Free Newsletters - Space News - Defense Alert - Environment Report - Energy Monitor
. 24/7 Space News .




TECH SPACE
Light-emitting triangles may have applications in optical technology
by Katrina Voss for PSU News
Philadelphia PA (SPX) Feb 08, 2013


Triangular single layers of tungsten disulfide have been synthesized by Penn State researchers. The edges of the triangles exhibit extraordinary photoluminescence, while the interior area does not. The photoluminescent signal disappears as the number of layers increases. These triangular structures may have potential applications in optical technology; for example, for use in light detectors and lasers. Credit: Terrones lab, Penn State Universtiy.

For the first time, scientists have created single layers of a naturally occurring rare mineral called tungstenite, or WS2. The resulting sheet of stacked sulfur and tungsten atoms forms a honeycomb pattern of triangles that have been shown to have unusual light-emitting, or photoluminescent, properties.

According to team leader Mauricio Terrones, a professor of physics and of materials science and engineering at Penn State, the triangular structures have potential applications in optical technology; for example, for use in light detectors and lasers. The results of the research will be published in a print edition of the journal NANO Letters.

Terrones explained that creating monolayers -- single, one-atom-thick layers -- is of special interest to scientists because the chemical properties of minerals and other substances are known to change depending on their atomic thickness, opening the door to potentially useful applications of multi-layered materials of various thicknesses.

In previous research, scientists had accomplished the feat of making a monolayer of graphene -- a substance similar to the graphite found in pencil leads. "The technique these researchers used was tedious, but it worked," Terrones said. "They basically removed, or exfoliated, the graphene, layer by layer, with Scotch tape, until they got down to a single atom of thickness."

Now, for the first time, Terrones and his team have used a controlled thermal reduction-sulfurization method -- or chemical vapor deposition -- to accomplish the same feat with a rare mineral called tungstenite. The scientists began by depositing tiny crystals of tungsten oxide, which are less than one nanometer in height, and they then passed the crystals through sulfur vapor at 850 degrees Celsius.

This process led to individual layers -- or sheets -- composed of one atom in thickness. The resulting structure -- called tungsten disulfide -- is a honeycomb pattern of triangles consisting of tungsten atoms bonded with sulfur atoms.

"One of the most exciting properties of the tungsten disulfide monolayer is its photoluminescence," Terrones said. Terrones explained that photoluminescence occurs when a substance absorbs light at one wavelength and re-emits that light at a different wavelength. The property of photoluminescence also occurs in certain bioluminescenent animals such as angler fish and fireflies.

"One interesting discovery from our work is the fact that we see the strongest photoluminescence at the edges of the triangles, right where the chemistry of the atoms changes, with much less photoluminescence occurring in the center of the triangles," Terrones said.

"We also have found that these new monolayers luminesce at room temperature. So no special temperature requirements are needed for the material to exhibit this property."

Co-author Vincent H. Crespi, Distinguished Professor of Physics, Chemistry, and Materials Science and Engineering at Penn State, added, "The images of the photoluminescence are beautiful; the triangles light up all around their edges like little holiday ornaments -- holiday ornaments with potentially transformative, long-term applications in nano-optics."

The research has many potential applications in the fields of optical light detection, the production of light-emitting diodes, and even laser technology. The researchers also plan to try the chemical-vapor-deposition technology to grow innovative monolayers using other layered materials with potentially useful applications.

In addition to Terrones and Crespi, other researchers who contributed to this study include Humberto R. Gutierrez, an assistant professor at the University of Louisville; Nestor Perea-Lopez and Ana Laura Elias, research associates at Penn State; Ayse Berkdemir and Ruitao Lv, posdoctoral fellows at Penn State; Bei Wang and Yuanxi Wang, graduate students at Penn State; and Florentino Lopez-Urias and Humberto Terrones, visiting professors at Penn State. Support for this research comes primarily from the U.S. Army Research Office and, in part, from the Penn State Center for Nanoscale Science.

.


Related Links
Penn State
Space Technology News - Applications and Research






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





TECH SPACE
Penn Research Shows Mechanism Behind Wear at the Atomic Scale
Philadelphia PA (SPX) Feb 04, 2013
Wear is a fact of life. As surfaces rub against one another, they break down and lose their original shape. With less material to start with and functionality that often depends critically on shape and surface structure, wear affects nanoscale objects more strongly than it does their macroscale counterparts. Worse, the mechanisms behind wear processes are better understood for things like ... read more


TECH SPACE
Building a lunar base with 3D printing

US, Europe team up for moon fly-by

Russia to Launch Lunar Mission in 2015

US, Europe team up for moon fly-by

TECH SPACE
Sampling Several Rock Targets

Mapping Mars

Weekend Test on Mars Was Preparation to Drill a Rock

AAS Division For Planetary Sciences Issues Statement On Mars 2020 Program

TECH SPACE
Supersonic skydiver even faster than thought

Ahmadinejad says ready to be Iran's first spaceman

Iran's Bio-Capsule Comes Back from Space

A Hero For Humankind: Yuri Gagarin's Spaceflight

TECH SPACE
Reshuffle for Tiangong

China to launch 20 spacecrafts in 2013

Mr Xi in Space

China plans manned space launch in 2013: state media

TECH SPACE
NASA to Send Inflatable Pod to International Space Station

ISS to get inflatable module

ESA workhorse to power NASA's Orion spacecraft

Competition Hopes To Fine Tune ISS Solar Array Shadowing

TECH SPACE
Arianespace Launches Six Globalstar Birds Using Starsem Soyuz

Final checkout underway for the Starsem Soyuz launch with Globalstar spacecraft

Zenit Engine Worked Normally

NASA Launches Rocket from Wallops Flight Facility in Virginia

TECH SPACE
Kepler Data Suggest Earth-size Planets May Be Next Door

Earth-like planets may be closer than thought: study

Are Super-Earths Actually Mini-Neptunes?

Herschel Finds Past-Prime Star May Be Making Planets

TECH SPACE
Light-emitting triangles may have applications in optical technology

Largest prime number to date found

South Korean Satellite Makes First Contact with Ground

Novel materials shake ship scum




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement