A Dual-Target Fluorescent Chemosensor Based on Naphthalene Oxa-Aza Receptor for Zn²⁺ and Tyrosine Detection

In this study, a new dialdehyde was synthesized, followed by the successful preparation of a novel naphthalene-based oxa-aza receptor (L). The receptor was structurally characterized using a comprehensive suite of spectroscopic techniques, including UV-Vis, fluorescence, IR, ¹H NMR, ¹³C NMR, DEPT, HSQC, and mass spectrometry. The chemosensor demonstrated high selectivity and sensitivity toward Zn²⁺ ions and the amino acid tyrosine. Fluorescence titration revealed a marked enhancement in emission intensity upon Zn²⁺ coordination, with a 1:1 binding stoichiometry confirmed by Job's plot and an association constant (K_a) determined via the Benesi-Hildebrand method. The detection limit for Zn²⁺ was calculated to be 1.86 × 10⁻⁸ M. Additionally, the chemosensor exhibited strong affinity for tyrosine, achieving a detection limit of 2.8 × 10⁻⁸ M. Fluorescence reversibility studies highlighted the excellent regeneration capability of the chemosensor, underscoring its potential as a reusable probe for biological and environmental monitoring applications.