Colorimetric determination of Hg2+ via thiosemicarbazide-to-oxadiazole transformation of a coumarin-benzopyrylium dye

A dual signaling reaction-based probe derived from a hybrid coumarin-benzopyrylium dye was developed for Hg²⁺ signaling. The probe exhibited selective colorimetric Hg²⁺ signaling via the Hg²⁺-induced thiosemicarbazide-oxadiazole transformation. Interference from Cu²⁺ ions was successfully circumvented using a citrate buffer as a masking agent. The detection limit for Hg²⁺ ions was found to be 1.88?×?10^–7 M. Practical application to Hg²⁺ detection in simulated wastewater was realized using a typical smartphone as a stand-alone data capture and data processing device.