Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Nanometer-Scale Light Source is First to Show Single-Molecule Electroluminescence

12.08.2002


Using photon emissions from individual molecules of silver, researchers at the Georgia Institute of Technology have created what may be the world’s smallest electroluminescent light source.



Believed to be the first demonstration of electroluminescence from individual molecules, the work could lead to new types of nanometer-scale optical interconnects, high-resolution optical microscopy, nanometer-scale lithography and other applications that require very small light sources. And because single molecules are known to emit one photon at a time, the technique could ultimately be the basis for high-efficiency quantum information processing and cryptography.

Though the effect was first reported in silver clusters composed of 2-8 atoms, the researchers also demonstrated electroluminescence in similarly prepared copper clusters, suggesting the effect may broadly apply to other metals. Details of the research were reported in the August 6 issue of the Proceedings of the National Academy of Sciences.


"This is the first time that anyone has seen electroluminescence from individual molecules," said Robert Dickson, assistant professor in Georgia Tech’s School of Chemistry and Biochemistry. "What we have observed involves sub-nanometer scale sources to which an electric field is applied. These molecules emit very strongly, and are very robust."

Dickson and collaborators Tae-Hee Lee and Jose Gonzalez began with thin films of silver oxide that are not electroluminescent. By exposing the film to electrical current of approximately one amp, they "activated" some of the silver oxide molecules, which then appeared within "discolored" regions in the film. When electrodes were attached to the film and an alternating current applied, a thin line of silver clusters began to emit light in colors that varied depending on the size of the clusters. The system operated at room temperature.

"When you zoom in more closely, you can see the emissions coming from single molecules," said Dickson. "They blink and have dipole emission patterns. You see an incredibly thin line of emissive species close to the middle of the sample."


Electroluminescence occurs when an electron recombines with a positively charged molecule from which a single electron has been removed to create an electron-hole pair. First, an electron is removed from a molecule, creating a positive charge. Then, an electron is quickly injected into a different state of the same molecule. Because of the charge differences, the electron is attracted to the hole, and when they recombine, a photon is released.

While normally stimulated by applying direct current (DC), the Georgia Tech group observed a dramatically enhanced response from high frequency alternating current (AC).

While DC voltage produced electroluminescence in the activated silver clusters, Dickson and his colleagues found that high frequency AC voltage -- above 150 megahertz -- produced a response as much as 10,000 times greater. Dickson believes the AC voltage created rapid recombination within single molecules in a very narrow section of a sample, producing the enhanced response. Bulk materials normally cannot respond quickly enough to the alternating current to enhance the electroluminescence to such a large degree.

The AC current was more efficient than DC current at converting electrical current to light because it injects the electron charge at just the right time, minimizing the amount of energy lost to production of heat, Dickson explained. From a practical standpoint, that increases the operating life of the emitting clusters and reduces the amount of current required to produce light, he noted.

"We know that the charge is recombining in the molecules because you can simultaneously measure the electroluminescence and the current, and the peaks are correlated," he said. "This is an extremely interesting materials system, not only because of the single-molecule electroluminescence, but also because of the resonance we see at relatively high frequencies."

Though the discovery may have important implications for optoelectronic devices, Dickson’s group is focusing first on understanding the basic process.

"We are concentrating on understanding the very fundamental aspects of this: what the nature of the emission is, how the emission occurs, the different time scales for electron injection, hole injection and recombination," he said. "We need to know how to better control this before we can begin to use it in nanometer scale devices or as nanometer scale optoelectronic components in circuitry. A lot of engineering will have to be done to make any potential optoelectronic devices both useful and stable."

The electroluminescence research builds on earlier work done by Dickson and colleagues Lynn Peyser and Amy Vinson that demonstrated optical storage potential of thin-film silver oxide clusters. In that work, reported in the journal Science in January 2001, the researchers demonstrated binary optical storage by writing and reading simple images recorded on films of silver oxide nanoparticles activated by light of a specific frequency. That work is continuing, and advances have been made toward potential optical storage systems.

Support for Dickson’s research comes from the Sloan and Dreyfus Foundations, as well as internal Georgia Tech research funds.


RESEARCH NEWS & PUBLICATIONS OFFICE
Georgia Institute of Technology
430 Tenth Street, N.W., Suite N-116
Atlanta, Georgia 30318 USA

John Toon | EurekAlert!
Further information:
http://gtresearchnews.gatech.edu/rnpo.html

More articles from Power and Electrical Engineering:

nachricht TU Graz researchers show that enzyme function inhibits battery ageing
21.03.2017 | Technische Universität Graz

nachricht New nanofiber marks important step in next generation battery development
13.03.2017 | Georgia Institute of Technology

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

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

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Pulverizing electronic waste is green, clean -- and cold

22.03.2017 | Materials Sciences

Astronomers hazard a ride in a 'drifting carousel' to understand pulsating stars

22.03.2017 | Physics and Astronomy

New gel-like coating beefs up the performance of lithium-sulfur batteries

22.03.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>