A PEGylated colorimetric and turn-on fluorescent sensor based on BODIPY for Hg(II) detection in water

We herein reported a click strategy to fabricate two kinds of colorimetric and turn-on fluorescent dual-modal mercury sensors (PEG-DMS) based on the styryl BODIPY scaffold attached to a hydrophilic polymer PEG, where the PEG chain could effectively improve the water solubility of these two mercury sensors and mean that their Hg2+ detection could be performed in pure water, while their corresponding small molecular precursor DMS could only detect Hg2+ in the mixed medium with a large amount of organic solvent. It is interesting that PEG-DMS exhibits an excellent spectral response to Hg2+ by inhibiting the intramolecular charge transfer (ICT) effect from the Hg2+ specific ligand, dithia-dioxa-aza cyclo-pentadecane, to the BODIPY core. Upon addition of Hg2+, a significant fluorescence enhancing property in conjunction with a visible colorimetric change can be observed. These two sensors are highly selective for Hg2+ over other common cations, whereas PEG-DMS1 with one Hg2+ binding ligand exhibits higher sensitivity than PEG-DMS2 with two Hg2+ binding ligands. Additionally, the sensor could be used as a potential imaging reagent for the detection of Hg2+ uptake in HeLa cells as revealed by confocal laser scanning microscopy (CLSM).