Construction of a novel ESIPT and AIE-based fluorescent sensor for sequentially detecting Cu and HS in both living cells and zebrafish.

The development of effective methods for tracking Cu and HS in living organisms is urgently required due to their vital function in a variety of pathophysiological processes. In this work, a new fluorescent sensor BDF with excited-state intramolecular proton transfer (ESIPT) and aggregation-induced emission (AIE) features for the successive detection of Cu and HS was constructed by introducing 3,5-bis(trifluoromethyl)phenylacetonitrile into the benzothiazole skeleton. BDF showed a fast, selective and sensitive fluorescence "turn off" response to Cu in physiological media, and the situ-formed complex can serve as a fluorescence "turn on" sensor for highly selective detection of HS through the Cu displacement approach. In addition, the detection limits of BDF for Cu and HS were determined to be 0.05 and 1.95 μM, respectively. Encouraged by its favourable features, including strong red fluorescence from the AIE effect, large Stokes shift (285 nm), high anti-interference ability and good function at physiological pH as well as a low toxicity, BDF was successfully applied for the consequent imaging of Cu and HS in both living cells and zebrafish, making it an ideal candidate for detecting and imaging of Cu and HS in live systems.