Small molecular fluorescent probes for the detection of lead, cadmium and mercury ions

Heavy-metal pollution, especially Hg2+, Pb2+ and Cd2+, have become a serious issue worldwide. Exposure to even very low concentrations of these metals will threaten human health and cause various illness. More seriously, these metals could not be biodegraded, and would gradually accumulate in environment as well as living organism. The development of rapid, accurate and economic methods to detect them is significant important to reduce or avoid exposure to these metals. Consequently, much effort has been dedicated to design and synthesize fluorescent probes that can selectively detect Hg2+, Pb2+ and Cd2+. Herein, we summarized recent small molecular fluorescent probes for these metals. To be helpful for rational design, these probes are divided into three types according to response modes (turn-off, turn-on, ratiometric probes) and are further subdivided according to sensing mechanism (PET, ICT, AIE and others). Especially, reaction-based probes are listed separately because of its good selectivity.