Hierarchical Assembly of Gold Nanoclusters Mediated by Kinetic Aggregation of Amphiphilic Amino Acid for Generation of Enhanced Emission and Tunable CPL-Activity

Hierarchical assembly of coinage-metal nanoclusters constitutes an important strategy for constructing optical materials with advanced luminescent performance and chiroptical activities. However, it remains intractable to rationally design and direct the hierarchical assembly process that leads to the desired functionalities. Herein, hierarchical assemblies of 6-aza-2-thiothymine-protected gold nanoclusters (ATT-AuNCs) are constructed by coassembling with an amphiphilic amino acid (Fmoc-Arg) whose aggregates serve as reservoirs to control the assembly kinetics. In the presence of a proper amount of Fmoc-Arg higher than its critical aggregation concentration, dynamic coassembly can be observed, which gives rise to tassel-like and hydrangea-like aggregates. Thermodynamic and kinetic spectral analyses verify that the controlled release of Fmoc-Arg and subsequent association with ATT-AuNCs are involved in the hierarchical assembly mechanism. Moreover, the obtained tassel-like and hydrangea-like aggregates exhibit enhanced emission and chiroptical activity. By introducing rhodamine B to construct a FRET system, the emission color as well as CPL can be bathochromically shifted. The tunable optical properties endow ATT-AuNCs/Fmoc-Arg systems with potential applications in anticounterfeiting. The dynamic assembly of nanoclusters described herein controlled by the reservoir of aggregated amphiphiles represents a feasible strategy for constructing hierarchical assemblies with excellent performance.