A highly selective colorimetric and ratiometric fluorescent probe for instantaneous sensing of Hg2+ in water, soil and seafood and its application on test strips

Highlights: • An effective colorimetric and ratiometric fluorescent probe 3 TS is developed for naked-eye detection of Hg²⁺. • 3 TS exhibited high selectivity and excellent sensitivity for rapid detection of Hg²⁺ with a low detection limit of 10.3 nM. • 3 TS was applied to detect trace of Hg²⁺ in water, soil and seafood samples analysis as well as test strips. - Abstract: A new simple and efficient oligothiophene-based colorimetric and ratiometric fluorescent probe has been developed for highly sensitive and fast detection of Hg²⁺ in water, soil and seafood. The probe 5-(1,3-dithiolan-2-yl)-2,2':5′,2″-terthiophene 3 TS can selectively detect Hg²⁺ via the Hg²⁺-promoted deprotection reaction of thioacetals, which caused a remarkable color change from colorless to yellow and a strong fluorescence enhancement with emission color varying from blue to yellow, enabling naked-eye detection of Hg²⁺. The probe shows high sensitivity with the detection limit down to 1.03 × 10^-8 M. Visual color changes of 3 TS were observed on filter paper and TLC testing strips when they were impregnated on testing strips and immersed in Hg²⁺ solution. Moreover, the probe 3 TS has been successfully used to rapidly detect trace amounts of hazardous Hg²⁺ ions in tap, distilled, river and lake water, cropland soil, fish, shrimp and kelp samples with acceptable results and good recoveries.