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

In this contribution, an improved near-infrared absorbing colorimetric detection of Hg2+ 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 Hg2+ in synthetic Hg2+ samples and natural Hg2+ 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 (3σ, 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 Hg2+ was discussed in details.

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► A NIR colorimetric detection for trace Hg2+ with dibenzo-18-crown-6-based squaraine.
► The interaction between Hg2+ and BCSQ is exclusive.
► The reaction mechanism is confirmed by means of experimental and theoretical proofs.
► An effective NIR colorimetric recognition to Hg2+ is developed.