Upsetting the stability of super-small gold clusters generates multifaceted nanocrystals with potent catalytic properties
A*STAR researchers have devised a way to destabilize gold nanoclusters so that they form tiny atomic nuclei that then grow together into perfectly proportioned, 12-sided dodecahedron crystals. These unique polyhedra have energy-rich surfaces that can boost the catalytic efficiency of important chemical reactions and serve as potential adsorption sites for targeted sensor devices.
Typically, gold nanoclusters are prepared by chemically reducing a gold–sulfur precursor in the presence of an organic stabilizing agent. This procedure creates a symmetric core of gold atoms protected by a thin layer of surface groups known as thiolates. Researchers have developed many techniques for varying the size of the nanoclusters to tune their chemical and physical properties. But destabilizing gold-thiolate bonds to enable further transformations into polyhedral crystals has proved more challenging.
To tackle this issue, an interdisciplinary team led by Yong-Wei Zhang from the Institute of High Performance Computing and Ming-Yong Han from the Institute of Materials Research and Engineering at A*STAR in Singapore investigated strategies to destabilize gold clusters by oxidizing the surface-protecting thiolates. While promising, this approach has its risks: previous attempts using ozone destabilization agents produced uncontrolled aggregation of gold atoms into macroscopic precipitates.
The researchers examined if switching to a milder hydrogen peroxide destabilization agent would give more favorable results. They first synthesized a solution of 25-atom gold clusters stabilized by outer layers of bovine serum albumin (BSA). When hydrogen peroxide was added to the mixture, the team’s mass spectrometry instruments showed that covalent gold–sulfur bonds slowly ruptured.
This peroxide-based destabilization initially produced smaller 11-atom gold clusters. But after sitting for nearly a week at room temperature, these clusters transformed into remarkable dodecahedron shapes (see image).
High-resolution scanning electron microscopy revealed that every facet on the dodecahedra had identical crystallographic orientations — a rare distribution of gold atoms known as a  facet. Density functional theory calculations initiated by co-author Guijian Guan showed that these unusual structures arise when amino acids liberated from BSA during the destabilization reaction attach to the nanoparticles and promote growth in every crystal direction except the  orientation.
Guan explains that because  facets have the highest surface energies among standard gold facets, they present strong attractive forces to incoming molecules — a phenomenon that improves the catalytic capacity due to a stronger binding affinity to target molecules. “For example, we observed a four-fold enhancement in catalytic ability for our dodecahedra compared to gold nanoparticles during the reduction of 4-nitrophenol to 4-aminophenol,” he notes.
The A*STAR-affiliated researchers contributing to this research are from the Institute of High Performance Computing and the Institute of Materials Research and Engineering. More information about the group’s research can be found on the Engineering Mechanics webpage.
 Guan, G., Liu, S., Cai, Y., Low, M., Bharathi, M. S. et al. Destabilization of gold clusters for controlled nanosynthesis: From clusters to polyhedra. Advanced Materials 26, 3427–3432 (2014).
Game-changing finding pushes 3D-printing to the molecular limit
20.06.2018 | University of Nottingham
Creating a new composite fuel for new-generation fast reactors
20.06.2018 | Lobachevsky University
In a recent publication in the renowned journal Optica, scientists of Leibniz-Institute of Photonic Technology (Leibniz IPHT) in Jena showed that they can accurately control the optical properties of liquid-core fiber lasers and therefore their spectral band width by temperature and pressure tuning.
Already last year, the researchers provided experimental proof of a new dynamic of hybrid solitons– temporally and spectrally stationary light waves resulting...
Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...
Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.
Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...
The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.
Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.
An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.
Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...
13.06.2018 | Event News
08.06.2018 | Event News
05.06.2018 | Event News
21.06.2018 | Earth Sciences
21.06.2018 | Life Sciences
21.06.2018 | Earth Sciences