Physicists Discover Structures Of Gold Nanoclusters

Using different experimental techniques, two separate and independent research groups in collaboration with a team from the Center for Computational Materials Science (CCMS) at the Georgia Institute of Technology, have unveiled the size-dependent evolution of structural and electronic structural motifs of gold nanoclusters ranging in size from 11 to 24 atoms. The experiments, in conjunction with the theoretical analysis performed by the Georgia Tech team, show near perfect agreement pertaining to the cluster structures occurring in the experiments. Understanding the electronic and geometric structures of gold nanoclusters is a key step towards understanding their behavior under different conditions, such as their use as nanocatalysts or in certain medical applications. The results appear in separate papers in The Physical Review B and in the journal ChemPhysChem. In its bulk form, gold is treasured for its property as a non-reactive metal. Its use in electronics, dentistry, jewelry and art, depends on this inertness. But at the nano scale, when gold clusters contain only a small number of atoms, gold shows very different properties, which exhibit chemical reactivity that make them potent catalysts. Because their chemical and physical properties depend greatly on their physical structures, significant efforts have been invested by scientists to determine what the most stable configurations of gold clusters are in this size range. Understanding this is of great importance for elucidating the chemical properties of these clusters and in research aiming to discover the physical patterns that govern how the clusters are put together. Between 2000 and 2002, a Georgia Tech team, led by Uzi Landman, director of CCMS, Regents’ and Institute professor, and Callaway chair of physics at Georgia Tech, predicted that negatively charged gold nanoclusters, up to 13 atoms in size, would exhibit two-dimensional, flat structures. The appearance of two-dimensional structures for such relatively large metal clusters is unique to gold, and the researchers showed that it is related to the strong relativistic effects for this metal. When these predictions were verified experimentally, research in Landman’s group and in other places focused on what happens when the nanoclusters are even larger. "We wanted to know, what happens after 13 atoms,” said Landman. “What happens when these clusters become three-dimensional and what is their structural motif?” For the past few years, scientists at the CCMS have made theoretical predictions about the structures of gold nanoclusters in the larger size range. Now, working with two independent experimental groups... Whole article: "www.sciencedaily.com":[ http://www.sciencedaily.com/releases/2007/01/070116131214.htm]

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