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Significance Statement
Previous research has shown that protecting thiolate ligands play a prime role in optical and electrical properties of gold nanoclusters. The inclusion of an aromatic thiolate ligands on gold nanoclusters such as Au25(SR)18 can also control the catalytic properties it offers by simply using the ligand-substrate interaction.
In line with this, Gao Li and colleagues published an article in ACS Nano, reporting the synthesis, crystallization, electronic and chemical properties of an aromatic thiolate-protected [Au(SNap)18]–[TOA+] nanoclusters.
They introduced ceric oxide CeO2 powder to support Au25(SR)18 nanocrystals as they show higher catalytic performance compared to other oxide supports. An x-ray crystallographic analysis was conducted on the aromatic-thiolate-protected nanocystals before being characterized by using UV-vis absorption spectra.
The ligand effect at the thermal balance of Au25(SR)18 nanocrytals at a temperature of 800C under atmospheric conditions under an hour showed that the two aromatic thiolate-capped nanoclusters were more stable than the aliphatic nanoclusters when observed in UV-vis spectra of their toluene solutions.
Results when observing the antioxidant properties of aromatic thiolate-capped Au25(SNap)18 and aliphatic thiolate-capped Au25(SCH3Ph)18 nanoclusters in presence of hydrogen peroxide oxidant and a toluene-soluble oxidant showed that the presented aromatic thiolate-cappped nanoclusters had super antioxidation stability at longer period in presence of high concentration level of oxidant which was the opposite case in the aliphatic thiolate-capped nanoclusters as they oxidize easily to form a neutral and cationic nanoclusters. Density functional theory calculations also showed a higher level nanocluster’s frontier orbitals for [Au(SCH3)18]– compared to [Au25(SPh)18]– which suggest easy reaction of the former with oxidizing agents of hydrogen peroxide and toluene soluble oxidants.
The synthesized [Au(SNap)18]–[TOA+] nanoclusters share the same features of an icosahedral Au13 kernel and six dimeric Au25(SR)3 staple motifs found in crystal structures of [Au(SCH2CH2Ph)18] and Au25(SCH2CH3)18. The authors noted that the Au13 kernel in aromatic thiolate-capped Au(SNap)18 nanoclusters was responsible for the red-shift in UV-vis spectrum and the thiolate ligand is weakly bonded leading to an easy loss under an external force.
Despite a drop in recyclability and selectivity of the gold nanocrystal catalyst of Au25(SR)18/CeO2, its catalytic performance became nevertheless almost effective. Further results from the density functional theory calculations confirmed that the aromatic thiolate ligands increases reaction conversion rate and favors formation of heterocoupling product when compared with the aliphatic thiolate ligands. The consequences display good correlation with the experimental results.
The authors’ findings highlight the importance of ligand engineering for tailoring the electronic and catalytic properties of nanoclusters.
Journal Reference
Gao Li*1, Hadi Abroshan2, Chong Liu3, Shuo Zhuo2, Zhimin Li1, Yan Xie1, Hyung J. Kim2,4, Nathaniel L. Rosi3, Rongchao Jin*2. Tailoring the Electronic and Catalytic Properties of Au25 Nanoclusters via Ligand Engineering, ACS Nano 10 (2016) 7998-8005.
[expand title=”Show Affiliations”]- Gold Catalysis Research Centre, State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.
- Department of Chemistry,University of Pittsburgh, Pittsburgh, Pennsylvania 15213, United States.
- School of Computational Sciences, Korea Institute for Advanced Study, Seoul 02455, Korea.
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