Nanoparticle Fragmentation below the Melting Point under Single Picosecond Laser Pulse Stimulation

Abstract

Understanding the laser−nanomaterial interactions that lead to nanomaterial fragmentation is important for nanoparticle manufacturing, energy, and biomedical sciences. So far, three mechanisms of laser-induced fragmentation have been recognized including non-thermal processes and thermomechanical force under femtosecond pulses and the phase transitions under nanosecond pulses. Here, we show that single picosecond (ps) laser pulse stimulation leads to an anomalous fragmentation of gold nanoparticles that deviates from these three mechanisms. The ps laser fragmentation was weakly dependent on the particle size, and it resulted in a bimodal size distribution. Importantly, ps laser stimulation fragmented particles below the whole particle melting point and below the threshold for a non-thermal mechanism. We propose a framework based on near-field enhancement and nanoparticle surface melting to account for the ps laser-induced fragmentation observed here. This study reveals a new form of surface ablation that occurs under ps laser stimulation at a low fluence.

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