A Highly Selective and Sensitive Turn-on Fluorescent Probe for Al³⁺ Detection: Properties and Applications

The development of fluorescent probe for Al³⁺ detection is of great significance in environmental and biological systems, and helps to study the role of aluminum ions in physiological and pathological processes. Therefore, a new aluminum ion fluorescent probe (2-hydroxy-5-methylbenzylidene)picolinohydrazide (HMPC) based on hydrazide Schiff base has been successfully synthesized and characterized. HMPC demonstrated a remarkable selectivity and pronounced enhancement in its fluorescence emission specifically towards Al³⁺ ions, which was attributed to the influence of intramolecular proton transfer and intramolecular charge transfer effect. The detection limits of HMPC in ethanol and acetonitrile, as deduced from the titration curve, were found to be 3.90 × 10^- 8 M and 1.87 × 10^- 8 M, respectively. Density Functional Theory calculations supported the proposed mechanisms. HMPC has been validated as an effective practical detection tool for Al³⁺ions, which can detect Al³⁺ ions in actual samples through fluorescence spectroscopy, achieve on-site detection by smartphone, and image intracellular Al³⁺ ions by bioimaging.