Fabrication of silica nanoparticles on the surface of functionalized multi-walled carbon nanotubes

A method for the preparation of a hybrid material consisting of various size silica nanoparticles attached to multi-walled carbon nanotubes (MWCNTs) is proposed. Poly (acrylic acid) oligomer was first reacted with hydroxyl groups on acid-treated MWCNTs leading to a grafted encapsulation of the MWCNTs. These were subsequently reacted with 3-aminopropyltriethoxysilane (APTES) resulting sub-grafting of APTES on the MWCNTs. Such MWCNTs (siloxane-MWCNTs) were further hydrolyzed to make MWCNTs indirectly bearing Si–OH groups. Finally, a bud-like MWCNT/silica hybrid was obtained by forming a number of silica nanoparticles from Si–OH groups on the surface of MWCNTs by introducing siloxane-MWCNTs into a solution of tetraethyl orthosilicate, ammonia, and ethanol. The average size of the silica nanoparticles on the surface of the MWCNTs could be controlled by adjusting the concentration of ammonia and the reaction time.