The best of two nanoworlds

As you probably know by now, carbon nanotubes show amazing mechanical strength, while metal nanowires show very interesting optical and electrical properties. Combining both has proved to be a challenge. But if it was possible, this would open the way to the use of carbon nanotubes in computer chips, displays and sensors. Now, scientists from Rensselaer Polytechnic Institute (RPI) say they have developed hybrid structures which combine the strengths of carbon nanotubes and nanowires. They add that their method is another step towards the realization of nanotube-based electronics. I'm still somewhat skeptical.

As you probably know by now, carbon nanotubes show amazing mechanical strength, while metal nanowires show very interesting optical and electrical properties. Combining both has proved to be a challenge. But if it was possible, this would open the way to the use of carbon nanotubes in computer chips, displays and sensors. Now, scientists from Rensselaer Polytechnic Institute (RPI) say they have developed hybrid structures which combine the strengths of carbon nanotubes and nanowires. They add that their method is another step towards the realization of nanotube-based electronics. Even if this research work has been published by Applied Physics Letters, I'm still somewhat skeptical.

Here are some excerpts from the RPI news release.

Carbon nanotubes display amazing mechanical strength, and they are excellent conductors of electricity, with the capacity to produce interconnects that are many times faster than current interconnects based on copper. Gold nanowires also have very interesting optical and electrical properties, and they are compatible with biological applications, said [Fung Suong Ou, the paper's corresponding author and a graduate student in materials science.]
"In order to take full advantage of these materials, we demonstrate the idea of combining them to make the next generation of hybrid nanomaterials," he said. "This approach is a good method to marry the strengths of the two materials."

Below is a picture of a junction between a gold nanowire (top) and a carbon nanotube (Credit: Fung Suong Ou, RPI).

A nanotube-nanowire junction

The metal nanowires in this technique are made using an alumina template that can be designed to have pore sizes in the nanometer range. Copper or gold wires are deposited inside the pores, and then the entire assembly is placed in a furnace, where a carbon-rich compound is present. When the furnace is heated to high temperatures, the carbon atoms arrange themselves along the channel wall of the template and the carbon nanotubes grow directly on top of the copper wires.
"It's a really easy technique, and it could be applied to a lot of other materials," Ou said. "The most exciting aspect is that it allows you to manipulate and control the junctions between nanotubes and nanowires over several hundred microns of length. The alumina templates are already mass-produced for use in the filter industry, and the technique can be easily scaled up for industrial use."

If these hybrid nanostructures are so easy to develop, why did we have to wait for the research work of several students working for Prof. Pulickel M. Ajayan's Carbon Nanomaterials Research Group? I don't know for you, but I have some doubts about this new technique...

For more information, this research work has been published by Applied Physics Letters under the name "Multisegmented one-dimensional hybrid structures of carbon nanotubes and metal nanowires" (Volume 89, Article 243122, December 11, 2006). Here is a link to the abstract.

Sources: Rensselaer Polytechnic Institute news release, January 8, 2007; and various other websites

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