Growth Processes of Nanoparticles in Liquid-Phase Laser Ablation Studied by Laser-Light Scattering

Abstract

We applied laser-light scattering for investigating the growth processes of nanoparticles in liquid-phase laser ablation. We observed the growth of nanoparticles inside the cavitation bubble. This means that particles ejected from the target are transported into the cavitation bubble, and they condense into nanoparticles inside it. The production of nanoparticles was efficient until 3 s after the irradiation of the laser pulse for ablation, indicating the fast growth of nanoparticles. A part of nanoparticles was transported from the cavitation bubble toward the water, but the great portion of nanoparticles was stored in the cavitation bubble until the collapse.

Liquid-phase laser ablation

“…In addition, if nanoparticles are stored inside the cavitation bubble, there is a possibility that nanoparticles are in the high-pressure, high-temperature reaction field at the collapse. To answer these questions, we carried out in situ detection of nanoparticles by laser light scattering [18,19]. The experimental apparatus was similar to Fig.…”

Discharge phenomena in a cavitation bubble induced by liquid-phase laser ablation

“…This may be a unique feature of the cavitation bubble induced by liquid-phase laser ablation, since the deformation of the cavitation bubble is not observed when it is produced by an ultrasonic power [26,27]. Since it has been found that the growth field of nanoparticles in liquid-phase laser ablation is the inside of the cavitation bubble [36][37][38][39][40], the present experimental results may explain the origin of the high zeta potential of the colloidal solution synthesized by liquid-phase laser ablation. …”

“…The experimental results are consistent with a model calculation which assumes free charges on the gas-liquid boundary. Since it has been shown that the growth field of nanoparticles in liquid-phase laser ablation is the inside of the cavitation bubble [36][37][38][39][40], it is suggested that the origin of the high zeta potential of the colloidal solution synthesized by liquid-phase laser ablation is the electrical charges stored in the cavitation bubble.…”

Spectrum of laser light scattered by nanoparticles in an ablation-induced cavitation bubble

“…3(c), the wavelength-shifted component was also observed from the outside of the cavitation bubble. This is because a part of nanoparticles in the cavitation bubble are ejected into water in the expansion phase and at the collapses [4,12]. Therefore, water around the rebounded cavitation bubble contains ejected nanoparticles which are detected as the wavelength-shifted component in this experiment.…”

“…We have given an answer to this question by carrying out simultaneous imaging of shadowgraph and laser-light scattering [12]. The experimental result clearly shows the growth of nanoparticles inside the cavitation bubble.…”