Recent advances in the application of copper nanocluster and copper nanoparticle in water for heavy metals detection: A review

Heavy metals (HMs) are a threat to ecology and human health. HMs, present even in a trace amount, are often carcinogenic creating an alarming threat to civilization. Consequently, selective and sensitive detection of HMs is a crying need. Copper, being a group 11 3d transition metal, is inexpensive with a strong surface plasmon band in the nano regime and intriguing fluorescence in the cluster regime. Copper particles, though cost-effective, are usually vulnerable to aerial oxidation. By different capping agents/stabilizing agents, copper particles are stabilized. With this idea in mind, we reviewed the sensing of HMs using copper nanoparticles (PNCus) and copper nanoclusters (CCus). Fluorometric and colorimetric detection techniques are illustrated in detail here. Fluorometric sensing was quenching-based and no enhancement-based sensing is available, to the best of our knowledge. CCus are usually employed for fluorometric detection while PNCus are mostly used to detect calorimetrically. In addition to it, we included mechanistic ground of sensing, the fate of sensing platform & analytes, spot analyses, and natural sample analyses along with basic knowledge of nanoparticles & nanoclusters and toxicity of heavy metals.