Highly sensitive and selective turn-on fluorescent chemosensors for Hg²⁺ based on thioacetal modified pyrene

This work reports a facile strategy for the synthesis of water-soluble fluorescent probes Pyr1 and Pyr2, which have carboxyl and hydroxyl group in the side chain of thioacetal moiety, respectively. Pyr1-2 exhibit exclusively selective turn-on fluorescence response towards Hg²⁺ over other cations, based on intramolecular charge transfer (ICT) mechanism. Upon addition of Hg²⁺, the thioacetal moiety in Pyr1-2 can be converted to aldehyde group, which is confirmed by ¹H NMR titrations. The detection limits for Pyr1-2 are less than 1.80nM in aqueous media, lower than the maximum allowable level of Hg²⁺ in drinking water by EPA. Moreover, Pyr2 have been successfully used for fluorescence imaging of Hg²⁺ in living cells, demonstrating potential application in biological science.