Jun Yang,Jingjing Cao,Dingyi Shen,Jie Xiong,Jianfeng Tang,Shanshan Hu
Well-crystallized and uniform ScPO4·2H2O and ScPO4·2H2O:Ln3+ (Ln = Ce, Eu, Tb, Lu) nano/micro-crystals with multiform morphologies, such as sphere, hexagonal plate, diamond, four-angle star, butterfly-shaped and cuboid, have been successfully synthesized by a facile hydrothermal route without any surfactant molecules. XRD, FE-SEM, TEM, PL and kinetic decay were used to characterize the as-prepared products. The size and morphology of ScPO4·2H2O can be determined by the pH value, reaction time, reaction temperature, additive and doping of lanthanide ions. In particular, Ln3+ doping not only has a crucial role in the morphology of ScPO4·2H2O, but also affects its luminescence properties. The ScPO4·2H2O:Tb3+ and ScPO4·2H2O:Ce3+ samples display intense green and blue emissions, respectively. More importantly, the luminescence properties are closely related to morphologies and crystallinity. It can be found that the ScPO4·2H2O:Tb3+ sample with a hexagonal plate-like morphology possesses much higher emission intensity than those with other morphologies because of its larger anisotropic geometry. ScPO4:Ln3+ crystals will become promising candidates for a variety of applications in down/up-conversion luminescence, magnets, lasers, and bio-labeling.
Single-host white light-emitting diodes with good stability and simple fabrication methods have attracted extensive attention from researchers. In this study, Cs2NaGdCl6:Sb3+ with blue emission is synthesized by introducing Sb3+ into Cs2NaGdCl6. After doping Tb3+ into Cs2NaGdCl6:Sb3+, the sample achieves a tunable ion emission from blue to green. The energy transfer relationship between Sb3+ and Tb3+ is explored. White phosphors with CIE coordinates of (0.34, 0.33) are obtained by introducing Ho3+ into Cs2NaGdCl6:Sb3+/Tb3+ double perovskites. This work provides a new option for white light emission of halide perovskites doped with Ln3+.
Jie Xiong,Wei Wang,Yini Mao,Qingyuan Liu,Jun Yang,Jianfeng Tang,Shanshan Hu
BaLu2−xF8:xLn3+ crystals have been synthesized via a one-step hydrothermal route without any surfactants. X-ray diffraction (XRD), scanning electron microscopy (SEM), and down-shift/up-conversion photoluminescence spectroscopy were used to characterize the samples. Pure monoclinic BaLu2F8 crystals were obtained at pH = 7 with NaBF4 as a fluoride source. Doping 0.06 mmol Ln3+ ions from Ho3+ to La3+ and doping Yb3+ ions from 0.1 to 0.4 mmol both have caused dramatic changes to the product's morphology from prismatic microrods of about 10 μm to particles of about 3 μm aggregated by flakes. The differences in the phase, size and shape of the final products were greatly related to the fluoride source and pH values, which have been studied in detail. In addition, surfactants also affected the phase and morphology of the BaLu2F8 crystals. Multicolor down-shift emission was achieved in the BaLu1.94F8:0.06Ln3+ (Ln = Sm, Eu, Tb, Dy, Er and Tm) crystals under UV lamp excitation at 365 nm, and multicolor UC luminescence has been achieved in BaLu2F8:Yb3+,Ln3+ (Ln = Er, Tm, Ho) systems. When the Yb3+–Er3+ ions are co-doped into the host, the mechanism for the red emission (4F9/2 → 4I15/2) retains the tri-photon process like the single-doped Er3+ ion, but the mechanism for the green emission (2H11/2/4S3/2 → 4I15/2) is a two-photon process. Furthermore, the UC luminescence mechanism for the co-doped Yb3+–Ho3+ pairs is also a tri-photon process in the BaLu2F8 matrix. The as-prepared BaLu2F8:Ln3+ phosphors have potential applications in the fields of light emitting devices, three-dimensional displays and backlights.
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