Mechanism study of nanomaterial synthesis by pulsed laser ablation in liquid

摘要

With the development of nanotechnology, nanomaterial have been widely used in many fields, such as medical technology, catalysis, and biotechnology. Among the methods of nanomaterial fabrication, pulsed laser ablation in liquids (LAL) has attracted great attention as a green and versatile approach to fabricate manifold nanomaterial with ligand-free surface. LAL physical process and mechanism is complicated. Firstly laser focus on the target material through the liquid layer, and the surface material is exfoliated. Then the plasma is generated and expands, accompanying the plasma shock wave. Afterwards, the plasma quenches and releases energy into the surrounding liquid. Finally cavitation bubble appears and collapses. These complex mechanisms affect the properties of the prepared nanomaterial, including shape, size, structure, photoelectric properties, etc. Here, we investigate physical process and mechanism of nanomaterial prepared by LAL in detail using high-speed camera experimental system and CFD (Computational Fluid Dynamics) simulation mode. According to the analysis of LAL mechanism, it is reasonable to assume that laser-induced bubble can act as an ideal reactor for nanomaterial synthesis. The movement of the nanoparticles depends on the bubble oscillation. They move outward when the bubble expands and move inward when the bubble shrinks. It shows that the velocity, pressure and the temperature are high at the beginning of expansion and the collapse moment of the bubble, which is quiet benefited for the nanomaterial synthesis.