From Aggregation-Induced Emission of Au(I)–Thiolate Complexes to Ultrabright Au(0)@Au(I)–Thiolate Core–Shell Nanoclusters

Abstract

A fundamental understanding of the luminescence of Au-thiolate nanoclusters (NCs), such as the origin of emission and the size effect in luminescence, is pivotal to the development of efficient synthesis routes for highly luminescent Au NCs. This paper reports an interesting finding of Au(I)-thiolate complexes: strong luminescence emission by the mechanism of aggregation-induced emission (AIE). The AIE property of the complexes was then used to develop a simple one-pot synthesis of highly luminescent Au-thiolate NCs with a quantum yield of ~15%. Our key strategy was to induce the controlled aggregation of Au(I)-thiolate complexes on in situ generated Au(0) cores to form Au(0)@Au(I)-thiolate core-shell NCs where strong luminescence was generated by the AIE of Au(I)-thiolate complexes on the NC surface. We were able to extend the synthetic strategy to other thiolate ligands with added functionalities (in the form of custom-designed peptides). The discovery (e.g., identifying the source of emission and the size effect in luminescence) and the synthesis protocols in this study can contribute significantly to better understanding of these new luminescence probes and the development of new synthetic routes.

All‐Copper Nanocluster Based Down‐Conversion White Light‐Emitting Devices

“…Reduction of Cu 2+ by GSH is evidenced by the absence of any satellite peaks around 942 eV. We note that the difference between 2p 3/2 peaks of Cu 0 and Cu + species is only 0.1 eV, so that the valence state of copper in Cu NCs may lie between zero (in the core) and one (at the surface where it is bound to sulfur), which is consent with the previous reports 13, 22. The ratio of S to Cu was estimated to be 4:1 from XPS measurements.…”

“…Such long (microseconds) excited state lifetimes, together with the observed large spectral shift between the PLE and PL maxima suggest that the emission of Cu clusters occurs through a phosphorescence mechanism, attributed to ligand‐to‐metal charge transfer from the sulfur atoms of GSH to the Cu atoms in the core, followed by a radiative relaxation through a metal‐centered triplet state, which is a commonly observed feature of thiolate‐capped metal NCs 18, 23. Increased degree of aggregation in solutions with increasing f ethanol leads to a stronger inter‐ and intracluster interactions, resulting in the restriction on the molecular vibrational, rotational, and torsional movements of Cu NCs 24. This reduces the probability of nonradiative path and activates the radiative decay, which results in a longer PL lifetime and enhanced PL intensity 23, 25.…”

Multivalent Glycosylation of Fluorescent Gold Nanoclusters Promotes Increased Human Dendritic Cell Targeting via Multiple Endocytic Pathways

“…The most important optical features of AuZw and AuZwTriMan are summarised in Table 2. 58 but has only recently been reported for metal (Au, Cu) nanoclusters 45,59 . For instance, in an elegant study from the Xie laboratory it was shown that Au NC aggregation induced by the presence of ethanol or by electrostatic interactions in the presence of cadmium cations led to a drastic fluorescent enhancement 45 .…”

“…For instance, the Mattoussi lab reported the preparation of red-emitting Au NCs with a quantum yield of up to 14% when stabilised with bidentate thiolated ligands containing a zwitterionic group 40 . NC features such as tunable photoluminescence [41][42] , multiexponential fluorescence lifetime [43][44] , or aggregation induced enhancement 45 have been extensively studied with potential applications in the fields of sensing 46 , bioimaging 47 and optics 48 . Other interesting properties of NCs relevant for therapeutic applications rely on their ultra-small size, low toxicity and stability in physiological media.…”

Photoluminescent Gold Nanomaterials as Sensitive Probes

“…They are often called gold nanodots (Au NDs) or gold nanoclusters (Ag NCs), with sizes usually smaller than 2 nm; Au NCs are commonly reffered to the one having less than 30 Au atoms per cluster. The molecular-like optical properties (photoluminescence) of Au NDs and NCs are highly dependent on the size of Au core and the number of Au atoms per templates, respectively [4,5]. The Au complexe on the surface of Au core and its surface density affect the stability and optical properties of Au NDs, while the nature and size of the template affect that of Au NCs.…”