Effect of Silver Alloying on the Vibrational Dynamics of Rod-Shaped Gold Nanoclusters

Abstract

Doping and alloying are effective strategies to improve the performance of metal nanoclusters, including photoluminescence and catalysis. The effect of doping on the electronic properties has been intensively investigated by experimental and theoretical methods, while the effect of foreign atoms on the mechanical properties of metal nanoclusters remains largely unknown. Here, we investigated the effect of silver alloying on the mechanical properties of rod-shaped gold nanoclusters by comparing the coherent vibrational dynamics of rod-shaped Au25 and AgxAu25–x (x ≤ 13). In both nanoclusters, we observed significant coherent vibrations in their transient absorption dynamics. The coherent vibrations exhibit a frequency of 0.9 THz and 0.65 THz for Au25 and AgxAu25–x (x ≤ 13), respectively, which are assigned to extension vibration modes of two rods. A detailed analysis of the coherent vibration indicates that the amplitude of the excited-state absorption is modulated in these two NCs. These results provide new insights into the photophysics of alloy metal nanoclusters.