Study and characterization of the gold nanoparticle’s formation mechanism by re-irradiation of linear bromide-induced gold nanoparticle chains

Noble metal nanoparticles (NPs) exhibit unique size- and shape-dependent optical properties, making their controlled synthesis a key challenge for applications in sensing, photonics, and nanomedicine. Pulsed Laser Ablation in Liquid (PLAL) and its related techniques, Pulsed Laser Fragmentation (PLFL) and Pulsed Laser Melting (PLML), provide a chemical-free approach for producing NPs with controlled size and shape. In this work, we investigate the laser-induced disruption dynamics of bromide-induced gold NP (Au NP) chains in aqueous solution, using pulsed laser re-irradiation at different fluences and wavelengths. Through UV-Vis absorption spectroscopy, Surface Enhanced Raman Scattering (SERS), and electron microscopy, we demonstrate that chain disruption and NP fragmentation coexist, depending on laser fluence. At the lowest fluence, the chain disruption is slow with no fragmentation, while at the higher fluences the chain disruption is faster, with fragmentation that is more extended for higher fluences. Kinetic analysis shows that the process follows an Arrhenius-type behavior. Furthermore, we show that irradiation in resonance with the transverse LSPR (532 nm) is significantly more efficient than off-resonance (1064 nm), suggesting a plasmon-driven phenomenon. This work, beside investigating the fundamental mechanisms of light-driven NP chain disruption, also proposes an alternative method for tuning the size of Au NPs.