Synthesis of monosized core–shell Fe3O4/Au multifunctional nanoparticles by PVP-assisted nanoemulsion process

Monosized core–shell Fe3O4/Au magnetic–optic multifunctional nanoparticles were synthesized by a modified nanoemulsion process. The formation of the core–shell nanostructure was accomplished in the presence of poly(vinylpyrrolidone) (PVP) as the surfactant in two consecutive steps. The comparison FTIR study proves the PVP coating on the surface of the resultant nanoparticles, whereas the morphological analysis illustrates the nanoparticle shape, nanostructuring, size and size distribution and shows the excellent monodispersity <10%. The crystal structure of the core–shell nanoparticles is revealed by the XRD patterns, with the single-crystallinity of such individual nanoparticles illustrated by the lattice imaging. Moreover, the nanoparticles manifest soft ferromagnetic behavior with a small coercivity of ∼40 Oe at room temperature and ensuing excellent susceptibility. The magnetic hysteresis curves of the nanoparticles were elucidated by a modified Langevin equation, giving estimation of the effective magnetic dimension of the nanoparticles and reflecting the enhanced susceptibility response as a result of the surface covering. The UV–vis spectroscopic examination reveals the well-behaved surface plasmon at ∼590 nm. Thus, the use of PVP has evidently led to the improved structure and properties, anticipating application potentials of the nanoparticles.