Bright and Photostable Fluorescent Metal Nanocluster Supraparticles from Invert Emulsions

Abstract

Fluorescent supraparticles of gold, silver and copper nanoclusters are synthesized by simply drying of invert emulsions, resulting in a dozen-fold increase in photoluminescence quantum yield (up to � 80 %) and a significant improvement in photostability. The inhibition of the ligand twisting during the intramolecular charge transfer is found to be responsible for the enhancement, especially for the gold nanocluster supraparticles. This research provides a general, flexible, and easy method for producing highly luminescent and photostable metal nanocluster-based materials that promise practical applications in white-light-emitting diodes.Fluorescent metal nanoclusters (MNCs), composed of several to tens of metal atoms, emerge as promising materials in various applications such as bio/chemo-analysis, catalysis, biomedicine, etc. [1,2] Nevertheless, MNCs typically suffer from low photoluminescence quantum yields (PLQYs) and poor photostability that hinder their applications. Research efforts in the past decades have directed attention to enhancing the PLQYs of MNCs. Assembling MNCs to trigger the aggregation-induced emission enhancement (AIEE) effect is among the most effective strategies for high PLQYs. [3,4] Bright assemblies of MNCs have been obtained through solvent induction, [5,6] gelation, [7] intermolecular interaction, [8,9] and so forth. However, the resistance of MNCs to photobleaching, namely photostability, has been overlooked. Conventional methods to improve the photostability of fluorescent materials like encapsulation in matrixes can decrease PLQYs. [10] Therefore, the challenge