A highly efficient, selective, reversible and ultra-sensitive fluorescence "Turn-ON" chemosensor for aluminium ions...

The synthesis of a Schiff base-based chemosensor, denoted as H₆L, was accomplished through the condensation reaction of Isophthalohydrazide and 2,6-dihydroxybenzaldehyde in an ethanol solvent. The resulting compound was further characterized using ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy, as well as high-resolution mass spectrometry (HRMS). Extensive research has been conducted on several facets of metal sensing phenomena, revealing that the Schiff base H₆L demonstrates discerning and expeditious fluorescence sensing characteristics specifically towards Al (III) in acetonitrile. The purported method detects Al (III) can be ascribed to the suppression of photo-induced electron transfer (PET) and the enhanced chelation-induced fluorescence (CHEF). The stoichiometry of metal-ligand complexes (2:1) was determined using Job's plots titrations, HRMS and subsequently confirmed using NMR titration studies. The H₆L sensors demonstrated remarkable fluorescence sensing capabilities in acetonitrile, with a low detection limit (LOD) of 0.44 μM. This LOD is suitably low for the detection of Al³⁺, which is commonly found in many environmental and biological systems. Fluorescence lifetime measurement provides additional evidence of complexation of H₆L with Al (III). The reversibility of the sensor was demonstrated through the introduction of pyrophosphate (PPi), which forms a complex with aluminium ions, thereby releasing the chemo sensor for subsequent utilization. The findings suggest that H₆L has the potential to serve as a viable probe for the detection and identification of Al³⁺ ions.