Laser ablation has emerged as a versatile and scalable technique for producing nanoparticles of two-dimensional materials, including graphene, transition metal dichalcogenides (TMDCs), and MXenes. This method involves irradiating a bulk target material with a high-energy laser pulse in a liquid or gaseous medium, leading to the ejection of atoms and clusters that subsequently form nanoparticles. The process is particularly advantageous for 2D materials due to its ability to exfoliate layers while minimizing defects and contamination. However, achieving precise control over layer number, lateral dimensions, and crystallinity remains a significant challenge.

The laser ablation process begins with the selection of an appropriate target material. For graphene, highly ordered pyrolytic graphite (HOPG) is commonly used, while bulk crystals of MoS2 or WS2 serve as precursors for TMDCs. MXenes, typically synthesized from MAX phases, require careful handling due to their sensitivity to oxidation. The target is immersed in a liquid medium, which plays a critical role in stabilizing the ablated particles and preventing aggregation. Common solvents include water, ethanol, isopropanol, and N-methyl-2-pyrrolidone (NMP), each influencing the final nanoparticle properties. Water, for instance, may introduce oxygen-containing functional groups on graphene, while organic solvents like NMP can enhance dispersion stability.

Laser parameters must be optimized to achieve desired nanoparticle characteristics. Pulse duration, wavelength, energy fluence, and repetition rate directly influence the ablation efficiency and particle size distribution. Nanosecond lasers with wavelengths in the ultraviolet (UV) or visible spectrum are frequently employed due to their strong absorption by most 2D materials. For example, a Nd:YAG laser operating at 532 nm with a fluence of 0.5–1.0 J/cm² has been shown to produce monolayer or few-layer graphene nanoparticles with lateral sizes below 100 nm. Femtosecond lasers, though less common, offer reduced thermal effects, potentially preserving the crystallinity of TMDCs and MXenes.

Controlling the layer number and lateral dimensions of 2D material nanoparticles is a persistent challenge. The layer number depends on the laser energy and the interlayer bonding strength of the material. Graphene, with its weak van der Waals forces, is more easily exfoliated into few-layer sheets compared to TMDCs, which exhibit stronger interlayer interactions. MXenes, with their unique surface terminations, require careful tuning of laser parameters to avoid excessive fragmentation. Lateral dimensions are influenced by the laser fluence and the solvent’s viscosity. Higher fluence tends to produce smaller particles, while viscous solvents can limit particle agglomeration but may also reduce ablation yield.

Liquid medium selection is critical for stabilizing the ablated nanoparticles. Polar solvents like water are effective for hydrophilic materials such as MXenes, but they may introduce defects or oxidation. Nonpolar solvents like toluene or chloroform are better suited for hydrophobic materials like graphene but often require surfactants to prevent aggregation. Mixed solvent systems, such as water-ethanol blends, can offer a balance between dispersion stability and defect minimization. The pH of the medium also plays a role, particularly for MXenes, where acidic conditions can prevent oxidation but may alter surface chemistry.

Characterization of 2D material nanoparticles requires specialized techniques to assess layer number, size distribution, and structural integrity. Raman spectroscopy is widely used for graphene and TMDCs, with the G and 2D peaks providing information on layer thickness and defects. For MXenes, shifts in the characteristic Raman modes indicate surface functionalization or oxidation. Transmission electron microscopy (TEM) is indispensable for direct visualization of lateral dimensions and layer stacking, while atomic force microscopy (AFM) provides precise height measurements to confirm monolayer or few-layer structures. X-ray photoelectron spectroscopy (XPS) reveals surface chemistry and oxidation states, particularly important for MXenes. Dynamic light scattering (DLS) offers a rapid assessment of particle size distribution in colloidal suspensions.

Applications of 2D material nanoparticles leverage their unique properties compared to bulk forms. In energy storage, graphene nanoparticles enhance the performance of supercapacitors due to their high surface area and conductivity. MXene nanoparticles, with their tunable surface chemistry, are promising for lithium-ion battery anodes. TMDC nanoparticles exhibit exceptional catalytic activity for hydrogen evolution reactions, benefiting from edge-rich sites and quantum confinement effects. In biomedical applications, graphene oxide nanoparticles serve as efficient drug carriers, while TMDC nanoparticles are explored for photothermal therapy due to their strong near-infrared absorption. Environmental applications include photocatalytic degradation of pollutants using TiO2-graphene hybrid nanoparticles, where the small size and high surface area improve reaction kinetics.

The advantages of 2D material nanoparticles over bulk forms are evident in their enhanced surface-to-volume ratio, edge effects, and quantum confinement. These properties lead to improved catalytic activity, optical response, and mechanical strength. However, challenges remain in scaling up production while maintaining consistency in layer number and size. Post-processing steps such as centrifugation or filtration are often required to isolate specific fractions, adding complexity to the synthesis workflow.

Future developments in laser ablation for 2D material nanoparticles will likely focus on improving control over layer number and lateral dimensions through advanced laser systems and solvent engineering. In situ monitoring techniques, such as time-resolved spectroscopy, could provide real-time feedback for process optimization. The integration of machine learning for parameter prediction may further enhance reproducibility and yield. As the demand for high-performance nanomaterials grows, laser ablation stands as a promising method for producing 2D material nanoparticles with tailored properties for diverse applications.

The continued refinement of this technique will depend on interdisciplinary efforts combining materials science, laser physics, and colloidal chemistry. By addressing the challenges of layer control, size distribution, and solvent interactions, laser ablation can unlock the full potential of 2D material nanoparticles in technologies ranging from energy storage to biomedicine.