A dual-responsive ratiometric fluorescent probe for the detection of hypochlorite and hydrazine in environmental samples, live cells, and plant tissues

Hypochlorite (ClO^-), a potent oxidizer and disinfectant, and hydrazine, a powerful reducing agent, are widely used in daily life and various industries. However, their extensive use comes with significant risks, as they are highly toxic to both the environment and human health. They have been associated with various health issues and even linked to cancer. Therefore, the simultaneous detection of hypochlorite and hydrazine is crucial for assessing their impact and monitoring the onset and progression of related diseases. A phenanthroimidazole-indandione based colorimetric and ratiometric fluorescent probe PIID was designed and synthesized for dual channel detection of hypochlorite and hydrazine in environmental and biological samples. Probe PIID, which showed a strong yellow-orange emission at 640 nm with a massive Stokes shift of 220 nm, exhibited excellent fluorescence change from yellow-orange to green (526 nm) in the presence of ClO^- and from yellow-orange to blue (424 nm) in the presence of hydrazine in an aqueous-THF solvent system. A strong ICT effect, which was acting in probe PIID, gets weakened through ClO^- - mediated cleavage of the CC bridge bond to produce aldehyde PIB with a blue shift of 114 nm and hydrazine-induced hydrazinolysis of the indanedione moiety to form hydrazone compound PIBH with a blue shift of 216 nm and that was also confirmed by DFT studies. Not only that, the probe exhibits excellent selectivity over other ROS (reactive oxygen species) and amines with a very fast response time of 40 seconds for hypochlorite and 90 seconds for hydrazine, and high sensitivity was observed with detection limits of 32.75 nM for hypochlorite and 92 nM for hydrazine. Moreover, PIID was employed to monitor both the analytes successfully in environmental water samples and in a solid-state TLC strip study. Hypochlorite was monitored in commercial disinfectants, and by exogenous bioimaging in human breast cancer cells (MDA-MB 231) and endogenous bioimaging in RAW 264.7 macrophage cells with very low cytotoxicity and good cell viability. Meanwhile, hydrazine was tracked in soil samples, and confocal imaging was performed on onion tissue.