Generation of a direct-current, atmospheric-pressure microplasma at the surface of a liquid water microjet for continuous plasma-liquid processing Available to Purchase

Plasmas at the surface of or inside liquids are of importance for emerging applications, and are often formed with stagnant liquids. Here, the authors present the generation of a direct-current, atmospheric-pressure microplasma at the surface of a liquid water microjet that enables solution species to be transported by forced convection. The water jet is formed by pumping conductive ionic solutions through a plastic capillary tube in a vertically falling geometry, and overcomes Plateau–Rayleigh instabilities by controlling the flow rate, resulting in a constant diameter jet of ∼0.45 mm over lengths of more than 30 mm. Analysis of the electrical characteristics of the complete microplasma-water jet system shows that the current–voltage (I-V) relationship is linear with a large positive slope when the solution conductivity is relatively low. The authors show that the primary contribution to this large resistance is the confined solution geometry. As proof-of-concept, the authors demonstrate that plasmonic Ag nanoparticles can be continuously produced at steady state from solutions of silver nitrate, opening up the possibility of scaled-up production of materials by plasma-liquid processes.