Pulsed Laser Ablation In Liquid Process Research Articles

Synthesis of low dimensional nanomaterials by pulsed laser ablation in liquid

With the increasing application of functional nanomaterials in numerous fields, considerable effort has been devoted to exploring simple and efficient methods for their synthesis. Pulsed laser ablation in liquid (PLAL) is one such novel technique for producing colloidal nanomaterials. It is simple to setup, easy to operate, and can be carried out at room temperature and under atmosphere. This method employs a pulsed laser beam to ablate bulk targets or powders within different liquids, thereby creating colloidal nanomaterials. As a result, it holds significant promise for scalable processing. However, most prior research on PLAL has focused on the synthesis of larger spherical nanoparticles, even though low-dimensional nanomaterials, including zero-dimensional quantum dots, one-dimensional nanowires and nanotubes, and two-dimensional nanosheets and nanobelts, find more usage in various applications, such as optoelectronic devices, catalysis, and biomedicine. In the PLAL process, the high-intensity laser pulses not only fragment the illuminated solids to produce nanomaterials but also interact with liquid molecules, generating multiple reactive ions for chemical reactions. Consequently, various low-dimensional nanomaterials can also be generated. This study provides a comprehensive review of low-dimensional nanomaterials synthesized via PLAL, including their formation mechanisms and applications.

Unique production strategy of Pt/C electrocatalysts via pulsed laser for hydrogen generation: Insights screening by DFT calculations

Design and optimizing the components and structure of highly-active electrocatalysts is a prevalent approach for reducing the input electrical energy consumption and concurrently H2 fuel production. An efficient and sustainable method is a water-electrolyzer for H2 generation, but still restricted by the stable electrode materials. In this study, a green chemistry approach for one-pot production of Pt/C nanospherical with controllable ratios of Pt and C was demonstrated using simple pulsed laser ablation in liquid (PLAL) process, during which Pt target ablation in diverse solvents (water, methanol, ethanol, and 1-propanol) without external carbon source and reducing/capping agents. The carbon-rich solvents are acted as both C-source and solvent, which are decomposed during the PLAL process, producing C, H, and OH ions inside the cavitation bubble which condenses as C-shells on the Pt surface. The optimal Pt/C proportions have the highest electrochemical H2-evolution in acidic media with an overpotential of 59 mV at 10 mA/cm2, Tafel slope of 41 mV/dec, and j0 of 0.686 mA/cm2. The exceptional electrocatalytic concert of optimal Pt/C was further supported by the density functional theory. Optimized C-content in Pt/C reveals good dispersion and strong interaction of C with Pt can make efficient electron transfer, structural stability, and electrochemical durability, resulting in superior electrocatalytic performance in electrolyzer devices.

Post-fabrication adjustment of metalloid Mg–C-graphene nanoparticles via Pulsed Laser Ablation for paper electronics and process optimisation

Metalloid nanoparticles (MNPs) possess unique physicochemical properties but are challenging to create through biological or chemical routes. Using Pulsed Laser Ablation in Liquid (PLAL), Mg–C MNPs are fabricated from powders. The produced nanocolloids were ablated after the target was removed to tailor the particle size. MNPs with a mean size 300 nm could be reduced to 60 nm. Alternatively, MNPs with a mean size of 60 nm could be increased to 90 nm. The increase/decrease in size is controlled by the laser processing parameters and showcases the ability of PLAL for real-world applications that require meticulous control of size. The as-fabricated nanocolloids were successfully inkjet printed on paper, achieving a low resistivity of 75 Ω/square after 60 prints, highlighting their potential in printed electronics. To address a historical research gap, this article explored the impact of PLAL processing parameters, including fluence (1–2 J/cm2), pulse width (0.2–0.9 ns), repetition rate (10–20 kHz), and pH, factors often overlooked which is partly limiting applications. The influence of powder vs rod target on the PLAL process was addressed revealing that powders produce better size control and are easier to handle but they produce lower colloid concentrations.

Optical Diagnostics during Pulsed Laser Ablation in Liquid (PLAL) for the Production of Metallic Nanoparticles

Pulsed laser ablation in liquid (PLAL) is gaining an important role as a methodology for producing nanostructures without the use of chemicals and stabilizers. Several nanomaterials have been produced and the engineering of PLAL is becoming an important task for the dissemination of this approach for nanostructure production. Monitoring the processes involved in the PLAL during nanostructure production can be extremely useful for improving the experimental methods and for pushing PLAL to new material formation. In this paper, we discuss the use of optical techniques for investigating the specific stages involved in the production of nanomaterials with PLAL. In particular, the recent advancements of these optical techniques for each specific stage of the PLAL process will be discussed: optical emission spectroscopy and imaging for the investigation of the plasma phase, shadowgraph imaging for the investigation of the cavitation bubble dynamics and different scattering techniques for the visualization of the produced nanostructure.

Anomalously enhanced thermal conductivity of graphite-oxide nanofluids synthesized via liquid-phase pulsed laser ablation

Graphite-oxide (GO) nanofluids with enhanced thermal conductivity are successfully prepared using pulsed laser ablation in liquid (PLAL) of a graphite target in deionized water. The effects of laser frequencies are investigated on the variations of GO nanoparticles. The morphology, structure and composition of the nanoparticles are characterized using various spectroscopic techniques. During the PLAL process, graphite is oxidized to GO which is inherently hydrophilic, no surfactant is required in the preparation of nanofluid. The laser frequency significantly affects the size and morphology of the GO nanoparticles during laser ablation, leading to a profound variation in the thermophysical properties of the GO nanofluids. At the laser frequency of 10 Hz, the maximum thermal conductivity enhancement of 82% is achieved at a temperature of 50 °C while the maximum viscosity increment is recorded at a temperature of 30 °C. This study shows the great potential of the PLAL method in synthesizing GO nanofluid with anomalously enhanced thermal conductivity.

One-step synthesis of sulfur-incorporated graphene quantum dots using pulsed laser ablation for enhancing optical properties.

To tune the electronic and optoelectronic properties of graphene quantum dots (GQDs), heteroatom doping (e.g., nitrogen (N), boron (B), and sulfur (S)) is an effective method. However, it is difficult to incorporate S into the carbon framework of GQDs because the atomic size of S is much larger than that of C atoms, compared to N and B. In this study, we report a simple and one-step method for the synthesis of sulfur-doped GQDs (S-GQDs) via the pulsed laser ablation in liquid (PLAL) process. The as-prepared S-GQDs exhibited enhanced fluorescence quantum yields (0.8% → 3.89%) with a huge improved absorption band in ultraviolet (UV) region (200 ∼ 400 nm) and excellent photo stability under the UV radiation at 360 nm. In addition, XPS results revealed that the PLAL process can effectively facilitate the incorporation of S into the carbon framework compared to those produced by the chemical exfoliation method (e.g., hydrothermal method). And also, the mechanisms related with the optical properties of S-GQDs was investigated by time-resolved photoluminescence (TRPL) spectroscopy. We believe that the PLAL process proposed in this study will serve as a simple and one-step route for designing S-GQDs and opens up to opportunities for their potential applications.

Pulsed laser ablation based synthetic route for nitrogen-doped graphene quantum dots using graphite flakes

Graphene quantum dots (GQDs) prepared by pulsed laser ablation in liquid (PLAL) process face barriers to commercialization due to their poor optical properties and the use of expensive carbon precursors. In this work, we report a one-step route for the preparation of N-doped graphene quantum dots (NGQDs) with excellent optical properties using a low-cost carbon precursor. The as-prepared NGQDs exhibited excellent optical properties and high quantum yield compared to pristine graphene quantum dots (0.8% → 9.1%) due to the presence of the N atoms. A possible recombination mechanism of NGQDs was investigated by time-resolved photoluminescence spectroscopy. The increase of N atoms incorporated in the GQDs resulted in an increased fraction of the short recombination lifetime from the intrinsic state. We also report a possible mechanism for the formation of the N atoms in the GQDs structure during the PLAL process, which is explained based on the plasma plume, cavitation collapse, and nitrogen precursor decomposition model.

Investigation on the material in the plasma phase by high temporally and spectrally resolved emission imaging during pulsed laser ablation in liquid (PLAL) for NPs production and consequent considerations on NPs formation

In this paper experimental temperature and density maps of the laser induced plasma in water during pulsed laser ablation in liquid (PLAL) for the production of metallic nanoparticles (NPs) has been determined. A detection system based on the simultaneous acquisition of two emission images at 515 and 410 nm has been constructed and the obtained images have been processed simultaneously by imaging software. The results of the data analysis show a variation of the temperature between 4000 and 7000 K over the plasma volume. Moreover, by the study of the temperature distribution and of the number densities along the plasma expansion axis it is possible to observe the condensation zone of the plasma where NPs can be formed. Finally, the time associated with the electron processes is estimated and the plasma charging effect on NPs is demonstrated. The set of observations retrieved from these experiments suggests the importance of the plasma phase for the growth of NPs and the necessity of considering the spatial distribution of plasma parameters for the understanding of one of the most important issues of the PLAL process, that is the source of solid material in the plasma phase.

Liquid media regulated growth of cinnamon nanoparticles: Absorption and emission traits

Customized cinnamon-based nanostructures are of great demand for broad arrays of nanomedical, biomedical and photocatalytic purposes. Conventional methods for cinnamon nanomaterials production with desirable optical absorption and emission properties are still limited. This communication elucidates the role of growth media (liquid ethanol and methanol) in controlling the optical qualities of cinnamon nanoparticles (CNPs). Such CNPs of varied morphologies were prepared using pulsed laser ablation in liquid (PLAL) technique (a simple, an inexpensive, and an eco-friendly approach). In the PLAL process, clean cinnamon sticks (as target material purchased from supermarket) were ablated via Q-switched Nd:YAG laser pulse of wavelength 532 nm operated at optimum fluence of 5.73 J/cm2. As-synthesized CNPs were characterized at room temperature using ultraviolet-visible (UV-Vis) absorption and photoluminescence (PL) emission spectroscopy. Uniformly dispersed high purity colloidal CNPs with narrow size distribution was achieved. The UV-Vis absorption and the PL spectra of CNPs revealed prominent peaks. These observed distinctive absorption and emission traits of studied CNPs were ascribed to the effects of oxygen deficiency, quantum confinement, crystal defects and existence of cinnamaldehyde compounds. In short, the nucleation and growth of CNPs was significantly sensitive to the chemical character of liquid suspension that provided a favorable thermodynamic condition via entropy driven free energy minimization. It was demonstrated that the structural, morphological, physical, optical properties of such CNPs can be tailored by intuitively selecting the liquid growth media. This disclosure affirmed that the present systematic approach can constitute a basis for the large-scale production of CNPs effective for widespread applications.

Pulsed laser ablation of wire-shaped target in a thin water jet: effects of plasma features and bubble dynamics on the PLAL process

In this paper, emission spectroscopy and fast imaging surveys during pulsed laser ablation in liquid (PLAL) for nanoparticles (NPs) production have been used, in order to provide further details about the process involved and the potentialities offered by a wire-shaped sample ablated in a flowing water jet. This kind of set-up has been explored because the laser ablation efficiency in water increases when a thin water layer and a wire-shaped target are used. In order to understand the physical processes causing the increasing ablation efficiency, both the laser-induced plasma and bubble dynamics generated in a flowing liquid jet have been analysed. The plasma parameters and the bubble behaviour in such a system have been compared with those observed in conventional PLAL experiments, where either a bulk or a wire-shaped target is immersed in bulk water. From the data presented here it is evidenced that the plasma and shockwave induced during the breakdown process can play a direct role in the ablation efficiency variation observed. With regard to the cavitation bubbles evolving near a free surface (the interface between water and air) it should be noted that these have to be treated with caution as a consequence of the strong influence played in these circumstances by the boundary of the water jet during its expansion dynamics. The effects due to the size of the liquid layer, the presence of the water/air interface, the liquid characteristics, the target shape, the plasma evolution and the bubble dynamics together with their outcomes on the NPs’ production, are presented and discussed.