Laser Ablation in Flowing Liquid

Abstract

Pulsed laser ablation (PLA) is a unique method used to obtainatoms, ions, and small molecules from solid targets because ofits high-energy output, the ability to adjust the power of thelaser, and the purity of the final product.1,2 Most experiments onpulsed laser-solid interaction have been carried out in vacuum(10−4 Pa)3 or in a low pressure background gas,4 aiming at thin film fabrication and cluster formation.1 One of the advantages ofthe PLA method is that stoichiometric thin films can be preparedwith the same composition as the target materials. In addition,metals, semiconductors, and ceramics with high melting point canbe obtained at lower temperatures. However, this method has somedisadvantages, such as the size of the granules on the surface ofthin films is not even, big particles exist in the surface, and ahigh vacuum environment raises the preparation cost. Also, it isdifficult to obtain a thin film with big area using the PLA method.Some researchers have attempted to produce new materials by PLAin a static liquid medium. Figure 11.1 shows a typical schematicdiagram of the experimental apparatus of PLA in static liquid.5Mafune´ and coworkers prepared small silver, gold, and platinumclusters by laser ablation of ametal plate in the aqueous solution of asurfactant, where the clusters are encapsulated by the surfactant. Atthe same time, they also researched the influence of the preparationconditions, such as the concentration of the surfactant and thepower of laser ablation, on the stability of the nanoparticles in thesolution.5−8 Yang and coworkers prepared nanocrystalline diamond and cubic C3N4 by laser ablation of a graphite target in acetonesolution and ammonia solution, respectively.9,10,11 Iwabuchi et al.12prepared nanosized titania particles by PLA of a rutile single-crystaltarget in water. Compagnini et al.13 reported PLA of gold andsilver in several liquids (mainly water, ethanol, and chloroform).They observed the formation of metal sols by laser ablation inwater and ethanol and the formation of chloride compound solsby laser ablation in chloroform. This revealed that the chemicalstate of the formed nanoparticles depends mainly on the chemicalreactivity of the liquid. Liang et al.14 synthesized ultrafine SnO2−x nanocrystals by PLA of a tin metal plate in aqueous solutions ofsodium dodecyl sulfate and in pure water. Yeh and coworkers15also prepared aluminum hydroxides by laser ablation of an Al rodimmersed in water solvent. During aging, bayerite, gibbsite, andboehmite particles were formed simultaneously.