Tuning the nonlinear optical properties of Au@Ag bimetallic nanoparticles

Abstract

In this work, we report the nonlinear optical properties of Au@Ag bimetallic nanoparticles synthesized by a seed-mediated method. For the synthesis of bimetallic nanoparticles, gold seeds with particle size of 18 nm were synthesized by citrate assisted thermal reduction method, followed by the reduction of silver ions with ascorbic acid. The nanoparticles were characterized by means of UV–Vis spectrophotometry, SEM and Z-scan measurements with an Argon CW laser of variable power at 514 nm was used to determine the nonlinear optical properties. Au@Ag core-shell nanoparticles presents negative and positive nonlinear absorption coefficient and the nonlinear refraction index is negative. Moreover, the results show that the nonlinear optical properties can be tailor modifying the thickness of shell.