The synthesis and characterization of polymer-coated FeAu multifunctional nanoparticles

Abstract

We report the one-pot nanoemulsion synthesis of FeAu magnetic-optical multifunctionalnanoparticles coated by the biocompatible triblock copolymer, poly(ethyleneglycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEO-PPO-PEO). The FTIRstudy confirms the PEO-PPO-PEO molecules on the surface of the resulting nanoparticles.The structural characterization identifies the crystallographic parameter 4.072 Å of the cubicphase and the morphology analysis gives the nanoparticle shape, size and size distribution,showing the high crystallinity of the FeAu nanoparticles and an average particle size of ∼ 6.5 nm. In addition there is direct confirmation of the alloying by elemental point probing of anindividual nanoparticle. Following the visual demonstration of a rapid, efficient and reversibledispersion–collection process of the nanoparticles in solution, the magnetic measurementmanifests a soft ferromagnetic behavior of the nanoparticles with a small coercivity of ∼ 60 Oe at room temperature. The corresponding magnetic hysteresis curves were effectivelyassessed by modified bi-phase Langevin equations, which were satisfactorily explained interms of a bimodal particle size distribution. The UV–vis studies display the broadbandabsorption of the PEO-PPO-PEO-coated nanoparticles with the maximum surface plasmonresonance around 585 nm. The characterization and analysis, therefore, shows theunification of iron and gold into one alloy nanostructure entity covered by thebiocompatible triblock copolymer thin film, preserving the optical and magnetic propertiesof the individual constituents. This gives the prospect of enhanced performance inapplications.