Controlled growth of carbon nanotubes using zinc oxide nanotubes as the catalyst

In this study, carbon nanotubes (CNTs) were synthesized on a catalyst of zinc oxide (ZnO) nanorods prepared with a hydrothermal process. The surface morphology of the CNTs was studied with scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the structural properties and chemical compositions of the CNTs were studied with Raman spectroscopy and energy dispersive spectrometer (EDS), respectively. Our research results reveal that the CNTs grown on ZnO nanorods exhibit a multiwalled structure with defective graphite sheets on the wall. The surfaces of the CNTs grown on ZnO catalyst were covered by the nanonodes carbon nanoparticles. Raman spectra show that the appearance of the relatively strong D peaks in CNT films grown on ZnO catalyst can possibly result from the existence of nanonodes and the structural defects on the nanotubes graphite sheets. EDS results reveal that the CNTs grown on ZnO nanorods do not need any purification process to optimize the field-emission characteristics of the CNTs. The CNTs synthesized on ZnO catalyst exhibit a lower turn-on electric field and a higher emission current density than that of the CNTs synthesized on Ni catalyst.