Synthesis of nanoparticles of silver and platinum by microwave-induced plasma in liquid

We have conducted a basic study of microwave plasma in liquid at atmospheric pressure. Plasma could be successfully induced by radiated microwave from pointed and ring tungsten electrodes. The tungsten electrode showed a long lifetime of 70 h. Melting and chemical etching of the electrode's top limited the lifetime. Silver cations from silver nitrates could be rapidly and completely reduced to generate metallic silver nanoparticles using this plasma source without any addition of reducing chemical reagents. Optimization of electric conductivity of the reaction solution was not needed. When the material of the electrode was changed to platinum from tungsten, platinum nanoparticles were produced by vaporization into pure water. Both these preparation processes can be expected to produce lower contamination than chemical synthesis. ► We have conducted a basic study of microwave plasma in liquid at 1 atm pressure. ► Silver cations could be reduced to generate metallic silver nanoparticles. ► When the electrode was platinum, platinum nanoparticles were produced.