Kinetically controlled self-assembly of atom-precise gold nanoclusters into multicolor emissive supramolecular assemblies

Abstract

Establishing self-assembly chemistry based on metal nanoclusters (NCs) holds great potential for promoting performance improvement and enriching functional diversity. Herein, by a well-designed liquid reaction strategy, the individual atomic-precise Au₅ NCs self-assembled into a highly regular and ordered nanofiber supramolecular structure with improved photoluminescence (PL). The kinetically controlled structural growth mechanism was unraveled through time-dependent in situ multi-spectral monitoring of the self-assembly process. The self-assembly experienced three structural evolution stages involving disordered aggregation, lateral arrangement and longitudinal stacking, which were driven by multiple driving forces involving aurophilic interaction, dipolar attraction and π–π stacking. By establishing dynamic structure–property relationship, the assembly-induced PL enhancement mechanism was illustrated. The enhanced aurophilic Au(I)–Au(I) interactions promoted the excited state relaxation dynamics via a radiative pathway, and the structures with enhanced rigidity reduced the level of nonradiative relaxation of excited states, which collectively contributed to the increase in PL intensity. The assembly-promoted average Au(I)–Au(I) distance decreased, causing a red shift in the PL wavelength. Inspired by the assembly-induced PL enhancement of Au₅ NCs, a series of multicolor emissive nanofibers were successfully obtained by the self-assembly of various atomically precise Au NCs. The multicolor nanofibers comprising independent and homogeneous chromophores exhibited phosphorescence emissions, with the PL wavelengths spanning the whole visible-light range. They were well employed as multicolor luminescent inks, showing broad prospects for optical property-related potential applications.