Laser-Assisted Detection of Metal Nanoparticles in Liquid He-II

Area of Science:

• Physics
• Materials Science
• Nanotechnology

Background:

• Superfluid helium offers unique thermal properties for studying nanoparticle behavior.
• Laser-induced heating of plasmonic nanoparticles generates localized thermal effects.

Purpose of the Study:

• To investigate the formation and dynamics of gas bubbles around laser-heated copper nanoparticles in superfluid helium.
• To correlate gas bubble characteristics with the size of the parent nanoparticles.
• To validate a novel liquid-phase nanoparticle sizing technique.

Main Methods:

• Utilizing Schlieren imaging to visualize nanoparticle distribution and bubble formation.
• Employing laser heating of copper nanoparticles suspended in superfluid helium at 1.7 K.
• Validating results with atomic force microscopy (AFM) on deposited nanoparticles.

Main Results:

• Observed rapid (within 3 μs) growth of gas bubbles around laser-heated copper nanoparticles.
• Determined a relationship between gas bubble radii and the size of the parent nanoparticles.
• Confirmed nanoparticle size distribution in liquid helium using Schlieren imaging and AFM.

Conclusions:

• Gas bubble formation is a sensitive indicator of nanoparticle size in superfluid helium.
• Schlieren imaging provides a viable method for in-situ nanoparticle size analysis in cryogenic liquids.
• The study validates a new approach for characterizing nanoparticles in challenging environments.