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Nanohelices for nanoscale sensors?

New nanohelices created from zinc oxide and which bear a resemblance to the helical configuration of DNA discovered 50 years ago, could become a basis for creating nanoscale sensors, transducers, resonators and other devices that rely on electromechanical coupling.

New nanohelices created from zinc oxide and which bear a resemblance to the helical configuration of DNA discovered 50 years ago, could become a basis for creating nanoscale sensors, transducers, resonators and other devices that rely on electromechanical coupling.If you're familiar with nanotechnology, you know that nanostructures can show up in a great variety of shapes, such as nanotubes, nanorings or nanobelts. But have you heard about nanohelices? These new nanostructures, which bear a resemblance to the helical configuration of DNA discovered 50 years ago, are built from zinc oxide. These nanohelices can "reach lengths of up to 100 microns, with diameters from 300 to 700 nanometers and widths from 100 to 500 nanometers." And they could become a basis for creating nanoscale sensors, transducers, resonators and other devices that rely on electromechanical coupling.

These nanohelices have been created by Zhong Lin Wang and his fellow researchers in his group at the Georgia Institute of Technology.

And here starts another story. On September 9, 2005, the Georgia Institute of Technology issued a news release about these nanohelices, soberly named "Nanohelix structure provides new building block."

But twenty days later, the Chinese Academy of Sciences (CAS), where Zhong Lin Wang is also working for the National Center for Nanoscience and Technology published its own press release with a more exciting title,"First helical structure in the nano-world".

Intrigued by this discrepancy, I looked around and found that nanohelices are not that new, and have been a research subject for several years now.

You'll find more on this below, but let's first look at some images of these nanohelices taken via a scanning electron microscope (SEM) (Credit: Georgia Institute of Technology).

Nano helices -- part 1

These right-handed ZnO helical nanostructures are pretty small, with nanobelts having a typical width of about 30 nanometers.

Nano helices -- part 2

Here is a short excerpt of the Georgia Tech news release about the fabrication process of these nanohelices.

Zinc oxide (ZnO) powder is positioned inside an alumina tube in a horizontal high-temperature tube furnace. Under vacuum, the material is heated to approximately 1,000 degrees Celsius, at which point an argon carrier gas is introduced. Heating continues until the furnace reaches approximately 1,400 degrees. The nanohelix structures form on a polycrystalline aluminum oxide (Al2O3) substrate in the furnace.

And other exotic nanostructures may be produced by this research team.

Thus far, Wang’s research team has produced nearly 20 different zinc oxide nanostructures, including nanobelts, aligned nanowires, nanotubes, nanopropellor arrays, nanobows, nanosprings, nanorings, nanobowls and others. And there may yet be other structures discovered.
"You never know what other structures might be out there that could be added to this toolbox," said Wang. "From the richness of this configuration and the complete properties, this is a unique material that could become the new material for nanotechnology following carbon nanotubes."

The latest research work about these nanohelices has been published by Science under the title "Conversion of Zinc Oxide Nanobelts into Superlattice-Structured Nanohelices" (Vol. 309, Issue 5741, Pages 1700-1704, September 9, 2005). Here are two links to the abstract and to the full paper (PDF format, 5 pages, 517 KB).

But a previous work was published by Nano Letters two years ago under the name "Spontaneous polarization-induced nanohelixes, nanosprings, and nanorings of piezoelectric nanobelts" (Vol. 3, No. 12, pages 1625-1631, August 6, 2003). And here are the links to the abstract and the full paper (PDF format, 7 pages, 1.06 MB). The pictures above were extracted from this paper.

After reading all these elements, what do you think of the CAS press release claiming a world's premiere for nanohelices?

Sources: Georgia Institute of Technology, September 9, 2005; The Chinese Academy of Sciences, September 29, 2005; and various web sites

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