Fast and massive synthesis of silver nanoparticle by a liquid-flow plasma source using AgNO₃solution

Plasma-liquid interaction has attracted much attention for various applications such as water purification, decomposition of liquid waste, biotechnology, agriculture, and material synthesis. However, there are many problems in applying the plasma treatment to industrial applications. First, many applications require treating large volumes of liquid, but the processing capacity of most plasma treatment systems is not adequate for the application. Furthermore, many liquids are difficult to ignite with plasma due to the electro conductivity of the liquids, the high electro negativity and the internal energy of the water molecules.

To solve these problems, we have developed a plasma source for liquid treatment in which a ring-shaped microwave plasma is sustained in a reduced pressure region by liquid flow from a nozzle. The pressure drop at the discharge is realized by the flow itself using the Venturi effect. Thus, a steady discharge can be generated, and throughput can be efficiently increased through fluid processing rather than batch processing. In this study, as an application of this device to material synthesis, synthesis of silver nanoparticles is demonstrated using 15 L of 0.1 mol/L silver nitrate solution. The yields and shapes of the generated nanoparticles are evaluated.