Formation of Au–Pt bimetallic nanoparticles in a two-layer SiO2 films doped with Au and Pt, respectively, through interlayer diffusion

Abstract

Bimetallic Au–Pt nanoparticles have been generated inside a relatively porous SiO₂ film matrix by a two-layer (2L) coating methodology. Two overlapping coating layers were deposited on glass substrates from Au- and Pt-doped inorganic–organic hybrid silica sols and air dried at 60 °C. The 2L coating assembly was then UV- and followed by heat-treated at 450 and 550 °C in air. UV-treatment decomposes AuCl₄⁻ and PtCl₆²⁻ ions in the respective layers and the subsequent heat treatment in air influences the diffusion of Au and Pt nanometals to each other to form bimetallic Au–Pt nanoparticles inside the silica matrix. A UV-visible study showed damping of Au-plasmon after heat treatments. GIXRD and TEM analyses reveal the formation of a partial Au/Pt solid solution with a small fraction of Pt (∼16%), while the major fraction of Pt remains fused with the Au(Pt) solid solution.