Doped carbon nanotube array with a gradient of nitrogen concentration

Carbon nanotube (CNT) arrays doped with nitrogen were synthesized using chemical vapor deposition by pyrolysis of xylene/pyridine and ferrocene with a modified precursor feeding technique. The system produced a gradient of nitrogen concentration that modified the CNTs from a hollow cylinder to a bamboo-shaped structure which contains a series of compartments whose lengths are gradually reduced as the nitrogen concentration increases.