چكيده به لاتين
Metal and metal-based nanoparticles (NPs) e.g. metal oxides and hydroxides are being increasingly used for optoelectronic devices as well as catalysts, sensors, storage, and medical fields due to excellent biocompatibility, unique electronic, optical and mechanical properties. In recent years, production of such NPs by using Pulsed Laser Ablation in Liquids (PLAL) have been particularly interested because of their ease of synthesis, antimicrobial activity, high electrical conductivity as well as size, shape and surface modifications. To utilize PLAL in fabricating NPs efficiently, it is essentially important to understand the fundamental aspects of PLAL. This issue important as the process including the production efficiency of NPs and their characteristics (such as precise size control) can be controlled by changing the experimental parameters.
In this thesis, our goal is to analyses the effect of External Electric Field (EEF) on characteristics of nanoparticles and ablation rate. For this purpose, the colloidal Al-based NPs in deionized water and ethanol and Cu-based NPs in deionized water have been prepared by the nanosecond pulsed laser ablation processes under two different conditions, with and without the electric field. The effect of electric field strength on the material removal rate, the nanoparticles characteristics and its mechanisms were investigated both in the electric field parallel and perpendicular to the laser beam path schemes. In another part of this study, the effect of external electric field and laser fluence on ablation rate were investigated. Our results indicate that for both aluminum and copper targets, regardless of the type of the electric field scheme, the average size of the NPs decreases with increasing the electric field strength. However, the interaction of laser beam with metal targets (in perpendicular condition) leads to formation of smaller size NPs than those in parallel condition. Moreover, the UV–Vis spectra show that the nanoparticles production efficiency increases with increasing the electric field strength. The XRD patterns show that the structure of produced NPs with and without presence of electric field is Boehmite (AlOOH). In addition, under an applied electric field, synthesized NPs with Boehmite crystal (grown along a specific direction) are formed. According to the results, it can be concluded that the ablation rate enhanced by applying electric field and increasing laser pulse energy. The results explain that more efficient laser energy absorption on the target may occur in PLAL with an external electric field due to the effects of the external electric field on the population of seed electrons on the target surface (in parallel condition) and the dynamic of charged-particle in the plasma plume (in both parallel and perpendicular conditions).
