Oxidized multi‐walled carbon nanotubes (MWCNTs) were prepared by functionalizing MWCNTs with nitric acid (70%). In order to remove the oxidative debris, in which partially attached onto the outer layer of MWCNTs side wall, the functionalized MWCNTs (f‐MWCNTs) by reflux method were carried out with NaOH (1M) and followed by HCl (1M) wash. The presence of the carboxyl (–COOH) group that covalently attached onto the f‐MWCNTs side wall is confirmed with acid‐base titration (Boehm titration). The transmission electron microscopy images show the comparison of pristine MWCNTs, f‐MWCNTs and base‐acid wash of f‐MWCNTs, whereas energy dispersive Xray analysis confirms the removal of sulphur, a common catalyst material typically employed in the production of carbon nanotubes (CNTs). The UV‐Visible spectroscopy shows the dispersibility of pure and functionalized MWCNTs in water (H2O).
