Synthesis of metal nanoclusters and their application in Hg2+ ions detection: A review

Mercuric (Hg2+) ions released from human activities, natural phenomena, and industrial sources are regarded as the global pollutant of world's water. Hg2+ ions contaminated water has several adverse effects on human health and the environment even at low concentrations. Therefore, rapid and cost-effective method is urgently required for the detection of Hg2+ ions in water. Although, the current analytical methods applied for the detection of Hg2+ ions provide low detection limit, they are time consuming, require expensive equipment, and are not suitable for in-situ analysis. Metal nanoclusters (MNCs) consisting of several to ten metal atoms are important transition missing between single atoms and plasmonic metal nanoparticles. In addition, sub-nanometer sized MNCs possess unique electronic structures and the subsequent unusual optical, physical, and chemical properties. Because of these novel properties, MNCs as a promising material have attracted considerable attention for the construction of selective and sensitive sensors to monitor water quality. Hence this review is focused on recent advances on synthesis strategies, and optical and chemical properties of various MNCs including their applications to develop optical assay for Hg2+ ions in aqueous solutions.