Laser-Induced Plasmonic Nanobubbles and Microbubbles in Gold Nanorod Colloidal Solution

Area of Science:

• Nanotechnology
• Optics
• Acoustics

Background:

• Pulsed lasers can induce optical breakdown and microbubble formation in water.
• Gold nanorods (GNRs) exhibit surface plasmon resonance (SPR), enhancing photothermal effects.
• Understanding the dynamics of laser-induced bubbles in colloidal solutions is crucial for various applications.

Purpose of the Study:

• To investigate the initiation of plasmonic nanobubbles and subsequent microbubbles in GNR colloids using pulsed lasers.
• To determine the effect of GNR concentration and laser wavelength on microbubble generation thresholds.
• To characterize different types of laser-induced microbubbles in GNR solutions.

Main Methods:

• Utilized pulsed lasers at 700 nm and 980 nm to irradiate dilute GNR colloids with different SPRs.
• Employed a probing He-Ne laser, photodetector, and ultrasonic transducer to monitor bubble dynamics.
• Analyzed optical and photoacoustic signals to identify and classify microbubble formation types.

Main Results:

• GNRs significantly reduce the pulsed laser energy threshold for microbubble generation via SPR-enhanced photothermal effects.
• Three types of microbubbles were identified: single, coalesced, and splitting, corresponding to different breakdown events.
• Lowering GNR concentration and using NIR laser wavelengths near SPR reduced energy thresholds, especially for dilute colloids.

Conclusions:

• Dilute GNR colloids effectively facilitate laser-induced microbubble generation, particularly in the NIR bio-optical window.
• The findings suggest potential for GNR-assisted laser-induced microbubbles in biomedical applications.
• This study provides insights into the relationship between plasmonic nanobubbles and triggered microbubbles.