Colloidal nanoparticles: mechanisms of laser synthesis and interactions
Résumé
Laser ablation in liquids is now commonly used to produce colloidal nanoparticles (NPs) that have found numerous applications in different areas. In the experiments, NPs of different materials can be rather easily produced by using laser systems with various pulse durations, shape, wavelengths, and fluence. Here, we focus our attention on metal nanoparticles produced by ultra-short laser pulses.
These nanoparticles have found many applications in various areas as bio-sensing, bio-medicine, catalysis, optics and photonics, new energy sources, cosmetics, etc.
First, we present the modeling of ultra-short laser interactions with metal target in the presence of an ambient liquid. In the model, we vary the delay between laser pulses and laser fluence. As a result of laser interactions, not only NPs, but also bubbles can be formed. Both small bubbles around NPs and one large cavitation bubble near the laser irradiated spot are typically observed above a certain threshold fluence. Local field enhancement and water ionization also affect these processes. Second, lasers provide unique possibilities also for a control over NP sizes. Depending on the experimental conditions, laser interactions with colloidal nanoparticles can either promote nanoparticle growth or induce their fragmentation.
To better understand these processes, we numerically examine laser interactions with nanoparticles in the presence of a liquid environment. The effects of laser wavelength and pulse duration, liquid environment, as well as of nanoparticle material, initial particle sizes and concentration are underlined based on the proposed combined modeling.
References:
1. T. E. Itina, Modeling nanoparticle formation by laser ablation and by spark discharges, LASE 2016, SPIE Photonics West, February 13-18, San Francisco, CA, USA, Invited talk (2016)
2. A. Kucherik, T. E. Itina, Laser ablative nanostructuring of Au in liquid ambience in continuous wave illumination regime, LASE 2016, SPIE Conference Proceedings (2016)