Eu²⁺/Eu³⁺-Based Smart Duplicate Responsive Stimuli and Time-gated Nanohybrid for Optical Recording and Encryption

With the rapid development of information science, it is urgent that memory devices possessing high security, density, and desirable storage ability should be developed. In this work, a smart duplicate response of stimuli has been developed and a time-gate nanohybrid based on variable valence Eu²⁺/Eu³⁺ coencapsulated has been fabricated and acts as active material in the multilevel and multidimensional memory devices. The luminescence lifetime of Eu³⁺ in this nanohybrid gave a stimuli response due to which the energy level of the coordinated ligand could be modulated. Furthermore, by a simple sintering procedure, Eu³⁺ was partially in situ reduced to Eu²⁺ with a short lifetime in the system. And the in situ reduction ensured both Eu³⁺ and Eu²⁺ ions' uniform distribution in the nanohybrid and simultaneous response upon light excitation of variable valence Eu ions. Interestingly, Eu³⁺ revealed a prolonged lifetime because of the presence of an energy-transfer effect of Eu²⁺ → Eu³⁺. Such a nanohybrid had abundant luminescent properties, including the short lifetime of Eu²⁺, the energy transfer from the Eu²⁺ to Eu³⁺ ions, and the stimuli response of the Eu³⁺ lifetimes when exposed to acidic or basic vapor, thus giving birth to interesting recording and encryption performance in spatial-temporal dimensions. We believe that this research will point out a new direction for the future development of multilevel and multidimensional optical recording and encryption materials.