Competitive Phase Transition of NaYS₂ in Non-Vacuum Environment for Cutting-Edge Anti-Counterfeiting

Recently, chalcogenides with layered structures exhibit promising applications in the fields of information chaos processing and compilation remodeling, yet facile synthesis of their microcrystals with multi-temporal and multi-modal luminescence remains a major challenge. Herein, a competitive phase transition to generate orderly layered NaYS₂ microcrystals is achieved by lattice reconstruction with introduction S²⁻ occupying a unique anionic site in non-vacuum sulfur-rich environment, revealing crucial role of competitive phase transitions in regulating material structure and properties. Simultaneous photoinduced luminescent chromism and photo-stimulated luminescence are attained by introducing Pr³⁺. Interestingly, broadband long-wavelength visible afterglow emission in 4f¹5d¹ cluster state is achieved and a reversible temporary change in upconversion emission from orange broadband to green narrowband occurs under continuous 980 nm excitation, which is attributed to ordered polarization of Pr³⁺ in YS₆ layer and injection of defects. Furthermore, by integrating long-lived down-conversion emission and relatively short-lived up-conversion emission in Pr³⁺-doped NaYS₂, a multilevel dynamic optical anti-counterfeiting platform is constructed based on transient and long afterglow luminescence. This work implements a competitive phase transition to generate NaYS₂ with 2D structure, providing a new model of tunable space-time resolved emission for spatiotemporal optoelectronic multiplexing, which are applicable to large-capacity information encryption, optical data storage, and biosensing. © 2025 Wiley-VCH GmbH.