Silver Nanoclusters Store Data

Hank Hogan

Every data cloud may someday have a silver lining. Researchers have demonstrated that fluorescing nanoclusters of two to eight silver atoms can store information, a phenomenon that may eventually find applications in optical data storage.

"This is at a very fundamental level at this point, and we're trying to understand the photophysics and photochemistry of this whole process," said Robert M. Dickson, an assistant professor of chemistry and biochemistry at Georgia Institute of Technology and a member of the team investigating the nanoclusters.

Silver oxide nanoclusters may find applications in optical storage. The clusters store information that can be retrieved as a fluorescence response. Photo by Gary Meek, courtesy of Georgia Institute of Technology.

The group deposits a film of silver less than 20 nm thick on a glass slide. The film forms islands on the slide that react with oxygen to create silver oxide. When exposed to light of wavelengths shorter than 520 nm, the silver oxide film forms nanoclusters that fluoresce strongly under light longer than 550 nm. Above that wavelength, no nanoclusters are produced.

Multiple fluorescence

The researchers, who reported the results of their study in the Jan. 5 issue of Science, have stored and retrieved information in the silver oxide clusters, including simple geometric shapes and the letter L. They wrote the data in the film using an argon-ion laser at 488 or 514.5 nm, and then read it out nondestructively using a filtered mercury lamp that produced wavelengths up to 550 nm.

Viewed under a microscope, the nanoclusters appear to glow in green, red and yellow. This multicolored fluorescence is characteristic of nanoclusters and might be due to the exposure time or the wavelength of light. If the hues of the fluorescence can be controlled, Dickson said, the result would be a medium that could store multiple bits of data in the same space.