A review: Red/near-infrared (NIR) fluorescent probes based on nucleophilic reactions of H2S since 2015

The topics of human health and disease are always the focus of much attention. Hydrogen sulfide (H2S), as a double-edged sword, plays an important role in biological systems. Studies have revealed that endogenous H2S is important to maintain normal physiological functions. Conversely, abnormal levels of H2S may contribute to various diseases. Due to the importance of H2S in physiology and pathology, research into the effects of H2S has been active in recent years. Fluorescent probes with red/near-infrared (NIR) emissions (620-900 nm) are more suitable for imaging applicationsin vivo, because of their negligible photodamage, deep tissue penetration, and maximum lack of interference from background autofluorescence. H2S, 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 H2S.