Radical scavenging efficiencies of modified and microwave-treated multiwalled carbon nanotubes

Radical scavenging efficiencies of various modified multiwalled carbon nanotubes (CNT) including ball-milled CNT, benzoyl peroxide-treated CNT, acid-treated CNT, and microwave-treated CNT were investigated in this study. Raman spectrometry, X-ray photoelectron spectroscopy, scanning electron microscopy, and energy dispersive spectrometry were used to characterize these modified CNT. Electron paramagnetic resonance (EPR) and ultraviolet/visible spectrophotometer (UV/Vis) were used to measure radical scavenging efficiencies of the modified CNT for hydroxyl (OH) radical and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, respectively. EPR, UV/Vis, and Raman spectra revealed that the radical scavenging efficiencies for both radicals increased with increasing contents of defect sites on the modified CNT. The DPPH radical scavenging efficiencies of the modified CNT were found to be relatively low as compared to the OH radical scavenging efficiencies; the rankings in the scavenging efficiencies, however, were similar for both radicals. The findings in this study that the modified CNT were effective radical scavengers suggested that these CNT have potential applications as antioxidants.