A Squaraine-Based Colorimetric and Turn on Fluorescent Sensor for Selective Detection of Hg2+ in an Aqueous Medium

A novel squaraine-based chemosensor SQ-1 has been synthesized, and its sensing behavior toward various metal ions was investigated by UV- vis and fluorescence spectroscopies. In AcOH-H2O (40:60, v/v) solution, Hg2+ ions coordinate with SQ-1 causing a deaggregation which induces a visual color and absorption spectral changes as well as strong fluorescence. In contrast, the addition of other metals (e.g., Pb2+, Cd2+, Cu2+, Zn2+, Al3+, Ni2+, Co2+, Fe3+, Ca2+, K+, Mg2+, Na+, and Ag+) does not induce these changes at all. Thus SQ-1 is a specific Hg2+ sensing agent due to the inducing deaggregation of the dye molecule by Hg2+.