Au nanoclusters have found use in many contexts, but their structure and electronic properties have until recently remained elusive. Nanoparticles made of S and Au are known to occur in certain highly symmetric configurations, and there has long been a suspicion that there is a ‘divide and protect’ motif in the structures: a core of Au atoms protected by a bound S and Au ‘shell’. Last year, a group from Stanford University published high-resolution structures of a 102-atom Au cluster [Jadzinsky et. al., Science, doi: 10.1126/science.1148624] showing such a structure.
Now, one of the Stanford researchers has joined others from the University of Jyväskylä in Finland, Institut für Festkörperforschung in Germany, Georgia Institute of Technology in the US and Chalmers University in Sweden to put the idea on firmer theoretical grounds.
The team have employed supercomputers to solve the electronic structures of nanoclusters of varying sizes [Walter et. al., Proc. Nat. Acad. Sci. (2008) 105, 9157]. They found that the stability of the clusters rely on how the Au atoms donate their electrons; the number of valence electrons for each structure corresponds to closed shells like those found in noble gases. In the 102-atom cluster case, each atom donates one valence electron, 44 of which were tied up in thiolate bonds—leaving a neat 58 to form a full valence shell.
Publisher's noteThe author of the Opinion article ‘The Disappearance of Louis le Prince’ [Materials Today, 11 (7/8), 48] wishes to state that this was a work of fiction, and submitted to the writing competition as a creative writing story.