Evolution of the microstructure, chemical composition and magnetic behaviour during the synthesis of alkanethiol-capped gold nanoparticles

In the present paper, we show an exhaustive microstructural characterization of thiol-capped gold nanoparticles (NPs) with two different average particle sizes. These samples are compared with the polymer-like Au(I) phase formed as a precursor during the synthesis of the thiol-capped gold NPs. The set of analysed samples shows different microstructures at the nanoscale with different proportions of Au atoms bonded either to S or to Au atoms. It has been experimentally shown that the presence of a ferromagnetic-like behaviour is associated to the formation of NPs with simultaneous presence of Au–Au and Au–S bonds. In order to explain such magnetic behaviour a possible model is proposed based on the spin–orbit coupling so that localized charges and/or spins (Au–S bonds) can trap conduction electrons (Au–Au bonds) in orbits.