Amine functionalization of carbon nanotubes with solid urea using different plasma treatments

Carbon nanotubes (CNTs) were amine-functionalized through treatments in inductively coupled post-discharge, capacitively coupled micro spark and pulsed micro arc/glow discharge plasma regions, using urea in solid state as functionalization agent. In each plasma mode, the CNT functionalization yield was evaluated according to the variation of the plasma power and treatment time. For that, the samples were characterized through Fourier-transform infrared spectroscopy, Raman spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The results show that, while preserving the integrity of the CNTs, an 80 % increase in oxygen content and up to 1.2 at.% of nitrogen was achieved using an asymmetric bipolar plasma power supply (ABiPPS). The adsorbed water can be completely removed from the CNTs through both a high-plasma-density treatment and a methanol washing procedure, conducted before sample characterization to remove any unreacted urea.