A Selective Colorimetric and Turn-on Fluorescent Chemosensor for Hg2+ in Aqueous Solution

A simple colorimetric and turn-on fluorescence receptor FT (thiophene appended fluorescein-hydrazone derivative) was prepared and its cation-sensing properties were investigated. Receptor FT displayed a selective colorimetric change (from colorless to orange color) upon binding to Hg2+ in DMSO/H2O (1:9, v/v) solution. The association constant of FT-Hg2+ complex was calculated to be 3.03 × 109 M−1, and the detection limit for Hg2+ was found to be 0.24 ppm.