Effect of plasmonic coupling on photothermal behavior of random nanoparticles

In this paper, the effect of plasmonic coupling on the photothermal behavior of a random distribution of silver nanoparticles is investigated. The spatial profiles of the temperature increase for illuminated nanoparticles have been computed by means of discrete dipole approximation method and thermal Green's function. Our results show that in a random assembly of nanoparticles the effects of plasmonic coupling with other nanoparticles and thermal accumulation lead to a photothermal behavior for nanoparticles which is different from the one with an isolated single nanoparticle. The separate contributions of plasmonic coupling and thermal accumulation effects to temperature increase of nanoparticles assembly have been determined qualitatively. Based on obtained results, for wavelengths far from the plasmonic resonance of a single nanoparticle, the plasmonic coupling between clustered nanoparticles can heat up nanoparticles to significant high temperature which it cannot be expected for the case where the plasmonic coupling is assumed to be ignored (where nanoparticles only can interact due to the thermal accumulation). On the other hand, at the plasmonic resonance wavelength of a single nanoparticle, plasmonic coupling between clustered NPs causes the temperature increase to be lower in comparison with the case which the clustered nanoparticles are assumed as an assembly of individual non-coupled nanoparticles. Our results help to have a better understanding of the physics of photo heating of random nanoparticles in biological applications.