Why the magnetite–gold core–shell nanoparticles are not quite good and how to improve them

The nature of the formation of a chemical bond at the magnetite–gold interface has been studied. The geometric structure and the electronic and magnetic properties of plane layers consisting of magnetite Fe$_3$O$_4$ and gold have been investigated using the DFT-GGA calculation. It has been found that the specific energy and the wetting parameter of the magnetite–gold interface are negative, which leads to the island growth of small Au particles on the Fe$_3$O$_4$ surface. The role of an intermediate thin titanium layer between magnetite and gold has been discussed. The specific energy and wetting parameter of the magnetite–titanium (for thin Ti layers) and magnetite–titanium–gold interfaces are positive. It has been suggested that an intermediate thin titanium layer at the interface between the magnetite nanoparticle surface and the gold layer will make it possible to obtain magnetite nanoparticles with a continuous gold coating.