Surfactant-regulated self-assembly of copper nanoclusters into high fluorescent micron-scale hexagonal plates for Fe3+ detection

Abstract

The precise synthesis and self-assembly of metal nanoclusters (NCs) featuring customized morphologies and structures, represent a crucial step in the exploration of structure-property relationships and the discovery of new functionalities. This study presents a strategy to induce the self-assembly of copper nanoclusters (Cu-NCs, Cu₄I₄(PPh₃)₄) into stable and highly fluorescent regular micron level hexagonal plates by nonionic surfactant Tyloxapol and mixed solvent (DMSO/H₂O). The aggregation-induced emission (AIE) behavior markedly enhanced the fluorescence quantum yield and lifetime of Ty-Cu-NCs, from 0.57 % and 68.6 ns to 22.60 % and 2.8 μs, representing a ∼40-fold improvement in both. Kinetic studies of the assembly process have revealed a sequence involving nucleation, aggregation, oriented growth and subsequent size enlargement. When varying the types of surfactants, the formation of Ty-Cu-NCs assembly with different morphologies was observed which indicated the unique role of Tyloxapol in directing the formation of hexagonal plates. It is noteworthy that the Ty-Cu-NCs assembly exhibits high selectivity and sensitivity towards Fe³⁺ ions, with a detection limit of 1.51 μM, which is considerably lower than the maximum permissible concentration of Fe³⁺ in tap water as per health standards. The combination of high fluorescence properties and selective ion detection capabilities renders these Ty-Cu-NCs assembly promising candidates for applications in ion sensing and anti-counterfeiting technologies.