Heavily doped Au_25–xAg_x(SC₆H₁₁)₁₈⁻ nanoclusters: silver goes from the core to the surface

Abstract

We report a method for heavy doping of the Au25(SR)18 nanocluster (where R = C6H11) with silver through the Ag(I)-thiolate complex induced size/structure transformation of Au23(SR)16(-) into Au25-xAgx(SR)18(-). X-ray crystallographic analysis revealed that Ag dopants are distributed not only in the icosahedral core but also in the surface staple motifs; the latter was not achieved in earlier studies of alloy Au25-xAgx nanoclusters.

Molecular “surgery” on a 23-gold-atom nanoparticle

“…There are only two specific sites (centrosymmetric) where Ag can be found. This is different from previously reported Au/Ag alloy nanoclusters in which the Ag atoms are distributed in many sites ( 31 , 34 , 35 ). The occupancy of Ag is determined to be 31.5 and 30.0% at position 1 in the two crystallographically independent clusters, whereas position 2 has a lower occupancy, determined to be 12.7 and 6.4%.…”

“…On the other hand, structure/size transformation of [Au 23 (SR) 16 ] − to [Au 25− x Ag x (SR) 18 ] − upon heavy silver doping ( x ~ 19) was reported in our previous work ( 31 ). Compared to the present work, the different results (Au 23− x Ag x with light doping versus Au 25− x Ag x with heavy doping) arise from the different amounts of Ag I (SR) added in the reaction.…”

Structure-conserving spontaneous transformations between nanoparticles

“…Crystal structures of Ag 25 (DMBT) 18 and Au 25 (PET) 18 show that the inherent structural framework of the icosahedral core and staples, described above, are identical and the presence of different ligand R groups do not affect this structure222328. In addition, crystal structure data of alloys have also shown that the substitution of Ag atoms into all the three available positions (C, I and S) in Au 25 (SR) 18 does not alter this framework5354. The recently reported structure40 of Ag 24 Au 1 (SR) 18 shows that the Au atom occupies the C position, preserving the inherent structure.…”

Identification of an Eight-Electron Superatomic Cluster and Its Alloy in One Co-crystal Structure

“…So far, a variety of atom-precise Au-based alloy NCs have been reported. Especially, the doping of Au 25 (SR) 18 clusters was extensively studied with metals such as Cu [5], Pd [6], Pt [6], Ag [5,7], Cd [8], and Hg [9] and the results imply that Pd, Pt, and Cd atoms preferentially occupy the inner icosahedral positions, Ag resides on the surface of the superatomic core whereas Cu and Hg are found in the staple motifs. On the other hand reports on silver alloy NCs are comparatively scarce.…”

“…Prominent silver/gold alloy examples being structurally characterized include Au 25-x Ag x [10], Au 38-x Ag x [11], Au 24 Ag 20 [12], Au 24 Ag 46 [13], Au 12 Ag 32 [3b], Au 25 Ag 2 [14], Ag 28 Au [15], Au 12 Ag 13 [16], Au 80 Ag 30 [17], Au 3 Ag 38 [18], Au 7 Ag 8 [19], and Au x Ag y [20] + via a galvanic replacement method [22]. Despite the tremendous progresses in their synthesis and characterization, the mechanistic studies for the formation of Ag alloy NCs are lagged significantly behind.…”