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