A dual-functional chemosensor based on acylhydrazone derivative for rapid detection of Zn(II) and Mg(II): Spectral properties,recognition mechanism and application studies

In this work, an acylhydrazone derivative (QN62) was developed via the one-step condensation of 6-hydroxy-2-naphthoic hydrazide with quinoline-8-carboxaldehyde. The structure of the QN62 compound was characterized by ¹H NMR, ¹³C NMR, HR-MS (ESI), and X-ray crystallography. As a dual-functional turn-on fluorescence chemosensor, QN62 exhibited rapid recognition for Zn²⁺ in DMSO-H₂O (4:1, v/v) and Mg²⁺ in ethanol-H₂O (9:1, v/v). The enhancement in fluorescence detection was associated with the coordination reaction between QN62 and the target ions, which promoted intramolecular charge transfer and prevented the CN isomerization process. Simultaneously, a rapid color change from colorless to yellowish-green or yellow under UV light (365 nm) was easily visible to the naked eye. Under optimal conditions, the limit of detection and limit of quantification were 32.3 nM and 97.8 nM for Zn²⁺ and 16.1 nM and 48.9 nM for Mg²⁺, respectively. The recognition mechanism was reasonably speculated based on analysis of the Job’s plot, HR-MS, ¹H NMR, and density functional theoretical calculations. Utilizing silica-gel plates fabricated from the QN62 chemosensor, the visual and rapid identification of Zn²⁺ and Mg²⁺ was successfully achieved, which could provide a convenient approach for on-site detection in environmental fields. The QN62 chemosensor could also quantify trace amounts of Zn²⁺ and Mg²⁺ in water samples. Furthermore, the cell imaging experiments indicated that QN62 could effectively sense intracellular Zn²⁺ and Mg²⁺, providing potential applications in biological systems.