Stable colloidal system of mild acid functionalized multiwalled carbon
nanotubes
*Nor Aziah Buang1, Zaiton Abd Majid1, Shafinaz Shahir2 and Fatirah Fadil1
1
Department of Chemistry, Faculty of Science,
Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor, Malaysia
2
Department of Biological Sciences, Faculty of Bioscience and Bioengineering,
Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor, Malaysia
* Ibnu Sina Institute, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor,
Malaysia.
* E-mail: noraziah@kimia.fs.utm.my
Multiwalled carbon nanotubes (MWCNTs) has a great potential in wide applications due
to their extraordinary mechanical, thermal and electrical properties. However, the aggregation and
bundling of MWCNTs has restricted the usage of this material and thus, acid treatment is
expected to promote the debundling of MWCNTs. The CNTs can be easily dispersed in polar
solvent through carboxyl groups generated on the MWCNTs surface by undergo acid treatment
functionalization. The functionalization process involves simple reaction under ultrasonication
and mixing techniques. By the chemical oxidation process of aqueous acid solution of HNO3 and
H2SO4 (1:3 v/v), the carboxyl groups were generated on the surface of MWCNTs. The remaining
amorphous carbon and metal residues were then successfully removed from the MWCNTs
structure. Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD),
Thermogravimetry Analysis (TGA) and Field Emission Scanning Electron Microscopy (FESEM) were used to characterize chemical properties and morphology of functionalized
MWCNTs. From the FTIR spectrum, the existence of carboxyl group indicates the success of
functionalization process. FE-SEM micrograph shows some surface modification on the
MWCNTs without structure collapse and complimented by X-ray diffraction analysis. In
addition, increasing of weight loss at temperature range of 100-500°C shows the decomposition
of oxygenated groups in the functionalized MWCNTs. Finally, a stable colloidal system of
MWCNTs dispersion in polar solvent was successfully obtained when functionalized and
remained stable for many days.