ZGSO Spinel Nanoparticles with Dual Emission of NIR Persistent Luminescence for Anti-Counterfeiting Applications

Abstract

The property of persistent luminescence shows great potential for anti-counterfeiting technology and imaging by taking advantage of a background-free signal. Current anti-counterfeiting technologies face the challenge of low security and the inconvenience of being limited to visible light emission, as emitters in the NIR optical windows are required for such applications. Here, we report the preparation of a series of Zn1+xGa2−2xSnxO4 nanoparticles (ZGSO NPs) with persistent luminescence in the first and second near-infrared window to overcome these challenges. ZGSO NPs, doped with transition-metal (Cr3+ and/or Ni2+) and in some cases co-doped with rare-earth (Er3+) ions, were successfully prepared using an improved solid-state method with a subsequent milling process to reach sub-200 nm size particles. X-ray diffraction and absorption spectroscopy were used for the analysis of the structure and local crystal field around the dopant ions at different Sn4+/Ga3+ ratios. The size of the NPs was ~150 nm, measured by DLS. Doped ZGSO NPs exhibited intense photoluminescence in the range from red, NIR-I to NIR-II, and even NIR-III, under UV radiation, and showed persistent luminescence at 700 nm (NIR-I) and 1300 nm (NIR-II) after excitation removal. Hence, these NPs were evaluated for multi-level anti-counterfeiting technology.

Development of NaY9Si6O26:Yb3+ phosphors with high thermal stability for NIR anti-counterfeiting: study of its crystal structure and luminescent properties

“…In recent years, counterfeiting technology of security materials has advanced, making anti-counterfeiting technology an important tool for protecting the legitimate rights of consumers and enterprises. 32,33 It is therefore imperative to develop new materials for advanced anti-counterfeiting security. For this application, it is necessary to develop an NIR-emitting material that is sensitive in the NIR region beyond the existing method of checking security through ultraviolet excitation.…”

Transition metal and rare earth doped Zn1.3Ga1.4Sn0.3O4 persistent phosphors for anti-counterfeiting applications

“…To further improve the security, other excitation sources could be envisioned in the future as the persistent luminescence materials possess very wide excitation ranges. [30][31][32]…”

Tunable Spinel Structure Phosphors: Dynamic Change in Near‐Infrared Windows and Their Applications

“…Moreover, the generation of trap states causes the afterglow of Cr 3+ -doped phosphors. [114][115][116] To apply in the advanced anticounterfeiting or security, the pattern can be arranged by different Cr 3+ concentrations with red emission and afterglow (Figure 16b,d). [117] In Figure 16d, the difference of Zn 2+x Ga 4−2x Sn x O 8 :0.5%Cr 3+ afterglow intensity can present different characters, such as 896 and 035.…”