Templated Atom‐Precise Galvanic Synthesis and Structure Elucidation of a [Ag₂₄Au(SR)₁₈]⁻ Nanocluster

Abstract

Synthesis of atom-precise alloy nanoclusters with uniform composition is challenging when the alloying atoms are similar in size (for example, Ag and Au). A galvanic exchange strategy has been devised to produce a compositionally uniform [Ag24Au(SR)18](-) cluster (SR: thiolate) using a pure [Ag25(SR)18](-) cluster as a template. Conversely, the direct synthesis of Ag24Au cluster leads to a mixture of [Ag(25-x)Au(x)(SR)18](-), x=1-8. Mass spectrometry and crystallography of [Ag24Au(SR)18](-) reveal the presence of the Au heteroatom at the Ag25 center, forming Ag24Au. The successful exchange of the central Ag of Ag25 with Au causes perturbations in the Ag25 crystal structure, which are reflected in the absorption, luminescence, and ambient stability of the particle. These properties are compared with those of Ag25 and Ag24Pd clusters with same ligand and structural framework, providing new insights into the modulation of cluster properties with dopants at the single-atom level.

Metal Nanoclusters with Synergistically Engineered Optical and Buffering Activity of Intracellular Reactive Oxygen Species by Compositional and Supramolecular Design

“…3b triangles and Fig. 2a), the PL efficiency is nearly constant and relatively low, in agreement with previous reports on Ag clusters protected with small thiol ligands 36–38 . In this time interval, the growth of the PL signal is therefore due to the increasingly larger number of clusters in solution, consistent with over 10-fold increase of the ensemble’s absorbance.…”

“…We notice that other mechanisms could, in principle, lead to enhanced PL, such as the intercalation of Au atoms between the early-formed Ag cores and their capping thiols, or the substitution of Ag atoms with thiolated Au species. Both these mechanisms would, however, result in significant alteration of the electronic structure of the clusters, either due to increase of their size by incorporation of additional atoms 10 , or to the modification of their chemical composition 38 , in disagreement with the optical absorption and PL spectra in Figs 1b and 3a. We note that the final PL quantum yield of our Ag/Au-t clusters is ~2%, which indicates that the shelling is incomplete.…”

“…One possible limitation to the use of Ag clusters as multifunctional luminescence markers is, however, that the emission efficiency of systems protected with small capping molecules, such as thiols, is typically very low 36–38 . In order to address this issue, Ag clusters capped with bulky biomolecules 39–41 and polymers 42 , which protect the metal cores from luminescence quenchers 43 , have been realized.…”

Templated Atom‐Precise Galvanic Synthesis and Structure Elucidation of a [Ag24Au(SR)18]− Nanocluster

“…Au red, Ag silver white, Syellow,Ppurple, Cgray [19]. Au red, Ag silver white, Syellow,Ppurple, Cgray [19].…”

“…Au red, Ag silver white, Cgray,Syellow [19]. B) Orientation of ligands methyl groups in p-p interactions.…”