Ethanol and Gd3+ activated aggregation induced delayed fluorescence in copper nanoclusters for detection of Cr(VI)

In recent years, significant emphasis has been dedicated towards investigating aggregation-induced emission (AIE) phenomena, and a notable addition to this emerging field is aggregation-induced delayed fluorescence (AIDF). Here, we proposed two different strategies to produce AIDF-based luminescent materials at room temperature from glutathione-capped CuNCs (GSH-CuNCs) by (1) simply modifying the solvent environment and (2) introducing gadolinium (Gd) ions. The synthesized GSH-CuNCs displayed weak fluorescence (Fl) emission in aqueous solution with a short delayed lifetime of 3.2 μs and quantum yield (QY) of only 1.42 %. However, introducing GSH-CuNCs to an ethanol medium promptly led to enhanced delayed Fl emission with a significantly delayed lifetime of 21.8 μs and a high QY of 89.2 %. Moreover, introducing Gd ions to the aqueous GSH-CuNC solution also enhances delayed Fl emission with a delayed lifetime of 13.6 μs and a high QY of 79.5 %. Analysis of transmission electron microscopy and dynamic light scattering data showed that both the ethanol medium and Gd addition endows controlled aggregation of GSH-CuNCs, enabling successful harvesting of triplet states and ultimately leading to the AIDF phenomenon. Moreover, the AIDF harnessed from GSH-CuNCs by Gd was successfully employed to detect Cr ions in an aqueous solution with excellent selectivity.