Fractal Patterns in Nucleation and Growth of Icosahedral Core of [Au_nAg_44–n(SC₆H₃F₂)₃₀]^4– (n = 0–12) via ab Initio Synthesis: Continuously Tunable Composition Control

Abstract

An ab initio one-pot synthesis of the bimetallic clusters [Au n Ag 44−n (SC 6 H 3 F 2 ) 30 ] 4− (abbreviated (AuAg) 44 ; n ≤ 12) is reported. The mixed-metal (AuAg) 44 clusters, synthesized with different reactant Au/Ag ratios, exhibit a fractal-like distribution, suggesting that nucleation of the icosahedral core is a fractal growth process. X-ray crystallographic studies provided unambiguous evidence that the doped Au atoms occupy the icosahedral sites and the maximal doping is 12. The number of Au atoms (n) in [Au n Ag 44−n (SR) 30 ] 4− (SR = SC 6 H 3 F 2 ) can be continuously tuned from 0 to 12. A three-way correspondence between single-crystal structure, MS, and UV−vis is established, thereby facilitating future identification (finger-printing) of the alloy [Au n Ag 44−n (SR) 30 ] 4− clusters. The temperature, solvent, and temporal effects in the synthesis were also investigated.

Nanogymnastics: Visualization of Intercluster Reactions by High-Resolution Trapped Ion Mobility Mass Spectrometry

“…The DFT structure is in agreement with the crystal structure of Au 12 Ag 32 (SR) 30 directly prepared from mononuclear precursors by Zheng et al 28,29 In a recent report of alloy clusters formed in a related "one-pot ab initio synthesis", Zheng et al showed by X-ray crystallography that any number of Au doping (from 0 to 12) in Ag 44 (SR) 30 clusters leads to Au exchange in the icosahedral core. 29 By contrast, Xie et al have suggested that 12 Au atoms exchange on the surface (staple) of the preformed Ag 44 (SR) 30 clusters (rather than in its core) when the exchange is mediated by Au(SR) 2 Cl-type thiolates. 30 In a related study, Burgi et al have inferred that over longer times, silver exchange occurs preferentially in the core of a Au 38 (SR) 24 cluster rather than on its staples.…”

Molecule-like and lattice vibrations in metal clusters

“…, co-reduction of a mixture of metal salts). 33 The Ag 44− x Au x (SR) 30 clusters used in our experiments were synthesized by the co-reduction method and their UV/Vis spectra resemble those of the previously reported Ag 44− x Au x (SR) 30 clusters which consist of twelve 17 or nearly twelve Au atoms. 33 Therefore, it is very likely that the number of Au atoms in the Ag 44− x Au x (SR) 30 clusters used in our experiments is also twelve, approximately.…”

“…5B ) indicate that the number of Au atoms in them is 0–12 and that these Au atoms are located in the innermost, hollow icosahedral shell. 33 It is also known that when the number of Ag atoms in Ag 44− x Au x (SR) 30 clusters is significantly less than twelve, the UV/Vis absorption spectra of such clusters are similar to those of Ag 44 (SR) 30 and that it is not possible to incorporate more than twelve Au atoms in Ag 44 (SR) 30 by direct synthesis ( i.e. , co-reduction of a mixture of metal salts).…”

“… 37 Ag 29 (BDT) 12 clusters used in these measurements were synthesized using a previously reported procedure. 38 Ag 44 (2,4-FTP) 30 and Ag 44− x Au x (2,4-FTP) 30 clusters used in these measurements were synthesized adopting the procedure reported by Zheng et al 33 The Au 25 (PET) 18 clusters used in these measurements were synthesized using reported procedures. 39 Anionic Au 25 (PET) 24 clusters were oxidized to neutral clusters by running the clusters on a thin layer chromatographic (TLC) plate using DCM as the eluent.…”

Revealing the composition-dependent structural evolution fundamentals of bimetallic nanoparticles through an inter-particle alloying reaction

“…39 It is also worth noting that the reported alloy Au x Ag 44− x NCs so far exclusively adopted the M–S framework of [Ag 44 (SR) 30 ] 4− , where up to 12 Ag atoms are substitutable by Au atoms. 35,40–42 Therefore, [Ag 44 (SR) 30 ] 4− , [Au 44 (SR) 26 ] 2− and their alloy NCs provide an ideal platform for decoding the composition dependent alloying chemistry at the molecular and atomic levels, although an efficient synthetic method should be developed for fine tuning the composition of alloy Au x Ag 44− x NCs in a wide composition range.…”