Gas–Vapor Interplay in Plasmonic Bubble Shrinkage

The
understanding of the shrinkage dynamics of plasmonic bubbles
formed around metallic nanoparticles immersed in liquid and irradiated
by a resonant light source is crucial for the usage of these bubbles
in numerous applications. In this paper, we experimentally show and
theoretically explain that a plasmonic bubble during its shrinkage
undergoes two different phases: first, a rapid partial bubble shrinkage
governed by vapor condensation and, second, a slow diffusion-controlled
bubble dissolution. The history of the bubble formation plays an important
role in the shrinkage dynamics during the first phase as it determines
the gas–vapor ratio in the bubble composition. Higher laser
powers lead to more vaporous bubbles, while longer pulses and higher
dissolved air concentrations lead to more gaseous bubbles. The dynamics
of the second phase barely depends on the history of bubble formation,
that is, laser power and pulse duration, but strongly on the dissolved
air concentration, which defines the concentration gradient at the
bubble interface. Finally, for the bubble dissolution in the second
phase, with decreasing dissolved air concentration, we observe a gradual
transition from a R(t) ∝
(t0 – t)1/3 scaling law to a R(t) ∝
(t0 – t)1/2 scaling law where t0 is the lifetime
of the bubble and theoretically explain this transition.