More light news--nanoclusters composed of 2-8 silver atoms could be the basis for a new type of optical data storage. Fluorescent emissions from the clusters could potentially also be used in biological labels and electroluminescent displays. According to Robert M. Dickson, assistant professor of chemistry and biochemistry at Georgia Institute of Technology, the Ag₂O nanoparticles "have a remarkable new property: when you shine blue light with a wavelength less than 520nm onto them, you switch on their ability to fluoresce." The researchers produced films less than 20nm thick of silver oxide on a glass slide, then exposed portions of the film to light in the blue spectrum. The light chemically reduces particles near the film's surface, partially producing clusters of silver atoms. When exposed to longer wavelength green light, the clusters fluoresce strongly, emitting red light visible to the naked eye. Silver oxide particles not photoactivated by the blue light do not fluoresce. Looking at individual particles with a microscope, "you can see green emission, then red emission, then yellow emission all from the same particle," says Dickson. "Not only are you generating fluorescence, but you presumably are also changing the size and/or geometry of the cluster, causing it to emit different wavelengths."

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