Fluence Threshold for Photothermal Bubble Generation Using Plasmonic Nanoparticles

Under nano- to femtosecond pulsed illumination at their plasmonic resonance wavelength, metal nanoparticles efficiently absorb the incident light energy that is subsequently converted into heat. In a liquid environment, with sufficiently high pulse fluences (light energy per unit area), this heat generation may result in the local formation of a transient nanobubble. This phenomenon has been the subject of a decade of investigations and is at the basis of numerous applications from cancer therapy to photoacoustic imaging. The aim of this article is to clarify the question of the fluence threshold required for bubble formation. Using a Runge-Kutta-4 numerical algorithm modeling the heat diffusion around a spherical gold nanoparticle, we numerically investigate the influence of the nanoparticle diameter, pulse duration (from the femto- to the nanosecond range), wavelength, and Kapitza resistivity in order to explain the observations reported in the literature.