Effect of pulsed laser irradiation on the thermal diffusivity of bimetallic Au/Ag nanoparticles

Abstract

Bimetallic Au/Ag nanoparticles have been synthesized by laser ablation technique using a pulsed Nd:YAG laser with fundamental wavelength of 1064 nm. Initially, gold nanoparticles were synthesized in PVP solution by the ablation technique. For the generation of bimetallic Au/Ag nanoparticles, a silver plate was ablated for different time durations in the already synthesized colloidal gold nanoparticle solution. These source samples were further subjected to pulsed laser irradiation using a Q-switched frequency doubled Nd:YAG laser at a wavelength of 532 nm for varying time periods. Formation of the bimetallic nanoparticles was confirmed by Transmission Electron Microscopy (TEM) as well as absorption spectroscopy. Stability of the samples was established by the zeta potential analysis. Thermal diffusivity of the samples was determined using a dual-beam mode matched thermal lens technique at two different pump wavelengths. A systematic increase in the thermal diffusivity values was observed with increase in the ablation time of silver plate in gold nanoparticle solution which is attributed to the morphological variations occurring to the bimetallic nanoparticles. The effect of laser irradiation on the thermal diffusivity values was also investigated. An increase in thermal diffusivity was observed as the laser irradiation time increased due to the agglomeration of the bimetallic nanoparticles. The study can act as the basis for using plasmonic bimetallic nanoparticles as a nanoheat source in the medical field applications.