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 cyclopentadecane, 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).