Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New Nanocrystals Show Potential for Cheap Lasers, New Lighting

12.05.2009
For more than a decade, scientists have been frustrated in their attempts to create continuously emitting light sources from individual molecules because of an optical quirk called "blinking," but now scientists at the University of Rochester have uncovered the basic physics behind the phenomenon, and along with researchers at the Eastman Kodak Company, created a nanocrystal that constantly emits light.

The findings, detailed online in today's issue of Nature, may open the door to dramatically less expensive and more versatile lasers, brighter LED lighting, and biological markers that track how a drug interact with a cell at a level never before possible.

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," says 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."

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

Krauss, an expert in nanocrystals, and Keith Kahen, senior principal scientist of Kodak and an expert in optoelectronic materials and devices, 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. Currently, different color laser light is created using different materials and processes, but with the new nanocrystals a single fabrication process can create any color laser. To alter the light color, an engineer needs only to alter the size of the nanocrystal, which Krauss says is a relatively simple task.

The same is true of what could one day be OLED's successor, says Krauss. Essentially, "painting" a grid of differently sized nanocrystals onto a flat surface could create computer displays as thin as paper, or a wall that lights a room in any desired color.

This research was funded by the Eastman Kodak Company, the U.S. Department of Energy, the National Science Foundation, the University of Rochester Center for Electronic Imaging Systems, the Cornell Center for Nanoscale Systems, the Office of Naval Research, and the Alexander von Humboldt Foundation.

About the University of Rochester
The University of Rochester (www.rochester.edu) is one of the nation’s leading private universities. Located in Rochester, N.Y., the University gives students exceptional opportunities for interdisciplinary study and close collaboration with faculty through its unique cluster-based curriculum. Its College, School of Arts and Sciences, and School of Engineering and Applied Sciences are complemented by the Eastman School of Music, Simon School of Business, Warner School of Education, Laboratory for Laser Energetics, Schools of Medicine and Nursing, and the Memorial Art Gallery.

Jonathan Sherwood | EurekAlert!
Further information:
http://www.rochester.edu

More articles from Physics and Astronomy:

nachricht Unraveling the nature of 'whistlers' from space in the lab
15.08.2018 | American Institute of Physics

nachricht Early opaque universe linked to galaxy scarcity
15.08.2018 | University of California - Riverside

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

Im Focus: The “TRiC” to folding actin

Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.

Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...

Im Focus: Lining up surprising behaviors of superconductor with one of the world's strongest magnets

Scientists have discovered that the electrical resistance of a copper-oxide compound depends on the magnetic field in a very unusual way -- a finding that could help direct the search for materials that can perfectly conduct electricity at room temperatur

What happens when really powerful magnets--capable of producing magnetic fields nearly two million times stronger than Earth's--are applied to materials that...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

2018 Work Research Conference

25.07.2018 | Event News

 
Latest News

Staying in Shape

16.08.2018 | Life Sciences

Diving robots find Antarctic seas exhale surprising amounts of carbon dioxide in winter

16.08.2018 | Earth Sciences

Protein droplets keep neurons at the ready and immune system in balance

16.08.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>