The influence of treatment duration on multi-walled carbon nanotubes functionalized by H2SO4/HNO3 oxidation

Characterizing Functionalized Carbon Nanotubes for Improved Fabrication in Aqueous Solution Environments

“…Evolution of the high binding energy peak intensities during sonication shows a consecutive, single-step first order O-attachment mechanism, leading to the carboxylate. This scheme is consistent with a report made by (Chiang et al, 2011) showing CO to be an intermediate species, which could be oxidized quickly to other forms, usually COO under acidic environment. Sonication creates defect sites on the sidewalls that allow for O atom attachment .…”

A study on the dependence of structure of multi-walled carbon nanotubes on acid treatment

“…The results show that the position of T onset , T midpoint appears at higher temperature when the P-MWNT was acid treated for 1 and 2 h. Perhaps the main reason of this variation can be attributed to the fact that during early oxidation of F-MWNT, the oxidant starts to attack the active sites already existed on the MWNTs such as CH 2 and CH groups, so the thermal stability of F-MWNTs improves [1]. Besides lack of formation defects on surface of CNTs due to acid treatment is another reason for promotion of thermal stability of MWCNTs after acid treatment.…”

“…OH peak is related to observed water molecules on the carbon in the CNTs. In the case of F-MWNT, there is an additional peak, appeared at 1719 cm -1 which is due to the C=O stretching frequency, indicating the presence of carboxylic group created during the oxidation of MWNTs [1]. The intensity implies more number of carboxylic groups which had been successfully attached to the surface of MWNT after acid treatment.…”

“…Acid treatment by using HNO 3 has been most often used, and it has been divided into two categories: (1) treatment with boiling diluted HNO 3 , and (2) treatment with pure HNO 3 , and a mixture of concentrated H 2 SO 4 / HNO 3 in an ultrasonic bath [19]. At both methods, the nitric acid opens the end caps of MWNTs, creates the carboxylic groups at the open ends and the side wall of MWNTs, also introduces the damage on the walls of MWNTs, and even can cut the MWNTs into short of pieces [5,20].…”

“…But low purity of the MWNTs and hydrophobic and inert nature of the surface of MWNTs reduce their applications. The oxidation of MWNTs by using wet chemical [1][2][3][4][5][6][7][8][9], photo oxidation [10][11][12][13], gas phase treatment [13], and oxygen plasma [10] method is a basic technique for purification and also improvement of the chemical reactivity of the MWNTs.…”