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Posted: Jan 12, 2012

Quantum dots hold promise for future lighting devices

(Nanowerk News) UT Dallas researchers are making strides in understanding the workings of quantum dots – nanosized particles that have immense potential in several industry applications.
Quantum dots could be used in a variety of ways ranging from illuminating the human body in high-tech medical imaging to increasing the efficiency of energy sources.
These tiny, semiconducting nanoparticles have a dark side though—they blink unpredictably. The effect is similar to switching a light on and off, substantially diminishing the effectiveness of light emission.
nanocrystal blinking
A systematic study of photoluminescence (PL) intensity and lifetime fluctuations in individual CdSe/CdS core/shell nanocrystal quantum dots (NQDs) as a function of shell thickness. (© ACS)
"Quantum dots are regarded as the next generation of efficient light sources because of their efficiency in both emitting and absorbing light."
Dr. Anton Malko"Quantum dots are regarded as the next generation of efficient light sources because of their efficiency in both emitting and absorbing light," said Dr. Anton Malko, assistant professor at UT Dallas. "Keeping them from blinking is key to facilitating their widespread use."
The findings are detailed in a recent issue of the journal Nano Letters ("Pump-Intensity- and Shell-Thickness-Dependent Evolution of Photoluminescence Blinking in Individual Core/Shell CdSe/CdS Nanocrystals").
Malko and fellow researchers from Los Alamos National Laboratory reported that by increasing the size of the exterior shell of the particles, blinking could be suppressed.
Researchers altered these quantum particles, which are mere billionths of a meter in size, by increasing them from around 4 nanometers to 15 nanometers.
"We observed that the same process that causes the dots to blink didn't have the same effect when we scaled up the size," Malko said. "We found that this process, the so-called "Auger" recombination, is strongly dependent on the thickness of the quantum dot's shell and allows complete blinking suppression for large shell particles.
"Gaining a better understanding of all of the forces at work in this phenomenon will lead, hopefully, to a way of reducing these unpredictable behaviors in quantum dots," Malko said. Making quantum dots with uninterrupted light output will certainly help in their employment in a variety of applications ranging from biomedical imaging to quantum information processing.
This study resulted from collaboration between Malko's group at UT Dallas and researchers from the Center for Integrated Nanotechnologies and the Center for Advanced Solar Photophysics at Los Alamos National Laboratory.
Source: University of Texas, Dallas
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