Tetramethylolphosphonium chloride-inspired gold nanoclusters endow a heavy metal ion sensor array by pH-regulated surface ligand–metal chelation

Surface ligands are critical to the recognition capability of metal nanoclusters, making the ligand control essential for exploring their applications. In this work, we tried to develop a high-throughput heavy metal ion sensor array using surface-functionalized gold nanoclusters (AuNCs) based on pH-regulated ligand-metal chelation. In a case study, the surface tetramethylolphosphonium chloride modification of glutathione-templated AuNCs generates pH-stable multi-ligand functionalized AuNCs (THPC/GSH-AuNCs) by enhancing the rigidity of the ligand layer. The produced THPC/GSH-AuNCs are used to construct a heavy metal ion sensor array by integrating pH-regulated surface ligand-metal chelation and metal-AuNCs interaction-cased fluorescence variation. The different binding affinities between metal ions and surface ligands, as well as dramatic fluorescence modulations of metal ions on the AuNCs, enable the successful discrimination of eight heavy metal ions at a concentration of 10 μM, when linear discriminant analysis and hierarchical cluster analysis are smartly combined. In addition, a mixture of two metal ions could be distinguished with the proposed THPC/GSH-AuNCs sensor array. The practicability of this developed sensor array is validated by a high accuracy (100%) examination of 44 unknown metal samples.