Excited-State Behaviors of M1Au24(SR)18 Nanoclusters: The Number of Valence Electrons Matters

Abstract

Doping is a quite useful strategy for probing the structure and properties of metal nanoclusters, but the effect of doping on the photodynamical properties is still not fully understood. Here, we reveal that the number of valence electrons plays a major role in determining the photodynamics of M1Au24(SR)18 nanoclusters. By carrying out temperature-dependent optical absorption, it is found that Cd doping enhances electron–phonon coupling while Hg doping does not significantly alter the coupling. Moreover, the relaxation dynamics of [M1Au24(SR)18]0 (M = Hg/Cd) nanoclusters show similar features to that of the negatively charged Au25 nanocluster. Specifically, the 8-electron M1Au24 (M = Cd/Hg) nanoclusters show a long excited-state lifetime (50−200 ns) and a weak picosecond relaxation, similar to the case of the anionic [Au25]− nanocluster. On the other hand, the non-8-electron MAu24 (M = Pd/Pt) nanoclusters show much more significant picosecond relaxation and thus much shorter excited-state lifetimes, which...