Luminescent Hydrogel Based on Silver Nanocluster/Malic Acid and Its Composite Film for Highly Sensitive Detection of Fe3+

Metal nanoclusters (NCs) with excellent photoluminescence properties are an emerging functional material that have rich physical and chemical properties and broad application prospects. However, it is a challenging problem to construct such materials into complex ordered aggregates and cause aggregation-induced emission (AIE). In this article, we use the supramolecular self-assembly strategy to regulate a water-soluble, atomically precise Ag NCs (NH4)(9)[Ag-9(C7H4SO2)(9)] (Ag-9-NCs, [Ag-9(mba)(9)], H(2)mba = 2-mercaptobenzoic acid) and L-malic acid (L-MA) to form a phosphorescent hydrogel with stable and bright luminescence, which is ascribed to AIE phenomenon. In this process, the AIE of Ag-9-NCs could be attributed to the non-covalent interactions between L-MA and Ag-9-NCs, which restrict the intramolecular vibration and rotation of ligands on the periphery of Ag-9-NCs, thus inhibiting the ligand-related, non-radiative excited state relaxation and promoting radiation energy transfer. In addition, the fluorescent Ag-9-NCs/L-MA xerogel was introduced into polymethylmethacrylate (PMMA) to form an excellently fluorescent film for sensing of Fe3+. Ag-9-NCs/L-MA/PMMA film exhibits an excellent ability to recognize Fe3+ ion with high selectivity and a low detection limit of 0.3 mu M. This research enriches self-assembly system for enhancing the AIE of metal NCs, and the prepared hybrid films will become good candidates for optical materials.