Naphthalimide-benzimidazole conjugate for the light-up fluorescence detection of Ga3+ and DCP

Abstract

Gallium ions (Ga³⁺) play a crucial role in human life due to their remarkable physical, chemical, and biological properties, with applications ranging from electronic devices and solar cells to anticancer therapeutics, owing to their strong affinity for tumor tissues. However, increasing industrial and biomedical use has led to environmental accumulation, making Ga³⁺ exposure a concern. In this work, we report a novel naphthalimide-based reversible chelating ligand (NaHB) capable of selectively recognizing both Ga³⁺ ions and the nerve agent diethyl chlorophosphate (DCP) in a CH₃CN/H₂O medium. The binding interactions were systematically studied using UV–Vis absorption, fluorescence spectroscopy, NMR, and high-resolution mass spectrometry. NaHB displays an instantaneous “switch-on” fluorescence response toward Ga³⁺ and DCP, with binding constants (Kₐ) of 5.15 × 104 M-1 and 1.2 × 105 M-1, respectively. Job’s plot analysis confirmed a 1:1 stoichiometry for both systems. The practical utility of NaHB was demonstrated through paper strip assays and quantitative detection of Ga³⁺ and DCP in real-field water samples. Furthermore, the NaHB–Ga³⁺ complex was explored for molecular logic gate applications, showcasing its multifunctional sensing capability.