Highly sensitive and selective fluorescence-based sensing of metal ions using a novel Schiff base chemosensor

Heavy metal ions like Fe3+ and Hg2+ present unique health and environmental concerns. While Fe3+ is essential for bodily functions, excessive levels can lead to oxidative stress and damage due to its role in producing reactive oxygen species. In contrast, Hg2+ is toxic even at low concentrations, affecting the central nervous system and accumulating in the food chain, making it a serious environmental pollutant. Thus, developing sensitive detection methods for these metals is crucial for monitoring their levels and mitigating their impacts on health and ecosystems. In this work, a novel fluorescence ‘turn-on’ chemosensor AS1 based on a Schiff base has been synthesised and thoroughly characterised by FT-IR and 1H NMR spectroscopy. The designed chemosensor was applied for simultaneous detection of Fe3+ and Hg2+ ions in MeOH – H2O (v/v 4:96) system. This chemosensor demonstrates exceptional fluorescent sensing capabilities with notable selectivity for Fe3+ and Hg2+ ions over other metal ions. Upon interaction Fe3+ or Hg2+ ions, the sensor exhibits a significant fluorescence enhancement. This fluorescence enhancement was due formation of complexes (AS1-Fe3+ and AS1-Hg2+). The chemosensor showed high sensitivity with a detection limit of 0.0031ppm (0.056 µM) for Fe3+ and 0.014 ppm (0.07 µM) for Hg2+. The chemosensor developed for detecting Fe3+ and Hg2+ has been successfully applied to real water samples. The observed percent recovery values for Fe3+ ranged from 90.0 ± 0.25% to 103.3 ± 0.36%, while for Hg2+ they ranged from 86.0 ± 0.60% to 102.6 ± 0.43%, showing its practical utility in environmental monitoring.