Core-shell like Au-Ir nanoparticles with spatially variant electronic state of Au synthesized by femtosecond laser irradiation of solution

In this work, nanoparticles were obtained via laser-induced nucleation. Specifically, the fabrication of Au-Ir core-shell like nanoparticles was demonstrated, based on the femtosecond laser irradiation of aqueous solution of HAuCl ₄ and H ₂ IrCl ₆ . UV–vis transmission spectra showed that the metal ions were reduced and nanoparticles were generated in response to the laser irradiation of these solutions. In addition, elemental mapping by energy dispersive X-ray spectroscopy confirmed a core (Ir)-shell (Au) in which a portion of the Ir was exposed to the surface. The formation of this nanostructure is ascribed to the relative probabilities of interactions between the incident laser light and the two types of anions. Electron energy loss spectroscopy demonstrated that the electronic states in the Au region of Au7Ir3 core-shell like nanoparticles were quite different from those of pure Au nanoparticles and also exhibited spatial variations. We propose that the strain at the Au/Ir interface induced by a lattice mismatch could be responsible for the spatial variation of the electronic states.