Purification and Oxidation Studies of Multiwall Carbon Nanotubes using Raman Spectroscopy

Abstract

A process of chemical purification of multiwall carbon nanotubes (MWNTs) is investigated to determine the structural and chemical changes in atomic bond caused by chemical treatment. As-grown multiwall carbon nanotubes were treated in mixture of H₂SO₄, HNO₃ under a refluxing condenser with magnetic stir for different time period 5, 7, 9 and 15 h (samples S1, S2, S3 and S4, respectively) at 70 ºC in order to remove amorphous carbon and catalysts completely. The acid-treated tubes are extensively characterized by means of Raman spectroscopy. Raman spectra were recorded for as-grown as well as post treated multiwall carbon nanotubes samples as prepared for different time duration. The results of Raman spectroscopy suggest that the appropriate mixing ratio between H₂SO₄ and HNO₃ is 3:1 with treatment time from 5-9 h is suitable for purification and create less defect during acid treatment.