Tunable Emission Enhancement of Gold Nanocluster at Giant Vesicles Interfaces: Electrostatic and Hydrophobic Effects

Metal nanoclusters (MNCs) are a rapidly flourishing research area, distinguished by size-tunable emission and high fluorescence quantum yields (QY_f). However, the intramolecular vibrations and rotations of the capping ligands cause a significant decrease in their QY_f in aqueous media. In this work, we demonstrate a strategy to recover and amplify the emission of gold nanoclusters (AuNCs) by modulating their electrostatic and hydrophobic environments. We have synthesized 11-mercaptoundecanoic acid (MUA)-capped AuNCs via a ligand exchange method and investigated their interactions with giant vesicles. By altering the surface charge and hydrophobicity of these vesicular aggregates, we observed that interactions with oppositely charged, highly hydrophobic surfaces led to a significant increase in emission intensity and QY_f, whereas for the same-charged vesicles, QY_f remains unchanged. Utilizing this enhancement, we developed a high-efficiency Förster resonance energy transfer (FRET) system using AuNCs and Sulforhodamine B (SRh) within vesicular aggregates.