Dual Sensing Performance of 1,2-Squaraine for the Colorimetric Detection of Fe3+ and Hg2+ Ions.

A simple 1,2-squaraine based chemosensor material (SQ) has been reported to show dual sensing performance for colorimetric detection of Fe3+ and Hg2+ ions. Compared to common instrumental analysis, this method could provide fast and direct detection though colorimetric changes by the naked eye. The sensor has shown excellent selectivity over the other metal ions by tuning different solvent environments. The detection limit for Fe3+ could reach to 0.538 μM, which was lower than that in the environmental agency guideline (U.S. Environmental Protection Agency, U.S. EPA) in drinking water. And for Hg2+ detection, the limit was calculated as 1.689 μM in our case. A 1:1 binding mode between SQ⁻Fe3+ and SQ⁻Hg2+ ion were evidenced by Job's plot measurement and IR analysis. The proposed different binding mechanisms were also supported by Density Function Theory (DFT) calculation. All these findings provide a unique material and a simple, facile, and low cost colorimetric method for dual metal ions analysis and have shown preliminary analytical applications in industrial water sample analysis.