A mitochondria-targeted fluorescent probe for ratiometric detection of H ₂ S 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 <b>TD</b>'s rapid response, exceptional selectivity, and sensitivity, establish a foundation for the development of a highly sensitive and accurate analytical method for monitoring H₂S.