Surface Engineering of Au₃₆(SR)₂₄ Nanoclusters for Photoluminescence Enhancement

Abstract

(1 of 6) 1600388The luminescence of metal nanoparticles constitutes an area of significant interest in recent years, in particular the luminescence of ultrasmall gold and silver nanoparticles. Gold has particular surface characteristics and low toxicity compared to other luminescent nanoparticles. However, gold often has weaker luminescence; thus, a major goal of research is to enhance gold nanoparticle luminescence. In this work, surface ligand engineering is performed on atomically precise Au 36 (SR) 24 nanocrystals (also called nanoclusters, whereSR represents thiolates) to determine different optical and luminescent properties affected by different ligands (i.e., the R groups). The gold nanocluster formula, structure, luminescence, and lifetime are characterized by techniques including electrospray ionization mass spectrometry, UV-vis and fluorescence spectroscopies. It is found that the surface ligands (i.e., different R groups) can affect the charge density transfer between the ligands and the metal core, which in turn influences the luminescence intensity. The luminescence intensity is found to correlate with the electronegativity of the surface ligands that are exchanged onto Au 36 . The effects of surface engineering on the luminescence properties of gold nanoclusters may open up exploration for applications such as biolabeling, luminescent probes, and other applications.

Observation of a new type of aggregation-induced emission in nanoclusters

“… 1 , 2 , 8 , 17 – 24 Although several luminescent NCs have been reported, 8 , 18 , 21 – 31 most of them exhibit lower quantum yields (QYs) compared with other fluorescent nanomaterials (such as lanthanide nanoparticles, 32 organic dyes 33 and quantum dots 34 ), which severely impedes extensive application of fluorescent NCs in biological and sensing fields. Several strategies have been developed to enhance the PL QY of NCs, and they can be mainly classified into the following three categories: (1) tailoring the capping ligands of NCs (in terms of controlling the ligand to metal charge transfer (LMCT) process); 8 , 35 – 37 (2) controlling the metal composition in the NC kernel; 21 , 22 , 26 , 28 , 29 , 38 and (3) aggregation-induced emission (AIE) from non- or weakly luminescent metal NCs (or complexes). 19 , 20 , 25 , 39 , 40 Nowadays, the AIE strategy is being expanded to the hydrocarbon, metal complex, metal NC, and macromolecular research fields.…”

Supramolecules‐Guided Synthesis of Brightly Near‐Infrared Au22 Nanoclusters with Aggregation‐Induced Emission for Bioimaging

“…[11,12] To date, several recent studies have been reported aiming to produce AuNCs with enhanced luminescence, [13][14][15][16][17] and the mechanism behind high luminescence is now better explained. [18][19][20][21] Among all of the explanations, increasing the content and aggregation degree of Au (I)-thiolate complexes on the surface of Au(0) core has been widely accepted as an effective way to gain highly luminescent AuNCs through enhanced aurophilic interactions. [22,23] Besides, AuNCs can undergo aggregation-induced emission (AIE) mechanism that further enhances the PL intensity.…”

“…However, the low quantum yield (QY) greatly limits their exploitation (typically ≈0.1%) . To date, several recent studies have been reported aiming to produce AuNCs with enhanced luminescence, and the mechanism behind high luminescence is now better explained . Among all of the explanations, increasing the content and aggregation degree of Au (I)‐thiolate complexes on the surface of Au(0) core has been widely accepted as an effective way to gain highly luminescent AuNCs through enhanced aurophilic interactions .…”

Deepening the Understanding of Thiolate-Protected Metal Clusters Using High-Performance Liquid Chromatography

“…40,41,43,46,53,58,61,62,74,80,125,130,138,147,149,159,162,166,197 888,890,891,915,916,922,932,936939 Furthermore, such ligandexchange reactions can be also used for size-selective synthesis of Au n (SR) m clusters, which are difficult to prepare directly. 46,53,61,62,80,138,149,159,264,301,306,467,484,491,515,571,628,633,637,662,744747,769,772,773,…”