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

E-ISSN： 1521-3765|19|13|4238-4243

ISSN： 0947-6539

Source： CHEMISTRY - A EUROPEAN JOURNAL, Vol.19, Iss.13, 2013-03, pp. : 4238-4243

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Abstract

AbstractAtomically precise alloying and de‐alloying processes for the formation of Ag–Au and Cu–Au nanoparticles of 25‐metal‐atom composition (referred to as AgxAu25−x(SR)18 and CuxAu25−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 AgxAu25−x(SR)18 (x=0–8) was dependent on the molar ratio of AgI/AuIII precursors in the synthesis, whereas the number of Cu atoms in CuxAu25−x(SR)18 (x=0–4) was independent of the molar ratio of CuII/AuIII precursors applied. Interestingly, the CuxAu25−x(SR)18 nanoparticles show a spontaneous de‐alloying process over time, and the initially formed CuxAu25−x(SR)18 nanoparticles were converted to pure Au25(SR)18. This de‐alloying process was not observed in the case of alloyed AgxAu25−x(SR)18 nanoparticles. This contrast can be attributed to the stability difference between CuxAu25−x(SR)18 and AgxAu25−x(SR)18 nanoparticles. These alloyed nanoparticles are promising candidates for applications such as catalysis.