Water-Dispersible Spherically Hollow Clusters of Magnetic Nanoparticles

We reported the synthesis of various water-dispersible clusters of magnetic nanoparticles by self-assembly of a cyclodextrin−polymer surfactant (CD−polymer) complex under one-pot reaction in an aqueous medium. Several polymer surfactants are selected to study their effects on size and morphology of magnetite nanoparticle clusters. They are polyethylene glycol (n) nonylphenyl ether series, NPEn (where n = 5, 9, 30), Brij-97, and Triton X-114. The effect of self-assembly of CD−polymer complexes, which were made up of hydrophilic and hydrophobic groups from the polymer surfactants with CDs, on the cluster formation was also investigated. Depending on the reaction conditions, the structure of the clusters of magnetic nanoparticles can be tuned from mesoporous, to hollow, and to solid by the judicious selection of polymer surfactants. It was also found that an increase in the number of hydrophilic groups of the polymer surfactants caused the size of the Fe3O4 nanoparticle clusters to increase. In addition, the self-assembled clusters of the Fe3O4 nanoparticle cannot be prepared if the hydrophobic groups of the polymer surfactants cannot be effectively associated with CDs. The Brunauer−Emmett−Teller surface areas and magnetic properties of these nanostructured spherical clusters of Fe3O4 nanoparticles were also measured. Other characterizations including Fourier transform infrared, X-ray diffraction, and thermogravimetric analysis were also investigated.