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Optical control of layered nanomaterial generation by pulsed-laser ablation in liquids
摘要： Pulsed-laser ablation in liquids capitalizes on combining chemical and optical control to rapidly generate size, composition, and phase-controlled nanostructures, without the need for surfactants. Very high temperatures, which we determined to be ca. (8,400 ± 1,300) K, pressures, and ion densities exist in the laser-induced liquid-confined plasma. These unique conditions, coupled with the rapid cooling during which nanoparticles are formed, permitted access to new extreme regions of materials’ phase diagrams. This way, we produced metastable layered copper and zinc hydroxide-based nanocrystals with interesting physical properties that can serve as precursors for two-dimensional inorganic semiconductor nanomaterials.
关键词： LTE spectra,optical control,electron temperature,layered nanocrystals,Pulsed-laser ablation in liquids,laser-induced plasma
更新于2025-09-23 15:19:57
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Study of the physicochemical surface alterations and incubation phenomena induced on iron targets by nanosecond pulsed laser ablation in liquids: Effect on productivity and characteristics of the synthesized nanoscale zero-valent iron (nZVI) particles
摘要： This work presents a systematic study of the significant role of the surface physicochemical alterations produced during the laser ablation of massive iron disks submerged in different solvents on the generation of colloidal iron nanoparticles. For that purpose, the laser ablation thresholds and the incubation coefficients for various pulse numbers per site and pulse energies have been measured under distilled water (DW) and ethanol (EtOH). After that, a complete physicochemical characterization of these targets indicated higher threshold fluence values for the ablation experiments conducted in EtOH than those performed in DW. The threshold fluence values decreased also with the decrease of the pulse overlap for both solvents, being it much more pronounced in EtOH. In addition, the related incubation coefficient showed that the incubation effect is lower for experiments conducted in DW. The characteristics of the synthesized nZVI particles were also a function of the solvent nature and the pulse overlap: laser ablation in DW leaded to iron oxide nanoparticles, whereas core-shell iron nanoparticles were obtained in EtOH. Moreover, high pulse overlap values lead to chemical alterations, resulting in a decrease of the composition homogeneity and a strong increase of the nanoparticle polydispersity.
关键词： Incubation effect,Nanosecond pulsed laser ablation in liquids,Raman spectroscopy,Colloidal nanoscale zero-valent iron particles,Laser ablation threshold,Laser induced-chemical surface alteration
更新于2025-09-19 17:13:59
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Effect of liquid environment on single-pulse generation of laser induced periodic surface structures and nanoparticles
摘要： The effect of a liquid environment on the fundamental mechanisms of surface nanostructuring and generation of nanoparticles by single pulse laser ablation is investigated in a closely integrated computational and experimental study. A large-scale molecular dynamics simulation of spatially-modulated ablation of Cr in water reveals a complex picture of dynamic interaction between the ablation plume and water, which involves rapid deceleration of the ablation plume by water environment, formation and prompt disintegration of a hot metal layer at the interface between the ablation plume and water, lateral redistribution and redeposition of a major fraction of the ablation plume, and eventual formation of smooth frozen surface features. A good agreement between the shapes of the surface features predicted in the simulation and the ones generated in single pulse laser ablation experiments performed for Cr in water supports the mechanistic insights revealed in the simulations. The results of this study suggest that the presence of liquid environment can eliminate the sharp features of surface morphology, reduce the amount of material removed from the target by more than an order of magnitude, and narrow down the nanoparticle size distribution as compared to laser ablation in vacuum. Moreover, the computational predictions of the effective incorporation of molecules constituting the liquid environment into the surface region of the irradiated target and the generation of high vacancy concentrations exceeding the equilibrium levels by more than an order of magnitude suggest a potential for hyperdoping of laser-generated surfaces by solutes present in the liquid environment.
关键词： Laser-Induced Periodic Surface Structures (LIPSS),Generation of Nanoparticles,Crystal Defects,Surface Morphology,Hyperdoping,Molecular Dynamics Simulations,Pulsed Laser Ablation in Liquids
更新于2025-09-19 17:13:59
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The effect of pulse duration on nanoparticle generation in pulsed laser ablation in liquids: Insights from large-scale atomistic simulations
摘要： The generation of colloidal solutions of chemically clean nanoparticles through pulsed laser ablation in liquids (PLAL) has evolved into a thriving research field that impacts industrial applications. The complexity and multiscale nature of PLAL make it difficult to untangle the various processes involved in the generation of nanoparticles and establish the dependence of nanoparticle yield and size distribution on the irradiation parameters. Large-scale atomistic simulations have yielded important insights into the fundamental mechanisms of ultrashort (femtoseconds to tens of picoseconds) PLAL and provided a plausible explanation of the origin of the experimentally observed bimodal nanoparticle size distributions. In this paper, we extend the atomistic simulations to short (hundreds of picoseconds to nanoseconds) laser pulses and focus our attention on the effect of the pulse duration on the mechanisms responsible for the generation of nanoparticles at the initial dynamic stage of laser ablation. Three distinct nanoparticle generation mechanisms operating at different stages of the ablation process and in different parts of the emerging cavitation bubble are identified in the simulations. These mechanisms are (1) the formation of a thin transient metal layer at the interface between the ablation plume and water environment followed by its decomposition into large molten nanoparticles, (2) nucleation, growth, and rapid cooling/solidification of small nanoparticles at the very front of the emerging cavitation bubble, above the transient interfacial metal layer, and (3) spinodal decomposition of a part of the ablation plume located below the transient interfacial layer, leading to the formation of a large population of nanoparticles growing in a high-temperature environment through inter-particle collisions and coalescence. The coexistence of the three distinct mechanisms of the nanoparticle formation at the initial stage of the ablation process can be related to the broad nanoparticle size distributions commonly observed in nanosecond PLAL experiments. The strong dependence of the nanoparticle cooling and solidification rates on the location within the low-density metal-water mixing region has important implications for the long-term evolution of the nanoparticle size distribution, as well as for the ability to quench the nanoparticle growth or dope them by adding surface-active agents or doping elements to the liquid environment.
关键词： phase explosion,pulsed laser ablation in liquids,molecular dynamics simulations,hydrodynamic instability,atomistic simulations,nanoparticles,nucleation and growth
更新于2025-09-19 17:13:59
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Investigating double pulse nanoparticle enhanced laser induced breakdown spectroscopy
摘要： Several strategies have been e?ectively tested in the past to improve the Laser Induced Breakdown Spectroscopy (LIBS) signal, involving peculiar experimental con?gurations, such as Double Pulse LIBS (DP-LIBS). Recently, sample treatment has proven to be a viable and simple way to enhance the LIBS performances; in particular, the Nanoparticle-Enhanced LIBS (NELIBS) methodology uses a deposition of metal nanoparticles (NPs) on the sample to greatly increase the emission of the LIBS plasma. In this work, we investigate the possibility of combining, for the ?rst time, DP-LIBS with NELIBS. The chosen set-up uses two parallel non-collinear laser pulses to ensure the activation of NPs during both pulses, while maintaining the low-pressure environment typical of DP-LIBS. The two laser beams are spatially separated so that the second beam is focused within the shock wave generated by the ?rst one. This con?guration allows the exploitation of the combined enhancement of both DP-LIBS and NELIBS. Several tests on copper targets have been performed to determine the best set-up for the maximum magnitude of the signal enhancement by adjusting di?erent parameters such as pulse energies and o?set distances. Commercially available silver NPs and NPs prepared by pulsed laser ablation in liquid have been tested and their performances compared with standard DP-LIBS.
关键词： Pulsed laser ablation in liquids,Double pulse LIBS,Nanoparticle enhanced LIBS,Spatially o?set DP-NELIBS,Signal enhancement
更新于2025-09-19 17:13:59
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Numerical Investigation of Ultrashort Laser-Ablative Synthesis of Metal Nanoparticles in Liquids Using the Atomistic-Continuum Model
摘要： We present a framework based on the atomistic continuum model, combining the Molecular Dynamics (MD) and Two Temperature Model (TTM) approaches, to characterize the growth of metal nanoparticles (NPs) under ultrashort laser ablation from a solid target in water ambient. The model is capable of addressing the kinetics of fast non-equilibrium laser-induced phase transition processes at atomic resolution, while in continuum it accounts for the effect of free carriers, playing a determinant role during short laser pulse interaction processes with metals. The results of our simulations clarify possible mechanisms, which can be responsible for the observed experimental data, including the presence of two populations of NPs, having a small (5–15 nm) and larger (tens of nm) mean size. The formed NPs are of importance for a variety of applications in energy, catalysis and healthcare.
关键词： metal nanoparticles,femtosecond laser ablation,dual nanoparticle distribution,pulsed laser ablation in liquids
更新于2025-09-16 10:30:52
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Laser-Ablative Synthesis of Isotope-Enriched Samarium Oxide Nanoparticles for Nuclear Nanomedicine
摘要： Nuclear nanomedicine is an emerging field, which utilizes nanoformulations of nuclear agents to increase their local concentration at targeted sites for a more effective nuclear therapy at a considerably reduced radiation dosage. This field needs the development of methods for controlled fabrication of nuclear agents carrying nanoparticles with low polydispersity and with high colloidal stability in aqueous dispersions. In this paper, we apply methods of femtosecond (fs) laser ablation in deionized water to fabricate stable aqueous dispersion of 152Sm-enriched samarium oxide nanoparticles (NPs), which can capture neutrons to become 153Sm beta-emitters for nuclear therapy. We show that direct ablation of a 152Sm-enriched samarium oxide target leads to widely size- and shape-dispersed populations of NPs with low colloidal stability. However, by applying a second fs laser fragmentation step to the dispersion of initially formed colloids, we achieve full homogenization of NPs size characteristics, while keeping the same composition. We also demonstrate the possibility for wide-range tuning of the mean size of Sm-based NPs by varying laser energy during the ablation or fragmentation step. The final product presents dispersed solutions of samarium oxide NPs with relatively narrow size distribution, having spherical shape, a controlled mean size between 7 and 70 nm and high colloidal stability. The formed NPs can also be of importance for catalytic and biomedical applications.
关键词： nuclear nanomedicine,samarium (Sm) oxide nanoparticles,pulsed laser ablation in liquids,femtosecond laser ablation and fragmentation
更新于2025-09-16 10:30:52
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Laser additive manufacturing of oxide dispersion strengthened steels using laser-generated nanoparticle-metal composite powders
摘要： A new route for the synthesis of powder composites suitable for processing with laser additive manufacturing is demonstrated. The powder composites, consisting of micrometer-sized stainless steel powder, homogenously decorated with nano-scaled Y2O3 powder particles, are manufactured by laser processing of colloids and electrostatic deposition. Consolidated by laser metal deposition and selective laser melting, the resulting specimens show superior mechanical properties at elevated temperatures, caused by the nano-sized, homogenously distributed dispersoids.
关键词： Laser additive manufacturing,Pulsed laser ablation in liquids,Selective Laser Melting,Oxide dispersion strengthened materials,ODS
更新于2025-09-12 10:27:22
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A new approach to coat PA12 powders with laser-generated nanoparticles for selective laser sintering
摘要： The modification of selective laser sintering (SLS) powder materials by nanoadditives offers the possibility to adapt the powder properties to the laser sintering process or the resulting part properties. To avoid agglomeration of the nanofiller, a new approach in which surfactant-free laser-generated colloidal nanoparticles are adsorbed onto the polymer surface directly in an aqueous solution is demonstrated. Based on this novel approach, polyamide 12 (PA12) powders are decorated with metal and oxide nanoparticles and processed via SLS. Electron microscopy and confocal laser scanning imaging are utilized to analyze the dispersion of the filler.
关键词： selective laser sintering,laser additive manufacturing,polymer powders,pulsed laser ablation in liquids,nanoparticles
更新于2025-09-12 10:27:22
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Effective size separation of laser-generated, surfactant-free nanoparticles by continuous centrifugation
摘要： High-power, nanosecond, pulsed-laser ablation in liquids enables the continuous synthesis of highly-pure colloidal nanoparticles (NPs) at an application-relevant scale. The gained mass-weighted particle size distribution is however often reported to be broad, requiring post treatment like centrifugation to remove undesired particle size fractions. To date, available centrifugation techniques are generally discontinuous, limiting the throughput and hindering economic upscaling. Hence, throughout this paper, a scalable, continuously operating centrifugation of laser-generated platinum nanoparticles in a tubular bowl centrifuge is reported for the first time. To that end, using a 121 W ns-laser, a continuous production of a colloidal suspension of NPs, yet with broad particle size distribution has been employed, yielding productivities of 1 - 2 g/h for gold, silver, and platinum. Subsequent downstream systematic study of relevant centrifugation parameters involved, effective size optimization and respective size sharpness parameters for a maximum Pt nanoparticle diameter of 10 nm are reported. The results of the experimental centrifugation of laser-generated Pt-NPs were in excellent agreement with the theoretically-calculated cut-off diameter. After centrifugation with optimized parameters, the polydispersity indices of the Pt-NPs size distributions were reduced by a factor of six and higher monodispersities were observed.
关键词： continuous process chain,tubular bowl centrifugation,contamination-free nanoparticle processing,Pt-NPs,pulsed laser ablation in liquids
更新于2025-09-12 10:27:22