Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Duke researchers coax bright white light from unexpected source

Abstract:
Duke University and United States Army scientists have found that a cheap and nontoxic sunburn and diaper rash preventative can be made to produce brilliant light best suited to the human eye.

Duke adjunct physics professor Henry Everitt, chemistry professor Jie Liu and their graduate student John Foreman have discovered that adding sulfur to ultra-fine powders of commonplace zinc oxide at about 1,000 degrees centigrade allows the preparation to convert invisible ultraviolet light into a remarkably bright and natural form of white light.

Duke researchers coax bright white light from unexpected source

DURHAM, NC | Posted on December 18th, 2008

They are now probing the solid state chemistry and physics of various combinations of those ingredients to deduce an optimal design for a new kind of illumination. Everitt and Liu have applied for a patent on using the preparations as a light source. "Our target would be to help make solid state lighting with better characteristics than current fluorescent ones," said Everitt, who also works with Foreman at the Army's Redstone Arsenal in Huntsville, Ala.

The researchers said they are producing white light centered in the green part of the spectrum by forming the sulfur-doped preparation into a material called a phosphor. The phosphor converts the excited frequencies from an ultraviolet light emitting diode (LED) into glowing white light.

Nanometer-diameter zinc oxide powders are being prepared by Liu's research group, which focuses on the chemistry of nanomaterials. He is Duke's Jerry G. and Patricia Crawford Hubbard Professor of Chemistry. They are then being tested at the Aviation and Missile Research, Development and Engineering Center at Redstone Arsenal by Everitt, an Army senior research scientist, and Foreman, an Army research physicist.

The researchers are also exploring using electricity alone to trigger the visible emissions without need for an ultraviolet light trigger.

The Army has selected the project for priority funding through a competitive In-house Laboratory Independent Research program because of its potential advantages as an energy efficient and safe illumination source.

"One of the objectives is to give soldiers efficient lighting that doesn't run their batteries down," Everitt said. "They need efficiency, brightness, longevity and ruggedness, and this helps with all of those things."

Existing commercial LEDs are already rugged enough to be used in bumper-mounted brake lights, Everitt said.

"They are good enough for decoration and for use in traffic lights, but they don't make good reading lights because they are not of a white color that our eyes use best," Liu said. White LEDs on the market now are costly, short-lived and not truly white, the researchers added.

A compound that can be used on faces or babies' bottoms also has major safety advantages over fluorescent bulbs, which happen to contain toxic mercury. "If a fluorescent bulb gets broken in the course of battle, it exposes soldiers to that mercury in addition to its shattered glass," Everitt said.

"I think the biggest payoff for the general public will ultimately be in future energy crises we're certainly going to face," Everitt added. "If we can have more efficient lighting it will reduce our energy requirements."

Scientists have long known that zinc oxide can itself serve as a solid state ultraviolet light source. They have also known that adding sulfur allows it to emit some white light. But Liu, Everitt and Foreman are investigating how nanostructuring and doping improves its performance.

The introduced sulfur is thought to boost wavelength conversions from ultraviolet to visible wavelengths by serving as an "impurity" that changes the chemistry and physics of the zinc oxide in ways the Duke researchers are still probing.

Most scientists consider such impurities "defects" that interfere with zinc oxide's ability to produce a stronger ultraviolet light, they said. But "we love the defects that other people hate," Everitt said. "That's been the gift of nanostructured doped zinc oxide, emitting what your eye expects white light to look like."

In a report published May 10, 2006, in the research journal Nano Letters, Foreman, Everitt, Liu and co-researchers first disclosed they could induce a formulation of zinc oxide shaped into nanowires to absorb light from an ultraviolet laser and re-emit it as a "broadband visible emission of unprecedented brightness." The white light component was more than 1,000 times brighter than the ultraviolet component, they reported.

In a followup report, published July 2, 2007, in the journal Applied Physics Letters, the Duke researchers initiated what they expect to be a series of published papers exploring how various alterations affect the white light emissions.

"We've learned something about what makes the white light conversion happen, and what makes it happen so efficiently," Everitt said. The Duke team has already achieved efficiencies as high as 80 percent. But there are still technical issues to resolve tied to the operating temperatures of the phosphors and the power from the underlying ultraviolet LED.

"Our challenge has been getting a foundational understanding so we can understand what is physically possible and how close we are to achieving it," Everitt said.

Zinc oxide would be both a less-toxic and cheaper light source than the combinations used in today's commercial LEDs -- gallium nitride and cerium-doped yttrium oxide, they said. Cerium-doped yttrium oxide is also used in today's mercury-containing fluorescent bulbs, Everitt added.

Liu's lab originally stumbled on to the light emitting potential of sulfur-doped zinc oxide while studying its electronic conductivity. "We just lit it up with an ultraviolet laser and -- whammo -- there was a lot of white light coming out," Everitt said.

####

For more information, please click here

Contacts:
Monte Basgall

919-681-8057

Copyright © Duke University

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

Ultracold atom waves may shed light on rogue ocean killers: Rice quantum experiments probe underlying physics of rogue ocean waves April 27th, 2017

Looking for the quantum frontier: Beyond classical computing without fault-tolerance? April 27th, 2017

Metal nanoparticles induced visible-light photocatalysis: Mechanisms, applications, ways of promoting catalytic activity and outlook April 27th, 2017

Arrowhead Pharmaceuticals to Webcast Fiscal 2017 Second Quarter Results April 27th, 2017

Govt.-Legislation/Regulation/Funding/Policy

Ultracold atom waves may shed light on rogue ocean killers: Rice quantum experiments probe underlying physics of rogue ocean waves April 27th, 2017

Metal nanoparticles induced visible-light photocatalysis: Mechanisms, applications, ways of promoting catalytic activity and outlook April 27th, 2017

Graphene holds up under high pressure: Used in filtration membranes, ultrathin material could help make desalination more productive April 24th, 2017

Nanoparticle vaccine shows potential as immunotherapy to fight multiple cancer types April 24th, 2017

Discoveries

Ultracold atom waves may shed light on rogue ocean killers: Rice quantum experiments probe underlying physics of rogue ocean waves April 27th, 2017

Looking for the quantum frontier: Beyond classical computing without fault-tolerance? April 27th, 2017

Metal nanoparticles induced visible-light photocatalysis: Mechanisms, applications, ways of promoting catalytic activity and outlook April 27th, 2017

Geoffrey Beach: Drawn to explore magnetism: Materials researcher is working on the magnetic memory of the future April 25th, 2017

Announcements

Ultracold atom waves may shed light on rogue ocean killers: Rice quantum experiments probe underlying physics of rogue ocean waves April 27th, 2017

Looking for the quantum frontier: Beyond classical computing without fault-tolerance? April 27th, 2017

Metal nanoparticles induced visible-light photocatalysis: Mechanisms, applications, ways of promoting catalytic activity and outlook April 27th, 2017

Arrowhead Pharmaceuticals to Webcast Fiscal 2017 Second Quarter Results April 27th, 2017

Patents/IP/Tech Transfer/Licensing

Forge Nano 2017: 1st Quarter Media Update April 20th, 2017

Making Batteries From Waste Glass Bottles: UCR researchers are turning glass bottles into high performance lithium-ion batteries for electric vehicles and personal electronics April 19th, 2017

'Neuron-reading' nanowires could accelerate development of drugs for neurological diseases April 12th, 2017

Laser activated gold pyramids could deliver drugs, DNA into cells without harm: Microstructures create temporary pores in cells March 27th, 2017

Military

Ultracold atom waves may shed light on rogue ocean killers: Rice quantum experiments probe underlying physics of rogue ocean waves April 27th, 2017

Nano-SPEARs gently measure electrical signals in small animals: Rice University's tiny needles simplify data gathering to probe diseases, test drugs April 17th, 2017

New technology could offer cheaper, faster food testing: Specialized droplets interact with bacteria and can be analyzed using a smartphone April 7th, 2017

Teri Odom and Richard Van Duyne Honored by Department of Defense: Each will receive $3 million over five years to conduct high-risk, high-payoff research March 31st, 2017

Photonics/Optics/Lasers

Using light to propel water : With new method, MIT engineers can control and separate fluids on a surface using only visible light April 25th, 2017

Method improves semiconductor fiber optics, paves way for developing devices April 16th, 2017

AIM Photonics Presents Cutting-Edge Integrated Photonics Technology Developments to Packed House at OFC 2017, the Optical Networking and Communication Conference & Exhibition April 11th, 2017

Photonics breakthough paving the way for improved wireless communication systems: The work could bolster the wireless revolution underway with efficiencies several orders of magnitude April 5th, 2017

Research partnerships

California Research Alliance by BASF establishes more than 25 research projects in three years April 26th, 2017

Better living through pressure: Functional nanomaterials made easy April 19th, 2017

Shedding light on the absorption of light by titanium dioxide April 14th, 2017

AIM Photonics Presents Cutting-Edge Integrated Photonics Technology Developments to Packed House at OFC 2017, the Optical Networking and Communication Conference & Exhibition April 11th, 2017

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project