A mitochondria-targeted fluorescent probe for ratiometric detection of H2S and its application in monitoring food freshness and bioimaging.

Hydrogen sulfide (H2S) is a colorless gas produced during the spoilage of sulfur-rich foods. It is also a multi-functional signaling molecule and plays an essential role in diverse physiological systems. Herein, a ratiometric fluorescent probe (TD) for monitoring H2S was rationally prepared. TD displayed red emission due to a strong intramolecular charge transfer (ICT) effect between the electron-donating phenol group and the electron-withdrawing benzoindole group. Upon reaction with H2S, the extended π-conjugation system was broken, leading to the ICT effect being turned off and causing a distinctive colorimetric and fluorometric response. Importantly, the probe-based test strip was developed for real-time monitoring of H2S generated during food spoilage, enabling on-site visualization and detection of food freshness. The practical applicability of TD to detect H2S was also evaluated in water, wine, and living cells. The results, which include TD's rapid response, exceptional selectivity, and sensitivity, establish a foundation for the development of a highly sensitive and accurate analytical method for monitoring H2S.