Modulating the Structural Complexity of AuNCs Aggregates for Generation of Bright Luminescence

Abstract

Self-assembly of coinage metal nanoclusters constitutes an important branch for the construction of bright luminescent materials. They also serve as a class of promising building blocks for the study of hierarchically organized assemblies due to their potential of generating high structural complexity. However, the strong intercluster interactions exert great difficulty and uncertainty on the modulation of the outcome aggregation structures. To explore a feasible methodology for constructing complex structures that combine order and disorder, accompanied by emerging desirable optical performances, herein we manipulate the supramolecular interactions of a gold nanocluster, namely, DPT-AuNCs through the incorporation of an amphiphilic cation, i.e., 1-dodecyl-3-methylimidazolium (DMI⁺). Diverse aggregation structures are obtained through coassembly, and a sea urchin-like aggregate with a complexity index of CI = 16.5 is formed by elevating the concentration of DMI⁺. Moreover, a positive correlation between structural complexity and emission intensity was observed, and strongly luminescent NCs-based aggregates were obtained. The mechanism for the emergence of structural complexity is demonstrated via kinetic studies, ¹H NMR titration, theoretical computation, etc. The cation-π interaction is found to be vital for the association between DMI⁺ and DPT-AuNCs, which modulates the supramolecular interactions for assembly and in turn facilitates the growth of aggregates in multiple dimensions. The sea urchin-like aggregate is formed through a dynamic assembly process, mediated by the pre-equilibrium of DMI⁺ micelles at high concentrations. Finally, the luminescent NC aggregates can also be obtained by incorporating different types of amphiphilic cations, thus generalizing the method for constructing complex assembly structures.