Reversible Information Encryption Based on Ag/TiO2 Hierarchical Plasmonic Structures.

The escalating threat of information leakage necessitates the development of advanced, dynamic, and reversible encryption technologies beyond static optical encoding. Herein, we report a reversible information encryption platform based on Ag/TiO2 hierarchical plasmonic structures that simultaneously integrate region-specific surface-enhanced Raman scattering (SERS) response with a photocatalytic self-cleaning property. By combining photolithography and colloidal lithography, precise macroscale and microscale patterning of nanocone arrays (NCAs) and nanosphere arrays (NSAs) is achieved on the same substrate. The NCAs with an enhancement factor (EF) of 3.45 × 108 generate strong SERS signals for information readout, whereas the NSAs exhibit weak signals to produce misleading information. SERS intensity contrast between NCAs and NSAs enables spatially selective molecular and image encryption. Ingeniously, photocatalytic degradation enables information erasure and rewriting, offering a convenient strategy for constructing multilevel and reversible optical security systems. With high information density and excellent recyclability, this reversible information encryption platform represents a significant advancement in next-generation anti-counterfeiting and secure data storage.