Multiresponsive tetrarylethylene-based fluorescent dye with multicoloreded changes: AIEE properties, acidichromism, Al3+ recognition, and applications

A novel fluorescent sensor BTAE-PA containing two tetrarylethylene (TAE) units linked through pyrimidine-2-amine was prepared, and its optical properties were systematically studied. BTAE-PA exhibited a typical aggregation-induced emission enhancement behavior, and its fluorescent properties could be efficiently modulated by acid/base and metal ions in THF. The protonated effect could induce significant acidichromism and 'turn-on' near-infrared emission with a large Stokes shift (Δλ = 225 nm). Furthermore, BTAE-PA was highly selective toward Al³⁺ with significant absorption (yellow → orange) and fluorescence (green → red) changes. A Job's plot established the 1 : 1 stoichiometry of the complex formation between BTAE-PA and Al³⁺, and the limit of detection for Al³⁺ was determined to be 1.30 × 10^-7 mol L^-1. Finally, we also demonstrated that BTAE-PA could be made into test paper strips for 'naked-eye' detection of acid/Al³⁺, and fluorescence imaging experiments proved that BTAE-PA is capable of achieving cell imaging with good biocompatibility. Therefore, the multi-stimuli-responsive and multicoloured display performance of BTAE-PA endows the material with potential applications in security ink, acid/Al³⁺ sensing, and bio-imaging.