Cysteine-Protected Antibacterial Spheroids of Atomically Precise Copper Clusters for Direct and Affordable Arsenic Detection from Drinking Water

Rapid and naked-eye detection of water-borne contaminants using molecularly precise nanomaterials has emerged as a promising strategy to reduce the impact of chemical pollution. This study presents a luminescence-based arsenic (As) sensor, eliminating the need for sample preparation. Incorporating red-emitting spheroidal cluster-assembled superstructures (CASs), comprised of Cu₁₇ nanoclusters (Cu₁₇NCs), coprotected by l-cysteine (l-Cys) and 1,2-bis(diphenylphosphino) ethane (DPPE) ligands, the sensor exhibits notable sensitivity toward arsenite (As³⁺) and (As⁵⁺) ions. A detection limit of 1 ppb in tap water was achieved through luminescence-based quenching. Remarkably, it demonstrates selective detection of As amidst common interfering metal ions such as Cd²⁺, Hg²⁺, Fe³⁺, Pb²⁺, Cu²⁺, and Cr³⁺. A sensor disc made of CASs coated on nonwoven polypropylene (PP) mats has been devised for practical field applications. Electron microscopy reveals disrupted morphology of the spheroids due to As interaction. Moreover, the CASs exhibit significant antibacterial efficacy against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus and antibiofilm properties against Bacillus subtilis. This research highlights the effectiveness of atomically precise clusters for a practical application with direct societal relevance.