Single-electron charging and ultrafast dynamics of bimetallic Au_144−xAg_x(PET)₆₀ nanoclusters

Alloying is an important strategy in tailoring the functionality of materials. In metal nanoclusters (NCs), the introduction of a heterometal leads to alloy nanoclusters that often outperform the homometal ones in terms of the physical and chemical properties. In this work, a series of four M₁₄₄(PET)₆₀ alloy NCs (where, M = Au/Ag, PET = –SCH₂CH₂Ph) are synthesized and characterized. The silver doping into the homogold template (Au₁₄₄) leads to more prominent optical absorption features in the steady-state spectrum in the visible range. Femtosecond transient absorption spectroscopy reveals the effect of Ag doping on the electronic relaxation dynamics compared to Au₁₄₄ and the pump fluence independent dynamics. Electrochemical results reflect a narrowing of HOMO–LUMO gap (E_g) induced by Ag doping. A temperature dependence of the single-electron charging is also observed for the series of alloy NCs, in which the E_g values of the alloy NCs enlarge as the temperature decreases, which is characteristic of semiconducting behavior.