A Bisphenol A-Based Chemosensor for Potent Sensing of Al³⁺ and Its Application in Real Sample Analysis

Development of fluorescent chemosensors for Al³⁺ is one of the important research areas as the presence of the cation is responsible for many health issues. The study presents the development and analysis of a novel Al³⁺ detecting compound, 4-(2-(4-hydroxy-3-((quinolin-3-ylimino)methyl)phenyl)propan-2-yl)-2-((quinolin-3-ylimino)methyl)phenol (abbreviated as H₂P). The probe was obtained by a simple condensation of bisphenol A dialdehyde and 3-amino quinoline (1:2 ratio) in methanol under mild conditions. A distinct color change was observed in the bare eye under UV light in the presence of Al³⁺, whereas other metal ions remained unresponsive. The fluorescence probe demonstrates a remarkable enhancement in fluorescence intensity, specifically a 29-fold increase at 466 nm, when exposed to Al³⁺. This phenomenon has been attributed to two mechanisms: the chelation enhanced fluorescence (CHEF) effect and the inhibition of C=N isomerization. The probe exhibits high sensitivity toward Al³⁺, with a detection limit of 1.48 × 10^-7 M. Furthermore, it forms a complex with the cation in a 1:2 ratio (ligand to metal), characterized by an association constant of 3.30 × 10⁴ M^-1. The application of H₂P demonstrated efficacy in detecting Al³⁺ within water samples.