Dispersing hydrophobic copper nanoclusters in aqueous solutions triggered by polyoxometalate with aggregation-induced eimission properties

Copper nanoclusters (Cu-NCs), as a luminescent material, have received widespread attention due to their low cost, non-toxicity and excellent biocompatibility. However, research on the preparation of stable dispersions containing hydrophobic Cu-NCs are rare because of its difficulty to achieve. In this work, by the help of polyoxometalates (Na9[EuW10O36]·32 H2O, EuW10), atomically precise Cu-NCs (Cu4I4 clusters, the ligand is triphenylphosphine (PPh3)) was successfully introduced into water in the presence of co-solvent (dimethylsulfoxide, DMSO) to form stable dispersions. This strategy makes the dispersions to achieve aggregation-induced luminescence (AIE) with a high absolute quantum yield of 19.34 % and also greatly improve the stability of the hydrophobic Cu4I4 clusters in the water system. One reason is that the copperophilic interaction between Cu4I4 clusters leads to the high compactness of the assembly and suppresses the intramolecular vibrations and rotations of the Cu4I4 clusters ligands which induced the AIE phenomenon; another reason is that the hydrophobic interaction between the hydrophobic part of EuW10 and the peripheral ligands of Cu4I4 clusters and the solvation of EuW10 with the mixed solvent make the Cu4I4 clusters disperse stably in the mixed system. Furthermore, Cu4I4 clusters/EuW10 stable dispersions can be used for Fe3+ sensing. The results indicated that the dispersion has good recognition ability, and high selectivity with a low detection limit of 40.34 nM for Fe3+. Our strategy of combining polyoxometalates with hydrophobic Cu-NCs to construct AIE systems in mixed solvents is expected to provide new insights into the development of biological probe, bioimaging, catalytic and sensitive sensors for environmental applications such as metal ion detection.