A Study on the Effects of Potassium Permanganate on the Functionalization of Multi-Walled Carbon Nanotubes

Abstract

In this work, multi-walled carbon nanotubes (MWCNTs) are functionalized by a wet chemical oxidation method using a mixture of potassium permanganate (KMnO4) and sulfuric acid (H2SO4) at 70 °C, for 12 h. The effects of various KMnO4 amounts on the functionalization of MWCNTs are studied and reported. The surface morphologies, structural properties, dispersion and thermal stability of the MWCNTs are characterized using a field emission scanning electron microscope (FE-SEM), Raman spectroscopy, UV-visible spectroscopy (UV–vis), thermal gravimetric analysis (TGA). The FE-SEM images display some surface roughness, cutting and open ends of functionalized MWCNTs (f-MWCNTs). The TGA curves of f-MWCNTs indicate a weight loss between 150 °C and 350 °C, which is attributed to the loss of carboxyl groups on the MWCNTs surface and the weight loss is increased when KMnO4 mass is increased. The highest weight loss value of 22.23% is recorded for the oxidation treatment with a mixture of 5 M H2SO4 and 200 mg KMnO4. UV–vis measurements indicate that the f-MWCNTs are highly dispersed in the aquoues solution in comparision to the pristine MWCNTs (p-MWCNTs). And f-MWCNTs with higher functionalization degree show better dispersibility. This study provides a great prospect of effective method to cut, end-open, functionalize and disperse MWCNTs.