A new, AIE-active "butterfly-shaped" Salicylaldehyde Schiff Base as a turn-on Fluorescent Probe for Highly Selective...

The development of highly selective and sensitive fluorescent chemosensors is urgently needed to detect toxic aluminum ions (Al³⁺) ions in environmental and biological systems. This work presents the development of a novel Schiff-base fluorescent probe L, which was efficiently synthesized via a one-pot condensation reaction between 3,5-di-tert-butylsalicylaldehyde and 4,5-dimethyl-1,2-phenylenediamine. The molecular structure of the probe L was characterized using nuclear magnetic resonance spectroscopy (¹H/¹³CNMR) and infrared spectroscopy (FT-IR). Fluorescence spectroscopy studies have shown that probe L exhibits specific recognition of Al³⁺ in ethanol/PBS solutions. After adding Al³⁺, the fluorescence at 547 nm is significantly enhanced, displaying a bright green fluorescence under 365 nm ultraviolet light, and it is not interfered with by other metal ions such as Na⁺, K⁺, Ca²⁺, Mg²⁺, Fe³⁺, Cu²⁺, and Zn²⁺. Job's plot and theoretical calculations confirm that probe L forms a 1:1 complex with Al³⁺, with a binding constant (K_a) of 2.64 × 10⁴ ± 44.67 M^- 1, and a detection limit (LOD) as low as 1.19 µM. This probe maintains stable recognition performance under a wide range of environmental conditions and has significant potential applications in environmental monitoring.