Effects of TEOS Precursor and Reaction Time on the Synthesis of Silica Coated Single-Walled Carbon Nanotubes

Abstract

This paper demonstrates a technique to synthesize silica-coated single-walled carbon nanotubes (SWNTs@SiO2) based on sodium dodecyl sulfate (SDS), 3-aminopropyltriethoxysilane (APTES), ammonium hydroxide (NH4OH) and tetraethyl orthosilicate (TEOS). The coating of silica is done to promote bond strength between SWNTs@SiO2 and other materials. The anionic surfactant used in the coating process helps create linkages between the silica coupling agent and the SWNTs’ walls without compromising the excellent properties of SWNTs. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive x-ray spectroscopy (EDX) were employed to characterize the sizes of SiO2 particles, the structure of SWNTs@SiO2, and the elements existed in the materials. The size of SiO2 particles has shown to be dependent on the amount of TEOS concentration and reaction time. Higher TEOS concentration and longer reaction time led to larger SiO2 particles. Successful coatings of SiO2 on SWNTs have been demonstrated. Silica appeared to be uniformly coated on the SWNTs surfaces. The thickness of the coating layer was found to be approximately 3-7 nm.