Flavonol-based small-molecule fluorescent probes

Flavonols, named as 3-hydroxyl-2-phenyl-1-benzopyran-4-one, are important natural botanical functional pigments widely distributing in fruits, vegetables, and flowers. Owing to intramolecular hydrogen bond, the flavonols can undergo the excited-state intramolecular proton transfer (ESIPT) process upon irradiation, leading to unique environmental-sensitive dual emissions, which makes flavonol an ideal fluorophore skeleton for probe design. In this paper, we summarized the recent progress of flavonol-based small-molecule fluorescent probes for diverse sensing applications, including detection of anions, cations, reactive biological species, proteins, DNAs, environmental hazards, and microenvironmental factors. This review highlighted the basic characteristics of flavonol probes in the respect of design principles, photophysical processes, sensing mechanism, sensing performances, and biological applications. The present review article aims to offer a comprehensive summary for researchers to inspire new probe design, and push forward the advancement of flavonol-based fluorescent probes.