Carbon nanocells and nanotubes grown in hydrothermal fluids

For the first time multiwall carbon nanocells (∅<100 nm) and multiwall carbon nanotubes have been artificially grown in hydrothermal fluids from amorphous carbon, at temperatures below 800°C, in the absence of metal catalysts. Carbon nanocells were the result of bubble growth of graphitic multiwalls at 600°C. Pristine multiwall nanotubes grow at higher temperatures. At 800°C, the condensed solids consist of defect-free sp2-bonded multiwall nanocrystals. Hot hydrothermal fluids seem essential for the growth of curled patches of sp2-bonded carbon at low temperatures. Hydrothermal synthesis of finite sp2-bonded nanotubes and carbon nanocrystals is possible in moderate conditions and easy to reproduce.