Double-pulse laser ablation in liquids: nanoparticle bimodality reduction by sub-nanosecond interpulse delay optimization

Applications of nanoparticles (NPs) in medicine, energy, catalysis, or additive manufacturing demand the development of NP production methods that are offering material and solvent versatility, high purity, morphology, and size control, together with industrial-scale production capabilities. Pulsed laser ablation in liquids (PLAL) is a technique that comes close to meeting these demands; however, NP size control remains a challenge. To reduce the characteristic bimodality in NPs synthesized by high-intensity PLAL, a double pulse configuration with inter-pulse delays between 300 ps and 1200 ps is proposed. In this temporal delay window, the plume and initial bubble are still flat so that shielding of the second laser pulse by the cavitation bubble is avoided; minimizing pulse shielding that could reduce NP productivity. At a pulse delay of 600 ps, a (9 +/- 1) wt% reduction of the large NP fraction is demonstrated (at the expense of mass yield), showing the possibility of modifying the NP size distribution produced in PLAL by temporal pulse shaping.