Evaluation of mild acid oxidation treatments for MWCNT functionalization

Acidic oxidation methods have been widely reported as an effective method to purify and functionalize the surface of carbon nanotubes (CNTs). Although effective, the strong acids typically employed and the high sonication power used to disperse the nanotubes in the solution frequently cause nanotube damage, limiting their great potential as mechanical and electrical reinforcements. This work examines the use of HNO3, H2SO4 and H2O2 at relatively low concentrations, short treatment times and low sonication power, in an attempt to achieve experimental conditions which efficiently functionalize the surface of multiwalled CNTs minimizing nanotube damage. A low power sonochemical treatment employing 3.0 M HNO3 for 2 h followed by 2 h of identical treatment with H2O2 proved to be the most effective for this aim.