The active sulfur small molecules such as biothiols, hydrogen sulfide, hydrogen polysulfides and sulfur dioxide are closely related to various diseases in the biological system and have important physiological and pathological functions. Small-molecule fluorescent probes enable to detect and image active sulfur small molecules by virtue of their non-invasiveness, fast response times, and real-time in situ detection capability. Based on the inherent characteristics of active sulfur small molecules, many fluorescent probes have been reported to detect and image them. In this review, we classify the fluorescent probes according to the different type reaction of each small molecule, and summarize the reaction mechanism in detail. Moreover, we also emphasize the challenges of active sulfur small molecules-responsive fluorescent probes, hoping to provide a general implication for future research.
