Laser-induced plasmas in liquids for nanoparticle synthesis

Abstract

Spatially and temporally resolved emission spectroscopy is used to study the major features of the onset and evolution of plasmas created by pulsed laser irradiation of targets immersed in liquids. It is shown that double pulse operation provides an enhanced rate of nanoparticle formation and increases the emission signal from the plasma atoms and ions owing to more efficient ablation of the target material. The main parameters (density of atoms, electron temperature and density) of laser-induced plasmas in liquids are estimated. The prospects of laser ablation in liquids as a method for producing nanoparticles are analyzed.Keywords: laser-induced plasmas in liquids, double pulse ablation, electron density and temperature, spatially and temporally resolved emission spectroscopy.Introduction. In recent years there has been increased interest in the production and study of nanostructured materials. The structural elements of these materials have characteristic sizes in the range of 1-100 nm so they can have unique electronic, magnetic, and chemical properties which differ from those of the corresponding bulk materials. For example, nanostructured materials can have enhanced mechanical characteristics (hardness, durability), catalytic activity, or luminescence properties, which are absent or less marked in their macroscopic analogs. Thus, nanostructures offer great promise for heterogeneous catalysis and micro-and optoelectronics, and can be used as gas sensors in medicine, biology, and other areas [1][2][3].It should be noted that different methods of nanoparticle synthesis are used, depending on their size, shape, and chemical composition : physical methods based on vapor condensation [4], chemical methods using reduction reactions of metallic ions from solutions of their salts [5], and combined methods [6]. In a number of cases, nanoparticles are obtained in the form of colloidal solutions, which are most often produced by various chemical methods. The main deficiency of these methods is that, besides the nanoparticles, these solutions contain ions and other reaction byproducts which are often difficult to avoid. An alternative method of obtaining nanoparticles that is free of these deficiencies is laser ablation of solids in liquids [7-10].One of the advantages of the laser ablation technique is its universality -the possibility of using it for metals and alloys, semiconductors and dielectrics with different compositions, fairly extensive control of the properties of the synthesized particles by changing the parameters of the laser radiation, and the production of composite particles by ablation of multicomponent targets.Laser ablation of solids can take place in a gaseous atmosphere or in a liquid. In the latter case there is no need use costly vacuum systems and the problem of collecting the nanoparticles is comparatively simple, compared to the difficulties of doing so in gaseous atmospheres. With ablation in a liquid the nanoparticles remain in the volume of the liquid and form a colloidal solution.Although ...

Preparation of PtAu Alloy Colloids by Laser Ablation in Solution and Their Characterization

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Collinear double pulse laser ablation in water for the production of silver nanoparticles

“…9 In orthogonal configuration DP-LAL, the two laser beams are sent with an angle of 901 between each other so that the first pulse ablates the target, while the second pulse, opportunely delayed, irradiates the ejected material. In spite of its promising preliminary results, especially for what concerns the production yield, 10 DP-LAL in collinear configuration for production of NPs has been poorly investigated, and a deeper insight into the fundamental aspects of this technique is needed to improve the LAL process. In this frame, it can be beneficial to underline here what are the differences between collinear DP-LAL and high repetition rate ablation (in the kHz regime).…”

Picosecond laser induced fragmentation of coarse Cu2O particles into nanoparticles in liquid media

“…This is due to the difference in physical, optical and chemical properties of ethanol and water [14,15]. Based on the above presented morphological and crystallinity data of the fragmented Cu 2 O particles and the available literature about the fragmentation mechanism of semiconducting particles [16][17][18][19][20], the following fragmentation mechanism for Cu 2 O is proposed.…”