Protein orders semiconductor bits

Researchers working to make structures at the size-scale of molecules are tapping self-assembly techniques found in nature.

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 substances.

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 human hair.

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.