Time-Dependent Density Functional Theory Study on Higher Low-Lying Excited States of Au25(SR)18–

Abstract

Gold–thiolate clusters of [Au25(SR)18]− are known to show multiple photoluminescence below and above 2.0 eV. Although recent theoretical studies have clarified the lowest energy emission from the S1 state originating from the Au13 core, the relaxation mechanism responsible for the higher-energy emissions remains unclear. Here, we present a theoretical study on the higher low-lying excited states of [Au25(SR)18]− (R = Me, EtPh: methyl, phenylethyl) using time-dependent density functional theory computations to gain further insights. In particular, we focused on the S7 state because there is a large energy gap between S6 and S7 at the ground state geometry. Two minimum structures that are found for the S7 state of [Au25(SMe)18]− show different natures, namely, the Au sp-intraband and d-sp interband transitions. The intraband excited state has an energy close to the lower excited state, whereas the interband excited state has a substantial energy gap. Considering the underestimation of the excitation energy,...