Atomic‐Level Alloying and De‐alloying in Doped Gold Nanoparticles

Abstract

Atomically precise alloying and de-alloying processes for the formation of Ag-Au and Cu-Au nanoparticles of 25-metal-atom composition (referred to as Ag(x)Au(25-x)(SR)18 and Cu(x)Au(25-x)(SR)18 , in which R = CH2CH2Ph) are reported. The identities of the particles were determined by matrix-assisted laser desorption ionization mass spectroscopy (MALDI-MS). Their structures were probed by fragmentation analysis in MALDI-MS and comparison with the icosahedral structure of the homogold Au25(SR)18 nanoparticles (an icosahedral Au13 core protected by a shell of Au12(SR)18). The Cu and Ag atoms were found to preferentially occupy the 13-atom icosahedral sites, instead of the exterior shell. The number of Ag atoms in Ag(x)Au(25-x)(SR)18 (x = 0-8) was dependent on the molar ratio of Ag(I)/Au(III) precursors in the synthesis, whereas the number of Cu atoms in Cu(x)Au(25-x)(SR)18 (x = 0-4) was independent of the molar ratio of Cu(II)/Au(III) precursors applied. Interestingly, the Cu(x)Au(25-x)(SR)18 nanoparticles show a spontaneous de-alloying process over time, and the initially formed Cu(x)Au(25-x)(SR)18 nanoparticles were converted to pure Au25(SR)18. This de-alloying process was not observed in the case of alloyed Ag(x)Au(25-x)(SR)18 nanoparticles. This contrast can be attributed to the stability difference between Cu(x)Au(25-x)(SR)18 and Ag(x)Au(25-x)(SR)18 nanoparticles. These alloyed nanoparticles are promising candidates for applications such as catalysis.

Toward the Creation of Functionalized Metal Nanoclusters and Highly Active Photocatalytic Materials Using Thiolate-Protected Magic Gold Clusters

“…87 Note that Jin et al also reported these Cu-doped clusters to be unstable. 88 The atomic radius of Cu (1.28 ¡) is smaller than that of Ag (1.44 ¡). Cu doping therefore distorts the framework structure significantly, 87 which likely destabilizes Au 25¹n Cu n (SR) 18 ; thus, only up to five Cu atoms can be incorporated into Au 25 -(SR) 18 .…”

Optical properties of nanoalloys

“…Refs. 21,23,28 . Indeed, during the revision stage of the present perspective article, a further review has appeared on-line 70 .…”

“…Section 2 is then dedicated to a brief survey of this topic. Moreover, a sub-field evolving in a particularly tumultuous fashion among alloy nanosystems is that of monolayer-protected, size-selected clusters [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] . For clarity of presentation, we then single out these latter systems apart, so that in Section 3 we discuss other nanosystems, i.e., nanoclusters and nanorods or nanowires both free and in a less interacting environment, while Section 4 will be devoted to monolayer-protected alloy clusters, also providing a literature review of the explosive growth in this sub-field.…”

Ligand-protected gold clusters: the structure, synthesis and applications

“…270 The Pt atom occupies position at the core centre, similarly to PdAu 24 (SR) 18 Unlike platinum and palladium, which form singly doped systems MAu n L m , silver and copper can form bimetallic variable-composition clusters. In particular, the Ag x Au 257x (SC 12 H 25 ) 18 (x = 1 ± 11), 272 Ag x Au 257x (SCH 2 Bn) 18 (x = 1 ± 8), 273 Ag x Au 257x (SCH 2 Bn) 18 (x = 6.7), 103 Ag x Au 387x (SR) 24 (x =1, 3, 5, 6), 100 and Ag x Au 1447x (SCH 2 Bn) 60 (x = 30, 34, 52, 53, 60) 99 clusters were synthesized. They are multiply doped analogues to the Au 25 (SR) 18 , Au 38 (SR) 24 and Au 144 (SR) 60 clusters considered above.…”

“…For instance, the maximum number of silver atoms (x max ) is 60 for Ag x Au 1447x (SCH 2 Bn) 60 clusters 99 and only 8 for Ag x Au 257x (SCH 2 Bn) 18 . 273 Reactions of gold nanoparticles with AgSCH 2 Bn result in the [Ag x Au 257x (PPh 3 ) 10 (SCH 2 Bn) 5 Cl 2 ] 2+ clusters containing at most twelve silver atoms. 274 The thirteenth silver atom can be introduced into the cluster by the reaction of Au 11 with AgSCH 2 Bn.…”