Innovative molecular architecture of a new Hg²⁺/Cu²⁺-dual chemosensor based on functionalizable chromenylium-cyanine framework

A novel chromenylium-cyanine based near-infrared (NIR) and dual chemosensor (NIR9) has been developed for the highly sensitive and selective detection of mercury (Hg²⁺) and copper (Cu²⁺) ions. The NIR9 is the first example of NIR probes developed for independently analysis of Hg²⁺ and Cu²⁺ in real samples. The probe exhibits turn-on fluorescence and ratiometric UV–Vis absorption and colorimetric responses for Hg²⁺. It also displays a turn-off UV–Vis absorption signal to Cu²⁺. Upon interaction with Hg²⁺, NIR9 undergoes a desulfurization-induced spirolactam ring opening, resulting in a strong fluorescence emission at 750 nm and a visible color change from yellow to green, with a detection limit as low as 0.02 μM. For Cu²⁺ detection, the probe shows a unique absorbance decrease at 380 nm, enabling quantification with a detection limit of 0.01 μM. The sensing capability of NIR9 is supported by theoretical DFT studies and further validated through successful applications in real environmental (water and food) and biological (A549 cells) samples. Additionally, the probe enables smartphone-assisted detection of Hg²⁺, promoting field-deployable analytical capabilities. This work introduces a next-generation multiplexed NIR chemosensor with high versatility, selectivity, and sensitivity for environmental and biomedical applications.