Fabrication of TiO2-coated magnetic nanoparticles on functionalized multi-walled carbon nanotubes and their photocatalytic activity

A novel magnetic photocatalyst with a hybrid nanostructure consisting of multi-walled carbon nanotubes (MWCNTs), Fe3O4 nanoparticles and a TiO2 layer was prepared. First of all, poly(acrylic acid) (PAA) was grafted onto the surface of MWCNTs by in situ polymerization. Fe3O4 nanoparticles were then anchored on PAA chains through amidation reaction between the amino groups on the surface of the Fe3O4 nanoparticles and the carboxyl groups of PAA. Finally, a TiO2 layer was coated onto the surface of the modified MWCNTs through hydrogen bonding interactions between the hydroxyl groups on the surface of titanium dioxide and the carboxyl groups of PAA or the amino groups of Fe3O4. The morphology and structure of the intermediate and final hybrids were investigated by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The magnetism of the product was characterized using a vibrating sample magnetometer. It was shown that the TiO2 decoration shifts the absorbance spectrum of the hybrid to the entire UV–vis region. The photo-catalytic function of the MWCNT/Fe3O4/TiO2 hybrids was validated for phenol degradation under irradiation of UV–vis light.