Nanoparticles exhibit distinct physical and chemical properties compared to bulk materials, making them valuable in applications such as electronics, photovoltaics, catalysis, and biomedical sciences.1
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Several methods exist for nanoparticle synthesis, including sol-gel processing, chemical reduction, and vapor-phase deposition. However, many of these techniques rely on chemical precursors, which can introduce impurities and limit scalability.1
Laser ablation provides an alternative approach for producing high-purity nanoparticles with precise control over composition and minimal contamination. Ongoing advancements in laser ablation techniques continue to improve synthesis efficiency, enabling the development of functional nanomaterials with well-defined structures.1
What is Laser Ablation?
Laser ablation is a physical process in which a high-intensity laser beam is directed at a solid target, causing surface atoms to vaporize and form a plasma plume. As the evaporated species cool and nucleate, nanoparticles are generated.
This technique is widely used for synthesizing semiconductor quantum dots, carbon nanotubes, nanowires, and core-shell nanoparticles. Its ability to produce high-purity materials without chemical precursors makes it a valuable method for nanomaterial fabrication.2
The Laser Ablation Process for Nanoparticle Synthesis
Laser ablation begins when a high-intensity laser beam is focused onto the surface of a solid target material, causing rapid localized heating. The absorbed laser energy vaporizes the material, creating a plasma plume composed of atoms, clusters, electrons, and ions.4
As the vaporized material cools, the plasma plume undergoes rapid condensation, leading to nanoparticle nucleation and growth. Nanometer-sized particles form at the edges of the laser plume, where cooling occurs within microseconds. This rapid solidification enables controlled nanoparticle sizes.
The resulting nanoparticles typically have clean surfaces, though they may undergo agglomeration due to coagulation or chemical bonding at contact points, which can influence their properties.3,4
Types of Laser Ablation
Two primary laser ablation techniques are used for nanoparticle synthesis:
Laser Ablation in Liquid (LAL)
In LAL, the target material is submerged in a liquid medium such as water, ethanol, or ammonia solution. When a high-intensity laser beam strikes the target, it generates a plasma plume that is confined by the surrounding liquid. This confinement promotes rapid cooling and condensation, leading to nanoparticle formation.
The liquid medium influences nanoparticle composition. For example, ablation of metals in water produces metal oxide nanoparticles, while ablation in organic solvents can modify surface chemistry.2
Laser Ablation in Vacuum or Gas
In this method, ablation occurs in a low-pressure gas environment or vacuum chamber. When a laser pulse strikes the target, it vaporizes the surface, generating a plume of evaporated species. These species collide and condense, forming nanoparticles.
The choice of background gas, such as argon or helium, affects cooling rates and prevents unwanted chemical reactions. This method enables precise control over nanoparticle size and morphology, and it is particularly useful for producing ultra-pure nanoparticles.3
Parameters Affecting Nanoparticle Synthesis via Laser Ablation
Several factors influence the size, shape, and composition of nanoparticles synthesized through laser ablation.
Laser Parameters
The wavelength, pulse duration, energy density (fluence), and repetition rate of the laser significantly impact nanoparticle formation. Shorter wavelengths (e.g., UV) promote greater fragmentation due to higher photon energy, resulting in smaller nanoparticles, while longer infrared wavelengths penetrate deeper into the target, increasing the ablation rate and producing larger particles.5
Laser fluence must exceed a threshold to initiate ablation. Higher fluence improves nanoparticle yield but may cause excessive fragmentation. The pulse duration also plays a key role—nanosecond pulses primarily induce thermal evaporation, whereas femtosecond pulses produce a direct solid-to-vapor transition, yielding more uniform nanoparticles.6
Target Material
The composition and physical properties of the target material, including hardness, melting point, and light absorption efficiency, directly affect the ablation process. Metals exhibit higher ablation efficiency under visible and UV lasers due to strong interband absorption. Softer materials or those with lower melting points vaporize more easily, whereas materials with high thermal conductivity may require higher laser fluence for effective ablation.7
Medium (Liquid or Gas Environment)
The surrounding medium—whether liquid or gas—affects nanoparticle formation. In LAL, factors such as solvent type, temperature, and pH influence nanoparticle stability and composition. Deionized water is commonly used due to its high heat capacity but can cause oxidation of metal nanoparticles. Organic solvents like ethanol and acetone enhance stability by preventing particle agglomeration due to their strong dipole moments.8
Temperature also plays a role—lower temperatures (e.g., ice water) promote smaller nanoparticles due to faster cooling, while higher temperatures favor particle growth and aggregation. Additionally, pH affects nanoparticle morphology, as acidic or basic conditions influence surface interactions and aggregation behavior.8
Benefits and Challenges of Using Laser Ablation for Nanoparticle Synthesis
Laser ablation provides high precision and control over nanoparticle synthesis, producing ultra-pure nanoparticles without requiring chemical precursors, stabilizers, or surfactants. This makes it particularly suitable for applications in biomedicine, electronics, and catalysis, where material purity is essential.9
For example, a study by Ahmed et al. demonstrated that silver nanoparticles (AgNPs) synthesized via Laser Ablation Synthesis in Solution exhibited superior antimicrobial activity compared to chemically synthesized AgNPs, as they were free from organic contaminants that could reduce bioactivity.10
Another advantage of laser ablation is its clean and environmentally friendly nature. Unlike wet-chemical methods, which rely on toxic solvents or reducing agents, laser ablation generates nanoparticles directly from a solid target in a gas or liquid without producing harmful byproducts.9
Laser ablation is adaptable for both laboratory research and industrial applications, as processing conditions can be optimized with high-energy lasers.9 However, large-scale production remains challenging due to the low nanoparticle yield per unit time. Higher laser power or extended ablation times are required to increase output, leading to higher energy consumption and operational costs.9
Another limitation is particle size uniformity. While laser ablation ensures high purity, plasma plume dynamics can result in size variations, affecting nanoparticle properties. Post-processing techniques such as secondary irradiation or ultracentrifugation are often needed to improve size distribution.9
Additionally, precise synthesis control requires high-energy lasers and complex setups, further increasing costs. While wet-chemical methods offer greater production volumes at lower costs, they often compromise purity, highlighting the challenge of balancing control, purity, and cost in laser ablation. But, despite these challenges, laser ablation remains a valuable tool for producing high-purity nanoparticles.
For more information on various nanoparticle synthesis methods, please visit the following resources:
References and Further Readings
(1) Kim, M.; Osone, S.; Kim, T.; Higashi, H.; Seto, T. (2017). Synthesis of Nanoparticles by Laser Ablation: A Review. KONA Powder Part. J. https://www.jstage.jst.go.jp/article/kona/34/0/34_2017009/_article
(2) Wazeer, A.; Das, A.; Sinha, A.; Karmakar, A. (2023). Nanomaterials Synthesis via Laser Ablation in Liquid: A Review. J. Inst. Eng. Ser. D. https://ui.adsabs.harvard.edu/abs/2023JIEID.104..413W/abstract
(3) Cutroneo, M.; Havranek, V.; Mackova, A.; Malinsky, P.; Silipigni, L.; Slepicka, P.; Fajstavr, D.; Torrisi, L. (2022). Laser Ablation for Material Processing. Radiat. Eff. Defects Solids. https://www.tandfonline.com/doi/abs/10.1080/10420150.2022.2049783
(4) Balachandran, A.; Sreenilayam, S. P.; Madanan, K.; Thomas, S.; Brabazon, D. (2022). Nanoparticle Production via Laser Ablation Synthesis in Solution Method and Printed Electronic Application—A Brief Review. Results Eng. https://www.sciencedirect.com/science/article/pii/S2590123022003164
(5) Naser, H.; Alghoul, M. A.; Hossain, M. K.; Asim, N.; Abdullah, M. F.; Ali, M. S.; Alzubi, F. G.; Amin, N. (2019). The Role of Laser Ablation Technique Parameters in Synthesis of Nanoparticles from Different Target Types. J. Nanoparticle Res. https://pure.kfupm.edu.sa/en/publications/the-role-of-laser-ablation-technique-parameters-in-synthesis-of-n
(6) Reich, S.; Schönfeld, P.; Letzel, A.; Kohsakowski, S.; Olbinado, M.; Gökce, B.; Barcikowski, S.; Plech, A. (2017). Fluence Threshold Behaviour on Ablation and Bubble Formation in Pulsed Laser Ablation in Liquids. ChemPhysChem. https://chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/cphc.201601198
(7) Zhang, D.; Gokce, B.; Barcikowski, S. (2017). Laser Synthesis and Processing of Colloids: Fundamentals and Applications. Chem. Rev. https://pubs.acs.org/doi/10.1021/acs.chemrev.6b00468
(8) Palazzo, G.; Valenza, G.; Dell’Aglio, M.; De Giacomo, A. (2017). On the Stability of Gold Nanoparticles Synthesized by Laser Ablation in Liquids. J. Colloid Interface Sci. https://pubmed.ncbi.nlm.nih.gov/27692858/
(9) Sportelli, M. C.; Izzi, M.; Volpe, A.; Clemente, M.; Picca, R. A.; Ancona, A.; Lugarà, P. M.; Palazzo, G.; Cioffi, N. (2018). The Pros and Cons of the Use of Laser Ablation Synthesis for the Production of Silver Nano-Antimicrobials. Antibiotics. https://pmc.ncbi.nlm.nih.gov/articles/PMC6164857/
(10) Ahmed, K. B. R.; Nagy, A. M.; Brown, R. P.; Zhang, Q.; Malghan, S. G.; Goering, P. L. (2017). Silver Nanoparticles: Significance of Physicochemical Properties and Assay Interference on the Interpretation of in Vitro Cytotoxicity Studies. Toxicol. Vitr. https://pubmed.ncbi.nlm.nih.gov/27816503/
