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21LM-O-6
Ultrafast time-resolved experiments reveal the influence of a liquid confinement layer on the laser ablation dynamics of gold
Maximilian Spellauge1'2, Carlos Donate-Buendfa2'3, Stephan Barcikowski2, Bilal Gökce2'3, Heinz
P. Huber1
1- Department of Applied Sciences and Mechatronics, Munich University of Applied Sciences, 80335
Munich, Germany
2- Technical Chemistry I and Center for Nanointegration Duisburg-Essen (CENIDE), University of
Duisburg-Essen, 45141 Essen, Germany
3- Materials Science and Additive Manufacturing, School of Mechanical Engineering and Safety Engineering, University of Wuppertal, 42119 Wuppertal, Germany
Main author email address: maximilian.spellauge@hm. edu
Laser ablation in liquid (LAL) is a versatile, environmentally friendly and scalable method to generate surfactant-free nanoparticles [1]. Compared to laser ablation in gaseous environments, the liquid layer present in LAL adds a layer of complexity as it represents an additional channel of energy loss, serves as a highly reactive environment, and confines the ablation products [2]. So far, experimental investigation of the ablation dynamics governing LAL has been mainly performed on timescales ranging from nanoseconds (ns) to microseconds (^s). However, investigation of the sub-ns dynamics would significantly enhance the understanding of the LAL process, as the conditions under which nanoparticles are generated are established at this timescale [2], [3]. Furthermore, a detailed experimental analysis of the sub-ns LAL dynamics would allow experimental testing of recent computational predictions [4].
In order to investigate the influence of a water confinement layer on the ablation dynamics, ultrafast time-resolved experiments were performed on gold targets immersed in air and water. A pump-probe microscope (PPM) setup was used to analyze the transient reflectivity dynamics of the LAL process on timescales ranging from picoseconds to microseconds. Double-pulse ablation experiments with inter-pulse spacing ranging from 0 ps to 1 ns complemented the PPM measurements and allowed for the investigation of the ablation plume composition.
The detailed experimental investigation highlights the water confinement layers influence on the laser ablation process on the entire investigated timescale. This ranges from electron injection and the generation of a highly absorbing plasma within 1 ps after pulse impact to cavitation bubble development at approximately 1 ns. Furthermore, confinement of the ablation products and formation of primary particles is observed on timescales ranging from 20 ps to 200 ps and 200 ps to 1 ns, respectively.
The results enhance the understanding of the LAL process, confirm computational predictions and create the opportunity to further optimize the nanoparticle production in terms of size distribution and production-rate.
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[3] A. Kanitz, D. J. Förster, J. S. Hoppius, R. Weber, A. Ostendorf, and E. L. Gurevich, "Pump-probe microscopy of femtosecond laser ablation in air and liquids," Appl. Surf. Sci., vol. 475, no. September 2018, pp. 204-210, May 2019.
[4] C.-Y. Shih, M. V. Shugaev, C. Wu, and L. V. Zhigilei, "Generation of Subsurface Voids, Incubation Effect, and Formation of Nanoparticles in Short Pulse Laser Interactions with Bulk Metal Targets in Liquid: Molecular Dynamics Study," J. Phys. Chem. C, vol. 121, no. 30, pp. 16549-16567, Aug. 2017.
