A reversible fluorescent chemosensor based on a naphthalene dyad for Pb (II) ions: Applications in food, water, and bio-imaging

Lead (Pb2+) ions, among heavy toxic metals, are extensively distributed and bioaccumulate in food chains, prompting researchers to monitor their levels in water and biosystems. Consequently, aiming to protect the environment and human health, this study synthesizes a straightforward naphthalene-naphthalene dyad-based "turn-on" fluorescent chemosensor (S) tailored for detecting Pb2+ ions. This selective response to Pb2+ ions over other competing metal ions is characterized by hypsochromic changes in fluorescence enhancement resulting from an intramolecular charge transfer (ICT) process from -OH group (donor) to the naphthyl ring (acceptor) following the complexation of S-Pb2+. Moreover, cross -contamination titration for probe S was conducted in the presence of various distinct competitive metal ions. By employing Job's plot and B -H plot, the complicated stoichiometry (1:2) and association constant (Ka = 9.45x104 M-1) of S-Pb2+ were studied. The probe's interaction with Pb2+ is studied using spectroscopic measurements and DFT calculations. The probe demonstrated exceptional selectivity and sensitivity, achieving a limit of detection (LOD) value of 12.50x10- 6 M for Pb2+ in a buffered THF:H2O (50:50, v:v) medium. The applicability of chemosensor S spans across various water, food, and E. coli samples, indicating its potential in monitoring and managing Pb2+ toxicity in wastewater and biosystems.