Role of ligand type on the geometric and electronic properties of Ag-Au bimetallic clusters

The interactions of a set of typical ligands (-CN, -COOH, -CH3, -OH, -SH, -NH3, -NO, -NO2, N(CH3)(2), and -PH3) with 13-atom icosahedral Ag-Au bimetallic clusters have been investigated by density functional theory (DFT) calculations. For the adsorption of all the ligands on the Ag-13 cluster, the adsorption strength follows the order of Ag-13-CN > Ag-13-SH > Ag-13-OH > Ag-13-COOH > Ag-13-CH3 > Ag-13-NO2> Ag-13-N(CH3)(2)> Ag-13-NO > Ag-13-PH3> Ag-13-NH3. Considering the composition effect, the adsorption strength of the ligands (X = -CN, -COOH, -CH3, and -NO2) on these clusters follows the order of Ag12Au-X > Ag-13-X > Au12Ag-X >Au-13-X. It is also found that the adsorption of the ligands (-NO, -N(CH13)(2), and -PH3) on the Au-rich clusters can modify their geometric properties, and even the icosahedral structure of Au-rich clusters has been transformed into the more stable truncated octahedral one upon adsorption. Our results show that the geometric and electronic properties of Ag-Au bimetallic clusters can be tuned by the ligand type, which can provide useful insights for the preparation of ligand-stabilized Ag-Au bimetallic clusters by chemical reduction. (C) 2014 Elsevier B.V. All rights reserved.