"Turn-on" fluorescence sensor for Sc³⁺ based on Schiff-based tetraphenylethylene

"Turn-on" fluorescent sensors have garnered significant attention for their high signal-to-noise ratio. However, the development of aggregation-induced emission (AIE) probes for Sc³⁺ detection remains limited, with only a few examples reported to date. In this work, we rationally designed and synthesized a novel tetraphenylethylene (TPE) derivative functionalized with Schiff-base-bridged isophthalhydrazide, achieving a satisfactory yield of 85%. The probe exhibits prominent AIE characteristics and demonstrates exceptional selectivity toward Sc³⁺ over a wide range of competing metal ions, including representative lanthanides, in THF/H₂O (5 : 95, v/v) mixed medium, accompanied by a significant fluorescence "turn-on" response upon Sc³⁺ binding. The detection limit was determined to be 3.57 × 10^-8 M. A comprehensive mechanistic investigation, including fluorescence titration, FT-IR, ¹H NMR, and mass spectrometry, unequivocally established a 1 : 1 binding stoichiometry between the probe and Sc³⁺. Furthermore, the practical applicability of this sensor was successfully validated through test strip experiments and simulated water sample analyses, highlighting its potential for environmental monitoring and Sc³⁺ detection in aqueous-organic mixed media.