Small-molecule-based fluorescent probes for f-block metal ions: A new frontier in chemosensors

F-block elements, consisting of lanthanides and actinides, play indispensable roles in various important fields, which have been receiving significant attention over a long period of time. Despite the numerous benefits that f-block elements afford, high intake or long-term contact of these two-row metal ions can result in severely adverse effect and irreversible damage to human health owing to their high toxicity and/or strong radiotoxicity, which are strictly defined the concentration limits in drinking water. Consequently, selective detection and determination of f-block cations become imperative necessity. Nevertheless, it is extremely difficult to recognize specific f-block metal ion from the bulky series due to the pronounced similarity in physical and chemical properties of the two-row cations derived from lanthanide contraction. Compared to traditional techniques, fluorescent chemosensors have distinct advantages, indicative of low cost and local observation, high selectivity and sensitivity, real-time visualization and in vivo bioimaging analysis. In this review, the progress made so far of fluorescent chemosensors for f-block metal ions is systematically summarized, which represents the first comprehensive summary describing fluorescent probes for selective recognition and detection of these two-row metal ion series. This review only focuses on the small-molecule-based fluorescent chemosensors, particularly the synthetic organic molecules, rather than polymers, biosensors and nanoparticle-based sensors. The molecular structures, sensing mechanisms and their applications of these fluorescent probes are discussed in detail. The prospects and challenges of fluorescent chemosensors related to this topic are also provided. (C) 2020 Elsevier B.V. All rights reserved.