Novel approach of controllable stoichiometric fabrication of alloyed Au/Ag nanoparticles by nanosecond laser ablation of thin bi-layered films in water

A novel approach was proposed and demonstrated to fabricate in a controllable manner alloyed colloidal Ag/Au nanoparticles with pre-determined stoichiometry from thin, magnetron-deposited bi-layered (Ag/Au) films of variable layer thickness by their nanosecond laser ablation in water. The optical properties of the obtained colloidal solutions were systematically analyzed, both experimentally and theoretically, indicating the alloyed character of the bimetallic nanoparticles as a monotonic 'red' spectral displacement of the localized plasmon resonance position, as well as gradual variation of its amplitude and width with increasing gold content in the bi-layered films. Transmission electron microscopy and energy dispersive x-ray spectroscopy support the alloyed rather than fragmentary character of the bimetallic nanoparticles, with the increasing gold content resulting in an increasing average nanoparticle size. This approach appears to be highly promising for the controllable on-demand fabrication of different bi- and poly-metallic nanoparticles with pre-determined stoichiometries.