Featured Research

from universities, journals, and other organizations

Remarkably Bright White Light Given Off When Diaper Rash Cream Concoction Is Heated To High Temperature

Date:
December 22, 2008
Source:
Duke University
Summary:
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. Physicists 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.

Glowing sulfur-doped ZnO phosphor emitting white light.
Credit: John Foreman (Redstone Arsenal)

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.

Related Articles


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.

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.


Story Source:

The above story is based on materials provided by Duke University. Note: Materials may be edited for content and length.


Cite This Page:

Duke University. "Remarkably Bright White Light Given Off When Diaper Rash Cream Concoction Is Heated To High Temperature." ScienceDaily. ScienceDaily, 22 December 2008. <www.sciencedaily.com/releases/2008/12/081218122238.htm>.
Duke University. (2008, December 22). Remarkably Bright White Light Given Off When Diaper Rash Cream Concoction Is Heated To High Temperature. ScienceDaily. Retrieved December 24, 2014 from www.sciencedaily.com/releases/2008/12/081218122238.htm
Duke University. "Remarkably Bright White Light Given Off When Diaper Rash Cream Concoction Is Heated To High Temperature." ScienceDaily. www.sciencedaily.com/releases/2008/12/081218122238.htm (accessed December 24, 2014).

Share This


More From ScienceDaily



More Matter & Energy News

Wednesday, December 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Tech's Next Step: Social Change

Tech's Next Step: Social Change

Reuters - Business Video Online (Dec. 23, 2014) — Technology is constantly changing lives but 100 firms have done more than most. As Joel Flyn reports a malaria diagnosis app, do-it-yourself architecture and camera glasses have recently won awards for driving social change. Video provided by Reuters
Powered by NewsLook.com
Google Releases 'Fully Functional' Driverless Car Prototype

Google Releases 'Fully Functional' Driverless Car Prototype

Newsy (Dec. 23, 2014) — Google hopes to have a driverless car on the roads in California in 2015. Video provided by Newsy
Powered by NewsLook.com
Hopes Ride High for Classic Car Boom in Havana

Hopes Ride High for Classic Car Boom in Havana

Reuters - Business Video Online (Dec. 23, 2014) — Cuba's vintage cars may see new roads ahead as restored diplomatic relations with the U.S. raise hopes of an American tourist boom to see the 1950s 'yank tanks'. Deborah Lutterbeck reports. Video provided by Reuters
Powered by NewsLook.com
Heads Up for Touch-Free Smartphone

Heads Up for Touch-Free Smartphone

Reuters - Business Video Online (Dec. 23, 2014) — A touch-free phone developed in Israel enables the mobility-impaired to operate smart phones with just a movement of the head. Suzannah Butcher reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins