From Thermo- to Plasma-Mediated Ultrafast Laser-Induced Plasmonic Nanobubbles

Abstract

The laser-induced generation of vapor bubbles around gold nanoparticles (AuNPs) is a promising diagnostic and therapeutic avenue for various pathologies. The physical mechanism that leads to their formation strongly depends on the time regime of the irradiation. While the plasmonic nanobubbles induced by nanosecond and picosecond laser pulses are known to be triggered by the energy that is absorbed in the nanoparticles and diffused in the medium (thermo-mediated cavitation), we show that a different plasma-mediated mechanism occurs in the case of femtosecond pulses. In this paper, we present experimental evidence that the dimensions of laser-induced bubbles depend on the polarization of the incident laser pulse when the pulse duration is reduced below ∼1 ps. This result cannot be explained by the standard thermo-mediated cavitation process and, thus, reveals the onset of a new mechanism in the ultrafast regime. We further show that the discrepancy between the dimensions of bubbles generated from linearly and circularly polarized laser pulses can be explained using a simple model, revealing the polarization cavitation dependence as a clear signature of the plasma mechanism. This paper presents in detail the transition between both cavitation regimes and provides insight into the precise control of the cavitation dynamics at the nanoscale.

Dynamic imaging of a single gold nanoparticle in liquid irradiated by off-resonance femtosecond laser

“…Plasmonic NP assisted cell nanosurgery is facilitated by transient sub-micron bubbles generated in close proximity to cells due to NPs excitation. Bubble generation and evolution strongly depends on the laser parameters such as pulse duration, wavelength and fluence 1,[6][7][8][9] . In particular, bubble generation has been mainly associated to NP heating and vaporization of the surrounding liquid when on-resonance laser irradiation is used 1,10 .…”

“…on-resonance peak wavelength 579 nm for 100 nm gold NP (AuNP)) maximizes the laser pulse energy absorption by the NPs due to their high absorption cross section. Recently, we proposed a nanoplasma mediated bubble generation mechanism for laser cell nanosurgery applications based on off-resonance femtosecond (fs) laser excitation (wavelength 800 nm) of plasmonic AuNPs 7,11 . In the off-resonance excitation, the energy absorption by the AuNPs is minimized due to their low absorption cross section.…”

Laser-assisted photoporation: fundamentals, technological advances and applications

“…The plasma relaxes and transfers its energy to the water, in turn leading to nanobubble formation ( Figure 6 b down panel adapted from Figure 2, see Refs. [117] and [134]). (c) Photoporation of the cell membrane may also be caused by photochemical reactions that are triggered by multiphoton ionization of water and the generation of ROs.…”

“…Apart from heat also plasma formation can lead to nanobubbles [123,134] (Figure 6(b), adapted figure in Ref. [134]).…”

“…The plasma cools down by collision and recombination with water molecules, hence producing a quick temperature and pressure increase and leading to the generation of a water VNB around the irradiated NP. The use of plasma-mediated nanobubbles was first reported by the Meunier group, who used fs pulsed laser (45 fs) irradiation of 100 nm gold nanospheres [123,134,135]. Under these conditions, they found that the threshold of plasma-mediated nanobubble formation is ~100 mJ/cm 2 .…”