Recent Advances in Near-Infrared Fluorescent Probes Based on Organic Small Molecules for the Detection and Imaging of Heavy Metal Ions

Heavy metal pollution poses a severe threat to ecosystems and human health. Therefore, it is important to develop rapid, sensitive, and reliable detection methods. Fluorescent probes with near-infrared (NIR, 650–900 nm) emission have emerged as powerful analytical tools owing to their distinct advantages, including low background interference, deep-tissue penetration, minimal photodamage, and high signal-to-noise ratios, which make them particularly attractive for both environmental monitoring and bioimaging applications. This review systematically summarizes recent progress in NIR organic small-molecule fluorescent probes for the detection of heavy metal ions, covering the period from 2022. Representative examples are categorized and discussed, with a focus on key metal ions such as Cu2+, Hg2+, Cd2+, Zn2+, Pb2+, Fe2+ and Fe3+. The molecular design strategies, sensing performance, and practical applications in environmental samples, food samples and biological imaging are critically discussed. Furthermore, current challenges and future opportunities in this rapidly advancing field are highlighted.