Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers Find Controls to Gold Nanocatalysis

10.08.2006
Researchers at the Georgia Institute of Technology have made a discovery that could allow scientists to exercise more control over the catalytic activity of gold nanoclusters.

The finding – that the dimensionality and structure, and thus the catalytic activity, of gold nanoclusters changes as the thickness of their supporting metal-oxide films is varied – is an important one in the rapidly developing field of nanotechnology. This and further advances in nanocatalysis may lead to lowering the cost of manufacturing materials from plastics to fertilizers. The research appeared in the July 21, 2006 issue of the journal Physical Review Letters.

"We've been searching for methods for controlling and tuning the nanocatalytic activity of gold nanoclusters,” said Uzi Landman, director of the Center for Computational Materials Science and Regents’ professor and Callaway chair of physics at Georgia Tech. “I believe the effect we discovered, whereby the structure and dimensionality of supported gold nanoclusters can be influenced and varied by the thickness of the underlying magnesium-oxide film may open new avenues for controlled nanocatalytic activity,” he said.

Landman’s research group has been exploring the catalytic properties of gold, which is inert in its bulk form, for about seven years. In 1999, along with the experimental group of Ueli Heiz and Wolf-Dieter Schneider at the University of Lausanne, Landman’s group showed that gold exhibits remarkable catalytic capabilities to speed the rate of chemical reactions if it is clustered in groups of eight to about two dozen atoms in size.

Last year in the journal Science, the teams of Landman and Heiz (now at the Technical University of Munich) showed that this catalytic activity involves defects, in the form of missing oxygen atoms, in the catalytic bed on which the gold clusters rest. These defect sites, referred to as F-centers, serve as sites for the gold to anchor itself, giving the gold clusters a slight negative charge. The charged gold transfers an electron to the reacting molecules, weakening the chemical bonds that keep them together. Once the bond is sufficiently weakened, it may be broken, allowing reactions to occur between the adsorbed reactants.

Now Landman’s group has found that by using a thin catalytic bed with a thickness of up to 1 nanometer (nm), or 4-5 layers, of magnesium oxide, one may activate the gold nanoclusters which may act then as catalysts even if the bed is defect-free. A model reaction tested in these studies is one where carbon monoxide and molecular oxygen combine to form carbon dioxide, even at low temperatures. In these reactions, the bond connecting the two atoms in the adsorbed oxygen molecule weakens, thus, promoting the reaction with CO.

In this study, Landman and company simulated the behavior of gold nanoclusters containing eight, sixteen and twenty atoms when placed on catalytic beds of magnesium oxide with a molybdenum substrate supporting the magnesium oxide film. Quantum mechanical calculations showed that when the magnesium oxide film was greater than 5 layers or 1 nm in thickness, the gold cluster kept its three-dimensional structure. However, when the film was less than 1nm, the cluster changed its structure and lied flat on the magnesia bed –wetting and adhering to it.

The gold flattens because the electronic charge from the molybdenum penetrates through the thin layer of magnesium oxide and accumulates at the region where the gold cluster is anchored to the magnesium oxide. With a negative charge underneath the gold nanocluster, its attraction to the molybdenum substrate, located under the magnesia film, causes the cluster to collapse.

"It’s the charge that controls the adhesive strength of gold to the magnesia film, and at the same time it makes gold catalytically active,” said Landman. “When you have a sufficiently thin layer of magnesium oxide, the charge from the underlying metal penetrates through – all the way to the interface of the gold cluster.”

In the previous experimental studies, defects in the magnesium oxide were required to bring about charging of the adsorbed clusters.

"Until now, the metal substrate was regarded only as an experimental necessity for growing the magnesium oxide films on top of it. Now we found that it can be used as a design feature of the catalytic system. This field holds many surprises,” said Landman.

Landman’s group is currently undertaking further explorations into possibilities to regulate the charge, and hence the catalytic activity, in gold nanocatalytic systems.

Landman and Heiz’s book titled “Nanocatalysis” is scheduled to be published this month.

The current research was performed at the Center for Computational Materials Science by postdoctoral fellows Davide Ricci and Angelo Bongiorno under the supervision of Landman. The research team also included Dr. Gianfranco Pacchioni, a colleague from the University of Milano.

The research appearing in the journal Science in 2005 was led by Landman and Heiz with Research Scientist Bokwon Yoon of the Center for Computational Materials Science as lead author.

The Georgia Institute of Technology is one of the nation's premiere research universities. Ranked ninth among U.S. News & World Report's top public universities, Georgia Tech educates more than 17,000 students every year through its Colleges of Architecture, Computing, Engineering, Liberal Arts, Management and Sciences. Tech maintains a diverse campus and is among the nation's top producers of women and African-American engineers. The Institute offers research opportunities to both undergraduate and graduate students and is home to more than 100 interdisciplinary units plus the Georgia Tech Research Institute. During the 2004-2005 academic year, Georgia Tech reached $357 million in new research award funding. The Institute also maintains an international presence with campuses in France and Singapore and partnerships throughout the world.

David Terraso | EurekAlert!
Further information:
http://www.gatech.edu
http://www.gatech.edu/news-room/release.php?id=1078

More articles from Physics and Astronomy:

nachricht New type of smart windows use liquid to switch from clear to reflective
14.12.2017 | The Optical Society

nachricht New ultra-thin diamond membrane is a radiobiologist's best friend
14.12.2017 | American Institute of Physics

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Plasmonic biosensors enable development of new easy-to-use health tests

14.12.2017 | Health and Medicine

New type of smart windows use liquid to switch from clear to reflective

14.12.2017 | Physics and Astronomy

BigH1 -- The key histone for male fertility

14.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>