Oxidation of Single-Walled Carbon Nanotubes under Controlled Chemical Conditions

Abstract

Single-walled carbon nanotubes are oxidized in the presence of H 2 SO 4 /HNO 3 mixtures containing distinct concentrations of the nitronium ion, [NO 2 + ].The spectroscopic analyses of the final samples suggest a higher structural disorder in the oxidized systems with increasing [NO 2 + ].This is due to a considerable oxygen amount on the tube surface, reaching up to 30%, depending on the reaction time and [NO 2 + ].Interestingly, if long reaction time is considered, the oxygen amount on the tube surface is maximum for low [NO 2 + ] and reduces slightly for larger [NO 2 + ].On the other hand, the oxidation process occurs gradually at 4 h, allowing a fine control of the oxidation process.Therefore, if fine tuning of the oxidation degree is desirable, the reaction must be conducted during short time (4 h) using increasing [NO 2 + ] as those obtained from 2:1, 2.5:1 and 3:1 H 2 SO 4 /HNO 3 acid mixtures to produce increasing content of functionalization.