Fabrication of well-defined superparamagnetic rattle-type Fe3O4@polyaniline hollow microspheres with large cavity

Well-defined superparamagnetic Fe3O4/SiO2/polyaniline (PANi) core–shell–shell microspheres with smooth surface are synthesized as the first time. Fe3O4/SiO2 core–shell microspheres modified by poly(vinylpyrrolidone) (PVP) are coated with PANi through in situ polymerization of aniline monomers in ethanol dispersion. Low polymerization temperature is a key factor for coating PANi on the surface of silica. Rattle-type Fe3O4@PANi hollow microspheres are obtained and the outermost rigid PANi layer could be kept with the hollow structure after etching spacer silica layers by NaOH. The thickness of PANi layer could be controlled by adjusting the concentration of aniline. The cavity size of rattle-type Fe3O4@PANi hollow microspheres is related to the thickness of spacer silica layer. As a potential carrier for catalysts, gold nanoparticles are loaded in cavities of the rattle-type Fe3O4@PANi hollow microspheres.