Double-walled carbon nanotubes: Quantitative purification assessment, balance between purification and degradation and solution filling as an evidence of opening

Abstract

We compared the effect of different oxidizing agents on purification, functionalization and opening of double-walled carbon nanotubes. The oxidative treatments were realized in nitric acid solutions at different concentrations (3 M or 15 M), in a mixture of two oxoacids (conc. HNO 3 /conc. H 2 SO 4) or in sulphuric acid solutions of KMnO 4 or K 2 Cr 2 O 7. Most of these treatments were very efficient for purification (removal of residual catalytic metal nanoparticles and/or of disorganized carbon) but also caused secondary reactions such as shortening of the nanotubes, creation of functionalized amorphous carbon deposits and covalent functionalization of the outer wall. Secondary treatments were undertaken in order to remove functionalized carbon deposit by washing with sodium hydroxide solutions or by heat treatment in air. A partial filling in solution was obtained with uranyl nitrate, in order to evidence the opening of carbon nanotubes. Effects of purification and filling treatments were characterized both qualitatively by TEM and HRTEM, AFM and Raman spectroscopy, and quantitatively by elemental chemical analysis and chemical titrations.

Fast and easy preparation of few-layered-graphene/magnesia powders for strong, hard and electrically conducting composites

“…Typical images show graphene in a form that could be described as carbon veils or a crumpled FLG particle, with marked curvatures (arrowed in Fig. 4) which could reveal that it was wrapped, at least partly, around the MgO grains, in agreement with observations of other acid-treated samples [53,58]. Obviously this is very different from the classical CVD deposition on planar substrates where the graphene domain size can be easily measured.…”

Preferred attachment of fluorine near oxygen-containing groups on the surface of double-walled carbon nanotubes

“…This sample was denoted pDWCNTs. The pDWCNTs were oxidized using a two stage process widely studied by Bortolamiol et al [40]. Firstly, a sample was refluxed in 3 M HNO 3 at 130°C for 24 h and then treated by a mixture of 15 M HNO 3 and 18 M H 2 SO 4 (volume ratio is 1:3) at 70°C for 5 h. The oxidized sample, denoted ox DWCNTs, was washed by deionized water three times to neutral pH and dried at 100°C for 24 h. Fluorination of ox DWCNTs and pDWCNTs was performed in a Teflon flask with gaseous BrF 3 diluted by vapors of Br 2 at room temperature for 3 days according to the method described in [41].…”

Chlorinated holey double-walled carbon nanotubes for relative humidity sensors

“…The sample was refluxed at 130 C in 3 M HNO 3 for 24 h followed by a treatment at 70 C in 1:3 vol. solution of 15 M HNO 3 and 18 M H 2 SO 4 for 5 h. It has been shown that this procedure allows removal of disordered carbon and additionally functionalizes the DWCNTs walls by oxygen containing groups [34].…”