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Enhancing the moisture resistance of Mn4+-doped fluoride phosphors is crucial for solid-state lighting (SSL) and liquid crystal display (LCD). Herein, the deteriorated K2AF6:Mn4+ (A = Ti, Si) phosphors were restored with Na2SO3 alkaline reductant, and optimal treatment conditions were systematically determined. The kinetic process for luminescence degradation and restoration, as well as the corresponding reparation mechanism were investigated in detail. These results showed that SO32− anion can reduce Mn4+ to Mn2+, rapidly remove the dark-brown layer of the degradation product, and restore the luminescence intensity of K2AF6:Mn4+ to more than 95%. Therefore, the restored K2TiF6: Mn4+ and K2SiF6: Mn4+ samples exhibit excellent moisture resistance, maintaining to be 66 and 76% of the initial intensity after immersing in deionized water for 300 min. Furthermore, fabricated white light-emitting device using the restored K2TiF6: Mn4+ phosphor also possess color rendering index of 94.2 and correlated color temperature of 3270 K. Our results provide a feasible strategy to significantly improve the moisture resistance of fluoride phosphors, demonstrating a great promise in phosphor-converted white-LED toward lighting and display field. [ABSTRACT FROM AUTHOR]

A series of Er3+, Tm3+, Yb3+ co-doped or tri-doped SrLu2O4 phosphors were synthesized by a high-temperature solid-state reaction method. The crystal structure was characterized by X-ray diffraction technique and further validated by Rietveld refinement. The chemical composition and elemental distribution of tri-doped sample were determined by the energy-dispersive spectrometry. It is worthwhile to note that the upconversion (UC) luminescence of as-prepared samples could be precisely controlled by adjusting the Yb3+ doping concentration and the excitation pump power. A bright UC white light in Er3+/Tm3+/Yb3+ tri-doped SrLu2O4 samples was observed by controlling the intensities of red, green and blue emissions. Under various pump powers in the range of 290-810 mW, the color coordinates could be effectively tuned in a quite broad white region. Particularly, the color coordinate of optimal sample under 630 mW at 980-nm excitation is (0.3336, 0.3244), which is very close to the standard white-light illumination (0.333, 0.333) and the corresponding correlated color temperature is 5442 K. Based on the UC emission spectra and luminescence decay curves, the energy transfer (ET) mechanisms involved in the different UC processes were proposed in detail. The results imply that ET processes of Yb3+ → Er3+, Yb3+ → Tm3+ and Tm3+ → Er3+ worked simultaneously in tri-doped system and produced white UC emissions by means of two- or three-photon processes. The Er3+/Tm3+/Yb3+ tri-doped SrLu2O4 phosphor can be a potential candidate for white UC material in displays, backlights and white-light sources. [ABSTRACT FROM AUTHOR]

Eu-doped BaAlO red phosphors were synthesized by high-temperature solid-state reaction. The crystal structure, morphology and luminescence properties were investigated by XRD, TEM and photoluminescence spectroscopy. The effect of calcination temperature, Eu concentration as well as charge compensators on the luminescence properties was also investigated. Characteristic orange-red emission at 589 nm was detected under 394 nm excitation. The best performance could be derived for the sample calcined at 1450 °C. With the increase of Eu concentration, the emission intensities increased gradually up to the Eu concentration of 12 %. The emission intensities could be enhanced with Li, Na and K introduced as charge compensators. The results showed that BaAlO:Eu phosphors with charge compensator had potential application in the fields of near-UV-excited WLEDs. [ABSTRACT FROM AUTHOR]

Mesoporous hydroxyapatite (meso-HA) thin films were fabricated by a sol-gel method using cetyltrimethyl ammonium bromide as the template. The phase, surface morphology, and mesoporous structure of the meso-HA films were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The uniform thin films consisted of meso-HA spherical particles with different pore size (2.0 or 3.1 nm) were prepared on the glass substrate at different pH value (pH 3.0 or 7.0). The introduction of mesopores would enhance the surface area of HA. Water contact angle was also measured on the non-mesoporous and meso-HA thin films, revealing the promotion of surface wettability in the mesoporous ones. In vitro cytocompatibility of HA films were evaluated by cell adhesion and proliferation tests using MC3T3-E1 cells. After 3 days of culture on the samples, the cells spread in an elongated shape and were well adhered to the surface of the meso-HA films. Moreover, the cells proliferation on the meso-HA films was higher than that on the non-mesoporous films. There are significant differences in the cell density between the control group and the meso-HA films with the pores sized in 2.0 nm after being cultured for 2 and 3 days ( P < 0.05). The results suggested that the presence of mesopores could influence the surface and biological properties of HA films, and the mesoporous structure would enhance the cell response of HA. [ABSTRACT FROM AUTHOR]