Electron localization in rod-shaped triicosahedral gold nanocluster.
basic_science · Level V
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- Record sourced from PubMed, PMID 28559316.
- Also identified by DOI 10.1073/pnas.1704699114 and PMC identifier 5474815.
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Abstract
Atomically precise gold nanocluster based on linear assembly of repeating icosahedrons (clusters of clusters) is a unique type of linear nanostructure, which exhibits strong near-infrared absorption as their free electrons are confined in a one-dimensional quantum box. Little is known about the carrier dynamics in these nanoclusters, which limit their energy-related applications. Here, we reported the observation of exciton localization in triicosahedral Au<sub>37</sub> nanoclusters (0.5 nm in diameter and 1.6 nm in length) by measuring femtosecond and nanosecond carrier dynamics. Upon photoexcitation to S<sub>1</sub> electronic state, electrons in Au<sub>37</sub> undergo ∼100-ps localization from the two vertexes of three icosahedrons to one vertex, forming a long-lived S<sub>1</sub>* state. Such phenomenon is not observed in Au<sub>25</sub> (dimer) and Au<sub>13</sub> (monomer) consisting of two and one icosahedrons, respectively. We have further observed temperature dependence on the localization process, which proves it is thermally driven. Two excited-state vibration modes with frequencies of 20 and 70 cm<sup>-1</sup> observed in the kinetic traces are assigned to the axial and radial breathing modes, respectively. The electron localization is ascribed to the structural distortion of Au<sub>37</sub> in the excited state induced by the strong coherent vibrations. The observed electron localization phenomenon provides unique physical insight into one-dimensional gold nanoclusters and other nanostructures, which will advance their applications in solar-energy storage and conversion.