A luminescent voyage: from highly sensitive hypochlorite fluorescence sensing to multilayered information encryption storage

Abstract

Stimuli-responsive organic materials with controllable luminescence properties have great potential in fields such as sensing and data security. In this work, the novel aggregation-induced emission (AIE) materials 4-(4-(4-(methylthio) phenyl)phthalazin-1-yl)-N,N-diphenylaniline (TSA) and 4-(4-(4-(ethylthio)phenyl)phthalazin-1-yl)-N,N-diphenylaniline (TSB) were constructed through a simple two-step reaction. Their AIE properties were significantly enhanced through a molecular engineering strategy (alkane chain modification and intramolecular charge transfer regulation). In terms of fluorescence sensing, TSB used the thioether group as a specific recognition site, which could detect ClO⁻ with high sensitivity. The detection limit was as low as 2.1 nM, and a large Stokes shift of 181 nm was observed, effectively reducing background interference. The TSB probe successfully achieved dynamic visualization monitoring of ClO⁻ in living cells and exhibited low cytotoxicity. In addition, portable cotton swabs based on TSB could enable the rapid on-site detection of ClO⁻ in water samples within 1 minute, with simple operation and intuitive results. The work further revealed the dual-mode dynamic response of the piezochromism and vapochromism of TSB. Its highly twisted molecular conformation and loose packing mode could reversibly regulate the changes in fluorescence under mechanical pressure or solvent vapor. Combining X-ray diffraction and single-crystal structure analysis, the structure–activity relationships between the molecular packing mode and piezochromism were elucidated. We innovatively developed a multi-stage information encryption, storage and stable decoding strategy through the synergistic regulation of pressure and vapor.