Wall structure and surface chemistry of hydrothermal carbon nanofibres

A transmission electron microscopy examination of hydrothermally produced carbon nanofibres/nanotubes with outer diameter 50-200 nm suggests that the tube walls are inclined with respect to the tube axis. The apex angles are in the range 8degrees- 16degrees. The structure of these tubes and their growth mechanism can be described by a conical-scroll model. The conical-scroll structure enables functionalization of both inner and outer tube surfaces. The outer wall of these nanofibres is shown to be covered by a hair-like layer, with a characteristic length of about 0.5 nm. Electron energy loss spectroscopy suggests that these 'hairs' are functional groups containing oxygen and carbon. The presence of these groups on the tube surface can account for the reported hydrophilic character of these tubes.