Metal oxide nanotubes: lower-cost alternative to carbon?

Tunable process
"The crux here is that when you try to make carbon nanotubes with diameters of less than about 10 nanometers, they become very difficult to control," said Nair. "But these metal oxide materials are very easy to control because of the mild chemistry we use—reactions sometimes take days to complete—which means we can take samples and analyze them with different types of characterization to fine-tune our process, which is very hard to do with carbon nanotubes."

So far the two nanotube materials fabricated in Nair's lab are varieties of aluminosilicogermanate (AlSiGeO) with diameters of from 1.5 to 4.8 nanometers and lengths of less than 100 nanometers. Electronic characterization of the current experimental material reveals bandgaps between 3.5 4.5 electron volts, making them similar to gallium nitride and zinc sulfide. Nair plans to lower the bandgap in the next generation of materials by inserting transition atoms into the organic nanotube to bring them nearer to traditional semiconductors.

The researchers also plan to do detailed characterization of the metal oxide nanotubes, examining their electronic properties as well as chemical properties such as adsorption and diffusion. The team further wants to create a general theory regarding the formation of the materials, along with detailed models, so that new versions can be designed with specific desirable properties.

Nair's research was funded by Georgia Tech and the American Chemical Society Petroleum Research Fund. The team included Georgia Tech doctoral candidates Suchitra Konduri and Sanjoy Mukherjee.