Realizing Tunable Long Persistent Luminescent in Novel Cu2+-Doped NaGaO2 for Multi-Level Information Storage and Encryption

Anti-counterfeiting and encryption are key technologies for information transmission in modern society. However, most optical materials offer only a single fixed response mode, limiting their security level in advanced anti-counterfeiting applications. Exploring efficient and tunable long persistent luminescent (LPL) phosphors is urgently demanded and highly meaningful. In this work, a dual-site occupancy strategy is innovatively reported via Li⁺ doped NaGaO₂: Cu²⁺ (NGO: Cu²⁺/Li⁺) phosphors for enhancing LPL properties. To be specific, Cu²⁺ initially occupies both Na and Ga sites in NaGaO₂, producing orange–yellow LPL at 585 nm and near-infrared (NIR) emission at 712 nm, respectively. Furthermore, the introduction of Li⁺ will occupy the Na⁺ sites, attenuating the NIR emission and increasing the defect density of the oxygen-deficient states, which results in enhanced LPL intensity and prolonged afterglow time. Significantly, the obtained NGO:Cu²⁺/Li⁺ exhibits multi-emission modes with dynamic change of LPL time (10–20 min). More importantly, the NGO: Cu²⁺/Li⁺ has great potential applications in multi-level information storage and encryption.