Photoluminescence Enhancement in Ag ₂₉ Nanoclusters via Ligand Engineering and Controlled Aggregate Formation

Systematic control of the photophysical properties of metal nanoclusters (NCs) through ligand design is a powerful strategy for future nanomaterials. In this study, we synthesized silver NCs with improved photoluminescence (PL) properties via surface-ligand engineering. We derivatized 3,5-dimercaptobenzoic acid (DMBA) with tethering a naphthalene ring via an amide linkage to form the BDT-Naph ligand. The use of BDT-Naph ligand with the aid of tetraphenylphosphine (PPh 3 ) as a subligand yielded luminescent silver NCs with the composition of [Ag 29 (BDT-Naph) 12 (PPh 3 ) 4 ] 3– ( Ag 29 -BDTN ). The solubility of Ag 29 NCs could be controlled with the choice of countercations of the trianionic NC, such as Na +, tetrabutylammonium (TBA), and tetraoctylammonium (TOA) cations. Ag 29 -BDTN NCs exhibited an improved photoluminescence quantum yield (PLQY) of 34% in THF compared to Ag 29 NCs carrying unmodified 3,5-benzenedithiol (BDT) with the composition of [Ag 29 (BDT) 12 (PPh 3 ) 4 ] 3– ( Ag 29 -BDT, PLQY: 6%) in the same solvent. Furthermore, stable aqueous dispersions of Ag 29 -BDTN NC aggregates maintaining a relatively high PLQY (24%) were obtained through a simple dilution of THF solution by water. It is worth noting that the emissive aggregates could be lyophilized into a powder and subsequently fully dispersed in water.