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 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 (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 Hg(2+) was discussed in details.