Dansyl-appended sequence-defined oligomers for selective ultrasensitive detection of Hg2+ in water, paper strips, living cells and its efficient removal

Abstract

The design and synthesis of dansyl-appended fluorescent sequence-defined oligomers (SDOs) for the selective detection of toxic Hg2+ ions in water is reported. The system incorporates dithiocarbamate (DTC) to act as the binding unit and hydroxy group at the terminal site to improve water solubility. The sensor exhibited positive solvatochromism. This platform has the advantage of systematically increasing the number of DTC units to improve the sensitivity and in doing so, a 100-fold enhancement in sensitivity was obtained by increasing the number of DTC from one to two. A very low detection limit of 60 pM was achieved with the two DTC system and this platform has scope to improve LOD further. Moreover, visual detection and fabrication of paper strip for easy detection of Hg2+ ions are also possible. The sensor selectively binds to Hg2+ ions even in presence of competitive ions and was applied for detection of Hg2+ contamination in lake and tap water samples. Further, we successfully used our sensor for cell imaging in MCF-7 and HeLa cancer cell lines and detect Hg2+ using fluorescence microscopy. The same system was also capable of removing Hg2+ ions from water with an efficiency > 95%.