Researchers at Northeast Normal University in China have made multiwalled carbon nanotubes by heating grass in the presence of oxygen. The resulting tubes had diameters of 30-50 nm. "We think it is a novel and 'green' approach - from grass to carbon nanotubes," Enbo Wang told nanotechweb.org. "Using renewable natural products as the carbon source and the participation of oxygen, a benign oxidation reagent, offer numerous benefits ranging from environmental safety to further exploitation of existing farm and natural produce." Wang and colleagues took grass from a field, before drying, crumbling and heating it at 250 deg C for one hour. Then they heated the resulting material to 600 deg C for around 20 minutes in a sealed container, together with about 15 ml of oxygen. Following cooling, the team reinvested oxygen and repeated the heat treatment. They carried out this cycle about 50 times.
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