Unraveling the atomic structure, ripening behavior, and electronic structure of supported Au<sub>20</sub> clusters.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 31922009.
- Also identified by DOI 10.1126/sciadv.aay4289 and PMC identifier 6941914.
- Licence recorded as CC BY-NC.
- Because redistribution is not established, this page shows the abstract only. Follow the links below for the full text.
Abstract
The free-standing Au<sub>20</sub> cluster has a unique tetrahedral shape and a large HOMO-LUMO (highest occupied molecular orbital-lowest unoccupied molecular orbital) gap of around 1.8 electron volts. The "magic" Au<sub>20</sub> has been intensively used as a model system for understanding the catalytic and optical properties of gold nanoclusters. However, direct real-space ground-state characterization at the atomic scale is still lacking, and obtaining fundamental information about the corresponding structural, electronic, and dynamical properties, is challenging. Here, using cluster-beam deposition and low-temperature scanning tunneling microscopy, atom-resolved topographic images and electronic spectra of supported Au<sub>20</sub> clusters are obtained. We demonstrate that individual size-selected Au<sub>20</sub> on ultrathin NaCl films maintains its pyramidal structure and large HOMO-LUMO gap. At higher cluster coverages, we find sintering of the clusters via Smoluchowski ripening to Au<sub>20<i>n</i></sub> agglomerates. The evolution of the electron density of states deduced from the spectra reveals gap reduction with increasing agglomerate size.