Magneto-plasmonic Au-Fe Nanoparticles
Laser-generated magneto-plasmonic Au-Fe Nanoparticles: Formation Machanism, Real Structure and Properties
The combination of elements with different functionality into a single nanoparticle is a promising route to the design of multifunctional alloy nanoparticles. In biomedical applications, for instance, nanoparticles made of distinct metals are of special interest because of their unique properties: iron as a magnetic agent for resonance imaging (MRI) or magnetic thermotherapy and gold for its optical properties and its capability to be easily functionalized by thiolated biomolecules. Such alloy nanoparticles have also attracted attention in catalysis or spectroscopy. Apart from the composition, the real intra-particle structure of binary alloy nanoparticles determines their properties. The real ultrastructure may consist of a homogeneous phase (solid-solution) or phase separations which can be characterized using advanced high-resolution electron microscopy. In a Fe-Au core-shell structure, an inert shell (gold) can protect a reactive core (iron) from oxidation thereby conserving high magnetization of the core and delivering plasmon resonance by the shell. HRTEM, ED, HAADF-STEM and tomography are used to detect the structure and morphology of the nanoparticles, EDX and EELS/EFTEM can be utilized to reveal the chemical composition.