Researchers working to make structures
at the size-scale of molecules are tapping self-assembly techniques found
National Renewable Energy Laboratory researchers have found a
way to construct fairly complicated nanostructures by combining a genetically
engineered form of the protein cohesin with quantum dots. Cohesin is found
naturally in a microorganism that uses it to build side protein complexes
dubbed cellusomes; quantum dots are bits of semiconductor material that
can trap electrons.
The researchers' nanostructures have a combination of light-absorption
and electrical properties that could form the basis of a new generation
of solar cells.
The researchers formed the three-armed, or trefoil, structures
by causing the amino acid tags from the cohesin to interact with the zinc
sulfide shell of a cadmium selenide quantum dot, then subjecting the combination
to high-pressure chromatography, a technique for chemically separating
The protein-coated quantum dot structures have an average diameter
of 30 to 75 nanometers, which is 1,000 to 2,000 times narrower than a
The researchers are working to create more complicated quantum
dot arrays. The ultimate goal is to self-assembled quantum dots arranged
in specific patterns and to control energy and charge transfer between
them in order to harvest energy from light, according to the researchers.
The work appeared in the November 12, 2003 issue of Nano Letters.
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