A Fluorescent and Colorimetric Chemodosimeter for the Detection of Hg ²⁺ Ions Based on Thiadiazole Ring Formation

A thiosemicarbazide-based chemodosimeter was developed for the selective detection of Hg 2+ ions. The sensing mechanism relies on an irreversible cyclization reaction leading to the formation of a thiadiazole ring, enhancing both stability and selectivity. Upon interaction with Hg 2+, the sensor fluorescence is strongly quenched and its UV–visible absorption spectrum exhibits a red-shift, enabling sensitive dual-mode detection. The detection limits for Hg 2+ were determined to be 3.31 × 10 –5 and 6.21 × 10 –6 M using the absorption spectral changes and fluorescence analysis, respectively.