Structural and optical properties of the naked and passivated Al5Au5 bimetallic nanoclusters.

The structural and optical properties of both the naked and passivated bimetallic Al5Au5 nanoclusters have been analyzed based on data obtained from ab initio density functional theory and quantum molecular dynamics simulations. It has been found that the Al5Au5 nanocluster possesses a hollow shaped minimum energy structure with segregated Al and Au layered domains, the former representing the electrophilic domain and the latter the nucleophilic domain. In particular, it has been shown that alkali metal cations attach in the nucleophilic domain and hop from one Au site to the next one in the picoseconds time scale, while anions are bound tightly to the Al atoms of the electrophilic domain. Simulating annealing studies are very suggestive of the proneness of the nanocluster towards coalescence into large cluster units, when the cluster is left unprotected by appropriate ligands. Further passivation studies with NaF salt suggest, nonetheless, the possibility of the isolation of the Al5Au5 cluster in molten salts or ionic liquids.