Multimodal dynamic luminescence of self-activated Na2CaGe2O6 phosphor via defect manipulation.

Anti-counterfeiting using multiple optical output modes has drawn considerable attention for enhancing anti-fake measures. Herein, a multimodal dynamic optical information coding from the self-activated Na₂-CaGe₂O₆ phosphor is developed. Na₂CaGe₂O₆ phosphor exhibits two distinct emission bands associated with the intrinsic defects of oxygen vacancies (V••_o) and inverse-site defects (Ge••_A). The incorporation of Bi³⁺ ions results in an increased concentration of defects, which in turn facilitates the modulation of the corresponding photoluminescence color from purple to red with prolonged ultraviolet (UV) irradiation. Moreover, the recovery of the corresponding emission color is observed for thermal disturbance. Besides, an improved optical storage behavior as the long persistent and photo-stimulated luminescence is achieved for the incorporation of Bi³⁺ ions. Consequently, a multimode dynamic color-changing code is constructed using screen-printing technology, offering an alternative approach for advanced anticounterfeiting. [ABSTRACT FROM AUTHOR]