Comparative Analysis Based on Near-Field Electromagnetic Theory Combined with Molecular Dynamics for Pulse Light-Induced Plasmonic Nanobubble in Gold and Silver Nanofluids

Noble metallic nanofluids can generate plasmonic nanobubbles (PNB) under short pulse light irradiation. Research of the PNB nucleation energy density threshold (EDT) and its growth kinetics will provide theoretical insights for emerging applications such as optofluidic control and cell-targeted drug delivery. Using a computational model of near-field electromagnetic theory combined with molecular dynamics (MD) simulation, this study compares the EDTs and nucleation times of PNBs around gold and silver nanoparticles (NPs) with different sizes irradiated with 5 and 100 ps pulse lights. Furthermore, it reveals the energy transfer mechanism of the PNB formation and growth by analyzing the temperature evolution of the water layer near the gold and silver NPs. The results show that with the same pulse light duration time and NP size, it is easier for silver NP to generate PNB than gold NP. In addition, PNBs are more likely to form around NPs with larger sizes. However, the impact of the pulse light duration time on PNB formation is more significant than that of the NP material and size. Notably, 6 nm silver NP has a 73% lower EDT with 5 ps pulse light irradiation than 100 ps; furthermore, the nucleation time of PNB is advanced by 77%. The temperature results reveal that the water layer near the silver NPs obtains a higher temperature than that near the gold NPs with 5 ps pulsed light irradiation. The observation indicates that the resonant electric field (REF), induced by a short pulse of light on the gold and silver NP surface, significantly enhances the motion of water molecules. However, under 100 ps pulse light irradiation, the temperatures of gold and silver NPs exceed those of the adjacent water layers. This phenomenon indicates that the thermal diffusion process is significantly slower than the strong effect of the REF on the motion of the water molecules. These results will provide an essential theoretical basis for accurate manipulation of the light and NP parameters to control the formation of PNB.