Molecular Packing-Driven Manipulation of Aggregation Induced Emission in Gold Nanoclusters

Abstract

A key limitation of supramolecular force-driven molecular assembly in aggregation-induced emission (AIE) materials is the need to precisely regulate molecular interactions within the assembly. Achieving such assemblies with in situ manipulable molecular arrangements could provide valuable insights into the role of molecular forces in AIE. Herein, by using glutathione-protected gold nanoclusters (AuNCs) as a model AIE material and a naturally occurring polyphenol, tannic acid (TA), as the assembling agent, we demonstrate that assemblies dominated by covalent bonds and hydrogen bonding show enhanced AIE, while those dominated by pi-pi stacking promote charge transfer, resulting in significant photoluminescence (PL) quenching. This phenomenon primarily stems from the oxidation of TA into smaller aromatic ring structures, leading to an increase in pi-pi interactions. The complete in situ oxidation of TA within the assembly induces a morphological transition from 3-D spherical to 2-D sheet-like structures due to the dominance of pi-pi interactions, consequently resulting in complete PL quenching of AuNCs. These findings highlight the critical role of molecular packing in modulating the AIE properties of AuNCs.