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.