Surface functionalization of vertically-aligned carbon nanotube forests by radio-frequency Ar/O2 plasma

Vertically-aligned carbon nanotube (CNT) forests were modified using radio-frequency Ar/O₂ plasma. The effect of plasma parameters on surface morphology, atomic composition and structure of CNT forests were studied. Functionalized CNT forests preserved vertical alignment and showed dramatic change in surface morphology, and bundle-like patterns were observed from scanning electron microscopy examination. X-ray photoelectron spectroscopy and Raman analyses reveal that the amount of sp²-hybridized graphite-like carbon bond in CNTs decreased significantly and oxygen-containing functionalities like C–O and O–CO groups were introduced after treatment. And the functionalization occurred exclusively on outer surface of CNT forests. Ar/O₂ plasma was found to be more efficient than pure Ar plasma for oxygen functionalization.