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Exposure to air transforms gold alloys into catalytic nanostructures

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Posted June 12, 2013
Transmission electron microscopy (TEM) images of the gold-indium alloy nanoparticles at room temperature. (A) shows an overview of multiple particles, while (D) shows a high-resolution TEM image of one nanoparticle's crystalline gold-indium core surrounded by the amorphous and catalytic oxide shell.

Transmission electron microscopy (TEM) images of the gold-indium alloy nanoparticles at room temperature. (A) shows an overview of multiple particles, while (D) shows a high-resolution TEM image of one nanoparticle’s crystalline gold-indium core surrounded by the amorphous and catalytic oxide shell.

Gold bars may signify great wealth, but the precious metal packs a much more practical punch when shrunk down to just billionths of a meter. Unfortunately, unlocking gold’s potential often requires complex synthesis techniques that produce delicate structures with extreme sensitivity to heat.

Now, scientists at the U.S. Department of Energy’s Brookhaven National Laboratory have discovered a process of creating uniquely structured gold-indium nanoparticles that combine high stability, great catalytic potential, and a simple synthesis process. The new nanostructures—detailed online June 10 in the Proceedings of the National Academy of Sciences—might enhance many different commercial and industrial processes, including acting as an efficient material for catalytic converters in cars.

“We discovered a room-temperature process that transforms a simple alloy into a nanostructure with remarkable properties,” said physicist Eli Sutter, lead author on the study. “By exposing the gold-indium alloy nanoparticles to air, ambient oxygen was able to drive an oxidation reaction that converted them into an active core-shell structure.”

Larger chunks of gold show the lowest chemical reactivity of all metals, but divided into discrete nanoparticles, gold can become a highly active chemical catalyst. But keeping gold in this active state is an ongoing challenge. Under even moderate heat, the tiny gold particles tend to sinter—fusing together into much larger pieces—and lose that crucial reactivity. Linking gold with other elements, however, can both increase durability and retain catalyst qualities—but only if the structure is perfect.

Read more at: Phys.org

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