June 23, 2009

Scientists grow molecular wire brushes

U.S. chemists say they've created a way to grow molecular wire brushes that conduct electrical charges -- a first step in developing biological fuel cells.

University of Georgia Assistant Professor Jason Locklin and graduate students Nicholas Marshall and Kyle Sontag grew polymer brushes made of chains of thiophene and benzene attached to metal surfaces as ultra-thin films.

The molecular wires are actually polymer chains that have been grown from a metal surface at very high density, Locklin said. The structure of the film resembles a toothbrush, where the chains of conjugated polymers are like the bristles. We call these types of coatings polymer brushes.

The scientists said they laid down a single layer of thiophene as the film's initial coating, then built up chains of thiophene or benzene using a controlled polymerization technique.

The beauty of organic semiconductors is how their properties change, based on size and the number of repeating units, said Locklin. Thiophene itself is an insulator, said Locklin, "but by linking many thiophene molecules together in a controlled fashion, the polymers have conducting properties.

This technique gives us the control to systematically vary polymer architecture, opening up the possibility for various uses in electronic devices such as sensors, transistors and diodes, he added.

The research appears in the journal Chemical Communications.