The Bi3+/Eu3+ co-doped KBaYSi 2 O 7 phosphors display intrinsic emissions of Bi3+ and Eu3+ and an energy transfer process between Bi3+ and Eu3+ can be detected. The luminescence colors of KBaYSi 2 O 7 :Bi3+,Eu3+ regularly shift from blue, through cold and warm white, finally toward orange-red by adjusting the relative doping concentrations of Bi3+ and Eu3+. The single-phase white light-emitting material can be generated in both cold and warm white regions by simply varying the Eu3+ doping concentrations. Furthermore, three kinds of WLEDs devices are fabricated by KBaYSi 2 O 7 :Bi3+ or KBaYSi 2 O 7 :Bi3+,Eu3+ phosphors, which can exhibit dazzling white light emissions with eminent CIE coordinates, correlated color temperature, and color rendering index. The result offers direct evidence that the as-synthesized phosphors may be potentially applied in WLEDs and solid-state lighting. [ABSTRACT FROM AUTHOR]

A variety of tetragonal Na 0.5 Gd 0.5 MoO 4 microcrystals with different morphologies, dimensions, side lengths, and heights (microplates, tetragonal, and quasi-cubic structures) have been synthesized by a novel inorganic salt assisted hydrothermal approach. The influence of the addition of inorganic salt NaNO 3 on the phase structure, morphology, particle size, and luminescence performance of the samples has been systematically studied for the first time. A series of Na 0.5 Gd 0.5 MoO 4 :Ln3+ (Ln = Eu, Tb, Dy, Sm, Yb/Er, Yb/Tm, Yb/Ho) phosphors with excellent down-conversion or up-conversion luminescence properties have been synthesized by doping proper rare earth activator ions into the host matrix. The addition of inorganic salt NaNO 3 and the calcination process can greatly improve the luminescence performances of the phosphors, which can be ascribed to the decrease of surface area and enhanced crystallinity of the Na 0.5 Gd 0.5 MoO 4 crystals. The as-obtained down-conversion and up-conversion multicolor luminescent materials show the intense characteristic emissions of Ln3+ and eminent thermal stability. Moreover, the corresponding LED devices fabricated by the phosphors display dazzling multicolor emissions, which directly verifies that the as-synthesized phosphors may have the prospect to be utilized in the field of optoelectronic devices and LEDs. [ABSTRACT FROM AUTHOR]

A facile, general, and synthesis method with low-cost has been explored to improve the stability of the CsPbBr 3 perovskite quantum dots (PQDs). During the synthesis process, the CsPbBr 3 PQDs are encapsulated into the strontium hydroxyapatite (SrHAp) matrix by a direct calcination process under high temperature in the air without any organic solvents, ligands, or polymer additives. The encapsulation strategy not only improves the luminescence efficiency of the PQDs but also greatly enhances their stability for long-term storage. The as-synthesized CsPbBr 3 @SrHAp composites possess many advantages including narrow-band emitting, high green color purity, and eminent stability, which may have prospects in the fields of solid-state lighting, optical displays, and optoelectronic devices. Furthermore, this feasible strategy may pave a critical way for improving the stability of all-inorganic CsPbX 3 (X = Cl, Br, or I) PQDs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Highly luminescent and stable CsPbX 3 @silica composites were obtained by a facile route. • The luminescent and mesoporous silica is employed as matrix to protect CsPbX 3 PQDs. • A remarkably enhancement of stability against temperature/storage/water is realized. • The formation mechanism and stability improvement mechanism have been discussed. • LED devices prepared with nanocomposites can emit dazzling characteristic emissions. The metal-halide perovskite quantum dots (PQDs) have been emerged as new stars of optoelectronic materials with fascinating luminescence properties. However, the poor stability of these materials severely restricts their practical applications. In this work, the novel defect-related luminescent mesoporous silica nanospheres are employed as protective matrix to improve the stability of PQDs for the first time. Firstly, the monodisperse CsPbBr 3 and CsPbBr 1.5 I 1.5 PQDs with perfect nanocube morphology and eminent luminescence properties have been prepared respectively by a facile synthesis strategy. Then, the CsPbBr 3 and CsPbBr 1.5 I 1.5 PQDs are encapsulated into the non-luminescent (SN) and luminescent silica matrix (DL-SN) respectively, resulting in the PQDs@SN and PQDs@DL-SN nanocomposites. The incorporation of the PQDs and silica matrix can be confirmed by XRD, FT-IR, TEM, XPS, elemental mapping images, N 2 adsorption/desorption isotherms, and density functional theory. The as-synthesized silica matrix especially for the DL-SN presents a remarkable enhancement of stability against temperature, storage time, and water for both CsPbBr 3 and CsPbBr 1.5 I 1.5 in comparison to the pristine PQDs. Furthermore, the formation mechanism and stability improvement mechanism have been discussed in detail. This work provides a facile and general approach to solve the intrinsic instability of all-inorganic PQDs, which may have a significant impact on their practical applications. [ABSTRACT FROM AUTHOR]

• A series of Ln3+-doped La 4 Ti 3 O 12 phosphors were synthesized by Pechini sol-gel method. • The crystal structure of La 4 Ti 3 O 12 is influenced by calcination temperature and time. • Both excellent DC and UC luminescence can be realized under UV or NIR excitation. • The influence of Ln3+ doping concentrations for DC and UC luminescence was studied. • The as-fabricated LED devices show dazzling characteristic emissions of activator ions. [Display omitted] A series of novel rare earth activator ions-doped perovskite-type lanthanum titanate La 4 Ti 3 O 12 phosphors have been synthesized via the Pechini sol-gel method. The influence of calcination temperature and time on crystal structure of the La 4 Ti 3 O 12 matrix is investigated, and the result indicates that higher temperature and longer calcination time is beneficial for better crystallinity. Upon ultraviolet excitation, the as-synthesized activator ions (Dy3+, Eu3+, Sm3+, and Tb3+) ions doped La 4 Ti 3 O 12 phosphors display the characteristic quasi-white, reddish orange, orange, and green emissions in visible region. The higher calcination temperature and longer time can induce stronger luminescence due to enhanced crystallinity of La 4 Ti 3 O 12 host. The optimal doping concentrations of Dy3+, Eu3+, Sm3+, and Tb3+ ions are determined to be 2, 12, 2, and 10 mol%, respectively. The corresponding LED devices fabricated by the phosphors and UV LED chips can exhibit bright characteristic multicolor emissions of activator ions, indicating their potential in LEDs and optoelectronic devices. Moreover, the up-conversion luminescence properties of the Yb3+/Er3+, Yb3+/Tm3+, and Yb3+/Ho3+ doped samples are also studied. The result shows that the excellent up-conversion performances can be also realized by doping appropriate rare earth ions into the host matrix by employing the NIR excitation. It is anticipated that this work may be of significance for the design and preparation of perovskite-type rare earth luminescent materials. [ABSTRACT FROM AUTHOR]