An effective fluoroquinolone-based fluorescent probe for ultrasensitive Zn2+ detection exhibiting "turn-on" fluorescence.

Contamination of water and soil by heavy metal ions is a major global concern because these ions are toxic and persist in the environment for long periods. A new, effective fluorescent sensor based on a fluoroquinolone was developed for detecting zinc ions (Zn2+) with a turn-on signal. When Zn2+ ions are gradually added to the fluoroquinolone solution, the fluorescence intensity increases due to an internal charge transfer mechanism. We evaluated the detection of Zn2+ ions using the fluorescence probe in various solvents and across different pH conditions. The key results showed that the fluorescent probe demonstrated a strong preference for detecting Zn2+ ions in ethanol, maintaining accuracy despite the presence of other metal ions, and exhibited enhanced sensitivity. The developed sensor achieved a remarkably low detection limit of 1 nM for Zn2+ ions, outperforming earlier reported sensors. Fluorescence measurements exhibited a consistent linear correlation for Zn2+ concentrations between 1 nM and 15 µM. Furthermore, spectrophotometric data showed increased absorbance peaks upon addition of Zn2+ to the fluoroquinolone solution, confirming the creation of a fluoroquinolone-Zn2+ complex. The suggested probe was successfully applied to detect Zn2+ ions in wastewater and drinking water samples, achieving recovery rates ranging from 97.0% to 102.75%. More interestingly, binding to Zn2+ leads to significant changes in the fluorescence lifetime of the proposed probe, which can be used to visualize Zn2+ ions in A549 cells via Confocal fluorescence microscopy. The reported chemosensor with fluoroquinolone is an effective and economical system for real-time monitoring of Zn2+ ions.