‘Caged’ Nanoparticle Mimics Japanese Fishing Float

AsianScientist (Jun. 23, 2016) - Researchers have designed a unique copper-silver nanoparticle structure that has a core of one element surrounded by a ‘cage’ of the other element. The nanoparticles very much resemble the ukidama, which are Japanese glass fishing floats traditionally covered with rope.

“The ukidama is a unique structure, which means that it can likely give us unique properties,” said first author Dr. Panagiotis Grammatikopoulos from the Okinawa Institute of Science and Technology (OIST) Graduate University in Japan. “The idea is that now that we know about this structure we may be able to fine tune it to our applications.”

The researchers made the discovery of the ukidama-like structure when sputtering copper and silver atoms simultaneously, but independently, through a magnetron-sputtering system at high temperatures. As the atoms cooled, they combined into bi-metallic nanoparticles.

During the sputtering process, researchers could control the ratio of silver to copper, with the rate of power with which the atoms were sputtered. They found that the ukidama structure was possible when the copper was the dominant element, since silver atoms have a higher tendency to diffuse on the nanoparticle surface. From their experimental findings, the team was able to create simulations like the one below that clearly show how the ukidama nanoparticles form.