Formation of Ag/Pt bimetallic nanoparticles obtained by ion implantation in α − Al2O3

Abstract

Metallic nanoparticles embedded in dielectric matrices are attractive for their non-linear optical properties, which result primarily from their surface plasmon resonance, which in most cases, are located at a frequency within the visible range. The properties of bimetallic nanoparticles are well known to depend on their size, form, composition and structure. The possibility of tuning these properties by controlling the composition or structure of bimetallic nanoparticles on dielectric surfaces has attracted much attention recently, principally using SiO2 as the host surface.In this paper, we synthesised Ag/Pt nanoparticles embedded in α − Al2O3 by Ag and Pt sequential ion irradiation of a pristine α − Al2O3 matrix. We used post-annealing treatments to induce the nucleation and growth of the nanoparticles to be studied. The characterisation of the linear optical behaviour was carried out through Optical Extinction Spectroscopy, while Scanning Electron Microscopy (SEM) provided additional information on the size and shape of the nanoclusters within the samples. X-Ray Diffraction (XRD) provides valuable evidence of the presence of the Ag15Pt17 phase in some of the samples.Our results show that the nanoparticles’ structure depends principally on the sequence of the ion implantation and the thermal annealing used. When Pt ions are implanted first, stable enough Pt clusters form, and core-shell structures predominate, as seen in the optical extinction spectrum by the presence of the Ag local surface plasmon resonance (LSPR). On the other hand, when silver ions are first implanted, the surface plasmon resonance is not present, meaning that a Ag − Pt nano alloy is predominant.