BETHANY HALFORD
Marrying biology and nanoscience, a team at Technion–Israel Institute of Technology, in Haifa, uses DNA to create a field-effect transistor out of single-wall carbon nanotubes (SWNTs) [Science, 302, 1380 (2003)].
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WIRED Scanning electron microscope image shows a rope of SWNTs contacting DNA-templated gold wires.
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In theory, the unique electronic properties and small size of SWNTs make them ideal components for molecular electronics. But actually using them has been less practical. Scientists typically have to employ time-consuming, labor-intensive, top-down techniques, which yield only small numbers of nanotube-based devices.
The Technion team, led by physics professor Erez Braun and graduate student Kinneret Keren, build SWNT-based transistors from the bottom up by exploiting biological systems’ ability to self-assemble. The team makes a DNA scaffold using a long piece of double-stranded DNA to which they bind a short, single strand of DNA wrapped with polymeric RecA protein. The RecA provides a precise binding site for the nanotube and protects the DNA during a subsequent metallization step, Braun says. To make the nanotubes bindable, the researchers coat them with streptavidin.
To tether the nanotube to the RecA site on the scaffolding, they use two antibodies that attach to one another. The end of one antibody links up to RecA, and the end of the other links up to streptavidin. The result is a DNA-protein-nanotube sandwich.
The scaffold DNA then gets metalized through silver reduction and subsequent electroless gold plating, ultimately producing a DNA-templated carbon nanotube between metallic wires.
“I believe that bottom-up techniques like this will pave the way for integration of molecular components into useful microelectronics,” says Keith A. Williams, a physicist at Delft University of Technology, the Netherlands. “Their approach envisions synthesis of moles of gold-contacted nanotubes in a bottle, rather than a few dozen nanotubes contacted on a wafer.”
