Surface modification and dispersion of multi-walled carbon nanotubes

After being refluxed with concentrated nitric acid for different time at 120 degrees C, the multi-walled carbon nanotubes (MWNTs) were modified with sodium dodecyl sulfate (SDS). The MWNTs were characterized with TEM and IR. in addition, UV-vis spectrophometric measurement was used to quantitatively characterize colloidal stability of the dispersion. It's found that the carbon nanotubes refluxed for 4 h had a uniform length with many hydroxyl groups and carboxyl groups on the surface. Experimental results show that the addition of SDS could significantly improve the dispersion of MWNTs in water, and after 80 h, the concentration decreased very slowly to 90% of its originality.