Tunable amorphous carbon nanotubes prepared by a simple template

An easy versatile method is reported to synthesize tunable amorphous carbon nanotubes (a-CNTs) with different pore diameter, length and orientation of graphene layers at a low temperature of 450 °C in the absence of metal catalysts by using porous anodic aluminum oxide (AAO) as a template and citric acid as a precursor. Since citric acid was adsorbed by hydrogen bonds with the -OH groups at the walls of the AAO templates, which can be influenced by the concentration of H⁺ ions in the solution, the pH leads to the change of the orientation of graphene layers and the graphitization degree.