Microwave-Induced Plasma-In-Liquid Process for Nanoparticle Production

In the past decades, various nanomaterials have been intensively developed because of their unique electrical, optical, magnetic as well as catalytic properties. In this review, we discuss the plasma-in-liquid process, especially the microwave-induced plasma-in-liquid process (MWPLP), for metal and metal oxide nanoparticle production. Various types of plasma systems have been employed to produce metal, alloy, and metal oxide nanoparticles. Nanoparticle production by plasma processes usually requires fewer chemical additives compared to other chemical processes. After discussing the bottom-up approach and the plasma-in-liquid process for nanoparticle synthesis, we have focused on MWPLP. Various apparatus systems and detailed mechanisms of MWPLP will be discussed and preparation of metal and metal oxide nanoparticles by MWPLP will be introduced in detail. The surface-coated-electrode system, which is a unique system for MWPLP, is also discussed in this review. This system prevents sample contamination due to the metal components, which are usually ejected into the surrounding liquid after plasma ignition during the production of nanoparticles.