The second finding, which appears in the February 1 edition of the same journal, answers the question of what happens when a nanowire of gold is pulled in the presence of oxygen. In these studies Landman, Postdoctoral Fellow Chun Zhang and Senior Research Scientist Robert Barnett used first-principles simulations and quantum electrical transport calculations. They found that oxygenated gold nanowires exhibit different properties, depending on whether the oxygen is incorporated in a molecular form or as individual atoms. Indeed, some of these theoretical results offer a new interpretation of recent laboratory experiments on oxygenated gold nanowires.
In the case of incorporation of molecular oxygen into the gold nanowire, the simulations revealed that the nanowires can be stretched to a significantly longer extent than pure gold nanowires in other words, the adsorbed oxygen molecule serves as a reinforcing clamp.
Furthermore, the simulations predict that up to a certain stretching distance (typically up to wires that resemble a stretched necklace of about six gold atoms and an embedded oxygen molecule), such nanowires will conduct electrons similar to a pure gold nanowire. These results have been confirmed experimentally. Moreover, the simulations predict that oxygenated gold nanowires extended beyond a length of about six gold atoms become insulating. The conducting state can be restored by a slight contraction of the wire, thus allowing distance - dependent sensitive metal-to-insulator nano-switching.
When individual oxygen atoms, rather than an oxygen molecule, are incorporated in the gold nanowire, the elongation range was found to be limited and the electrical conductance was predicted to be lower than in the previous case of
|Contact: David Terraso|
Georgia Institute of Technology