The rational design of effective tools capable of monitoring hydrogen sulfide (H2S) is of great

importance to fully understand its physiological and pathological functions. Herein, a self-assembled fluorescent nanoprobe with both aggregation-induced emission (AIE) and excited-state intramolecular proton transfer (ESIPT) characteristics for H2S detection has been successfully developed via a modified nanoprecipitation method. The nanoprobe features high water dispersibility, a large Stokes shift (ca. 100 nm), good biocompatibility as well as high selectivity towards H2S over other putative interferents. Live cell imaging experiments demonstrate that the nanoprobe, with good cell-membrane permeability, can facilitate the visualization of exogenous and endogenous H2S levels. Moreover, the nanoprobe has also been found capable of detecting H2S in zebrafish. This nanoprobe with AIE and ESIPT characteristics can provide a novel method for the development of fluorescent probes for monitoring biological processes.