The Origin of the Photoluminescence Enhancement of Gold-Doped Silver Nanoclusters: The Importance of Relativistic Effects and Heteronuclear Gold-Silver Bonds

The weak photoluminescence of silver nanoclusters prevents their broad application as luminescent nanomaterials. Recent experiments, however, have shown that gold doping can significantly enhance the photoluminescence intensity of Ag-29 nanoclusters but the molecular and physical origins of this effect remain unknown. Therefore, we have computationally explored the geometric and electronic structures of Ag-29 and gold-doped Ag29-xAux (x=1-5) nanoclusters in the S-0 and S-1 states. We found that 1)relativistic effects that are mainly due to the Au atoms play an important role in enhancing the fluorescence intensity, especially for highly doped Ag26Au3, Ag25Au4, and Ag24Au5, and that 2)heteronuclear Au-Ag bonds can increase the stability and regulate the fluorescence intensity of isomers of these gold-doped nanoclusters. These novel findings could help design doped silver nanoclusters with excellent luminescence properties.