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The near‐infrared (NIR) persistent luminescence (PersL) materials have attracted widespread attention owing to the unique self‐sustained light with good penetrability. Currently, most of the reported NIR PersL materials are activated by Cr3+. Considering the potential toxicity of chromium ions, there is an urgent requirement to explore the Cr3+‐free NIR phosphors. Herein, a novel NIR phosphor Sr2LuSbO6:Fe3+ (SLSO:Fe3+) is prepared and its luminescence properties are systematically studied. The Fe3+‐activated Sr2LuSbO6 exhibits a long‐wavelength NIR emission band centered at 890 nm with a 110 nm full‐width at half maximum (FWHM), and its PersL can last over 18 h. The phosphor shows excellent PersL stability even after being dispersed in solutions of different environments for 7 days. Furthermore, the PersL emitted by the phosphor can penetrate the 2 cm thickness beef, evidencing its good NIR PersL penetration property. This work provides a novel NIR PersL materials based on Fe3+ luminescence for technological applications and also contributes to accelerate the development of new‐generation Fe3+‐doped NIR PersL phosphor toward versatile applications. [ABSTRACT FROM AUTHOR]

A series of novel non-gallate near-infrared (NIR) Mg2InSbO6:Cr3+ phosphors were successfully prepared using the solid-state reaction method. With the strong crystal field, double-perovskite oxide Mg2InSbO6:Cr3+ under ultraviolet (UV) excitation exhibits intense NIR emission centered at 698 nm with an internal quantum efficiency of 70.8%. Apart from photoluminescence, NIR persistent luminescence can also be detected from the Mg2InSbO6:Cr3+ phosphor. The persistent luminescence from the optimized sample Mg2InSbO6:0.3 mol% Cr3+ can still be recognized after ceasing the 365 nm UV excitation for 24 h with the aid of a night-vision instrument. These phosphors can be photostimulated by NIR light rapidly to enhance the NIR signal. The persistent luminescence of Mg2InSbO6:Cr3+ can penetrate beef of 4 cm thickness, which suggests its great potential in biological imaging application. Based on the results of persistent luminescence and thermoluminescence, a feasible afterglow mechanism of the Mg2InSbO6:Cr3+ phosphor is proposed and discussed. The present work might provide a new perspective for developing novel NIR phosphors with high quantum efficiency and considerable persistent luminescence duration. [ABSTRACT FROM AUTHOR]

Bi3+ has gained increasing attention due to its abundant reserves, adjustable luminous colour and high chemical stability, therefore, Bi3+-activated luminescent materials have already been extensively applied in various fields. Herein, a novel blue-emitting CaNaSb2O6F:Bi3+ (CNSOF:Bi3+) phosphor with a pyrochlore-type structure with the space group Fd3¯m (277) was successfully synthesized. It exhibits a broad absorption band in the n-UV region (290–390 nm) and an ideal blue emission band centered at 441 nm. Interestingly, the wide emission peak of CNSOF:Bi3+ shows strongly temperature-dependent fluorescence properties and good thermal degradation resistance in the cycle temperature range from 298 K to 473 K, and the relative sensitivity is calculated to reach the maximum value of 2.34% K−1 at 423 K. Besides, the phosphor is different from a traditional optical temperature sensing material which shows the emission peak of trivalent rare earth ions. The wide emission peak makes the instrument insensitive to the peak shift, which dramatically reduces the requirement of the instrument, and the emission peak does not shift with the temperature to enhance the measurement stability, thus saving the cost. These results indicate that the CNSOF:Bi3+ blue emitting phosphor has potential applications in temperature sensing. [ABSTRACT FROM AUTHOR]

In this article, we synthesized a series of new warm-white emitting persistent luminescent phosphors by co-doping Zn2+ into Pr3+ activated BaLu2Al2Ga2SiO12, and systematically investigated the effect of Zn2+ co-doping on both their photoluminescence and persistent luminescence properties. Following the removal of UV excitation, the phosphor emits warm-white persistent luminescence consisting of greenish-blue and red emissions originating from 3P0 and 1D2 multiplet electron transitions at the 4f level of Pr3+. The luminescence properties of the Ba1−xZnxLu2Al2Ga2SiO12:Pr3+ phosphors can be modified by changing the content of Ba/Zn in the host, which affects the non-radiative energy flow between 5d1–3P0–1D2 levels and resultantly enhances the intensity of the 4f → 4f transition. Compared with the undoped sample, Zn2+ co-doping can significantly enhance the persistent luminescence intensity of the phosphors in the range of 400–800 nm and reduce the intensity in the UV region. Meanwhile, Zn2+ co-doping can also change the intensity ratio between the greenish-blue and red emissions, and the persistent luminescence color can be tuned from red to warm-white with the increase of Zn2+ concentration. Besides, the Zn2+ ions entering the crystal lattice also enhance the persistent luminescence performance by modifying the defect levels in the phosphor. For the optimized phosphor, bright warm-white persistent luminescence can be observed by the naked eye in the dark after the removal of the excitation source for 4 h. Based on the experimental results, a feasible mechanism was also proposed to reveal the persistent luminescence generation process for the BaLu2Al2Ga2SiO12:Pr3+,Zn2+ phosphor. [ABSTRACT FROM AUTHOR]

Phosphors for remote optical determination have gained great attention for their promising applications, due to their advantageous rapid and noninvasive detection compared to traditional thermometers. In this work, a novel white-emitting optical temperature sensor based on energy transfer in a Bi3+, Eu3+ and Tb3+ doped YBO3 crystal was designed. By making full use of the crystal structure information and an energy transfer strategy, we obtained a series of wide range color tunable phosphors including one with white emission, which makes it a candidate to replace phosphors for white light emitting diodes (WLEDs). The temperature sensitive energy transfer from the host and Bi3+ to Eu3+ and Tb3+ has been demonstrated by analyzing the spectra from phosphors with different concentrations of the doping ions, in which Bi3+ acts as both the emission center and sensitizer. By investigating the temperature-dependent emission of the white light emitting phosphor YBO3:0.04Bi3+,0.003Eu3+,0.008Tb3+, the absolute sensitivity value (Sa) and relative sensitivity value (Sr) were calculated in different temperature ranges of 200 to 300 K and 298 to 473 K, in which the maximum value of Sr reaches 0.57% K−1 at 398 K. Although the Sr values are not high enough for practical application, our design concept may provide a new perspective for developing novel multifunctional phosphors used as optical temperature sensors and WLED phosphors. [ABSTRACT FROM AUTHOR]

Traditional anti‐counterfeiting luminescent phosphors are usually composed of single‐mode photoluminescence materials, which greatly limits the security of encryption by its static fluorescent pattern. Herein, multi‐mode luminescence properties are achieved including fluorescence and persistent luminescence (PersL) within single host by co‐doping Bi3+ and Eu3+ in CaNaSb2O6F (CNSOF). A tunable emission is observed from blue (Bi3+, 3P1→1S0) to white and then to orange‐yellow (Eu3+, 5D1→7F2 and 5D0→7F0, 1, 2, 3, 4) as the excitation schemes, environment temperatures and doping level are modulated. Impressively, the blue emission attributed to the Bi3+ rapidly disappears after stopping the excitation light irradiation, and only the intense orange‐yellow PersL produced by Eu3+ can be observed. And a possible model for the energy transfer and PersL mechanism is proposed by the investigation crystal structure and photoluminescence/PersL. A schematic of security logo and digital information encryption is demonstrated using the prepared samples, which shows the dynamic evolution of the emission color and PersL brightness. The excellent property of multiple color outputs, different decay processes, and external field stimulation modes (including low energy light, thermal, and mechanical stimuli) present in CNSOF:Bi3+, Eu3+ provides a fast, low‐cost, and effective method for advanced anti‐counterfeiting and information encryption applications. [ABSTRACT FROM AUTHOR]

Bi 3+ has gained increasing attention due to its abundant reserves, adjustable luminous colour and high chemical stability, therefore, Bi 3+ -activated luminescent materials have already been extensively applied in various fields. Herein, a novel blue-emitting CaNaSb 2 O 6 F:Bi 3+ (CNSOF:Bi 3+ ) phosphor with a pyrochlore-type structure with the space group Fd 3̄ m (277) was successfully synthesized. It exhibits a broad absorption band in the n-UV region (290-390 nm) and an ideal blue emission band centered at 441 nm. Interestingly, the wide emission peak of CNSOF:Bi 3+ shows strongly temperature-dependent fluorescence properties and good thermal degradation resistance in the cycle temperature range from 298 K to 473 K, and the relative sensitivity is calculated to reach the maximum value of 2.34% K -1 at 423 K. Besides, the phosphor is different from a traditional optical temperature sensing material which shows the emission peak of trivalent rare earth ions. The wide emission peak makes the instrument insensitive to the peak shift, which dramatically reduces the requirement of the instrument, and the emission peak does not shift with the temperature to enhance the measurement stability, thus saving the cost. These results indicate that the CNSOF:Bi 3+ blue emitting phosphor has potential applications in temperature sensing.

In this article, we synthesized a series of new warm-white emitting persistent luminescent phosphors by co-doping Zn 2+ into Pr 3+ activated BaLu 2 Al 2 Ga 2 SiO 12 , and systematically investigated the effect of Zn 2+ co-doping on both their photoluminescence and persistent luminescence properties. Following the removal of UV excitation, the phosphor emits warm-white persistent luminescence consisting of greenish-blue and red emissions originating from 3 P 0 and 1 D 2 multiplet electron transitions at the 4f level of Pr 3+ . The luminescence properties of the Ba 1- x Zn x Lu 2 Al 2 Ga 2 SiO 12 :Pr 3+ phosphors can be modified by changing the content of Ba/Zn in the host, which affects the non-radiative energy flow between 5d 1 - 3 P 0 - 1 D 2 levels and resultantly enhances the intensity of the 4f → 4f transition. Compared with the undoped sample, Zn 2+ co-doping can significantly enhance the persistent luminescence intensity of the phosphors in the range of 400-800 nm and reduce the intensity in the UV region. Meanwhile, Zn 2+ co-doping can also change the intensity ratio between the greenish-blue and red emissions, and the persistent luminescence color can be tuned from red to warm-white with the increase of Zn 2+ concentration. Besides, the Zn 2+ ions entering the crystal lattice also enhance the persistent luminescence performance by modifying the defect levels in the phosphor. For the optimized phosphor, bright warm-white persistent luminescence can be observed by the naked eye in the dark after the removal of the excitation source for 4 h. Based on the experimental results, a feasible mechanism was also proposed to reveal the persistent luminescence generation process for the BaLu 2 Al 2 Ga 2 SiO 12 :Pr 3+ ,Zn 2+ phosphor.