Multiband MgGeO₃-Based Persistent Luminescent Nanophosphors for Dynamic and Multimodal Anticounterfeiting

Persistent luminescence (PersL) materials are excellent candidates in the dynamic and multimodal anticounterfeiting field. Compared to commercially available micrometer-sized PersL phosphors, nanosized PersL materials could blend more easily with solvents and allow printing patterns with fine details. MgGeO3 is one of the frequently employed lattice hosts for PersL phosphors. It can accommodate divalent ions such as Mn2+ to produce deep-red PersL. To date, the only reported method of synthesizing nanosized Mn-doped MgGeO3 (MGO:Mn) is the sol–gel method. The synthesis product has a wide particle size distribution and suffers severe aggregation. In this work, MGO:Mn nanorods are synthesized, for the first time, with a uniformly distributed morphology. These nanorods exhibit more intense and longer-lasting PersL. A detailed comparative study between the MGO:Mn nanorods developed in this work and the MGO:Mn particles prepared by the sol–gel method is performed to identify the origin of the improved PersL property. We also demonstrate that the afterglow duration of the MGO:Mn nanorods can be further modulated by adding co-dopants such as Yb3+, Eu3+, and Li+. The Yb3+ dopant also introduces a second PersL emission band in the near-infrared region of ∼1000 nm. Using a combination of these MGO-based PersL nanorods, dynamic and multimodal anticounterfeiting can be achieved.