Functionalisation of aligned carbon nanotubes with nitric acid vapour

Millimetre high aligned carbon nanotubes (ACNTs) were functionalised by nitric acid vapour at low temperature with the formation of carbonyl and carboxyl functional groups. Samples were analysed using a scanning electron microscope (SEM), EDX, Fourier transformed infrared (FTIR), Raman and X-ray photoelectron spectroscopy (XPS). Depending on the temperature and reaction time, the treatment can lead to uniform sidewall functionalisation preserving the alignment of the ACNT ´forest´, to random destruction, leading to significant modification of the morphology of the ACNT ´forest´, or in some cases to cutting off the ACNTs from the substrate. Influence of the treatment duration and temperature on samples morphology and oxygen-to-carbon ratio are discussed.