Colorimetric detection of trace Hg2+ with near-infrared absorbing squaraine functionalized by dibenzo-18-crown-6 and its mechanism

Abstract In this contribution, an improved near-infrared absorbing colorimetric detection of Hg 2+ ion with high selectivity and sensitivity had been developed by using bis-dibenzo-18-crown-6-based squaraine ( BCSQ ) as sensor in aqueous media. The proposed method was applied to analyze trace Hg 2+ in synthetic Hg 2+ samples and natural Hg 2+ samples. Under the optimum conditions, the detection had a linear range of 7.5–150 × 10 −8  mol L −1 with a correlation coefficient ( R ) of 0.9983 combining a limit detection (3 σ , n  = 20) of 5.6 × 10 −9  mol L −1 . The relative standard deviation (RSD) was lower than 2.4% ( n  = 5). The proposed method possesses the advantages of simplicity, rapidity, high selectivity and sensitivity. The action mechanism between BCSQ and Hg 2+ was discussed in details.