A potential way to store data in the form of fluorescing thin films of silver oxide has been reported by researchers at the Georgia Institute of Technology (Atlanta, GA). Because the fluorescing particles – nanometer-size clusters of silver embedded in the silver oxide – are so tiny, devices incorporating the technology could, in principle, pack a tremendous amount of data into a small space.

Thin layers of silver oxide are initially non-fluorescent. But, as described by Georgia Tech chemist Robert M. Dickson and colleagues in the Jan. 5 issue of Science, it is possible to turn on fluorescence in these layers by exposing them to light beams of wavelengths less than 520 nm. The fluorescence comes from nanoclusters of silver atoms, which form by photoreduction in much the same way as silver particles form in photographic film emulsions. Once they are photoactivated, the silver oxide layers exhibit multicolored fluorescence under excitation by both blue (450 to 480 nm) and green (510 to 550 nm) light. Blue excitation causes the layer to fluoresce in multicolored hues, but only intermittently. However, green excitation results in brighter and steadier red fluorescence.

Taking advantage of these properties, the Georgia Tech researchers have written data to their thin silver oxide films by first photo-exciting them with blue light. Then they have nondestructively read the data by monitoring the strong red fluorescence that emanates from the films under green light excitation. (Because the green light wavelength is longer than 520 nm, it does not alter the photochemical properties of the films.)

This work is still in the laboratory stage. But according to their Science paper, the Georgia Tech investigators believe that their "caged" fluorescent nanoparticles of silver "could be rapidly switched on and used, for example, as nanoscopic optical storage elements or as probes in living systems."