Non-aqueous synthesis of water-dispersibleFe3O4–Ca3(PO4)2 core–shell nanoparticles

Abstract

The Fe3O4–Ca3(PO4)2 core–shell nanoparticles were prepared by one-pot non-aqueous nanoemulsion with theassistance of a biocompatible triblock copolymer, poly(ethylene glycol)-block-poly(propyleneglycol)-block-poly(ethylene glycol) (PEO–PPO–PEO), integrating the magnetic properties ofFe3O4 and the bioactivefunctions of Ca3(PO4)2 intosingle entities. The Fe3O4 nanoparticles were pre-formed first by thermal reduction ofFe(acac)3 and thenthe Ca3(PO4)2 layer was coated by simultaneous deposition ofCa2 + andPO43 − . The characterization shows that the combination of the two materialsinto a core–shell nanostructure retains the magnetic properties and theCa3(PO4)2 shell forms anhcp phase (a = 7.490 Å, c = 9.534 Å) onthe Fe3O4 surface. The magnetic hysteresis curves of the nanoparticles were further elucidated by theLangevin equation, giving an estimation of the effective magnetic dimension of thenanoparticles and reflecting the enhanced susceptibility response as a result of the surfacecovering. Fourier transform infrared (FTIR) analysis provides the characteristic vibrations ofCa3(PO4)2 and the presence of the polymer surfactant on the nanoparticle surface. Moreover, thenanoparticles could be directly transferred to water and the aqueous dispersion–collectionprocess of the nanoparticles was demonstrated for application readiness of suchcore–shell nanostructures in an aqueous medium. Thus, the construction ofFe3O4 andCa3(PO4)2 in the core–shell nanostructure has conspicuously led to enhanced performance andmulti-functionalities, offering various possible applications of the nanoparticles.