Facile fabrication of superparamagnetic coaxial gold/halloysite nanotubes/Fe3O4 nanocomposites with excellent catalytic property for 4-nitrophenol reduction

A novel superparamagnetic gold/halloysite nanotubes/Fe3O4 (Au/HNTs/Fe3O4) nanocomposite with coaxial structure was designed and fabricated by selective decoration of the inner lumen and the external wall of halloysite nanotubes (HNTs) based on the difference inside/outside surface charges. The structure and composition of Au/HNTs/Fe3O4 were characterized by transmission electron microscope, powder X-ray diffraction, and X-ray fluorescence. The results indicated that Au nanorods selectively generated within the lumen of HNTs, while Fe3O4 nanoparticles uniformly deposited on the external wall. It was particularly worth mentioning that the structure of HNTs was not destroyed in the preparation process of Au/HNTs/Fe3O4 nanocomposites. The catalytic activity of the as-prepared Au/HNTs/Fe3O4 was investigated for the reduction of 4-nitrophenol in the presence of NaBH4. The Au/HNTs/Fe3O4 nanocomposites exhibited excellent catalytic activity and cycling stability according to the kinetic data of the catalytic reduction reaction. In addition, the Au/HNTs/Fe3O4 catalysts can be easily manipulated by an external magnetic field for recycling.