A novel ratiometric fluorescence and colorimetric probe with a large stokes shift for Hg2+ sensing

A novel ratiometric fluorescence and colorimetric probe (BDT-PBES) based on benzo[1,2-b:4,5-b’]dithiophene (BDT) unit, for the detection of Hg2+, was developed with dithioacetal group as the response unit. Based on the Hg2+-promoted dithioacetal deprotection reaction mechanism, the probe displayed high selectivity for Hg2+ over other ions including Co2+, Mn2+, Zn2+, Ag+, Cd2+, Pb2+, Ca2+, Al3+, Cr3+, Na+, Cu2+, Mg2+, Ni2+, K+, Fe2+, Pd2+ and Fe3+. The detection limit reached as low as 3.1 × 10–7 M. When Hg2+ existed, the maximum absorption peaks were obviously red-shifted with a solution color change from clarifying to light yellow, and the fluorescence changed with a large Stokes shift (179 nm) from blue-green to yellow.