Dual-mode multicolor luminescence based on lanthanide-doped Na2CaGe2O6 phosphor for anticounterfeiting application

The lanthanide doped luminescent materials have been of great importance to the anticounterfeiting applications. At present, these materials combing with the up/down-conversion luminescence could provide a promising assumption to design an advanced anticounterfeiting. Herein, a series of distinct combinations of rare earth (RE3+) doped Na2CaGe2O6 phosphors are synthesized for dual-mode anticounterfeiting. An up-conversion luminescent phosphor Na2CaGe2O6: Ln3+, Yb3+ (Ln3+ = Er3+, Ho3+, Tm3+) is reported, which could emit green, red and blue light under 980 nm excitation, respectively. Based on the up-conversion luminescence of Na2CaGe2O6: Ln3+, Yb3+ phosphor, these samples could simultaneously possess three luminescent modes of up-conversion, down-conversion and persistent luminescence with rich emission colors due to the co-doping Tb3+ ions. Furthermore, the Na2CaGe2O6: Eu3+ phosphor could be efficiently excited by ultraviolet lamp around 393 nm and exhibits intense red down-conversion luminescence. These outstanding luminescent properties make as-prepared phosphors particularly attractive for multilevel anticounterfeiting.