Growth of tadpole-like carbon nanotubes from TiO2 nanoparticles

Tadpole-like carbon nanotubes (CNTs) were synthesized by chemical vapor deposition from ethanol using TiO2 nanoparticles (NPs) as catalyst. The CNTs have a cup-stacked structure are typically less than 500 nm in length, and have a non-uniform diameter with a big “head” and a smaller diameter “tail”, inside which a catalyst NP is usually encapsulated. Transmission electron microscopy (TEM) characterisation reveals that the TiO2 catalyst NPs are oxygen-deficient, which is considered to be responsible for the gradually diminishing diameter of the CNTs. In situ TEM study further confirms that the effective catalytic species is solid oxygen-deficient titanium oxide. A tip growth mode combined with vapor–solid–solid mechanism is proposed for the growth of the CNTs.