Surface modification of multiwall carbon nanotubes by sulfonitric treatment

Abstract

Carbon nanotubes are widely used for electronic, mechanical, and optical devices due to their unique structural and quantum characteristics. The species generated by oxidation on the surface of these materials permit binding new reaction chains, which improves the dispersibility, processing and compatibility with other materials. Even though different acid treatments and applications of these CNT have been reported, relatively few research studies have focused on the relationship between the acid treatment and the formation of nanodefects, specific oxidized species or CNT surface defects. In this work, multiwall carbon nanotube (MWCNT) oxidation at 90 • C was characterized in order to determine the acid treatment effect on the surface. It was found that oxidized species are already present in MWCNT without an acid treatment, but there are not enough to cause water-based dispersion. The species were identified and quantified by infrared spectroscopy and X-ray photoelectron spectroscopy. Also, transmission electron microscopy observations showed not only modifications of the oxidized species, but also morphological damage on the surfaces of MWCNT after being subjected to the acid treatment. This effect was also confirmed by Raman spectroscopy. The acid treatment generates higher oxidized species, decreasing the zeta potential in the whole pH range.

Electrochemical Behaviour of Microwave‐assisted Oxidized MWCNTs Based Disposable Electrodes: Proposal of a NADH Electrochemical Sensor

“…In Figure b–e, the appearance of a band at 3500 cm −1 is evident; this corresponds to the stretching of the isolated surface hydroxyl groups from alcoholic or carboxyl functionalities produced during the oxidation of MWCNTs. The shifts from characteristic wavenumbers to lower wavenumbers indicate the presence of strong hydrogen bonds between ‐OH groups . The bands in the 1750–1630 cm −1 range can be assigned to C=O absorption in different functional groups (carboxylic, ketone/quinone).…”

“…Spectra b to e also exhibit an increase of the bands in the 1750–1630 cm −1 range that can be related to the formation of an increasing number of carboxylic groups at the MWCNTs surface. The relative increase for the bands in the 1250–950 cm −1 wave region for CNT30 (Figure e) indicates an increase in the amounts of hydrated surface oxides related to a mineralization of the material because of the extended oxidation treatment . On the other hand, the band at 1380 cm −1 (C−O from OH group) exhibits an increase in absorbance intensity, as a function of the treatment time, reaching the highest value for CNT15, and then, decreases for CNT30.…”

Capillary electrophoresis analysis of affinity to assess carboxylation of multi-walled carbon nanotubes

“…Acid treatment has been used to carboxylate surface defects and end caps on the carbon nanotubes and the methods, times, and acids used for treatments vary in the literature [9, 12, 27–29]. Affinity capillary electrophoresis was used to quantify the effects of acid treatment on pristine carbon nanotubes.…”

Heterocoagulation and SPS sintering of sulfonitric-treated CNT and 8YZ nanopowders

“…In two recent articles [24,25], we reported a systematic study of the surface modification of multiwall CNTs by sulfonitric acid exploring both the temperature and time as processing variables. Sulfonitric treatment was selected for the present study due to its known strong oxidizing capabilities, the treatment time was fixed at 20 min, based on bibliographic data, and the variable parameter was the treatment temperature.…”