Nanoparticle Fragmentation Below the Melting Point Under Single Picosecond Laser Pulse Stimulation

Area of Science:

• Materials Science
• Nanotechnology
• Laser Physics

Background:

• Laser-nanomaterial interactions are crucial for nanoparticle manufacturing, energy applications, and biomedical sciences.
• Existing models describe laser-induced nanoparticle fragmentation via non-thermal processes, thermomechanical forces (femtosecond pulses), and phase transitions (nanosecond pulses).

Purpose of the Study:

• To investigate the anomalous fragmentation of gold nanoparticles induced by single picosecond (ps) laser pulses.
• To elucidate the underlying mechanisms of ps laser-induced nanoparticle fragmentation, which deviate from established models.

Main Methods:

• Stimulation of gold nanoparticles using single picosecond (ps) laser pulses.
• Analysis of fragmentation patterns, particle size distribution, and dependence on laser fluence and particle size.
• Development of a theoretical framework to explain the observed fragmentation phenomena.

Main Results:

• Picosecond laser pulses induced anomalous fragmentation of gold nanoparticles, independent of particle size and resulting in a bimodal size distribution.
• Fragmentation occurred below the bulk melting point of gold and below the threshold for non-thermal fragmentation mechanisms.
• A novel surface ablation mechanism was identified for ps laser stimulation at low fluences.

Conclusions:

• Picosecond laser pulse interaction with gold nanoparticles presents a new fragmentation pathway distinct from femtosecond and nanosecond pulse regimes.
• The proposed mechanism involves near-field enhancement and nanoparticle surface melting, explaining fragmentation at low fluences.
• This discovery offers new insights into laser-induced nanomaterial modification with potential applications in advanced manufacturing.