Enhanced nonlinear and thermo optical properties of laser synthesized surfactant-free Au-Pt bimetallic nanoparticles

Abstract

The Au and Pt nanoparticles were synthesized employing laser ablation in water. Ligand-free Au-Pt bimetallic nanoparticles were generated by means of laser irradiation of the colloidal mixture of Au and Pt nanoparticles. The nonlinear optical characteristics like nonlinear absorption coefficient, nonlinear refractive index, optical limiting threshold and non linear optical susceptibility of Au, Pt, their colloidal mix and bimetallic nanoparticles were determined via Z scan method. All nanoparticle samples exhibited strong reverse saturable absorption behaviour with positive value of nonlinear absorption coefficient and strong optical limiting efficiency. The non linear absorption and refraction characteristics were found to be considerably enhanced for the Au-Pt bimetallic nanoparticles than the corresponding mono metallic nanoparticles and the pre-irradiation colloidal mix. The thermo optical features were also studied using thermal lens method and found to be tunable by controlling the fraction of Au and Pt in the bimetallic nanoparticles. To the best knowledge of the authors, it is presumed that, the present work is the first report on the non linear and thermo optical characterization of Au-Pt bimetallic nanoparticles. The present work has significance in nonlinear optical and photo thermal applications like optical limiting, photo thermal therapy and photo acoustic imaging.