Multimodal dynamic color-tunable persistent luminescent phosphor Ca3Al2Ge3O12:Mn2+,Cr3+ for anti-counterfeiting and industrial inspection

Abstract

Here, multimodal fluorescent materials of Ca₃Al₂Ge₃O₁₂:Mn²⁺,Cr³⁺ were synthesized by the traditional high-temperature solid-state reaction method. In this garnet Ca₃Al₂Ge₃O₁₂ structure, Mn²⁺ and Cr³⁺ ions occupy dodecahedral sites (Ca sites) and hexahedral sites (Al sites), and can produce dynamic color-tunable persistent luminescence at different concentrations, different excitations, and different temperatures; in particular, continuous luminescence with temperature (300 K–473 K) shows a color change from green to deep red. Through detailed pyrolysis studies and theoretical calculations, it is demonstrated that the double-trap structure existing in the host makes the persistent luminescence color temperature-dependent. Anti-counterfeiting and industrial inspection molds were successfully accomplished, which means Ca₃Al₂Ge₃O₁₂:Mn²⁺,Cr³⁺ may be used in anti-counterfeiting and industrial inspection.