Nanotubes self-assemble into circuit elements

Nanotubes measuring just 100 atoms in diameter have been created from designer molecules that were customised to self-assemble into angstrom-sized circuit elements, according to researchers at Purdue University, US.

Professor Hicham Fenniri's research group developed the nanotube parent molecules, which self-assemble in water first into tiny rings. The rings then snap together into long tubes. The outside of the seed molecules harbour hooks on which to hang other molecules, which functionalise the resulting nanotube for a specific electronic application.

Thus far, Fenniri has demonstrated two parent molecules: one that grows conventional wires, for electricity, and one for growing photonic devices that process light. Electronic components are next on his list. "There are several electronic applications [for nanotubes], but there are synthesis issues about how to control the chemical properties," said Fenniri. By controlling the nanotubes' chemical synthesis, the researchers hope to tailor them for applications in electronics.

Fenniri calls the devices rosette nanotubes. Their shape permits a hollow central interior channel that runs the length of the nanotube with tuneable inner and outer diameters. On the outside, smaller hollow channels are custom-tailored to the given application. Unlike other nanotubes, higher temperatures temper Fenniri's rosettes because they are based on hydrophobic attractions between molecules that increase in strength as temperature rises. In fact, according to Fenniri, his nanotubes attain a higher level of self-organisation as temperatures climb.

"We have designed a system that can be synthesised and modified almost at will. It is similar to biological systems. Our nanotubes are produced by a process of self-organisation and self-assembly," said Fenniri.