Liquid-phase Laser Ablation Research Articles

Influence of additional external pressure on optical emission intensity in liquid-phase laser ablation

We examined the influence of additional external pressure on the optical emission intensity from plasmas produced by laser ablation of a Ti target immersed in distilled water. We adopted two methods for applying the external pressure. When ambient water was pressurized by connecting the ablation chamber to N 2 gas at a pressure range of 0.1–0.9 MPa, we observed the increase in the optical emission intensity with the pressure. This increase was considered to be caused by the change in the amount of dissolved N 2 gas in the water. On the other hand, when an external pressure of 30 MPa was applied to ambient water by using a mechanical pump, we observed the compression of the spatial distribution of the optical emission intensity. These experimental results suggest a possibility that chemical reactions and physical states (pressure and temperature) of liquid-phase laser-ablation plasmas can be controlled by adding external pressure to ambient liquid.

Preparation of polyynes up to C 22H 2 by liquid-phase laser ablation and their immobilization into SiO 2 gel

Long-chain polyynes up to C 22H 2 were prepared by the liquid-phase laser ablation of a graphite pellet. Short-chain polyynes (C 4H 2, C 6H 2, C 8H 2 and C 10H 2) prepared simultaneously were identified not by UV–Vis spectra but by LC/MS spectra because C 4H 2 and C 6H 2 have absorption peaks at short wavelengths below 200 nm. Polyynes could first be immobilized in a SiO 2 dried gel, which was confirmed by UV–Vis spectra of the gel.

Effects of pulse duration upon the plume formation by the laser ablation of Cu in water

Time-resolved images of an ablation plume obtained at different pulse durations have been measured for the liquid-phase laser ablation of a Cu plate, and the emission intensity and size of the plume have been discussed. In some plume images, high-density bright spots were observed. The size of the light-emitting region increases and the bright spots disappear for the irradiation with a 150-ns pulse. We conclude that consecutive excitation by the later part of a longer pulse expands the plume and reduces plume density. These results are consistent with our previous result that less-broadened atomic line spectra with high emission intensity were obtained with a 150-ns-pulse irradiation.

Diagnostics of liquid-phase laser ablation plasmas by spectroscopic methods

We adopted spectroscopic diagnostics for investigating plasmas produced by laser ablation of a graphite target in water. By taking pictures of optical emissions at various delay times after the irradiation of the ablation laser pulse, we examined the size, the lifetime, and the transient expansion of the plasma. The spectrum of the optical emission was also measured at various delay times. No line emissions were observed in the spectrum. The blackbody temperature of the plasma was evaluated by fitting the continuum spectrum with the Plank equation. In addition, we examined the propagations of compressional waves in water by shadowgraphy.

Direct Growth of Highly Organized Crystalline Carbon Nitride from Liquid-Phase Pulsed Laser Ablation

The novel technique of liquid-phase pulsed laser ablation has been used to obtain unique, highly ordered nanostructures of crystalline carbon nitride (C3N4) via ablation of a graphite target submerged in aqueous ammonia solution. Transmission electron microscopy (TEM) analysis shows that the morphology of the carbon nitride material changes at different length scales, depending upon the synthesis conditions. The initial ablation product comprises spherical nanoparticles of carbon nitride, which then elongate to nanorods (10 nm by ∼200 nm) with further ablation. Given sufficient concentration, the nanorods aggregate to form multilayered structures, and then ultimately larger, ordered “leaf-shaped” structures 30−50 nm by ∼200 nm in size. With even higher concentration, these leaflike structures can themselves aggregate to create interconnected networks of large micrometer scale clusters, which ultimately rearrange to micrometer-sized flowerlike structures. The various nanostructures were characterized using a number of analysis techniques, and their composition was found to be consistent with that of crystalline α- or β-phase carbon nitride. A formation mechanism for these structures is proposed that rationalizes the observed morphologies.

Fabrication of inorganic nanomaterials by pulsed laser ablation in liquid phase

Fabrication of inorganic nanomaterials by pulsed laser ablation in liquid phase