Humid air plasma-assisted surface treatment as a green functionalization technique to enhance the multi-walled carbon nanotubes dispersion and stability in aqueous solutions

Abstract

In this work, the dielectric barrier discharge (DBD) humid air plasma was employed for the functionalization of hydrophobic MWCNTs. Effects of different process variables such as voltage, frequency, and processing time of the air-water plasma on the functionalization process were investigated by Fourier transform infrared (FT-IR) analysis. The energy-dispersive X-ray spectroscopy (EDS), Scanning Electron Microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and X-ray diffraction (XRD) were used to characterize functionalized MWCNTs. The stability of the plasma-treated MWCNTs in aqueous solutions was investigated by Ultraviolet-visible (UV-Vis) spectroscopy. At the optimum operating condition, the air-water plasma functionalization technique leads to the highest concentrations of hydrophilic functional groups on the surface structure of the MWCNTs at the frequency of 7 KHz and voltage of 10 kV for 8 minutes. According to the presented results, the dispersion and stability of the MWCNTs in the aqueous solution significantly enhanced by using the proposed eco-friendly humid air plasma functionalization technique.