Ag@Au core–shell nanoparticles synthesized by pulsed laser ablation in water: Effect of plasmon coupling and their SERS performance

Abstract

Ag@Au core–shell nanoparticles are synthesised by pulsed laser ablation in water using low energy laser pulses. The plasmon characteristics of these core–shell nanoparticles are found to be highly sensitive to the thickness of Au coating. In the synthesis, at first silver nanocolloid was prepared by ablating Ag target and then it is followed by ablation of Au target for different time durations to form Ag@Au core–shell nanostructures. The effect of plasmon–plasmon coupling on the absorption spectra is investigated by decreasing the effective distance between the nanoparticles. This is achieved by reducing the total volume of the colloidal suspension by simple evaporation of water, the solvent used. The suitability of these core–shell nanostructures for application as surface enhanced Raman scattering substrates are tested with crystal violet as probe molecules. Influence of plasmon coupling on the enhancement of Raman bands is found to be different for different bands.