A bifunctional "Turn On" fluorescent probe for trace level Hg2+ and EDTA in aqueous solution via chelator promoted cation induced deaggregation signalling

Because mercury and ethylenediaminetetreaacetic acid (EDTA) are widely used materials and are commonly found together in the environment due to anthropogenic and industrial releases, there is a great need to develop a bifunctional sensor for both mercury and EDTA. A fluorescent sensor SQ-1 based on a squaraine chromophore with dithiocarbamate (DTC) side arms has been prepared, and its aggregation behavior in aqueous solution has also been investigated. The results show that increasing water concentration in the solution causes dramatic H-aggregation of the symmetric SQ-1 and consequently provides a mercury probe with a visual color change and "turn on" fluorescence via cation induced deaggregation. EDTA, a strong chelator to mercury, accelerates the deaggregation process and enhances the fluorescent emission, which not only improves the sensitivity of SQ-1 to mercury by 10-fold, with a detection limit improvement from 1.1 x 10(-7) M to 1.3 x 10(-8) M, but also provides a way for trace level detection of EDTA, with the detection limit of 8.7 x 10(-8) M. The potential application of this technique for Hg2+ and EDTA determination of river water samples is revealed by proof-of-concept experiments. (C) 2014 Elsevier B.V. All rights reserved.