Nanotechnology Now

Our NanoNews Digest Sponsors





Heifer International

Wikipedia Affiliate Button


android tablet pc

Home > Press > Los Alamos Researchers Unravel the Mystery of Quantum Dot Blinking

"Artists conception of how solving the problem of quantum blinking
may lead to applications in areas such as solid state lighting." Courtesy Los Alamos National Laboratory
"Artists conception of how solving the problem of quantum blinking may lead to applications in areas such as solid state lighting." Courtesy Los Alamos National Laboratory

Abstract:
Research by Los Alamos scientists published today in the journal Nature documents significant progress in understanding the phenomenon of quantum-dot blinking. Their findings should enhance the ability of biologists to track single particles, enable technologists to create novel light-emitting diodes and single-photon sources, and boost efforts of energy researchers to develop new types of highly efficient solar cells.

Los Alamos Researchers Unravel the Mystery of Quantum Dot Blinking

Los Alamos, NM | Posted on November 9th, 2011

Most exciting is that the Los Alamos researchers have shown that blinking can becontrolled and even completely suppressed electrochemically. As the Nature article describes, the group developed a novel spectro-electrochemical experiment that allowed them to controllably charge and discharge a single quantum dot while monitoring its blinking behavior. These experiments facilitated the discovery of two distinct blinking mechanisms. "Our work is an important step in the development of nanostructures with stable, blinking-free properties for applications from light-emitting diodes and single-photon sources to solar cells," said Victor Klimov, LANL scientist and director of the Center for Advanced Solar Photophysics (CASP).

Quantum dots are particles between 1 and 10 nanometers in diameter. A nanometer is only one billionth of a meter across, or about 1/3000th the diameter of a human hair. At these tiny dimensions, the rules of quantum physics allow scientists to produce particles with finely tunable, size-dependent electronic and optical properties. Together with the fact that they can be fabricated by means of facile wet-chemistry techniques, their quantum nature makes these dots attractive materials for a wide range of applications.

Nanocrystal quantum dots have been on the research scene for decades. The color they produce when excited by light absorption or electrical current can be precisely tuned from the infrared through the visible to the ultraviolet spectra, andthey are cheap and easy to make.

Setagainst these advantages is a drawback—quantum-dot optical properties can randomly vary over time. Perhaps, the most dramatic manifestation of this variation is quantum-dot "blinking."

Additionally,if energized by electrical current or light, they are characterized by an effect known as Auger recombination that both competes with light emission in light-emitting diodes and reduces current output in solar cells. Both blinking and Auger recombination reduce the efficiency of quantum dots, and controlling them has been the focus of intense research.

To probe the mechanism responsible for blinking, Christophe Galland, postdoctoral researcher in CASP, along with collaborators from the Center for Integrated Nanotechnologies (CINT) and CASP developed a novel spectro-electrochemical experiment that allowed them to controllably charge and discharge a single quantum dot while monitoring its blinking behavior. It is this work that is described in the Nature article. Its main result is the discovery of two distinct blinking mechanisms.

The first is consistent with the traditional concept of quantum-dot blinking, that is, the random electrical charging and discharging of the core of the dot. In this model, a charged state is "dark" due to highly efficient nonradiative Auger recombination.

The second mechanism was a surprise; the majority of quantum dots blink due to the filling and emptying of a surface defect "trap" on the dot. If not occupied, this trap intercepts a "hot" electron that would otherwise produce photon emission, thus causing a blink. With further research into the photophysical properties of quantum dots, the scientists hope to provide a comprehensive theoretical model of this phenomenon.

"The new single nanocrystal spectro-electrochemistry technique developed here could readily be extended to study the effect of charging in a wide array of nanostructures, including carbon nanotubes and nanowires," said Han Htoon, a CINT staff scientist who took part in the research. "I believe that it will become an important new capability for CINT."

Experiments were conducted at CINT, a U.S. Department of Energy Office of Science User Facility and Nanoscale Science Research Center. Its emphasis is on exploring the path from scientific discovery to the integration of nanostructures into the micro and macro worlds.

CASP is an Energy Frontier Research Center funded by the U.S. Department of Energy Office of Science, Office of Basic Energy Sciences. Its goal is to explore the unique physics of nanoscale materials to boost the efficiency of solar energy conversion through novel light-matter interaction regimes, controlled excited-state dynamics, and engineered carrier-carrier coupling.

This work was also sponsored by the National Institutes of Health, NIH-NIGMS grant 1R01GM084702-01 (Htoon, Sykora, Hollingsworth, P.I.) that has the core aim of developing novel non-blinking quantum dots as molecular probes. This work was also sponsored by the Los Alamos National Laboratory Directed Research and Development (LDRD) program.

Reference: "Two types of luminescence blinking revealed by spectroelectrochemistry of single quantum dots." Nature, November 10, 2011. doi:10.1038/nature10569. Christophe Galland, Yagnaseni Ghosh, Andrea Steinbruck, Milan Sykora, Jennifer A. Hollingsworth, Victor I. Klimov & Han Htoon. Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.

####

About Los Alamos National Laboratory
Los Alamos National Laboratory, a multidisciplinary research institution engaged in strategic science on behalf of national security, is operated by Los AlamosNational Security, LLC, a team composed of Bechtel National, the University of California, The Babcock & Wilcox Company, and URS for the Department of Energy’s National Nuclear Security Administration.

Los Alamos enhances national security by ensuring the safety and reliability of the U.S. nuclear stockpile, developing technologies to reduce threats from weapons of mass destruction, and solving problems related to energy, environment, infrastructure, health, and global security concerns.

For more information, please click here

Contacts:
Nancy Ambrosiano
505.667.0471

Copyright © Los Alamos National Laboratory

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

Imaging electric charge propagating along microbial nanowires October 20th, 2014

Design of micro and nanoparticles to improve treatments for Alzheimers and Parkinsons: At the Faculty of Pharmacy of the UPV/EHU-University of the Basque Country encapsulation techniques are being developed to deliver correctly and effectively certain drugs October 20th, 2014

Physicists build reversible laser tractor beam October 20th, 2014

Removal of Limitations of Composites at Superheat Temperatures October 20th, 2014

Laboratories

HP Supercomputer at NREL Garners Top Honor October 19th, 2014

ORNL research reveals unique capabilities of 3-D printing October 15th, 2014

Scientists Map Key Moment in Assembly of DNA-Splitting Molecular Machine: Crucial steps and surprising structures revealed in the genesis of the enzyme that divides the DNA double helix during cell replication October 15th, 2014

Display technology/LEDs/SS Lighting/OLEDs

QD Vision Wins Prestigious Presidential Green Chemistry Challenge Award from the U.S. Environmental Protection Agency October 16th, 2014

Beyond LEDs: Brighter, new energy-saving flat panel lights based on carbon nanotubes - Planar light source using a phosphor screen with highly crystalline single-walled carbon nanotubes (SWCNTs) as field emitters demonstrates its potential for energy-efficient lighting device October 14th, 2014

Govt.-Legislation/Regulation/Funding/Policy

Crystallizing the DNA nanotechnology dream: Scientists have designed the first large DNA crystals with precisely prescribed depths and complex 3D features, which could create revolutionary nanodevices October 20th, 2014

Imaging electric charge propagating along microbial nanowires October 20th, 2014

HP Supercomputer at NREL Garners Top Honor October 19th, 2014

First Canada Excellence Research Chair gets $10 million from the federal government for oilsands research at the University of Calgary: Federal government announces prestigious research chair to study improving oil production efficiency October 19th, 2014

Discoveries

Imaging electric charge propagating along microbial nanowires October 20th, 2014

Design of micro and nanoparticles to improve treatments for Alzheimers and Parkinsons: At the Faculty of Pharmacy of the UPV/EHU-University of the Basque Country encapsulation techniques are being developed to deliver correctly and effectively certain drugs October 20th, 2014

Physicists build reversible laser tractor beam October 20th, 2014

Removal of Limitations of Composites at Superheat Temperatures October 20th, 2014

Announcements

Imaging electric charge propagating along microbial nanowires October 20th, 2014

Design of micro and nanoparticles to improve treatments for Alzheimers and Parkinsons: At the Faculty of Pharmacy of the UPV/EHU-University of the Basque Country encapsulation techniques are being developed to deliver correctly and effectively certain drugs October 20th, 2014

Physicists build reversible laser tractor beam October 20th, 2014

Removal of Limitations of Composites at Superheat Temperatures October 20th, 2014

Energy

First Canada Excellence Research Chair gets $10 million from the federal government for oilsands research at the University of Calgary: Federal government announces prestigious research chair to study improving oil production efficiency October 19th, 2014

Magnetic mirrors enable new technologies by reflecting light in uncanny ways October 16th, 2014

Unique catalysts for hydrogen fuel cells synthesized in ordinary kitchen microwave oven October 14th, 2014

Dyesol Signs Letter of Intent with Tata Steel October 13th, 2014

Quantum Dots/Rods

QD Vision Wins Prestigious Presidential Green Chemistry Challenge Award from the U.S. Environmental Protection Agency October 16th, 2014

Ultrafast remote switching of light emission October 2nd, 2014

Platinum meets its match in quantum dots from coal: Rice University's cheap hybrid outperforms rare metal as fuel-cell catalyst October 1st, 2014

University of Electro-Communications research: High density quantum dots for powerful solar cells September 25th, 2014

Solar/Photovoltaic

Magnetic mirrors enable new technologies by reflecting light in uncanny ways October 16th, 2014

Dyesol Signs Letter of Intent with Tata Steel October 13th, 2014

DNA nano-foundries cast custom-shaped metal nanoparticles: DNA's programmable assembly is leveraged to form precise 3D nanomaterials for disease detection, environmental testing, electronics and beyond October 10th, 2014

Over 100 European experts meet in Barcelona thanks to a COST Action coordinated from ICN2: The ISOS-7 Summit discusses the future of organic photovoltaic devices October 7th, 2014

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







© Copyright 1999-2014 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE