Argonne researcher studies what makes quantum dots blink
Argonne, Ill. (Oct. 1, 2007) – In order to learn more about the origins of
quantum dot blinking, researchers from the U.S. Department of Energy's Argonne
National Laboratory, the University
of Chicago and the California
Institute of Technology have developed a method to characterize it on faster time scales
than have previously been accessed.
Nanocrystals of semiconductor material, also known as quantum
dots, are being intensively investigated for applications such as light-emitting
diodes, solid-state lighting, lasers, and solar cells. They are also already
being applied as fluorescent labels for biological imaging, providing several
advantages over the molecular dyes typically used, including a wider range
of emitted colors and much greater stability.
Quantum dots have great
promise as light-emitting materials, because the wavelength, or color, of light
that the quantum dots give off can be very widely tuned simply by changing
the size of the nanoparticles. If a single dot is observed under a microscope,
it can be seen to randomly switch between bright and dark states. This flickering,
or blinking, behavior has been widely studied, and it has been found that a
single dot can blink off for times that can vary between microseconds and several
minutes. The causes of the blinking, though, remain the subject of intense
study.
The methods developed by Matt Pelton of Argonne's Center
for Nanoscale Materials and his team of collaborators has revealed a previously unobserved change in
the blinking behavior on time scales less than a few microseconds. This observation
is consistent with the predictions of a model for quantum-dot blinking previously
developed by Nobel Laureate Rudolph Marcus, contributor to this research, and
his co-workers. In this model, the blinking is controlled by the random fluctuation
of energy levels in the quantum dot relative to the energies of trap states
on the surface of the nanocrystal or in the nearby environment.
The results of this research provide new insight into the mechanism of quantum-dot
blinking, and should help in the development of methods to control and suppress
blinking. Detailed results of this work have been published in a paper in the
Proceedings
of the National Academy of Sciences.
Argonne's Center for Nanoscale Materials work for this research was funded
by the U.S. Department of Energy's Office of Basic
Energy Science.
Argonne National Laboratory seeks solutions to pressing national problems in science and technology.
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the U.S.
Department of Energy's Office
of Science.
For more information, please
contact Steve McGregor (630/252-5580 or media@anl.gov)
at Argonne.
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