Solvent-Induced Self-Assembly of Silver Nanoclusters for White-Light-Emitting Diodes and Temperature Sensing

Silver nanoclusters (Ag NCs), as a kind of luminescent material, have been widely studied due to their advantages of precise atomic structure, low toxicity, excellent photostability, and biocompatibility. However, studies on the preparation of hydrophilic Ag NCs with a strong fluorescence intensity and high quantum yield (QY) are rare. In this study, the atomically precise Ag NCs with six silver atoms as core (Ag-6-NCs) were self-assembled under the induction of a good solvent (water) and a poor solvent N-methyl-2-pyrrolidone (NMP). By limiting the rotation and vibration of Ag-6-NCs ligands, and accompanied by the ligand-to-metal charge transfer (LMCT), aggregation-induced emission (AIE) occurred, and the strong fluorescence emission of Ag-6-NCs/NMP/H2O assembly was realized through solvophobic interactions and noncovalent interactions, such as hydrogen-bonding interactions and pi-pi staking. Compared with the original Ag-6-NCs, the fluorescence lifetime of Ag-6-NCs/NMP/H2O was extended from 0.56 to 11.77 mu s, the QY was increased from 2.3 to 17.6%, and its photoluminescence (PL) intensity was enhanced 37-fold to the order of 10(7). Long lifetime and large Stokes shift (similar to 165 nm) indicate that the Ag-6-NCs/NMP/H2O assembly was a phosphorescent emitter. This research demonstrates that the excellent optical properties and regular response to temperature of the Ag-6-NCs/NMP/H2O assembly make it possible to fabricate white-light-emitting diodes (WLEDs) or temperature sensing materials.