Simple process makes thin nanoribbons for conductive products

April 16th, 2009 - 4:57 pm ICT by ANI  

Washington, April 16 (ANI): Scientists at Rice University, US, have uncovered a room-temperature chemical process that splits carbon nanotubes to make flat nanoribbons, which can be used to create basic elements for aircraft, flat-screen TVs, electronics and other conductive products.

The technique makes it possible to produce the ultrathin ribbons in bulk quantities.

These ribbons are straight-edged sheets of graphene, the single-layer form of common graphite found in pencils.

One would have to place thousands of them side by side to equal the width of a human hair, but tests show graphene is 200 times stronger than steel.

“If you want to make conductive film, this is what you want,” said Professor James Tour, Rice’s Chao Professor of Chemistry and also a professor of mechanical engineering and materials science and computer science.

“As soon as we started talking about this process, we began getting calls from manufacturers that recognized the potential,” he added.

The process involves sulfuric acid and potassium permanganate, which have been in common use since the 1890s.

This chemical one-two punch attacks single and multiwalled carbon nanotubes, reacting with the carbon framework and unzipping them in a straight line.

The unzipping action can start on the end or in the middle, but the result is the same - the tubes turn into flat, straight-edged, water-soluble ribbons of graphene.

When produced in bulk, these microscopic sheets can be “painted” onto a surface or combined with a polymer to let it conduct electricity.

Nanotubes have been used for that purpose already.

“But when you stack two cylinders, the area that is touching is very small,” Tour said. “If you stack these ribbons into sheets, you have very large areas of overlap. As an additive for materials, it’s going to be very large, especially for conductive materials,” he added.

Rice postdoctoral research associate Dmitry Kosynkin made the find while studying oxidation processes involving nanotubes.

“Dmitry came to me and said he had nanoribbons. It took a while to convince me, but as soon as I saw them, I realized this was huge,” recalled Tour.

According to Tour, nearly all of the nanotubes subjected to unzipping turn into graphene ribbons, and the basic process is the same for single or multiwalled tubes.

Single-walled carbon nanotubes convert to sheets at room temperature and are good for small electronic devices because the width of the unzipped sheet is highly controllable.

But, the multiwalled nanotubes are much cheaper starting materials, and the resulting nanoribbons would be useful in a host of applications. (ANI)

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