Size-Dependence of the photothermal response of a single metal nanosphere

Abstract

We study the thermal response of a single spherical metal nanoparticle to continuous wave illumination as a function of its size. We show that the particle temperature increases non-monotonically as the particle size increases, indicating that the photo-thermal response can be optimized by tuning the particle size and illumination wavelength. We also compare the size-effect on the photo-thermal effects of gold and silver nanoparticles and find somewhat surprisingly that Ag NPs are more efficient heat generators only for sufficiently small sizes. These results have importance primarily for application such as plasmon-assisted photo-catalysis, photothermal cancer therapy, etc., and provide a first step toward the study of the size-dependence of the thermo-optic nonlinearity of metal nanospheres.