Research progress of auxiliary groups in improving the performance of fluorescent probes

In the design work of fluorescent probes, it is important to consider not only the factors of fluorescence properties but also the environment in which the fluorescent molecule works. This requires the design of auxiliary groups to refine the fluorescent molecule. Nowadays, more and more fluorescent molecules are not limited to the traditional fluorescent probe consisting of a fluorophore, linker arm and recognition group, but integrate the three into one, and introduce auxiliary groups where possible. Auxiliary groups are "catalytic groups" that do not interact with the substrate, or "catalyze" the interaction of the recognition group with the substrate. The introduced auxiliary groups can improve the sensitivity and selectivity of the detection to some extent, which has attracted great interest from researchers. Although previous work has focused on this aspect, no one has summarized it systematically and comprehensively. So this review summarizes the role of auxiliary groups that are classified into three categories according to the different mechanisms between the auxiliary groups and the substance, in improving the performance of fluorescent probes in recent years (2012-2022). In particular, we generalize the mechanisms of the auxiliary groups in improving the sensitivity and selectivity of fluorescent probes. Also, the fundamental principles of auxiliary groups to improve the sensitivity and selectivity of fluorescent probes are discussed and future research directions in this field are proposed.