Ag-Au nanoclusters: Structure and phase segregation

We present a systematic survey of unprotected Ag-Au nanoclusters prepared by inert gas aggregation. The clusters are initially fully and homogeneously alloyed, exhibiting icosahedral and decahedral structural motifs. Imaging using scanning transmission electron microscopy indicates that over a period of up to 2 yr, the nanoclusters undergo structural transitions into phase-segregated core-shell and Janus particles with Ag-Au cores and AgxO shells. Larger Janus particles undergo a ripening process which results in division into separate Ag-Au-rich and Ag2O-rich particles. We propose that oxidation of the Ag component and subsequent diffusion of AgxO are responsible for the observed phenomena. (C) 2011 American Institute of Physics. [doi:10.1063/1.3656244]