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 Heating quantum matter: A novel view on topology
22.08.2017 | Université libre de Bruxelles

nachricht Engineering team images tiny quasicrystals as they form
18.08.2017 | Cornell University

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: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

Cholesterol-lowering drugs may fight infectious disease

22.08.2017 | Health and Medicine

Meter-sized single-crystal graphene growth becomes possible

22.08.2017 | Materials Sciences

Repairing damaged hearts with self-healing heart cells

22.08.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>