Stepwise Functionalization-Induced Molecular Tweak Unveiling Multi-Level Thermochromic Data Encryption and Fingerprint Monitoring System

Abstract

Protecting hierarchical data via multi-level encryption and authenticating high-contrast touch traces represents an emerging frontier demanding technological innovation in molecular materials. Herein, via precise molecular interventions, three D–A–A' (Donor-Acceptor-Acceptor) type aggregation induced emission (AIE)-active positional isomers (p-TPy, m-TPy, and o-TPy) are designed by varying the pyridine ring position in the acceptor. Their systematic investigation reveals key photophysical and structure–property insights, revealing their potential in advanced security and encryption. Positional modulation regulates electron-accepting strength and molecular packing, leading to red-shifted solid-state emission and influencing PLQY, transient PL, solvatochromism, and thermal stability as supported by crystal analysis and theoretical calculations. These stimuli-adaptive isomers address two critical challenges in advanced security systems. First, thermochromic luminescent materials (TLMs) exhibiting multiple temperature-dependent luminescent states are formulated as security inks by doping the para-isomer into phase-change matrices, enabling a multi-level security system. Second, a red-emissive, water-soluble amphiphilic fluorescent probe is obtained by functionalizing the para-isomer into a pyridinium emitter (p-TPyMe), capable of detecting latent fingerprints on diverse substrates and revealing level-3 ridge details with an exceptional contrast value of 5.39. These results demonstrate how molecular design in single chromophores translates into strategic AIE-active stimuli-adaptive positional isomers with intricate structure–property relationships, highlighting their potential for next-generation anti-counterfeiting, data encryption, and forensic technologies.