Au/Ag composite nanorings based on galvanic reaction of the Ag nanoparticles induced by laser ablation in water

Abstract

A simple route is presented to fabricate Au/Ag composite nanorings based on the galvanic reaction of the silver colloidal solution by addition of chloroaurate solution. The silver colloidal solution with near monodispersion in size is firstly prepared by laser ablation of Ag target in pure water and subsequent additional irradiation. It has been found that addition of chloroaurate solution to the Ag colloidal solution can produce the Au/Ag composite nanoparticles, which are the ring-like Ag single crystals embedded with ultrafine Au nanoparticles. Further experiments have revealed that appropriate molar ratio of Au to Ag in the solution and round original Ag nanoparticles are crucial to formation of such composite nanorings. This study provides a simple way to fabricate noble metal nanorings with different sizes. Such composite nanorings have exhibited the surface plasmon resonance properties in near-infrared (NIR) bands and could thus be used as the NIR-excited surface enhanced Raman scattering (SERS) substrates for detection of trace amount molecules and some other nanophotonic devices.