Laser Ablation in Flowing Liquid

Pulsed laser ablation in liquid (PLAL) was used to synthesise indium oxide (In2O3) nanocolloidal suspension. Colloidal In2O3 nanoparticles (NPs) are synthesised by pulsed laser ablation of high-purity indium target in distilled water with various laser fluences at room temperature. UV–vis absorption and transmission electron microscopy were conducted to determine the bandgap, size, distribution and shape of the NPs. The optical properties, size and the morphology of the synthesised In2O3 were influenced strongly by laser fluence and wavelength. Laser ablation of indium in water produced spherical In2O3 NPs with an average size of 30 nm and their distribution was nearly Gaussian type.

Pulsed laser ablation of a Si substrate in cooled KOH solution and a water-confined region is investigated. The liquid temperature is varied from room temperature down to 4°C. For laser ablation in water, the material removal rate reduces slightly as liquid temperature increases. However, the material removal rate for laser ablation in KOH solution is twice as high as that in the water at a cooled liquid environment (temperature ∼10°C). This enhancement results from a strong chemical interaction between the KOH solution and Si materials around the ablated crater during fast cooling of the substrate surface from the vaporization temperature after the laser ablation. It is also found that the material removal rate is reduced greatly in the KOH solution as the liquid temperature increases. It is because at a liquid temperature above 20°C, the KOH solution starts to interact strongly with Si when the two materials are in contact. The formation of Si(OH)x chemical debris blocks the incident laser beam to reach the Si surface and reduces the laser ablation effect. This result of the investigation is applied to set up a cooled KOH flow system for wafer thinning to thin substrate thickness down to 50 μm.

Pulsed Laser Ablation in liquid (PLAL) is considered as a robust and simple technique for producing nanoparticles (NPs) using lasers. The carbon-based nanoparticles were fabricated via the PLAL approach by irradiating a graphite target with a pulsed Nd:YAG laser of wavelength 532 nm. The graphite target was immersed in distilled water and irradiated for 10 min. The pulse length, reputation rate, and fluence were 6 ns, 10 Hz, and 0.4 J cm−2, respectively. The structural and physical properties of the synthesized NPs were investigated and analyzed using different characterization methods. For example, Transmission Electron Microscopy (TEM) images revealed diverse carbon nanostructures such as graphene nanosheets, nanospheres, nanospheres in the shape of a necklace, and nanotubes. The spectrum of Energy Dispersive X-Ray spectroscopy (EDX) confirmed successful synthesis of high purity carbon nanostructures. Moreover, the result of X-Ray Diffraction (XRD) Spectroscopy indicated the presence of reduced Graphene Oxide (rGO) with a (002) plane and the absence of Graphene Oxide (GO). The transmission spectrum from Ultraviolet-Visible (UV–vis) analysis showed a strong trough at 266 nm which is attributed to the presence of carbon nanostructures. Furthermore, Fourier-Transform Infrared Spectroscopy (FTIR) analysis demonstrated the vibration bonds related to carbon. The nanostructures produced were semi-stable with little agglomeration as was inferred from the results of the Zeta Potential. Finally, the Dynamic Light Scattering (DLS) analysis supported the TEM results. PLAL technique is proved to be a simple method for producing carbon-based nanomaterials. Moreover, the laser fluence was found to be an important factor which affects greatly the type of nanostructures that could be synthesized during laser ablation.

In this paper, we propose a simple two-step method for the synthesis of Ag, Au, and Pt-doped ZnO nanoparticles. The method is based on the fabrication of targets using the pulsed laser deposition (PLD) technique where thin layers of metals (Ag, Pt, Au) have been deposited on a metal-oxide bulk substrate (ZnO). Such formed structures were used as a target for the production of doped nanoparticles (ZnO: Ag, ZnO: Au, and ZnO: Pt) by laser ablation in water. The influence of Ag, Au, and Pt doping on the optical properties, structure and composition, sizing, and morphology was studied using UV-Visible (UV-Vis) and photoluminescence (PL) spectroscopies, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), respectively. The band-gap energy decreased to 3.06, 3.08, and 3.15 for silver, gold, and platinum-doped ZnO compared to the pure ZnO (3.2 eV). PL spectra showed a decrease in the recombination rate of the electrons and holes in the case of doped ZnO. SEM, TEM, and AFM images showed spherical-shaped nanoparticles with a relatively smooth surface. The XRD patterns confirm that Ag, Au, and Pt were well incorporated inside the ZnO lattice and maintained a hexagonal wurtzite structure. This work could provide a new way for synthesizing various doped materials.

Boron nanoparticles (BNPs) are attractive nanomaterials for their employment in many applications, such as neutron detection, boron neutron capture therapy, proton boron capture therapy and nuclear fusion. Depending on the specific application, 10B or 11B isotopes can be used.Nevertheless, there are significant challenges in developing suitable BNPs using both conventional chemical synthesis routes and dry fabrication techniques. In this study we report BNPs directly synthetised in water by pulsed Laser Ablation in Liquid (PLAL). Nanoparticles of elemental boron have been generated by laser ablation of a sintered 10B target in MilliQ water by employing ns laser pulse. The ablation resulted in BNPs and boron target micro-fragments with hydrogen gas and boric acid as by-products. Simple washing steps were used to obtain clean BNPs in water. The BNPs showed a narrow size distribution between 3 and 4 nm and their stability in water was induced by a thin layer of boron oxide surrounds BNPs. The BNPs were fully characterized by the chemical and structural point of view employing several techniques. A discussion on boron chemical reactions during laser ablation in water and after the NPs were released in solution was done.

Superconducting thin films of Y1Ba2Cu3 O7 −x have been deposited on (100) Y-ZrO2 substrates by pulsed excimer laser ablation from anunreacted mixture of Y2O3, BaCO3 and CuO. The films deposited at substrate temperature of 680°C and oxygen partial pressure of 200 mtorr were found to be superconducting with zero resistive transition temperature of 89 K and critical current density of over 3 × 105 A/cm2 at 77 K. These results are compared with those obtained by laser ablation from a sintered superconducting pellet.

We report the fabrication of permalloy nanoparticles by pulsed excimer laser ablation of a permalloy (Fe19Ni81) target in sodium dodecyl sulfate aqueous solution and the subsequent laser-induced assembly, sintering, and fragmentation of the nanoparticles. Specifically, permalloy nanoparticles with diameters of 400−600 nm were observed to assemble into fullerene-like hollow microparticles. Laser irradiation caused sintering of the assembled particles, which showed Wulff construction and ledge growth behavior and finally resulted in smooth shells. Laser−particle interactions also caused fragmentation of the micro/nanoparticles. When the particle concentration is high, laser fragmentation rather than laser ablation dominates due to enhanced light absorption and scattering. The experiments reveal the dynamic process of the nano- and microparticle formation, demonstrating the rich processing environment of laser ablation in liquid.

In this paper, we prepared ZnO nano-particles by using pulsed laser ablation in water. ZnO particles are dispersed in pure water as a target material of laser ablation. We irradiated the ZnO particles in water with YAG laser with different wavelengths to investigate the effects of photon energy on the nano-particle formation. We measured both atomic composition of ZnO and crystallinity of the fabricated nano-particles by EDX and XRD. We also observed ZnO nano-particles by TEM. The averaged diameter of ZnO nano-particles was 6 nm.

Liquid‐phase pulsed laser ablation (LP‐PLA) is a promising technique for the fabrication of various nanomaterials because this technique is very simple and it is easy to control the experimental parameters. This paper demonstrates the synthesis of phase‐controlled iron oxide magnetic nanoparticles by laser ablation of a bulk α‐Fe2O3 target in the following liquid media: ethanol, D.I. water and acetone. Absorption spectra of the nanocolloidal solutions are measured by UV–Vis spectrophotometer. As‐synthesized nanoparticles, extracted from the colloidal solutions, are characterized by X‐ray diffraction (XRD), Raman spectroscopy, transmission electron microscope (TEM) equipped with X‐ray energy dispersive spectrometry (EDX) and a vibrating sample magnetometer (VSM) to discover crystallinity, phase structure, morphology, elemental compositions and magnetic properties in detail. The experimental results showed that the type of target and the magnitude of laser power play important roles in controlling the uniformity of iron oxide phase in the final product nanoparticles. Laser ablation of the iron oxide target in ethanol and acetone yields crystalline maghemite (γ‐Fe2O3) nanoparticles, while that in D.I. water yields amorphous hematite (α‐Fe2O3). Use of an iron oxide (α‐Fe2O3) target for PLA in all three solvents is able to prevent the formation of metal iron and wustite phases in the final product nanoparticles. Moreover, our nanoparticles obtained in all three solvents possess magnetic behaviour, particularly that obtained in acetone, which has better saturation magnetization than those in ethanol and D.I. water.

Ag@Au core–shell nanoparticles synthesized by pulsed laser ablation in water: Effect of plasmon coupling and their SERS performance

In-situ temperature and thickness control grown 2D-MoS2 via pulsed laser ablation for photovoltaic devices

Magnetite (Fe3O4) nanoparticles of 1–10 nm (with the maximum at 2 nm) were obtained via pulsed laser ablation of iron target in water in form of a stable dispersion without addition of surfactants and stabilizers. The structure of the material obtained was investigated using transmission electron microscopy, scanning electron microscopy, and Brunauer–Emmett–Teller methods. To investigate the composition of the particles in the sample, such methods as Fourier transform infrared spectroscopy, Raman spectroscopy, differential scanning calorimetry, and X-ray diffraction, were applied. Magnetite phase was found to be sufficiently pure, it was not contaminated by other iron oxide phases and contained not more than 0.5% of metallic iron in form of large particles. The study of the magnetic properties of the magnetite nanoparticles obtained has shown that they exhibit ferrimagnetic behavior at room temperature with the paramagnetic contribution explained by the presence of fine superparamagnetic particles.

Laser ablation for material processing

We report the preparation of silicon nanocrystals with efficient ultraviolet luminescence by nanosecond pulsed laser ablation in de-ionized water at a high laser fluence condition. Atomic force microscopy results show that nano-grains form in the process of laser ablation. Fourier transform infrared spectroscopy analyses indicate that silicon nanocrystals are formed and partially oxidized during synthesis. The photoluminescence measurement and the ultraviolet-visible transmittance spectroscopy of the samples prepared at various fluences reveal that all the prepared samples present an efficient ultraviolet emission at room temperature and it can be attributed to the quantum confinement effect and surface defect states. The emission wavelength of silicon nanocrystals is far shorter than visible light, which means potential applications in optoelectronic devices.

Highly N-doped (mid-1019 to ≳1020 cm−3) ZnTe/(001)GaAs epitaxial films have been grown by pulsed laser ablation (PLA) of a stoichiometric ZnTe target in a high-purity N2 ambient (50 to 200 mTorr) without the use of any assisting dc or ac plasma source. Unlike recent experiments in which atomic N, extracted from dc and rf plasma sources, was used to produce N-doping during molecular beam epitaxy, spectroscopic measurements performed during PLA of ZnTe in N2 do not reveal the presence of atomic N. This suggests that the high hole concentrations in laser ablated ZnTe are produced by a new mechanism, possibly energetic beam-induced reactions with excited N2 adsorbed on the film surface, and/or transient formation of Zn–N complexes in the energetic ablation plume.