Hydrogen research enables graphane breakthrough

Nanoribbons were first prepared two years ago, making it possible to achieve strong variations of graphene's properties. One method to produce them is to start from carbon nanotubes and to use oxygen treatment to unzip into nanoribbons. However, this method leaves oxygen atoms on the edges of nanoribbons, which is not always desirable. A team from Umeå University in Sweden says it is now possible to unzip single walled carbon nanotubes by using a reaction with molecular hydrogen. According to physicist, Alexandr Talyzin, who has been undertaking the research, nanoribbons produced by the new method will have hydrogen on the edges which, he says, can be advantageous for some applications. "Treating the carbon nanotubes with hydrogen was a logical extension of our research," he said. "Our previous experience has been of great help in this work." Nanotubes are typically closed by semi spherical cups - halves of fullerene molecules. The researchers have previously proved that fullerene molecules can be completely destroyed by very strong hydrogenation. Therefore, they expected similar results for nanotube end cups and tried to open the nanotubes by using hydrogenation. The effect was not only confirmed, but other effects were also revealed. The most interesting discovery was that some carbon nanotubes were unzipped into graphene nanoribbons as a result of prolonged hydrogen treatment. According to Talyzin, unzipping of a nanotube with hydrogen attached to the side walls could possibly lead to synthesis of hydrogenated graphene: graphane. Until now, most attempts to synthesise graphane have been based on the reaction of hydrogen with graphene. However, this is extremely difficult, particularly if the graphene is supported on some substrate and only one side is available for the reaction. Hydrogen reacts much easier with the curved surface of carbon nanotubes. "Our new idea is to use hydrogenated nanotubes and unzip them into graphane nanoribbons. So far, only the first step towards graphane nanoribbon synthesis is done and a lot more work is required to make our approach effective," added Talyzin. "Combined experience and expertise from several groups at different universities, was a key to success." Caption: Reaction of single-walled carbon nanotubes (SWNTs) with hydrogen gas