MPa‐Level Piezochromic Excimer Switching for Self‐Erasing Visual Encryption

Résumé fourni par la source

Piezochromic fluorescence usually requires high pressure and often suffers from intensity quenching, limiting its utility in encryption and optical security. Here we uncover a previously unrecognized MPa-level dynamic excimer-switching mechanism in 9-phenylanthracene (An-Ph) microcrystals, enabled by pressure-induced reorganization within pre-associated J-type columns. Under increasing pressure (0-40 MPa), the emission evolves from blue → white → intense cyan, accompanied by enhanced rather than quenched brightness. Upon pressure release, unstable excimer states dissipate, yet the material still exhibits bright white emission with a high quantum yield (67.2%) from a mixed monomer-excimer output. A 3D chromaticity trajectory is introduced to precisely visualize monomer-excimer conversions, revealing reversible optical pathways inaccessible to conventional CIE mapping. Single-crystal analysis and molecular dynamics jointly elucidate the formation and relaxation of multiple Y- and X-type excimer conformations under MPa-level stresses. Finally, we demonstrate a recyclable, mechanically triggered self-erasing QR/Morse encryption system, highlighting the material's potential for dynamic, time-gated security. This work establishes a general design framework for low-pressure excimer activation and mechanically adaptive photonic materials.

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