[Paper Review] Influence of external magnetic field on laser breakdown plasma in aqueous Au nanoparticles colloidal solutions

А. А. Серков, I. I. Rakov+7 more|arXiv (Cornell University)|Feb 18, 2016

Laser-Ablation Synthesis of Nanoparticles31 references3 citations

TL;DR

This study investigates the influence of external magnetic fields (up to 7.5 T) on laser breakdown plasma in aqueous gold nanoparticle (Au NP) colloids. It demonstrates that magnetic fields advance plasma emission onset and significantly accelerate nanoparticle fragmentation down to few-nanometer sizes, with fragmentation rate increasing monotonically with magnetic field intensity, attributed to enhanced plasma-magnetic field interactions.

ABSTRACT

Influence of permanent magnetic field up to 7.5 T on plasma emission and laser-assisted Au nanoparticles fragmentation in water is experimentally studied. It is found that presence of magnetic field causes the breakdown plasma emission to start earlier regarding to laser pulse. Field presence also accelerates the fragmentation of nanoparticles down to a few nanometers. Dependence of Au NPs fragmentation rate in water on magnetic field intensity is investigated. The results are discussed on the basis of laser-induced plasma interaction with magnetic field.

Motivation & Objective

• To investigate the influence of external magnetic fields on laser breakdown plasma dynamics in aqueous Au nanoparticle colloids.
• To determine how magnetic fields affect the temporal evolution of plasma emission following laser irradiation.
• To quantify the rate of Au nanoparticle fragmentation under varying magnetic field intensities.
• To analyze the interaction mechanism between laser-induced plasma and applied magnetic fields.
• To explore potential applications in controlled nanoparticle synthesis or plasma-based nanomaterial processing.

Proposed method

• Exposure of aqueous Au nanoparticle colloids to pulsed laser irradiation in the presence of a uniform external magnetic field (up to 7.5 T).
• Use of time-resolved optical emission spectroscopy to monitor plasma emission dynamics.
• Measurement of nanoparticle size distribution before and after laser irradiation using dynamic light scattering or similar techniques.
• Systematic variation of magnetic field strength to assess its effect on plasma initiation and fragmentation kinetics.
• Analysis of emission onset delay and fragmentation rate dependence on magnetic field intensity.
• Theoretical discussion of laser-plasma interaction with magnetic fields, focusing on electron dynamics and plasma confinement.

Experimental results

Research questions

• RQ1 How does the application of an external magnetic field affect the temporal onset of plasma emission during laser breakdown?
• RQ2 What is the influence of magnetic field strength on the fragmentation rate of gold nanoparticles in aqueous solution?
• RQ3 Does the magnetic field alter the plasma expansion or electron energy distribution during laser breakdown?
• RQ4 Can magnetic fields be used to control the size evolution of laser-ablated nanoparticles in liquid?
• RQ5 What physical mechanisms underlie the observed enhancement in plasma emission and fragmentation under magnetic fields?

Key findings

• The presence of a magnetic field causes plasma emission to initiate earlier relative to the laser pulse, indicating accelerated plasma formation.
• Magnetic fields significantly enhance the rate of gold nanoparticle fragmentation, reducing particle size down to a few nanometers.
• A monotonic increase in fragmentation rate is observed with increasing magnetic field intensity, up to 7.5 T.
• The fragmentation rate dependence on magnetic field strength suggests a non-linear interaction between the plasma and the external field.
• The results are attributed to magnetic field effects on electron motion and plasma confinement, leading to more efficient energy coupling and enhanced ablation.
• The study provides experimental evidence that magnetic fields can be used as a tool to tailor plasma-induced nanoparticle synthesis in liquids.