Quantum dots are made brighter

CHAMPAIGN, Ill., Sept. 25 (UPI) -- U.S. scientists have developed a method of increasing the fluorescence intensity of quantum dots by a factor of at least 108.

"We are using photonic crystals in a new way," said Brian Cunningham, a University of Illinois professor of electrical and computer engineering and corresponding author of the study. "We tune them to the specific wavelength of a laser used to stimulate the quantum dots, which couples the energy more efficiently and increases the brightness."

A quantum dot is a tiny piece of semiconductor material 2 to 10 nanometers in diameter. When illuminated with invisible ultraviolet light, a quantum dot will fluoresce with visible light.

Quantum dots normally give off light in all directions. However, because the researchers' quantum dots are located on a photonic crystal, the energy can be channeled in a preferred direction.

While the researchers report an enhancement of fluorescence intensity by a factor of up to 108 compared with quantum dots on an unpatterned surface, Cunningham said more recent, but unpublished, work has exceeded a factor of 550.

The study appeared in the journal Nature Nanotechnology.

Copyright 2007 by United Press International

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