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by Staff Writers
Vienna, Austria (SPX) Jun 01, 2012
Most people value large chunks of gold - but scientists at the Vienna University of Technology are interested in gold at the smallest possible scale, because single gold atoms are potentially the most reactive catalysts for chemical reactions. However, when gold atoms are placed on a surface they tend to ball up into tiny nuggets consisting of several atoms.
A team of surface scientists now managed to fix single gold atoms on special sites of an iron-oxide surface. This could open the door to more efficient catalysts, requiring less of the precious material.
Gold Does Not Like to Be Alone
So far, however, this could not be studied in detail. "If individual gold atoms are put on a surface, they usually cluster up, forming nanoparticles", says Gareth Parkinson, who oversaw the experiments in the research group of Professor Ulrike Diebold at the Institute for Applied Physics at the TU Vienna.
Hot Surfaces - Loose Atoms
A Good Place to Settle Down
At the points where the lines of oxygen atoms are close to each other, the gold atoms attach permanently without losing grip. Even if the surface is heated, the gold atoms stay put - only at 500 degrees celsius they start forming clusters.
"When a gold atom hits the iron oxide surface, it diffuses to one of the sites where it can be attached to the surface", says Gareth Parkinson. That way, many single gold atoms can be placed close to each other.
When a gold atom hits a position already occupied by another gold atom, however, the two bond and start moving across the surface, picking up additional gold atoms along the way. When they have reached a critical size of at least five atoms, they become immobile again and the miniature gold nugget comes to rest.
New Paths for New Research
The recent experiments will also help to advance theoretical research: the quantum mechanically complex bonding between single atoms and this particular surfaces provide an excellent test case for theoretical calculations of highly correlated electron systems.
Vienna University of Technology
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