Preparation of multi‐walled carbon nanotubes/SiO ₂ core–shell nanocomposites by a two‐step Stöber process

The surface modification and functionalisation of multi‐walled carbon nanotubes (MWNTs) could provide enhanced properties to MWNTs for highly specific applications which often require solubilisation and dispersion, promotion of functionality, biocompatibility or lower toxicity of MWNTs. Herein, a novel nanocomposite consisting of MWNTs as a core and amorphous silica (SiO ₂ ) as a shell is developed. First, the functionalisation of MWNTs with carboxylic functional group (MWNTs‐COOH) was obtained via oxidation using the concentrated sulphuric acid/nitric acid mixture (3:1 v/v) treatment. Second, a silica uniform layer was grown on MWNTs‐COOH by a two‐step Stöber process. The core–shell nanostructure is characterised by Fourier‐transform infrared spectroscopy, X‐ray powder diffraction, transmission electron microscopy, and energy dispersive spectrometer. Experimental results show that a SiO ₂ shell was uniformly coated on the surface of MWNTs with a thickness of 5–10 nm. The results can have important implications for the preparation of carbon nanotube core–shell nanocomposites in general.