Facile and Green Approach To Fabricate Gold and Silver Coated Superparamagnetic Nanoparticles

Superparamagnetic magnetite nanoparticles are coated with homogeneous gold and silver shells using a simple aqueous based seed mediated method at room temperature with dopamine as a surfactant. Nanoparticles of Au in the range 2−3 nm are attached to amine functionalized Fe 3 O 4 nanoparticles, acting as seed for the growth of ultrathin Au or Ag shells. The monodispersed core−shell nanoparticles Fe 3 O 4 @Au and Fe 3 O 4 @Ag have a particle size range of 10−13 nm with a shell thickness of approximately 2−3 nm. They are magnetically purified and are superparamagnetic at 300 K with saturated magnetization values of 41 and 35 emu g −1, respectively.