Near-Infrared Dual-Emission of a Thiolate-Protected Au<sub>42</sub> Nanocluster: Excited States, Nonradiative Rates, and Mechanism
Xiaoying Xie, Ke-Qin Cheng, Wenkai Chen, Wenzuo Li, Qingzhong Li, Juan Han, Wei‐Hai Fang, Ganglong Cui
Abstract
Both DFT and TD-DFT methods are used to elaborate on the excited-state properties and dual-emission mechanism of a thiolate-protected Au42 nanocluster. A three-state model (S 0, S 1, and T 1 ) is proposed with respect to the results. The intersystem crossing (ISC) process from S 1 to T 1 benefits from a small reorganization energy due to the similar geometric structures of S 1 and T 1 . However, the ISC process is suppressed by relatively small spin–orbit coupling resulting from the similarity of the electronic structures of S 1 and T 1 . As a result of the counterbalance, the ISC rate is comparable with the fluorescence emission rate. In the T 1 state, the phosphorescence emission prevails the reverse ISC process back to the S 1 state. Taken together, fluorescence and phosphorescence are achieved simultaneously. The present work provides deep mechanistic insights to aid the rational design of NIR dual-emissive metal nanoclusters.