Gold Doping of Silver Nanoclusters: A 26‐Fold Enhancement in the Luminescence Quantum Yield

Abstract

Ah igh quantum yield (QY) of photoluminescence (PL) in nanomaterials is necessary for aw ide range of applications.U nfortunately,t he weak PL and moderate stability of atomically precise silver nanoclusters (NCs) suppress their utility.Herein, we accomplished a ! 26-fold PL QY enhancement of the Ag 29 (BDT) 12 (TPP) 4 cluster (BDT:1 ,3-benzenedithiol;T PP:t riphenylphosphine) by doping with adiscrete number of Au atoms,producing Ag 29Àx Au x (BDT) 12 -(TPP) 4 ,x= 1-5. The Au-doped clusters exhibit an enhanced stability and an intense red emission around 660 nm. Singlecrystal XRD,m ass spectrometry,o ptical, and NMR spectroscopys hed light on the PL enhancement mechanism and the probable locations of the Au dopants within the cluster.Noble-metal nanoclusters (NCs), consisting of ap recise number of metal atoms and ligands,exhibit unique molecular, optical, and physicochemical properties because of their distinct electronic structures.[1] Thetypical size of NCs lies in between atoms and plasmonic nanoparticles. [1a,2] Particularly, NCs of gold, silver, and their alloys are being investigated for their potential for light-energy conversion applications, [3] in addition to their catalytic activity, [4] biocompatibility, [5] and tunable emissions in the visible and near-infrared (NIR) regions.[6] Thephotophysical properties of NCs were found to be influenced by their intrinsic structure,c omposition, core size,a nd environment, including solvent and protecting ligand. [1c, 7] While luminescent NCs are in high demand, the origin of luminescence is not fully elucidated-with some studies implicating ligand-to-metal charge transfer (LMCT) and/or ligand-to-metal-metal charge transfer (LMMCT). [8] Thepivotal roles of the nature of metal atoms and the ligands signify the opportunity to tune the photoluminescence (PL) quantum yield (QY) of NCs for practical applications. [8,9] In this direction, various research groups followed the surface functionalization of NCs with diverse protecting environments,i ncluding polymers, [10] thiols, [11] and proteins.[12]Another approach is the alloying or doping of the metal core of aN Cw ith another suitable metal; [13] this method is attractive not only because of the control it affords over the number of alloying atoms,b ut also because it opens the opportunity to gain fundamental insights into the PL evolution with doping at as ingle-atom level. Fori nstance,a200-fold PL QY enhancement was observed when Au 25 NCs were doped with 13 silver atoms.[14] However,the role of doping on well-characterized Ag NCs-materials that would benefit immensely from enhancing their QY and stability-is still unknown.Among thoroughly characterized (including X-ray structure) visible-light-emitting Ag NCs,t he Ag 29 (BDT) 12 (TPP) 4 cluster (BDT:1 ,3-benzenedithiol;T PP:t riphenylphosphine) has moderate stability and weak PL QY (0.9 %), where PL is too weak to perceive by the naked eye. [15] In this work, we demonstrate the PL QY enhancement of Ag 29 NCs by doping with ad istinct number of Au a...

Silver Doping‐Induced Luminescence Enhancement and Red‐Shift of Gold Nanoclusters with Aggregation‐Induced Emission

“…These advantages make NCs promising in diverse application fields including environment, energy conversion, and biomedicine . To realize these applications, tremendous efforts were devoted to the design of efficient synthetic strategies for highly luminescent metal NCs, and some exciting progresses have been achieved . For example, our group recently devoloped a novel synthetic strategy for highly luminescent Au 0 @Au I ‐thiolate NCs with aggregation induced emission (AIE) .…”

Atomically Precise Bimetallic Nanoclusters as Photosensitizers in Photoelectrochemical Cells

“…The well‐defined structures of metal NCs enable scientists to study their structure‐property relationships at the atomic level . For example, a single Au–Ag substitution could greatly change the electronic structure of metal NCs, boosting their photoluminescence quantum yield as high as 200‐fold . Recently, ligand‐protected gold NCs have been successfully used for light energy conversions, such as in solar cells and water splitting .…”

Cu2+‐Induced Structural Isomers: Effect of Foreign Metal Ions on the Structure and Properties of Silver Nanoclusters

“…Among these factors, metal ions are a typical factor influencing the atomic number and the crystal structures of metal nanoclusters. Based on previous studies, the effect of metal ions can be classified into four types (Scheme ): (a) metal ions equally replace metal atoms of templated nanoclusters, without changing the number of atoms and structure of metal nanoclusters, such as Cd 1 Au 24 and Au 1 Ag 28 ; (b) metal ions are doped into templated nanoclusters to form another sized nanoclusters, which have the same structure as the template nanoclusters, like Cu 1 Au 24 and Ag 2 Au 25 ; (c) metal ions are doped into templated nanoclusters, whereupon, the structure is induced to change, like Cd 4 Au 20 ; (d) metal ions are not doped into templated nanoclusters, but induce another sized nanoclusters to form, which have different a crystal structure from templated nanoclusters, such as transformation of Au 23 to Au 28 and Au 25 to Au 44 in the presence of Cd 2+ and Cu 2+ , respectively. Wu et al.…”