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 x 10(-8) mol L-1 with a correlation coefficient (R) of 0.9983 combining a limit detection (3 sigma, n = 20) of 5.6 x 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. (C) 2012 Elsevier B.V. All rights reserved.