Synthesis and Shape Manipulation of Anisotropic Gold Nanoparticles by Laser Ablation in Solution

Anisotropic gold nanostructures are attracting attention due to the strong correlation between their shape and the localized surface plasmon resonances, which allows tuning their optical responses through morphological optimizations. Laser ablation synthesis in solution usually produces stable gold nanospheres colloids without any surfactant, which is important for their easy functionalization. Nevertheless, obtaining anisotropic nanoparticles with this technique is still a challenge, and few examples show that a postsynthesis approach is usually required. We show that a single pulse laser ablation allows the synthesis of anisotropic branched gold nanoparticles through careful control of the number of laser pulses interacting with the generated nanoparticles. It is shown that the very first pulses considerably affect the morphology of the ablated nanomaterial. Moreover, also the fluence above the ablated target is found to have an important role in the final nanoparticle morphology. The study of the interaction between the nanostructures and the laser pulses is achieved using an inflow setup. The optical extinction behavior of the produced anisotropic gold nanostructures was rationalized using boundary element method (BEM) based calculations, by considering the contributions from several morphologies, which were found to be in good agreement with experimental observations.