Showing papers by "Stephan Barcikowski published in 2023"
TL;DR: In this paper , the authors used a series of C6 solvents complemented by n-pentane and n-heptane during the nanosecond laser ablation of gold, focusing on the solventdependent influence on gas formation rates, nanoparticle productivity, and gas composition.
Abstract: Laser ablation in liquids has been established as a scalable preparation method of nanoparticles for various applications. Particularly for materials prone to oxidation, it is established to suppress oxidation by using organic solvents as a liquid medium. While this often functionalizes the nanoparticles with a carbon shell, the related chemical processes that result from laserinduced decomposition reactions of the organic solvents remain uncertain. Using a systematic series of C6 solvents complemented by n-pentane and n-heptane during the nanosecond laser ablation of gold, the present study focuses on the solvent-dependent influence on gas formation rates, nanoparticle productivity, and gas composition. Both the permanent gas and hydrogen formation was found to be linearly correlated with ablation rate, ΔHvap, and pyrolysis activation energy. Based on this, a decomposition pathway linked to pyrolysis is proposed allowing the deduction of first selection rules for solvents that influence the formation of carbon or permanent gases.
1 citations
TL;DR: In this article , a single-pulse, multiparticle fragmentation is performed in a continuously operated liquid jet, where 2-nm-sized nanoclusters (NCs) accompanied by larger fragments with sizes ranging between several ten nm and several µm are generated.
Abstract: Pulsed laser fragmentation of microparticles (MPs) in liquid is a synthesis method for producing high-purity nanoparticles (NPs) from virtually any material. Compared with laser ablation in liquids (LAL), the use of MPs enables a fully continuous, single-step synthesis of colloidal NPs. Although having been employed in several studies, neither the fragmentation mechanism nor the efficiency or scalability have been described. Starting from time-resolved investigations of the single-pulse fragmentation of single IrO2 MPs in water, the contribution of stress-mediated processes to the fragmentation mechanism is highlighted. Single-pulse, multiparticle fragmentation is then performed in a continuously operated liquid jet. Here, 2 nm-sized nanoclusters (NCs) accompanied by larger fragments with sizes ranging between several ten nm and several µm are generated. For the nanosized product, an unprecedented efficiency of up to 18 µg J-1 is reached, which exceeds comparable values reported for high-power LAL by one order of magnitude. The generated NCs exhibit high catalytic activity and stability in oxygen evolution reactions while simultaneously expressing a redox-sensitive fluorescence, thus rendering them promising candidates in electrocatalytic sensing. The provided insights will pave the way for laser fragmentation of MPs to become a versatile, scalable yet simple technique for nanomaterial design and development.
1 citations
TL;DR: In this paper , a series of TiO-2 (rutile and P25) with increasing oxygen deficiency and Ti3+ concentration by pulsed laser defect engineering in liquid (PUDEL), and selectively quantify the acidic and basic surface hydroxyls by fluoride substitution.
Abstract: Both oxygen vacancies and surface hydroxyls play a crucial role in catalysis. Yet, their relationship is not often explored. Herein, we prepare two series of TiO-2 (rutile and P25) with increasing oxygen deficiency and Ti3+ concentration by pulsed laser defect engineering in liquid (PUDEL), and selectively quantify the acidic and basic surface OH by fluoride substitution. As indicated by EPR spectroscopy, the laser-generated Ti3+ exist near the surface of rutile, but appear to be deeper in the bulk for P25. Fluoride substitution shows that extra acidic bridging OH are selectively created on rutile, while the surface OH density remains constant for P25. These observations suggest near-surface Ti3+ are highly related to surface bridging OH, presumably the former increasing the electron density of the bridging oxygen to form more of the latter. We anticipate that fluoride substitution will enable better characterization of surface OH and its correlation with defects in metal oxides.
1 citations
TL;DR: In this article , the authors synthesized nanofluids composed of ligand-free colloidal CuNPs dispersed in ethylene glycol by continuous flow, picosecond-pulsed laser ablation in liquids synthesis, yielding monomodal-CuNPs with mean diameters of 2.5 and 4.8 nm.
26 Jun 2023
TL;DR: In this paper , the authors present an extension of mesoscale particle-based modeling of electrophoretic deposition (EPD), which has relied exclusively on pairwise interparticle interactions described by Derjaguin-Landau-Verwey-Overbeek theory.
Abstract: This work represents an extension of mesoscale particle-based modeling of electrophoretic deposition (EPD), which has relied exclusively on pairwise interparticle interactions described by Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. With this standard treatment, particles continuously move and interact via excluded volume and electrostatic pair potentials under the influence of external fields throughout the EPD process. The physics imposed by DLVO theory may not be appropriate to describe all systems, considering the vast material, operational, and application space available to EPD. As such, we present three modifications to standard particle-based models, each rooted in the ability to dynamically change interparticle interactions as simulated deposition progresses. This approach allows simulations to capture charge transfer and/or irreversible adsorption based on tunable parameters. We evaluate and compare simulated deposits formed under new physical assumptions, demonstrating the range of systems that these adaptive physics models may capture.
TL;DR: In this article , a double pulse configuration with inter-pulse delays between 300 ps and 1200 ps is proposed to reduce the characteristic bimodality in NPs synthesized by high-intensity PLAL, showing the possibility of modifying the NP size distribution produced in PLAL by temporal pulse shaping.
Abstract: 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.
TL;DR: In this article , the authors show that pulsed laser doping is a promising technique to dope multiple ions in nBGs without negatively impacting their structure or size, and that laser doping of FeSr into NBGs can improve the angiogenic properties of nBs.
Abstract: We show that pulsed laser doping is a promising technique to dope multiple ions in nBGs without negatively impacting their structure or size and that laser doping of FeSr into nBGs can improve the angiogenic properties of nBGs.
TL;DR: In this paper , ligand-free AuNPs were fabricated by laser ablation in liquids and laser fragmentation in liquids (LFL) and irradiated with clinically relevant proton fields using water phantoms.
Abstract: Gold nanoparticles (AuNPs) are known radiosensitizers in proton therapy (PT) applicable for the treatment of solid tumors, where they amplify production of reactive oxygen species (ROS). However, it is underexplored how this amplification is correlated with the AuNPs´ surface chemistry. To clarify this issue, we fabricated ligand-free AuNPs of different mean diameters by laser ablation in liquids (LAL) and laser fragmentation in liquids (LFL) and irradiated them with clinically relevant proton fields using water phantoms. ROS generation was monitored by the fluorescent dye 7-OH-coumarin. Our findings reveal an enhancement of ROS production driven by I) increased total particle surface area, II) utilization of ligand-free AuNPs avoiding sodium citrate as a radical quencher ligands, and III) a higher density of structural defects generated by LFL synthesis, indicated by surface charge density. Based on these findings it may be concluded that the surface chemistry is a major and underexplored contributor to ROS generation and sensitizing effects of AuNPs in PT. We further highlight the applicability of AuNPs in vitro in human medulloblastoma cells.
TL;DR: Barcikowski et al. as discussed by the authors track microparticle laser fragmentation processes all along the timescale from picoseconds to milliseconds and discover the unprecedented efficiency to yield ultrasmall particles, exceeding current laser synthesis productivities by one order of magnitude.
Abstract: Active and Redox-Sensitive Colloidal Nanoclusters In article number 2206485, Stephan Barcikowski, Heinz Paul Huber, and co-workers track microparticle laser fragmentation processes all along the timescale from picoseconds to milliseconds. They discover the unprecedented efficiency to yield ultrasmall particles, exceeding current laser synthesis’ productivities by one order of magnitude. (Cover art shows AI-painted “Advanced Nanoparticle Generation and Excitation by Lasers in Liquids”, created by J. Barcikowski, F. Barcikowski, and S. Barcikowski using DiscoArt-DiscoDiffusion.)
TL;DR: In this paper , 45 binary alloys made of platinum and a selected 1st and 2nd-row transition metal, platinum group element, or coin metal were synthesized via a scalable laser synthesis method.
Abstract: Commercial diesel oxidation catalysis mainly uses monometallic and bimetallic Pt-Pd-based catalysts, but alloying with different elements has rarely been done systematically under industrial testing conditions. 45 binary alloys made of platinum and a selected 1st and 2nd-row transition metal, platinum group element, or coin metal were synthesized via a scalable laser synthesis method. Then, catalytic performance and durability were evaluated for one diesel oxidation and two ammonia-slip environments. The results show the highest activity when the adsorption enthalpy of molecular oxygen of the alloy was similar to the value of Pt. Furthermore, the durability of the alloy catalysts was found to increase with the melting point of the 2nd element Pt was alloyed with, even at molar fractions. Our results further indicate beneficial synergies beyond the binary systems underlining the possibility of further improvements by considering ternary or multinary alloys, which are accessible via laser synthesis.