Gold resists tarnishing due to its chemical inertness, yet the precise reason remained unclear until now. Unlike silver, copper or iron, gold maintains its luster because it rarely reacts with surrounding molecules such as oxygen. This property suits jewelry but restricts its potential as a catalyst in chemical processes.
Scientists Matthew Montemore and Santu Biswas at Tulane University examined surface reconstruction, a process triggered when gold is cut to expose fresh atoms. These atoms rearrange into stable hexagonal patterns that lower their energy and limit further movement. Such reconstruction is uncommon in metals, prompting the team to test whether it explains gold’s resistance to oxidation.
Using supercomputer simulations of quantum atomic states, the researchers compared different surface arrangements and their reactions with oxygen. They found that splitting an oxygen molecule on a hexagonal gold surface demands high energy, making tarnish unlikely, whereas rectangular patterns require far less energy. Because hexagonal arrangements dominate, gold stays bright.
The link between atomic geometry, reconstruction and oxidation offers new ways to activate gold for catalysis, possibly by applying voltage in an electrical circuit to shift surface patterns. Experts note the findings could extend to nanoparticles and other molecules, though further experiments are needed to confirm practical applications.
