One-step rapid preparation of CNTs using the spark plasma–assisted pyrolysis of melamine and its photoluminescence properties

In this study, carbon nanotubes (CNTs) were successfully fabricated using a novel spark plasma–assisted pyrolysis (SPAP) method at 700–900 °C. The existence of CNTs was confirmed in all samples, the diameter of the CNTs is approximately 40–50 nm. The CNTs fabricated at 750 °C presented a helical shape, which is different from the CNTs fabricated at other temperatures which presented a bending shape. The defects of CNTs, such as bending and abnormal layer spacing, are explained through the TEM observations. The sharp diffraction peak from the XRD result and the I_D/I_G ratio (a minimum of 0.772) from the Raman result revealed that the CNTs prepared at higher temperature possess better crystallinity. The photoluminescence results show that the CNTs produced exhibited strong emission peaks, and the intensity of photoluminescence could be enhanced by increasing the preparation temperature. The highlighted technique is capable of achieving the preparation of CNTs quickly, safely, and inexpensively. This technique has provided a new possibility for other materials of preparation such as boron nitride nanotubes.