37 research outputs found
Green nanoparticle synthesis at scale : a perspective on overcoming the limits of pulsed laser ablation in liquids for high-throughput production
Nanoparticles have become increasingly important for a variety of applications, including medical diagnosis and treatment, energy harvesting and storage, catalysis, and additive manufacturing. The development of nanoparticles with different compositions, sizes, and surface properties is essential to optimize their performance for specific applications. Pulsed laser ablation in liquid is a green chemistry approach that allows for the production of ligand-free nanoparticles with diverse shapes and phases. Despite these numerous advantages, the current production rate of this method remains limited, with typical rates in the milligram per hour range. To unlock the full potential of this technique for various applications, researchers have dedicated efforts to scaling up production rates to the gram-per-hour range. Achieving this goal necessitates a thorough understanding of the factors that limit pulsed laser ablation in liquid (PLAL) productivity, including laser, target, liquid, chamber, and scanner parameters. This perspective article explores these factors and provides a roadmap for increasing PLAL productivity that can be adapted to specific applications. By carefully controlling these parameters and developing new strategies for scaling up production, researchers can unlock the full potential of pulsed laser ablation in liquids
Second harmonic generation as a probe of broken mirror symmetry
The notion of spontaneous symmetry breaking has been used to describe phase
transitions in a variety of physical systems. In crystalline solids, the
breaking of certain symmetries, such as mirror symmetry, is difficult to detect
unambiguously. Using 1-TaS, we demonstrate here that
rotational-anisotropy second harmonic generation (RA-SHG) is not only a
sensitive technique for the detection of broken mirror symmetry, but also that
it can differentiate between mirror symmetry-broken structures of opposite
planar chirality. We also show that our analysis is applicable to a wide class
of different materials with mirror symmetry-breaking transitions. Lastly, we
find evidence for bulk mirror symmetry-breaking in the incommensurate charge
density wave phase of 1-TaS. Our results pave the way for RA-SHG to
probe candidate materials where broken mirror symmetry may play a pivotal role.Comment: 13 pages, 10 figures. Edited (v2) to include Bilal G\"okce in the
authors list who was mistakenly excluded. Edited again (v3) to incorporate
modifications recommended by referees. Replaced (v4) with version published
in Physical Review
Nanoparticles alloying in liquids: Laser-ablation-generated Ag or Pd nanoparticles and laser irradiation-induced AgPd nanoparticle alloying
International audienceLaser irradiation of a mixture of single element micro/nanomaterials may lead to their alloying and fabrication of multielement structures. In addition to the laser induced alloying of particulates in the form of micro/nanopowders in ambient atmosphere which forms the basis of the field of additive manufacturing technology another interesting problem is the laser induced alloying of a mixture of single element nanoparticles in liquids since this process may lead to the direct fabrication of alloyed nanoparticles colloidal solutions. In this work Ag and Pd bare, surface ligand-free nanoparticles in solution were prepared by laser ablation of the corresponding bulk target materials separately in water, the two solutions were mixed and the mixed solution was laser irradiated for different time durations in order to investigate the laser induced nanoparticles alloying in liquid. Nanoparticles alloying and formation of AgPd alloyed nanoparticles takes place with the decrease of the intensity of the surface plasmon resonance peak of the Ag nanoparticles (at ~405 nm) with the irradiation time while the low wavelength interband absorption peaks of either Ag or Pd nanoparticles remain unaffected by the irradiation for times even as long as 30 mins. The alloyed nanoparticles have lattice constants with values between those of the pure metals which indicates that they consist of Ag and Pd in approximately 1:1 ratio similar to the atomic composition of the starting mixed nanoparticles solution. Formation of nanoparticle networks consisting of bimetallic alloyed nanoparticles and nanoparticles which remain as single elements even after the end of the irradiation, joining together, are also formed. The binding energies of the 3d core electrons of both Ag and Pd nanoparticles shift to lower energies with the irradiation time also a typical characteristic of AgPd alloyed nanoparticles
Time and mechanism of nanoparticle functionalization by macromolecular ligands during pulsed laser ablation in liquids
Laser
ablation of gold in liquids with nanosecond laser pulses
in aqueous solutions of inorganic electrolytes and macromolecular
ligands for gold nanoparticle size quenching is probed inside the
laser-induced cavitation bubble by in situ X-ray
multicontrast imaging with a Hartmann mask (XHI). It is found that
(i) the in situ size quenching power of sodium chloride
(NaCl) in comparison to the ablation in pure water can be observed
by the scattering contrast from XHI already inside the cavitation
bubble, while (ii) for polyvinylpyrrolidone (PVP) as a macromolecular
model ligand an in situ size quenching cannot be
observed. Complementary ex situ characterization
confirms the overall size quenching ability of both additive types
NaCl and PVP. The macromolecular ligand as well as its monomer N-vinylpyrrolidone
(NVP) are mainly effective for growth quenching of larger nanoparticles
on later time scales, leading to the conclusion of an alternative
interaction mechanism with ablated nanoparticles compared to the electrolyte
NaCl, probably outside of the cavitation bubble, in the surrounding
liquid phase. While monomer and polymer have similar effects on the
particle properties, with the polymer being slightly more efficient,
only the polymer is effective against hydrodynamic aggregation
How Nanoparticle Size and Bubble Merging is Governed by Short-Range Spatially-Controlled Double-Beam Laser Ablation in Liquids
Pulsed laser ablation in liquid (LAL) is a method for synthesizing nanoparticles with controlled composition and high purity. However, current research predominantly examines isolated cavitation bubbles, overlooking real-world LAL scenarios where numerous bubbles interact simultaneously. This study addresses this gap by investigating the effects of short-range micrometric spatially controlled double-pulse laser ablation in liquids on nanoparticle size distribution. Gold and YAG are used as model materials, and a dimensionless parameter, H*, is introduced to quantify the ratio between double bubble spatial separation and their maximum height. This parameter correlates with cavitation bubble merging time, bubble volume change rate, and subsequent nanoparticle size increase. Shadowgraphs provide valuable insights into bubble contact and fusion dynamics, showcasing phase separation by a thin water film and subsequent merging into a single bubble. Notably, a two-fold increase in nanoparticle size is observed for both Au and YAG at H* = 0.25. Our research indicates a strong association between nanoparticle size trends and cavitation bubble volume rate change, particularly emphasized at H* = 0.25. Understanding the dynamics of neighboring bubbles during LAL emphasizes the relevance of lateral pulse distances in dual-beam LAL, impacting particle size distribution in a distance-dependent manner
Manipulation of the Size and Phase Composition of Yttrium Iron Garnet Nanoparticles by Pulsed Laser Post-Processing in Liquid
Modification of the size and phase composition of magnetic oxide nanomaterials dispersed in liquids by laser synthesis and processing of colloids has high implications for applications in biomedicine, catalysis and for nanoparticle-polymer composites. Controlling these properties for ternary oxides, however, is challenging with typical additives like salts and ligands and can lead to unwanted byproducts and various phases. In our study, we demonstrate how additive-free pulsed laser post-processing (LPP) of colloidal yttrium iron oxide nanoparticles using high repetition rates and power at 355 nm laser wavelength can be used for phase transformation and phase purification of the garnet structure by variation of the laser fluence as well as the applied energy dose. Furthermore, LPP allows particle size modification between 5 nm (ps laser) and 20 nm (ns laser) and significant increase of the monodispersity. Resulting colloidal nanoparticles are investigated regarding their size, structure and temperature-dependent magnetic properties