Small molecular N-heteroaromatics-based optical sensing of noxious Hg2+ ion: A comprehensive insight into recent advancements, existing challenges, and future perspective

The surrounding ecology and extant mammalian health recognize that the Hg2+ ions are very toxic and can damage the ecosystem even at a trace concentration level. Mercury exposure creates severe adverse effects on human health related to the respiratory system, central nervous system (CNS), skin damage, kidney failure, and various mental disorders. Therefore, detection and estimation of Hg2+ ions by alternative up-to-date techniques are more crucial than traditional methods, which require expensive and skilled personnel. Due to their high sensitivity and selectivity, optical sensors draw much attention for the sensitive and selective detection of various toxic environmental species. Recently, small molecular probes with N-heterocyclic fluorophoric receptors have successfully been utilized in different sensing arenas due to their cost-effective synthesis and commendable photophysical activities. For the last fifteen years, numerous research groups have reported N-heterocyclic-based receptors for Hg2+ ion sensing in solution and solid-state with a selective sensitivity, reversibility, and low limit of detection, accompanying several real-world applications. This review article aims to provide current progress and future viewpoints in N-heteroaromatic-based colorimetric and/or fluorogenic Hg2+ ion sensors with wide real-time applications.