Comparative Study on Contents of Oxygen-containing Groups on Multi-walled Carbon Nanotubes Functionalized by Three Kinds of Acid Oxidative Methods
The functionalization degree was evaluated by the determination of the oxygen-containing groups on carbon nanotubes.In this study,we prepared the acid oxidative multi-walled carbon nanotubes(c-MWNTs) by three methods and then compared their dispersion stability.The qualitative characterization of c-MWNTs was carried out by scanning electron microscope(SEM) and FTIR spectrometer.NaHCO3,Na2CO3 and NaOH were used to selectively react with the different acid sites on c-MWNTs surface.The concentration of oxygen-containing groups on c-MWNTs was determined by acid-base titration and the endpoint was judged by means of potentiometric titration.The result showed that the amount of carboxyl and hydroxyl were very different in three kinds of c-MWNTs.The order of the content is carboxylhydroxyllactones.The effect of functionalization by concentrated HNO3/concentrated H2SO4 under ultrasonication was the best.