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In the arena of advanced anti-counterfeit research, developing a multi-level, anti-counterfeit material with tunable luminescence is a hot topic. However, current research has mainly focused on the visible light signal, despite the fact that near-infrared is also suitable for optical anti-counterfeit applications. The importance of the near-infrared signal is because it is more difficult to observe than the visible light signal. Here, a new, persistent, luminescent, near-infrared material composed of Zn 2+ x Ga 4-2 x Sn x O 8 :0.5%Cr3+ (x = 0-0.4) has been synthesized using the sol-gel method. A new anti-site-like defect [ Zn Ga ′ - Sn Ga. ] appeared after incorporating both Zn2+ and Sn4+, along with an intrinsic, anti-site defect [ Zn Ga ′ - Ga Zn. ]. Specifically, the former and latter defects contributed to the deep and shallow traps, respectively. Introducing Zn2+ and Sn4+ resulted in a significant, two-fold enhancement of the NIR emission intensity. This led to an obvious improvement in its persistent luminescence. In the absence of light irradiation, the NIR emitted light lasted for several hours. If heated, the disappeared NIR signal reappeared and lasted for 10 min. Primarily due to both the shallow and deep traps, the prepared samples exhibited dynamic NIR luminescence behavior. This behavior then contributed to the dynamic display information. Collectively, these results indicate that persistent phosphors have great potential for use in advanced, optical anti-counterfeit materials, owing to their ability to afford higher security. [ABSTRACT FROM AUTHOR]

Long persistent luminescence materials developed to commercial standards are primarily concentrated in the blue and green regions, with only a few in the red region. Red, as one of the three basic colors, can be mixed in various proportions with blue and green to yield various colors. The development of red persistent phosphors has a broader application potential but remains a challenge. A solid-state reaction method was used to synthesize new red persistent luminescent materials of Ba 1- x Sr x Ga 2 O 4 :Sm3+ (x = 0–0.09). In BaGa 2 O 4 , both Sr2+ and Sm3+ preferentially occupy the Ba2+ site rather than the Ga3+ site. When exposed to UV light at 254 nm, the phosphors emit the characteristic red emission of Sm3+ at wavelengths ranging from 500 nm to 750 nm. After removing the UV light source, an intense red afterglow that lasted more than 1400 s was observed. The red afterglow signal reappears after a heating process. Doping Sr2+ reduces the trap depth and improves the red persistent luminescence significantly. Because the escaped electrons from traps compensate for the emission loss of Sm3+ during the heating process, the red phosphors have unimaginably luminescent thermal stability. Thus, the emission intensity at 200 °C is 1.6 times that at room temperature. The prepared red persistent phosphors show multimode luminescence, with the output signal being time and temperature sensitive, indicating that they are potential luminescent materials for anti-counterfeiting applications. Finally, a building-block strategy for advanced anti-counterfeiting applications of dynamic display information is proposed, with red persistent phosphors serving as an important component combined with upconversion phosphors of NaYF 4 :Yb3+, Tm3+, and green persistent phosphors of SrAl 2 O 4 :Eu2+, Dy3+. [ABSTRACT FROM AUTHOR]