An eco-friendly air–water plasma surface treatment technique for improving the stability of graphene oxide nanosheets in aqueous solutions

Abstract

In this work, the dispersibility of graphene oxide (GO) nanosheets in an aqueous solution was significantly improved by applying air–water plasma using the dielectric barrier discharge (DBD) technique. The effects of different process variables such as the voltage, frequency, and the processing time of air–water plasma treatment on the oxidation degree of GO nanosheets were investigated by Fourier transform infrared (FT-IR) spectroscopy and other characterization methods. High-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FT-IR), ultraviolet-visible (UV–vis) spectroscopy, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and X-ray diffraction (XRD) were employed to characterize the modified and unmodified GO nanoparticles. Finally, the stability of functionalized and non-functionalized GO nanosheets in aqueous media was investigated by UV–vis spectroscopy. According to the results, the plasma-treated GO nanosheets contained the maximum number of bonded carbonyl/carboxyl groups among the studied samples at a frequency (f) of 6 kHz, a voltage (V) of 8 kV, and a processing time (t) of 5 min.