Recent progress in the development of organic small-molecule and functional material fluorescent probes for formaldehyde detection and imaging

•The progress of fluorescent probes for sensing and imaging FA is summarized.•Both organic small-molecule-based and functional material-based probes are presented.•Structures, spectral properties, and recognition mechanisms of probes are outlined.•The challenges and future opportunities for designing novel FA probes are discussed. Formaldehyde (FA) is one of the most important reactive carbonyl species. It is not only exogenously generated from the environment but also continuously produced in most organisms. Low concentrations of FA take part in several important physiological processes, while elevated levels of FA are associated with different kinds of diseases. Fluorescent probes have emerged as promising chemical tools for FA detection and real-time visualization in food, air, and living organisms, etc., enabling the discovery of the diverse functions of FA in physiology and pathology processes. This review will summarize recent progress in the development of FA probes, including both small-molecular organic FA probes and functional material-based probes. In addition, prospects for future design and research will be also discussed.