Nanomaterials: Laser‐Based Processing in Liquid Media

Femtosecond laser‐produced optical absorbers for solar‐thermal energy harvesting

“…Direct treatment of surfaces to alter their optical, morphological, wetting, and compositional properties, 44–46 generation and modification of nanoparticles, 47–51 selective thinning of 2D materials, 52 and doping of semiconductors 53 are only few applications of pulsed lasers in materials processing. The quality of surface structures produced, the chemical composition, and processing mechanisms depend on the laser type (wavelength, pulse duration, pulse energy, and repetition rate), characteristic of the target material (thermal properties and absorption coefficient), and ambient conditions (pressure, liquid/gas, and reactive/nonreactive) 51,54 . Laser ablation of the material starts from the absorption of laser photon energy followed by heating and photoionization of the irradiated area of the target surface.…”

“…Laser ablation of the material starts from the absorption of laser photon energy followed by heating and photoionization of the irradiated area of the target surface. As a result, the ablated material is removed from the target surface as vapor, plasma plume, liquid droplets, or solid fragment 51 . The amount and the phase of the ablated material depend on the maximum temperature the target surface can reach as a result of laser irradiation.…”

“…As a result, femtosecond lasers can precisely remove materials from the target surface and produces much smoother grooves and edges over longer wavelength lasers. Details mechanism of nanosecond and femtosecond laser ablation and effects of different laser parameters on the rate of material processing are presented in references 51,55 .…”

“…The number of scans on the same line, 60 electric field orientation, 62,63 and ambient environment 64 are other control parameters to control the size and density of nanoparticles, the orientation of nanostructures, 65 and chemical composition. For example, different gas ambient or liquid media can be chosen to change the chemical composition of the laser‐processed surfaces 51,66 …”

“…The plasma plume, spatially confined near the target surface, can etch the target material more efficiently. Laser ablation in liquid media has several advantages over ablation in the air or gas phase including comparatively higher spatial confinement of the plasma plume, higher rate of overall ablation, formation of metastable phases, negligible amount of redeposition of particles on the surface, and easier collection of nanoparticles in the solution 45,49,51,82,83 . Recently, Garcell et al processed several copper absorbers in both water and air and studied their surface morphology and optical properties 84 .…”