A review: Red/near-infrared (NIR) fluorescent probes based on nucleophilic reactions of H2 S since 2015.

The topics of human health and disease are always the focus of much attention. Hydrogen sulfide (H2 S), as a double-edged sword, plays an important role in biological systems. Studies have revealed that endogenous H2 S is important to maintain normal physiological functions. Conversely, abnormal levels of H2 S may contribute to various diseases. Due to the importance of H2 S in physiology and pathology, research into the effects of H2 S has been active in recent years. Fluorescent probes with red/near-infrared (NIR) emissions (620-900 nm) are more suitable for imaging applications in vivo, because of their negligible photodamage, deep tissue penetration, and maximum lack of interference from background autofluorescence. H2 S, an 'evil and positive' molecule, is not only toxic, but also produces significant effects; a 'greedy' molecule, is not only a strong nucleophile under physiological conditions, but also undergoes a continuous double nucleophilic reaction. Therefore, in this tutorial review, we will highlight recent advances made since 2015 in the development and application of red/NIR fluorescent probes based on nucleophilic reactions of H2 S.