New nanocrystal shows potential for cheaper and more versatile lasers

Washington, Mon, 11 May 2009 ANI

Washington, May 11 (ANI): Scientists at the University of Rochester, along with researchers at the Eastman Kodak Company, have created a nanocrystal that constantly emits light, which has potential for the development of cheaper and more versatile lasers and brighter LED lighting.

 

Many molecules, as well as crystals just a billionth of a meter in size, can absorb or radiate photons. But, they also experience random periods when they absorb a photon, but instead of the photon radiating away, its energy is transformed into heat.

 

These "dark" periods alternate with periods when the molecule can radiate normally, leading to the appearance of them turning on and off, or blinking.

 

"A nanocrystal that has just absorbed the energy from a photon has two choices to rid itself of the excess energy-emission of light or of heat," said Todd Krauss, associate professor of chemistry at the University of Rochester and lead author on the study.

 

"If the nanocrystal emits that energy as heat, you've essentially lost that energy," he added.

 

Krauss worked with engineers at Kodak and researchers at the Naval Research Laboratory and Cornell University to discover the new, non-blinking nanocrystals.

 

Krauss and Keith Kahen, senior principal scientist of Kodak, were exploring new types of low-cost lighting similar to organic light-emitting diodes, but which might not suffer from the short lifespans and manufacturing challenges inherent in these diodes.

 

Kahen, with help from Megan Hahn, a postdoctoral fellow in Krauss' laboratory, synthesized nanocrystals of various compositions.

 

Xiaoyong Wang, another postdoctoral fellow in Krauss laboratory, inspected one of these new nanocrystals and saw no evidence of the expected blinking phenomenon.

 

Remarkably, even after four hours of monitoring, the new nanocrystal showed no sign of a single blink-unheard of when blinks usually happen on a scale of miliseconds to minutes.

 

After a lengthy investigation, Krauss and Alexander Efros from the Naval Research Laboratory concluded that the reason the blinking didn't occur was due to the unusual structure of the nanocrystal.

 

Normally, nanocrystals have a core of one semiconductor material wrapped in a protective shell of another, with a sharp boundary dividing the two.

 

The new nanocrystal, however, has a continuous gradient from a core of cadmium and selenium to a shell of zinc and selenium.

 

That gradient squelches the processes that prevent photons from radiating, and the result is a stream of emitted photons as steady as the stream of absorbed photons.

 

With blink-free nanocrystals, Krauss believes lasers and lighting could be incredibly cheap and easy to fabricate. (ANI)

 



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