Green and Near-Infrared Dual-Band Photoluminescence in γ-AlON:Mn²⁺ Enables High-Level Anticounterfeiting and Encryption

Multicolor luminescent materials hold great potential in high-level optical anticounterfeiting and encryption technologies. However, achieving multiple luminescence in a single phosphor with a single dopant, especially covering visible and invisible regions simultaneously, remains a standing challenge. Herein, we successfully realize a visible and invisible dual-band emission in single-doped γ-AlON:Mn²⁺ phosphors. Under 450 nm light excitation, the low-doped γ-AlON:<i>x</i>Mn²⁺ phosphors (<i>x</i> ≤ 0.02) emit a single narrowband green emission at 515 nm; however, when further increasing Mn²⁺ concentration, the heavy-doped γ-AlON:<i>x</i>Mn²⁺ (<i>x</i> ≥ 0.05) samples display an additional broad near-infrared emission band peaking at 730 nm. Such an intriguing dual-band luminescence spanning from visible to invisible regimes is assigned to the combined emissions of isolated tetrahedral Mn²⁺ ions and superexchange-coupled Mn²⁺-Mn²⁺ pairs in γ-AlON host. Exploiting the distinct photoluminescence in low- and high-doped γ-AlON:Mn²⁺ phosphors, we further realize a double-level optical anticounterfeiting and information encryption demonstration. This work first presents the green and near-infrared dual-emission in γ-AlON:Mn²⁺ phosphors, not only enabling high-level optical anticounterfeiting and encryption but also shedding light on luminescence tuning in inorganic phosphors.